Fix my (new) Lathe

This lathe is new with very few chip mileage on it.

I had noticed some play in the saddle, a slight lift, and set to looking for the problem. The gib was set ok so next I checked the fixed clamps. Oh, there's the problem.

I could slide a .01mm feeler gauge between the way and the clamp. Not sure what its proper name is. A .015mm gauge would not fit.

So removed the offending part and found this very nicely finished NOT !!

Tried to get a good picture. As you can see the surface that bolts to the saddle is not exactly flat. Probably not parallel either.

So my plan is to mill the surface to reduce the gap and hopefully improve the flatness, which should remove the play.

What do you guys think ?

Wait till I get to the cross slide !!

Hi Jonathan,

Is there a saddle clamp? If so make sure you don't remove too much material. If you remove the wiper, is there still play?

Thor

You cannot remove all clearance, or things will be immovable. There must be some clearance, even if only 0.025 mm to allow movement.

You are starting to fettle a hobby machine to improve the quality that you have bought.

Hobby machines are designed and manufactured to a low cost and affordable price..

They will not produce, certainly long term, to the leval of precision and longevity of an industrial machine. You will not be working the machine for 40 or more hours a week, week in and week out, close to its limits, that an industrial machine is made and expected to withstand.

Quality takes time to produce and control, which is why industrial quality machines are so much more costly.

By all means fine tune the machine, Lots of us make / add improvements. (The number of modifications made to machines make this obvious ), but keep a sense of proportion.

Howard

As it's new refer back to the supplier.

Robert Butler

Jonathan,

Hopefully, Hopper will see this thread soon and share the benefit of his experience.

Meanwhile … You might like to start reading here:

https://www.model-engineer.co.uk/forums/postings.asp?th=110038&p=1

MichaelG.

Edited By Michael Gilligan on 20/05/2022 12:41:23

Does it matter?

On a prismatic bed side-play and accuracy depend on the upper rail (or rails). The saddle slides on the rails and is unlikely to lift in normal operation because the cutting forces go down through the saddle and into the bed. Thus the clamps underneath needn't be anything special in terms of fit.

There are a few jobs, like parting off with an upside down tool in a rear tool post, and milling in the lathe, that might lift the saddle. What are you doing when the saddle lifts? There might be another way of doing the job.

Prismatic beds were controversial when they first appeared. Flat bed owners thought they were inferior. Nonetheless modern lathes seem more likely to be made with prismatic beds than flat ones. Ages ago I think MichaelG linked a document that explained the pros and cons, but I can't remember what it said.

Dave

Edited By SillyOldDuffer on 20/05/2022 12:59:26

Looks suspiciously similar to my ancient WM250 saddle clamp/guide. Have a look at this page on my website *** Journeyman's Workshop ***

John

That is about the right amount of clearance for there. Much less and it will tend to bind. As SOD pointed out, the block is essentially a lift plate that comes into play only if using an inverted parting tool, or a boring bar sticking way out in front of the saddle, or the top slide extended far foward thus causing the saddle to tilt. If you do machine any off that block, you will have to add shims to get some clearance back again. Journeyman's linked page has some good info and ideas on it re that block.

I thought I recognised that lovely puce paint colour. See the thread that Michael Gilligan linked to in his above post re the adventures of one forum member's Optimum lathe. The lift-plate clearance was the least of his worries. Bed was bent like a banana by about 1mm from what I remember and machining was all-round pretty ordinary. But with a bit of fettling it became a useful machine and he has made a number of very nice working model engines on it.

Never felt the need to measure the gap on my WM280 but while I had the feeler gauges out for something else this afternoon I tried them for size, like you 0.1mm will fit but 0.15mm is tight. I'll be leaving mine as is as the models that come off it seem half decent to me. You can see in this album what a lathe with tat sort of clearance can do

Agree with Robert Butler, you say it’s new, why are you not complaining to the supplier instead of taking the thing apart?

JB’s seems OK with about ten times the clearance you have measured. If that means anything, it means that the clearance is not particularly important.

I wonder if the OP has his numbers mixed up. Do they make a 0.01mm feeler gauge? That is less than half a thou' in old money.

If that's the saddle lock I'd leave it as it is, but I would ask for some new wiper felts as those do not look like they will wipe anything.

Of that, I have no idea. Rightly or wrongly, one can only rely on what is posted. Might even be units mixed up as well, for all we know.

Depending on the wear, you might get down to 0.05" at the left end and still not be too tight at the far end. That is nothing to worry too much about. The Smart & Brown model A that I use at the museum has to have at least 0.6mm at the left end to have any chance of reaching the right end without jamming.

I reduced the saddle play by milling the "press boards" on both my lathes. The play left will be about 0.01 mm or less.

On the small lathe, I also added 2 spring loaded ball bearings. They pull the saddle on the bed if the load is not to heavy. If the load is to heavy, the old "press board" takes over.
If the bed is worn, you need more play but the bearings still pulls the saddle on the bed.

These changes improves the repeatability/accuracy, especially when doing shallow cuts.

Also the yearly maintenance takes a few hours less because the play doesn't need to be adjusted any more.

For the foto's view my album (Carriage Saddle Press Board)

For the description PDF

Edited By Huub on 20/05/2022 22:10:12

Edited By Huub on 20/05/2022 22:12:24

Edited By Huub on 20/05/2022 22:17:15

Interesting that responses vary from 'send it back', to 'nothing wrong'!

To the 'send it back' brigade, I'd say it's foolish to go to the trouble of returning an item and starting a commercial dispute unless you're certain the machine really is faulty. Complaining about stuff that isn't broken makes you look like a plonker and is a complete waste of time!

Buying inexpensive hobby lathes, I don't think it unreasonable for half competent Model Engineers to fix minor issues themselves and to add value by making improvements. I don't think it's smart to expect a far-eastern hobby lathe to be as solid and well-finished as a professional machine costing 6 to ten times the price: you get what you pay for. My far-eastern kit isn't up to production work, but it does more than I need of it. I'd have sent them back if any had been duff on delivery - warped bed, damage, faulty electrics etc - but no need - they all worked out of the box.

I recommend taking a pragmatic approach. Rather than starting by looking for faults, and especially not by stripping down and jumping to conclusions based on hard to get right measurements, it's safer to use the machine to cut metal and judge it on actual performance. Then focus on problems that actually get in the way, using measurement and stripping down sparingly to identify the cause. Don't fuss unless it really matters.

Be aware good results are often got from equipment that isn't in perfect order, whether it be a worn ex-industrial machine, or a warty new hobby tool. Experienced operators routinely work around all sorts of workshop shortcomings: a complete set perfect equipment isn't needed.

Dave

To the 'send it back' brigade,

Who are these, Dave? The closest I have seen is to refer back to the supplier - which is certainly not to just send it back.

It may be possible that sending it back is a total non-starter - depending on the seller.

Correct! If an attempt to correct a fault without "reference" to the supplier is made potentially bridges have been burned.

Robert Butler

The 0.1 to 0.15 mm gap is not the issue. There will be more problems than that underside block. You will be better off to take it apart and see how the saddle fits to the Vee way. Then correct that if needed. The rear bearing block is the one most likely to be experiencing any lifting, especially of rear tool posts are added. While taking the saddle off the machine, look at and clean out any of the oil lube drillings etc of swarf etc. Check and deburr things that need it. Some edges should be left sharp to act as a scraper , where a chamfer or radius will allow junk to work it's way in between the surfaces. Cleaning out the factory swarf or grindings is the biggest advantage of stripping down the hobby end of machine tools.

Neil