Checking a lathe (runout, ways etc.)?

[sploo]

I'm considering moving to a "bigger" lathe (from my mini lathe), but given that'll be a higher cost I thought I should try to understand how I'd check that a lathe was in decent condition before purchasing.

I have a cheap Dial Test Indicator (0.01mm) so I put it against the outer registration area on the mini lathe spindle as shown below:

Rotating the spindle by hand or under power, the total swing on the dial (what I understand to be TIR) was just 0.01mm (about 4 ten thousandths of an inch). The same measurement for the internal taper was 0.02 (8 ten thousandths).

If I try to flex the spindle side to side with my hand I get about a third of one gradation on the dial, or 0.003mm (just over 1 ten thou).

Checking a hopefully pretty well ground milling bit shank in my three jaw chuck, I was reading a TIR of 0.05m (about 2 thou):

From a bit of searching it appears that for the mini lathe, spindle run out of under 1 thou, and 2-3 thou on a reasonable chuck is quite normal. So - the important question; have I done this test in the right way? I.e. if I were to do this again on another lathe am I going to be doing the right things to check the spindle bearings?

Also, how would I check wear on the ways? Maybe mount the indicator on the carriage and check the variation along the surface of the ways?

 

[TFrench]

Quick and dirty way I check ways is to try to wobble the carriage when it's near the chuck. That's where all the wear happens. Then take the tailstock off and move it right to that end. If it feels similar the ways should be ok, if it's too tight you know they've adjusted the gibs up to run well on the worn area.

 

[sploo]

Thanks.

I have my eye on a Colchester Chipmaster 5x20. Well, actually two - one looking pretty sorry for itself cosmetically, but obviously much cheaper. I quite enjoy restoring a "lost dog", but regrinding worn ways and replacing Gamet bearings is something out of my skill (or wallet) zone.

 

[Inspector]

Take another couple readings with the DTI. One on the face of the flange beside the registration boss you are checking and the other inside the bore. You can't really measure the bed wear by running the carriage back and forth as it is just going to follow the contour. The proper way is to mount a test bar the length of the bed between centres with the DTI touching the top and then side of the bar. Then it will show how much the carriage dips in the worn places. Plan B is to take the best straight edge you have and some feeler gauges. Put it on the working surfaces of the bed and see if there are gaps a 0.001/.025mm fit into. If bigger feeler blades fit the wear is greater. A light behind the straight edge will also show the gaps. If the wear is bad you can see it with your eye. The worn areas having a rougher surface. Put a rule between the centres in the tailstock and headstock. If perfect it will not be tilted in any direction. If tipped over from the top, either the head or tailstock is higher and if to a side them they are misaligned. Whether they can be adjusted to correct will depend on the machine or if it is because the bed is worn.

Pete

 

[TFrench]

In fairness a worn chipmaster is still going to be better than a mini lathe. Looking grotty is no guarantee of condition - my hardinge looked gross but it's not very worn.

 

[Fergie 307]

No one has mentioned one of the most important checks on a chipmaster. You need to make sure the speed variator works correctly. If this is damaged it will cost several hundred pounds to fix. The variator also requires special lubricant, very expensive and only available in twenty litre drums. You can probably find someone who owns one and has a drum of the stuff who will sell you the couple of litres you need. If you run it on the wrong oil it will be wrecked very rapidly, which is sadly all too often what happens to them. You need to see the machine running and run it up and down the speed range a few times to make sure it works correctly. Spindle run out on one of these shouldn't be measurable with your regular dti, it is to all intents and purposes zero, certainly not comparable to the horrendous figures for your mini lathe. To check accuracy of the machine the easiest way is to do a test cut. I use a 25 mm od piece of cds tube fitted with two 40mm acetal collars. One positioned about 5 inches from the end, the second 12 inches further along. Mount the tube in the chuck so the first collar is about an inch in front of the chuck. Then take a light cut across both with a very sharp hss tool. Measure the two collars and you will see if the thing cuts straight. on my 1961 Harrison the difference between the two collars is well under a thou. You can also check for bed wear by measuring with a micrometer between the upper and lower machined faces of the ways at the very end of the bed, where it is unlikely to be worn. Now compare with figures taken in the area in front of the chuck where the most wear is likely to occur. The chipmaster is a lovely machine but bear in mind it's only a 5x20, so still quite small capacity for the size of the machine. You will probably pay around £1000 for a basic machine in good order but cosmetically challenged, up to several times that for a minter with all the original steadies and other bits and pieces. Anything suspicious with the variator, noises, vibration etc walk away unless they are giving it away.

