How do you align a blank in the collet chuck?

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Carl Fisher

Carl Fisher

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This may sound like a stupid question, but I'm going to ask anyway.

So I took a blank, made it round between centers and then sunk it about 85% into my Beal collet chuck to drill. When I drilled and removed the blank, it was so far off center on the exit side I ended up tossing the blank.

I've also tried drilling first and then using a punch in the tail stock to keep the blank nice and true but once I tighten the Beal down and give it a spin by hand, all that does is wobble the tail stock around...so that's definitely not true.

So when dealing with drilling, then ultimately tap and die operations where you may have to remove and re-install the blank in the chuck a few times, how to you keep it running true in the collet each time when tightening back down? Or do you just have to keep adjusting by trial and error until you find the sweet spot where everything runs true again?

Is there a proven method to get everything lined back up between operations so that you can continue where you left off after removing the blank?
 
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If the blank is truly round and the chuck is seated properly, it should center every time. Test it with some metal round stock first to see if that turns true. If it doesn't something else is wrong. With drilling on the lathe, use some centering bits to start the hole before you drill.
 
I'll have to hold a straight edge to the blank and see if I'm truly the same diameter down the full length of the blank. I may not be since I'm turning down almost to the point of finished diameter before drilling and tapping. I'm starting to think I'd be better off to drill through and drill/tap before turning down as that way I'd at least have the finished center line in place before turning.

I do drill on the lathe exclusively for my normal kit pens but that's typically from either square or rough rounded stock in my pin jaws of my 4-jaw chuck and being true center is not an issue in those cases. I can be off by as much has 1/8" and still make the blank round.
 
I use a four jaw chuck to hold the square blank and drill then turn, it can be a little off because the square blank may not be straight but I have never ruined a blank drilling this way.
 
Thanks but we may be veering off the intent of the question.

It's not really the drilling that I'm questioning, it's the removing and replacing the blank into a collet chuck while keeping the center line always true.

I think Bruce may be on to the solution in that my rounded blank may not be the same diameter all the way down the length allowing it to skew one way or the other inside the collet. I hadn't thought that all the way through really and just took someone kicking me down the right path.
 
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I'm having the same trouble. I've got a Nova chuck. I don't put any of the jaw inserts in, just put what ever I'm working on straight into the jaws. I have 2 very precise machined pieces, one out of delrin and one is metal and I still have trouble seating them both perfectly. I have to try several times to get it right and even then it might be off a hair which causes issues with what I'm working on. This is not for pens, it's for doing some pool cue joint protectors. If it is a bit off center, it doesn't sit right on the cue joint.
 
Carl Fisher said:
Thanks but we may be veering off the intent of the question.

It's not really the drilling that I'm questioning, it's the removing and replacing the blank into a collet chuck while keeping the center line always true.

I think Bruce may be on to the solution in that my rounded blank may not be the same diameter all the way down the length allowing it to skew one way or the other inside the collet. I hadn't thought that all the way through really and just took someone kicking me down the right path.
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Carl,

I always put calipers on my blank if I turn it down by hand. I normally use my metal lathe though to turn it down. A straight edge may not be accurate enough.

Bruce is right though. If your blank is not the same diameter all the way down, it won't go in the chuck straight. Do you have multiple sizes of collets or just a few. It could also be that if your collet is not the right size that may also be part of the problem.

Do you put the collet in the chuck and slightly tighten and then put your blank in the chuck? Or could your collet not be seating all the way?

Just some more thoughts.....
 
Carl, I find that when I need to put a blank back in the collet chuck, I put the 60 degree live center in the tailstock and put just a bit of the blank into the chuck. As I advance the tailstock, I tighten the collet holder. When I get to the depth in the collet I need, I finish tightening the chuck up - otherwise, it is hard to re-chuck the piece where it runs true.
 
Lots of good feedback and some things to try.

I wish I had a metal lathe to really true up, but alas I'm only as accurate as my hand-eye coordination will allow :) Calipers are always on hand but the straight edge would tell me how wavy I am.

I do have the full range of imperial sized collets from 1/8 through 3/4. Typically I will put the collet and nut on before inserting the blank and slowly tighten hand tight and then a touch with the bars to snug it up...not too tight.

I do know I have been able to do a nearly perfect drill in the past on a piece of ebonite that was already round when I bought it. I needed to open up a 12.5mm hole with very little to spare around the edges and it actually turned out well...but the difference there was factory rounded vs my square to round sizing.
 
I use a dial indicator to find the point where the blank(turned round first) is running dead center. I have one mounted on a a mag base that I quickly set on the bed and turn the chuck by hand and either bump the end of the blank or re-position it until I get it as close as possible. Yea, this takes extra time but I get a good straight drill through. As said before, it is important to get the bland the same diameter all along the length. I use a dial caliper for this when I turn it round between centers.
 
I too use calipers to check the blank for the same diameter or as close as possible. Then use a straight edge such as a rule's edge to see that there are no drastic dips. Usually after one or 2 of these you can see by eye. If you are using a collet chuck why not just put witness marks on both the chuck and match them to the blank. So if you put the blank back in just line up the witness marks. I do this all the time with larger blanks and using a 4 jaw chuck.
 
What's funny is that I do witness marks with my 4-jaw lining up back to the numbered jaw with a mark on whatever I'm turning, but never thought to do that with the collet chuck.

I'm planning to do a few things tomorrow to see if I can iron it out. I also discovered that I was putting the collet incorrectly in the body. I was putting it in the body first and then running the nut up to it. Well thanks to the library article I found out that I needed to seat the collet in the nut first and then in the body. So I think I was actually getting uneven clamping pressure on the collet.
 
I also discovered that I was putting the collet incorrectly in the body. I was putting it in the body first and then running the nut up to it.
Click to expand...


That'll do it – You've solved your problem completely!
Your chuck will improve immediately


Best wishes and regards,
[FONT=&quot]John[/FONT]
 
I just noticed this thread. My first question was how you are mounting the collet in the holder. I think you have identified your problem, and will be well on your way.

Have fun.
Rich
 
It's crucial to have the blank turned between centers to a consistent diameter the entire length (level). Use the calipers while turning between centers and not a straight edge. Your measurements along the blank should be within .1 mm. For instance, these would be acceptable measurements at five places along the blank: 14.17, 14.07, 14.15, 14.06, 14.09.

It's especially important that if the blank is to be turned around in the chuck and rechucked, the blank must be level from end to end.

I use a Wood Chuck carbide cutting tool with replaceable cutters that have a 2' radius and have little difficulty getting a blank level. I wouldn't want to have to do it with a spindle gouge. Once the blank is level and in the collet chuck, I find I can drill holes that are perfectly centered every time.
 
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