Holding small parts

I volunteered to fix a bunch of older Vemco drafting machines (elbow type)
for the local high school. A frequent fault is that the graduated base
plate can no longer be clamped by the "Protractor Brake". Said brake is
simply a thin piece of aluminum with a shoulder that pinches (clamps) down
on the protractor. It is approximately the size of a nickel and about as
thick. I successfully filed 0.007 inches of one side, however, it is a
difficult task freehand and removes a lot of skin from the fingertips.
If it weren't aluminum, I would simply place it on my magnetic chuck.
One thought I had was to carve a recess into a block of wood and use that as
a work stop. An advancement would be to drill a hole into said block of
wood and use either my vacuum pump or mighty-vac to hold the part down.
Could also make in impression in a chunk of clay, but SWMBO says it would
take at least 24 hours to fire in her huge kiln.
Other ideas appreciated.
Ivan Vegvary
Reply to
Ivan Vegvary
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See my clamping suggestion from a day or two ago for Bob's cut out coins.
Reply to
Pete C.
super glue to steel. surface grind, heat part with propane torch to remove.
Reply to
Karl Townsend
And after it was fired, the part wouldn't fit - clay shrinks when fired.
Thin (not thick and foamy) double-stick tape might do perfectly well, if the parts are clean and flat. The superglue already suggested would also work. If the part is prone to creep during filing despite the tape, a couple of stops to catch the edge of the plate might be all the help it needs.
Hot glue is yet another option. Fixturing alloy would be another.
Reply to
How about making aluminum soft jaws for your milling vise with a shallow horizontal vee notch in the top edges, or a few dowel pin holes?
Reply to
Jim Wilkins
Paste wax an area on your mill table, and one of the subject parts with a good heavy duty paste wax. Mold release wax is premium, as sold by fiber glass venders.
Lay the part down on the side you wish to machine.
Lag the part up with body filler, or tooling plastic. Modeling clay can be used if necessary to stop the plastic from getting under the part in areas that would trap and lodge the part in the cured plastic mold.
Upon hardening, gently clamp the mold as is, and machine the back flat with well used tool. Body filler and tooling plastics are most often very abrasive.
Flip it over, clamp it down, and machine the part.
Pop out the part, replace with another, and repeat.
Reply to
Elliot G
Mount it on a wooden dop with sealing wax then either clamp that or work freehand with a decent handle. Heat to release. Might need a few brass panel pins with their heads just lower than the surface of the part round the edge to resist lateral forces, but it's gotta be easier than carving a pocket and wax will clean off easier at a lower temperature than superglue. I've lapped dozens of copper seal washers I annealed for reuse that way last time I rebuilt a diesel.
Reply to
Machine a pocket in a 5C emergency collet to hold the part and face off the part in your lathe.
Reply to
Tom Wait
on 3/12/2009, Ecnerwal supposed :
Agreed. I've had good luck with double sided sticky and light cuts.
Wayne D.
Reply to
Thanks everybody!!
I decided to try the thin double sided tape idea first. (BTW the part is not round so some of the replies would not work). Milled a thin slot across a 1" x 0.1" piece of aluminum. Slot depth approximately 0.025" deep. Simply enough to give me a shoulder against which the part will abut while I push the file. Used thin scotch brand double sided tape. Worked like a charm. Merely sliding the file across 4-5 times, I removed almost 0.010 material. Was shooting for 0.007±. Very fast. Takes longer to find the end of the scotch tape than to complete the project. It surprised me that I could even file backwards, whereby only the tape was holding the part i.e. no shoulder for the part to rest against.
Ivan Vegvary
Reply to
Ivan Vegvary
Lapidaries grind and polish rocks freehand. They use dop wax.
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Reply to
Don Foreman
Hey Ivan,
Glad it worked out for you. Me??? I had no idea what to do!!! BUUUTTT.... I do hope to catch at least one of the NAMES SEMINARS in mid April which would seem to be of interest to you and many of us:
Take care.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXX
...>Thanks everybody!!
Reply to
Brian Lawson
friend of mine polishes facets on glass chunks (up to about 50lbs apiece) by embedding them in a puddle of paraffin, using a vibrolap, then gently heating them up to get the paraffin off.
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