 

[RichardG]

I'm sure you're aware of the details of old lathes on lathes.co.uk but just in case.

Chipmaster & Harrison 10-AA lathe

It seems that early lathes didn't have hardened beds unless specified, later models were all hardened....definitely worth looking out for.

 

[deema]

This is a good source of the checks to do,

By the way 1 thou is 0.025mm

 

[sploo]

In fairness a worn chipmaster is still going to be better than a mini lathe. Looking grotty is no guarantee of condition - my hardinge looked gross but it's not very worn.

That's kinda what I'm hoping; given that it looks cosmetically rough but the owner seems quite happy that I want to clock it to check the bearings. I'm going to see it this weekend, so I guess if he knows it's a dog then he might have been evasive about me saying that I want to check it over with a DTI.

My only concern is that I am able to check it correctly, and not miss something due to inexperience. Buying a used mini lathe was obviously a low risk purchase due to the small cost and easy transportation!

 

[sploo]

No one has mentioned one of the most important checks on a chipmaster. You need to make sure the speed variator works correctly. If this is damaged it will cost several hundred pounds to fix. The variator also requires special lubricant, very expensive and only available in twenty litre drums. You can probably find someone who owns one and has a drum of the stuff who will sell you the couple of litres you need. If you run it on the wrong oil it will be wrecked very rapidly, which is sadly all too often what happens to them. You need to see the machine running and run it up and down the speed range a few times to make sure it works correctly. Spindle run out on one of these shouldn't be measurable with your regular dti, it is to all intents and purposes zero, certainly not comparable to the horrendous figures for your mini lathe. To check accuracy of the machine the easiest way is to do a test cut. I use a 25 mm od piece of cds tube fitted with two 40mm acetal collars. One positioned about 5 inches from the end, the second 12 inches further along. Mount the tube in the chuck so the first collar is about an inch in front of the chuck. Then take a light cut across both with a very sharp hss tool. Measure the two collars and you will see if the thing cuts straight. on my 1961 Harrison the difference between the two collars is well under a thou. You can also check for bed wear by measuring with a micrometer between the upper and lower machined faces of the ways at the very end of the bed, where it is unlikely to be worn. Now compare with figures taken in the area in front of the chuck where the most wear is likely to occur. The chipmaster is a lovely machine but bear in mind it's only a 5x20, so still quite small capacity for the size of the machine. You will probably pay around £1000 for a basic machine in good order but cosmetically challenged, up to several times that for a minter with all the original steadies and other bits and pieces. Anything suspicious with the variator, noises, vibration etc walk away unless they are giving it away.

Very useful info - thanks.

I can guarantee that there's nothing wrong with the variator; as there is no variator . It currently has a 3 phase motor control; though I don't know if it's running the original motor. That doesn't worry me particularly, as I get the gist that many people swap out the variator for a VFD anyway.

It's missing a few of the ball knobs (no bothered, can make new ones), and the rear splash guard (again, not too bothered). It's around £1300; and the cosmetically "nice" units I've seen (with the variator present) are all in the £3000-4500 range, so (given I'm not worried about the variator) I'm hoping it's a sensible price.

I understand the Chippie will do something closer to 5.5x20, so given that my mini lathe is 3.5x12 it'll be a big step up in capacity. Most important to me is the torque and rigidity required to take deeper cuts, and do parting; something the little mini lathe really struggles with.

With your acetal ring test, I assume you would not be supporting the end of the tube with the tailstock?

 

[sploo]

I'm sure you're aware of the details of old lathes on lathes.co.uk but just in case.

Chipmaster & Harrison 10-AA lathe

It seems that early lathes didn't have hardened beds unless specified, later models were all hardened....definitely worth looking out for.

The lathes.co.uk website is both very useful, and very frustrating (as often I just want tables of dimensions and model numbers). I see it mentions that "later" models were hardened, but as far as I can see there's no info as to when that happened. The one I'm looking at has a serial number that would put it mid/late 1969... so does that qualify as "later"? I have no idea.

Strangely, the very first image in the link above shows a "Late-model English gearbox Chipmaster"; but the tailstock is a rounded/curvy design. This model has a squared off tailstock with a flat top. I have a digital copy of the manual (stamped 1978) and the spare parts drawing contained within shows that same flat top tailstock (though other images in the manual show the curved version)

 

[Fergie 307]

Very useful info - thanks.

