Member postings for Ajohnw

LOL I'm glad you found something that illustrates what I mentioned Neil cause often in the few cases I have mentioned it I know I am pissing into the wind. There are always comments about mine doesn't jam etc. Actually some rock helps after a fashion as the tool on some lathes pulls away from the work when the saddle is wound back masking initial bearing wear problems.

Myford's narrow guide is better than many actually but has the wear problem. It has a huge area to take downward forces but not so good for any sideways ones. I phoned them once about buying new S7 spindle. Turns out that they had never supplied one but they did make some later. The conversation moved on to wear and they couldn't understand how it was happening because they had 30 odd year old machines used regularly that were still fine - the reason is simple really maintenance of the right type when it's needed. That has to include adjustment. I needed a new S7 spindle because some twink had used it for a long time and never adjusted it, probably didn't make sure the oiling was working correctly either. Trying to scape the cone back in to a badly worn spindle would be a waste of time. Actually I'd guess this area is why people have a lot of trouble adjusting them. The S7 is an amazing bit of kit when everything is as it should be. ML7's too but the bearings on those do need attention from time to time and I have often see them with no shims left under the bearing caps.

Personally for all sorts of reasons I feel a wear strip and the front rail narrow guide is the best option but if people do this and also reshim the saddle and sort out the gib strips they probably will find some work is needed on the rails as well. I suspect I have read that Tubal Cain converted a wide guide back to narrow if so he must have been an idiot just like me too.

John

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Some people book mark threads - even people who post to save them repeating themselves. Unusually on this forum people do seem to search it. Hard thing to balance because it could be that all questions are answered some where so there is no need for any one to post at all.

Lubrication is a fundamental aspect of lathes not just bearings. There is no harm in discussing how it applies to other areas - it's more information. Why not just read the first few words and skip it if it's of no interest.

John

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Oil technology took the motor industry by surprise Neil but it didn't take them long to take advantage of it and get wear rates back where they want them to be.

Noticing comments about lubrication other than bearings and seeing mention of greasy substances I would say don't. It's much better at catching bits of swarf than a thin coat of oil. I have just bought a used Wabeco mini and it has grease all over the lead screw. I'm not looking forwards to cleaning it all off and off the rack too. It also has a grease nipple for the front bearing to pump a bit in every 500 hrs - not that unusual. So much for only adding a bit as it will fill up, It also has grease on the tumbler reverse and as usual the end of the spindle is inside the end cover. I suppose that bits will miss these and as the rest uses belts it doesn't matter. When the lathe is started up initially there is a tinkling type sound that goes away in seconds. Not fully sorted but initially seems to be down to the tumbler gear arrangement settling down. I suspect the mesh may be out. I've seen mention of using photo copy paper to set the mesh. I mentioned this elsewhere as I thought some on might chime in. They did. The theoretical clearance on Boxford gears is around 0.0015" not photocopy paper thickness. Maybe the extra thickness allows passage for swarf.

The lead screw is so well out from the edge of the bed that it's bound to catch swarf. Doh - I suppose it has to be as if the bed was any wider the bed guide might not work correctly. I have looked around for spring covers - none found for straight forward mail order so far. Only phone for a quote. Arc did something once but I didn't like the way they worked.

John

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Tuctite in the UK

**LINK**

It might be worth asking these people what it would cost to regrind it and fit some sort of wear strip. This is the sort of thing you could do yourself with a miller but it will need very careful setting up. I'd just look at adding pads at each end and would probably have to finally fit by hand.

There are several things that can improve these machines when worn. One of the gib strips that hooks under the rails can be turned over. The other has to be reground or a new one fitted. These can then be shimmed for min clearance. Feeler gauges can speed that up but the thickness derived from that may need more adjustment. The trouble is that there is likely to be wear on the underside of the rails / top as well. Best check with a mic first as even few 0.0001"'s matter. Same with the fit of the part you have noticed is worn. People have lapped this sort of thing away in all cases including the cross slide which has similar problems on all lathes, Ordinary gib strips are probably best replaced but regrinding can remove wear. They may finish up bent slightly but this will cure over time if the adjustments are checked now and again.

