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How strong is wood?

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Robin Graham21/09/2015 21:04:41
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If all goes to plan I'll be buying a new milling machine (Warco GH Universal) soonish. It'll be sited in a cellar with a low vaulted roof, which doesn't give enough headroom (by about 2.5 inches) for it to be mounted on the stand Warco offer. So I'm thinking to bench mount the thing - I'm not worried about it being a bit lower than design because I'm below average height myself, but I'm wondering if a wooden bench will be strong enough. The machine itself weighs 320kg - I am thinking to make the bench by laminating 4x2 redwood, so a 4 inch thick top and 4x4 inch legs. Trouble is I have no idea how strong wood is! Has anyone out there done anything similar and could advise?

Best regards, Robin

Neil Wyatt21/09/2015 21:27:30
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320 Kg is about the weight of four men. Well-made I'm sure your bench will be strong enough.

Neil

Bob Brown 121/09/2015 21:27:43
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A wooden bench made out of 4x2 should be more than capable of taking the weight as long as the bench design is good and the span between legs is not too big e.g. less than say 1.5 metres. Although not as heavy as the GH, I have my Dore Westbury plus bench drilling machine on a 4x2 bench with a plywood top + a lot of other stuff. Wood is a lot stronger than you think.

Bob

 

Edited By Bob Brown 1 on 21/09/2015 21:30:00

Steve Pavey21/09/2015 21:49:22
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I don't have my little civil engineers pocket book with me at the moment, but assuming that your table is going to be about 1000 x 800 mm, and the mill weighs 320 kg, I don't think you have a lot to worry about.

Using **LINK** as a rough guide (its really intended for bookshelves and the like) the deflection is well within acceptable limits - 0.013mm/305mm sag compared with the acceptable limit of 0.51 mm/305mm.

The only thing I would be slightly concerned about is seasonal movement. If you intend to laminate a solid top 800 wide from timber with a nominal depth of 100mm there will be movement, with both the width and the depth changing with the ambient humidity levels. Your bolts will become loose when the timber dries out, and the hole positions will move as well. You could counter the width-ways movement by cutting slots rather than holes.

I think a better solution would be a couple of pieces of steel channel to mount the mill, and use the timber just to fill the remaining gaps in the top (in which case you could use something much thinner as it wouldn't be load-bearing. The 4x4 legs will be fine - timber doesn't move much along the grain and the size is much more than adequate (but don't forget the diagonals to stop it racking, or maybe a plywood back and sides). To be honest, you could probably build a strong enough base using just 18mm flooring grade plywood and dispense with the softwood altogether - you wouldn't need to worry about timber movement at all and you'd end up with a useable cupboard space.

Breva21/09/2015 23:38:21
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Robin,

The bench you suggest would be more than adequate.

Consider Bob's suggestion above and maybe to avoid any movement due to changes in humidity why not use a bit of kitchen worktop with laminated top. I would put a coat or two of paint or varnish on the bottom surface to seal it. It comes about 2" thick and if supported by 4x2s around the edge and one across the middle it will never budge.

If you use single 4x2 for the frame and sheet it with 12mm ply screwed and glued you will eliminate any tendency to move and you have useful storage for all your bits.

John

Ady122/09/2015 01:02:56
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You can always beef the wood up with some angle iron

A cheapo welding box and some angle iron is another option, enclosing the wood in a steel frame

Edited By Ady1 on 22/09/2015 01:09:24

JasonB22/09/2015 07:36:46
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Don't forget to allow for changing the drawbar if needed!!

Neil Wyatt22/09/2015 08:36:54
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Counsel of perfection would be tp place the legs under the lathe's feet and avoid that cantilever deflection of 0.013mm.

Steve Pavey22/09/2015 12:40:33
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Posted by Neil Wyatt on 22/09/2015 08:36:54:

Counsel of perfection would be tp place the legs under the lathe's feet and avoid that cantilever deflection of 0.013mm.

Er, it's a mill, and it's not a cantilever, just a simply supported beam. But anyway, the op's proposed method is really going overboard and will result in an enormously heavy bench. Something from some cheap 18mm sheet material is more than strong enough, maybe along these lines:

Vic22/09/2015 14:35:14
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I've used CLS timber from Wickes for all my benches. Wood is cheap so no need to risk building too light.

Bazyle22/09/2015 16:16:13
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Re overall height. Check your drawbar clearance to ceiling too.

Tim Stevens22/09/2015 16:59:14
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You need to be careful to cope with the sideways wobbles produced when the tool is not central - ie its C of G is not in line with the spindle. If your proposed bench is as in the sketch, you will find that it will wobble at the floor supports, and the sides at different rpm. Diagonal bracing firmly fixed at both ends will help, both across the design and at right angles to it (ie in both the x and y planes) and screwing the bench top to a strong wall will help too.

