LumberJocks Woodworking Forum banner

Drill bit size and type for this project?

1229 Views 5 Replies 4 Participants Last post by  MadMark
I am working on a project that will use a variety of hardwoods, primarily black walnut, to produce quantities of wooden handles for indoor/outdoor use. Ambient humidity/wetness will fluctuate accordingly, and the wood will 'move'. I don't want any failures over this issue.

The handles will be 1.50" thick and 5.0" - 7.0" long. They will be mounted using a 0.25" diameter machine screw that runs the length of the handle. I need to precisely bore a hole through the center of the handle to accommodate the machine screw and will be using a drill press and vise for this part of the process.

The bore will be parallel to the grain, and the grain may not always be very straight. Much will be highly figured.

My thoughts/questions involve the type of drill to use, its diameter, and whether a pilot hole is required. And of course any other advice you have.

1. If I use a drill bit 0.25" in diameter to accommodate a machine screw of the same diameter, wood movement/shrinkage and a bit of mechanical stress could force the handle to split. If that's a valid concern, the answer could be an oversize bore. One common oversize bore for an 0.25" fastener is 0.266". An alternative bore is 7 mm (~0.276"). Are these bore dimensions reasonable, or excessive?

2. I have been able to locate standard twist drills at 0.266", but no augers. However, I can get augers at 7mm. Precision is important, and I have heard that augers on bores of this length don't drill straight or keep a reliable diameter-although they remove material very efficiently. Given these alternatives, should I go with a standard twist drill, or an auger?

3. I've read that piloted augers can be too aggressive and damage the workpiece. Would it be best to drill a pilot hole first, and then use a piloted auger, to achieve a best compromise between precision and efficiency?

4. There's other drill bit types out there, like the 'barefoot' auger, maybe I'm looking at the wrong bit types. Should I be looking at something else, and what would that be?
See less See more
1 - 6 of 6 Posts
Are these handles going to be turned? You didn't specify, but I was imagining they would be for small gardening tools or grill utensils, something of that nature. If you were planning on turning them, you could always drill out on the lathe. I'm sure others will chime in here, but after a couple dozen pens, I've never had problems drilling with a good quality parabolic style bit, even in burls where the grain is all over the place.
A) There's not enough movement in a piece that size to stress the wood to the breaking point.

B) Good luck on boring a perfectly straight hole of that length. I've been trying to figure out the best method for a while now. The issue is that drill bits that small in diameter will flex, no matter what you do and longer bits will flex more and will try to follow the grain to some extent.

After lots of trial and error (many, many errors), the best I've been able to come up with is using sharp, high quality brad point bits at a high speed, carefully marking and drilling from both sides to meet in the middle. Sometimes the holes don't line up perfectly in the center, due to the flex, but if you are talking about oversize holes being OK, then that shouldn't be an issue for you.

You aren't going to find the quality of bits you need at the hardware store, either. Lee Valley has some very good brad point bits that work if a jobber length is OK-you'd have to check to see how long the flutes are. I don't think they would be long enough on a 1/4in bit to reach the center of a 7in long piece. For longer lengths, I've invested in some WL Fuller brad points and am very happy with them. They are spendy, but are superior quality and give excellent results.
See less See more
You can't drill that deep on your drill press as most presses only have about 3" of quill stroke.

There are some pretty long augers out there, and twist drills as well, that are long enough for the job. On the drill press, I'd go as deep as possible, then raise the bed, and finish. If that can work.
Raising the bed while running is dangerous. Doing it stopped & restarting may move the work piece.

I make 7" pipes and drill the stems 3/16" in two steps. First is in the drill press for the first 3" and then clamp and use an 'aircraft drill' in a hand power drill for the rest. And yes, the aircraft drills wander about 5% of the time.

1 - 6 of 6 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.