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Mass production and interchangeable parts

by Tom Gaylord
Writing as B.B. Pelletier

The history of airguns

This report covers:

    • But wait, there’s more
    • Final finishing
    • A gun maker who could not make a gun
    • Airguns?
    • Specialized parts can hurt you
    • Tooling, technology and schedules
    • It’s not as easy as it sounds

If you think interchangeable parts came from Eli Whitney, the way the U.S. history books tell us, you are mistaken. He did perform a demonstration in 1801, assembling one of his muskets from a seemingly random pile of parts — something that had never been done before. He did it, but he cheated. The parts in the pile were marked beforehand to assure they all went together. So — the idea of interchangeable parts may have come from Whitney, but the first practical application of the idea on a mass scale came 50 years later when Samuel Colt created the modern production line. He may have been inspired by Frenchman, Honore LeBlanc, who suggested that firearms ought to be made from standardized parts, but never went beyond the talking stage. Colt invented the production line that required complete interchangeability of parts to succeed.

French 1822 pistol

This French model 1822 percussion pistol was made in 1826. Although there are hundreds of 1822 pistols that look just like it, their parts do not interchange. The parts of each pistol are fitted by hand.

But wait, there’s more

In fact there is a whole lot more. In the early 1800s when Whitney was active, people talked about “good steel.” In the 1850s when Colt started producing hundreds of thousands of identical items that were comprised of millions of parts, they had to have a more refined knowledge of the metallurgy involved. “Good steel” wasn’t enough to keep the factories running. Before too many more years passed the steel alloys became standardized to the point that engineers could rely on repeatable performance from parts that were made to a specification. Engineering handbooks were written. Schools were able to teach new engineers how to calculate the performance of an item before it was made, and that knowledge rippled over into manufacturing. By the end of the 19th century, the production world had a good handle on interchangeable parts. Or did they?

Final finishing

The term final finishing is the enemy of controlled costs. Once an item has been made it still may require more work before it achieves the final goal. People who have never worked in production jobs imagine that finished parts roll off the line, one after another, ready to be used. For some parts there can be a whole list of additional steps that are needed before they are ready for the market. And, would you believe that some things simply cannot be made at all?

A gun maker who could not make a gun

As recently as World War II there was a firearms manufacturer who was unable to produce a single gun for the U.S. military that could meet specifications. The manufacturer was Irwin Pederson — the same gun maker who in World War I designed a way to turn a 1903 Springfield bolt action rifle into a semiautomatic assault rifle 20 years before Hitler’s engineers delevoped the Sturmgewehr.

The top-secret Pederson Device arrived in Europe too late for the war and was never issued. The devices were destroyed after the war and their classification kept them from public knowledge for several more decades. Pederson was a respected gun maker. But this same Pederson failed to produce even one M1 Carbine that could pass government acceptance testing.

Pederson’s failure was due to an outdated method of production. The factory moved carbine receivers from one manufacturing fixture to another as they performed the dozens of steps needed to complete the part. They used fixture pins to position the receiver in each different fixture, and these pins needed a small tolerance in order to fit into their aligning holes. This small tolerance caused a cumulative error in tolerances to creep into the part as it was made — condemning every receiver they produced.

Their contract was finally terminated and General Motors, who was already the largest producer of the Carbine, took over the plant and the guns and parts that were in-process. They finished the few thousand Pederson Carbines that were in a near-finished state before they started stamping their own Saginaw Steering Gear division name on the guns.

I could go on and tell other stories about things that couldn’t be produced. Harley Davidson has a history rich with anecdotes on how not to run a manufacturing operation. But they finally learned their lessons and managed to survive and even thrive in the modern production world, so there is a happy ending to that story.

Motorola almost went out of business because they couldn’t get out of their own corporate way to make anything. They went from being a premier producer of television sets to a company that couldn’t compete in pocket pagers in only a couple decades. They had to reinvent themselves to stay in the game, and in the process gave the world the Six Sigma program.


People ask what this has to do with airguns. Only everything. For starters, airguns are not made in the same quantities as M1 Carbines. Six million Carbines were made by 10 different prime contractors in just 38 months. Few airgun models have ever reached that production number, and those few that did took decades to do so. Even today, airguns are low- to moderate-rate production items. So airgun manufacturers have to learn how to build at low rates and still keep the quality up and costs down.

If you’re going to make a few tens of thousands of airguns, you probably buy your barrels from someone else. If you make them in-house, you do so with affordable production processes and machinery — not the latest and greatest.

