Thread: Colt drill bits and MDF

First thing Geoff are they "Twinland" or "5* FCE" (i.e tool steel or HSS M2)?

They're Twinland.

Hmmm. I've only used 5* so far, and they eat timber like nothing else. I should dig out a Twinland tomorrow and see how it compares, but what you're experiencing doesn't sound like it should be the case. Have you checked the tip geometry under a loupe for sharpness? I did have a couple of 12mm twinlands come over that were bent (like visibly so) but nobody has ever come back to say that they were no good - quite the opposite in fact. What I'm getting at is the drill may be faulty/previously dropped or something, dunno.

What are the two sizes (imperial as I recall)?

The two drill bits supplied with the jig were 1/4" and 7/16" - according to the Woodpecker site, it's too cold to go out to the shed to check

Yeah I thought one was a 1/4". If you email me your address I can post you a 1/4" 5* because I've got a few spares, and can order more anyway. Now if that doesn't work then it's the jig interfering I'd say. The 5* gives a fabulous clean result.

Thanks for the offer.
What I'll do first is try the Triton brad point bits I have. 6mm and 11mm should be close enough. I'll also try the Colt drill in 'real' wood.
I've sent an email to PWS to see if they've any ideas or if anyone else has reported MDF drilling problems.

Good thinking, those two tests should give you a few clues. MDF isn't known for jamming in the flutes, and you shouldn't have had to use that excessive force.

Now this might sound like I'm fully insulting your intelligence, but it's worth a try because I've heard of it being done before.....the drill wasn't in reverse was it?

Originally Posted by FenceFurniture

Good thinking, those two tests should give you a few clues. MDF isn't known for jamming in the flutes, and you shouldn't have had to use that excessive force.

Now this might sound like I'm fully insulting your intelligence, but it's worth a try because I've heard of it being done before.....the drill wasn't in reverse was it?

Wonders how he would have a hand held drill in reverse

Maybe I should have said battery drill instead of hand held?

My first thought was that I had the drill in reverse so I did check. I did try running it in reverse in case I had some special left handed drill bit

I got an answer from Graeme at PWS who confirmed that he has had similar problems with MDF and that cheap spade drills did the best job.

I'll try a few more drill bits and different timbers to see what results I get.
The hole for the dowel can be a blind hole which will eliminate the tearout and the small hole for the bolt will be covered by the fairly large bolt head so should OK if there's an 'exit wound'

A few test reveal that the Triton brad point drills have the same problem in MDF. A spade drill works fine as does a standard twist drill, a bit of tearout with both of these.

I tried the Colt drills in plywood and some pine and they work very well, especially on the drill press.

I made a quick joint and the jig works very well, certainly more accurate and quicker than I could do by myself.

I see. Maybe one more thing to try - what result do you get drilling MDF with no jig, either in the press or handheld?

Results without the jig were about the same. As the drill moves a bit from side to side while drilling without the jig, some test holes were neater, especially with the 1/4" bit.

I'm going to do some tests with the drill press so varying speed isn't an issue. I should be able to get a more constant downward pressure as well.

I haven't worked out if it's possible/practical to use the jig on the drill press, I need to work out a method to clamp things together. [The jig is pretty basic - see attached]

What about the pressure you needed to apply?

Ok, I just drilled a few holes in MDF with a Twinland and a 5* (both 1/4") and whilst the 5* gave a cleaner result, and with a little less pressure, there wasn't a huge difference. The Twinland gave a pretty good result, with only one hole being a little bit ragged around the entry. Then I changed to a Colt 6mm beam drill and this required a little more pressure (different tip geometry) but also gave a clean result. At 250mm long it wanted to flex a bit, and so the pressure needed to be less than I'd normally have used, therefore the going was a bit slower.

So, the bottom line was that the 5* was the best by a margin of say 10-15%.