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What are members thoughts on Gap Bed lathes ?

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colin hawes04/10/2019 13:39:49
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I would always prefer a gap bed lathe for its versatility. Colin

Packmule07/10/2019 20:26:37
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Thanks everyone for your replies.

Will definitely look at the Chester at the show and looks like a trip down south to see the Warco.

Gray07/10/2019 20:32:04
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Having owned both Chester and Warco machines (both current lathes are from Warco) and having experienced after sales from both, my money would always go to Warco.

I've owned a GH1330 for 14 years, the gap piece comes out frequently and goes back without issue, never had any alignment issues and the lathe turns parallel (within acceptable tolerances for the work I do)

Gray

not done it yet08/10/2019 08:57:20
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Having read Gray’s comment, it made me think that the initial bed would need to be ‘aged” to ensure no movement after finish machining. That would mean less or no ”twist’ in the bed to be adjusted away by the levelling process.

Nowadays, nothing is aged like castings used to be, and if the bed requires ‘twist’ removal, to cut parallel, the refitting of a gap piece might be more prone to inaccuracy or difficulty.

The origin of Gray’s machine might even be a factor - china or Taiwan? We (all) know that while chinese machines are somewhat better these days, than previously, they are likely using less metal than older products of similar capacity.

SillyOldDuffer08/10/2019 10:14:35
5323 forum posts
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Posted by not done it yet on 08/10/2019 08:57:20:.

...

The origin of Gray’s machine might even be a factor - china or Taiwan? We (all) know that while chinese machines are somewhat better these days, than previously, they are likely using less metal than older products of similar capacity.

Maybe, but:

  • Common short-bed ML7, 177mm Swing, (254" in gap), 508mm between centres - 91kg
  • WM250, 250mm swing, 450mm between centres - 125kg

Could argue:

  1. the ML7 is more lightly built because it's only fitted with a weedy 0.5hp (375W) single-phase motor, whereas the latest WM250 punches with a he-man brushless 1100W.
  2. the WM250 must be stiffer than an ML7 because its bed contains more metal and has no gap to weaken it.
  3. The ML7 wastes rather a lot of metal on those elaboratly shaped guards. In comparison, the WM250's innards are inside a simple light-weight sheet-steel box. The Chinese lathe makes better use of the weight.

Actually, such arguments are pretty dubious. The proof of the pudding is in the eating. Never mind who made the lathe, is it possible to tell the difference between an item turned on an ML7 with the same item turned on a WM250? In practice, I suspect the performance and capabilities of the two machines would be indistinguishable in a blind test. Subjectively though, when I played with a Super 7, I thought the controls were smoother - the Myford felt and looked good in a way my utilitarian WM280 absolutely doesn't. But the WM280 has size advantages - it's significantly bigger than a Super 7.

Horses for courses...

Dave

Michael Gilligan08/10/2019 11:01:55
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Posted by SillyOldDuffer on 08/10/2019 10:14:35:

[…]

The ML7 wastes rather a lot of metal on those elaboratly shaped guards. In comparison, the WM250's innards are inside a simple light-weight sheet-steel box. The Chinese lathe makes better use of the weight.

[…]

Horses for courses...

Dave

.

Metal in this case being mostly Aluminium

... But I agree wholeheartedly with your concluding remark.

MichaelG.

Andrew Johnston08/10/2019 11:24:51
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Posted by SillyOldDuffer on 08/10/2019 10:14:35:
  1. The ML7 wastes rather a lot of metal on those elaboratly shaped guards. In comparison, the WM250's innards are inside a simple light-weight sheet-steel box. The Chinese lathe makes better use of the weight.

Otherwise known as a drum. Just because something uses less metal doesn't mean it's automatically better; cheaper yes, but not always better. Sheet steel cabinets are notorious for vibrating. They often need stiffening to avoid the problem, which can feed back into a poorer surface finish.

Andrew

SillyOldDuffer08/10/2019 11:39:57
5323 forum posts
1089 photos
Posted by Michael Gilligan on 08/10/2019 11:01:55:

Posted by SillyOldDuffer on 08/10/2019 10:14:35:

[…]

The ML7 wastes rather a lot of metal on those elaboratly shaped guards. In comparison, the WM250's innards are inside a simple light-weight sheet-steel box. The Chinese lathe makes better use of the weight.

