drilling pen blanks

[rdewinter]

Drilling a hole in pen blanks has become a frustrating problem. When I drill a hole thru the pen blank, it starts in the center at the top but exits the blank off center at the bottom. I tried to turn the pen blank anyway but it usually blows apart at the very end of the turning process. Obviously, this is very frustrating. I use a dedicated 10er in the drill press mode to drill the hole. I locate the center of the blank with 2 diagonal lines and use a center punch to create a hole to insert the brad point drill bit. When I drill the hole, I clear the wood shavings quite often. I also use a Rockler centering jig to hold the blank at 90 degrees to the table.
Any and all suggestions to resolve this problem are welcome.

[tom_k/mo]

Are you drilling wood or acrylic blanks? I've had problems in the past with acrylic blanks breaking out at the bottom but very seldom wood. I believe that using a regular HST drill rather than a brad tip is better on acrylic blanks, but the best solution I'v found that eliminates the problem completely is leave the blanks slightly oversize, and when you drill, drill a blind hole, just slightly short of exiting the end. Then after drilling the hole, cut the end of the blank off. Eliminates the problem of breaking on acrylics completely.

[wa2crk]

Try a variant of this fixture
[ATTACH]11216[/ATTACH]
I made this for a 520 fence but it can be modified for just about any machine.
I have turned many pen blanks where the hole wandered and were off center without having them blow out. I found that when I do have a blow out near the end of the turning (down near the brass tube) it has been from too little glue on the brass tube. Sometimes more is a little better. Also could be caused by a lathe tool being not sharp enough. If the hole is off center the blank should turn round and true up to the brass tube. If it is severely off center then you may run out of available material on the blank for the pen you are turning. In that case keep the blank for a different model of pen.
Bill V

[kalynzoo]

Not an expert by any means. However, I did experience drift in the drilling process making the bottom of the blank off center. I now use a jig similar to the one noted in the above previous link. I use blanks cut about 3/4x3/4 and at least 1/4" longer than needed. I then drill downward taking small bites, using 3 ro 4 insertions to drill through, allowing waste material to be removed reducing friction.
I'm not saying all holes are not perfect, just all are closer to center. I can cut off offending ends truing up the blank, and with plenty of wood attached to the brass I can turn the blank without a blowout.
To be total honest, I still end up tossing an occassional blank because in the drilling the end result indicates I will be less than satisfied with the presentation.
Merry Christmas and Happy Holidays.

[ss50th]

Is the drifting occurring more with harder woods than softer? I read an article that the drilling should be only 1/4" at a time even when boring into a four jaw chuck (different type of machine).

[fjimp]

You have received great advise here. May I add that I find a sacrificial block of wood inserted under the blank being bored assume the pressure where the bit exits the blank and I seldom have a hardwood blank blow apart. Softwood blanks are a different story. I am also very careful to use sharp bits. fjimp

[pennview]

Just a thought, but have you checked to see that the table is square to the spindle. You could check this easily, by putting a board on the table and drilling a hole with the 7mm bit through the board, inserting a brass tube in the hole, and then using a true square to ensure the hole is drilled perpendicular to the surface of the board. If that checks out, perhaps the Rockler vise is moving while you're drilling, or it isn't holding the blank square to the table. Or, maybe there's a problem with the bit. You could trying drilling a hole with a different bit, about a 1/4" diameter, and see if that will drill straight through a blank.

[wa2crk]

Just a thought about drill bits. If you are using a standard twist drill make sure that the cutting edges are ground to the same angle. If the faces of the cutting edge are not at the same angle then drift and binding can occur. One of the best investments I have made in the way of shop aids is a "Drill Doctor". They make the bits real sharp and it only takes seconds to sharpen them.
Bill V

[hdtran]

I built a jig similar to the one here

http://www.shopsmith.net/forums/attachm ... 1245373528

I first did something like this one:

http://www.shopsmith.net/forums/showpos ... stcount=28

Both do a good job. The one on top is easier to use; the one on the bottom is easier to align square to your drill bit.

Of course, make sure your tools are sharp, and be extra careful if your blank is cut on a bias, so that you're turning end-grain.

[iclark]

I got introduced to the Colt 5 star drill bits
http://www.woodcraft.com/Product/208020 ... t-7mm.aspx
in a pen turning class. the difference is amazing.

also, to test the plumb-ness of the drill chuck to the table, you can take a stiff piece of wire (like a section of wire coat hanger) and make a feeler tool. start with a straight wire and make 2 90* bends so that it looks sort of like a crank: a short vertical section sticking up, a 4-5" horizontal section, and a short section pointing down. chuck the top vertical into the drill chuck. extend the quill until the lower tip barely touches the table, and rotate the quill. if the table is squared up, the tip will barely touch all the way around. putting some tape on the end that touches the table will prevent scratching.

as indicated above, if the spindle is not plumb to the table, then your hole cannot stay centered in the blank.

someone has already pointed out the importance of a properly sharpened bit.

the other thing to check is the quill bearing. unplug the 10er, fully extend the quill, mount a large bit in the chuck, and side load the bit in different horizontal directions. look at how much the drill tip moves. if it moves much, you need to figure out if your chuck-to-spindle mount has play or if your bearings are having a problem.