Hello Forum Members,
Looking for advice for future reference. I recently drilled a 3/4 inch (19mm) hole through a 10mm modushop aluminum front panel. Unfortunately the bit chattered terribly giving me an adequate but not perfect hole. (Rough edges).
I am assuming my main mistake was not having my work clamped down tightly. The trailing edge of my panel rested against the pedestal of the drill press so the work couldn't catch and spin, but the bit did chatter.
I used a decent drill press, decent (and expensive) cobalt bit, and aluminum cutting fluid. I had previously drilled a 3/8 inch pilot hole.
Next time I will clamp my work. Any other pointers? Thank you for helping out a construction novice.
Looking for advice for future reference. I recently drilled a 3/4 inch (19mm) hole through a 10mm modushop aluminum front panel. Unfortunately the bit chattered terribly giving me an adequate but not perfect hole. (Rough edges).
I am assuming my main mistake was not having my work clamped down tightly. The trailing edge of my panel rested against the pedestal of the drill press so the work couldn't catch and spin, but the bit did chatter.
I used a decent drill press, decent (and expensive) cobalt bit, and aluminum cutting fluid. I had previously drilled a 3/8 inch pilot hole.
Next time I will clamp my work. Any other pointers? Thank you for helping out a construction novice.
The speed of the drill is also important. The larger the bit, the lower the RPM. There are equations and calculators that will give hard numbers, google "drill speeds and feeds" if interested. If your drill press is set up for woodworking (most are) I'd recommend setting it to the lowest speed for a bit that large when drilling any kind of metal.
What I have done is to use a little isopropyl alcohol (IPA) as a lubricant while drilling, and the chatter stopped and I got a very cleanly cut hole. I put the IPA in a squirt bottle and just squirt a bit onto the work as the drilling progresses. A very important step is to firmly clamp the work piece down on the drill press. Don't just manually hold onto the piece while drilling it. Cutting oil could also be used, but I prefer the IPA because it is easy to clean; it just evaporates away, whereas with the oil, it needs to be cleaned off the work piece. Another thing to note is that rubbing alcohol may not work well because the alcohol is diluted with water. I use the 100% alcohol type. I have not tried rubbing alcohol, though. It might work.
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When drilling thicker material with a step bit, I will go as deep as the bit allows for the size given, and then flip the piece being drill and see how deep the bit allows again. If there is leftover in the center of the material thickness, you may be able to remove it with a conventional bit, with the workpiece clamped of course.
1 - Clamp the material.
2 - Slow speed for large diameter drills.
3 - Progressively larger drills mean the drill has no centre location so can be more prone to chatter.
If you are enlarging a previous drilled hole, even try turning the chuck by hand when starting the cut until the larger drill has got proper location in the hole.
4 - a large drill in a small drill press that probably doesn't have a slow enough speed will need care to avoid chatter. Sometimes a hand held drill with speed trigger can do a decent job, especially if equipped with a gearbox (always use a vice).
2 - Slow speed for large diameter drills.
3 - Progressively larger drills mean the drill has no centre location so can be more prone to chatter.
If you are enlarging a previous drilled hole, even try turning the chuck by hand when starting the cut until the larger drill has got proper location in the hole.
4 - a large drill in a small drill press that probably doesn't have a slow enough speed will need care to avoid chatter. Sometimes a hand held drill with speed trigger can do a decent job, especially if equipped with a gearbox (always use a vice).
I've used centre drills and a counter sink bit to good effect on thin alloy. A two flute drill will always have a tendency to drill slightly triangular holes. You can sharpen drills for thin sheet, one way is to make them more "pointy", not really much improvement, or more like a wood bit, MUCH better. Use could use a taper reamer to round a lumpy hole, and to get it closer to the right size. Then of course, you could spend lots of money and trepan them on a milldrill.
That.
Stepped bits are incredible useful but not on 10mm thick aluminum, no way.
Most important is firm clamping of the work piece and using a well maintained drill press, proper mounted mandrel, etc.
Sometimes mandrel has a little "play" and that is multiplied at the drill tip.
Proper lubrication is the cherry on the cake, I use kerosene/petrol (storm lamp fuel); it is "oily" enough to lubricate but is easy to wipe out and does not leave oily residue behind.
A popular lubricant to work with aluminum, for drilling/punching/shearing is, believe it or not, pig grease.
Works very well.
Aluminum is infamous for galling, which is a nightmare, it even breaks tools, go figure.
https://clintonaluminum.com/galling-of-aluminum-and-stainless-steel/
Stepped bits are incredible useful but not on 10mm thick aluminum, no way.
Most important is firm clamping of the work piece and using a well maintained drill press, proper mounted mandrel, etc.
Sometimes mandrel has a little "play" and that is multiplied at the drill tip.
Proper lubrication is the cherry on the cake, I use kerosene/petrol (storm lamp fuel); it is "oily" enough to lubricate but is easy to wipe out and does not leave oily residue behind.
A popular lubricant to work with aluminum, for drilling/punching/shearing is, believe it or not, pig grease.
Works very well.
Aluminum is infamous for galling, which is a nightmare, it even breaks tools, go figure.
https://clintonaluminum.com/galling-of-aluminum-and-stainless-steel/
A step bit needs a little more to grab on to than just a mark from a center punch. I have a stock of Black & Decker "bullet" bits that come in useful for making holes in sheet metal, as they have a brad tip that centers properly on the punch - they also excise a neat hole without much of a burr.. a 1/8" hole from a bullet bit will give the step drill something it can properly engage.
A stout drill bit should be stiff enough to avoid chatter with everything clamped as it should be. However many wide drill bits are blacksmith style (thin shank that widens for the cutting end) - these are less well behaved.
Definitely a drill press and proper clamping is the way to go.
Progressively larger holes is a thing, but large steps, perhaps 4mm pilot hole then direct to 19mm. A 4mm bit is easier to start on a punch mark than a 19mm(!).
When you say aluminium do you mean pure aluminium or aluminium alloy? Pure is horrible to work with and always leaves large burrs. Most aluminium alloys are free-machining and easy, but can sometimes stick to the tip of the bit if your feed rate is too timid, especially with a worn bit. If the swarf comes off the bit in long continuous twists you are probably feeding OK.
Definitely a drill press and proper clamping is the way to go.
Progressively larger holes is a thing, but large steps, perhaps 4mm pilot hole then direct to 19mm. A 4mm bit is easier to start on a punch mark than a 19mm(!).
When you say aluminium do you mean pure aluminium or aluminium alloy? Pure is horrible to work with and always leaves large burrs. Most aluminium alloys are free-machining and easy, but can sometimes stick to the tip of the bit if your feed rate is too timid, especially with a worn bit. If the swarf comes off the bit in long continuous twists you are probably feeding OK.