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Crosshead Guide Material

Posted: Tue Apr 14, 2020 11:40 am
by rhbroehl
Hi,

I have to build 4 crosshead guides for me LE 0-4-0. They are 3/8 x 1/2 and I wondering if I could use key stock material for the guides. The material has fairly tight tolerances so I would think it would work.

Comments? Other ideas?

Thanks

Rob

Re: Crosshead Guide Material

Posted: Tue Apr 14, 2020 1:03 pm
by Mike Walsh
Probably work ok.

For the Allen cylinders that I'm machining at present, I picked up some 4140 prehardened material. Already ground to size. I think that'll hold up OK.

If you're interested in that route, check out McMaster #8892K47. I haven't tried machining it yet but hopefully will be able to in the next few months. Shouldnt be too bad - cut to length, drill a few holes here and there..

Re: Crosshead Guide Material

Posted: Tue Apr 14, 2020 3:32 pm
by hoppercar
I also used 4140 prehard....it has a rockwell around 35 to 38 I believe...which is still plenty soft to be machined.....but has better wearing characteristics than just plain 1018 c.r.s.

Re: Crosshead Guide Material

Posted: Tue Apr 14, 2020 7:06 pm
by ALCOSTEAM
Actually been working on a set of guides for some wagner cylinders and used 4140 crs. I bought some cobalt end mills but would go carbide next time..
Another thing to remember about 4140 crs is it will pull as you machine it.. take small cuts equally on opposing sides to keep the pull equal.

Re: Crosshead Guide Material

Posted: Wed Apr 15, 2020 9:28 am
by Benjamin Maggi
I used keystock on my engine's crossheads. A word of warning: I purchased my steel through Metal Supermarket and they shipped me keystock that looked like it had been sheared from a larger piece. It is hard to describe, but it wasn't perfectly square and such that you would expect from Keystock. They then replaced it with the right stuff when I went back.

Re: Crosshead Guide Material

Posted: Wed Apr 15, 2020 10:29 am
by BClemens
I've noticed that some of the 'big box' stores that sell lengths of steel of various types and sizes are selling 'angle' and 'channel' that are nothing more than sheared sheet metal braked to an angle or channel. Finding the small hot rolled angle and channel seems to be getting rare.
bc

Re: Crosshead Guide Material

Posted: Wed Apr 15, 2020 11:02 am
by tetramachine
4140 PH is closer to 25-28 HRC in hardness. Key stock may well be on size, but is usually made of junk steel. If you want On Size material, look at any of the tool steels. they are all sold in annealed condition, and can be on size to a few thou. Look at the online sites to find you needs. Sites like OnLine Metals, Yarde Metals Drop Zone was great deals on drops (Cutoffs), MSC and Mcmaster. Hardware store or Big Box store I would not touch their metal.

Re: Crosshead Guide Material

Posted: Wed Apr 15, 2020 2:55 pm
by BClemens
If you don't need a piece of structural steel with certs, and you have the ability to look at it and make a judgement about what it is (mill carbon coated for example) and judging the method of forming (hot rolled or braked), you can probably purchase an adequate piece of angle iron from a big box store. That is not to say that the purchase is not a rip-off considering the price at the big box store. If a piece of 'key stock' was ordered and had the tell tail indication of being sheared we would probably stay away from that supplier too (although referenced made it right). Key stock for crossheads is probably not a wise choice because it is very low carbon and is a basic soft steel intended to shear in situ. Not meaning sheared to size before you use it - not very likely anyhow. It is nicely put to call it junk steel - we always called it crap steel and doesn't even weld well. Off the peach crate.. just saying...
bc

Something else about soft steel, brass or even zinc. It will 'charge' or become embedded with material particles (dirt grit - or - diamond dust) that will cut another harder piece of material (steel). Once embedded it becomes the 'wear' part and will cut the 'worn' part to over tolerance. Best the other way around for crosshead guides rather than crossheads. Crossheads are (on full sized) made to adjust to make up for wear. Make the crosshead guides out of hardened steel or at least hard surfaced steel that will not embed.

Re: Crosshead Guide Material

Posted: Wed Apr 15, 2020 10:08 pm
by Greg_Lewis
BClemens wrote:
Wed Apr 15, 2020 2:55 pm
...

Something else about soft steel, brass or even zinc. It will 'charge' or become embedded with material particles (dirt grit - or - diamond dust) that will cut another harder piece of material (steel). Once embedded it becomes the 'wear' part and will cut the 'worn' part to over tolerance. Best the other way around for crosshead guides rather than crossheads. Crossheads are (on full sized) made to adjust to make up for wear. Make the crosshead guides out of hardened steel or at least hard surfaced steel that will not embed.
This ^ ^ ^

I made my guides from common CRS and after one run around a track I found them to be scored even though they were well lubricated. The crosshead shoes were 660 bearing bronze.

Re: Crosshead Guide Material

Posted: Thu Apr 16, 2020 1:50 am
by Lovesthedrive
So all this chatter of why Key steel might be bad. Yet no suggestions of what should be used as an alternative? Seems like too many armchair warriors here.

Re: Crosshead Guide Material

Posted: Thu Apr 16, 2020 1:56 am
by Harold_V
Perhaps a reread would help. Heat treated chrome moly was mentioned (4140) and provides an excellent wear surface, plus you can achieve the flatness and squareness desired.
I fully agree with not using keystock. It isn't hardened, and may or may not be flat and or square. Mild steel is notorious for galling. Not a great bearing surface.

H

Re: Crosshead Guide Material

Posted: Thu Apr 16, 2020 8:24 am
by PeterCraymer
Often times keystock is plated as well, so that is another thing to look out for. I used 1/4 x 1/2" HRS for my 10-Wheeler and used the stock Allen Models cast bronze crossheads and have no problems after 7 years of running. Sure was nice not having to do much machining on those parts!