Drilling an 8mm aluminum panel for recessed knob/jack.

So I'm looking at another project and thinking of buying a chassis that has some holes pre-drilled - IEC, Volume, Power. The only missing holes are RCA and headphone jack. RCA is easy. 4mm back panels. Since this chassis has a 8mm front panel and my headphone jack won't go that deep I need to make the jack recessed. The plan is to first drill a hole that works for the size of the jack 8mm deep using my drill press. Then use a separate bit that is larger and go about 4mm deep. What type of bit is used to do the 2nd hole? My guess is a reamer. Or is there a better bit for this?



Thanks,
Mull3t
 
I drill thick panels from the rear.
Drill the clearance for the jack first then with your drill press using a drill large enough to clear the jack chassis, measure and place a stop at 5mm in. That will give you 3mm at the centre and depending on the flute angle around 4mm on the outside.
Offer the jack to it and check for thickness.
If you have one, use a milling bit of the required size to finish off.

You can always remove more but cannot put any back.
 

avtech

Member
2017-12-12 4:04 am
South Oz
So I'm looking at another project and thinking of buying a chassis that has some holes pre-drilled - IEC, Volume, Power. The only missing holes are RCA and headphone jack. RCA is easy. 4mm back panels. Since this chassis has a 8mm front panel and my headphone jack won't go that deep I need to make the jack recessed. The plan is to first drill a hole that works for the size of the jack 8mm deep using my drill press. Then use a separate bit that is larger and go about 4mm deep. What type of bit is used to do the 2nd hole? My guess is a reamer. Or is there a better bit for this?

A reamer is used to clear an already drilled hole to a particular dimension.

I usually use a step drill for chassis holes because once it drills down to the desired diameter, you can continue to bore out the next diameter or two to create a suitable recess.

Another method I use is as Jon says; I drill a small pilot hole in the correct location all the way through the plate. Then drill the recess (larger) diameter on the front to a suitable depth. Once the test fit looks good (allowing for a tool if required), I flip the panel and back drill with the smaller diameter to fit the threaded part of the jack.
 
I use a flat bit intended for wood to fit RCA sockets into thick aly panels. Drill a hole just big enough for the tapered point to fit into just before the flat shoulder reaches the metal. It will enlarge the centre hole as it goes. Sometimes I have to grind off the outer points of the flat part, depending on style of bit. They are so cheap I don't mind sacrificing a bit for a set of holes. The full size centre hole is drilled afterwards.
 

phase

Member
2004-10-04 11:59 pm
The forstner bit that is intended for wood, not aluminum, will work, but you’ll be wise to make a guide clamped up with your panel made from mdf or something dense like that. Also to use lots of cutting fluid, maybe practice on something else first, or in a spot that won’t be noticed later to get the speed right.
 
Having the right, quality tool is always preferable. 'Buy once, cry once'.

A spade bit can get you out of a bind if you are desperate, but the length of them often makes them produce irregular holes.

My first choice would be a counterbore as Dave says, (actually CNC is my first choice) then step drill, moving onto to a disposable forstener bit depending on the urgency and level of finish required.
 

Dave Zan

Member
2010-11-21 7:12 am
Counterbore bits are usually countersink,
This is completely incorrect.
800px-Countersunk_and_counterbored_holes_cross-section.png


Best wishes
David
 
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phase

Member
2004-10-04 11:59 pm
And you would need a small guide hole to keep the Forstner bit centred.

That would be the (guide) mdf portion of the setup. Sorry if that wasn’t clear enough.
Forstner bits have tapered pilots, so not much to use as a guide there, so the outside of the cutter is where you would do that.

All this discussion about using wood cutting tools on metal is taking me back to my youth.
 
One technique I have seen used by a constructor on this site is to take a Neutrik RCA jack in a D-type shell (look on Ebay for Neutrik NF2D-2 RCA Jack D-Series), remove the RCA jack part, and then use the D shell to mount other stuff like volume controls and headphone sockets etc. You can get them with black and silver shells.

Saves all that drilling etc. and looks cool, particularly if you use them for other stuff on the same panel.

Cheers

Mike
 
The key with using a stepped bit would be having enough depth to the size your looking for. Let's say each step is only 3mm (this may not be the case) and you need 4mm then it doesn't seem it'd be right for the job. Then it seems like a forstner would work in a pinch. Only issue with a forstner is it's technically not meant for the job and who wants to waste $20 on something like this...

Fisch Wave Cutter Forstner Bit

I have a stepped bit. I'll take a look at what it can do on some scrap aluminum and if it doesn't live up to the hype, I'll try a forstner.