[…]

Horses for courses...

Dave

.

Metal in this case being mostly Aluminium

... But I agree wholeheartedly with your concluding remark.

MichaelG.

Of course, and my remark about the WM250's "he-man brushless 1100W" is similarly tongue-in-cheek. Myfords have performed perfectly well for 7 decades with 'only' 0.5HP of bumpy single-phase: although the motor could be 'better' it's really not a mission critical fault!

By training and personality I'm from the only-just-good-enough, fit-for-purpose and value-for-money school of engineering. But that's just me. Others value the feel of expensive tools and relish pride of ownership. Perfectly respectable, especially if it improves output and enjoyment. But advising newcomers to avoid buying Far Eastern because of those feelings is likely bad for the future of the hobby. I'd rather newcomers bought a lathe, got stuck in, and made their own minds up.

Nothing is black and white and I don't follow my own philosophy consistently! For instance I'd rather write in ink with a decent italic nibbed fountain pen on heavy cream paper than scribble exactly the same message in biro on the back of an old envelope...

smiley

Dave

Hopper08/10/2019 12:24:38
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The WM250 is in effect a gap bed lathe. The bed just continues along at the lower level of the gap whereas the Myford bed rises up that inch or two at the end of the gap. That is how the WM250 can swing a 250mm diameter job over the bed,

To make up for this, the WM250 has the tool bit perched way up high on top of a thicker carriage, cross slide, top slide and tool post.Same with the tailstock perched up on a thickened base. Thus introducing the added flexing and chattering in these areas that the Myford does not have.

And I'm not sure the relative weights is a meaningful comparison. Myford usually qiuoted their weights minus the electric motor, which was an "extra" (and usually a 3/4hp not a half btw.). So much of the WM250 weight may be that honking great 1100kw motor, which it needs so that is has sufficient power at lower rpm on a variable speed motor, some thing Myford avoided by use of a torque-multiplying counter shaft. Does not really say anything about relative bed rigidity as soo many other factors involved.

 

Edited By Hopper on 08/10/2019 12:42:57

SillyOldDuffer08/10/2019 13:26:43
5323 forum posts
1089 photos
Posted by Hopper on 08/10/2019 12:24:38:

The WM250 is in effect a gap bed lathe. The bed just continues along at the lower level of the gap whereas the Myford bed rises up that inch or two at the end of the gap. That is how the WM250 can swing a 250mm diameter job over the bed,

To make up for this, the WM250 has the tool bit perched way up high on top of a thicker carriage, cross slide, top slide and tool post.Same with the tailstock perched up on a thickened base. Thus introducing the added flexing and chattering in these areas that the Myford does not have.

And I'm not sure the relative weights is a meaningful comparison. Myford usually qiuoted their weights minus the electric motor, which was an "extra" (and usually a 3/4hp not a half btw.). So much of the WM250 weight may be that honking great 1100kw motor, which it needs so that is has sufficient power at lower rpm on a variable speed motor, some thing Myford avoided by use of a torque-multiplying counter shaft. Does not really say anything about relative bed rigidity as soo many other factors involved.

Edited By Hopper on 08/10/2019 12:42:57

The WM-250 is a gap bed lathe. Really? Never thought a gap extending the full length of the bed qualified but hey the point about towering tool-posts is a good one. The WM style lathes do have heftier saddles and wider beds than Myfords. Extra tool height doesn't seem to have worried Boxford.

The 91kg I quoted for a short-bed ML7 includes the motor, always assuming my source was right. Anybody know for sure?

Do WM250s chatter more than Myfords? I don't know. Anyone tested that?

Relative bed-rigidity is different too. The WM-type have an internally braced box structure typical of modern machine tools; their design is intrinsically stiff. Myford take a different approach: the bendiness of the bed is a feature exploited to fine-tune twist out and improve accuracy. That the bed can flex in the first place is glossed over!

Bob's original question was about Chester Craftsman vs Warco WM290. The Craftsman weighs 390kg and the WM290 is significantly lighter at 230kg. In that context, the gap isn't likely to matter much - the Craftsman is an altogether heavier machine.

What finished poor old Myford off as a business wasn't any of these technical comparisons. They went down because customers weren't prepared to buy enough new machines from them. The asking price was too high compared with competition from new Chinese and second-hand, especially the industrial bargains available due to the rise of CNC.

