Drilling into end grain

[Greenvilleguy]

In the "Horizontal Boring" thread, Nick mentioned the difficultly turners have hollowing end grain and he suggested using a spade bit to drill into end grain.

Thanks Nick. Making turned boxes or end grain bowls does require hollowing the end grain and as Nick says, it requires special technique. For a smooth finish, a scraper will give you a better cut than a gouge. My approach is to drill a starter hole to depth, use a gouge from center out cutting on the wing of the gouge to cut across the end grain and finish with a scraper. Drilling the starter hole has always been a real heat generator.

Last week, I was watching Tim Yoder turn a box on a PBS show. He used a tool to start the intial hole he called a boring tool. It looked like a spade bit mounted in a long handle.

Thanks to Nick's comment, I now get it. He had ground a spade bit down to act as a scraper to drill the initial hole.

[Nick]

Good try, Doug, but it looks like nobody bit on this topic. Too bad; I have a whole drawer full of Forstner bits that have been ruined by students trying to drill end grain with them. We might have averted some trauma.

With all good wishes,

[solicitr]

OK, I'll bite: how do you drill endgrain? I've always avoided spade bits like the plague, except for bashing wiring holes through rough framing.

[Greenvilleguy]

Well, it seems I mainly know what not to do. In the wonderful world of turning, you need to drill into end grain often, i.e. bud vases, boxes, end grain bowl, etc. I started out with forstner bits, but they generate an enormous about of heat. (for reasons Nick has now explained.)

I've been using brad point bits and they work, but I couldn't tell you why.

Some of the more famous turners like Richard Raffin use a spindle gouge as a drill. I'm assuming now that the wings of the gouge are cutting the end grain against the side of the grain, i.e. supported fibers.

My theory is based on turning. When hollowing end grain, you always cut from the center out. The more you can cut across the end grain instead of directly into it the better the cut. If I could draw, I'd draw a picture of the strains of grain running parallel to the lathe bed and the chisel cutting best when cutting across the grains instead of straight into them.

I'm hoping Nick will chime in and give us some suggestions and perhaps confirm or reject my theory. I haven't had a chance to try it yet, but I'm thinking I could take a spade bit and grind it so it had more of an arrowhead shape to reduce the amount of end grain it was cutting perpendicular to the end grain and instead slice across the end grain at more of an angle.

[reible]

Hi,

I once attended a demo and the person showed using step drilling and claimed that it was the way to go to make deep holes in end grain. I personally have never tried it but for what it is worth I'll post what I remember of the idea.

You start with the finished hole size and pick that bit. You drill in just enough to provide an area of that hole size which will be used later to guide the bit. You next take the next drill size smaller (I think he was going in 1/8" steps) then do the same sort of thing, that is using the point of the first hole to do the second hole and again only as deep as need to guide the bit. He did this until he was down to a 1/4" twist drill.

I did a few sketches to show how this works so maybe you will want to take a look at them as we go. So far we have covered the first 3 sketches. Now you start coming back out drilling each hole to the size of the step and having the step you drilled earlier as a guide. See the forth and fifth sketch.

You work your way back to the hole size you want and you're done. It took a while with all the drill bit changes and clearing chips but it did work. Someone did ask about bit life and he said he got years out of his bits and had been doing this for some years.

Like I said I've never done it but he made it look easy. Any brave soles out there you might want to try this out I'd like to here back from you.

Since you allowed only 5 attached files see my next post for the remaining couple of sketches.

Ed

[reible]

Remaining sketches attached.

Ed

[Greenvilleguy]

Thanks Ed,

I guess this just minimizes the amount of end grain being cut "head on" in each step, while providing a guide surface. Good idea!

[charlese]

Remaining sketches attached.

Ed

Thanks Ed (3d)! Good explanation! Makes it simple, even for me! Always have disliked spade bits. Don't know why - guess they never seemed smooth enough.

I've made a few deep holes in end grain with Forstner bits and haven't yet had one come up "Ruined". Of course I do occasionally sharpen my bits. Even the brad points. (smaller ones are a problem)

[Greenvilleguy]

Well, let me confess -- I have ruined a forstner bit drilling into end grain. Worse though, I've created so much heated that I've cracked the work piece. This happened again just last Monday (yes, after we were into this thread and I should have known better). I was drilling a hole in a weed pot, AKA bud vase and the narrow neck cracked due to the heat generated from the drilling.