What tooling to drill lots of 10mm holes 45mm deep?

[AlanMJackson]

Hi Lee,

It's a bit of a basic question, but how do you get a good finish on the bottom surface when through drilling wood? Even when I do this by hand on a drill press I find this hard. I use sacraficial wood underneath but the holes still blow out. Do you need to clamp down really hard?

I like your idea of slowing down again for the bottom surface but even when I feed slow the whole way it was blowing out so I must be doing something wrong.

-Alan

[Lee Roberts]

Hi Lee,

It's a bit of a basic question, but how do you get a good finish on the bottom surface when through drilling wood? Even when I do this by hand on a drill press I find this hard. I use sacraficial wood underneath but the holes still blow out. Do you need to clamp down really hard?

I like your idea of slowing down again for the bottom surface but even when I feed slow the whole way it was blowing out so I must be doing something wrong.

-Alan

No I think your right Alan, it is generally difficult to drill wood without getting any blow out on the other side of the hole, what I was suggesting was that by lowering the feed rate on the final pass’s may produce a better result than what your currently getting.

You see if you was to use an end mill and also combine something called ramping, I would think you would be eliminating some of the downward force produced (as we know) from trying to drill a hole with a normal drill bit (as the drill pass’s out of the wood the tip push’s the material away before its had a chance to cut it), though I must say I find using a sacrificial piece of wood under the hole I’m drilling sufficient allot of the time.

Using an end mill in this way would mean more force sideways and mean you’re using the side of the cutter, rather than the bottom.

I really don’t like the idea that you are using a hand drill on the machine, though I guess for this job using a hand drill for the spindle, it’s probably the better option to use a drill bit.

.Me

[AlanMJackson]

Do you think I should be using something like this?:

CNC Router Tooling Thru-Hole Drills. CT 70 mm length -Thru-Hole, Right Hand

[AlanMJackson]

The plot thickens...

I'm going to use furniture bolts so I was planning to counter bore the holes. I imagined I would have to do that in another pass but it might be possible to do it in a single pass with a bit like this:

Wealden Tool Company Limited Drill Counterbore

If I can find one big enough (10mm pilot, 16mm counter bore, 25+mm cutting length)... is that likely? I would have to counter bore on each face anyway so that would remove the advantage of through drilling if I could drill and counter bore at the same time.