Milling a plate square?

[Blink-]

Hey guys, I've got a general machining question.

I have a plate of material, 3/8" thick, about 5" x 5", how can I square up the edges. I do not want to machine the sides which the thicksness is measure, just the edges.

I was thinking about it earlier, and if I could get 2 edges square, then I could mount it flat, on parallels then just use the side of the end mill to square up the other edge, but the problem is getting the first two square and parallel, any tips?

[Mcgyver]

if there are any holes or cut outs, do them first and clamp through the work cutting all four edges in the same set up, or

clamp to the table with parallels, use at least to clamps. mill two parallels sides, then one at a time move the clamps so you can access the other two sides, or

if the table is too small to do this, you have to rotate the piece 90 degrees after cutting the first two sides. now you have to align the cut edge to the axis of the machine. this is readily done, but you need an indicator. mount the indicator in the spindle. Move the work by taping it under slight clamping pressure unit when you run the indicator along the cut edge the reading on the indicator stays the same

[Blink-]

Thank you very much for the reply. I hadn't thought about just clamping it to the table on paralles, that is a great idea, and is what I think I'll do, or try that is. Sure will be a pain in the ass having to set the work true with the spindle each time I rotate it. Oh well, can't be any worse than setting up the mill and vise regularly.

I will try that and let you know how it goes.

Will

[ViperTX]

Well....hopefully you'll use a shell miller when you do it with clamping to the table setup and do you have enough y-axis travel?

....with a 5"x 5" piece I generally use a L shaped angle plate....mount it to the table....and clamp the workpiece to the angle plate...I use a face mill to mill one face, rotate it 180 degrees and mill the opposite edge.....I then use one of the milled edges to align the workpiece to the angle plate....clamp it securely and mill the third face...rotate 180 degrees and mill the last face.

[Blink-]

The angle plate sounds intriging, and less labour intense. However, the plate I am trying to cut is plastic (Acetal), and I am worried about it flexing, causing chatter. Hence the reason I don't want to clamp it upright in a vise, and have 3" above the jaws. I'll have to check what sizes of angle plate are availible, maybe a 4".

Y asix tavel is no problem, it is a full size Bridgeport mill.

Edit: Shell miller?

[Geof]

Cut two pieces of 1/2" ply the same size as your plastic, put one on the table the acetal on this, the other one top and clamp from the sides. Of course the part is lined up as true as possible to the table.

Mill both edges that are parallel to the X axis to get your finished size in the Y direction.

Get two more clamps and now clamp front and back edges; remove the first two clamps.

Mill both edges that are parallel to the Y axis to get your finished size in the X direction.

The part is now square to within the accuracy of your machine.

[BobWarfield]

Originally Posted by Blink- The angle plate sounds intriging, and less labour intense. However, the plate I am trying to cut is plastic (Acetal), and I am worried about it flexing, causing chatter. Hence the reason I don't want to clamp it upright in a vise, and have 3" above the jaws. I'll have to check what sizes of angle plate are availible, maybe a 4". Y asix tavel is no problem, it is a full size Bridgeport mill. Edit: Shell miller?

The venerable Widgitmaster has a picture in these forums of a plate milling job in the vise where he is using 2-4-6 blocks to provide support and eliminate the chatter you describe. Look at his pix in this thread:

http://www.cnczone.com/forums/showthread.php?t=24554

Sure looked quick and easy, but you gotta have the blocks!

Best,

BW

[Blink-]

Another great idea, and I like this one even more :P. I'll have to check tomorrow to see if any 2-4-6 blocks are availible.

That thread was VERY nice, lots of good machining operations (squaring, slitting, rounding). Thanks!

[One of Many]

As you can see, there are several ways to get this done.

Here as some of my common approaches, depending how large the plate is verses the machine travels.

If your vise is deep enough. Stand it up and cut the first edge. Flip it 180 and cut the second edge parallel to the first. If you indicated the rear vice jaw in, to the X- axis, you can now lay the part flat on parallels in the vise to cut the ends square.

If you can trust your T slots are parallel to the X axis. Use pins or make up some snug fitting keys in the slot and use that as your reference. Clamp the part down over a piece of scrap(to keep from cutting into the table). If you position the clamps to keep 2 adjacent edges clear. Like one clamp in back and one to the left end. All you would need to do is cut those 2 clear edges(one in x and one in y) and rotate the part 180 and do the other 2 edges.

DC

[Blink-]

One of Many,

The first way you described it is the way I think I am going to try, but using 2-4-6 blocks as described above because I've got the travel, and the fixed jaw had been dialed in on the vise.

[One of Many]

Yep, that'll work well too.

I don't have those fancy blocks, but I have made up some extra tall aluminum vice jaws that fit my Kurt vises for similar purposes.

DC

[ZipSnipe]

Once again the Widgetmaster is the man , great idea with the 123 blocks. One of many, you should invest $14 in a pair of them they are very handy, in fact I,m buying a second set.