Some basic questions about wax chucks

NigelW

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Jan 2, 2015
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I have been reading about wax chucks in de Carle's Watchmaker's and model engineer's lathe with a view to upping my game, especially in turning and finishing components on a smaller scale than I am used to.

One problem I have been having is facing and finishing my wheel blanks. In the past I have made wheels out of brass sheet and turned them to the right diameter using a mandrel. The sheet is of uniform thickness and well finished so it has not been necessary to skim the surface.

Cast brass is a different matter. Not only is it rough it also needs work hardening by hammering. Any blanks made from this need turning not just on their edges but also their surfaces and when they are very thin holding the work becomes tricky.

I am now thinking that a wax chuck might help. My understanding is that these have to be made of brass (not sure why) and that shellac is used to attach the work.

My questions are:

- is there a practical limit to the size of work which can be held this way as wax chucks seem to be very much a watchmakers' thing?

- how smooth does the surface of the work need to be for it to adhere to the chuck? Would a piece of rough cast brass stick? or a freshly hammered piece?

- is the chuck intended to be somewhat sacrificial? One operation de Carle discusses seems to involve cutting right through the disc, which would seem to risk damaging the chuck. It that perhaps why they are made of brass, so as not to damage the tool?

- I can see why shellac is such a good material; it is reversible and sets slowly as it cools, allowing the work to be centred and pressed on nicely as it is doing so, but are there any more "modern" ways of sticking the blanks on which are as good to better?
 

glenhead

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The only limit to the size of piece you can turn on a wax chuck is what will spin on your lathe. If it's a jeweler's/watchmaker's lathe you can turn the headstock around and have the chuck hang off the end, and then the sky's the limit. Torque quickly becomes an issue, though, so from a practical standpoint you're better off staying within the swing diameter of your lathe. Light cuts with a sharp graver will bypass a lot of the torque issues, with the added benefit of reducing the heat generated.

One of the glories of a wax chuck is that with a heavy enough layer of shellac you can mount any danged thing you want to it. The shellac holds really well. Yeah, things might pop off occasionally if you snag the graver, and heat can be an issue.

Another glory is that the surface of the chuck is indeed sacrificial. Dork it up and cut it off. Cut through the piece you're working on - who cares? :) Cutting grooves in the surface increases the grip of the shellac, too.

I frequently use super glue for mounting things. A thick super glue gives a bit of working time, but it's still very limited relative to shellac. Shellac dissolves completely in cheap denatured alcohol, where super glue needs acetone. Either one will release with a bit of heat, but shellac releases at a much lower temperature. Again, grooves provide more grippy-tude. (That's the technical term, of course.)

I've used brass, aluminum, nickel, steel, and wood as wax chucks. "Ooh, there's a leftover piece of <material>, I'll add that to the sacrificial mounting surface pile!"

Hope this helps!

Glen
 

Willie X

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Feb 9, 2008
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I'm with Glen, lots of things will give good results, and a rough surface with saw cuts is just fine! For thicker irregular items you can use a cup shaped plate with pitch (hard tar) in it. Just push the workpiece into the softened pitch and put it in the fridge for a while. Willie X
 

Jerry Kieffer

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May 31, 2005
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I have been reading about wax chucks in de Carle's Watchmaker's and model engineer's lathe with a view to upping my game, especially in turning and finishing components on a smaller scale than I am used to.

One problem I have been having is facing and finishing my wheel blanks. In the past I have made wheels out of brass sheet and turned them to the right diameter using a mandrel. The sheet is of uniform thickness and well finished so it has not been necessary to skim the surface.

Cast brass is a different matter. Not only is it rough it also needs work hardening by hammering. Any blanks made from this need turning not just on their edges but also their surfaces and when they are very thin holding the work becomes tricky.

I am now thinking that a wax chuck might help. My understanding is that these have to be made of brass (not sure why) and that shellac is used to attach the work.

My questions are:

- is there a practical limit to the size of work which can be held this way as wax chucks seem to be very much a watchmakers' thing?

- how smooth does the surface of the work need to be for it to adhere to the chuck? Would a piece of rough cast brass stick? or a freshly hammered piece?

- is the chuck intended to be somewhat sacrificial? One operation de Carle discusses seems to involve cutting right through the disc, which would seem to risk damaging the chuck. It that perhaps why they are made of brass, so as not to damage the tool?

- I can see why shellac is such a good material; it is reversible and sets slowly as it cools, allowing the work to be centred and pressed on nicely as it is doing so, but are there any more "modern" ways of sticking the blanks on which are as good to better?

I collect vintage tools utilized for small parts and often demonstrate their use at various shows. The attached photo is a wax chuck lathe from around the 1850`s that was designed for wax chuck use only. In working with these types of tools and methods, you quickly learn that accurate consistent success is a long skill oriented venture.

Most of my work is micro work including parts that are smaller than watch parts. While I am familiar with Wax chucks as mentioned above, they have offered no advantage in my daily work.

