Author Topic: Easy vaccum fixture for the mill.  (Read 2730 times)

Offline 90LX_Notch

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Easy vaccum fixture for the mill.
« on: January 04, 2013, 04:38:06 PM »
I'll start off by saying this worked moderately well.  I didn't take pictures when used the fixture a couple of weeks ago.  The pictures are from today for this post.

I needed to mill .062 thick aluminum to .035 thick on a small rectangle .375 x .594.  I already had the length and width machined when I realized that the milling machines vice wasn't up to the task.  Soft jaws would have worked but the part probably would have sprung and I'm not set up for soft jaws anyways.  I decided to make a simple vacuum fixture.

It's just a squared block with a blind .250 dia hole drilled down the center length ways.  Three tiny port holes are drilled to intersect the .250 hole.  The open end of the .250 hole was tapped for a 1/8 pipe thread and a simple fitting was turned up.  The vacuum was supplied by a MightyVac handheld vaccum pump.

A smudge of grease was applied over the ports to ensure a good seal.  This is not enough to hold the part in place for milling, it slides around.  I wound up making some fences with close fitting notches out of .015 aluminum flashing and clamping them down.  It worked and I was able to successfully machine .028 off of the part.  The part came out perfectly parallel.  However, the notched fence did not securely hold the part. The part slid slightly during milling but it never lifted due to the vaccum.  I believe that an L shaped fence at each corner of the part would solve the sliding.

-Bob

 
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Offline kellswaterri

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Re: Easy vaccum fixture for the mill.
« Reply #1 on: January 04, 2013, 05:55:12 PM »
Excellent idea Bob.
                           John.

Offline Mosey

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Re: Easy vaccum fixture for the mill.
« Reply #2 on: January 04, 2013, 06:45:56 PM »
Love it...gonna make'm!

Offline Don1966

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Re: Easy vaccum fixture for the mill.
« Reply #3 on: January 04, 2013, 06:56:37 PM »
Isn"t it amazing how the mind can come up with a way to do something. Nice work up Bob.

Don

Offline 90LX_Notch

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Re: Easy vaccum fixture for the mill.
« Reply #4 on: January 04, 2013, 11:41:21 PM »
Thanks guys.

If you make one, test it on scrap first.  As I mentioned above, the part did move when I milled it due to clearance in the notches of the fences.  The part definitely needs to be captive at the corners.  When I machined it I had 25" of Hg.  You have to watch the gage to make sure that the vaccum holds while the part is machined.  I started with .005 cuts and did manage a .010 cut. 

Some design notes:  The ports are counter sunk so that they can be plugged with wax* if need be in the future.  When the need arises, I will drill two more .250 dia holes parallel to the existing one and drill additional ports.  The .250 holes will be linked by a manifold. 

*Electrical tape also works well for sealing any unused ports.

-Bob
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