BitZero 1/4” Probe issue

Yesterday I was trying to get my Pro setup as accurate as poss. I built a dial holder that I could mount to a bit. Then I thought that I’d use the 1/4” probe as the holder. I had a lot of trouble tramming. Then at the last minute I looked at the probe as I rotated it in the router. It was visibly not straight. An hour or two’s work wasted there. I should have checked it first but I just assumed the bitzero would not be accurate if the probe had run out. The run out was around 0.4mm. So a lesson there :grinning:. Even against a straight edge you could see light coming through the gap.

But then I’m thinking that the bitzero can’t possibly be giving me accurate Zero unless I’m misunderstanding how it works. I assume this isn’t a huge issue?

I have mentioned this in past pasts. For the last few months I have been using the bottom of material to zero the Z. This has worked very well. I use the superglue and tape method a lot and I just barely cut through the tape. This is a change of work flow and took some getting used to. I still use top of material on some things.

The only issue with zeroing on the bottom (Spoilboard) is the material thickness including the painters tape must be accurate or the first cut on the top of the material will be deeper than expected. This can effect pocket depths so measure while on the spoilboard with your calipers to include the two layers of painters tape if you use that method.

The z zero on the bottom of material has kept my spoilboard in good shape for 4 months.

If I understand correctly, you attached a dial indicator to a 1/4" probe mounted in the spindle then tried to indicate the probing hole in the BitZero to find X and Y. If this is the case, The 1/4" probe/shank/shaft, does not need to be straight. You are rotating about center. Meaning, you are rotating around the center line of your spindle. This will be as accurate as your spindle bearings. If the hole you are trying to indicate is not round, it makes it a bit more difficult to find center but you can.

If the spindle is static, (no rotation) and you are using the CM probing routine, then your probe/shank/shaft must be straight. In addition, your collet and spindle tapper must be clean, free of damage and seated properly.

For general machining, I would stick with the CM probing routine with a known good probe. If you want to check your probe for run out, properly mount it in your spindle, place a dial indicator near the end of the probe and slowly rotate your spindle by hand. Note the total amount of movement. If it is within your allowable limits, proceed with your probing routine.

Ah not really. I think I didn’t explain. I was using the probe 1/4” shaft purely as something to fix my dial guage on while I check tram error. That will only work if the shaft is straight. It isn’t.

But that brought me to conclusion 2 which has nothing to do with tramming; if the probe shaft isn’t straight then surely can’t probe correctly because the run out will effect when it contacts the probe hole walls in the probe body.

Maybe a picture for clarification?

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