MintLP arc protractor

Hello Wendell,
Yes, there would be a more accurate way to measure, but it would no doubt incure some costs. And I'm unsure if this degree of high accuracy is needed? I'm no Rega Arm expert, but I would think, unless you are using a Rega Cartridge, and buttoning up all three holes on the Cartridge might there then be a problem?

I would assume the very best way, would be a large Dial Caliper, such as the machinist used, when he fabricated a new plinth for me on my VPI HW-19. I'd hate asking him the price of that tool, I'm sure it was not cheap.

Machined Locating Pins were fabricated for both Bearing, and Arm Base. Then with Calipers, the required didtance was measured out. It is important, that any measuring tool be perfectly level when taking a measurement. Any sloping of the measuring tool from point A-B (Pivot-Spindle) will give an erroneous reading, most likely longer in length than the actual S-P distance measurement.

I would think a good accurate Steel Ruler would be better as a tool.

I wonder though, wouldn't this be true, with a slotted Headshell, if one finds the actual S-P spec of 222mm slightly off, say by +- .5mm-1.0mm, couldn't one then properly compensate by sliding the cartridge on Headshell, thus getting perfect alignment with the 222mm MintLP Arc Protractor? If I'm wrong about this, somebody please chime in! :-) mark

I'm trading emails with Yip at the present time. I can only be so confident in my measurements. Even if off by a mm I assume that adjustment in the headshell slots and whatever minor movement is available with the VPI armboard should be enough to dial it in. Does this sound reasonable?

Wendell

Take a thin piece of wood and measure 222mm, drive two small finishing nails through so the points are exposed. Measure from point to point to make sure the 222mm is correct. This will be as accurate as you can get by eye.

Finding the horizontal pivot point on my OL Silver (modded RB-250) was trivially easy...

1. Mount the arm to the table (no cartridge needed, keep the stylus guard in place if it's already mounted).

2. Stick a piece of scotch tape across the top of the bearing center.

3. Using a fine, felt tip pen, make a tiny dot on the tape where you *think* the pivot point is.

4. While viewing your dot from directly above, swing the arm back and forth through its arc several times.

5. Move the tape as necessary until the dot remains stationary while the arm is moving. Voila!

6. Measure from center of TT spindle to center of dot, using a fine lined metric ruler. Keep the ruler level or your measurement will be artificially lengthened. Move the arm until the dot's at 222mm and tell Yip. You'll be well within 0.5mm.

7. Don't forget to remove the tape! Save it for future use if you're especially cost-averse.

This takes 2 minutes and costs $2 (for the ruler). Well worth it IMO for getting a good arm position before dropping $110 on a protractor.

Doug

P.S. No, I will not make up the tape and dot for those unable to do it themselves, whether for free OR for a fee!

I recently got a Mint for a Rega RB-300 on a Thorens TD-850. 222 worked fine. Dougdeacon's suggestion for finding the pivot point sounds great. You may still need a caliper (a small one) to measure the spindle diameter.