+- MetalworkingFun Forum (http://www.metalworkingfun.com)
+-- Forum: Machining (http://www.metalworkingfun.com/forum-5.html)
+--- Forum: General Metalworking Discussion (http://www.metalworkingfun.com/forum-6.html)
+--- Thread: 4142 Pre-hard? (/thread-733.html)
Pages:
1
2
RE: 4142 Pre-hard? - Sunset Machine - 08-18-2012
1/4" tap is probably the smallest I can sharpen on a grinder, but that little #8 would appreciate a lick from a stone. Try it sometime, experiment a bit, develop a new skill. Just lay the tap flute on the corner of a stone, tip the back end up a bit and rub. Repeat for each flute until the shiny tips (the dull cutting edges) are gone or reduced in size.
How much material do you suppose there is in the upper 50% of a teeny thread like that? If I may, a paraphrased quote from Machinery's Handbook:
"Tests have shown that any increase over 60% does not significantly increase thread strength, in many cases 55% to 60% is satisfactory......if the engagement length is 1-1/2 times the diameter, then 50% - 55% is satisfactory."
Your "nut" is half-hard steel, the screw intended for soft steel, no? 50% should be fine if you do careful work. But it's a gun. I don't do guns. If you'd have mentioned that in your first post I'd have kept my yap shut - my apologies, I was responding to the tapping question.
RE: 4142 Pre-hard? - stevec - 08-18-2012
Sunset, I don't do guns either but I have "touched up" taps to my satisfaction, still, I don't think I'd try a #8 or smaller.
Also, even if you have one of those "today" model dentist drills you can't turn a carbon steel tap into an HSS one, Just my take.
How expensive can an 8-40 HSS tap be? (once you find it).
RE: 4142 Pre-hard? - Highpower - 08-18-2012
Well it looks like it was all much ado about nothing.
The "half hard" steel cut like butter, even with the carbon steel tap.
Having never worked with this alloy before, all this time I thought I was going to have a fight on my hands.
Another lesson learned.