Restoring (hopefully) my new Smart and Brown SAB

[Ben17484]

Typically the tailstock is slightly higher than the headstock to allow for some wear. There are no height adjustments in most lathes. Only way to adjust the height downward is to machine the tailstock which is doable but tricky to get right. My mini-lathe is similarly high. My 10x22 is closer to the correct height.

In most cases, the best you can do is to adjust the horizontal offset to zero and live with it. But us being tinkerers we should be able to machine it to get it right. The risk is adding more error than before. We want to reduce height only but not to add yaw or pitch over the full travel of the quill. It's not that easy since you want the tailstock assembly to be true, but you can't assume that the individual pieces are true at all. My mini-lathe tailstock base is not parallel to the ways but the assembly seems ok, save for height. I may try to fix it, since I can get replacement parts if mess it up too much. Not sure about your lathe.

Thanks WobblyHand. I think the picture isn’t too clear, but the tail stock is low here. I’ve read that you can adjust the tail stock up by shimming between the two parts of the tail stock, but I wanted to figure out how to find out if the headstock is level (I’ve had it off the bed whilst restoring). I guess I can indicate the top of the spindle whilst the base is on the ways?

(On a side note, shim stock seems expensive!!?! Maybe just in the UK?)


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[Beckerkumm]

Tailstock looks low and need some shims. Before you do that you need to determine if the ways have wear close to the spindle ( most do ) and how much the tailstock will rise as you increase the distance from the spindle. You may have to settle on a sweet spot ( range ) where you will use the tailstock most and shim it to match at that point. Dave

 

[WobblyHand]

You are in luck, in a way. Shimming will work for the tailstock height. For the headstock you can use Rollie's Dad Method to check alignment. Think it helps if the lathe is "leveled" first. I used a ground 20mm bar for this.

 

[Ben17484]

I’m trying to figure out what the other compound slide I got with the lathe is for:

I’ve not seen a set up like this before. Does anyone know how this is used or what it’s for?


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[Ben17484]

Thanks everyone for the advise on tail stock vertical alignment. I’ll get some shim stock, find the sweet spot along the ways and get the vertical alignment slightly closer to how it is now.


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[Ben17484]

Right, I finally got back to working on the lathe. The main thing left that’s stopping me using the lathe as much as I want, is the broken lever for changing the pulley:

Without this, changing spindle speed is annoying and takes a while.

First, I took the part off:

Suggestions to fix this had been 1) Remake the part or 2) build up the broken area via brazing.

I decided I don’t yet have the skills for number 1. Unfortunately I also decided I don’t yet have the skills for number 2 either.

That left solution number 3) Mig welding.

I know that mig welding cast iron isn’t strong and is brittle, but after some reading and some YouTube I read that it may be suitable as long as the forces are going to be low.

So I filled in the whole by building up the weld and above is where I got to to start with.

And then welded in a rod to test it out…. And it immediately snapped.

So now I’m back to one of the first two solutions. No idea which one I’ll go with. If anyone has any other ideas how to get this usable, I’d appreciate it.


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[Cadillac STS]

Looks like there is enough metal left to drill in and put in a threaded rod. For that you could drill all the way through to the center hole and have a long thread. Then make a shaft with a thread on the end and screw it in.

Would be a nice lathe project to make the handle that threads in. Make it look as if it fits with the rest of the machine.

 

[Ben17484]

Looks like there is enough metal left to drill in and put in a threaded rod. For that you could drill all the way through to the center hole and have a long thread. Then make a shaft with a thread on the end and screw it in.

Would be a nice lathe project to make the handle that threads in. Make it look as if it fits with the rest of the machine.

Great suggestion. I tried this out today and so far it’s worked ok.

I’ve just stuck a long M8 bolt in there for now to test it out. The last thing I want to do is waste time building a nice handle for this for it to fail after a few weeks. I’m thinking if this works out, I’ll build up the bottom around the bolt with weld again just so I can smooth it out and make it look nicer, and then I’ll probably make a handle to screw on to the top part of the bolt (cutting the head off it of course).


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[Ben17484]

Got the tail stock shimmed today

It’s lining up much better now.

I decided to check how straight the lathe cut. Over 20cm I am getting 0.3mm taper (which is a lot, right?) I’ve done no levelling yet and haven’t precisely aligned the tail stock. I’ll try another cut without the tailstock later to remove that from the equation. I did check the spindle run out before and it seemed fine (can’t remember exact numbers, I’ll measure later).

I’m not sure what number I should be hoping for in terms of taper over distance?


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[Ben17484]

Bit more playing and measuring.

Measured on the inside and outside of the spindle and I think this is pretty good in terms of runout? It’s a 0.01mm DTI and it’s moved a max of 0.04mm (if I’m reading this correctly) internally and 0.06mm externaly.

I then realigned the tailstock with the dead centre in the spindle itself (as pointes out by people here) instead of holding it in a chuck. It seemed to be quite far out.

After aligning the tailstock again I did another test cut:

And got a difference if 0.09mm (0.0035 inches) over 20cm (8 inches)

(Micrometer in inches on the bottom picture)

I’m not sure if I should keep chasing a better figure by doing some more levelling, or if this is good enough? (I realise that question is really subjective based on what needs to be made on the lathe).


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