Dave

PS. Nice to know there's enough cast-iron in a Craftsman to make four ML7s!

Andrew Johnston08/10/2019 14:09:36
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Posted by SillyOldDuffer on 08/10/2019 11:39:57:

Of course, and my remark about the WM250's "he-man brushless 1100W" is similarly tongue-in-cheek.

Nevertheless, the boys at Britan clearly didn't know what they were doing. My repetition lathe has a two speed motor and it doesn't do star/delta switching, so it's only 750W/375W. Even worse than that it's about the same footprint as a Myford but weighs 750kg. Of course that includes the stand and auxiliary motor along with coolant and hydraulic pumps, and an air compressor. But there must still be a lot of surplus cast iron. sad

Andrew

Michael Gilligan08/10/2019 14:36:06
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Recommended reading: **LINK**

https://archive.org/details/lathebeddesign00hornrich

… I’ve mentioned it before

MichaelG.

not done it yet08/10/2019 20:32:34
4149 forum posts
15 photos

My comment of ‘china or Taiwan’ was to compare the same offerings from those two “far eastern countries - not, as SOD infers later, a cheap shot at chinese lathes.

Taiwanese products seemed, to me, to be somewhat superior to the chinese copies/replacements. No experience with lathes but there are several threads where the quality of Taiwanese rotary tables have been compared with the same brand name - but of chinese origin. Vertex was the specific brand name I was thinking of. Taiwanese - good, chinese - less good. But both probably better than a lot on the market! I felt quite smug/lucky when my second rotary table turned out to be a Taiwanese version, after reading those previous comparisons.smiley

Hopper09/10/2019 07:00:10
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Posted by SillyOldDuffer / not done it yet on 08/10/2019 08:57:20:.

...

 

Maybe, but:

  • Common short-bed ML7, 177mm Swing, (254" in gap), 508mm between centres - 91kg
  • WM250, 250mm swing, 450mm between centres - 125kg

Could argue:

  1. the ML7 is more lightly built because it's only fitted with a weedy 0.5hp (375W) single-phase motor, whereas the latest WM250 punches with a he-man brushless 1100W.
  2. the WM250 must be stiffer than an ML7 because its bed contains more metal and has no gap to weaken it.

Not sure why we are comparing apples with oranges here, again.

A WM250  is a 250mm or 10" swing lathe, over the bed. A Myford is a 7" swing lathe,over the bed.. Of course a 10" lathe is bigger, and therefore heavier than a 7" lathe.

Perhaps compare with other 10"/250mm lathes? Both the South Bend 10" and the Raglan LIttlejohn weigh in at about the 200kg mark. Like the WM250 they swing 250mm diameter with no gap in the bed. So it is a direct comparison. So it seems the 125kg WM250's peers are more than 50 per cent heavier built.

If I wanted a good solid 10" / 250mm lathe I'd be looking for a South Bend or Raglan in good condition. Or a Boxford. Or either of the Warco 290 or Chester Craftsman in the OP if I wanted to buy new. Both of which are bigger lathes than a Myford by a large amount.

The Myford ML7 was originally a small, low-cost (34 Quid vs 45 for a Drummond in 1948), model engineer's lathe by comparison. With the compromise of the gap bed so it could be pressed into service to machine a 10" flywheel or loco wheel etc if needed. But it still compares well with other 7" lathes, or 180mm in modern parlance, such as the WM180, which weighs in at 70kg.

 

 

Edited By Hopper on 09/10/2019 07:22:15

Edited By Hopper on 09/10/2019 07:25:21

JasonB09/10/2019 07:33:22
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Posted by Hopper on 08/10/2019 12:24:38:

The WM250 is in effect a gap bed lathe. The bed just continues along at the lower level of the gap whereas the Myford bed rises up that inch or two at the end of the gap. That is how the WM250 can swing a 250mm diameter job over the bed,

To make up for this, the WM250 has the tool bit perched way up high on top of a thicker carriage, cross slide, top slide and tool post.Same with the tailstock perched up on a thickened base. Thus introducing the added flexing and chattering in these areas that the Myford does not have.

