Slitting Saw Arbor Recomendations

Well, I was able to center the stock with only a 3-4 thou runout at the end with no support. See photo. There's a lot of stick out.

I couldn't face it off, of course. So, I used a center drill for the tail stock live center. All seemed to work okay.

I put the live center in and I'm getting a LOT of runout, at least 30-40 thou. The whole tail stock is moving. Remember this is a mini lathe.

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If the tail stock is moving independent of the ways, something isn't right in the tail stock. If it's locked down, it shouldn't be able to move without bouncing the whole machine around. I've never used a mini lathe, so perhaps I'm missing something. My lathe is a "small" I guess. PM1127. So it might be different, but I can't imagine any reason the tail stock should move like that. Even for a mini lathe, that really doesn't look like a huge work piece. I've run 3x12" in my lathe which should be similar in scale.

Keep in mind, raw stock is not guaranteed to be round in most cases. You can get ground bars that are, but that looks like mill finish, which is sort of round. 40 thou wouldn't surprise me. If it's not a machined surface, you can't trust measurements on it.

I would figure out the tail stock, it should be solidly held down. Then if you still can't get runout that works for you, use a 4-jaw to adjust it in a bit better. But I think you will get it running smoothly with the tail stock. Or run between centers if you have the gear for it. But you still need the tail stock working properly for that.

You might also have to adjust the tail stock once it's holding down properly. At least line up the points on a couple of dead centers to get close. There is a lot of info about aligning them out there.
 
It doesn't normally move, but the hole I drilled must be out of center by more than I thought. I'll try the 4-jaw chuck and misalign it the same amount. This should be fun until it's round again.
 
The mini lathes do have issues with rigidity. My Atlas tailstock wiggles around too with heavy forces. The quill is not precisely fit
-M
My hunch is you could make the arbor shorter and/or modify the design to make the job easier and fit the lathe better
If we could see a sketch of the proposed dimensions it would help-
 
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I wonder if you could just make it in 2 parts? Make the shank extend into the 'backing plate' part of the arbor (and have the screw threads on it as well), then pin/green loctite the 'backing plate' in place? So of that 1.5" part, you'd only need a ~200 thou thick piece, then take a ~3/4" part to make the shank.
 
Do you have jaws for it that have a longer gripping surface? It might help some. The 4 jaw might help as well.

An up side to a two piece approach is that you don't have to knock 750 thou off the 2.5" length. That would take me a while on my lathe. A mini must need a really long time. That's when you want an Abom lathe, do that in a single pass. lol. The down side is that it would be harder to get concentricity. Perhaps put it together and do final turning as one part.
 
I'm using my 4-jaw chuck which has a deeper jaw and slowly turning it to remove the drill hole so I can reestablish another one that's centered better.

I'm pretty jealous seeing Joe Pi and Abom taking massive cuts on the lathe and mill. It takes me forever to get rough stock to dimension.
 
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