Best Workholding Method?

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Andre

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Sometime soon, I'll be making 12 subframe bushings for a Volkswagon R32. The AWD VR6 version of the fourth gen Golf. They will be made from most likely 6061 aluminum, and I would like some input on how to hold them once parted from the bar. I will turn the Min OD, Max OD, face, bandsaw from bar then remount backwards to face the back. I would like some advise on how to mount them backwards.


I would like to stay away from gripping the Min OD, as the part could easily become marred from the jaws. My Skinner 4 jaw doesn't have jaw caps, so no soft jaws can easily be made without a CNC or photograph. I have some ideas, but I would like some input from some of you guys who've done this before.

4x 4" dia and 8x 3" diameter.

Here is a picture of similar products for reference.

mk4ssfb.jpg
 
Build an expanding stub arbor with a sholder. Drill & tap the arbor for NPT, then slit the arbor, 2 slits at 90 degrees apart with a hack saw. Screw in a pipe plug to expand inside your part.
 
JimDawson said:
Build an expanding stub arbor. Drill & tap the arbor for NPT, then slit the arbor, 2 slits at 90 degrees apart with a hack saw. Screw in a pipe plug to expand inside your part.
Click to expand...

Thank you, Jim! I do happen to have a 1/4 NPT and I could use an air fitting as a plug......
 
Like Jim said, mount them on an arbor. Except, us an adhesive - makes for a very simple arbor.

Consider doing the ID and one face of all of them. Then make the arbor (I assume you are working with only one lathe) so the bushings are a slip fit. Do not remove the arbor from the machine (assuming you have it in your 3 jaw chuck - then it will remain true to the accuracy of the machine). Secure the bushing with Loctite (if you use the primer, it will have good strength in a matter of minutes). Then machine the OD, apply heat to release.

Let us know what you work out.
 
I had to make a few part that looked a lot like yours from aluminum, and like you, I just wanted to face the back side. I did not want to glue them on with Loctite since I would have to either heat on the lathe or remove the arbor to heat. I considered using a pipe tap and plug, I have the tap, but no plug.
I just made an arbor in the 3jaw with a tight slip fit. I then put a light straight knurl on the arbor so that the part would slide up the shaft and onto the knurl. I used a file on the knurl until it took a light tap with a mallet to get it on the part about 1/8". Then I trimmed the arbor back to length for facing. My parts where new hubs for my 8" grinder, so they where something like 2 1/4" in diameter, and needed to be very square to the axis.

It worked like a charm, and left no marks on the aluminum. Just don't get carried away forcing it up onto the knurl, and make light cuts - it will not spin. If you do not chamfer the ID before flipping, you could make the knurl a bit fatter and then chamfer off any marks by hand or on the mill.

On another job, where I had to turn the outside diameter. I made a spigot arbor in the 3jaw, and just put a socket between the live center and the work and used pressure from the tail stock to hold it in place. Worked fine for aluminum, but would probably not work for steel.
 
my friend makes some parts that don't have a hole, they are about .100 thick, he parts off about 20 of these from bar, then he holds them in a 5c step collet, that is bored about .050 deep and grips the od, then turns a cone on the end, its a cnc lathe, but still, the cutter gets about .020 away from the collet face to do the operation, he does short runs of this product so the step collet was needed, that way he can setup more of a production, first parting 20parts, then facing 20 parts, then putting the cone on all parts, because they are separate programs he had to swap them out and do each op to all parts.
collet.jpg
 
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I have rolls of 1 1/2' wide emery of different grits in the shop. What I do is tear a strip the with of the small dia. and rap 1 rap with the abrasive side out and chuck it in the 3 jaw. Holds tight and doesn't mar the piece.
 
joshua43214 said:
I had to make a few part that looked a lot like yours from aluminum, and like you, I just wanted to face the back side. I did not want to glue them on with Loctite since I would have to either heat on the lathe or remove the arbor to heat.
Click to expand...

Joshua raises a good point. When I'm heating a piece in the lathe (or other delicate location), I find a heat gun gives better control than some other options.
 
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