Newbie- Clamping with a rod

[thatstephen]

So I am running a cnc mill and I have had some problems with the parts rotating while I am doing any radial drilling. I clamp the part to the chuck and then when I go to drill 1/2 inch NPT ports the part tends to rotate. I guess my question is if I am clamping it on the ID of the part is it best to have a wider clamp on the front even if the entire face doesn't touch the jaws of the part, or does that not really matter?

[One of Many]

If the part is moving, everything contributing matters. Chances are you have not matched the work holding rigidity with the cutting forces to stabilize it. There honestly is not enough information in your post to dicern any more than that.

If you cannot grip the OD, I'd be speculating in suggesting a spud type expanding or clamping mandrel to mount the part on, not knowing more about the physical part itself.


DC

[thatstephen]

i am using a ready rod through the part with a piece of metal sandwiching the part against the chuck (which is at a 90 degree angle). is my problem not using a big enough piece of metal to sandwich it against the chuck.

[One of Many]

You still have not given any dimension references to the part, the allthread rod or the piece of metal you are using to clamp it. When you suspect something could improve it, make the changes and see if it takes care of it until there is improvement. The method will be somewhat different for long and narrow verses short and wide, thin or thick wall etc. Maximizing the available surface with distrubted friction will make the most difference.

Other than that. If this is your only option to hold the part, then you will need to reduce the cutting forces to meet the weak setup, by center drilling, and/or pre-drilling it with a smaller drill, or interpolating the hole with an endmill. Thereby taking less of a bite at a time that does not move the part. Slower might make a successful part, but efficient productivity would dictate going with a more solid setup rather than increasing the cycle time.

DC