X rail spacing (2001) 144x60

[wingnut]

Hello,
I am re-assembling a 2001 144x60 table and need to know the required spacing between the X rails. I have found info for smaller tables but not the 144x69. Any help would be greatly appreciated. Currently the spacing (out to out) is between 78 3/8 and 78 5/8. Thanks

[cnc_works]

Couldn't you just measure the distance between the bearings on your y car?

Donn

[scottcox]

Mike,

My 2006 model PRT Alpha 10' x 5' has the rails at exactly 78.25" apart.

[wingnut]

Donn,
I could, but I am starting from scratch and want to know that everything has been done according to plan. I do not want to make any assumptions. Also, I want to compare what it was to what it should be to determine what else is outta-whack and by how much. Thanks.

Mike

[wingnut]

Scott,
Thanks for the response. Is that out-to-out, in-to-in, or center-to-center.

Mike

[cnc_works]

OK, but let me understand. Isn't the distance between the bearings on the Y car a fixed distance? In that case, whatever anyone else ends up with as a distance would apply to their specific circumstances but not necessarily to your exact measurement. So, if you measure exactly from the left side of one bearing to the left side of the opposing bearing on the Y car, that cannot help but be the measurement you need for the X rails to be apart.

Am I not thinking clearly?

Donn

[scottcox]

Mike,

That is center to center, but Donn has a good point. You probably want to verify the distance between rollers and shoot for that.

[cnc_works]

Center to center is by definition same as left to left. And the reason I used it was because it is easier to measure precisely.

That being said, when I first set up my PRT I too used arbitrary measurements until the light bulb went off between my ears...had to be a bright one too because of the density of the fog.

Donn

[myxpykalix]

Unless i'm incorrect on the type of bearing, the precise measurepoint should be the center of the V bearing wheel from one side to the other?

What i did was take a cumalong and attached it to a cieling joist to hold most of the weight of the carriage.
I did a rough measurement of the distance between bearings and drilled holes 12" down from the end and loosly put a couple screws.

lowered the carriage down so it had play to move them a bit to adjust space by tapping with a rubber hammer.

When one end was right and it would roll freely on that end I would roll it down to the other end and repeat process.

However before doing that i marked a line down the rails of the table that was parallel to the edge of the surface top to make sure i was running the rails parallel and square to the table surface. (hope that makes sense?)

[frank134]

question. what if the x car was out of square?

[curtiss]

I made a bit of a long "t-square" feeler gauge to set the rails.

The bottom of the T had an adjustable threaded rod that would lightly touch the rails and it was easy to tell which way they need to move.

I would suppose with a 144 the trick is getting the first rail level and straight.

[frank134]

yes I use a transit to level mine. MY son idea, an it work great. For the spread of the rail I use a straight 2 x 4. strated at one end made a good pencil on the 2x4 and just keep checking down the rail. Did a cross meanasure of the rail end to end. that it.I have a 60 x 102 table.