Cheers, Tim

Ajohnw22/09/2015 17:22:43
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If I used mdf I would also use double sheets at the back to brace the sides. If that sort of weight tips a bit sideways for some reason a thin back wouldn't be a good idea. Actually the fact that only the back was braced would bother me.

I think for low cost and strength I would teach myself how to lay high density concrete blocks - not forgetting to add what I vaguely remember are called reveals at the front - walls for an L shape and I would lay all of the way across at the back. These blocks are dead easy to cut with an angle grinder and are also load bearing. The super light ones are more for insulation. If the walls were under the millers feet you could simply lay a sheet of mdf across the top maybe with checker plate or steel sheet etc on it.

John

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Bob Brown 122/09/2015 18:11:57
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Posted by John W1 on 22/09/2015 17:22:43:

The super light ones are more for insulation

John

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If you are referring to the likes of Celcon blocks then that statement is not strictly true, they are used in houses for the inner leaf and do offer some insulation but they also support the roof not the outer leaf of a cavity wall. Celcon blocks are a lot easier to handle and can be cut with an old wood saw.

FYI: a standard Celcon block is rated at 3.6N/mm2, Concrete = 7.3N/mm2

Ajohnw22/09/2015 18:23:37
3631 forum posts
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I'll note that in case I need the idea Bob because they are easier to use. The high density one are porous as well so might be some way in between. I've laid some for a garden wall some time ago. They are sized so that corner interlocking works out and the main problem I had was mortar between ends. Some one that could do it quickly said I should have used a bigger trowel. I found a pointing trowel useful - it's just a narrow strip of steel.

John

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Jeff Dayman22/09/2015 18:35:35
2200 forum posts
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I've never seen a concrete block bench for a small mill or lathe anywhere, ever, industry or in home shops.

As wood is so much less effort to work with, and has high strength for a given section/thickness, why use concrete blocks, lightweight or otherwise?

I think they would be bulky inside a shop, and would not take any side loads or vibration as well as a wood or welded steel bench. Both the wood and steel would be more compact structures, leaving more room for storage underneath, and shedding no abrasive dust over time onto stored items like concrete would.

spruce/fir 2 x 4 / 4x4 and a laminate countertop or a 3/4" plywood top would get my vote as easiest and cheapest, with an angle iron welded frame and laminate countertop a close second. Built several of both types and very satisfied with all.

One time I had reason to support the front end of a medium size north American car on a 4x6 foot bench built of spruce 4x4 legs and 2x4 crossmembers screwed together. Car weighed about 2400 lb. The bench supported the front end with no trouble while the suspension was removed and the frame got rust repairs by pathing and welding. Probably more than half the car weight was on that bench. We did it that way rather than on normal jackstands to make it easier for one of the crew who was in a wheelchair to access the work area. The repairs turned out great.

Good luck with your bench. JD

Bob Brown 122/09/2015 19:01:03
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It is possible to bond Celcon block with a mortar similar to tile adhesive in its application thin set called Celfix, bit like the advert for Fishermen's friends, "Corr talk about strong".

Bob

Alan Rawlins22/09/2015 19:42:54
74 forum posts

If you but 3/4" birch ply and screw and glue two pieces together you will an extremely strong top and very nearly flat and true. This is what I used to mount my Warco 250 lathe onto, on top of their metal cabinet as the cabinet wasn't sturdy enough IMO. Mine is also bolted to a conctrete floor too for extra rigidity.

Ajohnw22/09/2015 19:54:53
3631 forum posts
160 photos

I'd hope that the OP's concrete floor is sealed. Dust etc. Personally I would put doors on it and shelves inside.

I believe some of the blocks might have holes for rebars.

I bought a lathe recently and noticed some vibrations. I'm not mounting it the same way the owner but if I have problems I will probably buy a compressed 3'x2'x2" slab and semi rigidly mount it on it with raw bolts. The 18mm mdf pads for that are already fixed to the lathe.

Not appropriate for this because of the probably surface area loading if the miller has feet but I needed a strong bench so bought some 18mm exterior ply. Cut the bench top out and a lot of strips around 3in wide and glued and screws a lattice of them on the underside. In this case the screw heads showing on top didn't matter but it could be covered with all sorts of things. It would be even stronger if the bottom was covered and glued and screwed as well. I mounted that on 4 3in square legs and it's about 6'+ long. Afterwards I though mmmmm if it had to cope with very heavy load on it why not use blocks. As it is I at 95kg can jump up and down on it. Personally I don't much care if I have never seen some idea used some where. If life was like that nothing would ever change.

John

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bricky22/09/2015 20:05:56
542 forum posts
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Robin

Why not remove a section of the floor and fit a concrete base low enough to take the mill and the cabinet that fits the mill.Quicker than building a bench.

Frank

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