PDA

View Full Version : Tell me about.......wood lathe benches



Ringo
06-19-2019, 08:44 PM
In the old school lathe books, like Atlas/Craftsman, South Bend, Logan, etc. they will tell you to construct a wood bench, so an so thick and so on.
RB211 just posted a video about new technology lead screw from a guy, and his lathe was on a wood bench.
I have built several wood boats, all have been set up on wood foundation for levelling the frames an components. You can pull strings for straight lines, and level everything, +/- 1/16"
Come back next day and it is off by 1/8"
then it rains and it may or may not be on. the wood foundation is moving with the weather. we all know wood shrinks/contracts with moisture.
I already know wood moves a lot with weather, I already know a lathe has to be level.
So, then, how do you keep a lathe level if you mount it on a wood bench?

RB211
06-19-2019, 09:53 PM
In the old school lathe books, like Atlas/Craftsman, South Bend, Logan, etc. they will tell you to construct a wood bench, so an so thick and so on.
RB211 just posted a video about new technology lead screw from a guy, and his lathe was on a wood bench.
I have built several wood boats, all have been set up on wood foundation for levelling the frames an components. You can pull strings for straight lines, and level everything, +/- 1/16"
Come back next day and it is off by 1/8"
then it rains and it may or may not be on. the wood foundation is moving with the weather. we all know wood shrinks/contracts with moisture.
I already know wood moves a lot with weather, I already know a lathe has to be level.
So, then, how do you keep a lathe level if you mount it on a wood bench?

For small bench lathes, like my 8", I have it sitting on a wood bench, but the lathe itself is bolted to a big piece of C channel to stabilize it. My bigger lathe has a 3/16" sheetmetal stand with cast iron level pads with big bolts for adjustment. Checked it one month later after leveling, and it hasn't moved.
99% of my work is near the chuck and it is hard to notice any twist in a lathe bed. If I was turning precision shafting and needing to hit numbers from one end to the other, it would be much more critical.

It seems that many of us, myself included develop OCD with this hobby. Today I was pricing out parts to make my VFD lathe mod even better with proper cables, more DIN terminals, grounding terminals, EFI filters, contactor for the coolant pump, etc. I don't have to do any of it, the lathe functions... But I want to... Something inside me wants it to be even better...

BCRider
06-19-2019, 10:16 PM
That's a VERY good question.

I also do a lot of wood working. And part of the reading for that is learning how to best deal with dimensional changes due to moisture changes. A wood bench CAN be a good thing if the wood is picked for the grain runs and then laminated such that it does most of the growth in one direction so it swells and shrinks but the top surface stays flat. Then just a slight torquing allowance for the lathe to let the bench top "slide" under the lathe can do the trick. Just bolting it to a top made from any old 2x12 is not going to do the lathe any favors if it has two mounting points.

These days there are other options for a wooden bench that can work better. Plywood can be surprisingly stable in dimensions over a pretty wide humidity range. Plywood will vary a little in thickness with humidity changes but almost nothing in length and width. Now we want both rigidity and mass for a bench top for a lathe. So there's much to be said for laminating a number of layers together with a good glue to achieve a nice thicker plank. And don't spare the layers. For something like a 10x22 lathe I'd say a minimum of two layers of 3/4" plywood would do if the support framing on the lower side is quite sturdy and has the major load bearing members closely framing the footprint of the lathe itself. Otherwise I'd want to see 4 layers or more under the lathe itself so the slab is more self supporting for the portion under the lathe.

But your suspicions that there are other better options is 110% right. Wood is not all that heavy. And a mark of any metal machine tool is that weight is a big advantage for aiding in resisting chatter. So a good size hunk of granite or concrete can be a much better option. Or taking a page from ship's machine shops where the lathe is mounted to a large section box beam of steel or iron and then set in a stand that allows the stand to flex in response to the deck twisting and bowing without transferring those loads to the floating beam and lathe. That large square or rectangular thick wall section joins both joins with the bed through the mounting pads to create a larger overall section that is massively more rigid and strong and heavier all at the same time. All good features for a metal lathe.

Some time back there was mention around here of a pamphlet given out to small metal machine shops all over the US on how to make big concrete lathe mounts so their small size hobby machines could do more and attain more than they could while mounted to a wood bench. No one seems to be able to find the pamphlet but lots of folks seem to recall the contents.

I know that the "big tin boxes" that came with my 12x36 lathe were WAY too short for me. I'd blocked the boxes up but it was never steady. And it was an issue. When I moved and setup the new shop I tossed the base boxes in the scrap metal bin (quite happily) and made construction block bases mortared together and mortared to the floor. The upper course and a half was filled with concrete over road base gravel filling the lower portion. 1/2" threaded rod was bent into "J" shapes and used as mounting studs which were set into concrete using the holes in the chip tray to locate the studs. And the lathe sat on jacking nuts so I could level and true the bed easily without needing shims.

