Z clearance

[ccwerks]

I have a PRT Alpha 120 x 60.
I want to lower the table to get more clearance under the y gantry.
Are their any already tried and true ways of achieving this?
My thought is to put spacers in between the X rails and the angle iron cross supports to drop the surface of the table.
Thanks
Mark

[bleeth]

It's been done by some for various reasons, but you need to remember that your z only goes down so far. SB does make extended side plates and folks who need to use long bits (like foam cutters) have used them.
However you do it, remember that the further away from the material that your router is the weaker your cutting force is.

Reports are out there from people who have and they actually end up with a "secondary" table put on top of their lower one for cutting harder material with normal bits.

Lowering the table under the rails is probably the easiest way to do it with the standard plates. You didn't say how much you want to gain, but assuming it is more than a fraction of an inch I would use heavy material like an additional heavy c channel or even a box beam with side plate and be darn sure I bolted it (or welded) very well.

[ccwerks]

Dave thanks. I have the Colombo 5 hp spindle. same deal?

[bleeth]

With that you'll get a lot less runout at the end of a long bit but in general the same thing applies.

The other thing that comes into play is which Alpha. The earlier ones had 1:1 motors and much more chatter than the later geared ones. It resulted in some not so nice edge quality. This would be worse the further from the end of the bit the spindle is.

Post your Alpha serial number if you don't know already which you have. There were also changes made to the PRT gantry by SB. They changed the z car from all bolt together to more of a unibody plate and that helped keep thing square. I think that was done around the time of the earing change. Lots of different approaches were taken by users to stiffen the whole thing up and make it run smoother after-market.

Mine started out as a PRT with Columbo very shortly before the first Alphas came out. It's now a modified PRS Alpha with the orginal built by me heavy steel table, custom PRS rails and gantry, and Alpha motors and new controller. I've been tinkering and upgrading it in stages since I bought it. Call it my "more fun than chasing golf balls" hobby.