How to hold this part?

[PixMan]

True, the opposite end needs to be finished, my bad.

I do think getting both threads done in one op is good. Cut it off from the inside, flip it around and do the finishing of the opposite end on an expanding arbor that would be faster to make than soft jaws, if one has the slitting saw needed.

I'd first make the mating male taper solid plug with a hole to run the bolt through. Then, fashion a close-fitting arbor with a female taper in the end and a tapped hole through, slit the body for expansion. Don't even remove the arbor from the chuck, just slide the part on and crank the plug in tight. Now the part is firmly held and perfectly concentric.

[Harold_V]

True, the opposite end needs to be finished, my bad.

I do think getting both threads done in one op is good. Cut it off from the inside, flip it around and do the finishing of the opposite end on an expanding arbor that would be faster to make than soft jaws, if one has the slitting saw needed.

Wrong again. I can set up soft jaws and be running parts before you can turn the expanding arbor and move to the mill for splitting. You also don't have need to make a tapered piece and hope for the taper to match another. You enjoy the added bonus of not having the tailstock in the way.

Those of us that use soft jaws routinely don't make them for a job---we have existing jaws that are near the requirements and select them accordingly. I can generally grab a set of jaws and have them machined to my requirements without removing any more than about ten thou of material. I have soft jaws that have been in service for many years. It clearly is not a slow process. In fact, I often use soft jaws for a one-off item. They tend to solve all problems, not just a select few.

Harold

[Mid Day Machining]

Harold is right. Softjaws are a quick way to go, but you will need to use pijaws to keep from crushing the part out of round.

[Torch]

Another method which I have used on similar situations is make a
snug fitting S.S. coupling with a land type back stop machined into
one end, and matching threads to your small piece on the same end.

I used to make similar home-made nipple chucks for threading close and shoulder pipe nipples. They work well, producing pieces every bit as usable as a commercial clamping type nipple chuck. I'm not sure why you are specifying SS though? I used to use a piece of heavy- or extra-heavy-wall pipe with a running thread inside a steel coupling leaving 3 threads for gripping the nipple (mind you, they were tapered pipe thread. More might be better for straight thread).

[ken572]

Torch,

The only reason's I used 316 S.S. was because they were very hard
to wear out, and they didn't transfer any contaminate's into the pore's
of the softer metals and plastics.

Ken.

[Torch]

The only reason's I used 316 S.S. was because they were very hard
to wear out, and they didn't transfer any contaminate's into the pore's
of the softer metals and plastics.

Makes sense -- particularly if contamination of soft materials is an issue. Of course, the OP can simply use the same aluminium stock that he is making the part from if he's just making a few of them.

[Hot Brass]

I've decided to get an expanding mandrel and give that a shot simply because it is the cheapest option right now. Moving forward I'll buy a chuck with 2 part jaws so I can learn how to make and use soft jaws.

[scooterwrench]

I''m no expert but what I've done is to turn a recess in my jaws .100 deep by .060 out wit a slight negative chamfer(dovetail). The reason I did this was to bore the ID of flat washers but it's quite useful for holding parts like you've designed there. I'll send pics if you need. Hope this helps save you some deniero. J.

[kapullen]

I would make a clamp plate with a neat fit in the bore, and a clamping area 1/16"
wide to clamp the part on your faceplate with a screw thru the headstock.

A plug to fit the rear of the headstock with a hole, the draw screw size would help.

No face plate, You could clamp it on your 3 jaw in the ID, and use the jaws to lightly center the part.

No worry about out of round conditions here.

Kap Pullen

[scooterwrench]

I''m no expert but what I've done is to turn a recess in my jaws .100 deep by .060 out wit a slight negative chamfer(dovetail). The reason I did this was to bore the ID of flat washers but it's quite useful for holding parts like you've designed there. I'll send pics if you need. Hope this helps save you some deniero. J.

Here's those pics.

[Harold_V]

That's interesting! What you did is how soft jaws are applied, with the difference being soft jaws are easy to machine.

Would you be wiling to discuss the actual cutting of the jaws? While I realize they can be machined, they don't lend themselves well to the process, due in part to their hardness, where an interrupted cut makes the task all the more difficult. Looks like you got good results.

Harold

[scooterwrench]

I chucked a wrist pin out of a harley so that it was 'bout .150 back from the front surface of jaws, used a C8 cemented carbide tool,kicked in the back gear and slowly fed it out by hand so as not to let it bang hard. This is the second chuck I've done this to. First one was a chinese made, which came with the lathe. This one is a czech made chuck that is very high quality. I always use wrist pins to check the truness of my chucks,you can't find a truer or harder piece of round anywhere else.