Maybe not as perfect as it might be. But HO BOY! Did it ever make the lathe a MUCH better performer. Where I had to use back gear before for parting and chatter was never far away now I can use the lower direct speeds and the parting goes smoothly and silently. I can do heavier cuts than before without any risk of chatter.

Another member went ahead and made a poured concrete slab to use for his 10x22 or so and found similar gains in performance compared to his old wood bench.

Now if wood is used well it can be a decent bench. But I do feel that we can get better results without a whole lot of effort through using heavy steel (and lots of it) or by using concrete.

darryl
06-19-2019, 10:22 PM
You take advantage of proper construction methods where materials are selected for their properties. You don't start with fresh 2x4s and expect them to not warp or twist. Tops used to be pretty good if they were plywood, but the plywood of today is about as flat as the torso on Marilyn Monroe. There are better grades, and other materials which suit making a flat and stable top. You also treat both sides of a top the same, so if you epoxy the top you should also epoxy the bottom.

If your floor is prone to warping, then you might try to make the tailstock end of the top a bit of a floating fit on its legs at that end. If the lathe bed can be twisted by the top it's mounted to, then you have some degree of adjustment based on that- but if the bed is stronger than the top, then the top will twist as you try to adjust the twist out of the lathe bed. Then the stand might twist and perhaps one leg comes off the floor and just hovers there.

I would call this whole thing an inexact science, where many factors interact. If you really do have to account for the twisting that a floor can go through, but still need the bench top to be strong enough to 'pull' a lathe bed into alignment, then the construction of the top becomes the critical thing. If the floor can be considered stable enough, then the top can be kept rigid by way of legs mounted to both the top and the floor. There would be some adjustability for the length of the legs- and if wooden legs are used, they would tend to all grow or shrink at the same time, so little error would be introduced.

When I made my wooden bench for the lathe, I used old 2x4s and plywood. Being seasoned for a long time, they are already much more stable in dimensions and twist, and harder. And of course I selected the materials for straightness before cutting anything.

When I made the wooden bench for the mill- same thing. I picked up some 2x6s that had been sitting in a neat pile inside for some years and made it from those. And I only used the straight ones with no warping and no cracks.

darryl
06-19-2019, 10:37 PM
I've seen where some of the precision machines used in industry are mounted to their own concrete floor castings, which are nested into a hole cut in the floor. These castings are usually very thick and heavily reinforced, and will stay 'planar' because they're not rigidly connected to the building surrounding them. Still subject to error as the concrete continues to cure, but this is a factor that lessens with age.

How good does it need to be? A well constructed wooden stand using proper materials is probably as good as most of us would ever need.

J Tiers
06-19-2019, 11:13 PM
I have been considering a concrete slab as the bench top. But they are tearing up streets around here like no tomorrow, and that has me considering just a piece of 3/4" or 1" steel as the bench top, since I keep having to drive over the steel slabs they lay down over cuts in the street. Holds up cars and trucks, ought to be OK for a lathe... and add rigidity.

The steel would expand more similarly to the CI bed, I doubt not (need to look it up) and the concrete continues to move around for months.... steel may be better.

QSIMDO
06-19-2019, 11:22 PM
If you want to construct a truly straight and sturdy bench use the "torsion box" method.
I have a 4'x8' assembly table made with this design and it does NOT move!

J Tiers
06-19-2019, 11:44 PM
The plan with the plate is for the plate and the bed to form a partial torsion box..... I know you mean an actual box, with ends, which would be extremely stiff. But I already have the bench. Might allow 3" for concrete..... no n=more thickness than that.

Part of the plan is added mass.... to change the resonance.

BCRider
06-20-2019, 01:16 AM
A flat plate can twist fairly easily for the amount of mass and material. On the other hand a piece of thick wall rectangular tubing would act a lot like a torsion box. And if the ends were closed off with welded on caps to form a true steel torsion box it could make for a really good lathe bed. Lb for lb a lot better than the same weight of plate.

RB211
06-20-2019, 01:18 AM
A flat plate can twist fairly easily for the amount of mass and material. On the other hand a piece of thick wall rectangular tubing would act a lot like a torsion box. And if the ends were closed off with welded on caps to form a true steel torsion box it could make for a really good lathe bed. Lb for lb a lot better than the same weight of plate.

You could fill that box with concrete too.

mihit
06-20-2019, 03:13 AM
I have just got together a bench for the 12x37. It's on them flimsy metal cabinets at the moment, and the previous owner put the leveling feet at the bottom :rolleyes:.
The top is two 9x4" planks of about 20 year old heart totara (well seasoned you might say. very stable), laminated together (for 18x4) with a 1/2" steel plate rebated into it. And the levelling will be done at the bed :)

Lathes do not need to be level, just not twisted.

My other lathes are either VF heavy cast iron on VF heavy cast iron stands, or benchtop.

darryl
06-20-2019, 03:34 AM
And there you have it. A three sided steel box of sufficient length, with a designed in array of attachment points, pass-throughs in both x and y directions for wiring and cable or hose, and potentially other internal bracing rods. The end plates could be of any shape that would facilitate mounting legs, motors, etc. A suitable filler completes the basic structure of this top.

