Lathe Collet Closer

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Originally Posted by

The Tormach has (2) 120V controlled outlets in the back of the control cabinet. One is for the coolant pump and one is for the collet closer. There's a button on the screen, for each, to toggle them on and off. There are also M codes for a program turn the coolant on and off. I haven't found the M codes to have the program turn on and off the collet closure outlet, yet. I've sent Tormach an asking, but haven't heard from them.

Not even the suppliers of best quality ER collets will provide a guarantee, of specified parameters, for anything but the nominal size &#; certainly not the minimum achievable.

Hobbyists are not generally absolute perfectionists to absolute sizes &#; as may be required for series production of replacement parts for high precision machines. I use ER &#; and also a Clarkson occasionally.

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Maybe viewing some of those REGO-FIX videos first would have turned up the information that less than nominal sized tool shanks, or in our case when there being used as a work holding collet, they show no increased run out, and they will in fact guarantee those same guaranteed run out numbers over the holding range of the collet. At least REGO-FIX does. If an ER collet and it's chuck are correctly and accurately made, the collets segments will close down evenly against the tool shank, in fact there designed to do exactly that and provide the high grip strength ER collets are known for. So why would smaller than optimal diameters be any different than on size diameters since the collet has to close at least a bit even with on size tool shanks? My Bison ER 40's show no increase in run out over the various sizes I've checked. When I want holes with a high degree of location accuracy, or I'm using large diameter reduced shank drills, I'll use them instead of a drill chuck, so I can also use mine as a tool holder with a variety of sizes within each collets closing range. That ability is simply due to the radial and axial precision the collets and chucks are being made to, and what I think can be assumed adds a high percentage to the actual cost for those better collets and chucks. There's also more than a few YouTube videos that show cheap off shore ER collets having visually noticeable differences in segment widths, differences in slot widths, burrs etc. Since the collet isn't and can't close evenly around it's full circumference, then of course it will produce higher run out numbers even "if" it was bored and ground true to it's tapers. And if there being made that poorly, then it's highly doubtful anything else is correct other than by pure luck. There's also videos showing collet chuck thread deviations and nuts with internal tapers that are out of square enough to force the collet sideways or physically tilt the collet axially as the nut is tightened. So it's not only the concentricity of the collets themselves, it also has a lot to do with just how accurate the collet blocks or chucks are as well.

5C is completely different because of how there designed to work. That design of collet isn't meant to accept anything over sized, and even a bit too far under size will or can crack or break collet segments if the collet is closed on any smaller than optimal diameters. Since a 5C collet is a single taper and closed by drawing the collet inwards against the collet holders taper, that forces the collet segments to exert the most holding power towards the front of the collet. For that reason, special soft 5C over sized collets can be machined and used even for very short parts. If 5C was being used for driving tools, then yes nominal sized collets to fit the tool shanks diameter would be logical to obtain the highest grip. Possibly there still being made somewhere, or at least were at one time. But other than those now fairly rare machine tools that were designed to use 5C, I can't recall seeing any actual 5C milling chucks. About the only option left would be to build your own if that's what you really wanted to use. As a tool holder, I think 5C is a rather poor second choice.

ER collets are a dual taper, and the segments at each end are forced in and closed by both the chuck and closing nut tapers as it's tightened to the correct torque. For that reason it's highly recommended that at least 80% (or more) of tool shank, or work piece fills the collet length. If that's not done, then the collet's grip is seriously decreased and a collet can be permanently damaged because the tool or part is then only being gripped by the front of the collet. Run out numbers will then increase, but that's the fault of the user because there being used improperly and outside there intended design application.

It's also not about being a perfectionist, and as I already said, those REGO-FIX videos clearly explain just how detrimental any excess run out is to maximum tool life no matter what collet type or tool holding method is used. And since the ER collet design has a decent amount of closing range when holding work pieces, you can be quite sloppy about those exact sizes as long as the part length is inserted deep enough into the collet. 5C collets would require much more attention to those nominal diameters than ER's ever would. Like anything else, there's no perfect one size fits all when it comes to tool and work holding collets. 5C is logically the clear winner as a work holder just due to it's versatility. ER is a much better and far more secure tool holding method because of it's grip ability over the length of a tool shank.

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