Thread: lathe bed size vs. swing on pecision bench lathes

I have been picking up a few old precision bench lathes including a couple of P&W models from 1920's or 30's and it seems that somewhere I once read that the bed size for the lesser swing lathes was also lower, and a bit shorter.
One of the Pratt and Whitney lathes last to come in has a bed that is rather larger than what looks right. The headstock and tailstock fit well, but they seem tiny sitting on the bed - compared to the larger swing stocks on beds of the same size.
Anyone know the particulars on this?


JR

I don't know from P&W stuff. But Hardinge Brothers Cataract lathes had only one bed width. There were 32 and 38 inch lengths available. On those beds would fit headstocks that took 3C, 4C, 5C, 6C and 7C collets. The 3C heads came in 7 inch swing. The others came in either 7 or 9 inch swing. The slide rests and tailstocks came in 7 or 9 inch swing. If you set a 38 inch bed with 3C headstock next to a 32 inch bed with 9 inch 5C headstock, the difference in proportion would be striking.

Larry

I have a friend with a Leblond Regal. He is proud of the fact that the lathe ways are wider on his lathe than on other 15" lathes he's seen. He figures it gives more strength and rigidity, while obviously costing more to manufacture.

A good lathe should have a bed width equal to its swing. Most older machines meet this requirement. Most new ones far fall short, especially those of large (over-rated) swing. We have a Meuser lathe at work with a 48" swing and a 17" wide bed. It's a joke. Similarly, the supposed 18" Nardini has a bed suitable for a 12" machine.

Originally Posted by Mike C.

A good lathe should have a bed width equal to its swing. Most older machines meet this requirement. Most new ones far fall short, especially those of large (over-rated) swing. We have a Meuser lathe at work with a 48" swing and a 17" wide bed. It's a joke. Similarly, the supposed 18" Nardini has a bed suitable for a 12" machine.

That is no doubt true of engine lathes.

But the question was about "precision bench lathes." Those lathes typically have a swing of 6 to 9 inches and have a slide rest that clamps tightly to the bed. There is no saddle that slides down the bed, so the bed design is totally different from engine lathes.

Larry

Even then, it's the WIDTH of the bed that gives rigidity and resists twisting. Get the widest bed you can find for a given swing in any lathe.

Well,the depth counts,too.

Originally Posted by Mike C.

A good lathe should have a bed width equal to its swing. Most older machines meet this requirement. Most new ones far fall short, especially those of large (over-rated) swing. We have a Meuser lathe at work with a 48" swing and a 17" wide bed. It's a joke. Similarly, the supposed 18" Nardini has a bed suitable for a 12" machine.

I doubt there were ever too many lathes where the width equaled the swing.. Maybe some very heavy duty ones, but pretty rare to see it on the more common ones.....

Originally Posted by Mike C.

A good lathe should have a bed width equal to its swing. Most older machines meet this requirement.

Yeah, that joke of a machine Monarch put out called the 10EE swung 12" but only had a 10" wide bed!

10EE is also a RATED 10" lathe that swings 12" over the bed (as are most older industrial duty machines). Going by its rated swing, it meets this requirement. The 22" L&S model X at work can swing more than 24" over the bed. It has a 22" wide bed. The old makers rated swing by the largest faceplate that would fit on the lathe and clear the wings. An honest rating of what you could do on the machine. This new method of rating a lathe by of every fraction of an inch you can clear the closest way is pure marketing. You cannot work on anything that doesn't clear the carriage wings, so it's a useless claim.

That said, 10" on a 12" lathe is still a lot closer than most new lathes you see these days. Ideal is bed width equal to swing. Less is acceptable in many cases, but most modern machines are a joke in this department. That awful Summit again comes to mind. 20" swing gap bed lathe with about a 12" wide bed. Bed was very deep in section, but still chattered and would not cut straight to save your life, even after being professionally leveled. A deep section lends rigidity, but still does not get the toolpost inside or on top of the front way, especially when when you get on large diameter work.

Think about it... you are turning a part that is slightly wider than the bed. Your turning tool is at the outside edge of, or hanging OVER the front way. The toolpost and comound are OUTSIDE the bed way and trying to pull the cross slide up on the back. Now put a light, narrow apron on it, make the cross slide extra long to get enough reach and very thin, so you can claim maximum swing over the slide. Put the compound and toolpost way up high on a block on the cross slide so you can get to center and make the compound slide narrow and thin to save room again. Don't bother to put a heavy tailstock and quill on it, 2-3" diameter will be plenty and put only two clamping bolts or a quick clamp and single lock bolt. Recipe for a crappy lathe. Now go look around and see how many lathes made after about 1980 are built this way.

