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Collet or chuck for tapered workpiece thoughts?

bikemutt

Aluminum
Joined
Mar 5, 2022
I want to hold a tapered workpiece in a collet or chuck, preferably a collet. The taper is very slight, less than one degree but, it's there. The piece must be held straight. Many of these will be processed, I don't want to mess with 4-jaw anything.

I have one idea that has some potential, I think. I do have a reamer with the same taper as the piece, 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.

Or, maybe there's such a thing as a tapered work collet/chuck, or a floating jaw collet/chuck? I haven't been able to find such a thing.

Figured I'd ask the experts here to see if anyone has done something like this?

Thank you.
 
A 3-jaw chuck with replaceable and machinable jaws - machined to match the taper with a bit of a lip at front to hold things in? The lip probably not needed for just a one degree taper.
 
Can you tap the part into the tapered holder and then hold the other end with a little pressure from the tailstock, do your work and tap it out with a rod through the headstock?

Pictures of the part will get better answers.
 
A 3-jaw chuck with replaceable and machinable jaws - machined to match the taper with a bit of a lip at front to hold things in? The lip probably not needed for just a one degree taper.

I like that idea. I think I've seen soft aluminum jaws which would be easy enough to machine to fit.
 
Can you tap the part into the tapered holder and then hold the other end with a little pressure from the tailstock, do your work and tap it out with a rod through the headstock?

Pictures of the part will get better answers.

Unfortunately, the small end of the taper faces the tailstock.

I suppose though, if I could cut off a piece of MT3 and place it inside the spindle, it would act as a backstop so the piece doesn't back out.
 
You'd do yourself and your respondents a favor to post useful info on the part size and material, at least.
Critical details like will the taper locate the rest of the axial features, or will it be a straight shaft, etc.

The short answer is yes, 5c E collets and tooling fixtures are perfect for that sort of thing.
But i don't know if your part is larger dia than 5c in the spindle, or longer than makes sense in 5c extended nose pot chucks (collets) of larger dia with closers.

I do that sort of thing all the time, including one set up that holds 30 taper shanks in a collet to mod them in a DH to 30mm for my mill.

Also, what size spindle & taper is your lathe?

smt
 
Make the sleeve out of aluminum, leave a step on the front to keep if from driving all the way into the collet. Form the taper on the ID. Then take a woodruff key cutter and cut three or four slots along the side of the portion that goes inside the collet. Make the slots not go all the way to the ends of the sleeve, leave 1/8 inch or so unslotted at each end. Make the OD a good snug fit in whatever size 5C you want to use. When you snap the collet closer shut, it will grap the part inside the sleeve.

Best if the sleeve wall thickness is around 1/16 inch or so.
 
With no part sizes or overall shape given then it's an impossible to properly answer question. Can it be done between centers? Before the independent 4 jaw, 3 jaw scroll chucks or even collets were invented everything larger than watch maker parts got done either on a face plate or between centers. For really tough and odd shaped parts then face plate fixtures, mandrels and/or with tail stock support were used. Chucks and collets aren't the only part holding methods, or even the most accurate.
 
OP says the small end of the taper will experience some axial force, so I suspect there's drilling, tapping etc. that would preclude turning between centers. Additionally, centers require more time to change parts (fitting the dog, etc) and dogging some tapers might be problematic. Probably not 1deg though.
 
A picture of what you are trying to hold would really help. The easiest way to hold that would be to cut the blank long, grip on the extra material, then part off to finish.

I have in the past made a fixture for parting off .223 brass to make .300BLK. I drilled and reamed a piece of aluminum to the size of the base of the brass and put a cross pin as a stop for the base of the brass. I turned the outside leaving a step the amount that the .223 case tapered and a larger step to stop off the 3 jaw for my length. I then split the fixture like a collet so it could flex. I actually works pretty well.

Screenshot 2022-05-11 075858.jpg
Screenshot 2022-05-11 080024.jpg
 
Now that we know that the large end of your tapered part faces the headstock - which you didn’t mention until your third post - the collet or custom chuck jaws suggestions will work perfectly. Assuming that you machine the collet or chuck jaws only to a certain depth, or use a stop to limit the depth of the workpiece, they will hold. Tapered tooling or workpieces have a tendency to work loose under side loads, but yours can not.