Sounds like a killer idea to me- definitely costing more in steel than if wood, but a much superior lathe stand.

Ringo
06-20-2019, 07:15 AM
Someone mentioned granite for added weight.
What if you built a heavy, stout, plywood cabinet box, topped it with granite similar to your kitchen countertops, mount the lathe on that???

J Tiers
06-20-2019, 08:39 AM
A flat plate can twist fairly easily for the amount of mass and material. On the other hand a piece of thick wall rectangular tubing would act a lot like a torsion box. And if the ends were closed off with welded on caps to form a true steel torsion box it could make for a really good lathe bed. Lb for lb a lot better than the same weight of plate.

Of course it can.... but it will twist a lot less than a couple sheets of thick plywood, and weighs more.

The torsion box does at least one thing very well. The question is whether or not that is THE thing that is needed..... Is the issue with the lathe really mainly that it will twist the mounting base in that way? I think that is a bit questionable.

The lathe bed can flex up and down, it can flex side to side, and it can twist. I am by no means sure that twisting is the main issue for most machines, which do not have the power applied to the spindle to do a lot of twisting, especially when bolted to almost any form of support.

Twisting would be applied by the cutting tool to the bed, somewhere toward the middle away from supports, usually. A fair bit of the force is down, flexing the bed. and the "twisting" is due to the distance the cutting tool is away from the center of the bed. The force is limited by the strength of the work against the "chisel action" of the tool cutting it, as well as the strength of the tool itself. The twisting is applied through the bed to the ends, and from the ends down at a mechanical disadvantage to the base. The mechanical disadvantage depends on the height of the "feet".

The base is therefore not being "twisted" on its axis, against which it may not be strong, but has a combination of shear in its plane, as well as some twisting. The base is likely to be strong against the shearing action (tryin g to move the HS end CCW, and the TS end CW.). So the base may be pretty good against the amount of twisting it is likely to get.

The bed as a beam, is, in most cases, supported essentially with "hinges" at the ends, as if it were laid on loose supports. The wood base is not very good support for the "feet". Converting that as much as possible to a "rigid support" at each end would seem to have more potential in preventing the bed from flexing up and down, which seems to be a main issue of rigidity.

Yes, I know about (and own one of) the lathes that have 3 point support. They normally have very heavy beds compared to the forces applied, and so can be left to support themselves against the flexing and twisting.

JoeLee
06-20-2019, 08:54 AM
I've seen where some of the precision machines used in industry are mounted to their own concrete floor castings, which are nested into a hole cut in the floor. These castings are usually very thick and heavily reinforced, and will stay 'planar' because they're not rigidly connected to the building surrounding them. Still subject to error as the concrete continues to cure, but this is a factor that lessens with age.

How good does it need to be? A well constructed wooden stand using proper materials is probably as good as most of us would ever need.Darryl, you post brings back memories. When I was a kid there were a lot of factories around my area. I knew a lot of older guys that were machinists, and when they retired they some how ended up with a lathe.
Most machines that I remember were small South Bends. Every one I ever saw had a bench made out of 2" x 6" or 8". Everyone had their own design, basically.
The reason was that in the factories these machines were mounted on big I beam frames that were sitting on concrete piers. There were rows of them, all bolted down to the beams.
So bottom line is they couldn't take the beams with them so they had to make their own stand, or I should say bench.

They did have stands for those machines.
http://www.lathes.co.uk/southbend/img63.gif


JL................

fjk
06-20-2019, 10:23 AM
I have a rikon midi lathe. Itís mounted on a wood cart. The frame is made from Wood L girders that I made from 1x2 and 1x4 boards. Top is 3/4Ē plywood. It works fine for me.

In this picture you can see the cart under construction (the lathe is on the floor behind the cart). The completed blue&white cart farther back is the same design, on which Iíve mounted a mitre box and mitre trimmer:
https://www.dropbox.com/s/rrkwo08m2lancxp/IMG_0983.JPG?dl=0

Frank

BCRider
06-20-2019, 12:48 PM
Someone mentioned granite for added weight.
What if you built a heavy, stout, plywood cabinet box, topped it with granite similar to your kitchen countertops, mount the lathe on that???

The granite in the case of the person in a post some time back that did that was three times thicker than a typical countertop slab. It isn't just the weight. It's the rigidity. And that starts with a thicker slab. Something more like the much thicker stock used for making grave markers. If you don't need a massive size slab of the stuff go around to a place nearby that does memorial slabs and see what it would cost for a piece that would be suitable. For a smaller machine I suspect it would be a superb mount.

But a lot more expensive than pouring your own concrete. And you'd need a darn good hoist to move it and set it in place. There is a monument making service near me and I picked up a scrap to use with my leather working. It's only 8x16x3 inches and it's already 39 lbs (I measured it). So you can do the math to figure out what such a slab to go under your lathe would weigh.

