IAP Houston, I have a problem....

[Warren White]

I think I might know the problem (which probably exists between my own ears).

The issue is that when I was drilling some acrylic on my lathe, I heard more noise than I was used to. I thought it might be that the acrylic was a bit harder than it had been in the past.

Well, the outcome wasn't pretty. As you can see in the photos, the entry hole is fairly good. The exit hole is much larger than it should be.

I think I may have neglected to tighten the tailstock quill lock handle. Does this sound like a reasonable reason for the result I am seeing? Any other suggestions? The bad thing is that I drilled a number of blanks, painted the inside, waited a few days and then epoxied the tubes in. As a result, I have three pens and two perfume holders that are a bit messed up.

I will let you know how this turns out, but in the meantime, could I be on the right track?

Thanks,
Warren (the perplexed and unhappy)

 

[Dale Allen]

Warren, if you had any vibration when drilling the unsecured tailstock quill could easily be the issue. I've done that and immediately stopped and checked the setup and found that to be the problem.
I'm wondering about the pictures you posted. Is one of them the entry hole? If so, it seems that both ends have issues. Maybe your drilled hole is supposed to be that much bigger. I know many will tell you the hole has to leave room for the glue. I try to keep mine real close to the tube size. I figure that when I glue and clamp 2 pieces of wood together making a cabinet, there is very little room between there for the glue and it holds just fine.
When drilling on the lathe and the drill bit is not perfectly in line with the blank or it is moving off center while drilling, it will never turn out well.
Imagine that the back of the stock is moving in a larger circle than the front and it is moving in such a way that it is wobbling. It is doing this in reference to the drill bit that is not aligned with the stock. Under that situation there is no way you will get the holes the same on both ends.
I center drill and turn all my blanks round before drilling and they are turned to the same diameter all the way along the length. When I put the blank in the scroll chuck, I make sure it is turning true to center using a dial indicator.
Typically the blank is cut somewhere in the middle and the end where the drill bit is going needs to be smoothed and I make a small dimple in the center with a round scraper. That lets the drill bit end get a perfectly centered start. I advance the bit with the tailstock quill very tight so there is no chance the bit will walk. Only when the bit has gone past the outer flutes do I ease up on the quill.
When doing this I must hear and feel absolutely no vibration the entire drilling time. I use short advances and retract the bit, vac off the shavings and cool the bit and blank with the vac. On some acrylics I use veg spray lube. I only use standard jobber bits but not the really cheap ones.
Typically I get a .002" variance from front to back because that is how much runout is in my lathe headstock. And from what I have observed that is better then many new lathes out there.

 

[Cmiles1985]

If you don't mind, could you walk me through your drilling process?

Locking the quill would insinuate that you are pushing the tail stock by hand to advance the bit through the material. That will allow the bit to wobble making for a sloppy hole.

What I consider to be a reliable practice is to lock the tail stock, and advance the quill using the handwheel into the blank: slow, and about 1/4 - 1/2" between completely withdrawing the bit to clear the swarf.

 

[Warren White]

Well....

...I didn't think that one through very well, did I?

I just went out to the lathe, and of course Clark was right on target. I of course did not lock the quill so that I could advance the drill using the tailstock handwheel.

I still think the tailstock/chuck was the issue, and most likely the tapered drill chuck was not sufficiently tight within the morse taper. I just tried another blank (wood this time) and was careful to assure that the drill chuck was tightly held in the morse taper. When i was through, both the entry and exit holes were exactly the same and were the right size. I guess I just got careless; you know familiarity breeds complacency.

Thanks for all who looked at this and didn't shout out WHAT AN IDIOT! THAT CAN'T BE THE PROBLEM. STAY AWAY FROM SPINNING MACHINERY!

Oh, well, back to the garage.... I mean shop.

Thanks again!
Warren

 

[Cmiles1985]

Enjoy making some more pens

 

[Warren White]

Dale,

I was so embarrassed regarding my lack of thought in my post that I didn't properly respond to your outstanding post. I did appreciate the time you took to help me understand what might have been going on.

