A little trouble with my collet chuck

[Jeremy]

I'm having some issues with my PSI collet chuck. I turn the blank round, down to 5/8, and when it comes time to put it in the chuck for drilling I have one helluva time getting it to stay straight when tightening, or even getting it straight in the first place. It keeps ending up with me tapping it repeatedly while the lathe spins at 250 RPM until the hole from the dead/live center is the least "blurry" I can make it.

I figured the tolerances for a collet chuck were so tight it would pretty much be "slip in blank, tighten, drill". What am I screwing up?

 

[Daniel]

I don't have the PSI chuck. I have two Beall chucks and one from 800 watt on ebay. every one of them are a stick it in and it is center sort of deal. One thing I am thinking is are you certain your are getting it turned "Round"? if your head and tail stock are not aligned it will turn an oval rather than round.

I do know that I have drilled over 500 50 cal bullets with my collet chuck and all but a hand full where very close to dead center to the point of the bullet. The outside surface of these bullets are not necessarily smooth either.

I would also suggest you make sure your collet is seating well in the chuck. that is a common problem

 

[Jeremy]

My head and tail stock are perfect, amazing really. I just got a Delta 46-460 last Friday. I'll check the collet seating, thanks.

 

[ldb2000]

As Daniel said , check your blanks . Even just a little bump anywhere along the blank will cause the problem you are having . I use a 3/4" open end wrench to check my blanks when I turn them round (5/8" would work just as well) . Start at one end and turn the blank to final size keeping it a snug fit to the wrench all the way along . Any under or over turning will be very apparent as you go along .
When you put your blank in the collet bring your tailstock up and use it to center the blank as you tighten up the chuck . If it was turned and centered and is perfectly round this will keep it lined up on the center axis of the turning .

 

[johnnycnc]

I'll say you may not have the collet seated properly. There is a groove on the collet,
behind the opening, on the side..goes all the way around.
That groove needs to be seated in the nut you screw/unscrew, inside it.
It may or may not pop into that groove, but that's how it has to go.
If it is not snapped in place, and you just put things in, you'll have exactly the problem you describe.
Try popping the collet in the nut, and hold the collet somewhat in place, put your blank in, then hold that kind of all together, and install that on the chuck body.
When you remove blank, just unscrew the nut enough to get the part to release, not all the way.
This is normal, by the way. I use collets everyday on my job on the cnc.
Hope this helps you!
John
♠

 

[jskeen]

I"m with John on this one, it does seem logical that you would slip the collet into the chuck, push it back till it's snug then put the cap on, but that's definitely not going to work. Instead take the nut off the chuck, put the collet in so that it's crooked, but one side of the groove in the collet locks into the cap, push a little to snug it in so it (hopefully) won't fall out, then tighten onto the body of the chuck. It will straighten itself out as it seats. This ensures that the collet will release the workpiece (or usually the cutter shaft) when you loosen the cap.

 

[PaulDoug]

Also make sure your chuck is clean. No debris in threads or the grove the collet seats in.

 

[Sylvanite]

How deep into the chuck are you sliding the blank? The more bearing surface between the collet and blank, the better (and squarer) it will hold. The deeper you seat the blank, the less runout will be exaggerated at the end.

If you can move the end of the blank by tapping on it, then the chuck is not holding properly.

Regards,
Eric

 

[Jeremy]

Thanks, somewhere between all the suggestions the problem is resolved.

 

[johnnycnc]

Good!
That's a pretty nice chuck. I have that and a Beall, and would not want to be without them.

 

[larryc]

I"m with John on this one, it does seem logical that you would slip the collet into the chuck, push it back till it's snug then put the cap on, but that's definitely not going to work. Instead take the nut off the chuck, put the collet in so that it's crooked, but one side of the groove in the collet locks into the cap, push a little to snug it in so it (hopefully) won't fall out, then tighten onto the body of the chuck. It will straighten itself out as it seats. This ensures that the collet will release the workpiece (or usually the cutter shaft) when you loosen the cap.

I'm confused here. I tried this method and I couldn't get the collet to seat.

The instructions for the Beall Collet Chuck states, "To use, first fit the collet into the nose nut and then insert the whole assembly into the chuck body. The nose nut is equipped with a small internal flange which must fit behind the groove cut near the top of the collet. The chuck is so designed to allow the collet to be pulled easily from the chuck when the nut is unscrewed, preventing it from becoming jammed.
When properly installed the front of the collet should ne nearly flush with the front of the nose nut."

 

[PenMan1]

First, take a 5/8 maple dowel (the maples here at HD are much more consistent than the oak) cut it to 5 1/4 inches. Roll the dowel on a flat surface looking for "wobbles" . If a wobble is found keep cutting until you get a dowel piece with no wobble. Put the dowel in your chuck. If the machine made dowel spins true at slow speeds, the problem is with you rounding technique.

If rounding technique is the problem, try rounding another blank using a 5/8 open wrench as a caliper. As others have said, a small "divot", etc will cause out of concentric.

If the dowel does not spin true, remove the face of the PSI chuck. Look for dirt, dings, gouges, etc. Clean it and then try a 3/4" machined maple dowel in the same holder with the 3/4 ER 32 collet. If this spins true. The problem is likely the PSI chuck face.

First, you must find out which piece of the configuration is the ememy, before you can fix it. The technique described above will help you do just that.


Addendum: particularly with the PSI chuck, make SURE to fit the collet with blank inserted to the chuck FACE first looking for consistent "seating" of the collet all the way around the chuck face, then attach face, collet and blank to the collet body....NOT THE OTHER WAY.

 

[johnnycnc]

Short video;
http://youtu.be/xrqjoJCFoTU

Thought this might help explain putting the collet in the nut.. it's a little tough with just words!

just a quick offhand shoot.

John
♠

 

[jskeen]

Short video;
http://youtu.be/xrqjoJCFoTU

Thought this might help explain putting the collet in the nut.. it's a little tough with just words!

just a quick offhand shoot.

John
♠

That's what I was trying to say Thanks John

 

[leaycraft]

John- Thats what I thought you meant and yep it does make a difference doing it that way on a PSI chuck. Would not have thought it would but concentricity is improved.

 

[PaulDoug]

Thanks John. I have not been doing it exactly like that and now I well. Some times I have to play around with to get things seated correctly because I've been doing it with the body mounted on the spindle. Seeing it always makes it easier to understand for me.

 

[johnnycnc]

Thanks everyone! it was a really unplanned video, so it's pretty rough as far as that goes. as long as it works!