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Unibit RPM speed

Draker

Well Known Member
Are there guidelines about the correct RPM speed to use when drilling aluminum with a step bit (unibit)? Reading threads here I?ve seen both ?use high RPM? and ?use low RPM? recommendations. I ask because I?ve had mixed success with this tool in the past, using a drill press to drill the conduit holes in the wing ribs. I?ll be drilling through the main center section soon and want to do it right. Also, lubrication or no lubrication? High or low drilling pressure?
 
Generally speaking slower speeds allow for better control. However, I doubt your issues are with speed. Most get poor results in thin sheet by not supporting the work. I use a wood block under the web to support the sheet and drill right into the block as I make the hole.
If you don't support the web it can flex and bind which can cause inconsistent results.
My guess is you will have much better luck on the thicker center section.
Lubrication isn't always necessary in a non production environment (we typically are not cutting at max work speeds) but it cuts down on tooling wear and certainly won't hurt.
 
Free Opinion

I have had the best luck just using a cordless drill and pretty slow speeds. I start of with a little extra pressure, but once the step starts cutting I back off the pressure and maybe increase the speed a bit. As the step reaches the far side of the sheet, I back the pressure to near zero.

I also use a Sharpie to highlight the desired step, so I don't get carried away. Overall, I have found these tools to be quite handy and make some very nice looking, clean holes. They are prone to "walking" when using the cordless drill, so if the location of the hole is critical, take extra precautions.

Good luck!
 
Support

Support is the key. Also, as the diameter of the hole increases, the rpm should decrease.

Put a 2x4 under the work piece and drill into it. Be aware of hoe you set up the work and table as many units will be long enough to go through the 2x4 and into your drill press table...
 
Great post. I've had struggles too. I second the tips on here. For me, using it in my cordless hand drill, was the marked improvement.
About the lube, I insist yes, use BoeLube on this and everything. I am a huge believer now as I have seen an eye opening marked improvement on drill bit and reamer tool life. Not only life, but I've seen again marked improvement on cutting surface finish. Lube is a must for sure.
 
a general rule of thumb is to use slow speeds and extra pressure for steel and higher speeds with moderate pressure for aluminum.

Larry
 
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I use styrofoam to support the part while drilling. This has the same result as a wood block but it is easier.
 
screwdriver

I have had the best outcome on thin metal using the unibit in a battery powered screwdriver, slow speed and easy to control, also as mentioned above if you can finish the hole from the backside.
Figs
 
I mark crosshairs through the center, extending well outside the finished hole size. On larger holes, it helps me keep the hole 'in the right spot', since the bit will walk the hole sideways with uneven pressure.
 
If hole location is critical I drill a pilot hole using a conventional bit that is the same diameter as the smallest step on the uni-bit. This and a backing board as mentioned previously eliminates the possibility of the uni-bit walking. A very light touch of the uni-bit with the first oversize step after reaching finished size is a quick way to cleanly deburr the hole.
 
Ryan---dont hold the piece in your hand. Support it on a bench, in a fixture , in a vise, something. IF the unibit 'were' to grab and bind in the hole, it 'could' twist, AND if you didnt have gloves on, it 'could' create a very hurtful situation. Thin aluminum can be as sharp as a knife---and we certainly dont want to see red stuff on shiny aluminum--or worse.

Yep sometimes in trying to get it done we forget the little things---and they cost us later--. Been there and yep it hurts.

Tom
 
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