Time for new rails?

[jeffreymcgrew]

Hey everyone. So we're now at three years (god it's hard to believe that!) of semi-regular use on our PRT96.

We've replaced the pinons, and now are wondering about replacing the X rails too. They are a little warn now.

We mounted our rails to aluminum extrusions when we redesigned our table. I'm thinking that with new rails, we could mount them like the PRS instead.

I'm looking at the BWC website, and I'm wondering what would be a good one to go with.

Should we go with a bigger rail? Is there an advantage there?

Should we go with dual rails (top and bottom)?

Should we get new wheels too? Don't see why, but then that's why I'm posting here...

[bleeth]

The ultimate decision is up to you but I have opted for the larger rails and wheels from www.superiorbearing.com (http://www.superiorbearing.com) in my PRT rebuild. Since I am redoing the whole gantry as well and plan on running a smaller auxiliary spindle primarily for drilling I wanted the extra oomph as well as raising the gantry a bit. My table is a SB design steel one and I am also adding a 45 x 45 mm extrusion to raise it more. This is so I can get my final table height up further from the floor.

[oddcoach]

Shopbot now has replacement hardened rails I'm thinking about replacing mine with 10' ones extra size would be nice.
John

[knight_toolworks]

they cast a arm and a let from shopbot. shipping will be killer too.

[ken_rychlik]

There is a web site of a place where folks build their own cnc router that you may find helpfull. It is mechmate dot com
They grind their own rails with an attachment they make for an angle grinder. You may can use one of those things to grind yours down a little and dress up the bevel withought even taking them off.

[Brady Watson]

I would attempt to dress the original ones before I invested in replacement rails, which can be pricey. The original rails are steel & are easily dressed with a sanding block and/or appropriate file.

First, take a wire brush (motorized is preferred) and clean the rails, removing embedded material from the CNC cutting process. Then, file down flat, the apex of the rail using a file. As these rails wear, they get 'forged' downward, and the center of the rail gets formed into a ^ shape since the v-roller never touches this part of the rail. Then, take either a sanding block, or the file and smooth down the edges of the rail on a 45° angle - IF necessary. The idea here is to clean up the rails while maintaining the original shape. NEVER clean up the rails with a grinding disc. It is too aggressive for the purpose of 'tuning' the rails from wear. Steel is pretty forgiving, but take your time and pay attention to what you are doing. It doesn't take long to dress a pair of rails with a file & sandpaper. For those that have welded before, your body position is everything when trying to hold a line or get good feedback from your hands while using a tool.

-B

[harryball]

Unless you are looking for a project for your own enjoyment, I agree with Brady. Dressing the rails is fairly simple and personally fits my budget.

I dressed my rails recently, granted they didn't need much but a touch up, and it took me about an hour with a wire brush and a good file. After a good wire scrub I started by filing straight down the sides of the rails with the file almost flat but tilted just enough not to take the blue paint off. This cleaned the burrs created by the rollers that build over time. Then I gently worked the tops flat again. Then I went down the rails at the 45 degree angle.

FYI, I keep T9 on my rails and rollers so there is virtually no rust even where the rollers do not contact the rails.

/RB