How would you setup this part?

[Vavet]

How would you set up and clamp this part on your mill?
I have a 12x14" 1/4" thick steel plate. I need to make three 7/8" diameter holes in it with the centers of the holes representing the three points of an equilateral triangle with each leg equal to 11.5 inches. The altitude of the triangle is 10 inches.

How would you support the piece off of the table so the drill bit/boring bar does not contact your table? Or do you try to align the intended hole locations with the T-slots in your table? I don't think they're 7/8" wide, but if the holes were smaller, would you entertain that as an option?

Do you set it on parallels laid flat on the table?

The workpiece is too big to be held by the vise.

 

[Tony Wells]

I would use toe clamps and 1-2-3 blocks, most likely. And feathers in a table slot for alignment.

 

[pineyfolks]

Space it off the table with whatever you have handy. I use 1" key stock or square tubing because that what I have the most of. You have to have it high enough your drill tip can get through. Clamp as close to the holes as possible. I usually throw a piece of scrap plate under the hole so if you break through you can't hit the table.

 

[jaded13640]

I like both plans.

I was thinking something along the lines of multiple pieces of stock all clamped down and the workpiece clamped to the stock. I don't know how accurate you're holes have to be in perpedictularity to the surface but if it is at all critical that'll determine what you use for stock. You know, like using parallels or something with very accurate tolerances.

Interesting project.

Be sure to show pics of the finished piece.

Wayne

 

[Frank Ford]

Space it off the table with whatever you have handy. I use 1" key stock or square tubing because that what I have the most of. You have to have it high enough your drill tip can get through. Clamp as close to the holes as possible.

Same here, but I'd probably reach for a scrap of 3/4" plywood.

 

[Vavet]

I would use toe clamps and 1-2-3 blocks, most likely. And feathers in a table slot for alignment.

Im not really sure what you mean by feathers. Can you expand on this idea?

the fact is I already made one of these and I used parallels, but it requires a tight tolerance on the depth stop. I have to make another plate with 3 smaller, but concentric holes for vertical rods to go though and I figured there had to be an easier way. I have some 1" square stock handy and I think that will be sufficient in perpendicularity for my purposes.

Thanks for your help, ideas, and comments.

 

[kd4gij]

By feathers he is saying stick somthing in the T slots that stick up high enough to but the plate aginest for alinement.

 

[xalky]

If the holes can be ever so slightly off square to the plate, wood is my spacer of choice. Mainly because I have tons of it laying around. MDF is remarkably stable dimensionally, as long as it doesn't get wet. If they have to be absolutely perfect then space it up with some parrallels.

 

[markknx]

Next time you have to make two parts with the same hole layout you could do yourself a favor and stack drill them. line the edges up real nice and clamp them together then drill them. Or at least drill the one with the smaller holes first so you can use a transfer punch or spot the hole through the first plate. As far as how to mount it I like the ideas already given using 123s or scrap depending on how square the holes need to be you can even use wood block. I do this on the drill press for thigs Like clear holes for bolts in thinner parts like 1/4" Just some thoughts.

Im not really sure what you mean by feathers. Can you expand on this idea?the fact is I already made one of these and I used parallels, but it requires a tight tolerance on the depth stop. I have to make another plate with 3 smaller, but concentric holes for vertical rods to go though and I figured there had to be an easier way. I have some 1" square stock handy and I think that will be sufficient in perpendicularity for my purposes. Thanks for your help, ideas, and comments.

 

[Metalbender]

My vote goes to the MDF, you're likely not working on a spaceship, otherwise you'd have all the fancy tools at your disposal. The joy of a home shop is you get to improvise. A hole that big in relatively thin stock will always have some wiggle room for alignment.