Trouble with centre-drilling resin pen blanks

[Doktor_Zeus]

I get the feeling that some of these centre drills are combination centre and spotting drills. Certainly more than one shop I've looked at lists what appears to be a centre drill as a spotting drill. Hard to tell from the pictures, but it looks like at least some of them have 90 degree tips.

[Bill21]

Here’s some more on spotting drills.

https://www.cnccookbook.com/when-to-use-a-spot-drill/

Many years ago I was making some very small components out of brass rod on my lathe.  I used a centre drill to start the hole and after cleaning up the part I was disappointed to see the hole was not concentric! I did some research and discovered that the correct tool to use was a spotting drill and have used them ever since. They aren’t expensive so no reason not to use them. They are more durable than Centre drills as well so less likely to snap the end off - been there, done that a couple of times! 

Plenty of spotting drills on the Auction site.

[Doktor_Zeus]

Plenty of spotting drills on the Auction site.

I don't trust anything much bought on eBay, and it's oddly difficult to find affordable spotting drills anywhere else. Even the few available on Amazon seem to be shipping from China.

[Derek]

Have a look HERE just search for Spot drill

[Bill21]

I’ve not had any trouble with the auction site but Amazon have some as well. 

[Doktor_Zeus]

Looks like the main problem was the spindle retaining screw not being sufficiently tight, although I've not tried it again on resins yet, I did a test with some scrap wood today and it seemed to work fine.

[The Bowler Hatted Turner]

I would add that you should check and make sure you are using a good quality drill bit that has been sharpened correctly. A poorly sharpened fdrill bit will have a tendency to wander.

[Doktor_Zeus]

I think I have a process worked out that suits the lathe I use.

First, ensure that the quill retaining screw is fairly tight.

Second, loosen the tailstock and push it against the near side of the track - there's a bit of give in it from side to side that can shift the center, and this is the best contact point I've found for centralising the bit. Tighten up again.

Third, use a self-centring chuck and drill in half way from both ends to meet in the middle.

Fourth, never advance the quill more than five or six full turns of the handle during drilling. The further out it gets, the more off-center it gets. Once you get to the end of the fifth rotation, stop the lathe, wind back the quill and move the tailstock up until the bit touches the bottom of the hole, not forgetting to push it against the near side of the track at the same time, then start again. Not only does this mean you get less deviation from central, it also gives a good opportunity to clear the drill bit flutes of debris and let it cool a bit, which is vital when working with resins.

Fifth, when working on thinner holes and especially in resins, use a slightly smaller drill if you can (I'm using a 7.8mm drill for 8mm holes)

Sixth, if working on larger holes, center-drill first using a suitable bit. I don't have a spotting bit, so I use a stepped bit.

I'm trying to mainly use jobbing bits, as I've had problems with brad points, but I don't think that's necessarily important.

[John D Smith]

  Try using a Bullet point drill bit it works for me or start with an engineering centre bit Best of luck.

                                Regards John Smith