Making a Tap Question???

[November X-ray]

I want to make a 1" x 8TPI tap to use on blind holes in hardwood forms to try my hand at metal spinning. My question is since the tap is for wood only, do the flutes need to be deeper or different then one for metal?

[doubleboost]

Hi
I would think a thread that course would cut wood no problem with standard metal flutes
Metal spinning now that sounds interesting
Looking forward to some pictures
John

[TomG]

I would make the flutes with a little positive rake so the teeth cut the wood with a shearing action rather than a scraping action. That should give you a much better finish in wood.

Tom

[November X-ray]

(06-24-2012, 04:19 PM)TomG Wrote: I would make the flutes with a little positive rake so the teeth cut the wood with a shearing action rather than a scraping action. That should give you a much better finish in wood.

Tom

Any suggestions on how best to cut the flutes with a positive rake? I was thinking about using an endmill to make the initial cuts and then swapping to a small ball endmill since that's all I got. Would three flutes be better than four for wood or will that matter much?

Thanks for the replies!

[TomG]

(06-24-2012, 04:19 PM)TomG Wrote: Any suggestions on how best to cut the flutes with a positive rake? I was thinking about using an endmill to make the initial cuts and then swapping to a small ball endmill since that's all I got. Would three flutes be better than four for wood or will that matter much?

Thanks for the replies!

Depending on how small your ball end mill is, you might need more than four flutes for a 1" tap. I would make one flute complete and then see how many would fit around the circumference of the tap. To get positive rake, all you need to do is shift the side of your end mill past center a bit when you cut the flutes.

Here's pic of a tap I made for my Steven's project. It has four flutes, but then it's only a #12. It also has neutral rake.

Tom

[f350ca]

A standard metal tap should work. According to Lee Valley Tools drill to the root dia of the thread for 100% thread rather than the tap drill size. In your case drill .8466 or 27/32 rather than the 7/8 tap drill.