Collet or chuck for tapered workpiece thoughts?

[eKretz]

I must be missing something. I agree that a straight sleeve bored to a taper, slit, and held in a collet or chuck would be a good way to hold this workpiece. But, if the OP is making enough of these parts, a collet or soft chuck jaws bored to fit the taper would be even better. Depth could be controlled with an adjustable stop, or the collet or chuck jaws could be taper bored to a fixed depth only.

It seems to be that the large end of the taper faces in, so there's no way to do that with a collet without leaving the back end open. Soft jaws yes, collet no. However, we still don't know if OP has a chuck with available soft jaws... Regardless, simpler proposition to make a quick sleeve and split or slit it. Don't need a machinable E-collet for that either. If there are hundreds of parts on a repeat basis, something more permanent might make more sense.

 

[michiganbuck]

If we knew more about the part and work needed that would help. The 1-degree part's Od taper would be a self-locking taper.
It may be possible to use a 3/4" round stock and with that held in any chuck for machining/makimg a tube-type taper ID holder

Stock 3/4" x 3 (or what the OP figures the length after reading this post.

Skim the OD of the tube type holder to run true (perhaps .748), then drill it (well centered), then ream it with the ops taper reamer, Parting-tool part it off at a length suitable to allow 1/8" of the part big end sticking out.
Now cut off the small end of the tube with having a taper Id, so it allows 1/8 " part's small end to stick out (for knock out).
This tube holder would be set in a 3/4" collet so the part's small end is pointing out toward the tail when in use. This taper tube holder would have no slits, just a straight Od with a taper ID.

The part would be tapped into the tapered ID tube for a taper fit holding...and it(part in tube) put into a 3/4" collet with the small end facing out and the machining would be performed.
When done the tube holding the part would be taken out of the collet and the small part end tapped on a brass block to release the (taper fit holding)part from the tube.

Some fineness (Trial and try) to obtain the correct amount of tap in, so the tap out will work.

* if the Op thinks the machining of the part would be too much for the holding he could make the taper ID tube holder by having a stop-screw to at the big ID end of the taper tube holder.

Sich a holder tube could also be set on the reamer(if the reamer has centers)so the tube OD could be run/turned between centers for a near-zero accuracy.

Such a holder could be made from a 1" stock, and set between centers to turn down to 3/4".

it could be made of 1" stock if the Op's lathe can hold a 1" collet.

This tubetype holder would use/go into a standard straight collet.

 

[JohnMartin]

A collet does not have to be bored clear through - all that is needed is a small hole to allow the jaws to collapse. A step collet. No reason why the step could not be used to register the depth to which the part is inserted, which to me is the simplest solution - it’s one piece. Not the two-piece solution of a sleeve within a collet or chuck.

Of course, it all depends on the numbers. What collets his machine will take, and what holding depth he needs for his parts. If it’s a 5C collet and he needs to do some heavy work at the small end of the part, he may find his part needs to extend back into the freebored section of the collet - and would therefore require a separate stop to locate it. Although an extended nose emergency collet might do the trick.

Collet or chuck, sleeve or no sleeve, built-in stop or separate stop. Lots of options, and it’s pretty hard to give him good advice without knowing more.

 

[rons]

2 cents:

When difficult situations arise here I sometimes turn to wood to help hold my children.

 

[eKretz]

^^^ THIS ^^^

Your part has a taper already less agressive than several well-known "driving" taper standards.

Under reasonable tool loading, so long as soundly seated (deadblow) it will JF stay in the socket until driven out.

No need for splitting the holder to make a "spring" collet atall.

No, not unless he's got a stop behind it. He already mentioned that he'll be applying some axial force against the small end of the taper while machining. That will push it out, almost certainly. Using a sleeve in a collet or soft jaws it can be completely captured, and will also be more positively and repeatably located in the Z axis. But I'm in the camp that there are a million ways to skin this cat.

 

[bikemutt]

That's what I was thinking. I've done this plenty of times. The tapered ID sleeve can also be made as one piece then just sawed completely in half if you don't have a slitting saw. No real need for slitting. The ID of the collet and the surface of the part contacting the sleeve will hold it in perfect alignment as long as the sizes are hit pretty close.

