I'm drilling some 6061-T651 aluminum 0.250" thick plate that is 4" x 6" using one 17/32" drill and one 5/16" drill. these are through holes. There are also some 1/4-20 locations too but those have already been done.

17/32 = 0.53125"
5/16 = 0.3125"

hole finish √125 or better.

can use flood or mist coolant.

have not decided how to fixture these parts.. I have a run large enough to justify a fixture. Might use destaco clamps, allen SHCS's, milling step clamps, drill bushings and dowel pins. Last time I did parts like these I did a new fixture using advise from Carrlane and Destaco. (I called their techs)

would like to do a CNC program from a DWG or DXF of these parts to run on my Monarch VMC45 with Fanuc 6M control.

Either holding it in a ER16/32 collet or TG100 collet or in my Jacobs 14N.

I need to know what spindle speed I can use for these two drills. I have up to at least 4,250rpm drilling down to about 275rpm.

Greg

17/32 drill it @ 1900 RPM and 14 IPM, the 5/16 drill it @ 3000 rpm and 18 IPM...also make sure not to peck just run it straight thru..make sure your drill has 118 deg. tip evacuates ships better ,you'll have a nice finish.

I was wondering if it would be ok to go for a 0.001 or 0.002 downfeed per rev.

I also thought it would be in the neighborhood of 10-20 IPM.

Greg

That thickness 6061, those size drills, flood coolant I would use 3500 - 4000 rpm, 15 - 20 ipm, 118 deg drill and would spot the holes first with a 120 degree spot drill. Probably would also take a few pieces of scrap and try it without spotting all the way up to 6000 rpm and 30 to 40 ipm just to see how they came out.

Ok. I'll try it a little slow first. I can reliably drill @ 4,250/4,275 and have before so I was hoping this would be it.

I have a good coolant mixture set up right now so it will be nice to see how they come out.

One of the drilled holes then becomes an part of an index for milling / routing the periphery.

Greg