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richz

richz

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Jan 19, 2012
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I am building a simple tilting table. I have machined a round with a notch in it and need to attach a flat plate. I am going to use some allen bolts recessed into the flat plate and tapped into the round. I have the plate on the round and clamped to the mill table. Now the question. Do I do one hole at a time, tap drill, clearance drill then countersink? My thinking is to tap drill all four holes use the DRO to go back clearance drill all four then go back with the DRO and countersink them. I think if I do it this way I can hold all the depths consistently without having to change out the tooling for each individual hole.
 
My Tech Instructor just smiled and nodded when I asked this question.
I'm working off handwheels (by choice). It's easier for me to mess with Z than to relocate XY.
I've had good luck with my Wahlstrom. But, adjusting the knee gets tiresome.
You are working with DRO sounds like your plan is solid, as Z becomes the largest window for error.

Daryl
MN
 
What you describe is the way I normally do it. I think you are right on. :encourage:
 
I do it the same way as described. Otherwise you will find your self changing depths too many times. This can give errors in depth by simply thinking you already changed it for the hole you are about to do.
 
I'd do it your way for the reasons you state.
 
Using the DRO and tap, clearance drilling and counter boring went pretty good. I did have a problem with counter boring for the 1/4" allen head screws. I am using a PM 932M and was counter boring at 345RPM. It seemed like I had to apply a lot of pressure on the 3/8" end mill to start cutting. I tried 670RPM and the cutter was making noise and did not want to cut. I know that there are specific counterbore tooling. First hole was #7 the I clearance drilled at .250 I thought that the would work better than what it did. also when doing the drilling and counterborin

1.JPG
 
I like doing one hole at a time, especially when tapping. More chucking, but every hole is done w/o relocating. Just be sure to spot/set Z axis DRO before counter boring with a REAL, flat bottom counter bore tool (1/4" allens I go .255" deep).
 
Odd that you had trouble with the end mill cutting. I've caught myself going the wrong direction on the bp between shifting from high to low, tapping to drilling....but even a non-centercutting end mill should work fine as a c'bore. You do know they aren't truly square ended, right? Not a big problem usually.
 
I did not know they weren't truly square. I have milled a lot of keyways at work put a key in and never noticed.
 
Well for that, the resulting cut profile is square, because they act the same as a flycutter. But they have a little relief on the face edges of the flutes. Put a good square on one sometime and you can see it.
 
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