Old desk as bench for South Bend 10K lathe

I just acquired a wood office desk made in the 1930's which looks like it would make a good bench for my South Bend 10k lathe. The
desk has lots of drawers, very helpful for all the little (and some not-so little) hunks of metal that come to roost around metalworking machines.
The top is 50 by 34 inches and about two inches thick. Because of its age I'm fairly sure it isn't ersatz wood, but rather plywood or possibly even solid wood. The joinery is well done, the cabinetry straight-grained and clear of knots. It's a smaller and less-ornate version of this: https://www.facebook.com/LincolnDesks
The obvious approach is to just bolt the lathe and countershaft to the top of the desk, that wouldn't be any worse than the table it's on now. The lathe is far stiffer than either and straighter to boot.
I wonder if it might be better to bolt the lathe and countershaft to a sheet of half-inch or so plywood, just strong enough to support belt tension (which isn't all that great, there's a prop rod 'tween headstock and countershaft assembly) and place it on a cushion atop the desk. That isolates the lathe from irregularities in the desk, the cushion will serve to absorb at least some vibration.
Has anybody tried something like this? It's hard to believe a bench contributes much if anything to the stiffness of a machine tool, but it could contribute to vibration damping.
Thanks for reading, and any thoughts.
bob prohaska
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My South Bend 9" Model A is on a similar table but I put a sheet of 3/16 5086 aluminum plate between the lathe and the table top. It makes for a brighter work area and is not affected by swarf and cutting oil. And is easy to clean too. phil k.
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Metal is neat, but it's expensive. And, it's not clear to me that the greater stiffness is helpful; that's somewhat the question I'm trying to pose: The lathe was manufactured straight and true. Is it not better to let the lathe assume its natural shape, rather than forcibly bolt it to something most likely of contours different from those supporting it while it was made?
Metal, in particular has a high mechanical Q, so if the lathe is inclined to chatter a metal plate won't provide much, or any, dissipation.
I do appreciate the value of rigid mounting to help convey acoustic energy out of a structure; bolting a lathe down keeps it from ringing like a bell, at the price of deflection or painstaking alignment. One can also muffle a bell with a soft cushion, I think with less deflection.
Do you observe any particular tendency of the metal plate under your lathe to vibrate (I realize it's a hard comparison to make...)
Thanks for writing!
bob prohaska
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wrote:

http://www.atlasfdry.com/grayiron-damping.htm
The only chatter I see is from cutting with a wide bit like a corner rounding or cutoff tool, and slowing the spindle cures it. -jsw
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On Tue, 8 Aug 2017 05:45:19 -0000 (UTC), bob prohaska

No matter how straight your lathe was when made it will twist some when set on a surface that is not true. Then, if fastened down, it will deform more. No matter what surface you are going to attach it to the lathe will need to be leveled in order for it to cut straight. On a wood desk it will change over time with temperature and humidity. So bolt it to the desk top. Adding the 1/2" sheet of plywood won't increase the stiffness of the mounting unless it is fastened to the desk top in such a way as to be essentially part of the desk top. Gluing it down properly would do this. Then the amount of stiffness will be increased much more because the stifness goes up by the cube of the thickness. In other words, a benchtop twice as thick is 8 times as stiff. Eric
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wrote:

OTOH you may not notice the twist if the lathe sat flat on the tabletop without rocking before you attached it. I almost never turn a continuous cylinder from end to end between centers, because I buy shafting or ground drill rod the right size to fit bearings and only modify a short distance on the ends. You may be OK just bolting it down, using it and watching for issues to correct later, instead of waiting for a precision level.
A bigger problem than slight bed twist is that the cutting force deflects the unsupported right end of chucked work. If I drill it for a supporting live center in the tailstock the space for carriage travel between the spinning chuck and the tailstock base can become tight. My lathe came from a trade school and bears multiple scars where inattentive students ran the carriage into the chuck jaws. That alone is a good reason to buy (or make) a micrometer carriage stop. http://neme-s.org/SB_Carriage_Stop/making_replacement_carriage_stop.htm
They don't really need the micrometer dial, a simple threaded rod with a finger knob would do because you can set it to the tool bit position on the work.
I was advised to buy at least one chuck small enough that the carriage can pass under it, unless the jaws are cranked way out. I have several now and they are the chucks I use most often. -jsw
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Wise words indeed.
bob prohaska
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wrote:

http://www.cartertools.com/jose06.html
-jsw
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bob prohaska wrote:

Or grab some stuff you have around the shop and try this method...

https://www.youtube.com/watch?v=2qIdsnl5vpg

--
Steve W.

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snipped-for-privacy@whidbey.com wrote:

This I absolutely agree with.

Thus my question: "Why fasten it down?" The only reason I can think of is to help disspate acoustic energy generated by tool chatter, in an effort to reduce ringing in the bed.

