Ideas sought for a bolted metal work/lathe bench

[Bill PhinnParticipant @billphinn90025]

Sonic Escape's recent metal workbench thread has persuaded me to ask for people's advice on how to go about creating a strong bolted metal bench around 150cm long, possibly to take a lathe weighing up to 250kg, that is dismantlable into manageable component parts and therefore doesn't involve welding, or, if it does, only a minimal amount.

I bought a bench of this kind recently, and though I was pleased with the work top, most of the rest is not impressive from a structural point of view: the box section wall thickness is too thin, for a start, the small amount of welding is terrible in places, and there is not nearly enough bracing, particularly if it is to be used, as intended, as a work bench.

Where would you start? What materials, and how would you go about bolting the pieces together? My only certainties are that box section should have a minimum wall thickness of 1/8", and steel angle be somewhat thicker.

[Bill PhinnParticipant @billphinn90025]

[Nigel Graham 2Participant @nigelgraham2]

I must admit I'd not like to put a tonne on that Sealy table even if evenly distributed, but it's probably stronger than it looks.

It is better used as an assembly or marking-out bench, or for electrical work, than for mounting a heavy machine-tool, though one of the "micro-lathes" would all right on it if with some ribs added below the machine's footprint to take much of the load.

A quarter-tonne lathe would be unfair because it is not evenly-distributed; though you could mount the lathe on two channel-steel longitudinal rails the full length of the table. Doing so would raise the machine's height above the floor so then you need think "ergonomics"!

SO…. keep that bench for the work it is fine for, and make the lathe bench, the right size – including height for you operating it.

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The wall thickness is too thin. Is it?

Look at how it "works".

It might be only 1mm in an item like that, but strength of a structure depends more on how the metal is used than how thick it is. Your bench members do not need be more than 1/8" (or more likely 3mm stock) thick: it is the area of steel, and its distribution with respect to the applied load and its direction, that do the work.

You can make a very substantial bench for your lathe from 40 X 40 or 50 X 50mm square, 2 or 3mm wall-thickness, box-section and 30 X 30 X 3mm angle. You want rigidity and vibration-damping as much as simple load-bearing.

You can bolt the box-sections together by overlapping, though that looks crude. Or use butt-joints with a heavy-duty steel angle-bracket on each side, bolted through with M10 bolts and "Nyloc" nuts. Brace the corners' outer faces with triangular 2mm – even 1mm – plate gussets bolted through with M8 bolts and "Nyloc" nuts.

If you put one each side of the box-section, those 1mm thick galvanised triangles sold as building components would probably be sufficiently strong corner braces, but their holes might not open safely to accommodate even M8 fastenings so would need M6. They are not the primary joining-parts, nor would they take much lateral load, but used judiciously they act in tension.

I have used heavy-duty galvanised steel L-brackets and those triangles, from e.g. 'Toolstation' for such engineering in metal and wood. They are building not mechanical-engineering parts, but seem fine if you don't mind the rather "building-site" look and remember some are not quite as squarely bent as you'd want.

Include cross-members of the same box-section in the top frame, their top surfaces flush with the rest, to take the weight of the lathe below the headstock and the tail feet.

For a splashback taking little or no extra load, you could extend the uprights, or you simply add a frame made from 25 x 25 x 1mm square tube to which the sheet material is held by self-tapping screws.

Use the angle-section for diagonal braces on the end-frames, and for horizontal rails to hold shelves or cupboards.

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You could go all-angle – I would suggest heavier section because L-angle is inherently less rigid than box-section, size for size. Perhaps 50 x 50 x 5 or even 6mm, 'L' . Again, it's how you use the metal more than its size that counts.

Finally….

– Think about how to stand the whole lot on the floor so all four corners share the load: levelling feet, for example; or bolt it down with shims as required?

– The bench top: Remember that wood, in bulk plank or some composite form, is not best for supporting a machine-tool as it can warp. You can use it as a surround, if the lathe and its chip-tray are bolted through it to the steelwork in such a way that the wood is not really supporting it.

