tumbler mill

[David R. Pennington]

http://i2.photobucket.com/albums/y32/northwoodsforge/TriggerTools003.jpg

Here is a picture from an older thread of a very fancy tumbler mill. How was the tumbler rotated to provide the cutting action. I've looked at this for a while and can't figure it out. I see how it is adjusted to give the proper thickness. If the mill is rotated by the two wooden handles how is the tumbler held stationary?

[whetrock]

My understanding (based on JHAT vol 1) is that the tumbler was rough forged with the large axle left quite long and tapered (cone shaped). That tapered end would stick down through a hole in the lower cutter, and could be gripped in a vise.

In that method, the tumbler did not move. It stayed stationary and the mill was turned around it.

[whetrock]

To elaborate a little… The JHAT article says that the larger axle was first filed almost to size, and then (with the mill disassembled) the tumbler was held in a hand vise and turned into the lower cutter, until the main body of the tumbler reached the cutter. THEN, with the main axle shaft sticking down through the hole, the cutter was reassembled and the excess portion of the axle sticking down through the lower cutter was then clamped in a vise. The tumbler then stayed stationary and the mill was turned to mill the faces and to cut the small axle.

I have carpal tunnel syndrome and tendonitis. If I was doing this, I would try to avoid using the handvise in that manner. Turning something into a hole like that (twisting, screwdriver motion) absolutely kills me. I think I would try filing the large axle almost to size, then clamp the tumbler body in the vise upside down with the large axel pointed up. I would then take the tumbler mill apart and turn the lower cutter upside down and fit it onto the large axle, turning it on much as you would turn a die onto a shank to make a bolt. When it reached the face, I would then take the tumbler out of the vise, flip it over, reassemble the mill and continue. (I have not tried this. Just thinking out loud here.)

[James Wilson Everett]

Guys,

I was just going to add this to the lock making thread.  To make a tumbler I start with a 1/2 inch square bar of W1 steel - very much the same as 1095 steel, water quench hardening.  I forge the end into an "L" shape somewhat duckfoot shaped and try to get the outside corner rather square.





This is all the forging - Now I cut the piece from the rod with more than an inch on the long part of the "L".  Using a file I round this leg to a tapered pin that is just a bit oversize from the anticipated tumbler axle diameter.  A caliper is a great help in keeping the size correct.







Now to start using the tumbler mill.  This one was made from the design in JHAT, but I added various holes to round up iron rods for screw making in the field.  No need to waste the rest of the tool, actually I use these various small holes to make screws more often than I make tumblers.





The rounded leg is slightly tapered so it will pass about half way through the tumbler axle hole I plan to use.  The mill half is now used to round off the remaining axle to the proper diameter.  The forged "duckfoot" blob is held in a vise with the rounded leg vertical and the action of the mill half is a lot like using a die stock - turning is leftie-righty while pressing down.  If there is a lot of metal to be removed I just use the mill half to mark the piece and use a fine mill file to remove most of the metal.  The tumbler mill is used only to remove just a hair of metal.


This is done until the tumbler axle shaft and the one surface of the "duckfoot" are true.  Later the other half of the tumbler mill is attached to start forming the opposite pivot pin and opposite side.  The reason for the longer tapered rod is to allow the rod to be held in a vise for this step.  However, I will stop here as I will wait for the next visitor show-n-tell to do this work.  Here is a nearly finished tumbler set back into the mill to show you how it looks.










Jim

[whetrock]

Great photos, Jim.
I'm assuming that you mark the position of the small axle by turning the mill, then remove it and do much of the filing by hand, then put it back in the mill to clean it up and center it perfectly. Is that correct?  (The JHAT article talks about that on page 37. The article suggests that doing it that way helps avoid wearing out the cutters on the mill prematurely.)

We all look forward to the full installment.
Whet


PS:  For any new guys unfamiliar with the JHAT, I'm referring to this article:
Brumfield, Gary. 1985. The Production of Flintlocks Used on Colonial American Rifles: Raw Materials, Tools, and Technology. Journal of Historical Armsmaking Technology. August. Vol 1. p 1-83.

[Pete G.]

Sure makes one appreciate clicking a few buttons and having a completed lock delivered to your doorstep.

[James Wilson Everett]

Pete,

Yes, you are right.  The JHAT tumbler mill, and the one I adapted from JHAT is such a non-aggressive cutter that it is used almost like candle blacking.  Just to highlight where to use a file.  Really, it is used only for the very final cut.  As for the tumbler mill shown by David at the start of this topic - it makes me break commandment #10 all to pieces.