When I retired some one who regularly gets enquires concerning sorting myfords out suggested I should do that for a "living". The problem as I see it is that once wear has caused significant problems it would be possible to improve things a little for people purely via adjustments but that would only improve not fix it. Past that I feel it would be hard to compete with what myford offered especially in terms of a bed regrind and saddle refit and grind. There would be no chance of matching that doing it by hand. I decided to be short of money and happy rather than going around pissing people off. Suppose I am too honest.

A note cause people don't seem to appreciate this for some reason and it is why this type and dovetails wear.

There has to be some rock on this style of bed because there must be clearance for the saddle to move. It should tend to be on the leading edge on the front as cutting pressures will force that corner against the rail and the opposite on the inner guide - but in real terms there can be wear at both ends. A good quality parallel might show a flat bit in the middle to use as a reference. If scraped the thickness of blue that needs to be used for the accuracy needed is so thin it's not that easy to see. Personally I would use files and maybe a diamond lap. Rifflers are likely to be handy - good sharp ones. Myford hardened beds really are. Diamond laps and honing oil might be the best option if the thickness of the rails via the underside needs changing in places.

The best answer really is to keep them well adjusted and not wait until problems start to show. That way the oil film has a chance of doing it's job.

John

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I'm sure I put moly in a shogun gearbox without any problems other than a 3ft lever to undo the filler plug. It was a one shot gearbox treatment.

John

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J&S also do some with the usual end but with most of the shank thinned down - they are a bit rare. I've seen them oil blacked rather than the usual shiny ones.

John

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Edited By John W1 on 18/09/2015 19:42:22

I suppose it sort of puts the costs of answering questions on the people who ask maybe saving a subscription price increase and giving a call centre type job to some one.

Personally I never ever phone a line like this as my phone calls are free no matter how many I make so they mess up my bill and I don't get the cost of a standard phone call deducted.

What's next - 3 very easily answered questions to win a prize worth £10, phone calls may last 10 min and cost 10p a min. Companies that do this make a fortune even with prizes worth thousands. Just a thought for you Neil. You could do a win a mini lathe one on the TV.

John

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Edited By John W1 on 18/09/2015 18:02:37

I think one of the things about moly is that there is moly grease and there is moly grease. There is a type that is used on articulated lorry 5th wheel - that's the one the whole trailer hinges on with many tonnes on it. It's very thick high pressure stuff. People sometime think this is what moly grease is always like.

Arc sell some high speed moly grease - I think - my tin is yet to surface. They now have a gp one so mine might be too. I bought it some time ago. These are nothing like 5th wheel grease.

The motor industry don't like it at all or when it's used as an oil additive. They don't like people changing the engine oil too often either. Both can extend life far more than they are happy with. One problem that can occur when it's used in engines is that it can prevent initial running in. There are also claims that it can poison sensors. This was long before this aspect was as complicated as it is now. In fact there weren't any sensors in the exhaust or the engine oil in most cases. Ford on the other hand bring out the black stuff and start using it if they have problems with bearing type things not lasting through warranty.

I'm a firm believer. I once drove a car with a hole in a piston that blew all of the oil out of the exhaust for 20 miles keeping the revs up so that something showed on the oil pressure gauge - air. The AA emptied the oil out of a mini and drove it to London and back. All they found when they dismantled it was slight signs of over heating. Both had been treated with it for some time - not the same as just pouring it in. I've used it on every wheel bearing on all of the cars I have had when I did that sort of thing myself. Caravans too. Some people seem to think it has a molecular effect between the boundaries of rotating parts. I'd guess this is why the bearing people argue about it but they in real terms may be exactly the same as the automotive companies. I obtained my tin of a castrol MS3 equivalent rather early on from an uncle who was an aircraft fitter. Now I just have the car serviced. It might cause grief on modern sensors. In fact I'm pretty sure motor manufacturers would make sure it does if they could.

