different Surefire body alloys?

[lemlux]

I've used a 3/4" step drill to bore out numerous Surefire 2*123, 3*123 and A19 extenders for use with 18mm cells. In each case, the shavings came out in roughly 1/8" to 1/4" lengths.

Yesterday, I bored out my 4*123 Surefire 12pm body which I bought about 7 or 8 years ago used. Surprisingly, all the shavings came out continuous lengths of well over 1" and wrapped around my 6" drill extender. I had to repeatedly remove the shavings with pliers.

What does the shaving difference tell you metallurgists out there? I'm certainly curious.

 

[65535]

Not a pro here, but that would generally indicate a more ductile/soft alloy. It's also possible that a difference in thickness caused the chip to no break as opposed to modern bodies to break up.

 

[mossyoak]

were you using the same drill bit? some have a chip breaker built into the cutting face to break up chips and some dont, also if its been resharpened since you did the first boring you could have effected its chip breaking attributes.

 

[gadget_lover]

I have seen similar strings chips when working on extruded flashlight bodies. I also hit it when trying to enlarge the bore of an aluminium rod of unknown origin.

Daniel

 

[precisionworks]

Aluminum alloys are not easily predictable ... most produce long, stringy chips that wrap around any nearby object (like a spinning chuck). Try peck drilling where the drill is advanced a short distance (like 1/8") and then withdrawn, which will usually cause the chip to break.

I sometimes manual feed the carriage, but many CNC lathe operators will "peck feed" the carriage (advance a short distance, dwell in that position for a few tenths of a second, advance again, dwell again, etc.)

 

[lemlux]

I used the same inexpensive, unsharpened step drill applying some chain oil frequently as a cutting oil substitute each time.

The titanium coating on the 3/4" step edge does seem to have worn-off, however. This coating wear showed several borings before the 12pm body, so I don't think it's the cause.

With each drill insertion I never went more than 3/8", and usually less as I backed the drill out to extract the shavings.

 

[mossyoak]

Peck about 1/16th in each peck and you shouldn't have problems