What is it?

[mcostello]

Did it mess up the bit?

[armscor 1]

Flattened the tips of both drills.

[Wolfgang]

Flattened the tips of both drills.

Yes, the process removes the sharp corners of the drill bit, but the process still works.

I just tried it, using a 1/4" dia. commercial stellite drill and an O-1 tool steel plate hardened to Rc 60 - 62. Unfortunately 1000 rpm is too low, I put my drill press on top speed which is 2100rpm, and I really had to bear down on the feed lever to get the process to start. Basically the drill heats up the steel and anneals it, with the softened metal getting pushed out of the way.

My son recorded it and we just posted it on YouTube. Look for BasementEngineer (one word) and search for the latest video, Dec. 29., 2018. Note that the 1/3 hp drill press motor stalls and I had to ease up on the feed. I think that 1/2 hp may be the minimum required for 1/4" dia. drill. Anything larger may best be done in the milling machine. w

[mcostello]

WOW!

[spro]

I think we may be getting into "friction sawing" or friction drilling. Blades or tools with stellite or newer, arrive with proper angles but they introduce a heat factor at higher rpms. The tips aren't going anywhere but it is so hot that the base metal relents. They cant be used as regular drill bits or impact but I can see a point between, where the metal is melting or giving out, in face of pressure.

[Harold_V]

What spro said. Fact is, you can do it with a conventional DoAll saw with a common carbon steel blade. I've done it on a few occasions, although long ago. A file can be sawed in half with no effort. The blade can be operated in any position (teeth upside down or right side up, makes no difference) and it must travel quite fast. The common DoAll doesn't have the torque to friction saw continually, at least not the older models I've used, but they sell friction saws that can do so. Blade speed can be up to 15,000 fpm, but it will work much slower, as low as 1,000 fpm as I recall. The blade is useless for anything else, as it gets well rounded. Sort of defies logic, but, man, does it work!

A comment about Stellite. One of the alloys in that family is tougher at 1,500°F than at ambient temperature. Strange stuff. Had it not been for the development of tungsten carbide, we'd be using it extensively today.

H

[rrnut-2]

We had some big Tannewitz bandsaws (25hp drive motors) that did friction cutting. Scary machines, I wouldn't use them. One of the few machines that you could get hurt on by doing nothing wrong.

Jim B

[armscor 1]

Harold inspired me to give my 1/2" Stellite drill another chance, ran the DP max speed, 2400 rpm, it was like fireworks on NYE perfectly round hole and right on size. once the heat built up it was like cutting cheese.The Drill itself is slightly discolored but is ready for another task.

[neanderman]

Wow! That's amazing.

[JackF]

A friend of mine used to work for Alaska Copper in Seattle and they used their Duall? band saw to friction cut stainless steel. They used the back side of the saw blade at top speed. I was told it cut through like butter.

[spro]

First off, Mr. Wolfgang mentioned this process earlier. There is another thing which sticks in my brain for some reason. In the deep dark cold of WWII when they had to move entire factories there was more than I can say here. It was production by any means and people were getting shot if they couldn't complete the cutting of thick steel quickly. They ramped up the speed to friction cutting and it worked.

[spro]

Hi JackF. This input contributes very much. It is keen part of the discussion.