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View Full Version : How do you measure swing on a lathe?

1-800miner
04-07-2013, 02:54 PM
Do you measure from center,diagonally to a way?
Or measure vertically to a point half way between the ways?

One measurement makes my machine a twelve inch.
The other way makes it a thirteen inch.

Peter.
04-07-2013, 02:57 PM
I would measure from the centre-line to the nearest thing it will touch, since that is what matters to what you can mount in the chuck.

dp
04-07-2013, 03:13 PM
I am probably inconsistent with the world on this but I consider it the largest diameter at which you can remove metal. It may be possible to get a large swing with a gap bed but if you have no tools that will reach the OD then you have a large swing area within which you have a smaller work area. For me the swing area is nice to know but what I need to know is the working diameter. And of course I'm limiting my definition to home shop machinist class machines.

Dr Stan
04-07-2013, 03:17 PM
There are two different ways to measure the swing.

One is the swing over the ways. Find it by measuring from the axis of the lathe to the closest point on the ways, typically the top of the V on the back side of the ways then multiply it by 2.

The 2nd is to measure from the axis to the top of the cross slide. Again multiply by 2 and you'll have the swing over the cross slide.

loose nut
04-07-2013, 04:09 PM
North America uses the swing IE: the diam that can be turned over the bed.

England and other "colonies" use the center height IE: the distance from the lathe center to the bed or 1/2 the swing.

I use the cat method. Tie a cat by its tail to the center of a chuck and turn the lathe on. If the cat doesn't survive then you didn't have enough room to swing a cat by it's tail.:eek::D

flylo
04-07-2013, 04:25 PM
Loose Nut, sounds like about the same to me. Moral of the story buy a big enough lathe or own a small cat. Seems to me the larger production lathes measure over the cross slide while the smaller cheaper models measure over the ways, My American Pacemaker is tagger a 14" but measures 17"+ to the ways. Just my opinion.

Peter.
04-07-2013, 05:08 PM
England and other "colonies" use the center height IE: the distance from the lathe center to the bed or 1/2 the swing.

Not always. My Denford '280' swings - 280mm diameter.

Thomas Staubo
04-07-2013, 05:48 PM
Myford ML7 or Super7 = 7" swing, but was advertised as a three and a half inch lathe.

.

Georgineer
04-07-2013, 07:50 PM
Myford ML7 or Super7 = 7" swing, but was advertised as a three and a half inch lathe.
.
Thomas,

The 7 in ML7 was merely the next model number after the ML6. My ML4 is also a 3 1/2" lathe. I believe the ML2 was 3 1/2", and the ML1 and ML3 were 3 1/8". The ML8 was a woodworking lathe.

George

chipmaker4130
04-07-2013, 08:19 PM
Seems there was a time when 'swing' meant the length of stock one could swing arount the center without hitting anything. Then, just like with hp ratings on electric motors, as soon as somebody started using the term to describe max stock diameter, everyone followed along.

loose nut
04-07-2013, 08:34 PM
Not always. My Denford '280' swings - 280mm diameter.

My reference was back in the pre-metric/EU days, the Myford 254 was a 10" lathe

dmschmidt1200
04-07-2013, 09:44 PM
I use the cat method. Tie a cat by its tail to the center of a chuck and turn the lathe on. If the cat doesn't survive then you didn't have enough room to swing a cat by it's tail.:eek::D[/QUOTE]

Thats sum funny crap right there!!

darryl
04-07-2013, 09:55 PM
I sort of looked at it as a regular kids swing- how long are the ropes- 8 ft long, that's the swing, even though it would sweep out a 16 ft diameter. But I do think it's a point to keep in mind that it's specified different ways. No point in buying a replacement lathe that's 'larger', only to find out is won't swing as much as the old one.

I look at swing over the cross slide the same way- in terms of radius, not diameter.

What dp said is interesting. I've run into this several times- not being able to position a tool to a point where you could cut on the outside diameter of a workpiece. If the tool can't reach, then the machine doesn't have the capability- at least without modifying it. You would have to define the worn 'turn'. Usually that means remove material, as in 'turn the piece down', but it could be taken as simply rotating the part without having it smash into things.

My lathe should be called a 2-7/8 (swing over cross slide):)

1-800miner
04-07-2013, 11:03 PM
I am trying to id an old Sebastion lathe.
I can find some info on thirteen inch but no info on twelves.
So I will rephrase the question: How do the lathe manufacturers measure their machines?

Jaakko Fagerlund
04-07-2013, 11:45 PM
The usual I've seen is to tell what is the maximum diameter over bed and the maximum diameter over the saddle, as both are quite necessary to know if planning work for the machine. Plus the maximum length between centers of course.

RussZHC
04-08-2013, 12:34 AM
The usual is sometimes "undone" by manufacturers...IIRC having read multiple examples of how some lathes were called a given size but actually swung another size, in some cases considerably more and it seemed to be a bit more prevalent very early in 1900s and just pre and post WWII, I seem to recall having read Monarch for one could actually swing about 2" larger than what they were called.
I have in mind a photo I recently saw that Monarch even had a space on some plates that listed the "swing" (usually what the lathe was called, 14" for example) and had a spot for "actual".

One of the other factors was frequently, more so by some makers, that a lathe a size up could be made with minimal fuss but this was not always the case and it seems to depend a little bit on the sizes in question. It means parts can, in some cases, interchange simply but I also suspect in some cases there is missing information as those common parts would be mentioned in an overview but not again. Again, IIRC, from Tony's lathe site, LeBlond had in the 30s, 40s and maybe into the 50s only a couple of apron styles spread across quite a few model sizes. There were also so many twists and turns to makers that information just gets lost in restructuring or ownership changes/amalgamations.

Edit: you may have some luck asking on the sheldonlathe group site since late in Sebastian's existence, there was a take over there...problem of course being a lot of Sheldon info is missing as well for various reasons