But if you are Remington Arms and make hundreds of thousands of different firearms each year, you invest in hammer-forging rifling machines that cost three-quarters of a million dollars each, and you have dozens of them. Then — to keep those machines busy and help amortize their ownership costs, you start shopping for barrel-making contracts wherever you can find them.

Specialized parts can hurt you

Let’s say you want to build a spring-piston airgun that’s never been built before. You have made a prototype and it performs better than anything you ever shot. Now you have raised some capital and you want to use it to manufacture your airgun.

Your airgun uses a 27.5mm ID spring tube that allows it to accomplish everything you desire. There’s just one problem. You made the spring tube for your prototype gun from bar stock. That’s too wasteful, expensive and too time-intensive for manufacture. You need to use seamless hydraulic tubing for the spring tubes of the production guns.

Seamless hydraulic tubing doesn’t come in internal diameters of 27.5mm (I’m making this up, so don’t run to McMaster Carr to prove me wrong). You can buy 26.75mm ID tubing and ream it out, but if you do the wall thickness with be too thin. Or you can buy aerospace tubing in 26.75mm ID and ream it because it’s made from better steel and also has thicker walls. But there is a problem. Aerospace tubing costs 4 times as much as standard tubing. If you use it your gun will cost too much to produce.

Instead, you decide to enlarge the powerplant parts and use 28mm ID tubing, which is readily available. However, the minute your new gun comes to market it’s panned by a dozen internet critics who all say it’s too fat. “The rifle he showed me at the Texas airgun show was perfect. Why did he have to go and screw it up?” Until you have worked through a materials sourcing problem like this a dozen times, you will find it difficult to answer that question.

You see — it’s easy to make one of anything. You just work on it until you have it exactly the way you want it and you’re done. Time is no factor.

Making a million of something can also be relatively straightforward, if not exactly easy. As long as you know how. But to make just a thousand or even ten thousand of the same thing — that can be the kiss of death!

Tooling, technology and schedules

Most of us think about production the way it was done back in the 1950s — machines doing just one operation that was straightforward and relatively simple. They did it fast and, when their operators were used to the pace, they could make many parts rapidly — or seemingly so.

Some of us are aware of modern computer controlled machines that do everything at the same time, or in rapid succession. The parts never have to be moved and they transform from raw materials to finished parts before our eyes. But what only a few people realize is — that’s just the beginning. Following the shaping of the part there can be:

heat treatment
tumbling or blast cabinet
final finishing
packaging and so on…

Manufacturing is a whole lot more than just time spent on a machine. And, once you appreciate that consider this — some of these other processes require scheduling because they are done somewhere else by somebody else.

Maybe the company that does your anodizing charges you a setup fee for every batch of parts they anodize. So you don’t take them until you have enough parts built up to make the setup charge minimal for each part. Or maybe you can’t plate some parts until they are heat-treated.

One company does your heat-treatment and a different company does the plating. So you have to time your production schedule to dovetail into the schedules of both the other companies. A part that only takes 1 hour and 45 minutes to complete can really take up to 6 weeks because of the scheduling. These are the things that are hidden from public view when we talk about production.

It’s not as easy as it sounds

The making of interchangeable parts has been mastered over the last 165 years, but that doesn’t guarantee that all the parts made today will interchange. Sloppy tolerances, inferior materials, dull tools and poor quality control are just a few of the obstacles to be overcome. Automation has changed how we make things in a major way, but not every company is fully automated. And not every manufacturing process can be done by a machine.

When the production numbers are low there is less capital available to purchase even what automation that does exist. So, the making of airguns and airgun parts is a symphony of mechanization and hand operations, each selected to optimize the business situation and produce a viable product.

76 thoughts on “Mass production and interchangeable parts”

  1. Very good! As a former Motorolan myself, with a Six Sigma Black Belt Certificate granted by the company, it is interesting to see how things are connected in this diverse world of ours!
    I think most shooters never really bother to learn about the manufacturing processes involved in making a new gun, or airgun. As an engineer, I have seen modern factories with old manufacturing processes that could not turn interchangeable parts out. It was shocking for them to hear me saying that Mr. Colt could do that back in the 1850’s!

    • Fred,

      A Six Sigma black belt? I worked with a fellow who had a gold belt buckle with diamonds awarded by the Six Sigma program. I learned a lot about what went on from him.

      Yes, it is difficult to understand why the production of parts is so challenging. Until you have worked on the line and seen what goes on, I think you don’t appreciate all that is involved.


      • Haha–yes. I couldn’t even convince my father-in-law that it’ is reasonable for competitive airgunners to need to weigh and sort their pellets. His response was always something along the lines of “the factories should produce better quality pellets.” Easier said than done!

