View Full Version : Friction Drilling

john hobdeclipe
07-15-2008, 10:46 PM
Forgive me if these have been posted here before. I blundered into this over on the sculpture.net board and thought it was interesting.



Personally, I don't think it's a big deal...I've been doing it that way for years and years :D

07-15-2008, 11:05 PM
I was drilling tool-steel, HSS power hack-saw blades and files etc. just like that with "Stellite" bits over 50 years ago. It needs a good solid mill/drill to do the job at high sped with high pressure. It just rubs, get hot and then feel it starting to "go" - just keep going.

We ground the tips to a triangular pyramid with (as I recall) about a 60>90 degree included angle. Each face had a groove ground into it so as to leave a narrow "land" on each side of each face.

Friction drilling and cutting/forming threads on "self-tapping screws etc. has been used on sheet metal - up to say 1/8" - for siding, roofing, purlins and by erectors and Electricians and Plumbers etc. for many years.

07-15-2008, 11:13 PM
Interesting, I've seen the final results before, (did a LOT of sheet metal work) but had assumed that a sleeve had been inserted, now I know what they are.


Brian H.
07-15-2008, 11:43 PM
Yup, definitely an interesting (and useful!) process. I talked with the folks from Flowdrill, Inc. at the 2006 IMTS show (an EXCELLENT show, btw) for a while - IIRC, their drill points are slightly lobed with 4 facets, available in fluteless or fluted tip (to aid in piercing the material) versions, and are made from solid carbide. They use a special holder with a MT2 or MT3 shank, integrated fan, and an ER-25 or -32 collet to hold the drills.

They said that the extruded "bushing", when form tapped, had equal or greater pull-out strength than a welded-on nut, though there are presumably variations due to differing material strengths.

Some pics of a sample they gave me: