New Lathe leveling

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For the convenience of anyone who wants to try using "Optical Levers"

Near enough for practical work:

1 second of arc is subtended by 1mm at 206265mm

... and, expressed that way, there is a simple linear relationship.

MichaelG.

If you can arrange to do so safely it would be prudent to have a look at the underside of the headstock and tail end support castings to see how much contact between lathe and support the maker expects. Generally there will be a small boss around the bolting holes sitting proud of the main casting base which actually contacts the support or bench. Boss diameter of the order of 3 times bolt hole diameter projecting around 1/16", 2 mm or a bit more seems typical judging by the small machines I have seen. It seems that this area is rarely well finished, for example SouthBend 9" machines seem to be left as (nicely) cast, so it may be unwise to assume that the machine will sit with all feet in proper contact on a flat surface. Inspector Meticulous types may suggest that it would be advantageous to set the lathe on a flat surface on large steel washers coated with bodyfiller and allowing to harden before bolting to create a smooth true surface under each foot but this is probably OTT unless the foot surface is unreasonably poor.

In my view all small lathes are made to sit much too close to the bench. Spacing up by 3 inches or so gives room for a proper pull out chip tray and provides space to wield a brush whilst sweeping out the bits that miss the tray. Makes life so much more civilised. My first such tray was the cover off a broken record deck. If you do decide to space it up make proper levelling spacers with adjustment threads. Simple and quick to do, well worth the effort to make the installation job easy.

Odds are that the bench that a small lathe is bolted to will be stiffer than the lathe itself. Not the best of situations if the bench is a live material, such as wood, sitting on a fairly basic floor such as those commonly used with the more affordable variety of shed. The better quality thick chipboard kitchen worktop or, preferably, industrial rated counterparts make a nice dead, thermally stable, bench surface on which to stand a lathe. The finish seems oil proof over a more than a decade too. One of my Southbend 9" lathes sat very happily for over 15 years on such a worktop lightly mounted to a pair of plastic workshop cupboards. At B&Q special clearance offer prices the plastic cupboards seemed worth a try but I did add some judicous stiffening by driving nicely fitted timbers down the hollow molded sections and strutting under the shelves before bolting them in place.

Clive

Thanks for all your suggestions, especially Thor's.

Terry.

One thing that you need to pay attention to is that the bench top is most likely not as flat as the underside of the lathe.

So before tightening down ANY of the mounting bolts, stick a feeler gauge under all the mounting points and add appropriate shims if needed. Otherwise, when you tigthten down the the bolts, it could pull the bed out of true.

To keep everything true, the best set up is a steel bench bolted to a concrete floor, so the bench does not change shape as wooden benches can do, or as steel benches can if set on uneven flooring etc.

This is standard procedure for any machinery in industry, be it lathes, pumps, electric motors, power station turbines or bottling machines etc etc.

Laser pen + mirror + wall + bit of DIY will do it .

Regards ,

Michael Williams .

Hi Michael,

I like your idea and I can see this working for one fixed position, but if you wanted to compare the level at both ends of a lathe bed, how would you realign the mirror to be able to accurately compare the results?

Doug

One of the best ways of mounting a small lathe on a wooden bench is to acquire a thick concrete paving slab and bed this on to the top of the bench with flexible mastic, then bolt the lathe to the concrete.

You could even cast your own concrete slab or use a suitable lump of granite, perhaps an offcut from a tombstone maker ( or would that be a bit morbid ! )

Doug

There was a design for an Autocollimator in MEW

... Issues 73, 75, 76

MichaelG.

Recommended reading

See especially Chapter 2

MichaelG.

All this talk on lathe beds has me thinking. I wonder if the present day lathe beds can match the quality of the beds of old. One of my old Atlas brochures that was printed circa 1930 states that the Atlas lathe ways were machined to within 15 thou of final dimension. They were then stored for 3-6 months, depending on the model, in order to allow them to season (adjust to the machining stresses). After their lengthy nap, they were machined to their final dimension. I have read that South Bend did likewise during their US manufacturing years. I have an elderly uncle (97) who was a gunsmith for over 60 years. Anytime he turned a rifle barrel, he would season it in my aunts electric oven for one hour at 450 Deg F. After it cooled he would make the final 3-5 thou pass(es). His rifles shot extremely well and were in high demand all over North .America. There are obviously advantages to seasoning machined steel and iron.

I just used a test bar and a dti in the tool post, simples.

I have just seen this about lathe levelling, I have used Auto Collimation for checking the flatness of engine beds in a ship. I used a Wild Heerbrug Auto Collimator that is preset to the Titanium mirror on a surface plate and then transferred to the bed ways. It only measures undulations in bed surface every 300mm! NOT bed level in relation to other planes. On a lathe bed it would be difficult to measure twist as the area is small, whereas on an engine bed which might be 2M wide it is significant. In one instance I was able to determine that an engine bed had been damaged by a con rod becoming detached and bending the crankshaft and also the bed to buckle. Lloyds Maritime insurance paid up for a new bed and crankshaft from my evidence. (There is an interesting story behind this if anyones interested) Further to the lathe levelling, carrying out a level to the Nth degree is pointless as long as there is no twist and the lathe cuts without deviation I would not worry a bit. Super levelling will not make any superior work. As long as the lathe cuts parallel which is usually tailstock setting all will be well.An Engineers level of 10sec. accuracy will be all that is needed to check the bed. I decry the over enthusiastic tightening of bolts on the bed and excessive shimming to correct errors that only will then transfer somewhere else along the bed. I used to use a Colchester Comet lathe in the back of a lorry transverse across the chassis and never had any problems with accuracy.

Clive

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Yes please, Clive

... May be better to start a new thread though [?]

MichaelG.

The company in Taiwan that made my BH 1324 lathe in 1986 seasoned all their lathe beds for 18 months. As well as their own make of lathe, they made the beds for a similar size Colchester lathe. Ian S C

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Well said, Clive

... however [for the benefit of any newcomers] I think it worth pointing out:

A traditional Engineers Level, with a resolution of 10sec. per division and an "analog display" is a much more sensitive test instrument than the modern "Digital Angle Gauge" with its [typical] 0.1deg. resolution.

Horses for Courses !!

MichaelG.

John Hewes,

I've sent you a PM

Regards

Brian

Even the crude 1" long tube on top of my digital level appears to be several times as sensitive as the digital bit.

Neil

Neil - is that the CPC Duratool level referenced elsewhere? Is it any good (where "good" is undefined )?

Hi Martin,
My 2 digital levels arrived today and seem to work as well as the more expensive Wixey one I bought a couple of years ago. They also have the spirit level on top and a hold button which was not on the Wixey version. I have just had a look at the pictures I took of the Wixey version when I opened the case and there is a place on the PCB for a hold button. This makes me suspect that that the two versions are identical.

Les.