Even then, can the benchtop contribute discernibly to the stiffness of the cast-iron lathe bed? It looks as if the stiffness of iron is about ten times the stiffness of wood. The table is 2.5" thick at most, the lathe bed is nearly a box beam 4 by 4 inches, not counting the ways.
There seems to be an inherent Catch-22: If the wood is thick enough to contribute to stiffness, its warpage will contribute to distortion.
Thanks for your thoughts!
bob prohaska
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On Tue, 8 Aug 2017 18:25:17 -0000 (UTC), bob prohaska

The bed is not a box beam. It's more like two narrow I-beams, and not very stiff ones, connected only at the ends of the bed. Tying it together by fastening it to a plane surface at the bottom stiffens it up quite a bit.
--
Ed Huntress

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On Tue, 8 Aug 2017 00:12:50 -0000 (UTC), bob prohaska

Machine tools are normally "leveled" which doesn't always mean "level" :-) In the case of a lathe it would mean that there was no twist in the bed and while it can be leveled with a precision level (.0001" in 1 foot accuracy) it can also be done by cut and try. Or, if you have a "test bar", i.e. a bar the length between centers on your lathe with centers drilled in it that is straight and concentric you can simply mount it between centers and hold a dial indicator in the tool post and crank the carriage down the length of the bar. There should be no deviation.
Most people don't have a test bar so the usual method is to cut a piece of bar stock the length between centers, drill center holes in it, mount it between centers and take a cut the full length of the bar. Mike the bar, it should be the same diameter from end to end.... assuming that your tail stock is properly aligned, of course.
But to be honest, most "home craftsmen" usually spend their time frigging about down at the head stock end of the bed and usually don't turn things the maximum length possible. A rifle barrel, for example :-)
So depending on your use "leveling" may not be a critical item on the agenda :-(
--
Cheers,

Schweik
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Seems unlikely, this desk was sitting on the curb with a "free" note on it. I did see one listing at an auction site with a closing bid of $20. It's much nicer in joinery and materials than one finds at Ikea, but it's not fine furniture by any stretch. I am hesitant to wantonly vandalize it, which is part of my reluctance to go drilling holes in the top. It appears to be an unadorned clerk's desk, small, plain and simple.
Thanks for writing,
bob prohaska
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I'd be thrilled to be that lucky 8-) This desk was made in Chicago by the Commercial Furniture Company. It seems to be of northern softwood, not even hardwood. However, it _is_ wood, not composite, and the joinery is nice (dovetailed drawers, mortise and tenon legs).

Interesting site. The prices are breathtaking ($1500 for a tanker desk???). The wood pedestal desks are much finer than mine. Still, I won't go hacking and drilling on it just yet..
Thanks for writing!
bob prohaska

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The most critical concern is not twisting the bed, normally addressed by leveling both ends crosswise. The Heavy 10 can be on a sheet metal stand because it has a pivot under the tailstock that lets the bed center itself, but after it does the locking screws have to run in to hold it there against the cutting force that pushes the carriage down.
Find the manual for the 10k and see what it says about mounting requirements.
Sometimes auto parts stores sell large oil drip pans. I was given a used (flattened) Auto Trend Products pan almost 4' long. -jsw
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On Tue, 8 Aug 2017 12:46:35 -0400, "Jim Wilkins"

I have a 10L on a steel base, and that has the adjustment you're talking about. But the 9" SB's were made mostly as bench-top lathes, expected to be mounted on wooden benches.
I have a precision level that I use to check mine whenever I move it. I've had to adjust it whenever I do so, which is about once every 10 years. <g>
However, I think that a 10K, which really is a 9" SB with a built-in riser on the head and tailstock, should work out well for hobby use on a sturdy wooden bench. Gluing another layer on top, as someone suggested, should help. Plywood is a lot more stable in changing humidity than solid wood.
--
Ed Huntress

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That's a nice feature, which mine does not have. Perhaps it's too old, IIRC it's mid-50's.
bob
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That seems to imply the lathe is straighter than the table, at least to start with. Makes sense. Now, will the table stay the same? My guess is "no".

The usual, "Bolt it down securely", though they don't say anything about leveling or checking for twist. It's an army manual, probably intended for field use. The 10k is relatively lightweight, unlike the heavy 10, and seems intended for repair rather than production.

That's a good idea, I'll keep an eye peeled.
Thank you!
bob prohaska

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wrote:

I think the Heavy 10 was more of a tool/instrument maker's machine, wherever his shop was, not meant for serious production down on the solid factory floor. It goes well with my 700 Lb Clausing mill of the same age, another small shop machine that can be carried up stairs in pieces. In the 1970's my stuff would have made a great inventor's model shop
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