Need Advice About Lathe Collets

This is a good place to remind folks, especially those who have never used a collet chuck, that there is nothing magic about a collet chuck. It has the potential to hold a work piece accurately, yes, but the contact surface of any collet is rather small compared to a jawed chuck. The collet will hold the work solidly enough to resist cutting forces up close to the chuck but the farther you are from the chuck, the more the potential for deflection. This is especially true if you are using a carbide tool, which will deflect the work piece all by itself. (EDIT: Not fair; a HSS tool will deflect the work piece, too, but not as much as a carbide insert will.)

It is wise to extend the work piece only as far as you need to, and if that extension is greater than 1-1/2 to 2 times the diameter of the work piece then consider using a live center to support the work. This matters when the work must be held to close tolerances but it is also good workmanship if that is important to you. In fact, this advice also applies to a jawed chuck as well.

Deflection is a real thing and it has several sources, primarily the size and material of the work, cutting tool and the way we support the work piece. By supporting the work piece properly we eliminate one factor and minimize the effect of the other. When accuracy matters and tolerances are tight, do all you can to minimize deflection.
 
mikey said:
This is a good place to remind folks, especially those who have never used a collet chuck, that there is nothing magic about a collet chuck. It has the potential to hold a work piece accurately, yes, but the contact surface of any collet is rather small compared to a jawed chuck. The collet will hold the work solidly enough to resist cutting forces up close to the chuck but the farther you are from the chuck, the more the potential for deflection. This is especially true if you are using a carbide tool, which will deflect the work piece all by itself. (EDIT: Not fair; a HSS tool will deflect the work piece, too, but not as much as a carbide insert will.)

It is wise to extend the work piece only as far as you need to, and if that extension is greater than 1-1/2 to 2 times the diameter of the work piece then consider using a live center to support the work. This matters when the work must be held to close tolerances but it is also good workmanship if that is important to you. In fact, this advice also applies to a jawed chuck as well.

Deflection is a real thing and it has several sources, primarily the size and material of the work, cutting tool and the way we support the work piece. By supporting the work piece properly we eliminate one factor and minimize the effect of the other. When accuracy matters and tolerances are tight, do all you can to minimize deflection.
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Many collet designs will hold the part better then a scroll chuck while not damaging it in the process, I have spun a good deal of drills and taps in turret lathes yet have never spun a part in a 5C collet machine, Warner & Swasey push collets are bullet proof for the most part.

Also Swiss style lathes do the cutting far from the actual chuck through a bushing that rotates with the spindle with no clamping force, the bushing must have enough clearance to pass the stock without hanging up, it works. This of course requires round stock that has already been ground to size. A basic explination of how Swiss lathes differ from conventional machines may be found here.

http://todaysmachiningworld.com/magazine/how-it-works-why-swiss/
 
When I was in my young teens and working in my father's shop, 99% of the time the work was being carried out on collets. I will definitely pick some up in the near future, long before I get a 4-jaw chuck I think.
 
I would get the independent 4 jaw chuck first if I were you. Far more useful and accurate.
 
Depends on what you use your lathe for I guess. Can't remember the last time I used a 4-jaw chuck. It's been decades though.

Haven't even bothered to unpack the one I got with the 1340. YMMV... :)
 
mikey said:
Says the guy with an Adjust-tru chuck! :D
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Your right Mike. I do sometimes look at things from my perspective only.

If I DIDN'T have my PBA I would have to use my 4-jaw for barrel work, and any other operation that requires re-chucking a piece. Which is why I bought the set-tru. Hate using a 4-jaw... ;)
 
wrmiller said:
Your right Mike. I do sometimes look at things from my perspective only.

If I DIDN'T have my PBA I would have to use my 4-jaw for barrel work, and any other operation that requires re-chucking a piece. Which is why I bought the set-tru. Hate using a 4-jaw... ;)
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I hear you, Bill. I keep saying that my Adjust-tru just happens to have 4 jaws but I'm just kidding myself. One day I will own one, too. I tell you, you and Will (@darkzero) are really bad for my budget!!
 
Budget?!? What budget?

The nice folks here on the forums (darkzero being one...) blew my so-called 'budget' into the weeds years ago. :confused:

Truth be told, I'm actually glad they did. Now that the money tree is gone (early 'retirement') I can no longer afford any major purchases. The one machine I didn't get was a small surface grinder. Oh well, such is life.

With any luck, my PM machines will last longer than I. :)
 
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