Wrong depth

[kubotaman]

How does one go about knowing how to correct my Alpha from cutting too deep? It seems that it is approximately 1/32" too deep. Also when cutting a circle it is too small. What or how do I correct my problem?

[woodworx]

your unit values might be off. correct them if necessary.

[erik_f]

I once was using a down spiral bit that measured out at .23" and seemed to push the router up slightly because of its down spiral nature. I changed to straight flute that measured out at .25". My depth problem was solved and my dado's fit perfectly after that.

[dlcw]

I measure every bits' cutting diameter with digital calipers (.0005 accuracy) to get the actual cutting diameter, not the advertised cutting diameter. I then make sure that my tool databases have this actual cutting diameter and I've not had any problems with fitting joints.

When I first started using my PRS Alpha, I used the bit manufacturers numbers as the cutting diameters. I couldn't get joints to fit properly and my pocket cuts were not what I had specified.

The difference between an advertised .25" end-mill and an actual cutting diameter of .238" will make the difference in nice fitting joints and pockets being the correct size. It just takes a second to get the actual cutting diameter. I also check cutting diameters again after I get bits back from the sharpener. This burned me a couple of times.

All this applies to using bits in a hand-held router and a router table as well.

Don
www.diamondlakewoodworks.com (http://www.diamondlakewoodworks.com)

[shoeshine]

It would also help to mic your Zzero plate. I found that my plate was actually .119 though it was nominally 1/4in aluminum. I then corrected the settings in the Zzero routine and got much better depth control.

[rb99]

Are the Shopbot machines not all built the same? How then could the unit values be different?

I would take my Z plate to a machine shop and have it surfaced so it is super flat and accurate.

RIB

[thewoodcrafter]

Richard,

All ShopBots are not made the same.
You have PRT and PRS, with and without geared steppers.
The unit values will be different.

I think machining your z-zero plate is a little over kill.
Just mic it.
It is already flat enough.

[dlcw]

I agree with Roger, the z-zero plate is already flat enough. The secret is to z-zero at the same spot on the plate every time.

I simply mic'd the z-zero plate in one spot, about a half inch square (outlined in red) and always zero to that spot. The measurement is entered into my_variables.sbp file and things are good to go. This way I know there is repeatable consistency in the z-zero process.