Jim

[Mark Elliott]

Jim,

I like the idea of drilling holes in the tumbler mill to cut your screws and screw heads.   I am going to copy that idea on my next one.   

[David R. Pennington]

Thanks Whetrock. That clarifies things for me. I can see how it works now.  Jim, am I correct in assuming you anneal the file and drill then reharden? I may try forging out some tumbler blanks next time I get the forge going. I'm thinking some die blocks would be handy to help forge out closer to shape if a bunch of these were to be made? Save some on filing? I cut a couple chunks off an old piece of 1 and  1/8 inch octagon tool steel I had and will see how it machines. How hard should the temper be drawn on a tumbler? Jim did I remember seeing somewhere that you made tumblers out of wrought and case hardened? How do they hold up?

[whetrock]

The JHAT article shows three types of mills. The mill that you linked us to, David, is what the JHAT article calls the British type (fig.25). Like the one you show, the one in the article has removable mill-type cutters, held in place with a set screws. That means that the cutters can be removed for sharpening.
The second one the JHAT (fig. 26) shows is a simpler type, an antique, made with plate construction, with hand-raised file-type teeth. The plates are, quite interestingly, very short. The JHAT article calls it the Continental type.
The article also shows a third mill, from an image from Diderot’s (1751-1765, French) Encyclopedie. Diderot’s image very clearly shows a long, plate-style mill with multiple holes. Granted, it’s an old woodcut image, but a close look with magnification seems to suggest that the tool was made from a recycled files. It also shows multiple holes--perhaps just because they get dull so quickly, or perhaps some were also screw cutters (like Mark noted). (The JHAT article also shows a tool made in the CWF shop (figs. 28, 29) which is of the Diderot type and is very similar to Jim’s tool.)

It seems to me that there are two problems with using files to make these kinds of tools. First is the annealing processes, which (as you asked, David) is required before you can drill the holes. I’ve not been very successful at doing it without damaging the carbon content of the teeth. That is to say that the teeth get somewhat burnt and then don’t hold an edge very well after the tool is made and rehardened. Now I suppose (based on reading about how handmade files and rasps are made) that the trick would be to cover the teeth with some sort of flux, but I’m at a loss for the how and what. (I’m certainly open to suggestions on how to do this more effectively.)
A second and more fundamental problem stems from the fact that a file is made to only cut on a forward stroke. All the chisel-point teeth point in one direction. But the tumbler is turning in a circle. That means that at best only ¼ of the surface is actually cutting anything, while the other ¾ is actually just holding up the material and preventing cutting. That makes for a very ineffective cutter. It a fundamental flaw in the design—one that is not going to be overcome by improvements in annealing technique, etc.

What about the other two types?
The antique tool in the JHAT fig 26 shows a plate style tool that I think would have with a face of annealed smooth steel, and then the cutting teeth were hand-raised afterward and harden. That tool was not made from a file. I wish we could see it’s cutting face, but the image doesn’t show it. (The caption says it is owned by the CWF collection. Maybe one of us could ask to see it???)
Regarding the mill cutters, I’ll quote something from another book, Steele and Harrison, regarding a mill cutter made for shaping breech plug blanks. “Eight teeth are enough for the smaller sizes of these tools. If made with more teeth they are consequently finer and shallower and do not operates so well, or cannot be ground to an edge or sharpened with an oil stone if they become dull” (p 169). My point is to note the word “sharpen”. That’s a big advantage of the mill-type cutter.

It would be nice to have a tumbler mill that could be sharpened. But efficiency of production gets in there. Making the tool from files is a pretty time-efficient method. Drilling holes in an annealed file is easier and faster than making precisely shaped mill cutters.

I suspect that what we see in these contrasting kinds of mills is similar to what we see (or at least think we are seeing) in many other types of tools, dies, etc. That is that the specialized shops took the time needed to make high quality tools that would last and which could be used for a long period of time. The Continental smith, who could often buy locks but who on occasion needed to make one or to clean up a tumbler for repair or lock tuning purposes, was content with a simpler tool. The simpler tool was good enough for lighter use. That’s my interpretation, anyway, for what it’s worth.  


Refs:
Brumfield. 1985. The production of flintlocks…. JHAT vol. 1
Stelle and Harrison. first ed. 1883. (2013 reprint). The Gunsmith’s Manual.

