Suggestions for fixturing part while maintaining runout

edward.santos · Nov 26, 2018

So I have a part with the feature I've sketched out. Its pretty much complete, other than I need to drill the 1/4" hole on the left side.
I'm trying to think of a way to hold this part. Ideally it would be in a 4jaw as the outside of the part is rectangular. An expanding collet might work, but that 1" ID has a very fine surface finish, so I'd rather not touch it. There is also another 1/3 of the part not shown to the left that would make me feel uneasy about just holding that 1/2" on the ID
The problem is the runout tolerance. After mounting the part I have no way of indicating that ID.

You guys always seem to have some novel ideas.
Its also made of 304 in case you're wondering

jims · Nov 26, 2018

It would be easy to hold with an expanding collet. I have held thousands of parts that way with no damage to the finish. Runout should not be a problem. Go too you tube and look at Rovi ID collets . They are made in Calif. It would load in seconds if you are doing a lot of them.

litlerob1 · Nov 26, 2018

I'm assuming you want to do this on a Lathe. I would use a dead center in the head stock, and some copper or brass shims on the 4 jaw/s. You could also build a plate that attaches to the face of the chuck with a boss on it, to locate the 1" ID.

This is why 1st operations need to be well thought out. Give yourself a couple Tenths on the runout form OD to ID there, then you don't need to worry about it on the 2nd op. I woulda Drilled it all the way through for the 1st op though.

Were it me, I might Mill a round boss on a plate and use push clamps to hold it. And do the work on a Milling Machine. Dial in the Boss, then dial in the length of the part parallel to the Z-axis. If it were less than 20 parts.

R

Wlodek · Nov 26, 2018

Turn a spigot that fits closely the bores on the other end and leave it in the chuck. Push your part over the spigot with cement. I use solid shellac stick that I melt on the part wile the part is warm and hardens when cool. One can use 5 minutes epoxy as well. Drill and bore your hole and then apply heat (with a heat gun) to soften the shellac or the epoxy. The nice thing about shellac is that it softens at low temperature of about 100C and is easy to clean with alcohol. I often use shellac to cement odd shape parts on the lathe or mill. "Shellac chick" is a standard accessory in watchmakers lathe, but work well on bigger parts as well.

gbent · Nov 26, 2018

Make the diameter inside -A- to be true to -A-. Then use that diameter to hold your part.

michiganbuck · Nov 26, 2018

Perhaps a brass plug for going into the 1" bore,that Plug being set in a 4 jaw so to indicate true..driven with a dog to the OD.. the out end in a steady.. with a boring bar to start the 1/4"

QT:[ as the outside of the part is rectangular.} yes would have to know that runs good to the ID so set in a steady it would still run true.

QT:[There is also another 1/3 of the part not shown to the left] that changes everything.

QT:[The problem is the run-out tolerance.}If that +- .0005 then could you simply run it in a OD holding collet

or light press a guide bushing into the 1" ,, fixture the part and gun drill or drill and ream from the 1" end.

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Suggestions for fixturing part while maintaining runout

edward.santos

Plastic

jims

Hot Rolled

litlerob1

Diamond

Wlodek

Aluminum

gbent

Diamond

michiganbuck

Diamond

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