What are members thoughts on Gap Bed lathes ?

Looking to purchase a new lathe ,possibly Chester Craftsman or Warco 290.

I will have a look at the show but obviously I wont be able to see warco. Just wondered on thoughts on ridgidity etc.

Thanks

Bob

I don’t see a problem with a well designed gap bed lathe, a gap with a removable piece of bed means the gap can be bigger without the saddle overhanging the gap when not in use. Very handy for flywheels and wheels and save having a very large lathe.

Mike

I don't see a problem with a gap bed. For hobby use you're probably not going to be pushing it hard enough for the gap to make a difference. From a rigidity perspective, I would have thought that the bed with or without the gap piece would be much more rigid than the tool fixing, toolholder fixing, topslide and probably the saddle gibs too.

Whether you'll ever need the gap is another question that only you can answer Maybe, like a lot of tools that I have, great for one job every few years.

Rob

I have a Chester Craftsman gap bed lathe and have no problem with it.

I seem to remember removing the gap piece once, many moons ago to do some job.

I don't think I have ever removed it since, never had the need to, but it is useful to have and it cost nothing extra.

So, I would say, go for it, better to be looking at it than looking for it !

The Craftsman is a good all-round machine, not tool-room, but can still handle fair sized work

I think the Warco machine is very similar.

Six of one and half a dozen of the other. The advantage of a gap lathe is it's ability to turn larger diameter objects than might be expected of a machine of that size. But there's no such thing as a free lunch! Gaps have their disadvantages: the expected work-handling benefit will be less than the gap implies, for example tool-post travel may not be enough to fully exploit the extra space; the strength of the bed and the lathe's rigidity are reduced; and - if the gap has a plug - it's precision part to be kept clean, protected from damage, and carefully fitted. However, the disadvantages don't seem to matter much in a general-purpose workshop.

I wouldn't buy a gap-bed lathe unless the feature was going to be useful. They're not for me. But a jolly good idea for anyone who only has space for a moderately sized lathe and has a regular sprinkling of wheels and flywheels to make. Traction engines come to mind.

Dave

My Engineers ToolRoom BL12 - 24 is a lookalike of the Chester Craftsman (and the late Warco BH600 )

In the 16 years of ownership, have never needed to remove the gap. But have never had any concerns about rigidity when taking cuts of upto 0.150" deep, or with smaller intermittent cuts. The motor is a 1.5 hp, 3 phase , powered by a VFD.

The Craftsman is a heavy machine, weighing 390 Kg,

I have used it with a Vertical Slide, to flycut the ends of 3" x 1" steel bar, without problems.

When I had a Myford ML7, I did need to use the gap facility of from time to time, but found it not to be quite rigid enough for my needs, especially when using a Rodney milling attachment.

The BL12-24 bolts down using six 1/2" or 12mm fixings, where the ML7 uses four 5/16 or 8mm.

My lathe actually sits on six 1/2 UNF setscrews, with a nut above and below each lathe foot, which are secured to angle irons resting on the beams of ex warehouse staging, rather than the cabinet which comes with the lathe.

The ML7 was bolted to the steel bench.

Hence, I consider it to be much more rigid than the ML7.

In this case there should be no concerns over the bed flexing.

The gap is a useful feature, should you ever need to swing anything larger than 12", or 300mm.

Someone checked his BH600 before and after, having removed and refitted the gap piece. No misalignment was reported in the "refitted" condition, so the alignment seems to give no problems.

The Craftsman should be a versatile machine, given the Norton gearbox and PCF..

Howard

I'd go substantially with SOD's advice. But I would comment that in the years I spent on various shop floors, where gap fillers had been removed, they'd *usually* not been refitted precisely, often resulting in the crossslide needing to be tapped in a couple of thou as the carriage climbed onto the gap filler.

But you get used to anything - after a few days you just do it by instinct without really registering it.

Often very handy on my old Super 7 - where I can swing things that wouldn't fit otherwise, including a large 4-jaw (too big really but used often) as well as a big faceplate (also very useful). There are limits to this (as Dave observes) and care is required when setting up to make sure you don't clip the bed.

With regards to rigidity, I've never noticed a problem with that but I'm a "hobbyist" and don't knowingly abuse my machines - most of which are nearly as old as me and need to be treated gently (like me).

So I'd vote in favour of the extra flexibility a 'gap' provides as I haven't noticed any downsides...

Regards,

IanT

I wouldn't buy a main lathe that wasn't gap bed. But neither would I buy one that simply had a gap; it has to be a removable gap piece for me. On a well designed lathe a gap shouldn't materially affect the rigidity. One of the problems on lathes with a permanent gap is that in order to allow the saddle to be near the chuck for ordinary turning the width in the gap for the workpiece once a faceplate is fitted can be minimal.

Another point to note is that some of the import lathes with gap pieces do not gaurantee the turning accuracy of the lathe once the gap has been removed and refitted.

I am building a traction engine, so the gap bed does come in useful:

But it also comes in handy for smaller parts that need involved setups, meaning that the diddy faceplate cannot be used:

Andrew

And if a gap bed lathe is chosen, ensure it has a low enough speed. A geared head might be better due to the torque amplification, but I have no experience of variable speed drives (apart from my c300 minilathe).

