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Why a round bed?

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Former Member01/06/2019 20:57:39

[This posting has been removed]

JohnF01/06/2019 21:28:45
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874 forum posts
103 photos

I would suggest ease of manufacture and economy, think how much more difficult it is the make a prismatic or flat bed and fitting all the components, saddle tailstock headstock -- far easier to turn/grind a long parallel tube and bore holes !

John

ega01/06/2019 22:37:10
1290 forum posts
109 photos

The Barker lathe - see lathes.co.uk - used round bed components in a rather different way and was also "triangular".

Nicholas Farr02/06/2019 07:16:50
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1992 forum posts
950 photos

Hi, have you read this **LINK** it may help you to understand some of the reasons for the design.

Regards Nick.

Nigel McBurney 102/06/2019 09:02:28
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614 forum posts
3 photos

The really clever bit of this round bed,is the ability to rotate the saddle to adjust the centre height above the crosslide.

Former Member02/06/2019 09:53:32

[This posting has been removed]

Ian S C02/06/2019 13:26:17
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7447 forum posts
230 photos

The round bed is much cheaper to make than the more complex patterns required for a conventional lathe bed, most of the work on the bed could be done on a lathe.

Ian S C

Ron Colvin02/06/2019 14:42:32
54 forum posts
3 photos
Posted by Nicholas Farr on 02/06/2019 07:16:50:

Hi, have you read this **LINK** it may help you to understand some of the reasons for the design.

Regards Nick.

Tried calling Guildford 153, but so far no response. I wonder if the M.O.D. still have some in storage that they would be willing to sell off at low cost.

Clive Foster02/06/2019 15:35:41
1867 forum posts
59 photos

As always its a matter of striking a good balance between cost and capability given the needs of the intended purchaser, the depth of his pocket and the equipment in the factory.

In this case simple to make to good basic accuracy, versatile if the saddle and tailstock are made to rotate around the round bed. Major disadvantage of the system is that its intrinsically a right pain in the butt to get properly re-aligned after rotating things. Another, less than obvious issue, is that there are no reference surfaces. Everything is set relative to the (imaginary) axis of spindle rotation. Theoretically the sides of the slot under the bed ought to be reference but such are not accessible in normal use and, if the examples I have seen are anything to go by, are not defined in rotation relative to the spindle axis. Just longitudinally.

Of course in that day and age a conventional machine would have been unaffordable for the vast majority of potential customers. So the inherently fiddly nature and impossibility of truly accurate replication of set-ups had to be accepted. Modern multifunction machines aren't, in practice, that much better.

Two important things about then and there are often forgotten these days. First is the much greater relative expense of machinery in those days purely due to considerably less capable factory equipment requiring rather more direct, handwork, man hours at local pay rates. No cheap offshore or "China Inc". Secondly essentially no used machines around suitable for amateur use. So folk had to start off with a new machine. No working your way up market from something at saved paper round or first couple of weeks wages money dug out of your mates or Dads mates shed. (From Portass S with broken headstock bearing to Smart & brown 1024 over 35 or so years in my case.) Hence affordable new machinery was needed so significant disadvantages relative to "proper" designs were acceptable. Think below bottom end import mini-lathe today.

Things have changed. Here and now its a curio and, as a lathe basically total piece of crap. When I first got the bug back in 1970 a round bed was still marginally viable. But the world has moved on. A thing of its time and its time has passed.

Clive

Edited By Clive Foster on 02/06/2019 15:36:18

Nick Clarke 302/06/2019 18:43:40
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405 forum posts
12 photos

Clive - I must firstly declare an interest and say that I have roundbed under the bench as a long term project, but I can't accept that it as bad as you have written.

When put back together it will do as much as it ever could (I hope) and yes all of those weaknesses you describe are there, and always were there. What you can't do is wind in so many divisions on a dial and expect a workpiece to be to size. You have to measure and check. However despite all of the issues the older lathe can be set up accurately while the advice for some cheaper lathes today is, to quote a poster in a different thread, to treat them as a set of parts and set them up after purchase. If you haven't the adjustment left to do that then it needs to go back to the supplier.

Modern machinery is easier to use and has more features but unlike an older lathe may not be in a position to be put back into service 100 years after manufacture - as accurate and capable as it ever was - but no more.

Interestingly in my opinion as an addition to the imported machinery; the reason why so much excellent professional equipment is available to the amateur today is down to manual machines not being so prominently used in industry as before, and the lack of engineering taught in schools and colleges. This has brought to the market a large number of lathes and other machines. In 20 years time I suspect the machines coming from these sources will be far fewer in number and probably CAM based using incompatible out of date software or damaged electronics. Possibly even unusable.