  2. How about putting all your old Airgun Letter articles together in a book? Would be great to be able to put that in our airgun library. Any chance that might ever come to be?

    Just a thought.

    • Jonah,

      Thanks for the suggestion. Yes, I have thought about it.

      Actually, I am about to announce a book I have just published. It will take a few more weeks to get indexed by Amazon, Barnes & Nobel and other book sellers, and I believe Pyramyd AIR will also be carrying it. I should receive the first copy today.

      I thought my next book might be an update of the Beeman R1 book. They are selling for crazy prices on eBay, and now that I have the dream tune on the gun, it’s time for an update. That should happen in 2016.

      After that, who knows?


  3. I was smiling and nodding as I read todays’ blog. Been there, done that – got the T-shirt!

    Think this blog will make many people more aware of how many complex and critical steps there are in any manufacturing process in-between raw material and finished product or how much preparation and setup is required before you can even think about starting the fabrication. I won’t even mention regulatory requirements and restrictions (like RoHS for printed circuit boards).

    My whole career has revolved around Printed Circuit Board design, manufacturing, assembly and testing. Frequently I would have to explain to a customer that I could not give him one of the dozen boards he ordered now and ship the remaining eleven later – that it was like making muffins, they were all “cooked” at the same time.

    The added costs of fine finishing a functional product are added directly to the sticker price. Very often you can find a gem in the rough that with a bit of spit and polish really turns out great. Essentially, you can do what the manufacturer can’t afford to do without pricing the produce out of the market. For example, the Beeman P17 is a steal at $40 that with a couple of refinements is a real nice pistol to shoot. It’s not a P3 but then it’s $200 cheaper and a fun pistol for casual shooting.

    Excellent blog B.B.!


  4. Hi BB,
    I have enjoyed the visits I have had with Crosman engineers at the Malvern Airgun Show. They have explained some of the kinds of things you wrote about today.

    As a contractor, I sometimes try to pre-fab parts according to the drawings. I can get the parts cheaper that way but I loose about 50% due to the building not being perfect or parts being damaged before they can be installed. So, I usually wait until I can take in place measurements and fab the parts right.

    I enjoyed the blog,

    David Enoch

  5. B.B.,

    There’s a great scene in The Good, the Bad, and the Ugly that I always considered as farfetched as it is entertaining. Tuco (Eli Wallach) walks into a gun seller’s shop, looks contemptuously at an assortment, presumably different models by different makers, etc., of used percussion cap revolvers, and disassembles them all. Then he carefully and expertly pieces together a single, smooth shooting revolver by mating the different components from the different guns.

    Great scene, great acting by Wallach, but no way.


    • Remember that one. And he does it with all of his wits after walking 70 miles through a desert with no water. Kind of hard to believe about the guns, but if Samuel Colt really succeeded in making interchangeable parts, then maybe there’s something to this since it’s from the same era.


      • Perhaps, but as I remember the scene (and it has been a while), they were all kinds of revolvers, Colts, Remingtons, off-brands, etc. Just remember the rule of Hollywood: never let the truth get in the way of a good story.


  6. Mr Gaylord
    Is there a pre-production step of taking the prototype to Legal to insure there’s no patent infringement claims waiting in the wings? 🙂 🙂
    William Schooley

    • William,

      Certainly that is a consideration, but that’s called due diligence and it should be done well in advance of production. It’s done in parallel with the design work.

      It isn’t that difficult, either. Many makers copy patented designs that they know are out of patent, so there is no risk. And much of the design will be general enough to be in the public domaine already.

      The real danger comes with those “inventors” who try to get as close to a patented design as possible while still avoiding it. They are like businesspeople who flirt with tax laws so close that they are always risking an audit. What I’m saying is that patent infringement is less often a complete surprise and more often the result of poor judgement.


  7. With airgun production in my country (Philippines) being pretty much as a cottage industry we would really appreciate some form of a standard as far as parts go. Each maker has his own method of assembly. Rarely can you swap pieces from one to another without some handfitting required. Most parts are still made made by hand and guided by eye. No computer programs to tell the machinist what to do. Which also why the volume of production is low and prices relatively high.

    • Siraniko,

      You are describing the way the pistol at the top of this page was made. That was how all guns were made before Sam Colt’s influence began to be felt.

      Oh, the national armories did control the look and fit of certain major parts before Colt, but true interchangeable parts were not known.


      • Some makers have advanced to the use of CNC machines but they are few and far between. Until some form of drastic change (less restriction to owning an airgun, cheaper licences to manufacture, cheaper CNC machines, etc.) come along I’m afraid we are stuck in the late 19th Century as far as manufacturing is concerned.

