Menu
What's new

Too much torque?

It's long so that allows more ability to twist and bend.

Also depending on the hardness and the material, like HSS or Cobalt. If it's HSS it may be a case harden with a softer more ductile core. Sure I can see that happening. If it was Cobalt maybe not.

Deep hole drilling with a small diameter needs a LOT of pecking. In CNC industrial machines I would peck every 50 or 80 thousandths.

In a production deep hole application I once twisted a solid carbide reamer.
I do have proof of that.
 
Heh. So John, from Bridge City Tool had a blog post about how a lot of the cheap drill bits were only hardened in the sizes that were used and the others were not-quite-pot-metal.

Interestingly that blog post somehow disappeared after Bridge City was bought out by an overseas manufacturer (even though many others in the same class are still up). Entirely coincidence I'm sure. Regardless we have the archives...

$5 for a 1/8" Twist Drill? Only in America... - John's Blog

web.archive.org

I've had .. I think 2 drill bits unwind on me like that, both from cheap sets. I've also had a couple snap like twigs under only nominal load from similar collections.

That one looks longer than I've have expected to see this sort of behavior in though, specialty bits are often
 
It all depends on the steel and the alloy in the steel. It's like a cake mix, lots of ingredients. Good steel that is hardenable is more expensive than plain low end steel with little to no alloying agents. Even steel like 1144 can be hardened. It gets case hardened to a depth of about .030 Can't really get it much deeper than that. On the surface it would pass a file test, but you can drill a hole through it as it is soft in the middle. A good tool steel like O1, A2 or other steels can be thru hardened to achieve a hardness of Rc55-58 or even up to Rc61 or so, but it would not be practical at Rc61. Steels like D2 can be brought up to Rc62 but it is expensive and would be difficult to sharpen.
 
You must log in or register to reply here.
Top