Folks, I need a little guidance on creating index pin holes in my CNC Router MDF table surface.
I intend to place numerous 3/8" diameter holes in the surface for indexing and insert steel 3/8" pull-pins for location.
Is the best method to drill the holes using a standard drill or to use a smaller router bit (1/4" 2-flute end mill) to machine the holes using a helix cut to depth? Can I get the accuracy for no slop using a 3/8" Drill?
I'd strongly suggest using the machine itself to cut the holes, so the easiest way would be to draw a grid of circles with a CAD package, and then use your CAM package to pocket cut each one (with the 1/4" bit).
Even better would be to use a 3/8" bit, and place a point at the center of each hole, again using your CAD package, then create a drilling process in your CAM tool.
I use a free CAD package called ProgeCAD, and a cheap (but very good) CAM package called SheetCAM. Either of the above is easy with these two (and probably many other packages, to be honest).
I wouldn't recommend using a drill bit - especially if you are thinking of using it in your spindle. Drill bits aren't designed for use at spindle RPM speeds.
Spot drill, drill undersize, and ream your holes to size for a perfect fit. Solid carbide drills will certainly help, but their is no guarantee without reaming that you will have your perfect "no slop" fit.
Appreciate the feedback. Two different approaches and obviously both viable. I would prefer to machine using pocket methods because this will be quicker but drilling and reaming also meets the need!!
Hmmm - quandry! I think I will try a test hole with the pocketing method to see how close I can get it. The pins are ground, hardened steel draw pins (taped down the center for easy removal). If that doesn't work - i will drill and ream them.
I have a 200V 4HP spindle on a Yaskawa VFD - programmable (via software) and adjustable down to 1000 RPM. With a good quality drill bit, this would work. Not sure however about the reamer. I was under the impression that reamers need to go real slow.
... Not sure however about the reamer. I was under the impression that reamers need to go real slow.
Thanks for the input
A reamer in MDF is not very useful. In addition you will probably need blind holes to avoid pushing your pins all the way through; it is not practical to ream a blind hole. Interpolate the holes with a 1/4" carbide if your machine has enough precision or pilot drill and then straight plunge with a 3/8" carbide. For the straight plunge you need to make sure the cutter is running very true otherwise your hole comes out oversize.