        Even the screws are not all metric to my knowledge.

  8. On the subject of interchangeability I’d like som input on the 2200A I’m trying to resurrect, the sliding bolt, door and spring are wrecked.
    I figure a 2100 bolt and fabricated probe should work. If anyone can think of a reason it shouldn’t please speak up now because I’m ready to start shooting it.
    I did have a blood blister on my finger for a couple days from purging the charge that has been there who knows how long, anyone have experience with modifying bolt probes?
    Being a clamshell design I’d prefer to get it right on the first attempt.

    • I modified the bolt on a pump pistol, pumpmaster classic, for reduced obstruction in airflow, hindsight says it may have reduced pressure before the shot by increasing volume just after the transfer port… 2xxx series should swap pretty good, just like 13xx did if its any indication.

      • Did you just shave it down or replace with wire?
        The gun I’m talking about is the 2200 magnum Crosman produced in the ’80’s, the bolt probe and lack of BB magazine are the main difference between it and the 2100.
        If I had a place to 3-D printer one I’d probably go that route and just have them make the breech seal the original diameter but I have a 2100b that is in such bad shape it’s good for nothing more than it’s parts. I’ve considered an oversized O-ring glued in front of the.177 breech seal of a 2100 probe but I don’t wanna have to end my first session with a teardown because it came loose.

      • Thanks for the input!
        I take it the mod didn’t quite live up to your expectations?
        I’ve also considered using the .22 probe grafted onto a 2100 bolt via hot wire but think it’ll just add another possibility for failure.

          • The probe tapered down very slowly after the oring so I made it a consistent thickness from the tip to just in front of the oring so it stepped down as a ledge instead of tapering which removed a bunch of material where the air comes at it, theoretically letting it flow in faster and probably not any negative effect, not much positive either but placebo thinking is powerful medicine. I think it chronyd the same, if I remember, but putting a stronger valve spring gave a little, something like 10fps, the longer barrel was the only thing really picking up its step from 9″ to 12″ was 50fps better.

    • I love these types of reads, its like 5 wiki articles completely related by airgunning, takes a lot of grey matter to reach across timelines and pull these things together to make one decisive point! Always impressive.

  9. With all of the issues, no wonder guns can break down in so many ways. It’s amazing that they work at all. For all its problems, the Springfield Armory, according to Clint Fowler, made its M1s to very high tolerances and exact specifications. The gun production process makes me wonder about bolts for bolt-action rifles. It’s well-known that bolts are not interchangeable, so how do they work that at the factory?

    Michael and Dutchjozef, thanks for your response on boxing. I would agree that picking the best technical boxer in all history is futile, sort of like picking the best gun of all time. There are so many variations in style. That’s why I said the best boxer today. Sugar Ray Robinson is an interesting case. He is probably agreed to be the all-time best fighter, and he had an orthodox, classical style. Was he also technically the best? What’s tricky about him, as I found from his book, is that he was a very naturally gifted individual. He didn’t know how he did what he did in the ring or even in his dance career for which he had no formal training. I read his autobiography looking for some insight, and it was all about the money he spent and the women he chased. He is more a case of transcendent talent than anything.

    Jack Dempsey is also an interesting case. He is remembered as a wild man slugger, but his book makes clear that he was extremely technical. He invented the bob and weave technique! And his hitting power relied on a very sophisticated technique which enhanced his natural power. He was like Mike Tyson in his aggressive style, but he was far more controlled and would never have bitten someone’s ear.

    As for today, I think there is a candidate for best technician. I would say it is not Floyd Mayweather as commonly thought because his method is specialized. He combines an unorthodox shoulder roll defense with bobbing and weaving into a counterpunching style that is effective but narrow. Would it be fair to say that someone who is technically comparable in a wider range of skills could claim to be the best technician? If so, I have the man for you, Guillermo Rigondeaux from Cuba, I believe. He has fought some ridiculous number of fights and is the consummate master of everything. The reason that no one knows about him is that he is so small at 127 pounds! I don’t even know what you call his weight class. A great fighter who was fated to be a kind of MiniMe at 1/8 the actual size. The airgun of boxing! But he is fun to watch.


      • GenghisJan,

        In all likelihood, the bolt will drop right in and open and close manually with the op rod whether it be a Carbine or Garand, BUT the headspace COULD change. If the headspace is too short, the cartridge may not allow the bolt to lock into battery and if too long could create an unsafe condition since the cartridge will not be fully supported. Possible misfires and stretching/rupture of the cartridge case upon firing.


