Hobbymat top slide repair

Had an unfortunate incident involving my lathe's top slide and a concrete floor. Ironically, I've already bought some floor matting to prevent this sort of thing, but haven't installed it yet, wanting to do a proper organizing/cleanup first!

Is this fixable?

Metal-filled epoxy, brazing (silver soldering)? I am waiting for silver soldering hearth and silver solder from Cup Alloys. But I only have a handheld MAPP torch from Rothenberger, and the base is quite heavy, not sure it would be enough heat.

A friend advised against welding as it would likely warp the part.

Another (ugly) option would be to just make a pair of clamps to hold the top slide down - similar to the sort used on a milling table.

If thinking about a replacement... I once saw a top slide on eBay for around 130 EUR. Or perhaps a replacement top slide base could be made to order.

Just an instant suggestion: could the broken flat part be machined off the dovetail in favour of a screwed on steel replacement?

Yes welding will warp. Glue is unlikely to be strong enough. You could make a tidy enough compact clamp. An inverted top hat with hole down the centre could be made to work.

PS or an inverted L shaped block might be even tidier.

ega, do you mean the replacement would screw from the bottom (can imagine that), or from the side (more difficult to imagine)? In theory it could be possible. I don't have a mill, so machining off would probably have to be outsourced (unless I, as a beginner, just don't see the obvious way to do that in the lathe, without using the top slide as the vertical slide).

Hopper, I actually thought epoxy could work, but perhaps I'm wrong Is brazing/silver soldering out of the question?

For the clamps, I imagined something similar to these clamps: https://www.rcm-machines.com/en/machine-accessories/clamping/clamping/1-pair-clamping-kit-50-x-20-x-9-mm,-max.-m8/rcspw165

Could be easily produced by filing and drilling.

It might be worth contacting Essel Engineering, their website says "As a further service to modellers, we also supply a limited range of spare parts for the 'Hobbymat' machines. Otherwise I wonder if the SU300 Masterturn part will fit?

Brian G

EDIT: Unless perhaps one of these clamps similar to that suggested by Gene happened to be the right size?

Edited By Brian G on 01/06/2020 11:27:48

Yes you could cut and file somthing like that. I reckon you could make a tidy enough clamp like your link, maybe even curve it to match the shape, that would be far more durable.

Both glue and silver solder are going to suffer from the same problem of a weak joint design that is going to stress the glue or solder. Unlikely to survive repeated tightening and loosening. But silver solder might do ok if you use a large flat washer on top of the clamp down bolt. Trouble is getting it all to sit perfectly flat during and after soldering. Could be tricky but you could file it back flat if you had to. However if it is curved upwards, clamping pressure will eventually snap it.

Brian, thanks for your suggestions. I've e-mailed Essel Eng, Emco Machines, and Teco Znojmo - the manufacturer of the SU300, regarding availability/pricing of the spare part. The clamp you mentioned is too tall, but it really should be not a problem to make one. It would as well be good exercise to atone for my sin of dropping the topslide.

Hopper, I see your point about alignment difficulties of the silver soldering. And I guess the joint wouldn't be very strong because of lack of the gap for the solder to flow into.

I didn't attempt a detailed proposal as I don't know the precise construction. But assuming the normal arrangement of a male dovetail with a base for fastening to the cross slide then, yes, I would be thinking of screwing (and, perhaps, bonding also) from the bottom with countersunk screws. The replacement base could well be made from gauge plate (ground flat stock) for flatness but mild steel would be fine, too. You would obviously need some way of turning or milling off the broken area - perhaps even a toolpost mounted direct to your cross slide - and similarly for making the replacement part. The arcuate slots could be produced by drilling and filing if no other means is available.

All that said, the clamp-based suggestions seem perfectly workable as the broken off area seems to be doing little more than supporting one side of the clamp bolts.

Good luck!

Edited By ega on 01/06/2020 12:10:18

It's a fairly standard arrangement, as per the diagram below.

