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What is the correct procedure for boring out an emergency collet?

I've noticed that the threads and back bearing on the collets are being damaged and have to be replaced. What's wrong?

What's the advantage of buying a collet kit?

Why purchase master collets & feed fingers?

Why buy a hardened & ground collet?

Why not buy a bargain collet?

When should I use an emergency collet?

Can I use 5C collets in a 16C spindle?

Is there an adapter that lets me use my 5C collets in the 16C spindle?

Can I use my style S master collets in my CNC lathe? Will threaded collet stops help me hold lengths?

 "What is the correct procedure for boring out an emergency collet?"
"Insert the collet in the spindle with the draw bar in the full open position. Make certain that all the pins are in the face of the collet or step chuck. Adjust the collet closer until closed on the pins and then back off 1/8 to 1/4 of a turn. Do not back off enough to where the collet angle is not fully seated in the spindle. Lock the draw bar in this position. Decrease the chucking force as much as possible (do not use the same force you would to grip the part). Close the collet. If you can pull the pins out, you should increase the chucking pressure until the pins cannot be removed. Rough and finish the bore to the chucking diameter of the part. Remove the collet and debur it. Thoroughly clean the spindle and then remount the collet. Adjust collet closer for proper gripping and the correct draw bar pressure to hold the workpiece."


 "I've noticed that the threads and back bearing on the collets are being damaged and have to be replaced. What's wrong?"
"Vises, Vise-Grips and pump pliers are the cause of your problem. Purchase several Collet wrenches for each style collet in your shop (5C, 16C, 20C, etc.). This wrench is keyed and locates over the back bearing of the collet to hold it while the threaded stop, Dead-Length assembly, etc. are being tightened into the collet."

 "What's the advantage of buying a collet kit?"
"Hardinge offers several different kits for various types of collets. For example, the 5C, 16C, 20C, and 25C collets are all available in kits of varying quantities. The advantage is that you'll have every major size available to you for any job that may come to you. And as an incentive to you, we price the kits so that the total cost of the kit is 5% less than if you bought the pieces individually. Why not buy a set for your tool room today?"

 "Why Purchase Master Collets & Feed Fingers?"
"Why purchase Master Collets and Feed Fingers rather than Solid Collets?" "While the initial investment will be slightly more, the advantage of achieving more versatility at a lower net cost assures the user of a profitable return. Master collets and feed fingers are capable of holding and feeding bar stock in a variety of sizes and shapes by using interchangeable pads. Thus, the same workholding tool can be used for more than one job to reduce tooling cost, provide greater flexibility in operation, and save on storage space."

 "Why buy a Hardened & Ground Collet?"
"These collets have a head angle and bore that are case hardened to 60 - 63 Rockwell. They will give you the maximum life possible. The bore is precision ground and guaranteed to have a TIR of .001" or less. Special accuracy collets are available that are guaranteed to have a TIR of .0002". Before investing in a special accuracy collet, check your standard collet - they usually have a TIR of .0005" or better."

 "Why not buy a Bargain Collet?"
"A bargain is possible because something has been compromised. The head angle and bore are not in the 60+ Rockwell range. The back bearing of the collet is not held to precision size and concentricity tolerances. The bore, head angle, back bearing and thread are not all concentric with each other. Because the collet is softer than a Hardinge collet, it will wear very quickly. A precision hardened and ground collet can last for years."

 "When should I use an emergency collet?"
"When should I use an emergency collet?" "The emergency collet is a life saver. Its used when you need a collet bore to run as close as the spindle's TIR because it is bored in place in the machine's spindle. It is also used when you only have a few hundred parts to run and you don't have the proper size hardened and ground collet. Remember that the head angle and the collet bore are not heat treated on emergency collets and will wear quickly under heavy or long use. The rule of thumb for the life of the bore and leaf tension of an emergency collet is 300 to 500 pieces. The threads are heat treated but the leaves of the collet are not spring tempered. This results in the collet leaves losing their elasticity. Eventually you will not be able to put the part in the collet because the leaves have lost their tension."

 "Can I use 5C Collets in a 16C Spindle?"
"Is there an adapter that allows me to use my 5C Collets in the 16C Spindle?" "Yes, there is a 16C-to-5C collet adapter which accepts 5C collets. This is a good purchase if you have many 5C collets and few 16C, but there are limitations. The major one is concentricity. Because of the number of parts in the assembly, the TIR is greater than .002". It also takes about 15 minutes to change a collet with this adapter. Adapters are available for 20C-to-16C or 25C-to-16C."

 "Can I use my Style S Master Collets on my CNC Lathe?"
"If you're doing bar work, they work very well. The Style S Master Collet system was developed for use on multi-spindle automatic bar machines where collet runout is of very little concern. Secondary work on CNC machines usually requires very good collet concentricity, usually better than .001" TIR. Style S TIR could be as high as .004" to .008", therefore making them unacceptable for secondary work. In an emergency, there are emergency pads which will work. Once you remove them, however, their TIR will be unacceptable if you try to run the same job again."

 "Will threaded collet stops help me hold lengths?"
"If the diameter of the part being gripped is held to a very close tolerance, the answer is yes. Unfortunately, the stop is attached to the collet, which draws back with the draw bar. For every .001" variation in the chucking diameter, the collet will draw back or stick out .003". The main purpose of a collet stop is to eliminate the push-back of the part while it is being machined, or to automatically eject the part when the collet is opened."

Jones and Shipman Hardinge Limited
Murrayfield Road
LE3 1UW, England
Tel: +44 (0)116 2013000
©2013 Hardinge Inc. All Rights Reserved.
Hardinge is the leader in providing a wide range of highly reliable turning, milling, grinding and workholding solutions under the brands Hardinge, Bridgeport, Kellenberger, Hauser, Tripet and Tschudin. We never compromise on product design, so customers can count on Hardinge to help them make the right part to the required specification, every time.