How strong is wood?

The Warco cabinet is 550mm wide X 640 deep. The base of the M/C seems to be a rectangle, 2" wide that sits just inside these dimensions. So if you are building a reproduction of this, then using a 4" thick laminated top will mean that only the edges of this top are carrying any load, the centre having nothing sitting on it. If your top is going to be substantially wider then the top will have to carry a load and the best use of material would be to use the 4 X 2 on edge as it 8 X stiffer. ( Stiffness of beam is proportional to height ^4 and directly to its thickness). The 4 X 4 legs are really a bit on the large side, my 10 seater dining table has 4 legs about 2 3/4" square.

I would approach this by using 3 off 2 X 2 legs on each side, each having a 3 X1 strut between them on edge (perhaps two on the front one). The top could be 22mm P5 chipboard, and the 3 closed sides 1/2" ply. All joints screwed and glued (NOT with PVA). Really not sure what to do with the base, are you going to use leveling screws/bolts? Fixing a bit of chipboard on would certainly square the box up and make it rigid, but then the load is carried by its edges and would have to be transferred to the floor. perhaps a bit of roofing felt under the chipboard and some screws into plugs if its a concrete floor might be enough.

I have been cogitating about a new stand/cupboard for my lathe, headstock end fixings 4 X 1/2" whit on 4" X 2" centres and tailstock 2 X holes at 3" centres, about 40" apart to carry 5 cwt. My problem is getting the major weight of the headstock ( 3 1/2 cwt?) out from its 2" X 4" centre to 20" square cabinet sides.

Frank

Frank

Thanks for all your replies. Too many for me to address individually, but the concensus seems to be that my plan of building a 2x4 bench for the mill won't lead to catastrophe. Special thanks to Steve for taking the time to draw up and post a design using lighter materials - but I actually have a fair bit of 2x4 so was looking to use it up, and I'm not too worried about the the weight of the bench. It's interesting though - the designers at IKEA must have a very good understandingof material properties - the bits seem so flimsy but when it's all bolted together it actually works. I'll just over-engineer though!

JasonB and Bazyle - thanks for reminder about the drawbar. I'd like to say that because the mill has an R8 taper I'll never have to change it and I'd planned for that, but sadly I can't! Senescence I suppose. Good point though!

I thought that wood was probably stronger than I thought, but good to get confirmation.

Robin.

And don't for get that weight for weight, wood is stronger than steel.

All joints screwed and glued (NOT with PVA). What have you against PV? I appreciate Powdered Resin glue etc is very good, but if it screwed as well as gluing, what could be the problem?

Robin - that vital bit of missing information (that you already had the 4x2) changes things completely from a cost point of view! I think I would still use something man-made for the very top surface, maybe an offcut of kitchen worktop, fixed down to your laminated 4x2 'sub' top with fixings that will allow the sub top to move - maybe some oversize screw holes with penny washers under the screw or bolt heads.

You're right about Ikea cabinets - the extra strength that is gained from adding a skinny hardboard back to a kitchen unit is worth many times its' cost or weight. For your bench the addition of some thin ply panels to the back and/or sides will stiffen the structure considerably, even if it doesn't run full height, so if you have any offcuts lying around they'll be worth adding. For glueing the 4x2 you probably need something that will accomodate a bit of wood movement, like epoxy (too expensive but excellent), PVA or 'No-more-nails' - the latter is not something I would normally use but in this case it is probably the better option as it is cheap, gap-filling and flexible when cured.

For a strong flexible bond on wood I've used polyurethane sealant/adhesives such as are sold for boat building. Try Loctite or Sikaflex. The bond will be stronger than the wood.

Russell.

Beware using MDF, chipboard, OSB ply, or unreinforced concrete as a top unless supported by real wood cross pieces underneath as all these particulate materials can give way suddenly. Timber will give a warning by bending and cracking first. MDF is also unsuitable for the vertical frame as in kitchen cabinet style frames. Proper plywood however is good, even better than plain wood in many ways. Concrete is ok if it has reinforcing rods so it can break without completely failing.

Quite true Bazyle but would add many years ago built such a thing as OP intends.
Uprights and tops framed with 3x2" topped off with waterproof interlocking mdf floorboard. The noise was unbearable in fact annoying amplifying vibrations maybe 100 fold with belt driven mill. Very similar noise levels heard off railway sleepers on wooden bench.
Create a box it will be even more noisier.

Same mill on 1x1x1/8" RSA front two uprights, with top frame rawl bolted to back wall no rear legs to sit 5/8" mdf almost silent.

The wall will help with that as like block work sound and vibration wise it's pretty dead.

I've also stabelised legs at the bottom by fastening them to the floor - even if they are wood. Fastening to the wall will also prevent anything tipping side ways. MDF seems to be pretty dead too.

