Saturday, January 07, 2012

Aluminum (or aluminium, if you prefer) is a sticky metal.

This splash is what's left after a plunge up to 7/16ths with a stepped bit (or unibit, if you prefer).

The bit itself also suffered some adhesion issues, I had to pick metal from between the flutes between each pass. My goal here was to overbore a hole for the 3/8" shaft of the chassis punch, which allowed for a little shifting room to align the punch independent of actual drilled hole (my press having a few issues that I may get around to addressing).

Enter into the equation the chassis punch. Photo sequence here is going to sidetrack into another hole making session (as evidenced by the existence of steel in lieu of aluminium).

During that previous punching session, I needed to punch a one inch hole for an admittedly large pilot light assembly I am installing on a slave amplifier build. So, naturally I grab the punch set labelled 1" and move on. Sadly, it would appear as if my "vintage" chassis punch set of Japanese manufacture was prescribed to the metric inch, as my panel mount lamp would not fit the hole, which measured out 2% shy of an actual inch.

Thankfully my hand operated filing operation didn't need to ream out an actual inch.

The process was a pain in the ass none the less. This is also the time to point out that sometimes alignment on center of parts is inferior to unified distance of space between finished assemblies. For the record, that fuse assembly has been usurped by a superior one, and I do acknowledge there is a trace of rust on that power switch - electrical function will be assured prior to implementation.

Back to the 1U XLR breakout connector panel for the Autogram AC-8 (amongst other things), as it turns out, the snug inch hole is roomy for Switchcraft panel mount female XLR jacks (I have taken to measuring everything prior to commiting work). There is, in fact, enough slop to align the actual parts to compensate for drift that occurred in the punching phase. And so.. was made. Hole explanation from left to right: stereo pair XLR male send, 5 stereo pair female XLR input, one speaker bypass switch to allow capacitor discharge through 22 ohm resistors as opposed to my studio monitors (I live in a manual world). I'll update with a finished shot once it's finished & functioning.


MKULTRA said...

" Sadly, it would appear as if my "vintage" chassis punch set of Japanese manufacture was prescribed to the metric inch. "

“ The strange thing is they make such bloody good cameras." - Group Capt. Lionel Mandrake

Nice work. Using Duraluminum ?

crochambeau said...

I wish it was Duraluminum! I've wondered if the pitted 3/16" plate material I have is Duraluminum, as it exhibits strange corrosion that is atypical of modern aluminum. I think the 1U panel is probably 6061 or a cheaper alloy. This stuff bends pretty easily.

pearshapedhuman said...

I'm surprised how ugly that hole is. Stepped bits work great with die cast aluminum (just a slight burr on the back side). I would expect a larger burr with softer material, but damn. Maybe try different rpms on your drill. Or- a nice sharp reamer...

crochambeau said...

Normal 1/8" twist bit that I used for the fastener holes did the same thing, it's really poor grade material. Nothing a quick pass with a file couldn't fix..

That said, I do hope to avoid this grade of metal in the future.

krivx said...

You were using a cutting fluid?

crochambeau said...

No fluid, just bashed through them dry with my cheap bench top drill press. I'll run a lubricated set-up next time, I do think I have another blank panel from the same source floating around..