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Work holding problem

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Wolfie24/07/2013 14:54:36
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502 forum posts

Hi all I'm back in the workshop at last and I have a problem already.

I want to clean up the ends of a slab of aluminium, doing one end and then milling the other to a particular length.

However its a bit too big to clamp down. Its 12" long so can't put in the vice and its too wide to clamp on the mill bed, it covers all the t slots.

I can clamp one end but not the other. Grrrr

Ideas??

David Littlewood24/07/2013 15:01:59
533 forum posts

Wolfie,

Why is it too long to fit in the vice? If it is a chunky slab it should be rigid enough with say 4" overhang at each end. If not, hold it so one end is close the vice, clean up, move it so the other end is close to the vice, clock the clean end with a centre finder, wind along (ensuring you correct for backlash) and Robert, as they say, is your mother's brother.

If for some reason this won't work, you may be able to clamp it to the bed using toolmakers' clamps, but this may restrict table movement.

Alternatively, if it is to have any holes in it, make the holes first, use them to hold it to the table, and clean up ends to match hole location.

David

Russell Eberhardt24/07/2013 16:07:18
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2728 forum posts
86 photos

I don't know what lathe you have but you may be able to clamp it to the cross-slide and use a flycutter in the chuck.

Russell.

Andrew Johnston24/07/2013 16:46:52
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6574 forum posts
701 photos

Turn it through 90°, so it hangs off the front of the mill, setting perpendicular with a square on the edge of the table. Mill one end, and then turn it round.

Andrew

Wolfie24/07/2013 22:13:31
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502 forum posts

By in the vice I meant upright, in other words the vice has only the bottom end. I tried it the other way on and no matter which slot I mount the vice in the milling cutter doesn't quite traverse the whole end grrr.

Tried mounting it lengthways but as I have to raise it off the bed getting it square is the problem there.

Les Jones 124/07/2013 22:53:15
2255 forum posts
156 photos

Hi Wolfie,
If you use Andrew's suggestion you can get it square using a dial gauge against one edge of the bar. Clamp the bar down to the table with a suitable spacer to raise it above the table. ( Use parallels or as I do sometimes a scrap piece of melamone coated chipboard which I find ir reasonabley uniform thickness.) At first clamp the bar down from one side only using two clamps using a set square to get it about right. Set the dial gauge against the edge of the bar without clamps. Traverse the table in the "Y" direction (Front to back) and watch the dial gauge. Slacken the clamps slightly and tap the bar in the direction to correct any error. Re tighten the clamps and traverse in the "Y" direction again. repeat this until the dial gauge does not move significantly. Now put a clamp on the unclamped side of the bar. A variation on this would be to set an angle plate at right angles to the table using the above method.The bar can now be clamped between this angle plate and another one on the other side of the bar using two lengths of studding between the angle plates. The second angle plate not fully clamped to the table until the studding is tightened. If you have several ends to machine the angle plate method would save time.

Les.

JasonB25/07/2013 07:09:01
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Wolfie can you give us the other two dimensions of teh block so we have a better idea of what needs machining.

As les and Andrew say hanging it off the front of the mill is probably the best way as you have the longer X axis travel and just clock it in with a dial gauge. Or if you can't hold the squate against it when packed up put the stock of the square against the flat column but clocking it is more accurate.

If you have enough movement on the cross slide of your lathe then pack it up off that and again clock it true before flycutting the end. I had to resort to this the other day on a large engine base casting

Hopper25/07/2013 08:36:43
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6192 forum posts
321 photos

Couple of angle plates bolted to the t-slots and the block of aluminium clamped/bolted to the angle plates?

colin hawes25/07/2013 11:22:10
557 forum posts
18 photos

Sometimes on a job like this it is possible to drill and counterbore a couple of tooling holes in a place that won't show on the finished job or where they will subsequently be machined away. Then you can clamp into tee nuts. Colin

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