Laminating material

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Tuba Dave

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So forgive me if this is a crackpot idea. Say I want to replace the compound slide on a lathe with a solid toolpost. Conventional plan is to machine a block of cast iron. On hand I have much cast iron in plate form, and it was all free. Why shouldn't I laminate the plates to make a larger block? Also, I have no welding capability, but I solder and silver solder brass for a living.

Should I assume connectors are needed between the layers, like threaded rod? I could even solder these in place. Strategically placed so as not to interfere with machining the final shape.

Or make the part in layers, like a 3D printer, and connect them after machining.

The assumption is the rigidity of a laminated part is dependent on the fit and connection between them. Would a tight fit and silver soldered threaded connectors be sufficient? There isn't much shear on a toolpost, mostly vertical forces.

I guess it comes down to free stuff vs $100+ to buy CI stock to use.

Thanks for your input.
 
How thick of material are you talking about ?
 
If you have a way of heating the entire block sufficiently I don't see any reason it wouldn't work. Brazing would be my choice over silver solder. The cast iron would just need to be machined clean. As to technic do some trials and then cut through the blocks to be sure you are getting good bonding. A furnace would seem ideal. My only concern would be trapping the flux between layers making it weak. Perhaps "tinning" the parts with braze then stacking and heating the entire block would be the easiest way to ensure full coverage.
 
Cast iron and braze get along well together. Brazing is a common practice for repairing cast iron. The materiual is virtually free. Why not give it a go?
 
What soldering tools do you have?

If you don’t already have oxy/actelene could justify the purchase or borrow a setup?

Pre/post heating can be done in a gas bbq, I suspect you’ll end up with the prettiest solid tool post ever.

John
 
Thanks for all your help.

I have an oxy/acetylene setup, but only an M tank size with jewelry torch tips. I have a B tank for the larger torch (acetylene and air), so I think getting a new torch for the larger oxyAcety setup might be the way to go. (always better to invest in tools (capital)rather than materiel (consumable)) I am very familiar with brazing brass, and can apply the technique to iron, hopefully.

The material I have is various thicknesses from 1/2 to 5/8 of an inch thick, salvaged from an old bench vise, some grinder stand(s) and things like that. I don't know if an oven is needed as these parts are not too thick. I like the idea of tinning them beforehand, as the capillary action might not reach all the way into the middle of a 3" square part. Also, the doing one layer at a time this way might reduce the necessity to heat the entire block up, as only the mating surfaces need to be heated up to the temp needed. (correct me if I am wrong) I regularly solder multiple parts together at different times and am used to not letting the heat travel to an already established joint. After many self-induced "de-solderings", I can foresee that frustration.

I gather that fasteners might not be necessary if the braze is good. This would help as then I would not need to (plan to) avoid them on the mill.

This is turning into an interesting project.
 
Have you considered not using cast iron or steel and instead use a block of aluminum topped with a piece of precision-ground steel flat stock on top? As you say, in-use loads are compressive and aluminum has proven to work fine in this application. Sure would be easier to do than laminating a cast iron block. Or just buy a solid block of steel or cast iron and be done with it?
 
mikey said:
Have you considered not using cast iron or steel and instead use a block of aluminum topped with a piece of precision-ground steel flat stock on top? As you say, in-use loads are compressive and aluminum has proven to work fine in this application. Sure would be easier to do than laminating a cast iron block. Or just buy a solid block of steel or cast iron and be done with it?
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Of course, that is good advice. I was led to this idea by the cost of purchasing a cast iron block big enough to make this (I have a Logan lathe and I'll need a 4x4x3 block plus extra for mistakes) That looks to be around $300 at McMaster Carr. An oxy-acetylene torch kit will be about half that. The iron is free and on hand. Plus the learning experience.

I will consider the aluminum and ground steel option. That might be easier on the mill anyway. Minus the learning experience (read "possible frustration"! -- I have never learned to include errors in my project planning, a fatal flaw)

Thanks for everyone's insight!
 
Totally understand, Dave, and I wasn't trying to discourage you. Sometimes its more fun to experiment and that's what hobbies are for, fun.
 
With compressive forces the concern what would happen if you JB weld 5 or 6 pieces together? would definitely be easier if the surfaces are flat and free of occlusions. I did the solid toolpost on the carriage but took it off cause I didn't see a difference.
Biggest difference for me was proper insert or HSS profile, speeds and feeds ,and minimal tool overhang.
Also replaced the PM toolpost with a DTM and except for the smoothness and superb fit and finish on the DTM didn't see a diiference on the actual machining on the lathe.Lathe is a PM 1340gt which I balanced and added 600 to 700 pounds to the base.
 
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