Part support while milling

[Peacons]

What does one use to shim under a flat part when edge milling on a rotary rable?
Don't want to gouge the table inadvertently.

 

[benmychree]

A piece of aluminum would serve nicely, or most anything that would raise the part above the table surface.

 

[Karl_T]

Another option is called standoffs. I made up several many moons ago.

Take square stock, about 1"x1". drill 1/2" holes then a pocket for a Allen head bolt with spacing to fit your table. bolt them down with Tee nuts in the slot, take a pass with a large endmill across the tops. Now they are all perfectly flat to the mill.

Now you can place these under any part and clamp to the table as normal.

The advantage of this approach is open air under the part. better for drilling and boring ops. Also more rigid than just putting a scrap piece under the part - that likes to rock'n'roll under cutting pressure.

 

[Flyinfool]

It depends on the requirements of the part I am working on. If absolute accuracy is not required I often use a scrap piece of soft wood under the part. If greater accuracy is required I will use metal under the part. I have been known to put down the metal backer without the part and mill the relief into it so that I can then put the part down and have the end of the mill drill etc cutting air. Some times it is an odd shaped part where I have to mill a pocket to create a holding fixture. Or anything in between, It depends on the part. As with most work holding, there is no one right answer.

 

[RJSakowski]

My preference for backing is aluminum as wood or plastic will compress slightly with clamping. However machining flat stock is often two dimensional and some height variation can be tolerated. In that case, plywood, MDO, or tempered hardboard are a low cost backing material.

 

[Mitch Alsup]

What does one use to shim under a flat part when edge milling on a rotary rable?

If the part is big enough, just use the flat faces of parallels. (1/8" thick standoff).

 

[Peacons]

Thanks for all the great suggestions. Definitely have to try a few out.

 

[Illinoyance]

I keep some 1/8" and 1/4" aluminum flats cut into short pieces. I use these as sacrificial shims when using the RT.

 

[BGHansen]

Not adding thing that hasn't been mentioned above. I use particle board for a spacer when I'm manually advancing the Z axis. My Bridgeport has a 2-axis CNC controller, so easy to account for any rising of the particle board if it's becoming saturated with coolant. My Tormach is 3-axis CNC so have consider swelling over time, so generally use aluminum there unless I'm cutting without coolant. Made the finger joints for some bee boxes on the Tormach and used particle board since the coolant was turned off. I wouldn't hesitate using particle board with coolant, but would do some spot checks for height and compensate for swelling.

Bruce