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

Hi Mike,

I'm making some reconfigurable shelving. I'm drilling a line of holes along lengths of wood, about 40 holes per metre. As mentioned before the holes are 10mm through holes and 45mm deep. Because I'm drilling from both sides to get a good finish I'm actually drilling 80 holes per metre but if I could get a good finish on both sides drilling straight through I could save lots of time.

If I could get accuracy of 0.5mm for each hole that would be great. Even 1mm would probably be fine. So I don't need much accuracy.

With help and ideas from the forum I've tried some experiments today and found I can get feed rates of 400mm/sec but the surface finish is poor. So I've written some drilling gcode that feeds at 50mm/sec to break the surface for a few mm then goes to 400mm/sec for the rest of the drill cycle. Which means I've halved the program time and I'm now doing a metre in half an hour.

I've got a batch of 25m to do now and I'll be wanting to do 100 - 200m soon. I ran the hand drill for about 6 hours the other day and about 2 hours today. So it looks like I'll be running the machine for a few hours a day.

Quote:

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Originally Posted by AlanMJackson

With help and ideas from the forum I've tried some experiments today and found I can get feed rates of 400mm/sec but the surface finish is poor. So I've written some drilling gcode that feeds at 50mm/sec to break the surface for a few mm then goes to 400mm/sec for the rest of the drill cycle. Which means I've halved the program time and I'm now doing a metre in half an hour.

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Hi Alan,

That is good news i'm glad your getting somewhere with it, I'm now wondering if you could go all the way through with the holes but on the last few mm drop back down to 50mm/sec and hope for the same finish as the top?

.Me

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

Quote:

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Originally Posted by 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

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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

Hi Lee,

I agree about the hand drill - it's a real bodge. I'm using it at the moment because I haven't been able yet to work out what would be better. I've found trying to select the right end mill, especially for through hole drilling, is a bit baffling to the new comer! Also I don't have a spindle yet. Have you got any recommendations?

-Alan

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

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

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.

Hi, if you counter bore on both sides why is the finish on the under side a problem ? surely the c/bore will take care of this. If you get a spindle I think it would be much easier and you can use an end mill and program any hole size and counter you wish. Of course you will still have to turn the material over for the second c/bore. The break out on the underside could be eliminated if you use a down spiral cutter. Good luck with whatever you try. G.

Thru drill like you posted will work resonably ok but depending on material and grain structure you will still possibly get some breakout.

Milling Holes is too slow and isn't often done for holes this size and in wood. Much quicker to drill just past half way with No or few Peck's then flip material and use same G-code.
This is really the only way you can guarantee no tear and If you find the Drill/Counter bore you need then this will save loads of time.

Also there's nothing wrong with using a Hand drill for drilling, that's what it's designed to do, just don't try using it for Milling that's when you have trouble.!

Hi Alan
A different perspective ?
I am not fortunate enough to have a CNC machine so do most of my stuff using jigs, with your equipment you could make a very accurate jig from MDF with it bored @ your required locations to suite a router guide bush,variable speed router would allow you to dial in the required speed and i can see no reason why 2 or 3 plunges should not complete a drilling(plus you can feel how it's cutting. would go with the bit that Dean suggested earlier as i think you need it scribing on breakthrough to try and negate breakout.
regards
Mike