Oh, yea, one other difference. With the old PM3520A the minimum speed was almost 0 rpm. With the B model that went up to 50 before the motor turns off. This is standard for most 3 phase converter lathes (exception Nova DVR which used to be 200, and now I think it is 100). This is important to me for sanding my warped bowls. You can't keep your hand, the sand paper, or drill on the wood at speeds above about 20 rpm. I called the PM people and asked why they changed it:
"You'll burn up your motor and fry the electronics."
"I have sanded out thousands of bowls at that speed and had no problems."
"Well, you can't do that. If you want that done, we can do it, but you void your warranty is void, and you have to ship it here to us to do that."
I had Brent English walk me through lowering the speed, and actually raising the high end speeds a bit. I keep checking the motor for heat build up, and it runs cooler than when I am turning bowls. I don't know if Oneway would do this or not.
robo hippy
For some of us, the ability to have a very slow rpm is important.......it is important to me for the same reasons it is important to robo hippy.
For me, my normal sanding speed is somewhere around 300rpm, plus or minus.....but, the rules change with how much warp has occurred.
When finish turning, many well seasoned roughed bowls, with a low moisture content, will still have some amount of warping. This is especially true for "thin wall" bowls, some species, shapes, roughed wall thickness, original moisture content, etc.......and some will not warp at all. This is just the way it is, and we learn to deal with the real world results, instead of theories. Depending on how much warp you get, it's sometimes necessary to sand at very slow speeds......less than 100rpm, and down to about 25rpm, or in that range.
If a random orbital sander is used, you CANNOT have the lathe running at any rpm you would normally use for sanding discs, or paper sheets......but, it does a great job......IF.......you can get down into that extremely slow 25rpm range. Without the 25rpm capability, any use of the random orbital sander will need to be done at 0rpm.
I am relatively new to using a variable speed lathe, having converted my Woodfast in 2007......I had been changing belt/pulley for a couple decades prior to that. Since changing over to VS, my motor seems to be in good shape regardless of the slow sanding I've been doing.......will it burn out? That's a question unanswered for now, but so far, so good! I tend to think some manufacturers may have over-reacted to motor burn-out, and have prevented very slow rpm because some turners may have used the very slow speed capability for very long extended times.......but, that's just a guess on my part.
The bowl in the foreground is Maple, and warped badly during seasoning. I trued up the exterior as usual, but sanded the interior without further shaping. The result is rather spectacular, in my opinion. This would have been impossible to do without having that extremely slow rpm capability.
ooc