[JCKelly]

Mr Everett, I suppose you already know this but for the rest of the world -

Having forged that W1, you will end up with a tougher scear notch, less likely to chip, if you anneal the forging before hardening & tempering it. This is because here & there that forging likely has some very coarse grained areas. Annealing can refine the grain, which makes the thing tougher, even at the same hardness.

This morning, alas, I cannot find my edition of Robers & Hamaker, Tool Steels, for a detailed story. So I would just say heat the thing a nice bright red & bury it in ashes, hot sand, vermiculite - whatever - let it cool slowly. Then machine it to shape & heat treat it.

In Ancient Times, American steel companies used to put out useful data. One of the best is Modern Steels and Their Properties by Bethlehem Steel. The older hardcover editions are best, mine is 6th edition 1961. This had "Color Charts", page 145 showing red-hot colors versus temperature, and also the temper colors from straw through blue. By the 7th edition 1972, silver-colored paperback, they had deleted these charts.  This morning one may get a 1966 version for about $15 on abebooks dot com. I've never seen the 1949 or other older editions, but 1966 or earlier will be helpful to the non-metallurgist who must heat treat by eye. If you find it too technical, just do not read it like a novel - read it a couple of times, with a rest period in between. Then read it again.

[JCKelly]

Whetlock - log on to brownells.com and search for "heat treating" They have lots of interesting stuff.

Specific to your needs is a can of  Brownells Non-Scaling Compound, about $25.

 have never used this myself. I do imagine it is a $#*! of a lot easier to get ahold of than the potassium ferrocyanide needed to make up the good old mix that Nicholson File used to use, when things were actually done in the USA with a minimum of assistance from Our Gov't.

[whetrock]

Mr. Kelly, Thanks for the tip. I appreciate your help.

Re types of mills... Let me add that the Sprengel article (JHAT III, 1988, p 34) also talks about the manufacture of a tumbler mill, and the wood cut shows a mill of yet a forth type. I find it a little ambiguous, but it seems that it may suggest making a frame into which cutting plates would then be fitted. The Sprengel article is a reprint from a publication that originally came out in 1771.

[JCKelly]

Just a fyi.
I have examined locks from early US muskets, say 1812 - 1840.
On the earlier ones the lock screws appear to been clamp milled, much like the tumbler mill discussed above.
In the later muskets the screws appear to have been turned on a lathe, just as Us Moderns would do.
Guess I shoulda took pics.

[David R. Pennington]

Someone had an antique tumbler mill for sale the last time I was at the CLA show but I had already spent my dough on gun parts.

[Mark Elliott]

I know someone that bought one in the last year; I don't know where.    I told him to call me first if he wants to get rid of it.   I don't think that will happen anytime soon.   He told me that what he had to pay for it hurt.   

[David R. Pennington]

Jim, how do you center drill the tumbler shaft for the screw?

[Steve Bookout]

Here's a couple pics of my tumbler mill that is depicted in Notes From a Small Iowa Rifleshop.

[James Wilson Everett]

Guys,

In reply to the question from David, actually a very good question.  I drill the hole for the screw in the tumbler just the same way as any hole.  When the crowd is watching at a show-n-tell I use an 18th c fishtail bit followed by a special tapered square reamer.  Normally, I ream holes with a long tapered reamer where the hole is through the metal and not a blind hole as with the tumbler.  The reamer just extends through the far side of the hole until the proper diameter is cut.  Here are photos of the drill and the reamer in a typical lockplate hole, they would extend through to the far side.  Actually I use the tapered reamer from both sides so the hole is a tiny bit "hour glass" shaped.





The tumbler screw hole is a bit more difficult:

It is a blind hole - does not extend through - and is a lot more deep than the typical 3/16 inch lockplate.  When drilling this by 18th c tooling it can be a real adventure.  Also, since it is a blind hole the long tapered reamer cannot be used, a special short reamer must be used to bring the hole to the proper size.  When forming this hole I make the hole diameter a bit larger than normal.  Normally I cut the hole to 0.147 inch diameter for threading to a 0.174-30 thread.  This gives a smaller thread height in the female threads and a weaker threaded joint, but it makes forming the female threads a bit less likely to result in the adventure of a broken tap stuck in a blind hole.  I am sure that many of us have had that nightmare of breaking a tap in a blind hole - now what do I do?

Jim

[David R. Pennington]

Jim, how do you center the hole in the tumbler shaft? Do you simply spot it and drill by hand with brace or do you have an ingenious 18th century method for centering and keeping hole parallel with tumbler shaft? I really would like to lean over your shoulder some.

