Need Help!- Getting end mill back in already milled hole?

[Micro Milling]

I have to make cuts that are exactly the size of the end mill. One of the cuts has me needing to remove the clamped down object.

I need to make a straigt cut from that last cut. The problem is I have difficulty getting the end mill exactly back in the hole. Since the end mill is grooved at the tip, it is hard to get it back in perfectly and when I cut from there I will be a little bit off.


Is there a way to center the end mill back in the hole perfectly?

[HuFlungDung]

No, it is next to impossible not to create a dwell mark when you interrupt the tool in the cut. This is due to flex of the endmill, it tends to bend slightly (or a lot) while cutting and then straightens up when it the feed stops, even if you retract it very quickly.

The best way is to take a rough cut down the centerline with a smaller diameter tool, then take a cleanup pass down each side. The lighter cleanup cut will cause less cutter deflection than went on while you were hogging the groove out full width.

Another thing: the locating surface of the part must be absolutely flat, perhaps absolutely square to the machined surface and the fixture holding it must be absolutely square (vertically) or this will cause a slight change in position when you flip the part.

To some extent, you can use an edgefinder or an indicator to detect the exact location of the previously machined surface, and use that for the location datum when making the secondary cut.

It will still be a challenge to make two cuts in two setups merge perfectly. It might be that if you post a picture of what you are making, that someone will suggest a method of setup and machining that will permit the part to be machined more accurately and with good matchup.

[Micro Milling]

Here is a picture of the cut I will have to make. Going from right to left. First arrow, I start with a rotary table, locked at 0 degrees, and go straight left until I need to start rotating the rotary table to make the circular cut and stop about 135 degrees, then I go straight down with the end mill at that angle and stop where I have to go straight left again. Just follow the arrows.

Now the problem is, I can't simply rotate the rotary table back to 0 degrees to make that final left straight cut because the metal is not in the center of the rotary table and the metal is now at an angle. I have no choice but to reposition the metal to make that final straight left cut.

How would you do this cut all in one single cut with using a rotary table?

[HuFlungDung]

I'm no toolmaker, so I'm not up on the tricks that one of them might use to do that. I'd just program it on the cnc and be done with it.

[easymike29]

Without re-clamping the material, return the rotab to the 0 setting. You can then do the math required to calculate the new x/y location from the termination of the last position.

Gene