      • Yup, and M14/M1A, Springfield 1903, Mausers and just about anything having a moving bolt. Browning A 4 and A6 LMG’s considered adjusting head-space after a barrel change so important they had the artist Will Eisner make a comic-book story about it. (God bless Connie, whereever she may be.)

        • Interesting! I’m relieved that we’re not talking about the kind of 19th-century non-interchangeable parts that B.B. was blogging about, where the actual mechanical parts won’t go together without a good hand fit. Not too surprising that the headspace would require an expert hand.

          Now I want a copy of the LMG-headspacing comic book. I’m imagining it like the old Bicycle Repair Man sketch…


  10. It doesn’t matter how much statistics are kept on parts produced.

    Flyers can happen in production just like what happens when we try for that perfect group we shoot.

    We try to keep in a range at work that we call ppm. Parts per million. The parts produced when you measure them are suppose to fall in a given range. If they fall out of that range the parts are un acceptable.

    Kind of like how the pellet gage works in our air gun world. We collect and document diameters of pellets. If there are pellets that fall out of the predetermined dimension then we have a unacceptable condition.

    The next thing we try to do is improve that unacceptable condition. But if we can’t because we have used all our resources to make that part the best we can then a next step has to happen.

    We have to determine what is acceptable out of that given range of measured parts. That’s where the different pellet head diameters come into play.

    So now is the point in time to know what a certain gun would call a usable pellet. If we think this range of head sizes or diameters will still produce a good shot or group then we can determine if the pellet sizes in that tin of pellets will work in the average types of air guns produced.

    The end result is to produce and package the pellets for the customer and know that the pellets they get will produce a result that will average out to be a usable product for the air gun world in a above average product.

    And then put all those practices into any kind of product produced. Guns, cars, motorcycles, barrels, lasers, scope rings, scopes and so on.

    All in all to make closer to the perfect identical part.

  11. An interesting synchronicity. Friday we just spent several hours at a piano rebuilding concern, at a now closed Naval Air Station on the San Francisco Bay. Bet you’ve never seen 20 plus Gand pianos upended in a former jet engine rebuilding bay. I hear they’re kind of noisy when they’re working. If I could still hear.
    We’re contemplating rebuilding a Mason & Hamlin Grand piano, Ca.1922 and we’re becoming “educated”
    One of the issues is also becoming familiar with mass-production of high-end teeny parts of amazingly complex devices such as Steinways and such…and just why one needs to go back and take a few passes to “true things up.”
    Bearing in mind, the concept is to recognize just exactly the diffence between “just-right,” versus ” forever, forever just wrong” in devices made to be the best…at tolerances in wood measured in tiny fractions of a gram
    No more, no less, the best.
    This ain’t no job for weinies.
    I thought my short stint at Gibson Guitar was an education on just why one needed to invest in a real micrometer.
    Consider if you will, pushing the key on a Steinway or pulling the trigger on a really high-end target piece does not take much being “off” to be detectable to even the most numb of users.
    Forever and Forever, just wrong.
    (I know you want to know, what a serious rebuild runs for that league of device. I’m not going to tell. But the quote would make an adult cry, fart, cry some more, say “huh” “what?,” “that’s more than my first El Dorado!)
    I’m sure glad she’s paying for it.)

    • What would you consider a good micrometer? If just used to find consistancy then repeatability is an important factor, but do cheaper mics build up errors in measurement or start off delayed or early on the count? I have an older one that seems pretty good but have always wondered what kind of accuracy problems can occur.

      • It can be a mess, we had a rotor Mic. with a built-in scroll of the most popular specs and a 1″ standard calibration slug.
        Someone apparently lost the 1″ slug and instead of reporting it replaced it with a roller bearing that was about 7/8″.
        This was one of the first gremlins I found in that shop and it took 2 years worth of comebacks and a new micrometer to get things right. The new micrometer had a magnetic strip and LCD readout that would get grubby but a little brake cleaner on a shop rag and check zero was all that was required to keep it calibrated.

      • RDNA
        I guess all I did was tell you a good mic brand name but not anything about your question.

        Micrometers or any measuring device will have error. There is what is called a standard or set check. It is a gauge block or similar that is a precise size. The measuring devises have to be calibrated or checked by the standard to see if it is measuring correct everytime you want to check something.

        The standard also has to be periodically checked by what’s called a super mic. It is a very precise measuring device. Or other means of precise measuring.

        But here’s the thing every measuring devise including the super mic has to be checked to a precise standard block or set check.

        The whole idea behind all the standard set checks is that all the gages measure the same. That way as a part is made for a assembly that it will be more likely to work with its mating part made in another location of the shop.