Bill

I have a 14" x 40" gap bed lathe and have only needed to take the gap filler out once. Biggest downside for me is the modern lathe having the spiral spring lead screw cover which seriously hinders getting close enough to the face plate without excessive tool overhang.

Gaps never hindered the popularity of Myford S7 lathes...

Neil

.

Nor stopped people doing things like this to them: **LINK**

https://www.ebay.co.uk/itm/Myford-ML7-Capstan-lathe-240-volts/233317051295

MichaelG.

What would you do when a job comes along that would be too big for a non gap machine? Some posters have said they use the gap very rarely but unless you have access to a club workshop with larger machines or a friends machine then you may have to pay a machine shop to do the job, they can be very helpful and do it for a donation to the tea swindle or eye wateringly expensive. I don’t believe the gap has a real downside so why not have one? It could be very useful.

Mike

That seems an abuse of a nice machine, Neil.

Mike, some people have made raising blocks for the headtock and toolpost, which would be easier on a flatbed lathe than one with vees.

Here's an example on a small lathe:

Example of raising blocks

Bill

I see the gap as an asset even if used once in a blue moon.

I would not worry about the bed's rigidity on a properly-made lathe, as the bed will have been designed to cope with the gap both with and without the filler. If removing and refitting the filler compromises the bed's overall accuracy, as Andrew has observed, that seems to me a poorly-designed machine!

If the removed filler is held by screws tapped vertically in the bed (as on my Harrison L5), plug the holes with short screws, as swarf likes burrows.

Mick B1:

You remind me I should examine my L5's gap-filler L5. It does put a tiny step in the V-way, but that might not be the filler's fault. It is made to be easy to remove and replace, being located by two stubby dowels and held by two set-screws, albeit a bit awkward to reach. The mating faces still show their planing-marks, and no damage, so I think bed wear close to the chuck the more likely reason for the step.

The faceplate on that machine will just clear the V on the filler, I think.

I wouldn't be without the gap in the bed on either my Myford ML7 or the old Drummond M-type. Invaluable when you need it and no disadvantage at all when you don't. I do quite a bit of faceplate work in lieu of milling and you need the gap to fit the faceplate, even if the job is not that large. Or often the job must be mounted off-centre and swings down into the gap for part of its revolution.

But a lot of the Chinese lathes have a larger swing over the bed in proportion to the rest of their size, so no need for a gap bed. If you can swing 10" diameter over the bed, no need for a gap. Myford will only swing 7" diameter over the bed, hence need for gap to swing a 10" faceplate or thereabouts.

The thread seems to be concentrating on gap beds (per the thread title). The poster was initially also expecting comparison between the chester gap bed lathe at £2.5k and the Warco 290V at £3.3k. No option of a non-variable speed Warco offering and not a gap bed lathe.

My thoughts are that the gap bed will be at a premium, so I would expect the quality/functionality of that lathe is less. That given, the gap bed lathe does appear to weigh in at about 150kg more (does the 230kg include the mass of the stand would be one enquiry). With different bed lengths, that increase is quite considerable - but they have chopped out 75mm extra at the gap end.

I would remember that most gap bed lathes were relatively old iron and very robust. Not so sure about chinese offerings at the ‘hobby’ end of the market.

Might be worth watching the Keith Fenner series of videos on his more recent gap bed lathe (rather larger than most hobby lathes, possibly?) rebuild.

Two different lathes by a long way, so not very comparable, I would have thought. Buyer’s choice entirely. If I were expecting £3.3k quality/functionality I would be checking out both lathes in the flesh, for sure, before making my decision. If not so concerned about the quality/otherwise functionality, and needed the extra swing, then the craftsman is the only option?

It's an interesting question that I think could only be answered by testing.

Old-iron lathes date to a time when stress and strain calculations weren't well understood and the number crunching was too costly to do manually. Lathe designs are based on experience, basically if something broke or bent, more metal was poured next time. Gradually the necessary dimensions became well-known, mostly over-engineered. There's a serious disadvantage: the extra metal adds size and weight and it all costs money owners might have better uses for. The disadvantage becomes painful when competitors use modern techniques to make improved lathes for less money.

Chinese lathes are based on more modern European ideas. Designed to be made at minimum cost , functional without unnecessary material or curlicues. The bed is analysed as a braced girder using methods and understanding not available to the old-iron engineers. No gap in the bed considerably simplifies the analysis.

The build quality of Chinese lathes may not be impressive but the design certainly makes more effective use of materials. They are cheaper to make and there's a good chance they are stronger too. Looking at CNC and manufacturing equipment, it's apparent they are from the same school as Chinese lathes, and they don't resemble traditional old-iron much.

Trouble is no-one knows. Old-iron looks good but the design is probably sub-par. Modern machines look flimsy but were designed 40 years later by advanced engineers. Be interesting to compare the strength of an ML7 bed & headstock with that of a Chinese lathe of the same weight. I don't think it's ever been done.

Possibly lathes are a special case, but old cars, aircraft, ships, locomotives, radios, televisions and most other manufactured goods rarely compare well with their modern equivalents. For example, a WW2 Spitfire IX Fighter had a top speed of 595km/h and a ceiling of 11,125m. A Boeing 737 cruises at 836km/h with a ceiling of 12,500 metres. An ordinary commercial airliner couldn't be intercepted by one of the best fighters of its day. The comparison is even more stark when Boeing's performance is compared with a Sopwith Camel!

Dave