Material selection for lathe replacement part

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jasongetsdown

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I have a Dalton lathe circa 1914. It’s a beautiful machine, but part of the compound slide is cracked. I would like to make a replacement, but I’m not sure what material I can use.

The part has a round pocket on the bottom that sits on a circular boss to rotate the compound, and on top are dovetails that engage with the top of the compound where the tool post mounts. All this to say it has bearing surfaces that I will be scraping in.

the original part is cast iron as far as I can tell. Not many suppliers sell cast iron, but there is a product called dura-bar that makes continuous cast gray cast iron bar stock. Problem is it’s expensive, about twice the cost of cold rolled.

So my question is, do I need to use cast iron? Can I just use cold rolled? Should I use something tougher like 4140? Can any steel be scraped like cast iron?

Thanks!
Jason

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jkimberln

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I would use cast iron. You can buy a satisfactory piece from McMaster-Carr. Speedy Metals also has cast iron.
 

Charles Lamont

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Looks like a very nice shop you have there.

I think that lathe deserves a piece of cast iron. It would be authentic. Iron has better damping properties than steel.
It would probably wear better. Arguably perhaps, I would say it would be easier to make.
 

jasongetsdown

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Looks like a very nice shop you have there.

I think that lathe deserves a piece of cast iron. It would be authentic. Iron has better damping properties than steel.
It would probably wear better. Arguably perhaps, I would say it would be easier to make.
Thanks! I work in a cabinet shop so I was looking for a small lathe I could fit at my workbench. I still need to build a proper table for it.
I’m going to pull the trigger on a piece of cast iron from McMaster.
 

trlvn

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I think steel-on-iron would lead to extra wear so I agree that a cast iron part would be superior.

Just curious, how did the damage happen? Was it due to the chuck crashing into the compound at speed? Surprised at the level of damage on what looks like a pretty small lathe.

Craig
 

jasongetsdown

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I think steel-on-iron would lead to extra wear so I agree that a cast iron part would be superior.

Just curious, how did the damage happen? Was it due to the chuck crashing into the compound at speed? Surprised at the level of damage on what looks like a pretty small lathe.

Craig
Good question! Unfortunately I acquired it this way. Maybe it was dropped? There is a bolt hole for the clamping action through the side of the casting where another crack is developing. Most of what you see is a rough attempt at a repair by a previous owner. They didn’t get the bottom flat afterwards and it no longer clamps very hard so it chatters like crazy when I take anything more than a two thou cut in brass.

The design was never very good so part of the challenge is to come up with a better way of clamping for the new component. It just grabs a cylindrical boss on the cross slide. There is no t slot or other means of holding it down so it has to grab that boss pretty well. Any suggestions or examples of how other small lathes do it are welcome.
 

SmithDoor

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Good question! Unfortunately I acquired it this way. Maybe it was dropped? There is a bolt hole for the clamping action through the side of the casting where another crack is developing. Most of what you see is a rough attempt at a repair by a previous owner. They didn’t get the bottom flat afterwards and it no longer clamps very hard so it chatters like crazy when I take anything more than a two thou cut in brass.

The design was never very good so part of the challenge is to come up with a better way of clamping for the new component. It just grabs a cylindrical boss on the cross slide. There is no t slot or other means of holding it down so it has to grab that boss pretty well. Any suggestions or examples of how other small lathes do it are welcome.
I have used steel for sliding parts against cast iron.
Note add oil groves.

Dave
 
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