For a moment there I thought you were describing a Myford 254. Just look at that even higher base to the tailstock and the unsupported overhang of the topslide. Still does not stop the majority of Myford fand lusting after onedevil

Edited By JasonB on 09/10/2019 07:35:39

Michael Gilligan09/10/2019 08:45:57
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Posted by JasonB on 09/10/2019 07:33:22:

[…]

For a moment there I thought you were describing a Myford 254. Just look at that even higher base to the tailstock and the unsupported overhang of the topslide. Still does not stop the majority of Myford fand lusting after onedevil

.

An interesting assertion, Jason ... which, if true, puts me in the minority.

When I saw the 254 at Myford’s Beeston open-days, it did nothing to attract me.

My ML7R is much closer to my ‘Goldilocks zone’ machine in terms of size and capacity.

... I would rather they had further-developed that range, to bring it up closer to Schaublin 70 standards.

MichaelG.

Hopper09/10/2019 10:44:34
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Posted by JasonB on 09/10/2019 07:33:22:

For a moment there I thought you were describing a Myford 254. Just look at that even higher base to the tailstock and the unsupported overhang of the topslide.

Ah, but Myford have cunningly incorporated a threaded feedscrew fitted with a right-angle crank handle into the topslide. By manipulating the crank handle in an anti-clockwise direction, the astute operator can move the position of the topslide to such an extent that overhang is reduced to nil, or even less.

Nigel McBurney 109/10/2019 10:51:51
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I would go for a gap bed lathe any day,that extra capacity can be very useful ,The Myford gap is ideal for traction engine wheel rims and flywheels. a gap on any lathe allows easier mounting of angle plates on to face plates for boring. The proportions of the 7 series lathes are very good except for the spindle bore,The 254 always look a bit too tall and possibly not so rigid though I would prefer one one against a far eastern product.Though if it had been given better proportions the cost would have taken it out of the hobby /training market.Going bac to gap bed V straight bed,I was some years ago at a MOD auction and was looking at some Colchesters mainly students ,one was in excellent condition and had an extra long straight bed,ie no gap. Two dealers came along looked at it ,one cussed and said ,'no gap' that will be a difficult sale ! and went to look at the next machine.Always remember a machine may suit you but take into account you may want to sell it sometime .

Neil Wyatt09/10/2019 11:48:16
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Posted by Michael Gilligan on 08/10/2019 14:36:06:

Recommended reading: **LINK**

https://archive.org/details/lathebeddesign00hornrich

… I’ve mentioned it before

MichaelG.

It's interesting that the Myford design has a 'continuous' lengthwise web between the two shears, creating a 'H' cross section which is good, but not as good as the ideal but impractical box-section.

Mini lathes copy many historic lathes by having vertical webs at intervals between the two shears, probably adequate for smaller lathes.

The SC4 has an interesting variation - cross-webs at intervals, but these have very thick longitudinal webs at the top - giving them a T-shaped cross section and effectively providing a '50%-pierced' lengthwise web between the shears. I suspect this is comparable in stiffness to the Myford and has the advantage that accessories like fixed steadies can have their keep-plates easily attached from below, no need to remove the tailstock to slide the assembly on.

So... I wouldn't be in a hurry to condemn either the SC4 or the Myford for poor bed design in those respects; obviously the double-V design of the SC4 is more modern and arguably less vulnerable to wear (as the saddle just drops down rather than becoming loose with modest wear).

Neil

JasonB09/10/2019 11:48:57
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Posted by Hopper on 09/10/2019 10:44:34:
Posted by JasonB on 09/10/2019 07:33:22:

For a moment there I thought you were describing a Myford 254. Just look at that even higher base to the tailstock and the unsupported overhang of the topslide.

Ah, but Myford have cunningly incorporated a threaded feedscrew fitted with a right-angle crank handle into the topslide. By manipulating the crank handle in an anti-clockwise direction, the astute operator can move the position of the topslide to such an extent that overhang is reduced to nil, or even less.

The Warco must have copied that novel feed screw idea as you can do the same with theirs except it has less overhang than the Myford at either extent of travel. smiley

What Myford forgot to do is notch out the saddle which means any large diameter work requires the topsilde to overhand if you are going to avoid the work hitting the carrage first. On my 280 and Daves 250 you can swing the full quoted diameter and get that right up against the side of the cross slide, looks like you loose 40-50 on the Myford 254.

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