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Posted: Thu May 30, 2013 5:07 pm
by jmsolt
Wrong screws used. Should be self-theading fine thread! I stand corrected!
Posted: Thu May 30, 2013 8:59 pm
by shipwright
Just a thought and too late for it now but I think I'd be considering some silicon adhesive both on the interface of the parts and the threads of the screws.
Paul M
Posted: Fri May 31, 2013 2:47 pm
by frank81
jmsolt wrote:Wrong screws used. Should be self-tapping fine thread!
Fine thread is undesireable for self-tapping. You need gaps in your pitch for the tapping process.
Posted: Fri May 31, 2013 8:41 pm
by JPG
frank81 wrote:Fine thread is undesireable for self-tapping. You need gaps in your pitch for the tapping process.
I think self 'threading' is a more correct description. Self tapping screws create standard machine screw threads and are usually used with a metal 'target'.
I agree that a finer self threading pitch is more suitable for plastic. Chuck's pix looked like sheet metal screws(course pitch with deep threads).
Posted: Sat Jun 01, 2013 1:36 am
by charlese
JPG40504 wrote:I think self 'threading' is a more correct description. Self tapping screws create standard machine screw threads and are usually used with a metal 'target'.
I agree that a finer self threading pitch is more suitable for plastic. Chuck's pix looked like sheet metal screws(course pitch with deep threads).
Red is right-on here! The screws furnished by Shopsmith were indeed self threading sheet metal screws. In fact the new unit came with new screws inserted into the plastic posts clear up to their shoulders. Of course when the unit was installed on to the headstock, the screws come a bit short of that depth because of the thickness of the headstock.
Once again, I'll say I had to ream the old threads from the metal headstock (see post #6) holes to allow the screws to start perfectly centered into the plastic.