# Maximum Turning Capacity



## intjonmiller (May 20, 2016)

Practically speaking, what is the maximum turning capacity of a 10" Logan lathe? The brochure for my 850 says: Swing over bed and saddle wings: 10 1/2". Does that mean I could turn down a 10.5" part (10.5" before turning)? Or are there other limitations, such as how far I can retract the cross slide and compound? 

I'm not with the lathe at the moment. I have a lot of down time at work lately, so I'm drawing up some plans. I should probably be more patient and just try to measure things when I get home, but I figured it would be good to hear any other considerations that may not have occurred to me. 

For the sake of my current project I only need it to be a couple inches deep at that maximum diameter, in case that makes a difference (like reaching just that far with a specially ground tool or something).


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## Tony Wells (May 20, 2016)

That diameter is not the diameter of say, a shaft 2 feet long. That shaft would need to be smaller, because it would have to clear the cross slide. That 10.5 would be the disc it would spin without hitting the ways and "wings" as they call them, the extensions of the carriage. I suspect the shaft diameter max would be about 7", but I don't know. Someone with a lathe like it and a tape measure, or you when you get back to it could give that limit.

Many brochures also give the swing over cross slide as well.


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## kd4gij (May 20, 2016)

The short answer is no as Tony said. That said I have turned 12" on my 12x36 lathe. I had to turn the QCTP to mount a boring on the side facing me.


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## kd4gij (May 20, 2016)

This is a 46" sheave on a 36" gap bed lathe


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## Grumpy Gator (May 20, 2016)

_Jon,                                                                                                                    http://www.hobby-machinist.com/gallery/img018.94713/_


_ Here is the specs on a 9" Logan._
_More info in my photos._
_A price list and parts book from 1959._
_   **G**_


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## intjonmiller (May 20, 2016)

Like I said, I was talking about a shallow disc. I realize that clearing the cross slide is a further restriction. I was just asking about being able to creatively turn the absolute maximum diameter on a Logan lathe (thus the location of my post and the specific wording about a Logan lathe (correct me if I'm wrong but they never made a gap bed lathe) and a shallow disc).

As for the other measurement I wasn't currently asking about, it looks like the max from the center to the cross slide with the cross slide way/leadscrew cover removed (I would replace it with masking tape or something for such an operation, as obviously when trying to do a part of maximum diameter there would not be much cross sliding needed) is just barely over 3.5" (say 7.2" diameter).


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## wa5cab (May 20, 2016)

About 10-3/8" dia. if you turn your QCTP and compound around and use a backwards boring bar to reach along the part.


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## Tony Wells (May 21, 2016)

My instinct was pretty close, although immaterial to your quest. Just remember, however you have to go to reach it with a cutting edge, you're likely at a leverage disadvantage, so would be wise to avoid heavy cuts. 

And of course, you will need to watch out that you don't run over your jaws if you manage to chuck this piece. If the OD needs to be machined over the full length, of course you will have to flip it around, so plan accordingly.


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## intjonmiller (May 23, 2016)

This is a contact wheel for a belt grinder, which I will first cast in aluminum and then machine true, so I'm planning on having a recess in the sides, allowing me to chuck it on the center section, leaving the full perimeter clear for machining.


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## TOOLMASTER (May 23, 2016)

I came up a 1/4" to big the other day when i need to turn an outside edge


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## Richard White (richardsrelics) (Sep 28, 2016)

I restore OLD, old, old outboards, the kind with cast flywheels and such, while I can turn the OD on my 1913 Evinrude, 9 inch OD, I can't do the same for a 1915 Waterman, 11 inch OD... this is on my 1947 Logan 10 inch model 820.
Being mechanical , I will make a platform that will permit me to turn a 12 inch wheel, maybe more once I get the details figured out, OR I will try to find a 14 inch Logan or similar lathe


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## wa5cab (Sep 28, 2016)

Riser blocks aren't unusual to find on old flat-bed lathes but making the headstock riser on a V-bed is an expensive proposition.  If your only need for more swing is turning the OD of flywheels (and presumably not many of those), your cheapest and easiest and probably quickest solution is to find just the headstock part of a Globe Milling Attachment (see photo).  And a riser block for your tool post.  It and the tool post riser would only take a few minutes to set up after you make a bed adapter for it.  You will also need to make an arbor to mount a chuck of face plate to.  The only problem is that the one that I had, and all that I have heard of, have a No. 9 B&S taper.  Globe did offer an arbor with a threaded spindle nose but the brochure does not say what the threads are, and mine did not come with it.  If you decide to look into it, I have the complete brochure that the photo below is out of.


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