That big Meuser at work was a huge disappointment. I was really looking forward to running a nice European machine, but it's about an 18" machine with a raised swing to get 48" out of it. Yes, it has a huge 48" four jaw chuck on it, but the bed is 17" wide and the tailstock quill is about 2 1/2" diameter. The tailstock has two 1" bolts. I had a 130" long piece of 14" 1018 material in it for roughing a few days ago and could only get about .300" depth of cut without it starting to buzz and hum, even with a steady only 4ft from the tailstock.

Hmph...........

The Logan that is being laughed-at in another thread that is begging to be locked....... it is a 10" swing, with a 7" wide bed..... not too bad for a lower-end-of-light-industrial type machine. Quite a number of S-B don't come that close.

Just checked my two. SB10L is 7" wide. 1918 18" L&S is 17" wide. I don't have to push the capacities of the SB having the L&S on hand. My old L&S is noticeably more rigid than the much larger import machine I run at work (Takane?) that has about a 30" swing and a bed about 14" wide. It's all triangulation. Look at how the cutter meets the work and how those forces are transferred to the bed. The older L&S lathes (and some herringbone Sidneys) also used the front flat tailstock way as a third direct support for the carriage. Adds mucho rigidity and reduces overall wear on the ways.

Originally Posted by L Vanice

I don't know from P&W stuff. But Hardinge Brothers Cataract lathes had only one bed width. There were 32 and 38 inch lengths available. On those beds would fit headstocks that took 3C, 4C, 5C, 6C and 7C collets. The 3C heads came in 7 inch swing. The others came in either 7 or 9 inch swing. The slide rests and tailstocks came in 7 or 9 inch swing. If you set a 38 inch bed with 3C headstock next to a 32 inch bed with 9 inch 5C headstock, the difference in proportion would be striking.

Larry

Much thanks Larry,

Indeed that would be a shocker in some ways to see. However it makes good business sense to provide just one bed for the different
headstocks.

Jordan

Suppose he is correct on that idea of more strength. Yes, though...the cost is higher to the maker and the buyer.

Light work is about all I would be putting those lathes through with expectations of accuracy.
Maybe they are not as bad as I believe, but sadly the way of the world now is more from less.

Thanks for adding that note, Larry. The bed designs of the precision type lathes being akin to watchmakers lathe beds.
In fact, they are merely large versions of the typical WW style American watchmakers lathe.

JR

Thanks to all of you for your replies directly, and indirectly. Most of you would be little interested in the type of lathe with the WW bed, as they do not cut threads, and are too light for many of the jobs you do daily.
Just the same, I would like to see a comparison of the true twist resistance of the engine lathe bed vs. the WW type.
If the WW bed were scaled up to something like 6 feet long (and proportionally wide and deep)...how would it compare to a well designed engine lathe bed?
I would not bother to compare the strength of the precision bench lathe cross slide with the saddle at that enlarged dimension, as it probably would fail to impress.

Jordan

I have thread cutting capability on several of my WW type watch lathes by Derbyshire and Levin. I also have thread cutting capability on my Hardinge Cataract, Hardinge ESM-59 and Rivett 504 precision bench lathes. Most people have never seen such equipment, but it does exist.

Small machines are well suited to making small parts. When I had to make a knurled-head screw with .060-90 thread, I used a Levin WW lathe to cut the threads, not my 12 inch Clausing lathe.

I did once see a Wade bench lathe with traditional watch lathe shape bed that used 6C collets and was substantially larger than the Cataract 6C lathes in bed width, length and weight. I did not buy it, so I cannot give you any actual measurements.

Larry

There is a big difference between engine lathes with carriages and the old school precision plain turning bench lathe. I don't know anything about engine lathes except the Myfords we used at school.

I have a Stark #4 which has a 9" swing and is really just a large WW watchmakers large with the swing much larger than the width of split bed.. It's always seemed me that the bed of the Stark is way too long for a clockmakers lathe, but if I don't ever use that end of the bed, who cares?. I have no way of justifying this, but I believe that my Stark was made with such a large swing so that you can turn larger diamater work, not heavy work. It was made for clockmakers who occasionally turn a light but large disk or something, not for turning huge chunks, even if they might fit on the
lathe.

I have briefly owned and used WW pattern watchmakers lathes and have found the beds way too large and clunky for fine work. I have a geneva pattern (D-shaped bar 'bed') 8mm Lorch that I really love but only use for fine work, which is why I have the Stark. I believe that the issue of rigidity in a watchmaker lathe is moot because they are made for the finest most delicate work only.
The Stark, as a WW lathe on steriods, may have rigidity issues but I don't know because it works great.

Best,
Rich
http://www.clockconservation.com

Precision bench lathes that have large swings were good for clamping clock frames on for precision drilling and boring of holes they have for gear shafts. They were not made for turning big chunks of metal,as has been stated.

The widths of their beds are not in the same category as engine lathes. I would not worry the least about the quality or design of Pratt and Whitney precision lathes,old Hardinges,and the like. They were first class lathes.