Millturn workholding! (with pictures)

Hello friends,
I wanted to share two ways of gripping dovetailed stock in a power chuck;

I do the programming and setup on two multusb200 machines and started doing so about 3 years ago with practically no prior turning/using a lathe experience, and had a few parts fly out of the chuck.

Also there have been times where the I milled parts on the multus and had them vibrate a bit and start to come out/rotate slightly of the chuck jaws (hardened serrated jaws)...

It led me to search for solutions mainly on the internet and the first solution is;
turn the stock to a taper of 3 degrees (and the chuck jaws as well) and this serves well and enables counteracts the pulling forces that try to pry the material from the chuck, but do not provide a safe method to counteract rotating in the chuck due to agressive milling.

the second solution I came up with recently comprises of three 60 degree dovetailes - protruding about 3mm and equally spaced to 120 degrees apart.
this method of workholding provides a number of advantages :
1. counteracting rotating in the chuck due to agressive milling
2. stock preparation of dovetails can be preformed on a 3 axis mill
3. less stock is needed when compared to other methods.
4. part can be rough machined - stress relieved in a heat treatment process and go back for final machining.
5. part can be transfered to the subspindle automatically when compared to gripping the stock with a 5 axis vise and in case of needed part transfer - manual unclamping must be done and cause serious setbacks. (a solution Ive considered but abandoned eventually.)

I guess there might not be anything new here for some of you, but I havn't seen such a solution online and I would love to hear/see your thoughts and workholding solutions.

Pic 4 scares the Shiite out of me!



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Think Snow Eh!
Ox

MULTUSB200 said:

and had a few parts fly out of the chuck.

Click to expand...

Well, like Ox said...

IME, not much to worry about. Shop I retired from had a few parts we ran like that for ~20 years. Don't recall ever having any holding issues. They were 17-4 H900 or H1100 instead of aluminum though and about 6" long and 2"-3" diameters.

someone said you put an engineer in a hole and give him a shovel he will end up trying to make a ladder out of it. There was NO other way to make this part? You yourself said you had no lathe experience. Post up a print and see what others think. Not saying this is not a good solution, but how big of a problem was it? Did you somehow create the problem by viewing how to create the part a different way, not necessarily wrong.

Great solution, thanks for sharing!! Will be using they when the next suitable job arrives

We just use a raptor fixture if there is no other way. I've spun 10 x 9 x4" thick 6061 parts with a 1.5" eccentric throw as a prep for a tailstock operation from one of those and I've still got all my fingers and toes so far.

Looks like a great solution to me.

Ox said:

Pic 4 scares the Shiite out of me!



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Think Snow Eh!
Ox

Click to expand...

It's probably pretty safe.

I've run some big parts in the lathes (long and too big for the steady) by dovetailing the part and soft jaws. It's daunting for sure, but I've never had an issue with it.