[rich pierce]

Show us how it should be done, Tony!

[JTR]

Well Tony, I can hardly wait to see your write-up and photos of Your Historically Correct version of making a tumbler!

However, at this point, all you’ve done is reply with an unwarranted snarky remark!

Talk is cheap dude,,, let’s see some results!

John

[James Wilson Everett]

Guys,

Well, I couldn't wait for the next show-n-tell, so here is the next step in tumbler making.  Holding the duckfoot blob in a vise, you turn one half of the mill onto the shaft until it bottoms on the blob.  This does not take a long time, but it does help to oil the shaft as it will be very tight in the tumbler mill hole.  Here is what it looks like at this stage.



As can be seen by how far the tumbler mill in spread apart, there is still a lot of metal to be removed.  When at finished thickness the threaded studs on the tumbler mill will bottom on the brass spacers.  You stick a scribe through the tumbler small pin hole to mark the center location of the small pin.

A good way to decrease the tedious filing is to reforge the tumbler in a die plate.  Here a thick steel bar has been bored with a hole only a tiny bit larger than the tumbler mill hole.  Heat the tumbler red hot, insert the round pin into the hole, and bash the top down onto the top surface of the die.  Now the one surface of the tumbler is a whole lot more flat & square with the pin.





The die can also be used to adjust the shape of the tumbler blob if needed.

Jim

[Mark Elliott]

I have made a number of tumblers, far more than I wanted, in the manner shown in JHAT I using a tumbler mill made of a file.   This is a tool that was documented in period literature and while not at good as the 19th century factory make tool,  it does work as long as you hand file the tumbler reasonably close and only use wrought iron or mild steel.
It is unrealistic to expect plain carbon tool steel or case hardened mild steel to cut anything other then annealed iron or mild steel.   Even the factory made mill won't cut anything else.

I make probably half a dozen tumblers,  mostly of O-1 (a big mistake from which I learned) before I wore out my mill made of a file.  I plan to make another one and believe that it will cut much better and last longer by changing the process of annealing and re-hardening the tool.   You loose a good bit of metal in the teeth by repeated heating and loss of carbon.   Given that I was doing everything in a gas forge in a oxidizing flame and over heating,  I was loosing far more metal in the teeth than I needed.   The next time,  I am going to score and break the file so that I can put it in my heat treat oven for annealing and re-hardening.   That way,  I will only heat just enough to accomplish my goals and not have to subject soft teeth to Pearlite for annealing.    Additionally,  I plan to re-harden using Kasenite to replace lost carbon in the teeth.   All of this is to preserve as much of the original sharp teeth as possible.   I believe those efforts as well as never using anything but wrought iron in the mill will make it much more effective.

I would also like to say that I have minimal filing to do to prepare the tumbler blank for the mill.   As in JHAT,  I forge my tumblers like a nail or bolt using the 3/8" Pritchel hole in my anvil.   That means that the shaft and body of the tumbler really only requires me removing the forge scale to go in the tumbler mill.     After all, the shaft is perfectly round and exactly the right size at the tumbler as long as I am cutting an 11/32" shaft in the mill.   I get to choose what size shaft and axle the mill makes, so I choose a size convenient with my forging process.   I am also able to forge the tumbler body pretty flat and parallel to start.   The only problem I have is to make sure I upset enough metal for the tumbler body.   That is why I have a little brass pattern of the tumbler that I can lay over my forging.

The point of all of this is to say that I believe the tumbler mill made from a file is a perfectly workable 18th century and earlier tool.    It I wanted to make more than a few fully hand made locks in the period correct way, then I would make one of the factory type tools, but as I only want to make a couple fully hand made locks,  the file based mill should work fine.   For all other repair work where I need to make a tumbler,  I take my forging (it is still quicker to forge a blank, if you can, than turn from solid stock) and put it in my lathe.    A cobalt tool bit makes quick work of it.  

[James Wilson Everett]

Mark,

Thanks for the great information.  I really don't forge the tumbler blank anywhere near the final shape, maybe next time I will get it closer.  The mill I made used what I believe to be a too fine file.  The tiny teeth fill very quickly and it is difficult to clear the chips without disassembling the mill.  I think that the mill made from a file posted by Steve Bookout is probably a better one as it appears to be a good bit more coarse than mine, and probably does not need to have the chips cleared quite as often as mine.

Jim