Jerry, there's much in your last post I totally agree with. A thick pad or beam to mount the lathe onto IS one option. But very stout or well designed end stands can also do the job by connecting the lathe to the floor in a proper and effective manner. The filled construction block pedestals I made up are still working like a charm. And at least 20 times better than the tin boxes that came with the lathe.

There is another man made option these days that involves wood. The Parallam and Microlam products from Weyerhaeuser are much more stable and a lot more dense than the same woods. A suitable piece of Parallam beam used as the top for a wooden lathe bench should be just about as good as you could ask for in terms of a wooden bench. It's stiff, strong, heavy and thick. But not as heavy as granite, concrete or a heavy wall steel box as the mounting beam. Which would make it more attractive to those that need to consider how to move the machine from time to time.

And if the base for the bench is similarly solidly built, given sturdy shelves and then loaded down with heavy lathe tooling the effects of the mass will telegraph through the legs or sides and back up to the top and through that to the machine to aid with damping the machine to resist chatter. That can make up for the lack of mass in the bench itself.

mattthemuppet
06-20-2019, 01:19 PM
I think it's a valid concern, but I don't think it's a major one. If you construct the bench to be robust enough to use as you'd want to use it (mounting a heavy machine tool, whaling on stuff in a vise, lifting heavy stuff onto it to work on etc) then most likely it'll be robust enough not to cause major issues at the level of size and precision most people work at. If you want to minimise movement, lots of cross bracing, stout uprights and a multi layer top (with grains running in different directions) should get you a long way.

Doozer
06-20-2019, 01:34 PM
A wood lathe bench is a huge compromise.
Some men are willing to live with the drawbacks
while others are ignorant to these facts.
Perhaps you fit in somewhere in the middle.

-Dozoer

Mcgyver
06-20-2019, 01:34 PM
I already know wood moves a lot with weather, I already know a lathe has to be level.
So, then, how do you keep a lathe level if you mount it on a wood bench?

Basically, you don't. You get it as good as you can get, the wood is all sealed, so is hopefully as stable as it can be and probably when that stuff was written no one had of heard plastic wood (gag). It was made of maple or oak of something sturdy.

End of the day, wood moves, but so does your concrete slab. You work to certain tolerance then its grinding territory (or lapping). You level the lathe, cross your fingers and possibly tweak it when needed but all in the knowledge that most work only requires so much accuracy over so long a length. Some of the best lathes, a toolroom lathe like a monarch 10ee, and a lot of grinders rest on 3 points because the makers knew slabs move. So do some bench lathes, i.e. the Schaublin 70. That's the bench lathe rolls royce alternative: engineer some ribbed sturdy structure, possible filled with epoxy granite to damp vibration, scrape it to fit the lathe and have it rest on three points. Never to worry about level again.

J Tiers
06-20-2019, 01:46 PM
BC....

What is needed is whatever is good enough. I suppose there may be a dozen or so fairly normal ways to do the bench or benchtop, that would be much better than the lathe that is put on top of it as far as flexing, twisting, or whatever. I suspect that the cheapest and most easily done version is probably concrete, but heay plate would be good, and even well braced wood.

mattthemuppet
06-20-2019, 02:06 PM
A wood lathe bench is a huge compromise.
Some men are willing to live with the drawbacks
while others are ignorant to these facts.
Perhaps you fit in somewhere in the middle.

-Dozoer

everything in the realm of the hobby shop is a compromise, at least for most people. I'd love a bigger, sturdier lathe on a bigger, sturdier bench, but I have what I have and that works pretty well for me. If I had a longer lathe and was doing longer work, I'd pay much more attention to any effect my wooden bench moving around had on its accuracy, but I don't, so I don't. Last night was in part spent making some jewelry, including a couple of studs from stainless with 0.7mmx10mm shafts. I really wasn't worried about lathe bed twist :)

that said, my 6x18 is bolted to a base of 3/4" 5 core ply screwed to 2x4s and that base is screwed to a bench top of 3/4" 5 core ply and 3/4" mdf (or whatever they make treadmill bases from). I think that'll be fairly rigid and hopefully any movement in one direction will be cancelled out or resisted by other parts of the structure.

BCRider
06-20-2019, 02:48 PM
BC....

What is needed is whatever is good enough. I suppose there may be a dozen or so fairly normal ways to do the bench or benchtop, that would be much better than the lathe that is put on top of it as far as flexing, twisting, or whatever. I suspect that the cheapest and most easily done version is probably concrete, but heay plate would be good, and even well braced wood.

Very true. Or we make allowances and work around the issues. I know that I worked around the horrid ability of the original tin boxes for WAY too many years. But it was good enough for a lot of work. Including making MT3 tapers. I'm more than ecstatic with the performance improvement of my new pedestals though. But not everyone is willing to take on a solution involving concrete or very heavy large size rectangular steel sections. And that's fine.

