Linear Guide Rail replacement info needed

Good morning all!
My company's fab division has a very large Peddinghaus saw which uses linear guides to position the sawblade depending on material size. One of the rails broke, and I have been tasked with repairing/replacing it.
The saw is very old, so I'm unsure I will be able to find a replacement to buy from Peddinghaus, although I haven't checked yet.
If I need to machine a replacement, I have several questions: What material would you use? Broken pc seems to be cast and machined/ground. 4140 or tool steel needed? I have no idea.
I can model the profile, so I feel like I'd be able to machine a replacement, although the length will require me to machine in 2 setups each side.
Am I going about this all wrong?
Any ideas would help! Thanks!

Pix please.

Wipe the grease off the rails and blocks and see if there are any identifying markings. A little complicated figuring out EXACTLY what you have but replacements are readily available.

That rail installation is pretty lame. The rails are twisty wet noodles until you push them against a flat shoulder and bolt them to a flat surface. You will need to snug up the bolts and tap into alignment while indicating it to get them straight. Only one side of the rail is to be used as a reference, like I said earlier, details, details, lots of details.

Those seem to be a relatively new profile rail system, and I doubt the rail is cast, but who knows. I'd guess the screw where the break occurred was loose, allowing flexing of the rail at that point, and it fatigued to failure. WAG only...

It's possible the same rail system is made today, but if it's really old maybe not. There is a good chance that a similar rail and truck is available that will swap in, so you want to measure the height of the over-all system, the mounting hole pitch on the rail, and the size and mount method for the trucks. Then see what modern parts will swap in.

Replace everything, don't try to cheap out by only replacing the broken rail. Put some effort into alignment, that will help maintain accuracy and useful life of the trucks and rail. Don't forget to lubricate the trucks, and to check fastener tightness on a regular basis.

Those linear rails are typically made out of hardened steel, think ball bearing race. Hard but brittle. They are also ground to a high level of precision, so making it in house would be close to impossible unless you have highly specialized equipment.
Check THK, NSK and IKO for the identical dimension rail and block, many of them are interchangeable between manufacturers.
+1 to #5 on alignment
Make sure you thoroughly clean the mounting surfaces before installing a new rail, both rails must run in parallel to each other, use 0.0001" dial indicator and align as close as possible. Assembled stage should roll almost effortless. Any tightness indicates very large local forces which will cause premature wear

Rails are case hardened only at the races, otherwise pretty soft. Lots of hidden details when selecting a rail block combo, LOTS!!! HiWin is another source, the best bang for the buck I found when I replaced the ones on my mill. Rails and blocks from different manufacturers are interchangeable, except for shoulder heights, block lengths, and a few other "little" details that can bite you in the ass hard when you go to install.

Torque all screws down to proper specs. I say this because proper torque was not nearly as tight as I expected.

DavidScott said:

Rails are case hardened only at the races, otherwise pretty soft.

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I've seen both case hardened and through hardened rails. Considering it did not deform but snapped like cast iron, very likely this particular one was through hardened.

One more clarification regarding interchangeability - both rail and block must be from the same manufacturer, as race geometry, ball diameter, etc might be different.

And just a word of caution, many block designs would spit the balls out allover the floor if you slide the block off the rail.

DavidScott said:

Torque all screws down to proper specs. I say this because proper torque was not nearly as tight as I expected.

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Yeah, I'd guess it's to minimize hoop stress widening (or otherwise deforming) the rail around the holes.

What I don't get is that many of the rail systems use a much larger pitch between holes than I think is ideal. I've got over a thousand feet of linear rail here, from a variety of manufacturers and in different sizes, and almost all of them have a ~4-5 to 1 ratio between rail width and hole C/L. A few examples are about 2-3 to 1, which I consider a better design choice for loaded rails, especially vertical, but they're the outliers.

If I were designing rails, I'd use about a 2 to 1 pitch, but a one size smaller screw. I expect I'd have less stress around each hole, more intrinsic stiffness in the rail, and better stability in the system.

Edit: I should revise my width to pitch estimate, it's probably closer to 3 to 1 for regular rail, and 2 to 1 or less for the close pitch rails. So I'd do 1 to 1, slightly smaller screws.

the saw manual (if you have it) will give the pedinghaus part and manufacture part number. If it is old rail, updated because bearing companies do this for fun, then they will have identical height with blocks and hole pattern. Does not matter to much in your case, both rails and all blocks need replaced. Hiwins are going to be best value for the precision (lack of comparatively) saws use.
pedinghaus will likely have them, or known replacement on hand, fed ex them next day.