[skiffle]

I drill a lot of 5/16" holes on .058" walled aluminum tubing (6061-T6, 6063-T832, and 6463) - for tubing buttons/telescoping tubing, and thus far have been using the cheap Ryobi drill press from Home Depot (max 3500 rpm). It gets the job done, but the holes are not perfectly round and it takes quite a bit of reaming, deburring, and honing to get everything nice. If I were to use a different machine would the holes be nicer/cleaner and require less finishing work? I was wondering if a more powerful drill press or a milling machine, etc might produce better results, and if so what kind of specs should I be looking at. Thanks!

[hub1987]

Try a step drill bit. I have never used one on tubing, but they do eliminate oblong holes in sheet metal.

[rowbare]

A more rigid setup would help for sure. The choice of drill bit makes a big difference too. Try to find a stub length split point drill. Something like this: 5/16 Screw Machine Length Drill 135 deg split point black finish MariTool, The split point tends to wander less when starting the hole and the shorter drill is stiffer.

bob

[wizard]

You have gotten good suggestions but i might suggest a small CNC implementation to mill out your holes might be a good solution. Another solution might be a purpose built drilling machine such as: USA Hebo. Of course you would have to be drilling lots of holes to invest in a machine like that. It probably would pay to try different tooling, especially off the shelf cutters / drill bits that might help. Think short and stiff.

You may want to consider a DIY solution such as taking a small import lathe and implementing a single axis CNC drive. The idea here is that controlled feeding of a cutter would do orders for the quality of the machining. You could also work with custom cutter designs or even end mills (center cutting). In the end you would end up with something similar to a horizontal drill press / machining center. You could do the same thing on a small vertical mill, but if you do a lot of theses as you imply I suspect a horizontal arrangement would be better. The trick here is to get away from drill bits, at least for the finish cut.

Somebody mentioned Unitbit style cutters, which probably won't work off the shelf but the idea of a single cutting edge may be worth pursuing. Imagine a custom cutter that mounts a small drill bit in the center with an annular cutter following that up. I still believe that controlled feeding would have to be implemented here to keep the quality of the cut high.

If the tubbing you are drilling is consistent ID wise it may be beneficial to work on a fixture that supports the tubbing internally. Obviously this would only work for limited distance. The idea is to back up the tubbing while you drill your holes though it. We commonly do this in wood working to prevent splintering or tear out. In this case the support would have to have a hole in it to match up with the drill bit. That support should prevent some deformation to the tubing as it is drilled and help with shearing off of the aluminum instead of the ragged edge. You may still need to find the optimal cutter even with the support. That may include doing a rough drilling and following up with a reamer. A short reamer by the way because a long one would still have vibration issues. You may find that the works but requires two drill presses.

You could also try implementing a 3 axis CNC machine and running a pocketing routine with a small end mill. This may be a good long term investment but I can't say if the project you are working on can justify it.

Note that a lot of the ideas expressed above require either mew machinery, tooling or both. In the end if the project can't justify investment in new tooling and or machinery you may be stuck with screwing around.

[QC-Machinist]

what do you drill with? You might get away with chucking a .312 endmill 3 flute center cutting at slower rpm (1000-2000) if you have a pretty rigid setup this Will definitely help with walking and finish issues, HSS Will work fine carbide will last a lot longer.

[skiffle]

Thanks everyone for all the help. I currently drill with a short length split point 135 degree bit - I've tried HSS, black oxide, carbide, etc and noticed little difference. This is actually for my business and I drill every day, so a small investment would be worth it but honestly I have very limited experience in this field so do not know what machinery to look at and want to make sure I make a good choice if I do (which is why I'm asking you knowledgeable folks!). Does anyone have any specific machines in mind that I should look at?

[arizonavideo]

A used RF-31 is a great drill press and mills just fine.

They are all over the place used. Dont pay over $600 or so unless it looks just like new.

They look like this.

Grizzly.com

[awerby]

No matter how good a drill bit you use, a hole in a tube like that is going to have ragged edges because the geometry of the bit is not suited to the geometry of the hole. Probably the best approach would be to drill the rough hole and then finish up with an endmill that moves around the edge and takes off a small amount to arrive at the finished dimension. A machine with backlash will give you a hole that's slightly flattened at the quadrant points, so you'd want something pretty tight if you need a hole that's more round. If you want a specific recommendation for a machine, look at the ACT DMC III on my site, under Production.

[wizard]

Thanks everyone for all the help. I currently drill with a short length split point 135 degree bit - I've tried HSS, black oxide, carbide, etc and noticed little difference. This is actually for my business and I drill every day, so a small investment would be worth it but honestly I have very limited experience in this field so do not know what machinery to look at and want to make sure I make a good choice if I do (which is why I'm asking you knowledgeable folks!). Does anyone have any specific machines in mind that I should look at?

I was thinking a custom cutter ground like an electricians panel drilling step drill. That would still leave you with burrs in the inside.

As has been mentioned an end mill would probably do well in a CNC machine. However that means buying a CNC machine.

In the end it comes down to volume. If you have enough to justify new machinery hook up with some local tool dealers for suggestions. This has to be one of those things that is already solved. If I understand you right you are drilling holes for release buttons in telescoping tubing. Such things have been done for years so there should be something a good tool dealer can suggest. This likely can be done real cleanly with a laser.

If the volumes aren't there then the only thing I can suggest is to continue to experiment with different tooling in a drill press. You might also want to address controlled feed to eliminate uneven feed rates.

Your third option is the tried and true one, farm the job out! That is why all those independent machine shops are out there.

[CRO-WD40]

It gets the job done, but the holes are not perfectly round and it takes quite a bit of reaming, deburring, and honing to get everything nice.

Drill bits never produce round holes, they are always in a shape of a triangle with large radius on its points.
More cutting edges would help, you could try drilling with an endmill here. Thin walls will not fill up the endmil. there are attachments for deburring that you could add to the endmill so you can drill the hole and deburr it in a single operation.

If I were to use a different machine would the holes be nicer/cleaner and require less finishing work? I was wondering if a more powerful drill press or a milling machine, etc might produce better results, and if so what kind of specs should I be looking at. Thanks!

Drill press'es are built to drill. On 0,058" aluminum the size of machine doesn't matter.