Knowing how much I gained from a solid mount for the lathe is why I'm tossing out ideas for discussion for possible wood options that center around heavy and bulky options that might well offer a more rigid platform with some of the abilities of cast iron, concrete, granite or large heavy steel sections. Hence the 4 or more laminations of 3/4 fir plywood or the length of large section Parllam beam held up by sturdy legs and shelves that can be loaded down with lots of heavy stuff. Smaller lathes could likely make do with a bit less. But I still like the engineered wood options over sawn lumber for the stability and greater stiffness that they offer over plain wood.

Ringo
06-20-2019, 04:06 PM
I started this because I have to re-arrange my garage due to acquiring more machines, and space to put them, this means new work benches.
Besides, the Logan, Atlas, South Bend lathe books say get a level accurate to .0000x; level the lathe to .00000x accuracy...........then set it on a wood bench, Huh?
What about a piece of steel box rectangle, 2x10x .188wall? just let that be the lathe support.

JCByrd24
06-20-2019, 04:23 PM
There are two issues I've found with my 12x24 import on it's factory stand(s) and my be similar for lighter lathes:

1) As BC has mentioned is rigidity and the ability to resist chatter instead of ringing like a bell on heavier cuts.

2) Is the inability to untwist the lathe if necessary, which it is in my case. I'm not sure how it get twisted in the first place, it's a pretty stout bed compared to the stands, but I think this is relatively common.

Both are issues that BCs concrete design overcomes, and which I want to overcome with my next stand. As has been mentioned, it's not really the level that is critical, it's the bed twist. If the lathe is perfectly straight and rigid enough on it's own then whatever it bolts to only has to not twist it. But if like me you lathe is pretty stout and has a little twist, you need something you can pull against to straighten it out. Similarly if the lathe is flexible enough to conform to whatever it happens to be bolted to, you want that surface both straight and stout, or at least stout so you can shim it straight. A 2x10x.188 wall tube would likely be a very good start for a flexible lathe.

lbender
06-20-2019, 04:52 PM
So, then, how do you keep a lathe level if you mount it on a wood bench?
Yes, wood moves with humidity, but the composites like particle board are saturated with glue to the point of not moving much.
A torsion box with bracing glued and screwed together with enough weight in the drawers make a pretty stable mount.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=5507&d=1561063602

BCRider
06-20-2019, 07:06 PM
Ringo, for a small'ish lathe the 2x10 part sounds pretty good. But I'm not smiling over the 3/16 wall thickness. If the foot pads on your lathe will fit within the confines of a 10 inch wide face and you like this idea of using a big steel structural section then I'd suggest more like a 5/16 to 3/8 thick wall.

A four ft length of such tubing won't be cheap though. So plan on a bit of sticker shock. I bought some tubing that was about 5x10 or 6x10 or something like that and welded up a mail box for my club's guest pass payment envelopes. It was either 1/4 or 3/16 wall and it cost $180 just for the 2ft of tube. You could build a REALLY nice wood product based bench for that much. Or do a wood bench with a plywood basin top and pour in a 3 to 4 inch concrete fill with mounting studs set in place using a template to hold them in place accurately. If your chip pan is like mine it could be your template. Again even the $180 just for the heavy structural rectangular section could cover off the cost of some pretty good wood, concrete and a couple of pieces of suitable threaded rod.

Or consider a semi permanent option like I did. If you're 110% certain where you want the lathe to go then do a bit of brick laying with mortar and construction blocks. And then like I did set the mounting studs in concrete in the top course and a bit. Fill the lower cavities with a gravel and sand mixture. It's semi permanent because it's really not that bad to break it up later on. Just the top pieces will prove rather heavy. But the bottom part will come loose pretty easily and then just shovel and sweep it all away. But that's something you only want to do ONE time... :D So if you go that route be sure it is where you want it to be. And plan on the idea that any big maintenance work might well require lifting the lathe off this semi permanent stand.

One guy here doing his own stand at the same time for a smaller lathe used my construction block pedestals but then formed up and made a concrete "top" that spanned the two pedestals. That seemed like a pretty sweet way to go for a smaller size semi permanent option too.

Fir plywood is a big step up from SPF plywood that is more commonly found. If you have access to some woodworking machines you might consider that overbuilt laminated plywood lathe bench idea. It's sort of like a torsion box but you glue and screw full layers together to form a solid torsion box. I don't recall the type or size of your lathe. But I could see a South Bend SB9 perched pretty happily on four or maybe 5 layers of 3/4 fir plywood and some 3/8 foot spreader plates. The slab like that would be nice and stout and heavy enough to aid with damping the operatic tendencies of the machine. That much is certainly not needed to simply hold the lathe up. The idea is to create a structural addition to the lathe so there's something to lean against for aligning the bed. And add a good damping mass in direct contact.

And as mentioned by the others level is just one example of aligned. It's more important for the lathe to be true. It could be sitting at some odd angles and still be true and turn really good parts... but it's not nice if all the stuff keeps falling off. I roughly levels mine with a 24" builder's level. Then I started working with a test bar with skim cuts and a good mic and a good dial gauge to check for and tweak the bend twist and arc. Mostly I suspect that we are actually bringing the lathe to it's original natural no stress "relaxed" alignment. But if some small amount of twist needs to be added a good solid and rigid base member can be the good stable reference to lean on to tweak the bed back to good alignment.

