Same or Dissimilar....that is the question

[i44troll]

I've built an automatic tool changer prototype for my bench-top CNC mill out of 6061 Aluminum. Now that I have all of the mechanical problems worked out I have chosen to manufacture it out of 303 stainless. My question is... should I use two totally different alloys for the spindle and the toolholders or will it be acceptable to build it all out of 303? There is a maximum of 6° possible slippage between the toolholder and the spindle (20° taper) with 70 lbs clamping pressure. If it is recommended to use a different alloy what other stainless alloy could be used with 303? Thanks in advance!

Chris

 

[EdStainless]

Why 303 at all? It is soft, prone to galling, and will wear.
If you really want stainless, then go ahead and make the easy to replace part from 303, and make the mating part from 420 (preferably quenched and tempered, a high temperature temper 1050-1150F would be good). The 420 isn't as corrosion resistant but it will hold up well and provide some resistance.

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P.E. Metallurgy, Plymouth Tube

 

[i44troll]

Thanks Ed
I am a machinist but weak on metallurgy. Took a 16 week class that got my fingertips wet but never got further than that. I have found some info in the machinery handbook and some metals distributors have decent information of the uses of stainless but most only touch the surface. If there was a good book to add to my library that explains the characteristics / differences of metals and their uses (or why NOT to use them) I would jump on it. In the mean-time, I plan to scan through these forums to see what I can find. I know these forums are for professionals....hope I don't get booted for being a newbie. Thanks for the feedback! I will definitely use it.

Chris

 

[EdStainless]

You should pick up a book by McGuire called 'Stainless Steels for Design Engineers', it is published by ASM International (ISBN: 978-0-87170-717-8).
It may be a bit more theory than you are looking for, but it is reasonably complete and up to date (and McG posts here).

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P.E. Metallurgy, Plymouth Tube