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head stock taper

Joined
Jun 10, 2017
can anybody tell what size taper fits south bend 10 head stock with 1.7/8" x 8 tpi regular (small hole 1")

many thanks
 
i can only advise you to measure it.

I have conflicting info...one source says MT4 while another says the taper of MT3 but with a larger gage line than MT3 ( as is the case with the large bore 10L)... It may help to state the vintage of your machine.

Anyone?
 
If it's MT4 it is a short MT4 - a stock MT4 center sticks out too far. Miller Machine sells replicated adapters - like what SB supplied - that lets an MT3 work in the headstock.
 
Its easy enough to measure. All you need is a 1" travel indicator on the bed and a test indicator that is either small enough to reach inside the bore 1", or with a long enough tip to get it done.

Mark 4 places around the inside of the bore, basically 90 degrees apart, just to rule out any problems with measurement or the bore itself. Measure the change in the test indicator when moving 1" inward from the tailstock end of the bore. Do that 3 times for each position, average it all out and you now have taper in thousanths per inch. Multiply by 12 to get taper in thou per foot if needed. Compare that and the ID of the big end of the spindle taper to the chart of standard taper dimensions and that will tell you what you have.

If you want to make your own, frankly the taper measurements don't matter. Just adjust the compound until you can run it in and out of the spindle bore without a test indicator moving off zero and thats the taper angle. You'd want to heat treat it after making it so it doesn't just mush on you.

I did all that with my 10L, then found the official number and it confirmed my measurements. Then I both forgot the answer and lost the measurements so thats about as far as all that went. I know its not standard though. Basically the diameter is MT5, but I think the taper actually matches MT3. I was going to turn myself a proper headstock center but never got to it. If I need to run between centers I just chuck something in the 3 jaw, cut a 60 degree taper on it with the compound and use that as my center. Its not accurate once you pull the pointy bit out of the chuck but its not any effort to re-cut it as needed.
 








 
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