I can guarantee that there's nothing wrong with the variator; as there is no variator . It currently has a 3 phase motor control; though I don't know if it's running the original motor. That doesn't worry me particularly, as I get the gist that many people swap out the variator for a VFD anyway.

It's missing a few of the ball knobs (no bothered, can make new ones), and the rear splash guard (again, not too bothered). It's around £1300; and the cosmetically "nice" units I've seen (with the variator present) are all in the £3000-4500 range, so (given I'm not worried about the variator) I'm hoping it's a sensible price.

I understand the Chippie will do something closer to 5.5x20, so given that my mini lathe is 3.5x12 it'll be a big step up in capacity. Most important to me is the torque and rigidity required to take deeper cuts, and do parting; something the little mini lathe really struggles with.

With your acetal ring test, I assume you would not be supporting the end of the tube with the tailstock?

No. The whole point is that it should be unsupported. That's why I use the tube. It is fairly rigid and light enough not to suffer from droop. The point of the test is that it removes any inaccuracy of the chuck from the measurement. The acetal rings are easily cut so you don't get push away interfering with the result. What you are measuring is essentially the alignment of the spindle and bed. Inaccuracies in the chuck will not affect the result. If you mount you test piece between centres then any misalignment of the tailstock will come into play. The best way to test would be with a proper test bar mounted directly in the spindle taper, if you have or can borrow one. To check the slides I would wind each through its full travel, you are looking for an even turning force on the handwheel. If it's tight and either end of it's travel and looser in the middle that indicates wear. Same for the saddle, does it wind all the way up and down the Bed with an even resistance. As you can appreciate this is by no means an exhaustive list, but the measurements I have suggested should give you a pretty good idea. in practice most sellers are not going to stand for you spending several hours checking everything under the sun. And sorry but sticking a vfd on it is no substitute for a working variator. The variator is a form of cvt, so it alters the gearing of the machine, doesn't just make the motor go faster or slower. If the variator has been removed then you have lost one of the best features of the machine £1300 seems a lot to me for a machine with no variator and in less than great condition. I would suggest you would be better off with something like a Harrison 140 or Colchester student. If you need something a little smaller then a Colchester Bantam is a nice slightly smaller machine. All these are proper geared machines with a good range of speeds, power feeds and screwcutting capability. You should be able to get one in good working condition for between £1000 and £1500, more for one in really good condition and with all the steadies and other kit. Beware of those that have just had a coat of paint slapped on to smarten them up. There are many other good machines but the Colchester and Harrison ones have good availability of extra bits an pieces, and you can usually find spares fairly easily if you need them. The older versions, Harrison L5a for example also have hardened beds like the newer ones, the main difference is they are imperial rather than metric. You can cut both imperial or metric threads on either type, but more straightforward to cut metric threads on a metric machine and vice versa. All have their individual quirks and features I would have a good read of the articles on lathes.co.I'm for anything that you are thinking of.
And of course bear in mind that these machines weigh in at getting on for three quarters of a ton, they need to be solidly mounted on a thick concrete floor and properly set up if they are to give their best.

 

[Fergie 307]

The lathes.co.uk website is both very useful, and very frustrating (as often I just want tables of dimensions and model numbers). I see it mentions that "later" models were hardened, but as far as I can see there's no info as to when that happened. The one I'm looking at has a serial number that would put it mid/late 1969... so does that qualify as "later"? I have no idea.

Strangely, the very first image in the link above shows a "Late-model English gearbox Chipmaster"; but the tailstock is a rounded/curvy design. This model has a squared off tailstock with a flat top. I have a digital copy of the manual (stamped 1978) and the spare parts drawing contained within shows that same flat top tailstock (though other images in the manual show the curved version)

The Chippie was sold as a precision violation lathe, I know Harrison hardened all their beds as standard from about 1957 onwards

The lathes.co.uk website is both very useful, and very frustrating (as often I just want tables of dimensions and model numbers). I see it mentions that "later" models were hardened, but as far as I can see there's no info as to when that happened. The one I'm looking at has a serial number that would put it mid/late 1969... so does that qualify as "later"? I have no idea.