Please bear with me as I'm a beginner. I could bolt the toolpost directly to the cross slide, by making an appropriate spacer with holes in the right places. But how would that help mill away the broken-off area (without also milling away the other side)? I thought you were talking about using the lathe as a mill. I have the original Hobbymat angle plate, to which the top slide can be screwed to, serving as the vertical slide. But if I want to machine the top slide's base itself, I'd have to somehow clamp it horizontally directly to the angle plate at the right height, and use the cross slide traverse for milling, right? I could use an appropriate wooden block as a spacer and a couple of clamps to hold the base to the angle plate. Does this sound reasonable?

From what I understand, it's going to be a lap joint, right?

.

That seems by far the best solution

Just tidy-up the broken edges and clamp the thing down.

The section that has broken off doesn’t look sufficiently strong to be other than a convenient spacer anyway.

MichaelG.

L clamps will be fine. Trim the broken ends smooth. I find with mine the slots fill up with swarf which is hard to get out with a brush so look on it as a bonus your swarf trap has been removed! An unintentional upgrade!

Paul.

As Michael says it doesn't do a lot and the two screws can get in the way of turning some larger items between centres too. Consider making steel L pieces in which a shortened and turned down head sits in a recess to avoid the above interference. It would actually be an improvement on the original.

BUT

take extra extra care that the screw doesn't go through and bottom out on the top of the saddle and push up the slide and break that.

Thanks guys, it's good to hear that the clamp solution is not that bad and can actually be good.

I will make sure to make the clamps look nice to remind me of my clumsiness/stupidity!

Bazyle, I don't quite get how I could make the clamps sit lower than the original screw solution. Well maybe 1 mm lower. Can you please make a sketch of what you mean?

Gene:

I gather you are going for the clamp solution which may well be best.

Looking at your drawing suggests that there may be insufficient meat in the part to allow the whole of the base to be replaced (which is what I had envisaged) ie not sure if there is room for the retaining screws; and, perhaps, that milling it off would remove part of the through hole for the leadscrew. I don't think a stepped or lap joint would be a sound solution.

I agree that the original design with its cored slots is a bit vulnerable.

ega: I see what you mean now. Replacing the whole bottom wouldn't work, I'm sure. There's also a centering pin there on the bottom, I imagine hardened, which fits a matching hole on the cross slide.

I will go with the clamps solution, and if I hear back from one of the companies who might provide a spare part, will consider getting a new one if not very expensive.

Thanks everyone!

Look forward to hearing how you get on - perhaps an "after" photo?

If the pin in the base is hardened it's likely to be an inserted steel item - sorry my initial suggestion wasn't clear.

Yes I'll post back when I solve the issue! Thanks again

I don't know where you are located but hobbymat parts are fairly common on ebay uk. Infact a top slide sold yesterday for £25. Though it was in poor condition.

True parts are often on ebay but also often at what I consider rip off prices.

Anyway how I would proceed. Steel is chap and if the first version doesn't work you can try again. Steel is also stronger than CI so can be thinner. During the machining of the repair you can hold the slide with big washers under the bolts.

The M5 bolt head is 8mm dia and the slot was 9mm, tapering so without the washers it might go into the slot. machine off a mm from the dia to be on the safe side and file the edge of the slot square to give max clearance. The allen head hole is 4mm deep so take a bit off the top say 1mm.

The broken bit is 7mm thick/deep. Steel is strong and you can make a bigger area so start with a bit of steel 8mm thick and long enough to cover both holes together. Flycut or mount on a faceplate to 'bore' a recess of 6.9mm along its length matching the curve of the slot say 2mm deep leaving only 1.1mm that fits 'above' the topslide base over the curved bit. Although only 1.1mm thick it will be 20mm long so plenty strong enough.
Take cross slide off so you can spot through for the two 5mm bolt holes and drill them.
On the top drill a counterbore of 8.5mm for the bolt head for each one right down leaving only 1 or 2 mm at eh bottom of the hole so the head is right down out of the way - again in steel this is plenty strong enough.