[Paul LousickParticipant @paullousick59116]

If the mounting feet on the lathe sit directly above members on a rigid frame, the type of material used for the deck can be anything and does not need to be load bearing.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bill Phinn on 03/04/2023 23:43:58:

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Where would you start?
[…]

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In your situation, Bill … I would start by analysing what is wrong with the bench you have bought.

You have already noted skimpy material and poor welding, but the major its failing is lack of triangulation … as it stands, all three of the supporting rectangles are prone to ‘lozenging’.

Even a single diagonal brace across each opening would stiffen it enormously; but a useful alternative is to add sheet material as a diaphragm … This has a similar effect to an infinite number of ‘spokes in tension’
With a little more effort, you might then develop it to include some storage!

Work for a while on improving that one, and you will intuitively understand how to build something better, with the tools snd materials at your disposal.

MichaelG.

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Edit: __ Just found this [shame the Sealey folks didn’t]
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Edited By Michael Gilligan on 04/04/2023 07:53:22

[Robert Atkinson 2Participant @robertatkinson2]

One thought is to use ground shoulder bolts in reamed holes for the main joints. Do inital assembly with the thread size e.g. M6. When all square and level replace one fastener at a time. Drill and ream each hole to to shank size e.g. 8mm. you can re-use the nuts at least. Not super cheap, but no movment in the joints and if disassembled will go back together perfectly. An example bolt:
https://uk.rs-online.com/web/p/shoulder-bolts/0399173
Other and lower cost suppliers avalable but that link is likely to last longer than most.

Robert.

[BazyleParticipant @bazyle]

Are you obsessed with it being metal?
What you actually want is anti-vibration which is helped by mass and rigidity. The traditional wood bench is characterised by 2×4 real wood. This is not so easy to prevent the lozenging mentioned above. |
Although chipboard is crap kitchen cabinets are quite strong. So substitute plywood for chipboard each side and back to keep it square with just 2×2 to make the joints and feet to spread the load. Have another panel just forward of the lathe headstock for more support and conveniently support shelves about 15 in wide. Make the top with 2×4 or 2×6 or scaffold boards whatever your local skips provide, and top with ply then a thin metal drip tray.
2/3 of the weight is under the headstock hence extra leg; the other end can be lighter and less strong if your skip finds don't stretch in one span.

[martin haysomParticipant @martinhaysom48469]

as you have already bough a bench. i would strengthen that using the ideas above.

[Nick WheelerParticipant @nickwheeler]

Posted by martin haysom on 04/04/2023 10:43:26:

as you have already bough a bench. i would strengthen that using the ideas above.

If I had just spent £600 on a fairly small bench, I'd expect to be using it as is for the next 25ish years.

[Clive FosterParticipant @clivefoster55965]

I imagine there are some subtleties of construction that seriously affect the stiffness of benches made like the Sealey one in question.

Back in the early days of the DERA / DRA / Qinetiq / DSL morphing process management dictated the wholesale installation of new lab benches and cabinets based on bolt up frames of that style. Although vastly inferior to the old style solid teak benches (and storage units) those frames were adequately stiff and up to moderate metalworking, sawing et al duties with a medium sized vice fitted. Used free standing so not as stable as you'd ideally like but I'm pretty sure that bolting down to a solid floor would have fixed that.

Simple standard hex socket bolts did the holding together bit so the shoulder bolt refinements suggested by Robert wouldn't have been necessary although correctly engineered in they would undoubtably be effective. It's around 30 odd years since I helped assemble a set so I don't recall anything spectacularity clever in engineering terms. Frankly I was surprised how good they turned out. But still glad that I made sure my lab didn't get the modern kit!

First step is to take a good look at how the bolts up joints align and go together. It dosen't take very much fitting infelicity to make it all seriously wiggly. If the fits are good next step is to brace the open panels at side and rear. Whether simple diagonal struts or diaphragms. If you can live with the looks aluminium tread plate panels are seriously stiffer than plain alloy or steel of the same nominal thickness. I'd also put a horizontal strut at the front about 6" to 9" down which will make considerable difference, especially if a brace or diaphragm can be added.