Strangely, the very first image in the link above shows a "Late-model English gearbox Chipmaster"; but the tailstock is a rounded/curvy design. This model has a squared off tailstock with a flat top. I have a digital copy of the manual (stamped 1978) and the spare parts drawing contained within shows that same flat top tailstock (though other images in the manual show the curved version)

I know Harrison hardened all their beds as standard from about 1957 onwards. The two companies amalgamated during the life of the Chipmaster so there were both Harrison and Colchester versions. I should think of its 1978 you can be quite safe in assuming it's hardened. Generally they both introduced squared designs in the late 60's and early 70's as they were thought to be more modern. So you get the Harrison 11inch, with a square headstock casting, but it is identical in every other respect to the earlier round head 5a. Even the parts inside the headstock are all exactly the same. And you thought fashion was just about clothes !

 

[Fergie 307]

Blooming auto correct got me again. Should of course read toolroom lathe, doh !

 

[sploo]

No. The whole point is that it should be unsupported. That's why I use the tube. It is fairly rigid and light enough not to suffer from droop. The point of the test is that it removes any inaccuracy of the chuck from the measurement. The acetal rings are easily cut so you don't get push away interfering with the result. What you are measuring is essentially the alignment of the spindle and bed. Inaccuracies in the chuck will not affect the result. If you mount you test piece between centres then any misalignment of the tailstock will come into play.

Got it - the use of a tube makes sense now. Thanks.

And sorry but sticking a vfd on it is no substitute for a working variator. The variator is a form of cvt, so it alters the gearing of the machine, doesn't just make the motor go faster or slower. If the variator has been removed then you have lost one of the best features of the machine £1300 seems a lot to me for a machine with no variator and in less than great condition.

As a childhood user of Lego I consider myself to be an expert on gearing and torque

Absolutely understood on the VFD vs variator torque issue. From what I've seen, people who pick up a Chippie tend to replace the variator (even if it's a good one). I'm told the variator likely takes a fair bit of power to drive, and many people find the lathe fitted with a 1.5 or 2hp motor (the former apparently being common for educational use). Installing a 3hp motor with a VFD seems like a reasonable substitute in that scenario, accepting that torque at the lowest speeds won't match the variator?

I would suggest you would be better off with something like a Harrison 140 or Colchester student. If you need something a little smaller then a Colchester Bantam is a nice slightly smaller machine. All these are proper geared machines with a good range of speeds, power feeds and screwcutting capability. You should be able to get one in good working condition for between £1000 and £1500, more for one in really good condition and with all the steadies and other kit.

I've considered the 140; though it seems to have a pretty low top speed (for small diameter work)? The student I think is a big bigger - probably too big for my garage. The Bantam looks good, and I was chatting to a chap about one. Oddly the listings I've found seem to nearly mirror the Chippie prices in like-for-like condition, so I assumed the Chippie would be the better lathe.

Beware of those that have just had a coat of paint slapped on to smarten them up.

Funny you mention that; I've just seen a listing of a slightly more modern lathe, and it looks as though someone's tried to tart it up by painting the whole thing with a brush; complete with paint drips on the cross slide (and a few other areas that should be bare metal)!

 

[Fergie 307]

A lot of 140s, and 5as for that matter, were sold to schools and colleges. These often have a 1.5hp motor and a top speed in the region of 750. This was because it was deemed a safer option. All 140s, and the vast majority of 5as have a spindle rated for up to 2000 rpm, so can easily be run much faster. Mine has a 2800 rpm 3hp 3 phase running through a vfd. I use the gears to change speeds, but have the vfd set up to provide two motor speeds, mimicking the two speed motor that was an option with the machine originally. This gives a total of sixteen gears with speeds from, in my case 30 to 1500 rpm. The problem using a vfd on a chippie is that without a gearbox you will have a much more limited range of speeds. The variator gives something like 30 to 3000 rpm, you will not get anything like that range from a vfd controlled motor, not with any torque anyway. And I think you mentioned wanting to take bigger cuts, which is exactly where you want lots of torque at low speed. That's why I think you might be better off with a conventional geared machine. Personally I think if you buy one without a chip/splash guard, you will quickly find yourself looking for one. I really does help stop swarf flying everywhere. Price as ever is a lot to do with popularity. The Bantam is one of the most popular lathes of that size, so they fetch good money. The chipmaster is a better machine but no so popular, and a lot of people are a bit scared of potential variator problems.