        There will always be variation when somethings measured. But the closer that you can make the measuring devises be when measuring to each other it’s one more step to making the perfect parts that will work when fitted.

        I could go real deep into this. There are alot of things that add up in measuring something that can cause a problem somewhere down the line. The best scenario would always be to collect data. Then if possible collect more data with a different measuring device and compare results.

        It all boils down to how perfect you want your repeatability to be in the product you produce. Some things need to be perfectly repeated. Some can get away with bigger tolerances. It’s all about how that part your making will be used.

        • The last I had heard about where the meter came from it was based on the wavelength of excited Krypton atoms, seems they’re gone and changed it again and it’s now based on regular light and the second. If they keep changing the standard for measurement it’s not gonna be easy to use that system.

          • Reb
            Don’t know if that relates to the machining world.

            It’s a pretty simple procedure. There is a dimension you need to hold. Then you get a standard like a gage block that is at the that dimension your measuring. Then you check your measuring device to make sure it reads what the gage block says it is.

            Once you do that then you know your measuring device is reading a correct measurement in that given range of tolerance of that part your making.

              • Reb
                Climate control is another variation to add to the difficulty of checking a dimension and producing identical parts.

                No that’s not what the +/- tolerance is for. The +/- tolerance is given for the fitting of mating parts and also a way to make parts in that given tolreance repeatable from part to part.

                The climate control is a variable that causes the part being measured to change its dimension because of temperature. If a part is hot comming off the machine because of the cutting tools cutting it will measure different than when it sets in a inspection room to be checked with additional measuring equipment.

                That’s a tricky thing about machining. Experience helps you when you check a part. You learn how that machine runs and how the heat affects your measurements. And what makes a good machinist is how quick that person can catch a out of control condition. In other words you measure alot and you know how your tools wearing and how far you can push the tools before changing them is needed.

                Oh and also a good machinist trys his best not to ever run bad parts. That’s like a black mark or a bad reputation. A machinist takes pride in making the best part they can. Seconds are no good in the machining world.

      • RifledDNA22,

        As GF1 has already commented, Starrett is a good brand but so is Brown and Sharpe, Lufkin and Mitutoyo, and I am sure there are others out there.

        With reasonable care, maintenance, light oiling, not dropping them too many times on a hard surface and not using them as a mini C-clamp, quality micrometers should give you a lifetime of accurate service. I am referring to the analog versions which in experienced hands can easily measure within +/- .0001″, I am not familiar with digital ones nor really see the need for them in most cases ( they are more susceptible to damage and require batteries).

        For what it is worth, I would venture to say that the vast majority of all the dial/digital calipers in use by the readers of this blog were manufactured in China, and they work fine, at this point in time, I would imagine that they (the Chinese) probably make/export some decent micrometers also.


        • Bugbuster
          We have those other brands of measuring instruments too.

          Matter of fact I have a little 1″ Brown and Sharp dail indicator on a magnetic swivel base. Nobody gets to borrow that from me. But most of my non digital mic’s and calipers and depth mic’s are Starrett. Well now that I think of it my edge finder is a Starrett also. I do have a Mitutoyo digital caliper and mic also.

          Guess I should of mentioned the others.

            • TT
              With a ton of paperwork to go with it.

              I use to hate when we had to make flight parts. One example is we got contracted to make F18 aileron hinges. I bet there was a paper trail that was 2 miles long of every operation that each part seen. You spent more time filling out paperwork than making the part.

              Same when we use to make the 20, 25 and 30mm progectiles and the M430 grenades. Paper work, paper work is all I can say. We even had to fill out paper work for how thick the paint was after we measured it and also weighed each one before and after painting. Everything was documented. But that’s what happens if you want product repeatability.

          • GF1,
            I am not surprised, there are many old measuring instruments still in use, all you have to do is take care of them, which I am sure that you do.

            I bought a set of 24″ Chinese vernier calipers for my own use a few years ago, I could not justify the cost of set made by Starrett for as much as I use them since I have been out of the trade for near 30 years now.

            Question for you, why is it when you are inspecting a recently completed machine part and you drop it, why does it always land on a hard surface (concrete, steel) and almost never hits on the cast or non critical dimensions? Maybe this has never happened to you.


            • Bugbuster
              All I can say is I hate when that happens.

              And what’s funny is we have carbide 2 fluted step tools that cut stainless steel in 7 second cycle times 3 inches deep by like 2 diameter holes for thousands of parts before needing changed. Then you go to put the new one in the tool holder and its the last tool you have and there’s a 2 week lead time for the tool maker to get you more. Then you drop it and it snaps in half.

