Lathe Design Question

[Dan Wickles]

I have decide to build my lathe with a 1"-8 head stock spindle. It looks like I can have a low RPM of about 14 without too much of a problem. So here is my next question.

How big of a 'swing' should I have? My bed material I am using is about 6" deep. So I can build with a swing of 7" or 14".

 

[Barbara Gill]

What about 21"? I would go for 14" rather than 7". Of course that is strictly from a turning opinion as I know nothing about building a lathe.:cool2:

 

[Ken Grunke]

I have decide to build my lathe with a 1"-8 head stock spindle. It looks like I can have a low RPM of about 14 without too much of a problem. So here is my next question.

How big of a 'swing' should I have? My bed material I am using is about 6" deep. So I can build with a swing of 7" or 14".

I don't follow that last part, how is it determined that you can get a swing of 7" or 14", or a multiple of 7? I must be missing something.

You may be concerned about underdesigning your lathe, but it's also possible to overdesign it. Don't give it more capacity than it can handle. You will be pushing it if you turn a 20" bowl on a 1" spindle, for example.
You can beef up the spindle shaft to 1 1/4" or 1 1/2" and keep the 1" x8 spindle nose I would think. Also, some distance between the bearings will help--8" is better than 6", and 10" is even better for more stability and less vibration/chatter when turning.

 

[Dan Wickles]

6" I Beams

I am using 2 6" tall steel I-Beams I have. Both are 48" long. One is straight enough for the bed. The other, with big dings, will have to be cut up to be usable. So if I stagger the bed and head stock portion of the I-beams there will be a 'gap' under and to the right of the spindle end. Swing will increase by the bed material size, 6".

The IIII is I-beam material, Please Ignore the periods......They were the only way I could space it out.

OO.(Spindle).OOO..................................<<<<(Tail Stock)
III...............III......................................IIII
III...............III.(Gap)..IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII(Bed)
IIIII(Head Stock)IIIIIIIIIIIII

Hope this crude drawing helps.

I see that alot of chucks and face plates come with 1"-8 threads. Adding a different size spindle nose did not cross my mind. Are the chuck and face plates that have the center adapter strong enough to handle the larger sizes of bowls and platters? Will the adapter limit the usable strength?

The bearing blocks will be wide enough to get 6 pulleys between them. At this point changing to 1 1/4" or 1 1/2" spindle is not a problem.

 

[hockenbery]

1 1/4 x 8 Is probably the most common spindle thread size on the more popular lathes used for bowls and hollow forms.

Powermatic, larger Jets, stubby, Vicmarc General ..... all use the 1 1/4 x 8

Stacking 2 6" I beams give you 12' from center to bed which is a 24 capacity
which means you can comfortably turn 22" diameter pieces and still move the tool rest under the work.

the above mentioned lathes have 20" and 24" capacities

-Al

 

[Richard Baker]

Dan,
Uncertain what actual spindle diameter you intend to use. For 1-1/4 x 8 threads plus, let's say, 1/4" wide shoulder, that is an 1-3/4" minimum spindle diameter. Good ideas from Al.

 

[KEW]

If you are using a 1X8 spindle, 14" swing is a pretty good match. I believe this is what Jet uses on their 14" swing lathe (JWL-1442, IIRC). If you are going to 16" swing or bigger I'd go with a 1-1/4" spindle.
Either of these two sizes would avoid any significant problems finding mating accessories.

 

[Joe Greiner]

The only place that 6" gets into the act is the difference between the swing over the bed and the swing over the gap (increases the swing by 12" as "swing" is currently defined). Actual swing over the bed will be determined by the size of the pillow blocks supporting the headstock spindle, which is in turn (no pun intended) determined by the spindle size. If you're using a surplus tailstock, either that or the headstock pillow blocks may need to be shimmed to achieve alignment.

Unless you go really huge, the 6" I-beams, with substantial overlap at the gap, should be robust enough. You still need a motor that has enough grunt to turn the piece.

Joe

 

[Malcolm Smith]

I'd certainly become familiar with the designs of the leading manufacturers. Added capacity requires that a lathe be a great deal heavier/sturdier. Even a small amount of added capacity. The head stock and tailstock should line up perfectly. This is a problem with a great many lathes. The headstocks don't rotate on the Oneway lathes which contributes to the line up. I don't know what your intention is with regard to outboard turning. Oneway lathes have many advantages for outboard turning especially as the chucks and faceplates can be locked on with set screws. One can turn either in forward or reverse.

Just a few thoughts. You're taking on quite a project.

Malcolm Smith.

 

[Captain Eddie]

Don't sell the engineering that others put into a lathe short. I've designed and help some heavy stuff using I-beams only to see it flex. The webs are designed to transmit a portion of the live load to the sides of the beam. This transmission is commonly called "Flex". Lathe manufacturers tend to lean towards tubular design, both horizontal and vertical, to help transmit that load without flex.
If you stack up beams, and not add web stiffeners where the load is transmitted, you will have a beautiful tool for chatter work. If you design in cross bracing into your support, you will have a very rigid design and then you have to consider bearings, strength of the shaft and adequate support for the shaft.
I'd give it a whirl, but be ready to measure the runout with a load when completed.

 

[rjones]

the question that you need to ansewer first is why.( This is a very serious question ) you have to know ever reason why.

 

[Dan Wickles]

Don't sell the engineering that others put into a lathe short. I've designed and help some heavy stuff using I-beams only to see it flex. The webs are designed to transmit a portion of the live load to the sides of the beam. This transmission is commonly called "Flex". Lathe manufacturers tend to lean towards tubular design, both horizontal and vertical, to help transmit that load without flex.
If you stack up beams, and not add web stiffeners where the load is transmitted, you will have a beautiful tool for chatter work. If you design in cross bracing into your support, you will have a very rigid design and then you have to consider bearings, strength of the shaft and adequate support for the shaft.
I'd give it a whirl, but be ready to measure the runout with a load when completed.

Where I stack the beams I planned to add some vertical supports, spanning the entire stack. Should these verticals be bolted thru the webs? If I run washers and nuts up to the webs, where the bolts go thru, will this give enough flex deterence? Should the verticals also support the top and bottom of the beams?

 

[n7bsn]

Dan
Do you have a source for head? I'm in the planning stages for building a treadle lathe.....

TTFN
Ralph

 

[Dan Wickles]

Dan
Do you have a source for head? I'm in the planning stages for building a treadle lathe.....

TTFN
Ralph

I am planning on piecing my head together from parts. Pillow blocks will come from 'Burden Sales Supplus Center' or 'MSC-Direct'. The spindle stock will come from MSC. Pulleys will come from E-Bay(with any luck) or Burden.