 

[sploo]

As far as I understand, the Chipmaster has two "speeds"; in the sense that the variator has a roughly 9:1 range, with the low gear range (35-300rpm) powering the spindle via gears, and the high range (320-3000rpm) being belt driven.

I'm told (but haven't confirmed) that 6 pole induction motor can be run from around 30-200% via a VFD (roughly a 6:1 range).

3000rpm max seems high (even my mini lathe only hits 2500rpm max); so if I used a pulley that put 200% on a VFD at 2500rpm (in high range), that should give approx 400-2500rpm in high and 40-250rpm in low.

The question I guess is whether the torque of a 3hp motor would be inadequate at 30% frequency on a VFD; which I accept might be the case.

 

[Fergie 307]

It seems to me that £1300 is a lot for a scruffy one with no variator and no splash back. If it turns out to be in good condition mechanically, and you are prepared to accept the compromise in using it with a vfd, then go for it. All depends on what you want it for, but I would definitely want to get that price down to nearer £1000 though. I would certainly encourage you to have a look at a barman or 140 before making a final decision. I had always wanted a Chipmaster, but in the end decided against it mainly because of its small capacity, and because the 5a I have came up and was too good to miss out on.
As you say any of these machines is going to be a world away from your mini lathe. I have completely rebuilt mine, but actually had to do very little to it other than giving everything a really good clean, and removing all the grease that had been injected into what are actually oiling points, a very common issue. it's had a fresh cost of paint but all it needed in the way of repairs were replacement clutch pins, a new pulley bearing and belts and the saddle strips regrinding. As it happened I bought it just before the pandemic, and it turned into a bit of a lockdown project. Need to lose the nasty modern stop switch, but I have the original plate and buttons so on my to do list to make up when I have time.

 

[sploo]

That looks great. There is a Harrison 140 also available locally. Looks cosmetically good from the photos, but it is £2000. As for the Chippie; certainly I'd want to be talking the guy down to (or under) the £1000 mark.

For the capacities though; aren't the Chipmaster 5x20 and the Harrison 140 similar? The latter has a 140mm swing, and the Chipmaster 5x20 is 143mm. The Chippie is 508mm between centres. The Harrison is bigger in that regard at 610mm?

 

[Fergie 307]

That looks great. There is a Harrison 140 also available locally. Looks cosmetically good from the photos, but it is £2000. As for the Chippie; certainly I'd want to be talking the guy down to (or under) the £1000 mark.

For the capacities though; aren't the Chipmaster 5x20 and the Harrison 140 similar? The latter has a 140mm swing, and the Chipmaster 5x20 is 143mm. The Chippie is 508mm between centres. The Harrison is bigger in that regard at 610mm?

Thanks. The 140 is essentially a metric version of the 11inch square head, which in turn is just a square head version of the 5a round head. Mechanically they are pretty much identical, and most parts other than those specifically linked to the metric or imperial functions are interchangeable. I think the 140 fetches more primarily because people seem to prefer a metric machine, and they are newer, so may be in better condition. Whether £2000 is fair really depends on the condition and what it comes with. At that price I would expect it to be in good shape, and have all the original kit. So three and four jaw chucks, faceplate, catch plate and fixed and travelling steadies, and the spindle nose to Morse taper adapter. As a general rule you will find that a 5a in similar condition will be significantly cheaper, so again depends on how big an issue it is whether it's metric or imperial. Many 5a machines are hybrids, so they have metric dials, but are actually imperial machines. Mine is configured this way.
A big advantage with the Harrison is it is a gap bed, so with the gap removed it can accommodate much bigger diameters up to about 4 inches or so thick. I don't think they made a gap bed version of the Chipmaster. Harrison also tend to under quote the swing of their machines. If you look on lathes.co it will tell you the actual capacity. I would nip and measure mine but I'm not at home. Incidentally the Chipmaster is the same, nominally 5 inch, but actually 5 3/4 or thereabouts. So the swings of both are similar. The extra length of the bed and the gap swung it for me, no pun intended, as I find both very useful, but this may not matter to you. one major nuisance with a short bed is that the tailstock can get in the way when you aren't using it. Not a massive issue to just slide it off, but worth bearing in mind that you allow enough room around the machine to allow for this, and to open the doors for the changewheel etc. Another thing to consider is the pass through diameter of the spindle. This is a few mm larger on the Chipmaster if I remember correctly. So swings and roundabouts every machine has its particular pros and cons. All depends on which is best suited to your needs.