Removing saddle from vintage Drummond lathe

I have a vintage Drummond "flat bed" lathe which I am dismantling for restoration. I have previously referred to it as a B-type (the lathe bed is marked "Mch. B" but it has been suggested this lathe model is a "pre-B".

I am now down to the last couple of screws and the cross slide saddle. The lead screw and drive shaft have already been removed.

The saddle will not slide off unless the leadscrew full nut is removed, but there is no obvious way to remove the nut. The nut appears to be original to the lathe; it is stamped "10" in common with other parts of the lathe and is in excellent condition with very little wear. I'm not sure if the nut is a press-fit into the saddle or threaded in somehow. The centre punch mark (see photos) suggests to me that it may be threaded, maybe.

Any ideas?

I think it is a tight push fit in order not to contribute to play in that axis. Mine does not have a centre dimple but has a steel sleeve evident suggesting it was bushed to tighten it up. It is also very slightly proud of the surface while yours is flush. I suspect yours has been peened to tighten it.

The dimple does not mean it was threaded but might have been turned to size between centres as that was common back then. Often older parts have a boss cast in to make the centre, perhaps opposite a turned section which can look a bit out of place subsequently. (the over arm of some small die filers is a very good example - see my Excel die filer album)

However I'm interested to hear your findings as I still have to take mine apart sometime 

Edited By Bazyle on 19/09/2022 18:15:43

This is a tricky one. Thanks for posting so many good photos.

I don't think that is threaded, there isn't enough of a non-round edge to show there is one. A few defects yes, but the brass bit is very round.

The dot probably denotes which way round it faces, especially if the nut can be adjusted.

The dents in the surface make me think its been riveted in, or rather "upset" to fit tight into the hole. If so it will be a super-pain to get out as neither hole or stub will be round. If you can remove the top mm you might confirm this theory or disprove it, you may see signs of a thread, or it may come loose.

Good luck, I am sure there is value in doing so thorough a job.

I take it you have removed the gib from the front of the saddle.

Yes, gib strip and all gib strip screws removed. The saddle won't lift away from the dovetailed bed.

If it's a push fit removal could be tricky. I will have a look later to see if I can press it out with a custom tool. It would be good to know that it will press out before applying pressure!

I had another look at the saddle to see if I could make a tool to press the stud through. I then resolved to try with a punch and hammer. With the saddle loose (gib strip removed) I added some packing between the saddle and lathe ways and then tried a few gentle taps... success! Just be sure to move the saddle to the tailstock end so the leadscrew nut can be removed.

Great news, now if you can make a deep chamfer in the hole, you can fit a matching washer and a screw to hold it when it gets rebuilt.

I havejust realised that the nut os not for the cross slide, but offset to the right for a central leadscrew. Is there anything to keep the swarf off the leadscrew? Maybe a tube on the left of the saddle which just stops short of the left end of the gap?

Edited By old mart on 19/09/2022 21:12:22

You DO NOT need a screw and washer to hold the nut in. Just refit it exactly the way it came out, peen very slightly if it is loose in the hole at all. It will be overconstrained , it may jam at worst , and at least will wear prematurely if a washer and screw are fitted. Not a good idea.

I tend to agree with Jeff about the screw / washer idea. I've come across many similar setups over the years and have never seen one with a holding screw.

As they are fitted, they provide a tiny amount of 'wiggle room' for alignment and so are naturally self-aligning. 'Locking' them would probably result in excessive wear in the long run.

regards Mike

Excellent analysis, Jeff and Mike

MichaelG.

You can see the other centre in the base that they needed for turning the spigot. This method would have been a lot faster for production that trying to set up in a (uncommon at the time) 4 jaw chuck. Interesting also to see the hole in the base that the nut needs for removal. I wonder if they thought of that in the first pattern for the prototype.
The Boxford cross slide nut has a threaded hole down the middle, a hole going sideways and the idea is that a suitably shaped screw pushes a short wedge ended rod against the side of the hole to hold it.
The drawing for the assembly that is around on the net shows it the nut the wrong way round so that the cutting force is taken by the rod not the larger area of the spigot. I don't recommend this method.
Also some lathes have a hole down the spigot to the thread for oiling but that attracts swarf.