              Amazing how that tool will cut through stainless like butter but if you just bump it against something it snaps. Yes I have done that. And it just kills me when they have a critical job that tool is used for and somebody dropped the ball and didn’t have back up tooling ordered.

              The machining world is definitely a exciting feild to be in that’s for sure.

              • GF1,

                You are 100% correct on that, bottom line is, crap happens, and always at the most inopportune time, you have to have back up tooling and repair parts available or suffer the consequences! Somebody did drop the ball, they probably thought they were saving the company money by not investing in the cost of an extra tool in inventory, in the end, a lot of money was wasted since the job had to be shut down and eventually set up again for lack of tooling.


                • Bugbuster
                  Dead on. And that same scenario has happened over the 30 something years I have been doing this machining stuff more times that can be imagined.

                  You can’t produce parts if you ain’t got nothing to make them with. No parts produced no money made. How hard is that to figure out. Crazy is all I can say.

            • You guys don’t have floor mats? I had one in front of my toolbox and that’s where everyone seemed to congregate when work was slow. I was usually only there long enough to load my cart but it was always like a mini-break for my back.

              • Reb
                There is floor mats at the part checking stations.

                The problem is you can’t have them everywhere. And most of the tools I broke on accident is when I was putting the tool holder back in the machine on the tool spindle.

                I’m serious its like your handling nitro glycerin or something. The slightest bump of a carbide cutting tool on something and it breaks. Well of course when you try your darndest to make sure it don’t happen.

            • I just read an article by Popular Science On standards of measure and apparently anything manufactured prior to the early to mid ’80’s is obsolete due to the standard being changed.

              • Reb
                There are different procedures in place not standards.

                Standards is what you use to make sure your measuring instruments all measure the same.

                There is all kinds that have happened over the years. QS 9000 and others have came and then been updated as time has passed.

                What it comes down to is that parts can be produced using a procedure and documenting the results to see if there is out of control conditions and how much out of control coditions exist. There is parts that fall out of the dimensions that are acceptable by the customer. But the end result is to make sure the customer doesn’t get them bad parts.

                How do you make sure that happens? Documenting measurements when you produce parts and segregating parts that have been determined bad. How do you make sure you catch bad parts? 100% screening of key characteristics. Which is what is called a dimension that will affect the performance of the product. Again just like sorting pellet head size.

                A standard and a procedure has to be set and followed.

                • The standard for 1M used to be based on the wavelength of excited Krypton gas light set in the ’60’s however in the ’80’s it was based on regular light speed and the second.
                  I’ll try to get the name of the article to you to check out.
                  Effectively a meter is still the same length but the standard for measurement of one unit keeps evolving to be more and more precise.

                  • Reb
                    More precise is good. But up to the point when you can’t produce a part because the tolerances are to tight.

                    At that point in time you killed the part because you will spend to much money and time trying to make the part.

                • “Where standards for international units of measure come from”,
                  Popular Science
                  I stumbled across it while looking for the Krypton wavelength standard we were taught about in my high school.

  12. Gunfun be right and calls it to the smallest degree.
    Small in this case is good.
    Listen to Gunfun.
    My experience is several decades old, not exactly state-of-art, but that baby still is several quantum jumps better than a duffer like me can realistically utilize.
    The thing is, we always try to eliminate the variables. And if we can eliminate those, meaning “take the variables out of the equation'” we’re going to inevitably improve the consistancy and repeatability.
    In other words, “do science.”
    This is why one buys the best micrometer, a Steinway, a Leica, a….well, you already know what the “best” in your field is, don’t you?
    Well, don’t you?
    Pay the money. You’re going to have it the rest of your life and you’ll never regret it.
    (Usually, I find, you can often charm pretty girls with it, too, whatever it is.)

    • 103David
      Thanks. And I would be sick if I dropped one of those brands you mentioned down in a production machine.

      When that happens they fall down in the coolant tank and we got to wait for the chip conveyor to bring it out into the chip tub. Some machines use oil types of coolant which ain’t bad on the mechanical measuring instruments. But will usually make the digital readout instruments fail. Then there is the water soluable coolant we use in some machines. That really messes them up. When that stuff drys up when the water evaporates it leaves a very sticky oil residue. Not good at all.

      And that reminds me of something. We had a guy that worked at the place I work at. He use to tie a string around his wrist and the measuring tool he was using so he wouldn’t drop it in the machine. Oh and forgot the paddles on the chip conveyers will tear something up as it drags out of the machine.

      But that’s why I don’t use the more expensive stuff. I could probably get away with it in the manual maching area or tool room as we call it. The Bridgeport’s and lathes and surface grinders is what I mean by manual machines.

