Is there such a thing as an emergency collet for ER style collets? I've been looking on the Googles but I haven't found anything yet. I don't have a need for one yet, it was a shower thought this morning. I've used soft 5C collets before when I was student help in a shop 30+ years ago and learned that they can be a really valuable tool when making small "production" runs but I'm not seeing anything in the ER space.
Kevin
ER Emergency Collets
Re: ER Emergency Collets
Can you come up with a plausible situation in which you would need one?
5C soft collets are useful if you need to grip something that is outside the range of your standard set (by 1/32" or 1/64" or 0.5mm). ER collets have a wide gripping range per collet, so as long as you have all collets in the set, they will cope with all diameters (standard and metric) in the range of the particular ER series.
As a practical matter, 5C soft collets have just three frontal slots in them, normally held from collapsing when boring by three pins. ER collets collapse both at the front and the back, and have multiple slots, so it would be difficult and expensive to provide pins at all the points of flexure.
Within each ER series, the back end of an individual collet varies according to its nominal gripping diameter (a 3mm ER32 has a lot shorter grip length than a 20mm ER32). How would a soft collet cope with this?
There are quite a few options with ER collets (the RegoFix catalogue is well worth flicking through; near the back of it is shown cross sections of the collets, illustrating the rear end details) but soft ones are not one of those options.
If we really wanted to be hardball about it, ER collets are strictly speaking tool holding collets only. The whole wide world uses them for workholding in addition to toolholding, but if confined to their proper use, the need for emergency collets is just not there.
5C soft collets are useful if you need to grip something that is outside the range of your standard set (by 1/32" or 1/64" or 0.5mm). ER collets have a wide gripping range per collet, so as long as you have all collets in the set, they will cope with all diameters (standard and metric) in the range of the particular ER series.
As a practical matter, 5C soft collets have just three frontal slots in them, normally held from collapsing when boring by three pins. ER collets collapse both at the front and the back, and have multiple slots, so it would be difficult and expensive to provide pins at all the points of flexure.
Within each ER series, the back end of an individual collet varies according to its nominal gripping diameter (a 3mm ER32 has a lot shorter grip length than a 20mm ER32). How would a soft collet cope with this?
There are quite a few options with ER collets (the RegoFix catalogue is well worth flicking through; near the back of it is shown cross sections of the collets, illustrating the rear end details) but soft ones are not one of those options.
If we really wanted to be hardball about it, ER collets are strictly speaking tool holding collets only. The whole wide world uses them for workholding in addition to toolholding, but if confined to their proper use, the need for emergency collets is just not there.
Re: ER Emergency Collets
I suspect not. Because tightening the collet is important for gripping power, without a load on the collet it would be difficult to machine. They also rely on their heat treated condition for memory, so they retain their intended size reasonably well. As I understand it, the increased flexibility of the ER series allows for use beyond a nominal size so you most likely can use a collet that will fit the size you hope to hold.
The shape of the ER collets isn't new. Such collets were commonly used previously, although split only in a few places. They lacked the flexibility of the ER types and could not be used beyond their nominal size. They also were known for breaking at the slits, leaving one with more than one piece.
Key to the success of the ER type collet is that they are double angled collets. They close at a constant rate, so the gripping surfaces remain parallel. That's very different from the 5C and R8 type collets, each of which have but a single angle. When they are used beyond their nominal range, the collet doesn't grip parallel. When the difference is extreme, the collet will grip only at either the front or rear of the opening, depending on whether the work piece is under or oversized. That offers the opportunity for the work piece to oscillate in the collet and to create grip marks.
H
The shape of the ER collets isn't new. Such collets were commonly used previously, although split only in a few places. They lacked the flexibility of the ER types and could not be used beyond their nominal size. They also were known for breaking at the slits, leaving one with more than one piece.
Key to the success of the ER type collet is that they are double angled collets. They close at a constant rate, so the gripping surfaces remain parallel. That's very different from the 5C and R8 type collets, each of which have but a single angle. When they are used beyond their nominal range, the collet doesn't grip parallel. When the difference is extreme, the collet will grip only at either the front or rear of the opening, depending on whether the work piece is under or oversized. That offers the opportunity for the work piece to oscillate in the collet and to create grip marks.
H
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: ER Emergency Collets
When I was learning to machine all those years ago, I had to machine a step and concentric bore in a couple of hundred steel washers. What the experienced machinist showed me was cutting a profile in an emergency 5C that held the part square, at the correct depth and allowed me to burn through the job a heck of a lot faster than I though I could. The job could have easily be done with a set of soft jaws but we had a stash of these 5C collets (and I ended up making a bunch more later) and I got to learn a new skill/tool.
I hadn't thought about the fact that a profile on the face would not provide anything for the rear of the collet to "grip" on so yeah, there's probably a reason these don't exist. Like I said, this was just a "shower thought".
Thanks
Re: ER Emergency Collets
…and there is nothing fast about opening and closing ER collets in comparison to a 5C lever actuated collet closer for lathe production work.
Glenn
Operating machines is perfectly safe......until you forget how dangerous it really is!
Operating machines is perfectly safe......until you forget how dangerous it really is!