My boxford has been running on it since I had it. Initially I pocked out all of the grease I could and then put some moly in it. Now it's all moly. These are taper rollers. It has a 3 morse spindle. I gauge the running temperature inside the spindle right under the rear bearing to be around 40C once the lathe has warmed up. Sort of nice and cozy warm not hot. If it was around 60C I could probably keep my finger there but it would be rather uncomfortable. I've used the same test at work on electronics before getting a contact thermocouple out. It's not an exact science.

I've no idea how this will work out on other lathes. Some aspects of headstock design are probably a bit of a black art - eg what bearing heating effects do to any preload that might be there. There isn't any preload at the front on some designs and these do show improvements when they warm up. Boxford bearings tighten up a touch.

John

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I assume this one was a kit at some point. It's a sine bar swivelling on the axis of the bearing on the left - which needn't be a bearing really.

The part that links this to the top part that fits on the cross slide is simply fork shaped and has a decent guide length along the bar to minimise rock. This part fixes to the holes and machined area myford provide on the back of the bed.

It's covered in oxidised oil in places.

Some one might be able to knock something up like this by basing it around a parallel strip but the fork is ground as well on this one.

John

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Don't expect the straight shank er collet holders to be on size. Every one I have looked at is undersized - enough to mean there isn't any chance of using it with a standard bearing size. I've been interested in spindles for a long time.

John

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I wouldn't even suggest Brian adjusts them.

I suspect I am going to have the problem soon. Manual states check bearing heat every 500 hrs. Adjustment states remove free play still allowing the spindle to turn easily by hand plus an over tightening warning. Pity there isn't any info on the heat aspect. My understanding is that there are 2 methods of specify bearing setting. One is dimensionally - a lathe that doesn't have any adjustment and via torque required to turn. Even too much grease can mess that one up. The wrong grease too.

It also states something which I feel people neglect - as soon as any slides show signs of wear - loosening in other word adjust ASAP. Same for the bearings. It is a fact that these all wear more slowly if the adjustments are kept correct. Nearly every small lathe I come across has the cross slide set too loose. The bearings on my Boxford were way too loose when I bought it. I doubt if they had ever been adjusted from new.

John

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Edited By John W1 on 18/09/2015 00:17:09

The problem with screw cutting via cnc is the need to control the motor speed pretty precisely as loads vary. It needs servo motor type set ups really.

The Taigs make good use of some sort of concrete in the bed. Peatol reckoned it was a sort of slurry that is backed down into an aluminium extrusion with the metal part of the bed on top.

John

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The main reason the saddle wears so quickly is that the contact length on the rear of the front rail is rather small and things will twist a bit in use. The inner one can't be as long as the outers as these need to go past the tail stock to give a usable machine.

If they didn't do this the lathe would have the same "problem" as ML10's etc a rather narrow saddle compared with the width of the bed. That means for the same clearance needed for reasonably easy movement causes more rock than a lathe with a longer guide. The clearances have to be very low but the saddle will tend to twist / move under load. This is often a problem on lathes that use a dovetail on the bed and they can wear quickly as well.

This is an area where prismatic beds score heavily over others although the best arrangement isn't always used. The outer prisms ( ^ 's) can run all along the bed. The head and tail stocks sit on another prism which also aligns the head. 2 are used for this on larger high end machines as the tailstock gains the same advantage mentioned for the saddle shortly - cutting forces tighten the fit on the guide. This way the outer guides on the saddle can pass both the headstock and the tailstock and cutting forces are applied within the length of the guides. Some machines fall short of this ideal as the guides can't pass the head so cutting forces are applied right at the end of the guide. The other advantage of this type of set up is that the weight of the saddle causes it to sit firmly on the guides, no clearance at all - cutting forces just increase the pressure there. It's also easy to get relatively large bearings surfaces.

John

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Ball races can be preloaded but they then run as angular contact - one well regarded small lathe the unimat has done this for donkeys years. Not a problem providing that they are good bearings. Angular contact may offer a bigger contact angle than a deep groove ball bearing has. Some more compact angular contact bearings have rather low contact angles. It's probably possible to compare ball and angular by measuring diameters - the less distance between inner and outer the greater the contact angle.