      And I bet that piano work can get interesting at times.

      • Reminds me also…
        While I remain a pretty competent Duff, (meaning pretty good at being a Duff,) there’s always someone out there that’s better ar Duffdom than oneself. Some years ago, my then teenaged sister-in-law developed an interest in photography and asked if I could find a “nice camera” for her trip to Hawaii. I found a “beater Leica” for her, not even remotely pretty, but very functional. Short version, she returned a thinly coated ball of hardened mud to me that turned out to be the aforementioned Leica.
        The subsequent conversation went something like this;
        Me: So what happened? (Never yell at a female teenager. They cry.)
        Rachel: I accidentally dropped it in the mud.
        Me: And why? (Thinking possibly a tropical 8 pound mouse being involved…)
        Rachel: My feet were burning up.
        Me: After a moment of silence…Where…exactly…were you?
        Rachel: Hawaii. The Volcano. You know, they be kinda’…hot.
        Me: You dropped your Leica in a volcano?
        Rachel: Yup, lava and everything…though it went into the mud. Hot enough. The film maybe a bit…toasted.
        Me: you went back to get it? And it’s still loaded? (Thankful I hadn’t loaned her a .357 Magnum.)
        Rachel: I didn’t want you to be mad, and it was still hot and by the time it cooled down it was all hard and crusty, like this.
        Me: you mean like your Brother-in-law?

        Now comes the unbelievable part. After a fairly lengthy session in the garage with my grandfather’s no-holds-bared-unregulated-3000 PSI-+++-Air-Force-surplus compressor in one hand, and pretty hefty vacuum in the other hand, and a plastic faced mini-mallet in the other hand (we all know this kind of work requires at least three hands and maybe one foot to stand on the leash,) the Leica emerged anew.
        It was still warm.
        It still worked.
        It looked better than before. (Must have been the beauty treatment.)
        I developed the film, and it turned out to be (a little) fogged but okay.
        Life lessons; Before marriage, meet and critically appraise all potential new relations;
        Limit teenager access to volcanos; If they must go, strip them of expensive paraphernalia.
        Teenaged-Sisters-in-laws are a dime-a-dozen.
        Leica M-3, not so common anymore.

        • 103David
          At least she didn’t ask for a Corvette or something. I would bet that could turn out to be interesting also.

          All I can say is if you want to test the durability of something. A teenager will probably give you a good result.

          Expensive toys are for adults if you know what I mean.

  13. I did spindle and splice for a galv line wire mesh fence and lobster trap in rolls. One week was interesting with 5/16″ thick horizontal wire running 1/8″ apart in 8×12′ panels, they were unclimbable prison fences, pretty interesting. Nothing got miced on my line as it was already assembled, we just galvanized it, but I saw all the processes of setting the assembly machines and, yeah, lot of specifics. Theic I have has no name but has a ticker display, it seems reasonable for multiple measurers to be standardized with a slug that all get set by but I never thought to check against a slug at the open position, always thought about the closed position hitting zero meant itd be on time, thus the accuracy question. What is a good “slug” or item that is all but guaranteed to be 1″ or 1/2″ that could be used to check the movement from zero?

    • RDNA
      I just responded to Reb above.

      The set check that you get from a assortment of calibrated blocks has to be selected for a dimension and tolerance that you want to hold when you measure your part.

      That way you know when you measure that given dimension it will be true to the calibrated set check or standard.

      And yes you should zero your measuring device but also check it to the set check/gage block/standard to see if it measures right for that given dimension.

      At work when we make a part there will be some time of gage for every dimension on that part. There could be as little as 5 gages or up to 15 gages or more. Some will be mics and digital gages and some will be plug gages and position gages. There are a precision dowel rods if you will that comes out of a assortment of gages. They will be set up to measure as a go and no go gage for a specific dimension. More than likely to measure a hole diameter.

      The whole thing about it all is that a part needs to be measured accurately on all dimensions. That way the part your making for the customer is as perfect as can be made with the processes involved.

      The blue print is the bible. Anything that falls out of tolerance from what the blue print says is scrap.

  14. Ah yes, the blueprint. That brings up the whole other end of the tolerance business – the engineer(s) who make the design who don’t often really understand the details of precision, tolerance and interchangeability, and therefore over-specify the tightness of the tolerances, so the part is impossibly expensive to make.
    Never happened to you?

    • Gerhard_k
      Yes that has happened. Then they realize how quick the company lost money.

      You know what happens next? That engineer gets schooled real quick and keeps their job or they stay stupid and its see ya for them.

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