Newbie- Handy Table Fixtures ???

[Bob La Londe]

I finally got my mini cnc mill setup and calibrated. I can tell I am going to need some various clamping fixtures. The biggest problem I have right now is clamping material in place on the table. Mostly I have been experimenting with the machine by engraving some .125 aluminum I have left over from another project, but holding them in place, and making them square is a pain.


It came with a couple screws with threaded plates that slide into the table. There are four grooves in the table and I got four of these screws and plates. I drilled three pieces of aluminum angle to use as clamps by putting the screws through the angle, screwing on the plastes, and then sliding the assembly into the table. Still its a pain to get things square and clamp them in place. I think for some repeated projects I may find that it will be a benefit to make some jigs to hold the entire work piece.

So, I am curious, what kind of clamps and fixtures do you guys use for holding material on the table? How about jigs that you can leave in place so you can repeat your work consistently?

There really isn't any place to use the classics like c-clamps or welding clamps like I use on my drill press.

[Bob La Londe]

I think my next project is going to be mill a bunch of t-bolt blocks to exactly fit the grooves in my table, and drill and tap them with helicoils for strength. Actually I think I'll just make some long pieces, then slice them smaller as needed.

Then I think I'll weld up a rectangular clamping jig out of aluminum angle to exactly fit the working dimensions of my mill. Maybe put a stop on the Y axis so it will always square against the back of the table. Then maybe add some tabs on the opposite side of the Y axis so I can clamp a piece of material up to it where it hangs off the table.

I can't believe nobody has any standard mill clamping fixtures they are proud of. So many ideas so little time.

[TOTALLYRC]

Hi Bob, alot of people use a fixture/tooling plate with holes drilled on a regular pattern.
say 2"x2" spacing on a full sized mill or what works best for you.
Otherise the clamping kits work well for the one of jobs.
If I am doing a lot of the same part, say 100+ I will make a dedicated fixture.

Mike

[Bob La Londe]

Yesterday I finished ... sorta... my first fixture. I took a piece of 3/8 aluminum plate cut into a 5/8 strip and milled 1/16 off each side. Then I milled 1/8 x 1/8 off each top corner. I followed that up with a run to punch 11/64 holes along it on 1/2 inch centers. The next thing to do is tap and Helicoil all the holes to 8-32 so I can use an assortment of various length screws for clamping. Somehow every thing came out rough but ok except my holes down the center. They are visibly off center. I must have done the math wrong at some point. I don't know why I didn't see it while it was on the mill. I think I'll go ahead and finish it though just to see what other headaches I'll run into. I have another strip cut to do the same way, but I need to come up with a better way to clamp and zero the work piece. I think it will be easier to keep the math right if I make a couple test cuts and zero the work piece to its londitudinal center rather than zero it to its first milled edge like I did the last piece. I'll basically have a t-bar nut 8 inches long that I can slide into the table grooves.

One of the biggest things I am having a problem with is lack of experience...

I am learning the hard way what the best RPM is for various size cutters, and what the best feed rates are, and how much to vary feed rate or rpm depending on how much material I am removing.

On the flip side of all this... its repeatability for drilling holes exactly on 1/2 centers was awesome. I may never use my wobbley old drill press again. Atleast not for anything I can fit a bit in my mill anyway.

One of the other headaches I had was trying to use the mill like a regular mill for this project. For drilling it was ok, but for those long runs its kind of a pain to sit there with one hand holding down the button on the keyboard, and the other working the spray can of lubricant. My first couple projects were engraving, and I could just start the program and watch the machine, but for just plain milling one off fixtures like this it was kind of awkward.