First my holes were too big, now they're too tight

[jgerman]

Hi all,

My first few pens I was getting holes that were too loose resulting in the blank separating from the tube during turning. Switching bits helped that out tremendously.

However now, occasionally, I get holes that are too tight in spots... it sounds physically impossible but here I am, the tube jams up partway through the hole.

Any advice to sort out what's going wrong here? I'm wasting blanks

I'm using a 3/8" twist bit and drilling on the lathe. I believe this has only happened with burl blanks. I'm guessing I can take a file to the hole and ease it a bit but it's still very frustrating.

 

[KenV]

The wood is moving. The most common reason is moisture in the wood is changing and the wood is moving.

New purchases???

Drill one day and check the hole for clearance the next day (or a few days later).

May have to redrill or file out the kinks.

Had some cherry burl that was supposed to be dry. When it was really dry, it was corkscrewed in shape.

 

[jttheclockman]

Heat will also cause this.

 

[SteveG]

Here are some thoughts...

Hi all,

My first few pens I was getting holes that were too loose resulting in the blank separating from the tube during turning. Switching bits helped that out tremendously. If a bit is even slightly not straight, it will produce a larger hole than the actual size of the bit. Unless you always use high quality, straight bits, the nominal size of the bit will not likely indicate the actual hole diameter...it will end up oversized. It is somewhat of a challenge to reduce oversize holes. Perhaps there is another, larger size kit that be used with the oversized hole blank. If one gets too large, set it aside for later, rather than glue it up. This will avoid ending up with an unusable blank. Bits that are correctly sharpened, and very sharp are more likely to yield a correctly sized hole.

However now, occasionally, I get holes that are too tight in spots... it sounds physically impossible but here I am, the tube jams up partway through the hole. If a bit follows the grain, or even shifts off center due to some difference in the make-up of a non-wood blank, you get a curved hole, which will feel like it is "smaller" at some point as you insert a fairly tight fitting tube. I have two sizes of rat-tail files at the bench to correct and resize bored holes, as needed. If a blank is not fully dry, it will tend to dry more quickly and often warp, once it is drilled, as already mentioned. Learning some simple techniques to get the hole you want, the first time, will ease the frustration!
Any advice to sort out what's going wrong here? I'm wasting blanks

I'm using a 3/8" twist bit and drilling on the lathe. I believe this has only happened with burl blanks. I'm guessing I can take a file to the hole and ease it a bit but it's still very frustrating.

 

[randyrls]

Jeremy; As said above, either a bent, or dull bit will cause this. Check the bit for straightness. If the bit is dull, the only solution is to sharpen it on a drill doctor or something similar, or get a new bit.

The other major cause is stress or moisture in the wood. When the hole is drilled the wood flexes and the hole isn't straight any longer. To fix this, place the blank in a vice with light pressure and re-drill the hole again. If the hole is oversized, you might want to use polyurethane glue like gorilla glue to take up the excess space. If you use polyurethane glue, make sure to check the tubes do not move during the curing process.

Hope this helps.

 

[jgerman]

Thanks all. I'll sharpen the bits and I'll try re-drilling today to see if the blank is finished moving!

 

[MTViper]

Jeremy,

JT had a good point. Heat will definitely cause the wood to move, especially if it's a little wet. If you drill too fast or don't clear the swarth often enough, heat will build up. Waiting a day is not a bad idea. If you don't want to wait, wrap a piece of 80 grit sandpaper around a 0.25" dowel. Make sure it's long enough to reach all the way through your blank. You can get it round inside in a hurry.

Steve