Ok,, simple question, but I don't understand what's happening...

I just got my Ace Mitchell Tru-Pitch. I took out the finger grips to improve accuracy, and started measuring. There's no instruction guide, but it's seem so simple that I shouldn't need one....

On any pitch I try to measure, I'm always getting different readings depending on which way I lay the scale. In other words, let's say I have the finger holes at exact top dead center and measure with the scale going down to the thumb, and let's say the finger pitch reads 1/4 reverse. Now, if I take the exact 180 degree difference, I should still read 1/4, although the direction may be opposite. Problem is, I'll read 1/4 one way and zero the other.
It's worse for lateral pitch. If I orient the scale left of the finger, I'll get 3/8 left pitch (left handed). If I orient to the right, I get 1/16. The same problem will exist for thumb measurements.

I can understand and correct for forward or reverse on fingers and orient to the thumb, but what about laterals? And why differing amounts, forgetting the direction. I should get the same angle each way....

Any ideas?

Make sure your using the biggest insert that will fit into the hole.  It should be very snug.  If you use a size that goes into the hole easy there will be play in it.

Yes, I see what you mean. I can fairly well stabilize the readings by using the absolute tightest insert. I realize its a cheap tool, but I can still obtain the results I want, such as differences between balls, and a few readings that are now consistently showing a 1/4 - 3/8 difference from spec in lateral pitch. The Jonell gauge I've used at the pro shop is clearly superior, but they are also 10 times more expensive. So, for the purpose needed, I think I can now call this a success.

The span measurement doesn't match up to the standard metal span gauge that I have used in the pro shops, but that's not what I bought it for....

Thanks for the tip.