Denham Lathe Restoration

Hi everyone.

My first posting apart from the newbie thing. I'm not a model engineer, but I am an engineer; my tastes tend toward the watchmaking side of things at the moment. Up until now I have been using my boss' machines at work to make my parts, and although that will still continue to be the case (at least in the short term) I have been looking to guy myself a machine or two so I can work at home a little. I don't have much money to play with so I ended up buying a much older lathe than I had initially wanted, and also very much in need of a makeover.

I bought a Denham MKII.

I'm posting some photos of the lathe before restoration. Actually, the machine is already in pieces, albeit in larger pieces in some cases. Unfortunately there are issues with the machine; missing plaques, play in the shaft holding the end gear, a very worn cross slide shaft nut, among other things.

The motor has a date on it of 1939, not sure if this is the date of the motor build or the machine build, it's one of the few plaques still in place.

I did check that everything worked before parting company with my hard earned but knew that work had to be done as there was backlash present, although the vee slides were pretty smooth.

You don't get much for your money in the machine tool world.

Now that I have the cross slide and top slide completely disassembled, and seeing the need for a new cross slide nut, I have been looking for a tap to create a new nut with. There don't seem to be any. The shaft is an older style Imperial square form thread and I can't find any taps out there so far.

Any help on this would be appreciated.

I do have a pdf manual though, so that's a bonus. Apart from that there don't seem to be any spare parts out there or, for that matter, many Denham lathes full stop.

Perhaps there are a few here.

Anyway, will post some pics of the disassembled slides soon and the weirdest looking shaft nuts I've seen yet.

Kris.

The cross-slide shaft is definitely square not Acme thread? Rare now, probably, but try someone like Tracy Tools who do stock ACME tools.

If you need replace both, if you can't obtain a square-thread tap, I'd suggest trying someone like HPC Gears, from whom I bought a length of 3/4" LH ACME rod to make a new leadscrew for my Myford lathe.

Yes, definitely square. I can get lengths of Trapezoidal threads quite easily. My cross slide shaft has a gear on it that is actually part of the shaft, not pinned or locked on in any other fashion. I guess I could splice part of the present shaft with the new Trap thread, although that isn't ideal really.

The "motor date" probably refers to the British Standard, bss170:1939 and not the date of manufacture.

OK: I might be able to help if you can quote the diameter, pitch and hand; but I can't promise anything!

Otherwise it looks as if you might need screw-cut a new nut on whatever other lathe to which you have access.

I think Bede Tools in Jarrow had a Denham in stock when I last visited a few weeks ago, looked to be a good machine don’t think it was that expensive either.

Hi Chris I have made a crossslide nut for my M Type Drummond lathe. It's made from Phosphor Bronze and I had to make a tap to finnish the thread. I made it from silver steel which I turned, screw cut cut the cutting edges on a mill then harden and tempered it. The nut had to be screw cut first to remove most of the material as the tap was only a finnishing tap. The thread was 1/2 inch dia. by 0.125 pitch.

David

Looks very nice work there, David.

It very much looks as if my screw is also worn so am looking at options regarding that. Probably I will replace the thread part only with an ACME thread bar. Will have to look at suppliers of that here in the UK, although Roton do that a lot and some bar and one nut, with postage, is around 115 pounds, what the added duty would be on that I'm not sure.

Thanks for the link, will check them. It does seem that my screw is also worn, so will need replacing.

I'm curious about my cross slide lead screw. It's a two start thread, is there any reason why they would have a two start for a lead screw?

I would have thought that It would double the area of wear surfaces and prolong the accurate life of the thread.

There's a fellow who advertises manufacture of new feed screws and nuts on Lathes.co.uk:

http://www.lathes.co.uk/page3.html/

just after the row of asterisks.

You may be right there, doesn't seem to be any other reason for it.

Thanks, but I bought a length of ACME thread and will splice it with the lead screw at some point. I also have a tap and plenty of Bronze here to make the nut from.

Is it part of the original machine? If it is any idea what the lettering on the plaque means?

Plus, any ideas where I might find the plaques that fit on various parts of the Denham? I think I might have 1, that's all, the rest are MIA.

Not part of the original machine. Likely an asset or inventory number. An interesting possibility is the lathe was fitted to a ship sometime during or after WW2. Shipbuilders worked with Yard Numbers, not names, because names were were allocated later by owners. (The Titanic was Harland and Wolff Yard No 401, and the QE2 was John Brown Yard No 736. )

Most vessels of any size had a decent on-board workshop, and a lathe was essential.

The 1939 date on the motor refers to British Standard 170, not when the motor or lathe was made. No matter - the machine is still approximately of WW2 vintage.

Dave

Don't see why number of starts makes any dufference

No, it probably doesn't. I guess I was just curious as to why, even doing my job as an engineer I don't see many multi- start threads.

Thanks for the information. Very interesting if it was on board a ship, adds to the history of it. I figured, given what you and others have said here, that it started life around the WW2 era and I'm curious as to the history of it all.

Any help with the plaques etc would also be a help. Not sure how I might go about making those things from scratch, it would be a lot of work regardless.

An update on the restoration. I was packing most of the parts away until I was able to give more time to it, but then found the head sitting there, way too heavy to lift and to awkward to park on a shelf with the limited equipment, so decided to start restoring it instead. Took everything apart, spindle, pulley shaft, inter shaft, gears etc...cleaned the casting down, stripped off the bearings (7 - 4 BB, 1 Roller, and 2 Angular Contact) , and found them all worn like a bag of nails. It seems that they were the original bearings; Hoffman and R&M, British manufacture, expensive at the time I would guess, given that if you can find them they are very expensive now.

Hoffman and R&M got bought by RHP, which is now part of NSK, such are the machinations of the corporate world.

Anyway, having bought a couple of bearings I'm finding that the sizes are slightly larger; 0.0005" on the OD's and a little less on the ID's. 1/2 a thou is usually the preference for interference fit on bearings so decided to measure the bores on the head to find out what I was working with, found some surprising results, bores smaller than I expected. So, will have to grind the OD's of the new bearings so they fit properly, which isn't as much of a problem as it is a PITA, and timer consuming, but not as bad as re-boring the head.

At least you can buy Imperial bearings these days, or the metric equivalents. Just can't afford to buy RHP bearings for all the replacements. Will probably buy NKE for the AC spindle bearings but even they are £60 at least for one. I have bought one Hoffman bearing so I could check the size of it, just to make sure the size difference wasn't because it was an old British bearing.

I wonder if bearing fits/tolerances were different back in the day, maybe that's why I'm seeing different sizes, or they built the head and shafts around the bearing sizes they had then. Some of the bearings did have their sizes etched on them.

I've re-sprayed the head casting and decided that the handles were getting a coat of paint as well, as they were badly corroded. Still working on some aspects of the spraying process and haven't got all the photos of it yet, but promise they are coming.

The plaque I asked about before I took off while I was looking at the bed and stand. I'm also going to restore that so it gives me somewhere to put the head when it's finished.