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Drill runout woes

gotyoke

Well Known Member
I'm about to countersink the main spars for the RV-14 wings, but the wobble in my electric drill has me worried. The pneumatic drill is too fast. And my drill press doesn't have enough height. I have already sunk $200 into trying to address the runout of my handheld drill (new chuck = slight improvement, new drill (Makita) = even more runout than the older one).

I'd love some of your thoughts on what I ought to do about this conundrum.
 
Countersink

I'm about to countersink the main spars for the RV-14 wings, but the wobble in my electric drill has me worried. The pneumatic drill is too fast. And my drill press doesn't have enough height. I have already sunk $200 into trying to address the runout of my handheld drill (new chuck = slight improvement, new drill (Makita) = even more runout than the older one).

I'd love some of your thoughts on what I ought to do about this conundrum.

Set the cage shy of the target and finish by hand. Actually, speed is better. Again, set it shy. You can always cut more.
 
In the past, I have found that if the countersink has a good pilot then it should take care of the alignment.

Use a bit of lube if the pilot is on the tight side.
 
Exchange the Makita

If the Makita is new and has runout I would return it and exchange it for another unit, because that is a manufacturing fault. The lack of quality control on mass produced items is annoying, but Makita is usually good. I would take a straight drill bit to the store and check the runout of the replacement unit before you leave.
 
Remember that the bit pilots in the already installed nutplate.
Runout in the drill isn’t going to be a problem unless it’s very bad.
Try it out with a K-1100 nut plate riveted to some scrap 063 to convince yourself.
 
Remember that the bit pilots in the already installed nutplate.
Runout in the drill isn’t going to be a problem unless it’s very bad.
Try it out with a K-1100 nut plate riveted to some scrap 063 to convince yourself.

That's a good point. I never use a countersink cage without testing on scrap. Every single time. I don't trust them.
 
spar countersink

Just don't go anywhere near the spar parts with the hand drill until you figure out the problem! Practice on some scrap material first, even if it means installing some nutplates on a simulated spar part to practice with.

Or....beg, borrow, or steal the use of a larger drill press to countersink these parts. Even then, practice on some scrap first.

Running some practice parts will show if the runout is/is not a problem. Plus you can figure out the feeds, speeds, countersink depth, and cutting fluid thing too.


Still looking for a "magic drill" that, when reversed, puts the chips back in the hole that I just messed up. Haven't found it yet. :)
 
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For anyone interested, where I landed was I bought a single-flute countersink bit (from Cleaveland Tool), not expecting it to be much better than a three-flute. But I was wrong, that thing is amazing! I got it dialed in on scrap and it was flawless on the spars using the pneumatic drill. Very pleased!
 
Re: single flute. Just be careful with the single flutes on thin materials. They can pull the material up into the cutter, resulting in a deeper C/S than expected. (a cutting lip vs shaving edges on the three-flute style)
They are awesome though. Very clean cuts and no chatter.
 
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