What equipment are you using and how large are your wheel blanks and other parts ?

Jerry Kieffer

fullsizeoutput_111.jpeg
 
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Harry Hopkins

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This is my variation of the wax or shellac chuck. The first picture shows the chuck I made. It is 2.5" diameter aluminum and about 2 inches long. The arbor is precision ground 3/8" drill rod. The second picture shows it mounted on my lathe in Sherline's 3/8" end mill holder. Mounting this way has a very small amount of runout so the tool can be taken in and out of the holder as many times as necessary and it will remain true. Picture 3 shows a pocket I have bored in the aluminum the exact size of the wheel I need to machine, You can also see I have cut some grooves as mentioned above although I use super glue and not shellac. (I want to try this with shellac just to compare). The super glue releases quickly with heat and I have not had a part come out after many uses of this chuck. Of course the aluminum is sacrificial but I have probably only used less than a half of an inch in the last year when I need to use this tool. Picture 4 shows a part super glued in the pocket.. This particular part is part of a clock mainspring barrel where I am replacing the sleeve portion due to the original sleeve being mangled. This setup allows me to cut a groove for the new sleeve and guarantee that it is concentric. I dislike mounting anything with teeth in a 3 or 4 jaw chuck and this is quicker for me than mounting the piece on an arbor and using a test indicator to adjust it to run true.

12929.jpg 12935.jpg 12937.jpg 12939.jpg
 

glenhead

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Ding ding! Pictures that speak a thousand words. Thanks, Harry. That's a nice beefy chuck. Having a cup like that so it custom-fits the piece is a real luxury for repeatability.

The biggest difference that I've seen between shellac and super glue is that the shellac is adjustable. Yes, the super glue will re-cure if you heat it, but it still cures annoyingly quickly for those times when the danged part doesn't want to cooperate. I've never really experimented with it to see if the glue loses any strength from heating, and have always wondered about that. The shellac will soften but stay nice and sticky so you can fine-tune things while the chuck and shellac cool, and the shellac retains its strength through repeated cycles.

One really big advantage to the super glue is that it's not worth beans in shear strength, so you can smack the part parallel with the chuck to pop it loose, if it will withstand that kind of abuse. Think a hockey puck glued to the ice (sort of, work with me here...) The really-thin layer of the super glue usually means that when you pop the part off there's very little glue residue left to clean from the part. On the other hand, the shellac just drifts away in an alcohol bath, so that's good, too.

Super glue is available at the grocery store, but it goes bad after a while. Flake or stick shellac lasts forever, but it's not particularly easy to find. (Except online, of course.) I like the smell of the shellac better than the tang of super glue. Advantages and disadvantages, the story goes on...

Glen
 

RJSoftware

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Another option you might find a little kinder than shellac or super glue is "hot glue" from typical glue gun.

The trick about the wax chuck is the centering. Shellac is temperamental, sometimes good - sometimes not, and tends to be brittle. Super glue dries quick, can be messy, mess can be disaster.
Hot glue is relatively strong, but slightly flexible.

So you can heat hot glu over and over again. Most time to perfectly center you can get away with touching object with fingertip while it rotates in the lathe.

What your probably finding is the shellac chuck is the most practical way of centering an object especially at the microscopic level.

When you make your wax chuck make it relied center by the glue. Example: watch staff normally pivot tip bottoms into cone of wax chuck. the glue holds stationary. But if wax chuck is unscrewed/removed from collet then cone center is off. So instead of using pivot tip use staff shoulder. The wax chuck can find center without the cone tip restricting location. The more free floating relying on glue, the more capable it is to center.

A member here who introduced the use of hot glue has youtube vid of using hot glue to reshape a tiny tiny tiny watch jewel by sticking jewel on small blob of hot glue on end of dremel shaft, then centers the jewel with point of sharpened tooth pick while cools. Then he used flat small steel with diaminteen paste to grind the jewel so it would fit.

This point I bring to you is to show the freedom of choices you can make that can still produce highly accurate results. The trick of it is in the centering.
 
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RJSoftware

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Ha, found him on the youtube....!
 

Harry Hopkins

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Thanks to all that have offered alternative methods. I have enjoyed reading all the suggestions of pros and cons of Shellac vs. super glue vs. hot glue. I think each has it's own merits and faults. Probably best to decide on a case by case basis. One other method of holding work (at least clock size work) such as we are discussing is a Pie Chuck. I have investigated Sherlines Pie Jaws and while I think it would speed up the process of machining wheels, etc the aluminum jaws are $81 and they are sacrificial also so they will not last forever and if you don't already have the appropriate chuck to fit them on it will cost you an additional $199... at least they will hold your parts safely without any sort of messy adhesives or shellac. I only have a use for this sort of specialized holding every few months so for me I will probably stick with my proven method of holding the parts with super glue or some other adhesive.
 
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