Clive

Edited By Clive Foster on 04/04/2023 12:13:46

[Niels AbildgaardParticipant @nielsabildgaard33719]

My ideal looks something like this three point furniture:

[old martParticipant @oldmart]

That new Sealey bench could be stiffened with some bolted on diagonal bracing at very little additional cost and effort. If you are concerned about the top strength, then a couple of layers of 19mm thick plywood added would hold a couple of tons. If the existing top can be removed, the plywood could go underneath.

[Bill PhinnParticipant @billphinn90025]

Thanks for everyone's replies. There's a lot to mull over there.

I've not yet decided whether to use the Sealey legs etc. with more bracing or build a base from scratch. I bought some 2mm thick angle braces and some flat steel bar for this purpose, but before posting this thread was pondering starting from scratch and sidelining the Sealey legs etc. for use on another less critical kind of bench.

Don't worry, Nick Wheeler: the link I provided was to show the bench I bought, not the price I paid for it.

The need for triangulation seems to be commonly agreed on. Statical determinacy is a new phrase for me. It strikes me that a structure can be both statically determinate and have no sway mechanisms and yet still be inherently weak; it depends on the materials used, and how they are used, to achieve statical determinacy etc. Ensuring there is statical determinacy and no sway mechanisms is clearly a useful starting point, nonetheless.

Two details I was planning to incorporate into any completed bench are castors and levelling feet. This is another reason why I started thinking the Sealey bench wouldn't be appropriate – because it would be too high off the ground once castors were installed.

[Tony Pratt 1Participant @tonypratt1]

Posted by Bill Phinn on 08/04/2023 14:47:33:

Two details I was planning to incorporate into any completed bench are castors and levelling feet. This is another reason why I started thinking the Sealey bench wouldn't be appropriate – because it would be too high off the ground once castors were installed.

Not sure why you would need either? It's a bench.

Tony

[Bill PhinnParticipant @billphinn90025]

Posted by Tony Pratt 1 on 08/04/2023 17:52:44:

Posted by Bill Phinn on 08/04/2023 14:47:33:

Two details I was planning to incorporate into any completed bench are castors and levelling feet. This is another reason why I started thinking the Sealey bench wouldn't be appropriate – because it would be too high off the ground once castors were installed.

Not sure why you would need either? It's a bench.

Tony

Regarding levelling feet, Tony, if you can suggest a better way of quickly and easily making the bench level when the floor isn’t, I’d be interested to hear of it.

I need to put the bench against a wall, and envisage wanting to get to what’s on the far side of the bench occasionally without having to lift whatever’s on the bench off it first.

Which brings us on to the last consideration, which is that when the bench is in situ against the wall there wouldn’t be enough depth from the front of the bench to the wall to get the legs of my engine hoist under it far enough to deposit a lathe centrally [front to back] on the bench. Again, if you can suggest a way round this when lifting, say, a 200kg lathe on to a castorless bench [all other things being equal], I’d be genuinely interested to hear of it.

My 230kg milling machine sits against the wall on a 2m long wooden bench I made. The bench is supported on nine braked casters as well as levelling feet. It is rock solid. The castors came in very useful when I had to pull the whole bench away from the wall recently to fit a Z axis DRO and perspex screens over the lower part of the windows behind.

[Howard LewisParticipant @howardlewis46836]

Always a believer in the conservation nof energy (Especially my own! ) I would opt for bolting a thin sheet steel panel across the end rwo legs and the back.

This will stiffen the bench enormously (As Received its torsional stiffness relies only on the strength of the welds holding the legs to the top rails )

The space on the front, open, side can be folled with shelves or drawers, for extra storage, if you wish

(Very usedul for lathe acessiries such as chuccks, steadies etc. )

Howard

Edited By Howard Lewis on 09/04/2023 20:45:19

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