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5c 1-1/8 collet with no internal threads

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kf4zht

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#1
Does such a thing exist and who makes/sells it. Trying to do some semi production stuff with a threaded section, then a clampable section, but the threads hit the ID threads before there is enough to grab on to.

I can attempt to turn the threads off the collet but wanted to see if someone sold them that way for the larger sizes

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Bob Korves

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#2
5C collets will only pass 1" through the bore, at least as designed and usually manufactured. 5C collets over 1" diameter have a step inside that necks them down to around 1" deeper in the bore. But you no doubt know that, other readers of this may not. The necked down section comprises more of the collet length than just the threaded portion, on mine well more than half of the collet is at 1" and only 1 to 1-1/4" is opened to 1-1/8". Collets are also hardened, and so will be difficult to open up the inside diameters. The spring slots will also cause problems. They will be difficult to machine unless you can grind them in a O. D. fixture that holds them externally and also supports the spring sections. Even it that is accomplished, residual stresses in the steel that become unbalanced with the re-machining could very well make them warp. So you might get it done, but still not achieve a decent work holding solution. If you attempt it, please let us know how it turns out. I suggest finding a different way to hold your work...
 

dlane

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#3
A pic would be good ,but they make emergency collets that can be machined but still not 1 1/8 thru
 

mksj

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#4
As other have mentioned, 1" is the maximum size that will fit through a 5C collet, and even stock that is a few thousandth over will not pass. The minor diameter of the 5C outer thread is ~1 1/8" so enlarging a 5C collet would not work. You would be better off using a 4J independent with some shim stock between the bolt and the jaws. Otherwise you could consider and ER system, the maximum size for an ER-40 collet would be 1.125" and ER-50 is 1.25", so that could be an alternate solution and use an ER-40 or 50 collet block held in your 4J.
 

kf4zht

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#5
5C collets will only pass 1" through the bore, at least as designed and usually manufactured. 5C collets over 1" diameter have a step inside that necks them down to around 1" deeper in the bore. But you no doubt know that, other readers of this may not. The necked down section comprises more of the collet length than just the threaded portion, on mine well more than half of the collet is at 1" and only 1 to 1-1/4" is opened to 1-1/8". Collets are also hardened, and so will be difficult to open up the inside diameters. The spring slots will also cause problems. They will be difficult to machine unless you can grind them in a O. D. fixture that holds them externally and also supports the spring sections. Even it that is accomplished, residual stresses in the steel that become unbalanced with the re-machining could very well make them warp. So you might get it done, but still not achieve a decent work holding solution. If you attempt it, please let us know how it turns out. I suggest finding a different way to hold your work...
That was part of what stopped me from just trying it. However I am building a toolpost grinder to fix an old 3 jaw chuck, so I may give it a shot. The advantage I have is the threaded section is 1.090 MD, and I only need another .250 or so depth. If I try it I think I'd have a a better chance.

As other have mentioned, 1" is the maximum size that will fit through a 5C collet, and even stock that is a few thousandth over will not pass. The minor diameter of the 5C outer thread is ~1 1/8" so enlarging a 5C collet would not work. You would be better off using a 4J independent with some shim stock between the bolt and the jaws. Otherwise you could consider and ER system, the maximum size for an ER-40 collet would be 1.125" and ER-50 is 1.25", so that could be an alternate solution and use an ER-40 or 50 collet block held in your 4J.
Unfortunately the operation is putting wrench flats on it using a collet block in the mill, so it isn't just chucking it up. It would require me purchasing a dividing head or rotary table, chuck for that, etc. Thanks for the idea of an ER50, been thinking about making a collet chuck for the lathe anyway and that might be an option.
 

Jimsehr

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#6
When I made up a lever collet set up for my 11 inch Logan with a 2 1/4 8 dia spindle nose I held the collet tube 1.375 dia in a Jacobs collet chuck which fit the spindle. I had to mount the collet chuck on a face plate so that I could bore and thread the collet tube to fit the 5c collets. There is a Jacobs collet chuck on eBay right now with most if not all the collets neaded to hold stock from .125 dia too 1.375 dia. It is a buy it now for about $225 dollars and about $20 shipping. It is such a good deal I would
Buy it myself if I didn't already have 8 collet chucks.
Jimsehr
 
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