Splitting Blanks

[tomwojeck]

All,

I've been making cigar pens and have been having troubles with my blanks splitting when I am drilling the hole. It's happened with padauk, bolivian rosewood, and kingwood. I'm obviously doing something wrong, but can't figure it out. I don't know if the blanks are too small, the drill press isn't set at the right speed, or the blank is just shifting enough while drilling the hole that it's breaking.

Any advice that anyone can give is greatly appreciated.

--Tom Wojeck

 

[Scottydont]

What kind of bit are you using? I use brad point bits and have never had that problem. Speed may be too low.

 

[DCBluesman]

I just drilled some 1/2" brazilian rosewood blanks without a problem using a 7mm drill. Are you clearing the drill often enough. Sometimes, even drilling 2 or 2-1/4" blanks, I clear the drill 5 or 6 times...and with real oily woods, even more than that. It takes a few seconds longer, but I've had no problems.

 

[Kurt Aebi]

Clear the chips out of the drilled hole Often, Often, Often.

They build up pressure on the sidewalls if you don't clean out the hole Often.

Did I mention to clean out the chips Often?

 

[tomwojeck]

I was wondering about the speed of the bit. I think that it was to slow. Can I assume that faster, but not top speed, is better?

As far as clearing the bits, I try to do it, but I don't take the bit all the way out, as I'm concerned that the bit won't hit the hole the exact same way and I might get an oblong hole.

I secure the blank to the drill press table by putting the blank in a screw clamp and then clamping that to the table, but I still worry that it might move a bit.

 

[DCBluesman]

I think you just named your problem...not taking the bit all of the way out. If you're good and tight in both of your clamps, you should have no trouble hitting the center with each pass. Then, if you use a little Gorilla Glue on your tubes, it will expand to fill and minor hole problems. The bit needs to be really clean with each pass.

 

[Doghouse]

It will help to get one of the vises to clamp the blank into. That way you can get the bit all the way out. As chips build up, they tend to get stuck at the tip. That is where the friction occurs and causes the blank to heat and split.

 

[Paul Downes]

Another issue with drilling when using a 'regular' drill point is that the center of the drill point scrapes rather that cuts the wood. You can alleviate the pressure by thinning the point. This is commonly reffered to as a split point. It will drill with less resistance but be careful that it doesn't drill too quick. I always cut my blanks long so that any egg shaping to the hole is trimmed off. Always back the drill out all the way and clear off the chips. If the chips are packed tight, you are not backing it out soon enough. Also with some of the harder woods I have found it helps to drip a little water in the hole to act as a lubricant/cooler. This also helps urethane glues to set up well.

 

[rjenkins]

Tom,
be careful about overtightening the clamp, especially on thinner blanks, as this can increase the friction on the bit. A lot of heat is generated drilling blanks. That's why you want to go slow and clear the chips alot. I use a constant flow of air (~35 psi) and about 200 rpm. It'll probably take me about a minute to drill a 2 1/32" blank (slimline). I do a lot of segmenting and cut the blanks very close to finished length, allowing maybe 1/32" for trim. Don't advise this until you are sure you have "blowout" under control or if the blank is not entirely solid. If that' the case, I'll leave ~1/8" for trimming.

If you have the large wooden clamps it only takes a minute to cut matching notches on either side to allow a pit bull grip with not too much pressure. If you need more info on this, post a msg and it will be forthcoming.

Good luck with it.

 

[Scott]

Hi Tom,

I might ask when the blank splits? My biggest problem splitting blanks happens when the drill bit exits out the bottom. A lot of bits can be real grabby when they exit, so the common solution is to cut your blank long, stop drilling short of the end, and then cut off the end of the blank to expose the hole before gluing up.

Scott.

 

[tomwojeck]

Scott,

It was always at the bottom. I took your advice above, as well as making sure that I had the drill press set fast enough and was clearing the bit frequently enough. I was able to make a few sets of blanks tonight with no issues.

Thanks again everyone for your help!

 

[Mac In Oak Ridge]

Tom,
If the same drill bit is being used now that you are having splitting problems, and it didn't used to split, look at sharpening the bit or getting a new one. Could be it is just getting dull.

 

[tomwojeck]

Originally posted by Mac In Oak Ridge
<br />Tom,
If the same drill bit is being used now that you are having splitting problems, and it didn't used to split, look at sharpening the bit or getting a new one. Could be it is just getting dull.

Mac,

They were splitting almost from the get go. I turned the speed on the drill press up as well as making sure that I cleared the bit enough and that made a huge difference.

--Tom