Ringo
06-20-2019, 07:16 PM
I'll probably go the plywood route.
Even if I did get a section of steel rectangle tubing, it would not be sitting flush with the bench, or else custom fab it to be flush.
I got enough wood working tools to do the trick in wood, how about MDF? that would be stable wouldn't it?

Doozer
06-20-2019, 08:02 PM
..... the Logan, Atlas, South Bend lathe books say get a level accurate to .0000x; level the lathe to .00000x accuracy...........then set it on a wood bench...

Stop believing what books say.
Believe only that the person who wrote the book believed it.
Forming your own opinions based on facts is a big step forward
towards enlightenment.

-Doozer

J Tiers
06-20-2019, 08:39 PM
Ringo, for a small'ish lathe the 2x10 part sounds pretty good. But I'm not smiling over the 3/16 wall thickness. If the foot pads on your lathe will fit within the confines of a 10 inch wide face and you like this idea of using a big steel structural section then I'd suggest more like a 5/16 to 3/8 thick wall.
......

Concur.... remember that you also need to support the feet against the bed bending up and down.... that 0.188 thickness is hardly over sheet metal and is not very stiff as a "mounting plate".

OK for small lathe, 7 x 12, etc. not so good for Logan sized machines.

Ringo
06-20-2019, 08:54 PM
my Logan is 9x17 v-belt

Planeman41
06-20-2019, 09:15 PM
if you want to go with wood, I recommend using thick oriented strand board (OSB) available at Lowe's, Home Depot, etc. This is the plywood alternative with the large flakes of wood glued together. It is the most stable of all of the wood products as the wood flakes are oriented randomly. Top this with a sheet metal top or Formica. You can also buy this as a top for a bench lathe already assembled as counter tops. Also, do as I did and only bolt the tailstock end with with one bolt. Drop another bolt in the other corner for looks, but leave off the nut. This helps the lathe resist any twist that might settle into the wood top. Steel lathe beds are tough and rigid and don't need bolts at the four corners. But they can twist a very few thousandths if enough force is applied. The "three point" bolting avoids this.

Tom S
06-20-2019, 09:59 PM
if you want to go with wood, I recommend using thick oriented strand board (OSB) available at Lowe's, Home Depot, etc. This is the plywood alternative with the large flakes of wood glued together. It is the most stable of all of the wood products as the wood flakes are oriented randomly. Top this with a sheet metal top or Formica. You can also buy this as a top for a bench lathe already assembled as counter tops. Also, do as I did and only bolt the tailstock end with with one bolt. Drop another bolt in the other corner for looks, but leave off the nut. This helps the lathe resist any twist that might settle into the wood top. Steel lathe beds are tough and rigid and don't need bolts at the four corners. But they can twist a very few thousandths if enough force is applied. The "three point" bolting avoids this.

I would argue that one with you, OSB is probably the last product I would go with. It's one step above chewed up kleenex formed into a board, and is awful with moisture due to the excessive end grain. Flexes when you look at it wrong.

With wood you will get movement, you need to figure out how to deal with it. Lateral movement either front-to-back or along the length will not have much of an effect on level, while cupping of the top in either direction will cause twist in the lathe bed. So you need to design to promote lateral movement and eliminate cupping.

First choice for me would be 8/4 hard maple (because Canada, you Americans can go with oak), quartersawn. All surfaces (including oversized holes drilled for mounting the lathe) sealed up Danish Oil to both prevent moisture from penetrating and for oil resistance. All holes would be drilled oversized with bolts running through the top and secured from underneath with nuts and washers. This would be to allow the mounting points to slide with lateral movement, preventing the bed from being put in tension or compression. Flanged rubber bushing would have the same effect.

Second choice would be 1" MDF with laminate on the top and bottom and all edges. The trick to this one would be to support the top solidly with a sub-frame since the MDF is less stiff than a product with grain, but to also allow the top to float on the sub-frame to so any movement in the sub-frame is not transmitted to the top. My concern with this one would be seal up the mounting holes so that you can't get any moisture working it's way down into the MDF, which would cause swelling. The MDF will be very even with it's movement, so as long as you don't get localized water penetration and swelling it should be consistent.

J Tiers
06-20-2019, 10:08 PM
if you want to go with wood, I recommend using thick oriented strand board (OSB) available at Lowe's, Home Depot, etc. This is the plywood alternative with the large flakes of wood glued together. It is the most stable of all of the wood products as the wood flakes are oriented randomly. Top this with a sheet metal top or Formica. You can also buy this as a top for a bench lathe already assembled as counter tops. Also, do as I did and only bolt the tailstock end with with one bolt. Drop another bolt in the other corner for looks, but leave off the nut. This helps the lathe resist any twist that might settle into the wood top. Steel lathe beds are tough and rigid and don't need bolts at the four corners. But they can twist a very few thousandths if enough force is applied. The "three point" bolting avoids this.

