Ideas about to setup a part for edge milling

[dansawyer]

The project is to make multple common parts on a mill. The parts are 2 1/4 inches long and 1 1/2 wide. They are 1/2 inch thick and have a 1/2 diameter hole in the center. The question is: What are the practical ways to set this part up for machining the edges?
The machining is on the long sides. The machineing on one long side, left side in picture, does not extend beyond the side to either end edge. However the machining on the other long side is an 'arc' that extends to both the edges. This leaves about 1/2 on each edge that is not machined, lower and upper edge in picture.
In my mind I have gotten a blamk that has the hole drilled. My first thought is to bolt the part to a mill T slot with an offset. However I do not beleive I can bolt it tight enouch to prevent the milling from causing the part to rotate.
The next thought is to make a jig that clamps to the edges that is not machined.
I have made a prototype using 2 setups. I came to the conclusion two setups should be avoded if at all possible. Any other thoughts would be appreciated.

 

[RJSakowski]

I would machine the hole first and use that for primary clamping with a bolt through to a tee nut. A single clamping point is not desirable so I would clamp the arc as well and machine the long side, then move the clamp to the long side and machine the arc. the bolt through the center hole will prevent the work from shifting while moving the secondary clamp.

 

[RJSakowski]

Another way to do it is to leave two tabs on the short ends for clamping purposes and to cut them to size as a final op.

 

[RJSakowski]

Yet another way is to leave additional thickness on the part with material for clamping out of harm's way so that the complete profile can be machined and to mill that off as a final op. What method is used depends upon allowed tolerances which depend upon intended use.

 

[RJSakowski]

The bolt through the hole and stickum to prevent shifting will also work. Double stick tape or painter's tape plus super glue have been used. Care must be used not to take too heavy a cut. I would use multiple depth cuts followed by a dull depth cleanup pass.

 

[dansawyer]

Thank you. I will try the clamping method. I am traveling for the next week so it will be a while before I get to try it. Dan

 

[mmcmdl]

CNC or manual mill ?

 

[dansawyer]

CNC. I don't have the hole in quite the right spot and the two tabs are not quite parallel. But the part is close.

 

[mmcmdl]

CNC. I don't have the hole in quite the right spot and the two tabs are not quite parallel. But the part is close.

I would use 5/8" or 3/4" thick plate and mill the entire part to size and finish hole . Flip it over and mill to thickness in soft jaws . Still 2 set-ups but easy ones .