drilling/tapping aluminum

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I supposed for now I should try not to get too carried away with buying equipment as I need to drill one type of a hole, and make a thread in it. There'll be about 30 of those holes throughout my chassis .. Its too easy to get caught up in the moment (for me at least!) and start buying stuff.
 
Elizard:

The best tools in the world will be wasted if you don't drill the holes in the right locations.

Therefore I would recommend also getting a punch (so that you can accurately mark the location of each hole before you drill it), as well as some kind of adjustable clamp so that the chassis which you are working on doesn't move or slip during the drilling operation.

When drilling each hole, at first don't spin the drill bit, but lower the chuck so that you are sure that the drill bit is _exactly_ where you want it on the work-piece - good lighting being an asset. Then and only then should you drill.

I also use a wire brush to remove the metal shavings from the drill bit before moving to the next hole. It is harder to pinpoint the next drilling location if the tip of the drill bit is partly obscured by ribbons of aluminum.

Repeat the procedure for each hole.

Tapping threads isn't such a big deal once suitable pilot holes have been drilled. But in addition to lubrication, again you will get cleaner threads if, between holes, you remove any metal shavings from the tapping bit with a wire brush.

hth, jonathan carr
 
diyAudio Member
Joined 2003
A few drill speeds for bits,

3mm (1/8) 3000-3500rpm
6mm 1400-1600rpm
8mm 1000-1200rpm
10mm 800-1000rpm

Ok a general rule to follow here is the smaller the bit the faster we go, this does also have to do with feed rate.

For tapping holes, if you know how to tap a hole correctly you should never break a tap. The way i was told when i was doing my engineering course is to go 1.5 full turn's in, then back half a turn. Doing this will clear out the cutting burrs from the tap and stop the tap from jamming up resulting in a break. However now days we have taps that we can just run through with a drill non stop and the tap wont jam up. These are the more exspensive taps that we can buy, but they can also snap depending on what we are tapping due to clogging up.

For aluminium we shouldnt have a problem with breaking a tap providing its well lubricated and you keep the tap clean. Work the tap through the alloy going 2.5 turns in, then 1 turn out. This will clean the cutting burrs out of the tap and give us a very nicley cut thread. Going too fast with a tap will break the threads off instead of cutting them. The best way to tap a hole is by doing it by hand and not with a cordless drill, however trying to tap a 3inch hole can only be done by machine, obviously a lathe or a heavy drill press, and will require a tap that can be run strait through.

The best lubricant that ive used is called teflex, its green and has teflon added into it for a super lubricant on the tap.
For aluminium soap is a way to go if your worried about staining, dishwashing liquid, chain oil, the bacon fat, sump oil are all good, but do it by hand or you will break your tap and threads using a normal drill.

I dont see any problem with the walmart taps, they should be fine for this work, just take your time and keep the tap clean.


Trev
 
diyAudio Member
Joined 2003
The best tools in the world will be wasted if you don't drill the holes in the right locations.

LOL very true.

Therefore I would recommend also getting a punch (so that you can accurately mark the location of each hole before you drill it), as well as some kind of adjustable clamp so that the chassis which you are working on doesn't move or slip during the drilling operation.

You could also drill a fine pilot hole after you have punched the material hole mark, this will result in a more acurate redrill with a bigger bit. It will also drill faster and the drill bit wont run off.

i checked home depot/rona/canadian tire for the screws

Elizard, are we using screws or bolts here? cos if just using screws you can buy self tapping screws that tap the hole as they screw in, eliminating the need for any taps.

Trev
 
I'be been using lately, but only for M4 or higher, a three bit set that I got from spares at my company. It's a 3 tapping bits set , one does the first sweep, the next goes deeper in the thread and the 3rd one is the standard M4 bit that sees a very easy job. This is an standard in my workshop.
For lubricant I use olive oil available from my kitchen, and if you manage to do it carefully, the hand drill it's very helpful for quick threading. You only have to take care of not putting pressure.
 
diyAudio Member
Joined 2003
I'be been using lately, but only for M4 or higher, a three bit set that I got from spares at my company. It's a 3 tapping bits set , one does the first sweep, the next goes deeper in the thread and the 3rd one is the standard M4 bit that sees a very easy job.

Heya Raka, thats a very similar type of system i used to use on m24 holes but with a drill press. IMO they are the best type to get but arent very cheap.

Trev
 
Taps in sets of three?

Whenever I've bought taps (I've worked with 9BA, and 3mm-dia/0.5mm-pitch taps), I've been given a set of three taps. I have no formal training in the use of taps, and I've broken quite a few taps (specially the 9BA size, which has an external dia of 2mm) while teaching myself to tap. Angshu (another member of this forum) taught me about lubrication and tapping technique, after which I've never broken any. :)

In the set that I get here, the three taps are different... they need to be used in a specific sequence, where the first tap cuts the first groove down the full length of the hole, and the subsequent taps make the threads deeper and sharper.

When I saw the online catalogues you guys are referring to, they seem to talk of a price per tap. Does this mean that I need to buy three taps from them to get the set that I've always seen in India? And on page 35 of the Enco catalog, I saw something called "Pitch Dia Limit", with values of "D3" and "D4", etc. What's this pitch diameter limit?

What drill and tap sizes do you use for bolting TO-220 transistors and chips with insulating shoulder washers? I use the 9BA size for such situations, and I'd really like to use something of a larger diameter, to avoid tap breakage. And this British size is a bit difficult to find when looking for taps.

PS: It appears that Raka and Ace_3000_1 have put in their posts while I was writing mine. :) Well, my doubt still stands... doesn't one always need taps in sets of three?
 
Candle Wax for tapping

A simple and CHEAP material for tap lubrication in aluminum or Copper is candle wax. There is more than enough heat at the cutting edges to melt the wax for lubrication. The remaining unmelted hard wax will act as a carrier for the chips and help keep them out of the cutting area. This works for hand as well as drill tapping. I also use the taps from home depot. I havn't broke many in my work only when I set the drill down:dead:
For drilling and routing simple oil works fine but Tap Magic for aluminum is best. The key here is keeping the cutting edges cool enough not to cause local melting (galling). For that matter water would work ok if it wouldn't corrode my tools.

Scott
 
well i ordered the srews and tapmagic (a 6oz bottle i think, the smallest they had, should be more than enough) through mcmaster .. the rest (i.e. the taps) i'm getting locally ..
i went to rona/revy today .. the only place that actually had the tap i needed, it was $7CDN .. but it came with a HSS drill bit, so its all good :)
 
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