How to centerdrill bowed pen blanks?

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mikeschn

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Hey guys, I'm stumped. I typically centerdrill my square pen blanks on my wood lathe with a Penn State Ind dedicated pen blank drilling chuck. I also use a small centerdrill (1/8" x 5/16"). I draw lines on the end of the blank from corner to corner. When I tighten my chuck up on the blank, the centerdrill on a bowed blank doesn't hit anywhere near the center. I would like to get as close to the center as reasonably possible. How do you guys deal with that?

I have a 3d printer, so I could print any jig or fixture I need to get the centerdrill in the center of the blank. What do you suggest?
 

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I would drill it like I do curved deer antler… on the lathe with a Jacob's chuck and drill bit in the head stick and 60° live center in the tail stock. (Brad point drill bit work best for this). Put a divot on each end
of the blank where you want the center of the hole, and while holding the blank with pliers put the drill point and live center point in those divots. As you drill at low speed, crank the tail stock to push the blank onto the drill bit, drilling the hole. Drill half way through and flip them back the bit out and flip the blank. Putting the drill tip in the divot where the live center was and put the live center tip in the hole and finish drilling. As long as your lathe head and tail stock are aligned, the bit should meet up with the hole in the middle of the blank so the bit and live center don't hit each other.

I drill all of my curved deer antler like this.

If you have enough size in the blank you can also put the blank between centers and turn it straight enough for the chuck jaws to grab and hold straight. The 2 jaw drilling chuck set up works best for this over the 4 jaw system because it centers and hold the blank better when out square.
 
I would use a curved bit. :oops: Seriously, never had that problem...yet. John has good information as I have been putting off drilling a deer antler for ages.
 
LOL. Well, my blank is not "That" curved. As you can see in the image (in the orig post) , when chucked up on the pen chuck, it might be off by 1/8". It's enough to mess up a pen.
 
okay I was thinking a little more crazy... like a dedicated chuck for crooked blanks... grab it on the far end, so that the centerdrill is centered!!!
 

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mikeschn said:
okay I was thinking a little more crazy... like a dedicated chuck for crooked blanks... grab it on the far end, so that the centerdrill is centered!!!
Click to expand...
I hate to be a Debbie-Downer, but that gives you no control over where the drill bit exits the blank.

For this specific blank you picture in the original post, I would use the center bit to create a recess both ends then turn it down to a cylinder between a 60 degree dead center (in the headstock) and a 60 degree live center. Once it's round, you'd be able to hold it on-axis in your pen blank jaws.
 
duncsuss said:
For this specific blank you picture in the original post, I would use the center bit to create a recess both ends then turn it down to a cylinder between a 60 degree dead center (in the headstock) and a 60 degree live center. Once it's round, you'd be able to hold it on-axis in your pen blank jaws.
Click to expand...
That's exactly what I do...
 
Honestly, I would put a dimple on both ends, chuck it between a dead center in the head stock and a live center in the tail stock, turn it round between centers, the once you have it round and to a nominal collet size, chuck it up in a collet chuck and drill.
 
I wouldnt even use the two jaw chuck.
I would use the curved antler method only I would just use a hand drill to start the center drill at the nexus of the two lines you drew from corner to opposite corners. Then use the curved antler method of drill chuck and bit in the head stock live or dead center in tail stock, hold blank with a plier in the center. One center drilled point goes on the end of the drill bit and the other goes on the center in the tailstock. Hold on to the pliers of rest them on the tool holder and slow speed start to advance the tail stock. Once at half way flip the blank around and do again until the drill breaks through.

@Jarod888 beat me to the post.
 
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