We’re still guessing about the size of your workpieces and the specs of your machines, though, as well as the precision needed in the process. So I’ll suggest finding an old telephone pole that will fit through the spindle of your oilfield lathe, using an adze to hollow out a taper from the side, and fitting a plug that will be compressed by one of your chuck jaws to hold the part. Should work just fine.
 
If you have no other way to make the slits (such as a slitting saw on a mill) you could drill relief holes in 3 locations where the end of the slits would be and cut them with a hacksaw. You'd need to carefully de-burr the holes and slits. For repeatable work you'll need an end stop and I'd suggest incorporating a screw to eject the parts after machining with such a small taper.

You can spot the hole locations by carefully marking at the tips of the chuck jaws. In use you'll rotate it so the slots are midway between the jaws and one spot should be marked where the # 1 jaw will go so it is always mounted the same way. Ream the taper with that spot under the # 1 jaw and you should get good repeatability.

Sequence:

Turn the outside shape.

Mark the hole locations and spot drill only. Don't drill through yet.

Locate the index mark at the # 1 jaw and bore and ream.

Finish drilling the relief holes and slot from the edge to them.

De-burr and use.
 
Per sleeves. I use them routinely too, in larger deep pot chucks to save expense. :)

As well as in other collets for odd ball work.

Jim R is correct about leaving a shoulder on a sleeve that will not seat to the bottom of a pot chuck/collet, or have a back stop. But i differ on how to slit them. For aluminum sleeves, just bandsaw in from one end to within maybe 1/4" or 3/16" of the other end (2 slits formed in one cut, 180 deg apart) Then saw from the other end at 90 deg to the first set, same distance from the first end. Use a triangular file to de-burr the slits inside and out.

If the workholding tool will be expected to last for hundreds or thousands of parts, then it might be worth sacrificing (spending for) a regular E collet to the job. The ones from Hardinge are even hardenable; and could be ground, post heat treat.

OTOH, if the fat end of the taper really does go in the chuck first, then you will have to use a sleeve. I like 4140 prehard as being convenient to machine, grinds well, too, and is hard enough to run for a long time as a precision insert.

smt
 
Anything is really just conjecture without a better part description. A sketch is great. Also number of parts being made. High production probably requires a more elegant solution than just a few.

But it does sound like a spring collet won't work though unless part is very short because not enough clamping motion to swallow the big end.

I slit lots of collet sleeves with a hacksaw. You can do a reasonable job and all you need is a slit.

1* taper is slow so shouldn't push back unless you really pound it.
 
A lot would depend on how accurate the original part varies in size compared to the machining that needs to be done.

Knowing the part and what is needed would help to think about the advice.

A straight bore, perhaps 1" ID and then a reverse taper solid collet(no slits) perhaps .999" DIA.. with a screw on collar nut at the out end might work to take the part to stop at the back end. The solid collet made using the taper reamer.

One thow clearance to the sold collet would make it run very close.

Put the part in the collet, then put that assemble into the dead end bore, and add the end cap nut.
 
We’re still guessing about the size of your workpieces and the specs of your machines, though, as well as the precision needed in the process. So I’ll suggest finding an old telephone pole that will fit through the spindle of your oilfield lathe, using an adze to hollow out a taper from the side, and fitting a plug that will be compressed by one of your chuck jaws to hold the part. Should work just fine.

That's hilarious, thanks!

The piece is about 1.5" long with an outside (tapered) diameter of about 0.5".
 
The piece is about 1.5" long with an outside (tapered) diameter of about 0.5".

Perfect fit and app for a 5c E collet.
Or, if fat end does go in chuck first?
A regular 1" 5c collet, a rear stop, and a 1" OD sleeve with the internal taper bore.

If skinny end goes in first and taper is aprox MT or similar, it can be held to a stop, with care in a taper bore to suit. If taper is more obtuse than MT, some sort of draw bolt, shoulder catcher, or nose closer might be useful to retain it for axial cuts.

smt
 
Perfect fit and app for a 5c E collet.
Or, if fat end does go in chuck first?
A regular 1" 5c collet, a rear stop, and a 1" OD sleeve with the internal taper bore.

If skinny end goes in first and taper is aprox MT or similar, it can be held to a stop, with care in a taper bore to suit. If taper is more obtuse than MT, some sort of draw bolt, shoulder catcher, or nose closer might be useful to retain it for axial cuts.

smt

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 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.
 








 
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