So, how do YOU fix the job to the mill bed?

[Robin Hewitt]

Hi Lee

I think it's an important subject so to encourage you lot I'm going to post pics of how I do it and show what went wrong. Lots of explanation for the noobs :naughty:

This part was secured with 2 bolts on 3/4" steel standoffs. I used 3/4" because I couldn't find 8mm capheads between 40 and 65mm. A good selection of bolts helps minimise overhangs.

The wonderful things about bolts is you can set the tool to lift above them for the G0's without ridiculous quill extension. In this case 10mm to clear 8mm. No need to watch the G0 paths to make sure they don't hit a clamp.

I didn't dare run it right down in to the standoffs because they would cause the tool to dig in as it cut the extra metal, so I set it shy of the top surface and got a .06mm lip left around the bottom.

If I'd bothered to machine the stand offs so they didn't overhang the botttom I could have set the final cut deeper than the material thickness and lost the lip.

I used Gsimple to produce the G code because it was easy. Gsimple insists on cutting outlines up hill, internals down hill. I didn't notice the tool tip had snapped. See the pic at the bottom and notice the difference in cut quality inside to out. With a missing tip this long tool was bending like a banana and went past final depth on the externals before the finishing pass. Have to make it again :sad:

It never rains but it pours, my camera got on the wrong setting and all the pics came out black, but I did take a brief video that shows the setup. Notice sheets of acrylic in front and rear tee slots to catch the splash.

Bright mild steel, 12mm, 2 flute cutter (1.5 flute really) cutting 2.5mm deep, 2mm/s feed at 335rpm. A tadge slow perhaps but don't you just hate it when the suds gets diverted by a fixture and everything goes red hot in a trice leaving you stuffed mid cut

Robin