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Internal threading. 35mm x 1.5 on a 7x10
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Brass_Machine:
So as my thread title says, I have to do some 35mm x1.5 threading. Priced out the tap... cheapest i found so far is about $120USD! Not bad, but not good either. Now, I have never threaded on my lathe... So is it possible to cut a 35MM X 1.5 on an imperial 7x10 lathe? Should I just cough the money up for the tap?

Eric
winklmj:
Should be doable but with some errors if you don't have a metric leadscrew.

http://littlemachineshop.com/Reference/change_gears.php?func=submit&soughtTPI=1.5&threadUnits=mm&leadScrewPitch=16&addGears=

Brass_Machine:
That's a good link. Didn't know they had that on their site. I just down loaded a small thread calculator from HERE

Getting somewhere now. Looks like I gotta bore out to 33.5MM...
spuddevans:
As said, it should be doable, obviously there will be a margin of error, but assuming that you are not threading to a very great depth the error should be negligable.

Marv Klotz has a calc program for change gears and it gives you the errors as well, might be worth a look.


Tim
andyf:

--- Quote from: Brass_Machine on November 05, 2010, 03:01:47 PM ---Getting somewhere now. Looks like I gotta bore out to 33.5MM...

--- End quote ---

That's right, Eric. For the usual metric thread forms, the tap drill (or bore) is easily calculated. Simply subtract the pitch from the major diameter. So 35 - 1.5 = 33.5mm.

Andy
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