I get a lot of inquiries asking, “how much expansion can you get from our expanding collets”? Most expanding collets that are activated by a screw pulling back into the front taper of a collet will only have a maximum expansion of .010”. The reason being, if the collet is expanded beyond .010”, you will experience what we at Rovi call “flowering of the collet ”. Flowering is when the collet is expanded to the point that the Expanding Collet will not go back to its original position once the screw is released to unclamp the collet.
If you flower the collet, you will not be able to load the next part on the collet. This is because the stress induced in the material will not allow for it to settle back to is original diameter, thus making it over-sized and not allowing for your other parts to slide onto the collet.
However, if the Expanding Collet is made from a material that is heat treatable such as 4140 or 4130, you will be able to get a little more expansion out of the collet (.011”-.015”). The hardness introduced into the collet with heat treat has made it more rigid and able to retain more memory in the material.
If you do require a collet that needs to expand beyond the .010”, we do offer a system in which the collet is expanded on both ends by being pulled onto a shaft that has a taper on the front and back side. This style collet has an expandable range of .015”. They are a little more costly, but do work well. Need more info? Do not hesitate to contact us to go over your specific applications. 800-423-5145.
Click on the following link for more info on Expanding Collets: Expanding Collet Page