Boxford have an interesting way of setting preload. Wrap rope/string round a face plate and pull string with a spring balance and note the weight it reads. Some find it works others don't. This seems to be down to bearing wear. They always wear oval eventually which seems to mess the setting up and more preload is needed to prevent spindle deflection. It didn't work for me so I used heating. Bearings heat up in use and as the heat is taken away more easily from the outer than the inner they also tighten. What I did was adjust and run the lathe for around 15mins and then checked the bearing temperature on the rear by sticking my finger in the end of the spindle - lathe off of course. I did this because I happen to know that lathe bearings often run at over 100C so expect to feel some real warmth. I did this at medium speed - around 600rpm on a Boxford and then flat out, 1300rpm as a check. Not much difference. Set like this I can see that the finish with very light cuts improves when the lathe has warmed up but due to that it's also more likely to show very shallow problems that are down to vibrations on the machine.

I can't relate either of these to small ball bearings as the Boxford uses much larger taper rollers but it might give people some idea of how they might set them. The problem with setting preloads on bearings is that if it's too high they wont last long at all. None of these types of lathes even from other manufacturers seem to give any info on setting them. - Not the ones I have seen anyway.

John

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Edited By John W1 on 17/09/2015 20:05:40

Things these day will seem to measure 1 micron Muzzer. I have a dti for instance that will. Trouble is that at best even at this level it's really digital and probably the limit of resolution so in real terms is +/-1 digit and then there is the tolerance on the scales themselves when measurements are made with digital mic's and digital readouts which are very likely to be worse, getting even worse as the length goes up. Often that tolerance isn't even given.

Lastly lathes are not micron devices, most of the metal turned on them isn't either.

As well as mentioning how accurately a chuck hold I should have asked how straight does he think the bar is. Even on ground stuff a tolerance of 0.001in per foot is by no means unusual.

The best way to check a lathe is via turning and even then actually measuring all aspecta to 1 micron is beyond the ability of most people really. Even a digital mic in really terms is only a comparator at this level if used very carefully.

John

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Edited By John W1 on 17/09/2015 09:30:52

Some might need explanation of why begs the question is interesting. Thankfully the wiki has been updated

**LINK**

It did refer to some Gaelic person that probably couldn't speak English properly who a long time ago said that the phrase was circular

John

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The oxford dictionary doesn't take anything like that length of time to update Neil. The real source for Collin's too but more concise. Both probably give all meanings of both words which will have wider scope than the things under discussion anyway. This begs the question should dictionaries ever be updated. I'd beg to differ.

John

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Ditto except my callipers that I use for quick and dirty measurements are mitutoyo absolutes. I use mic's for anything that matters because they are far more reliable in terms of accuracy.

For measuring bores with callipers the old style that wouldn't measure below a certain size where the internal jaw width had to be subtracted from the reading are much more reliable than thin edges but are sadly not available on run of the mill ones because they aren't really intended for taking very precise readings - especially that way.

John

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Edited By John W1 on 16/09/2015 23:26:53

Just how accurately do you expect a chuck to run?

John

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There is something decidedly odd going on Jeff. I almost feel like saying stinking fish. Most things have been covered. There is only one other that I can think of. Brians adjustment of the saddle so that it does rock !!! Rather hard to imagine what some on might do to achieve the results he has had.

I can't really imagine how some on can have this much trouble using a lathe as I used one for the first time at the age of 11 at school. Did I receive any instruction - yes a bit, on things like this is how you turn it on. Teach watched from a distance for a while and noticed that I tightened up the belt drive and he loosened it again after class - he was very keen on keeping the bearings in good order - me I wanted to take a bigger cuts. It seems I was the only person that did that. It was the first time I had even seen a belt drive but it was obvious why the chuck stopped turning even though I couldn't see the belt - I had to look under the guards and behind the machine. Perhaps it's my parental black country genomes. No one round here could survive without them so natural selection rules etc.

John

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