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madman
01-11-2010, 01:53 PM
Yup ON tOPIC for once. I am making some (10) tapered grinding wheel holders for a old cincinatti drill sharpener . I was wondering if I should heat treat these parts then cut the taper or machine within .010 and cut taper after heat treat,. Taper has to be very accurate. Also what material would give good wearabilirty and not deform under heat treating. ??This part has one left hand thread and also one right hand thread, Interesting machining project indeed for myself. Just thinking about order of operations so i have no distortion from heat treat.

mechanicalmagic
01-11-2010, 02:08 PM
My choice would be pre hard 4140. It's still machinable at RC 30-35, and should not warp IF you take material off equally around the rod.
http://www.mcmaster.com/#catalog/115/3609/=5bwoim
middle of the page.

Machinist-Guide
01-11-2010, 02:10 PM
A-2 and S-7 holds shape and size very well if done in a furnace with tool wrap
How long are the shaft's as this would determine the process.

Machinist-Guide
01-11-2010, 02:12 PM
My choice would be pre hard 4140. It's still machinable at RC 30-35, and should not warp IF you take material off equally around the rod.
http://www.mcmaster.com/#catalog/115/3609/=5bwoim
middle of the page.

This would be a good thing to do. You won't have to heat treat.

madman
01-11-2010, 06:48 PM
Doesnt that stuff suck to thread and turn> I recall machuining some and was surprised at how tough it was. ? How bout A2 material?? Thanx guys> I am mainly concerned about warpage afecting my taper fit?

mechanicalmagic
01-11-2010, 07:17 PM
"4140 in the hardened and tempered as supplied condition has good to very good machinability and operations such as sawing, turning, drilling, broaching, hobbing, milling and tapping can be carried out satisfactoraly using machine manufacturers recommendations for suitable tool type - feeds and speeds."

from
http://www.interlloy.com.au/data_sheets/hollow_bar/4140.html

YMMV

smalltime
01-11-2010, 07:49 PM
Our shop has dozens of wheels on arbors like this. If you are like me, you will be switching these out a bunch.
If so, then I would go to the trouble of hardening them and grinding the taper afterwards. If left soft, they will get pitted from the exchanges.
The A2 or S7 drawn to around 57-55 r.c. will hold the tight threads close enough. Although I would not harden the nuts you will have to make.

As you prepare to grind the arbors, you should probably grind a slave to "ring" in the taper BEFORE grinding the real deal. A little royal blue or even a sharpy would tell you if your angle is close.
And keep them cool:D