I'm considering an upgrade of my 1981 Model 500 to a 510/520, but now I'm wondering if I'm better off getting a used 510/520. My 500 is in good shape, so what don't I get if I go upgrade? Here's what I know from the SS site:
Two bearing quill introduced in 1984. I can buy this as a separate upgrade. Is there anything else different about the Poly-V drive that was introduced in 1984?
"C" Headstock and red safety switch introduced in 1991. Safety switch is also available as a separate upgrade. What else is different about the "C" headstock?
Is there anything else I'm missing?
Are the motors the same? Mine is 1 1/8 HP, and the SS website says "develops over 2 HP." Does that mean it still uses the same motor? I always felt it could use a bit more oomph.
You can of course do as you please but there is no reason to purchase a newer model as an upgrade is a very viable path. The quill is in my opinion worth the upgrade, the power switch is an none issue (the one in my 1976 model has never needed any attention) and the motor is the same as you already have. The "C" if I remember right also has a larger hole and a matching change to the logo cover thing.
If you have taken care of your unit then at worst it might need some new belts or bearings.... when you get a used one who knows how well it was or wasn't taken care of... or in other words what you pay for it may not be what it is going to cost you.
(BTW I upgraded my '76 to the 520 and then when I got a used 510 I upgraded that to a 520 so I have two.... this is another option for you, keep the one you have and buy another.)