As I indicated, I think you are right on. The improperly secured tailstock (or rather the tapered drill chuck) was most probably the issue. I jumped right to the material I was drilling rather than stop and listen to the little voice in my head. In answer to your questions, the entry hole was much better than the exit hole. In fact, I went ahead and finished one and it worked out all right, but the second was a disaster. I drilled the hole with the size drill bit recommended for the project. I suspect the oversized hole was a result of the slop in the chuck/taper.

I liked your suggestions for making sure the drill bit is centered. I don't understand how you turn the blanks before drilling. Could you "'splain that to me, Lucy?" (A rather vague reference to I love Lucy...sorry) Does that mean you drill them all to the 7mm mandrel size and then drill those that need a larger center after turning? I think my method of holding the blank needs the shoulders on the blank since I use a PSI Pen Blank Drilling Chuck, but I would welcome your thoughts on that.

I had't thought of using vegetable spray on acrylics. What brand do you use?

Again, Dale thank you. I really appreciated your response.

Warren

 

[Dale Allen]

OK, some of that was probably not clear enough. :biggrin: Such things always need some clarifications when I write them.
The tailstock is locked down with extra force so it won't move. The quill lock is tightened 'almost' to the point the handle will not advance the chuck. I say almost because it takes a bit of force to turn the handle and advance the bit. Yes, I am putting wear on the parts that is not normal. However, this is understood and has not caused any damage that prevents the quill from normal use. I do this to be sure there is no way the machine can vibrate or cause the bit to go off center. I advance it extremely slow at first and have done this many times and get the same good results.

As for the rounding of the blank. I use a center bit at the dead center of the blank ends and turn it between centers to get it round all the way along the length. It is important that it is the same size everywhere so that when I put it into the scroll chuck jaws it can be adjusted to run perfectly true to center. Usually it is just a matter of a slight tap in one direction to get it running true. Any wobble from true center will cause the bit to start off center and vibrate...not good.

The pen blank drilling chucks can still be used as you will be bearing down on the rounded blank instead of the corners. In my experience, I have never found a blank that was exactly the same width both directions and perfectly square. That seems to be the ideal condition for the pen drilling jaws to be able to get the blank turning at dead center. My method assures me the blank is uniform round all over the length.

Hope that helps.

 

[Warren White]

Dale, all of that makes sense....

....thanks for the explanation.

I will have to try your suggestions.

Best wishes once again,
Warren

 

[dartman]

I was so embarrassed regarding my lack of thought in my post that I didn't properly respond to your outstanding post. I did appreciate the time you took to help me understand what might have been going on.

As I indicated, I think you are right on. The improperly secured tailstock (or rather the tapered drill chuck) was most probably the issue. I jumped right to the material I was drilling rather than stop and listen to the little voice in my head. In answer to your questions, the entry hole was much better than the exit hole. In fact, I went ahead and finished one and it worked out all right, but the second was a disaster. I drilled the hole with the size drill bit recommended for the project. I suspect the oversized hole was a result of the slop in the chuck/taper.

I liked your suggestions for making sure the drill bit is centered. I don't understand how you turn the blanks before drilling. Could you "'splain that to me, Lucy?" (A rather vague reference to I love Lucy...sorry) Does that mean you drill them all to the 7mm mandrel size and then drill those that need a larger center after turning? I think my method of holding the blank needs the shoulders on the blank since I use a PSI Pen Blank Drilling Chuck, but I would welcome your thoughts on that.

I had't thought of using vegetable spray on acrylics. What brand do you use?

Again, Dale thank you. I really appreciated your response.

Warren

Dont be embarrassed Warren,we have all done things like that. Now go
and make some spinney things

 

[TonyL]

Every 20 to 30 barrels that happens to me. I fill the void with thin or med CA, and turn it, To date, I never had an issue with the hardware meeting the outside of the barrel material. I wish I could tell you why I haven't had a problem, but I don't know.