Not sure I am on board with the "3 point mounting"..... I have two problems with it, maybe you have already solved them?

1) The single bolt is off center, typically, so it applies an off-center clamping. That is more likely to DISTORT the bed than just leaving it loose, no bolts at all. Most lathe "feet" have a hole in the front side and one on the back side.

2) Smaller lathes in the lower cost categories have relatively limber and flexible cast iron beds... thinner and not very wide (there are exceptions, like Logan, but even Logan is flexible). Going with legitimate 3 point with the flexible bed just puts you basically back to not even bothering to bolt it down.

If you insist on a 3 point mount, then bolt the feet to plates.... one is fastened to the stand by the usual bolts, the other is balanced on a piece of hardened rod in the middle, and only loosely bolted if at all (bolt through a loose hole in the rod, possibly). But I do not recommend that.

Also I've used a lot of OSB... Plywood every time, Baltic birch if you can get it. It is oriented two ways, but many layers, and is quite stable as wood products go.

OSB has a layer of N-S chips, a big layer of E-W chips, and another layer of N-S chips. It is marginally better than regular chipboard, and just about as strong as papier-mache done with glue. A hammer puts a hole in it easily.

I don't like MDF... it is all sorts of reactive, basically plastic with a lot of wood filler, only not quite enough plastic to be strong. bends, takes a set, thermally unstable. What's to like?

Ringo
06-20-2019, 10:16 PM
I think the 3 point mount would work if applied to something like the 2x10x36" box tubing. mount the tubing 3-point, then set lathe on top of that. you still have to level lathe though

Tom S
06-20-2019, 10:26 PM
The thing to like about MDF is the lack of grain and density. When used properly any movement will be linear, no cupping or twisting. You get warping when it’s not used properly - not supported well enough or only laminated on one side. Laminate does not expand or contract near as much as the MDF, so if you only apply it to one side of the sheer you get warping due to uneven stress. If you apply it to both sides of the sheet you balance out those stresses and make a very strong composite panel. Plus the laminate provides impact and abrasion resistance to protect the MDF core. The density of the MDF core will help with deadening any harmonics or vibrations.

JCByrd24
06-21-2019, 07:43 AM
MDF isn't bad in terms of stability but it's a noodle over time. My workbench is 2 layers and has sagged some basically under its own weight in the middle of a 2x4 frame the is only 2 feet span. Plywood and OSB don't do this, or they couldn't be used in floors on 2' centers. If using MDF you need to build a torsion box. A bonus would be it's freaking heavy. I'd agree with Tom S, OSB would be my absolute last choice. You can't fasten into the edges and I don't think it'd glue up well or straight in layers. There are really only a couple of choices that incorporate wood in my mind:

1) Torsion box with birch or other good plywood or MDF

2) Chunk of glulam or other engineered beam

3) Hardwood butcherblock

All need a decent sub-base as well.

BCRider
06-21-2019, 12:02 PM
I think the 3 point mount would work if applied to something like the 2x10x36" box tubing. mount the tubing 3-point, then set lathe on top of that. you still have to level lathe though

That's basically what the ship board lathes do. The deck is not solid but instead waves around, humps, twists and shudders. A ship is flexible after all. So they fix the lathe to a big solid structural member then float it on a three point mount in the bench's support frame. The lathe then being "trued" as opposed to "leveled".

Used with a solid enough block of the stuff MDF could be used. It's got good hardness and is very good at damping vibration. Hence why it's a favored material for speaker boxes. But I have found that when laid flat and under load the darn stuff does "flow" and take on a bend over some years. So it would need to be a pretty thickly laminated to a sizable block for supporting the lathe. Perhaps take advantage of the vibration absorbing aspect by using top and bottom layers of fir or baltic birch plywood with MDF "filler layers" between?

And it DOES love moisture and humidity. So giving it a moisture retarding finish, particularly around the edges, is important.

If building a longer work bench which will be used for bench tasks and also to hold the lathe I'd further suggest that the section with the lathe be given its own middle legs. So a 6 legged bench. For a good sturdy top that resists sounding and acting like a drum skin when you thump something on it I'd really suggest and can recommend the two layers of FIR plywood glued and screwed together. When I did mine I essentially "sewed" the layers together with drywall screws used in a 6 x 6 inch pattern. And regular wood glue was also used between the layers. It's a lot of pre-drilling to get it ready and a lot of screwing to get it done but for something that large there really isn't any good way to clamp it together other than bazillions of small screws.