I tried something a while back where I clamped together two square pieces in the vise and center reamed down the contact surfaces, once done, the slit was accomplished by simply removing them from the vise. It was one of those moments when I couldn't figure a way to get there from here, so I started from there and worked backwards. It worked great in that application.

 

[bikemutt]

Regarding work holding, it's either 3-jaw, 4-jaw or ER, I do not have a 5C.

 

[michiganbuck]

3 or 4 jaw the part accuracy will change with each change of the next part.

Collet held likely also to change a little perhaps 2 to 5 tenths depending on the quality of machine and collets.

 

[michiganbuck]

I will change my post 22 to say leave the big end of the tube a 1/2 inch long, so to decide if the taper fit tap-in will hold the part strong enough to machine the part.

That extra 1/2 inch will allow a screw at the end to hold the part in the tube, from being pushed out by the work being done at the small end.

 

[bikemutt]

I will change my post 22 to say leave the big end of the tube a 1/2 inch long, so to decide if the taper fit tap-in will hold the part strong enough to machine the part.

That extra 1/2 inch will allow a screw at the end to hold the part in the tube, from being pushed out by the work being done at the small end.

I'm thinking along the same lines.

Part of this is knowing the tolerance of the work end, which is where you identified it's location. It's unspecified and may be unworkable using this approach.

 

[michiganbuck]

So with that, the holder would/could be a straight OD that fits a large non-altered collet.
A tapering ID that fits the part and allows the out end to stick out enough to do the work needed.
At the left holder-end is a screw that will push/hold the part in the taper.

if there is any widening shape of the part near the big end of the ID taper then a counterbore may suffice that feature,

Having the screw will also set the length if a gauge block is used to measure the stick out from the collet.

The tube holder may be made with an OD step-diameter if a controled part length stick out or accurete length measure is required, or a gauge block can measure the amount of the part sticking out.

The tube holder should be made very accurately OD to ID. Perhaps running on a mandrel, between center or what best you have method.

Care taken so the screw does not push the part too tight and so lock it in beyond removal.

 

[bikemutt]

The tube holder should be made very accurately OD to ID. Perhaps running on a mandrel, between center or what best you have method.

Care taken so the screw does not push the part too tight and so lock it in beyond removal.

Since the work end is a straight tube, I've got an inside work holder on order, it's a shanked pull collet with a radial actuator so there's no need to pull from the blind side of the work. The collet is designed to be machined to fit a specific work piece I.D.

I'm still going to pursue the tapered holder, and I like your idea for the screw, thank you. Even if I cannot use it for machining, it may serve a valuable metrology purpose.

 

[michiganbuck]

Post a photo of your shanked pull collet along with a photo of the part. It sounds interesting.
Buck

 

[rons]

I thought about reaming a hole in a piece of round stock, turning it down to a thin wall, then cutting a slit longitudinally, sort of like a sleeve. The sleeve can then be chucked, light pressure will hold the workpiece inside the sleeve. I need to have the extra holding force because the small end of the taper will experience some axial force, I don't want it popping out of the sleeve until I'm done with it.

I have no idea how I'd make the slit, nor if it would work the way I think if I was able to make the slit.

2 cents more:

Have you thought about reaming the hole in something like plastic. Tap the part in the hole.
Drill a hole on the small diameter side for an ejector pin.

 

[bikemutt]

I've thought about using plastic. The problem there, I think, is durability, It's going to be repeatedly holding and releasing parts internally, and being squeezed, albeit gently, by a collet externally. Having worked with various types of plastic in the past, nothing jumps out at me as being a good fit here.

 

[rons]

I've thought about using plastic. The problem there, I think, is durability, It's going to be repeatedly holding and releasing parts internally, and being squeezed, albeit gently, by a collet externally. Having worked with various types of plastic in the past, nothing jumps out at me as being a good fit here.

I'm not sure of your dimensions ans ops during mounting.
But a Morse taper on a drill chuck shank is the same idea.