 

Edited By Nick Clarke 3 on 02/06/2019 18:47:01

Ian S C03/06/2019 12:29:09
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7447 forum posts
230 photos

Although cheap compared to other lathes in it's day, it was still very expensive for the average worker, that's why a number of little lathes such as the Super Adept came out in the between wars period.

Ian S C

Bazyle03/06/2019 13:37:48
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4760 forum posts
187 photos

At the same time as Drummond were selling the roundbed they were also selling 'conventional' flat bed lathes. Perhaps someone can find an old ME with both types advertised to compare the prices.

Andrew Tinsley03/06/2019 13:38:01
923 forum posts

I have a Drummond round bed. I have graduated the hand wheels and cleaned and fettled the lathe. I find it surprisingly good, once you have got used to it. I don't find it difficult to set up either.

The one thing that lets it down is lack of a back gear. I wished I could find one of the aftermarket back gears that were made for the old round bed.

I have more modern lathes than the Drummond, but it gets used quite a lot, so that must say something about the lathe. Clive would probably say it says a lot about me!

Andrew.

Nick Clarke 303/06/2019 14:29:05
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405 forum posts
12 photos
Posted by Bazyle on 03/06/2019 13:37:48:

At the same time as Drummond were selling the roundbed they were also selling 'conventional' flat bed lathes. Perhaps someone can find an old ME with both types advertised to compare the prices.

The manual on this site describes the 3 1/2" lathe as "being again modified in 1921" and the price is £21-10-00 for a bench lathe. A 1923 ME lists a roundbed as a bench lathe at £9-10-00 

I think it would be safe to assume these are from the same date.

 

Edited By Nick Clarke 3 on 03/06/2019 14:29:59

Hollowpoint04/06/2019 17:15:59
225 forum posts
28 photos

The little unimat sl uses 2 round rails for the bed, I'm supprised at how rigid this setup is for such a tiny lathe. I,ve always thought a larger lathe based on this design using newer technologies like linear bearings could produce a very good economical lathe. You could eliminate the need for gibs for example! How nice would that be?

Edited By Hollowpoint on 04/06/2019 17:17:24

Martin Hamilton 104/06/2019 18:38:03
139 forum posts
Posted by Hollowpoint on 04/06/2019 17:15:59:

The little unimat sl uses 2 round rails for the bed, I'm supprised at how rigid this setup is for such a tiny lathe. I,ve always thought a larger lathe based on this design using newer technologies like linear bearings could produce a very good economical lathe. You could eliminate the need for gibs for example! How nice would that be?

Edited By Hollowpoint on 04/06/2019 17:17:24

Wabeco still offer round bar bed lathes like the Unimat SL but much larger, besides there cast iron bed lathes as well.

Lee Rogers10/06/2019 14:08:40
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5 forum posts

I have to put in a good word for the roundbed. A handy machine if used within reason and still very popular. You do need to bin the insert tools and learn to grind HSS . Also think rigid with all your set ups. I've seen so many forum posts about poor finish on old lathes and the problem is nearly always a carbide tool in a QCTP with more overhang than a pagoda. A good roundbed that's well equipped will still fetch a good price because it's capable, compact and light.

Nick Clarke 310/06/2019 14:31:49
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405 forum posts
12 photos
Posted by Lee Rogers on 10/06/2019 14:08:40:

I have to put in a good word for the roundbed. A handy machine if used within reason and still very popular. You do need to bin the insert tools and learn to grind HSS . Also think rigid with all your set ups. I've seen so many forum posts about poor finish on old lathes and the problem is nearly always a carbide tool in a QCTP with more overhang than a pagoda. A good roundbed that's well equipped will still fetch a good price because it's capable, compact and light.

I agree except for the last part - for a small lathe, mine is ********** heavy!!

Keith Long10/06/2019 15:10:02
793 forum posts
10 photos

I find that I use insert tooling quite a bit on my Drummond roundbed, so don't dismiss it too readily, and yes they are HEAVY. A bare roundbed ie just the lathe without drip tray, motor or stand is about 50kg, definitely not one for carrying upstairs single handed. If you look at the long bed version (an extra foot in length) then the drip tray for that alone is well above any weight you want to carry.

not done it yet10/06/2019 15:26:35
3476 forum posts
15 photos

50kg heavy? A bag of cement or fertiliser weighed that amount when I was younger. Only baby bags of cement these days!

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