Drilling... entry and exit holes are larger than the bit!?

[Justin H]

I've got a Barracuda chuck and the pen blank drilling jaws that go with it.
Pen Blank Drilling Jaws for C Series Lathe Chucks at Penn State Industries

I've used them quite a few times in the past with excellent results. It's been a while since I've made any pens, but I had a specific request for a few, so I fired up the lathe and went to drilling.

For some reason, I can NOT get clean drills. No matter what size, even stepping up sizes. Acrylic or wood, no difference.

The tube fits tightly, but the entry and exit hole at each end of the blank has a significant gap between material and tube. I can physically SEE the drill bit wobbling at times while drilling! First thing I did is try several different drill bits, from 3/8" to 37/64ths. (God I hate the over/under shotgun pen...) The tail stock is tight, I use a keyless drill chuck, which is without movement when checking by hand pre-drill. The chuck on the head-stock is tight as well.

I cannot figure out what is going on. Can someone please help? Ideas to try? Anything? I tore down my drill-press assembly that I used to use and sold my vice, so I'm not in a position to switch back in a hurry.

The blank I'm attempting to drill now is for a Nova Sceptra, simple single tube 3/8" drill. I'm getting really sick of ruining nice blanks.

 

[Mr Vic]

Make sure the morse taper of your tail stock and drill chick are clean little crud could cause the drilling to be off center. Mount a pencil in the drill chuck and turn by hand with it againest your blank. If you get a circle your off center. If all you get is a dot then your set up is true and I'm at a loss.

I ocassionally get a bit of flex from longer bits causing an enlarged entry hole. I found using a longer blank allows me to trim the oversize piece off.

 

[ed4copies]

You say you used several drill bits---so that should not be it.
You say the headstock is ok---I believe you.
So, the tailstock and the drill chuck remain. And, if the hole is larger at front and back, it would imply a crooked (to the travel of the chuck in the headstock) bit.

My GUESS: Your (Jacobs--Drill head) chuck is somehow out of alignment--MT is dirty, not seated properly, or just the jaws are not straight for some reason.

One comment, I have seen holes that are enlarged on entry---I have never seen them enlarged on exit. That would seem to dictate that the bit IS traveling crooked.

FWIW,
Ed

 

[Ed McDonnell]

Have you tried removing your chuck jaws to make sure there is no chips or anything that might be causing them to be not seated correctly?

Some things you could try:

To check headstock and tailstock alignment:

Remove the barracuda and put a dead center in the headstock. Put your live center in the tailstock. Move them up so the points almost touch. Either eyeball the alignment or put a thin piece of metal (e.g. a razor blade) between the points. With the thin piece of metal in contact with the dead center and live center, it should be perpendicular to the axis of rotation. If the metal ends up angled, it will indicate where you are out of alignment.

With the headstock and tailstock aligned:

1) mount a 1/2" diameter straight rod of metal (transfer punch, drill rod, any old metal rod that is straight). You could even use a drill bit, but it will be harder to see a problem in the later steps.

2) move the rod in the drill chuck up into the jaws. No blank in the jaws and have them open enough so the don't contact the metal rod.

3) Slowly close the barracuda until the jaws make contact with the rod. Examine the whole length of the rod inside the jaws. The jaws should contact the rod simulataneously on both side and along the whole length of the rod. If you get partial contact something is out of alignment.

Ed

 

[StuartCovey]

I agree with the previous posts. Something is probably out of alignment.
Or it could be that your not cleaning out the shavings enough. I've had problems like that simply because I wasn't pulling the drill bit out enough times throughout the drilling process.

 

[designer]

Are the drill bits used from other previous projects? Are they sharpened on center or a bit off center? If sharpened off center it can cause the problem as well.

 

[studioseven]

What speed are you drilling at? A slower speed may help.

Seven

 

[Wood Butcher]

I experienced the same issue and solved it by twisting the drill chuck in the tail stock. I lock the tail stock and loosen the "quill" slightly. With the speed set around 500rpm I grasp the drill chuck that has been installed in the tail stock and twist it toward me while I rotate the ts handle. I continue holding the twist until the bit is maybe 1" into the material. Of course backing out to clear chips helps. The reasoning is that the "quill" in the tail stock will have play when the locking lever/handle is loosed. It will rattle around and cause the bit to move off center and back and forth. This is worse in wood (following the grain) than in the plastics. That's my take on it.
WB

 

[Tom T]

Justin, glad you asked this question. Alinement has been a recent issue for me. Mr. Vic I like the pencil idea, and all the other thoughts from every one. It seems my mandrel goes silghtly up hill at the tall stock end.

 

[randyrls]

Justin; This is a fairly common problem.

There is an alignment check you can make in the IAP Wiki

Also When retracting and inserting the drill bit into the hole, turn the lathe off.