Atlas 618 Spindle Material

[mvagusta]

I have been working steadily on the Atlas 618 CAD documentation project and am now checking the drawings for the M6-31X headstock spindle assembly (see images below) and have a question on the material for the M6-31 spindle itself. The factory drawing I have calls out SAE 1112 steel, which is soft and doesn't appear to be heat treatable. It is also now considered obsolete. Does anyone know for sure whether or not the material is heat treatable? Any suggestions for an alternative material? I have experience with Graph-Mo and 4140 for similar applications. I have also included below some images of the assembly itself. Feedback on any of the notes or anything else would be welcomed. Checking one's own drawings is always a little tough. Here is a link to the original project thread: Atlas 618 CAD Project

 

[DavidR8]

Wow, those are amazing drawings!

 

[pontiac428]

If you want the OEM correct steel, it's called 10S20 today. If I wanted to make a new spindle, I would choose something closer to 4340.

Impressive CAD work, I am sure a lot of people will appreciate it.

 

[machinistnoob]

...that's, looking really good.

 

[mvagusta]

If you want the OEM correct steel, it's called 10S20 today. If I wanted to make a new spindle, I would choose something closer to 4340.

Impressive CAD work, I am sure a lot of people will appreciate it.

Thanks to you all for the complements.

I was a little surprised that the spindle was made from a low-carbon steel and so soft. I once worked for a company that made stainless steel band clamps, and the plant was full of custom-designed machines that automatically made them from a coil of strip. The plant ran 24 hrs/day and those machines got a workout. We used 4140 for many of the machine components, including the spindles. We heat treated them to low 50's on the Rockwell C scale to increase hardness and toughness while avoiding brittleness. In looking at the properties of 4140 vs. 4340, they seem much alike. I have two questions:

1. Why would one choose one over the other?
2. What heat treatment would you recommend for 4340 in this application?

 

[wa5cab]

Unfortunately I don't know the answers to any of your questions. My only suggestion would be to call Clausing and ask for either of the McNett (may be spelled McNutt ) brothers and ask them if they can find out what material was actually specified on the last order placed for the 618 spindle.

 

[pontiac428]

Thanks to you all for the complements.

I was a little surprised that the spindle was made from a low-carbon steel and so soft. I once worked for a company that made stainless steel band clamps, and the plant was full of custom-designed machines that automatically made them from a coil of strip. The plant ran 24 hrs/day and those machines got a workout. We used 4140 for many of the machine components, including the spindles. We heat treated them to low 50's on the Rockwell C scale to increase hardness and toughness while avoiding brittleness. In looking at the properties of 4140 vs. 4340, they seem much alike. I have two questions:

1. Why would one choose one over the other?
2. What heat treatment would you recommend for 4340 in this application?

4140 and 4340 heat treat the same, and in most ways they are interchangeable. The reason I would select 4340 is it has nickel, which in addition to stabilizing properties makes the 4340 more corrosion resistant. I always assumed my Atlas spindles were 4340, because they were always bright and shiny.

By the way, the "S" in 10S20 is for Sulfur. It machines like leaded steel because of that, it's a good lubricant.

 

[mvagusta]

Thanks again. I'll add 4340 to the list of alternate materials. I think I might also add 17-4PH H900, one of my favorite materials.