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Drill Drift

Awl --

How does a drill drift in x,y, with drill depth?

I would like to drill four 5/16 holes through a series of 1/4" alum plates (actually wide 6061 or 6063 bar), where the holes must line up later (within .001-.005), and wonder how deep I can stack these plates and stay out of trouble. The hole is a clearance hole for 5/16 threads, but a semi-tight clearance hole.

I am hoping 8 plates would be OK, with a "regular" drill, either 118 or 135 deg. If not 8 plates, about how many?

How does drift vary with speed, feed, pecks, drill point geometry, etc? Best drill? I will of course spot the hole. On a fadal, altho I have considered a P-pushing fixture on a drill press or BP to do this, as well.

On the fadal, I suppose I could come back with a long 5/16 em, which would increase the clearance a bit, but would improve alignment. But I'm hoping to not have to do this.

Reply to
Proctologically Violated©®
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PV, I'd use a 5/16 parabolic flute, split point drill. I wouldn't think you would have problems. I drill a 5/32 hole in a 10.00" long alum piece 5.20" deep from both ends using a parabolic flute drill. The worst mismatch is around .010 I would guess.

I use a Titex drill for this, none of those Costco Worksmith drills!

Best, Steve

Reply to
Garlicdude

Don't worry -- the only thing parabolic on those Costco drills is their wobble.

Reply to
Proctologically Violated©®

Reply to
RoyJ

Reply to
Kirk Gordon

rescuesite.com/

have you considered one of those insert type drills ? they had them at my last place and they went nice and fast into tool steel, and dead accurate too. when the insert wore, replace and keep on going. highly recommeneded.

Reply to
raamman

Reply to
Proctologically Violated©®

You need to be using a quality drill with a good point and relief, but I have found the most important point is starting each hole with a center drill. If a jobber length drill drifts off even a couple of thousandths, you are no longer in line with the spindle and will be forcing the error to multiply as you drill.

I have drilled 5/16" holes through aluminum castings as much as three inches with no more than .002 drift.

Of course, having your spindle perfectly square with the work piece is usually very important as well, depending on the required accuracy with the outside edges of the work piece.

Reply to
Tim

That was a very interesting read. Since I just fix the machines and you program and run them, you send in the tuition check. I'll just thank Kirk for the lesson ;)

Wes

Reply to
Wes

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