Shure Stylus Gauge

As some of you may know I have had some questons about the use of the Shure SFG-2 Gauge. Well at the risk of being extremely annoying here is one more:

I have noticed that when I place the Gauge on a record instead of the platter mat, the VTF reading on the gauge is much more higher. (ie. on the mat the reading is 1.5 grams, on the record the reading is 2.5 grams, then if I place it on the platter without the mat the reading is much lower roughly around 1 gram). The Shure instructions read "for better stability, place the gauge on a record" when I do this it seems to balance okay, then if I push the lever down (stylus still on lever groove) the tonearm and lever stay down and won't balance back up. It just lies against the record. Weird since it balanced before I pushed the lever. Could there be something wrong with my RB300 arm, I just had it rewired and VTF spring removed, or the guage itself?

My theory would be that there is something causing mechanical resistance at the arm bearing as the headshell goes lower. This would explain both the different readings with and without an LP, and also the fact that the arm stays down when pushed down.

There could be a few reasons for this:

First, is your arm mounted at the right height at the pivot? The bearing will only allow the arm to swing free within a certain range.

Second, does your arm have two separate balancing mechanisms, ie, a gross mechanism to get the arm to balance (0 weight) and a second calibrated one to set the actual weight? If so, you should always calibrate the the arm to zero before using your scale. If not, the arm may not be within a range in which the counterweight and stylus force are linear with respect to eachother.

Third, is the tonearm lift interfering?

Fourth, there is some friction at the pivot of the scale (good news) or some friction at the tonearm bearing (bad news).

Hope this helps.
How can I tell if it is the arm bearing. Is there a test I can do? When I set the counter weight to float the arm, it seems to float, and bob up and down, side to side without hesitation at all.
the bearings might do ok but the pivoting position plays the vast role in this situation. the cartridge weight oght to be the same whether you place mat record or none of these. certainly the readings on the soft mat might not be pricese anywhay.
After talking to a few dealers, I'm almost sure that you are suppose to get different readings if you raise the surface height of the platter (i.e. record V.S mat). If you think about it, it only makes sense. As you raise the the gauge the arm rises too creating incorrect VTA which would cause incorrect VTF. Does this make sense to anybody or am I just totally in the wrong.
i've just re-measured on my turntable(where i don't use any mat) and the reading are barely different that the difference cannot be captured by the Shure gauge meaning less than one tenth fraction of the gramm.
I've never tested the diffences; I measure on a record and Let It Be. I have used a touch of lube on the pivot pins of the Shure to eliminate bearing stiction.
There is something definitely not right here. The first is that you should not get a different reading when you apply pressure to the gauge and it does not return to the same spot. If it bottoms out and does not return, you have no way of knowing what vtf you have.
It is not true that the vtf will change due to the height or vta. For any arm that uses only counterweight to control balance and vtf, the reading should and will be exactly the same regardless of the position of the arm. Technically, if there was still a spring in yours, the spring could have a different tension depending on the height the arm was sitting, but I have never got a different reading on an rb-300 that I could detect. To be sure, you should not get a different reading depending on height.
I'm struggling to clarify rather than confuse- but here is this. If you are going to measure vtf on any arm, you should apply some sort of of light tap on the gauge and get a reading that way to be sure that other forces, such as friction or damping or resistance, are not giving you a false reading. A cheaper arm with cheaper bearings, or sticky damping fluid, or bound wire, or any external force could cause a reading different than what the vtf is when things finally come to rest.
None of this should apply to you since the rega arm has excellent bearings, no damping, and cardas wire is thin and flexable enough that there should be no influence that you should be able to detect. That particular combination should balance perfectly every time.
I can only guess at what is going on, but I am sure something is not right, and hopefully it is your procedure in getting your vtf. I would first put the stylas gaurd on and balance the arm to acheive 0 vtf, and it should float and dance around with no resistance. Do this to accustom yourself with the behaivior of the arm and check for anything which would cause the arm to not move freely, such as the wire causing tension, the cueing lever, etc. There sould be no obstructions or resistance. Then, after you have done everything you can to see that it is free, and you haven't ruined your stylas because you had the gaurd on, do your vtf- when you get it to balance, push down EVER so slighty, only about 1 or 2 millameters, and adjust so it balances.
Get back after you have done this or attempted to. Don't forget the stylas gaurd while you are checking it out.
I totally agree with MRCS's idea of mat vs. record underneath the gauge affecting the reading. I have noticed a difference in VTF when I changed the VTA even slightly using a Graham, SME IV.Vi, or a Rega tonearm. I usually place the stylus in the notch on the gauge, and then blow on the gauge lightly (once the weight is fairly balanced and in range) to reset the gauge. This allows the gauge to really zero in on the correct weight (by moving fully up, then back down to a true resting point) I've compared the Shure to a $600-$700 Winds gauge, and the Shure is pretty darn close (within 1/10th gram or so). Do your final dial in by ear though once you are in range.

Thanks to all for your help in this frustrating matter. It turned out to be a faulty gauge. I just got a replacement everything is set-up perfectly. Just gonna sit back, forget and enjoy.
Thanks to all for your help in this frustrating matter. It turned out to be a faulty gauge. I just got a replacement everything is set-up perfectly. Just gonna sit back, forget and enjoy.