John

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John

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Whats wrong with PVA? Well its not damproof,for a start. My Teacher , who taught me workshop techniques at night school, said he glued two piece of wood together and several days later he held one in a vice and loaded the other end, after a couple of days the joint had swivelled but remained "glued" as far as one could tell. i.e. it creeps under load. If you look through a catalogue, you will find some glues with a "D5" rating, including Cascamite which leads me to think "D5" has some superior quality about it.

I'll creep away and do some more research on what D5 actually means.

Frank

I owned a house with horsehair and lime plaster over lathes. Old and tending to crumble it was difficult to get fixings to hold. I attached a 6 foot length of 15mm sq timber to the wall with PVA held with tacks until it went off and then found that i could suspend my 17stone by fingertips from that. But then again that's effectively some 36sq inches of suction power.... I built a whole wardrobe unit. along the end wall of that room with the only wall fixings being PVA 15mm sq battons. I could sit, stand or swing from any part of that and the unit was still good when the house was sold 20yrs later.

It's not the glue it's how and where you use it. These days i tend to use brown foamy glue or epoxy and clamp joints until set with no screws.

I also carried out simiar tests on commercial kitchen units some 15yrs ago and can confirm that if you pulled out the drawers in Ikea and sat on them they broke whereas the ones at Magnet could support me. As for the screwdriver across laminated flooring scratch test.....I ended up buying at B&Q

The D5 indicates structural grade and will often be polyurethane - the same stuff they use for aerosol filling foam but much more viscus and with a less active foaming additive. If you use it, don't get it on anything you don't want glued (fingers for instance) as it is not coming off in any hurry! for interest, this is generally what is used for glulam beams and such like.

Mark

BTW, it is also fast as you would expect of spray foam type products when they encounter moisture

Edited By Mark C on 23/09/2015 22:11:20

Polyurethane foam is used to stick plaster board to Celcon blocks quicker the dab method also does not foam as much as sealer/filler.

Comes off with acetone at least before it has set or the stuff used to clean the guns.

Bob

Bob, the solvent cleaner is ok when it is fresh out the gun but has little effect when it has polymerised (if that is what happens?).

Mark

I was wrong about the D5 bit above, I was thinking of D4. There may well be a D5 grade but the stuff I was thinking about was D4.

Mark

Thanks for further contributions - I should have said that I have timber in abundance, the space behind my back yard is being 'developed' and the contractors asked if they could have access to the yard for scaffolding - fine I said, thinking it would be a few weeks. It's a year on now, and they've finally swept away the last of the Coke cans, squashed cigarette packets and other builders paraphenalia, so I have my yard back. Well almost - I'd asked if they could leave me any wood spare for burning so I have about 20 8 foot by four pallets, a stack of CLS and several rolls of earthwool surplus to their requirements. It reminds me of when I was working and needed a new circuits in my lab - the guys from Estates would come in with 50 metre roll of wire booked out from the stores, do the job and leave half the roll behind.

I don't have a problem with glue - Titebond III hasn't let me down yet, it'll do.

Steve - I've enjoyed playing with the Sagulator - I've got bookshelves to do as well!

Regards Robin

Titebond III seems to be rated on American site its a PU type. I did not know it was available over here. I did actually try and do some research on the D5 topic, but got no where with it. Interestingly, Wiki also said that PVA creeps under load, but nothing very specific. There does not seem to be a "killer application" of glue yet.

Frank

I get it from Axminster. Having on occasion vented my frustration on botched woodworking projects with a lump hammer I can confirm that it is indeed stronger than wood...

Robin

I have been using a bench with a mill and lathe on it for over a year now with no flexing or vibration problems.

It has a frame work of 4x2 timber, uprights and cross pieces. The top is made up of three 22mm flooring panels glued and screwed together at 150mm centres. The rear of the frame is screwed to the wall.

Titebond (type I, II and III) is an aliphatic resin glue, with characteristics closer to PVA than to PU glues. Titebond III in particular is the most water resistant of the three types available, and while all PVA and aliphatic glues are flexible to a degree when cured (as is epoxy of course) it is not susceptible to creep as a result of damp or humid conditions.

Aliphatic, PVA and PU glues all rely on close fitting parts and minimal joint thickness for success. PU will foam to fill any gaps, but the foamed cured glue has little or no strength. Epoxy is an engineering material in its' own right, as well as being an adhesive, so with the addition of, say, microfibres is an excellent gap filler.

If epoxy resin is not the ultimate killer glue I don't know what is - capable of bonding a range of materials, of filling, fairing and filleting, enormously versatile due to the range of fillers available and the types available to work at various temperatures and with differing open and curing times. The only criticisms are that it is fairly expensive, can trigger allergic reactions in some people and does not bond some types of plastic.

Apart from Epoxy, I would have no hesitation in recommending Titebond or PVA for this application. In fact the only glue I would never recommend is Cascamite, Extramite or whatever it is called these days. In many years of exterior joinery and marine work, it is the only glue that has consistently failed dismally over the long term, or where conditions are not optimal. It is brittle, weak, has a long cure time, will not fill even the smallest gap and is unkind to tools when cleaning up.