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View Full Version : How do I drill hole to a certain depth?



jimmy482
02-19-2012, 02:21 AM
I wanna drill a hole with a hand drill to exactly 3/8 of an inch deep. How can I do this without drilling to deep?

macona
02-19-2012, 02:32 AM
Exactly? Impossible.

Especially with a hand drill.

They make these little set screw stops that you put around the drill shank and lock it.

You can also just put a piece of masking tape to where you want.

kuksul08
02-19-2012, 03:15 AM
Yeah, a collar would work best probably.

Davo J
02-19-2012, 04:02 AM
I always cut a piece of small tubing up to roughly the length, then slip it over the drill bit and adjust the drill bit in the chuck to get the right length sticking out the end of the tube. When using it, I just hold the tube up while drilling the hole to let swarf clear properly, if you clear the drill a few times there is no need to hold the tube up. Once the chuck hits the tube there is no way you can drill deeper, so as long as you measured the stick out properly it will be spot on.

I have tried those collars with the grub screw in them, but don't like them as they can slip.

Dave

darryl
02-19-2012, 04:03 AM
Measure as you go?

One way to do it is to mount the drill bit in the chuck, not quite all the way, then measure the length sticking out from the jaws to the end of the bit. Take 3/8 off that measurement, then cut a strip of thin sheet metal to that width. Remove the drill bit and mount a slightly larger one temporarily. Fold the strip in half around the drill bit, then put the original bit back in the chuck. With the folded strip placed over the bit, adjust the position of the bit in the chuck to give you exactly 3/8 sticking out past the folded strip.

When you drill, hold the strip with one hand so it doesn't rotate. When you have come to full depth, the strip will be touching the workpiece and you can't drill any deeper. By holding the strip stationary, you also avoid marking up the workpiece.

Boostinjdm
02-19-2012, 04:03 AM
OR a sleave could work. Just cut a piece of 1/4" pipe or something long enough that only 3/8" of drill bit sticks out the end. No need for a set screw just slip it over the bit and drill away.

Peter.
02-19-2012, 04:48 AM
Drill over a tube is what I do if I really have to hand drill.

jimmy482
02-19-2012, 04:59 AM
Should pvc pipe work fine? The only thing about that is I can't see where I'm drilling, but I guess it would be fine if I drilled a pilot hole to know that I start drilling in the right place.

RussZHC
02-20-2012, 08:14 AM
Should pvc pipe work fine? The only thing about that is I can't see where I'm drilling, but I guess it would be fine if I drilled a pilot hole to know that I start drilling in the right place.
plus 3/8" deep...and given the capacity of a fairly common hand drill...

No offense, but holy cow...not sure the rigidity of the pipe/tube guide is the point, just saying to fit somewhat closely to the drill bit for all I know you could be looking at something that is more like flex tubing..,
if you can't see where you are drilling how do you expect to hit that pilot hole with any degree of "precision", let alone if we are talking a small size hole (you did not mention the drill size)..,
bottom line is you would have to do the same operation twice (once pilot one "real") in exactly the same spot both to the same depth without any sort of misalignment in a place you can't see...

Davo J
02-20-2012, 09:12 AM
Just start the hole without the tube on, then put the tube on and go to full depth.

Dave

Tait
02-20-2012, 10:57 AM
Hmm.

How are you defining 3/8 deep? Most drills are kind of pointy, so the middle will be deeper than the edge, right?

Dr Stan
02-20-2012, 11:36 AM
Hmm.

How are you defining 3/8 deep? Most drills are kind of pointy, so the middle will be deeper than the edge, right?

In standard drafting, design, and machining practice one dimensions and measures to the "edge", as depth is measured without including the portion produced by the drill point.

Evan
02-20-2012, 01:59 PM
If you need a precise flat bottomed hole you first drill with a drill sleeve so the point goes to 3/8 and then use another bit that is ground off flat at the point and resharpened to resemble a milling cutter.

Tait
02-20-2012, 04:51 PM
If you need a precise flat bottomed hole you first drill with a drill sleeve so the point goes to 3/8 and then use another bit that is ground off flat at the point and resharpened to resemble a milling cutter.

That's what I did, except it was in soft wood, so I didn't bother sharpening after grinding.

gundog
02-20-2012, 05:32 PM
I like shaft collars better for drill collars they are more expensive but they hold better and don't damage the bit you can make your own if you have more time than money. Drill collars have a set screw that holds against the side of the bit and they slip easily. Shaft collars are split and hold to the bit or shaft by clamping around the whole diameter rather than one small pressure point they also set straighter to the bit than the single point type they seem to cant to an angle when tightened.

Mike

Shaft collar http://www.ruland.com/ps_collars_1pc.asp

Drill type collar http://www.ruland.com/ps_collars_setscrew.asp

This place calls them both shaft collars I bought a set of the split collars after having too many of the single point type slip on me and ruin parts.