[Jack Burton]

I'm trying to drill a 1/8" diameter hole, 5" deep axially through a 1/4" dowel rod. I'm using an aircraft bit which I trimmed down to 6". I tried the drill press, both conventionally and lathe-mode (work chucked, bit stationary) but still, too much slop. Even after making a jig with a drill guide bushing, I can't get more than 3" in. No matter how centered and squared up I get it, the inherent flex of the bit seems to make the hole wander off course and bust out the side. I guess drilling endgrain makes it even tougher. I can't help but think that even on a metal lathe this would be difficult because of the bit deflection.

I'm thinking that running a bit in a tube/sleeve that follows the bit would help but that seems awfully involved for something like this.

Any ideas?

[smdysmf]

Try starting with a shorter bit then switch to the longer one to finish.
The shorter one won't deflect as bad and give you a straiter hole to start with.

[WoodSpinner]

I'm trying to drill a 1/8" diameter hole, 5" deep axially through a 1/4" dowel rod. I'm using an aircraft bit which I trimmed down to 6". I tried the drill press, both conventionally and lathe-mode (work chucked, bit stationary) but still, too much slop. Even after making a jig with a drill guide bushing, I can't get more than 3" in. No matter how centered and squared up I get it, the inherent flex of the bit seems to make the hole wander off course and bust out the side. I guess drilling endgrain makes it even tougher. I can't help but think that even on a metal lathe this would be difficult because of the bit deflection.

I'm thinking that running a bit in a tube/sleeve that follows the bit would help but that seems awfully involved for something like this.

Any ideas?

I'd suggest using a shorter bit and drilling in from both ends to achieve the 5"

John

[neilw20]

Start with a center drill.
The a stumpy 7/64 for a stable pilot hole, peck drilling
The a 3mm drill to full depth plus more, peck drilling to keep drill unclogged.

Then run the 1/8" drill through to finish.

Run, say 2000 RPM.

You might need to do it from both ends, at least with the initial steps.

[CarveOne]

If this is a wooden dowel rod it has grain that does not usually follow the center of the dowel. The drill tip will tend to follow the wandering end grain.

Select the dowel for the straightest grain structure you can find. Use the stiffest drill you can find. Cheap drills are usually fairly flexy because they have flutes that are ground too deep, or are made of metal that is not very rigid to begin with.

If using a drill press, the table surface needs to be set as close to 90 degrees to the quill's center line as possible or it will start drilling the hole at an angle anyway.

CarveOne