For a longer combo lathe and work bench with the lathe at one end that portion would get the extra "added bulk" layers of MDF. Likely added below. But don't be reluctant to add layers above the normal top as well to get the lathe and controls up to where you don't need to bend over to use it. In my case the main apron controls are up and pretty much centered at my belly button height. The carriage wheel being a little lower and the cross slide wheel being a bit higher. It also puts the work up where it's easy to see. For something like a mini lathe the two layers of fir ply for the main top with two more added between the four legs that bound the lathe area should provide a truly amazing mounting area. That's 3 inches of plywood. And the thick plywood does not mean you can skimp on the supportive framing. You're going to be pounding on stuff on this bench. Don't skimp on the supportive lower framing. We're trying to use wood as a substitute for iron, steel or concrete here after all.

For my fixed in place bench I opted for a lower frame with drawer boxes on top of the framing. The reasoning being that the truly heavy stuff could be put into plastic totes or wood boxes with casters. These acting like drawers themselves in the lower area. And we DO want lots of storage, right? The section built in this way is shown on the lower left portion of the work bench.

http://bbs.homeshopmachinist.net/attachment.php?attachmentid=3596&d=1537320554

In my case the units are fixed to the wall. But something similar that has multiple legs of 2x6's with drawer units between them to act as the stiffening framing could be done as a self standing bench.

I'm tossing out a lot of options for you to consider. And your own situation will certainly play a big part in the best solution to suit your needs and future plans. Me? I'm not going anywhere until I move to the place where they strain my Pablum for me. This IS my last big shop. The next one will likely be a desk in the spare bedroom of the retirement home apartment if I have one at all. So in my case built ins worked well for me.

BCRider
06-21-2019, 12:12 PM
MDF isn't bad in terms of stability but it's a noodle over time. My workbench is 2 layers and has sagged some basically under its own weight in the middle of a 2x4 frame the is only 2 feet span......

I had exactly the same experience as JCB. It seems to "flow" when under a load like this. The bench I did also had a wood supportive frame. But it still sagged a surprising amount over the years.

But as a filler between top and bottom layers of good tensile and compressive stable material like good fir or baltic birch plywood I think it could be a truly aces combination. The block would form a strong, solid and heavy torsion box structure.

MDF is even sensitive to how we glue the stuff. These days I'd choose to use polyurethane glue instead of regular carpenter's glue for making up the laminated block that we'd use for the lathe bench. Instead of adding moisture it uses some of the moisture already in the material. And while not cheap it's a lot less expensive than using epoxy.

Mcgyver
06-21-2019, 12:38 PM
I think the 3 point mount would work if applied to something like the 2x10x36" box tubing. mount the tubing 3-point, then set lathe on top of that. you still have to level lathe though

A big piece of hss would be good. three point it to the bench. You want to mount the lathe to the HSS in such a fashion that bolting it home imparts no twist. you could do that by scraping a pad welded to the HSS to the bottom of the lathe or use something like mogilice - put the bed on, get it dead level with shims, fill the gap with moglice, let cure and bolt it home.

I still there's missed opportunity in not filling that HSS with epoxy granite, and what the heck, while you've got the welder out turn it into a chip/coolant tray as well

BCRider
06-21-2019, 01:35 PM
A big piece of hss would be good. three point it to the bench. You want to mount the lathe to the HSS in such a fashion that bolting it home imparts no twist. you could do that by scraping a pad welded to the HSS to the bottom of the lathe or use something like mogilice - put the bed on, get it dead level with shims, fill the gap with moglice, let cure and bolt it home.

I still there's missed opportunity in not filling that HSS with epoxy granite, and what the heck, while you've got the welder out turn it into a chip/coolant tray as well

Wait a sec.... HSS? You have a tool bit that is that size? I think we need pictures.... :D

Setting the lathe in place on pads like that is fine provided the bed and feet are already in total alignment. And provided how we suspend the lathe does not also impart any flex to the bed. But you're assuming that the bed and feet are in alignment to a very good degree.

And then we have the rather clever arrangement of the South Bend SB9 lathes where there is a pivot and setting screws in the tail stock foot. And how they detail in the manual how to make and use a test bar that uses skim cuts and micrometer measurements to set the foot so there is no twist.

Mcgyver
06-21-2019, 01:57 PM
Wait a sec.... HSS? You have a tool bit that is that size? I think we need pictures.... :D



Hollow Structural Section.....


Setting the lathe in place on pads like that is fine provided the bed and feet are already in total alignment. And provided how we suspend the lathe does not also impart any flex to the bed. But you're assuming that the bed and feet are in alignment to a very good degree.


No. If the lathe feet are aligned with the the bed, you could scrape the pads into the exact same plane then attached the bed. But who go through the challenge of getting them into the same plane and take risk the two (foot bottom and bed) aren't aligned? I don't care if the pads on the hss or lathe bottom are in the same plane, all I care is that rigid mating of one to the other produces no twist in the bed. The process of scraping pads to the lathe is going involve checking that there is no twist via a level as would using a compound like moglice, again with things shimmed so there is no twist

All this idea is is a replciation of putting a rigid three point base on a lathe - something many manufacturers have done, usually with high end lathes...but I think it not a bad ideas as it wouldn't be very difficult and would add a lot of performance (including damping if you added epoxy granite)