Bracing top and shelf for dumbbell stand?

[jb603]

Hello, I've recently inherited some ironmaster dumbbells, and found an old saw stand that I thought would be a good solution for a dumbbell stand. The only tools I have are a drill, handsaw, hammer, wrench, pliers.

My question concerns creating a wooden top, which I can get cut to size for me, out of 30 mm ply, and a shelf that goes on the second tier beneath. These would fit on and there are already holes for the top to be bolted on. But I am concerned, since I will be putting about 60 kg on the stand, with the ply bowing over time. I am asking how I should brace the table top/shelf underneath. I can get hold of wood, and I can cut it with my handsaw and I can drill holes, etc., but I'm not exactly the sure about the best way to do this. If you can help me, please see the pic of the saw stand i have.

I am very grateful for anyone's expertise here. I'm a total newbie. Thank you!!!!!

 

[Myfordman]

So your panels will be say 600mm square and 30mm thick? I can't see those moving under 60kg load.

Google for "sagulator" an online calculator for shelf sag. Not sure if it copes with shelves supported on all four sides but you could start with supporting at two end and see what the sag will be and just say it will be soooo much less for a shelf supported on all four sides.
You will need to lip the ply to stop things rolling off and that will further stiffen the shelf against sag.
Gut feeling says to me that you will have no problem at all.

 

[sunnybob]

A lump of angle iron bolted across the middle with the ply on top will never sag. 8)

 

[MikeG.]

I weigh 73kg. If I stood in the middle of a piece of 30mm ply about 400x400 (guessing), which was supported all round, for half a lifetime, it wouldn't sag. Even Steve Maskery wearing stilettos wouldn't make it sag.

 

[jb603]

Thank you to you all. That is very encouraging. Maybe will leave it as is but that is a good point about angle iron and also lipping. Also great to know there is a 'sagulator' -- will check it out!

Is there somewhere I can learn about how to add a lip? Again, apologies for my total ignorance.

And with angle-iron, I'm assuming I'd need a special drill bit to get through that if I tried it, but not sure what that would be (sounds a little scary, tbh but maybe not). Thank you -- a big part of this for me is just learning basic stuff so I can move forward and actually build something someday.

 

[sunnybob]

Angle iron is soft. It gets its strength from its shape. The same piece of steel flat would hold very little weight without sagging.
Any normal metal drill will drill it fine. If using a hand battery drill, keep the speed medium, too fast and the drill will overheat and go soft.
Dont push too hard. mild pressure lets the drill do its business properly.

With the weight and sizes you quote, I'm not arguing with Mike over weight bearing (I upset him enough as it is :roll: :lol: ) but why not learn about angle iron as well? 8)

 

[MikeG.]

.......... I'm not arguing with Mike....(I upset him enough as it is :roll: :lol: )......

You? Upset me? No.

 

[owen]

If you're that concerned about strength, 30mm ply would be plenty overkill as Mike says, but you could always just use scaffold board? It's easy to buy a length and cut to size yourself then too. And with the left over piece you can make yourself a nice shelf for the kitchen

 

[sunnybob]

.......... I'm not arguing with Mike....(I upset him enough as it is :roll: :lol: )......

You? Upset me? No.

phew, thats a relief, I can forget about the contract you put out on me over the chisel incident then. :shock: 8) 8) 8)
I'll go out and disarm the claymores. :lol:

 

[MikeG.]

.......... I'm not arguing with Mike....(I upset him enough as it is :roll: :lol: )......

You? Upset me? No.

phew, thats a relief, I can forget about the contract you put out on me over the chisel incident then. :shock: 8) 8) 8)
I'll go out and disarm the claymores. :lol:

.....and the plan starts coming together........ :lol:

 

[jb603]

Heh, I can see there is some history here!

Another super basic question regarding the same project: I am hoping to pilot drill holes through the wooden top, then countersink a bolt and tighten down to the metal frame with a nut and washer on the other end. Been looking at WikiHow to 'countersink'. To put through the bolt, can I screw it into the wood after just doing a pilot hole (even if the bolt doesn't have a pointed end like a screw?) or do I do a pilot hole that is about as big the bolt since the bolt may not itself drive through the wood? Hopefully this makes sense.

 

[Myfordman]

For that sort of fixing method you want the bolt to be a sliding fit in the wood and the metal frame so that the nut does all the compression. If the bolt were threaded in place then the nut would be fighting againat the thread it had cut into the wood.
For a more invisible fixing use 25mm long wood screw from the frame up into your 30mm shelf. A slight countersink in the metal would be a nicety but by no means essential. The wood screw would need an undersized pilot hole but not all the way through as it will show on the top side.

 

[sunnybob]

Wood screw from underneath is the simplest method. If you wanted to use machine thread nuts and bolts, then it would be best to get "nyloc" self locking nuts, to stop them coming loose over time with vibration and movement.

 

[profchris]

For that sort of fixing method you want the bolt to be a sliding fit in the wood and the metal frame so that the nut does all the compression. If the bolt were threaded in place then the nut would be fighting againat the thread it had cut into the wood.
For a more invisible fixing use 25mm long wood screw from the frame up into your 30mm shelf. A slight countersink in the metal would be a nicety but by no means essential. The wood screw would need an undersized pilot hole but not all the way through as it will show on the top side.

Screws from underneath is the way to go - perfectly strong enough, you only want to stop the top sliding off the frame.

As you're new to this, the size of hole you want to drill is (roughly) the diameter of the solid part of the screw (ignoring the threads). Hold the screw and drill bit up to the light, one in front of the other, and you can see if your drill bit is the right size.

To avoid drilling through to the top surface, measure the screw length and then stick a bit of tape around the drill bit at that point. When drilling, as you get close to the tape slow down - some drill bits can drag themselves rapidly through the wood if it's fairly soft!

Apologies if you know all this, but the usual way to learn about depth marking a drill is to go too deep and ruin things.

The lip on the top is simply strips of wood around the edge, sticking up enough to stop your dumbbell rolling off. Attaching them to the edge, rather than stuck down to the top, probably looks better. But then you have to make neat corners (a mitre joint like on picture frames works, but is hard to do accurately). If I were making this I might just glue to the edges and, when the glue was dry, just round off the corners.

 

[jb603]

Thank you to all and to Myfordman, profchris, and Sunnybob for the recent replies; no advice here is too elementary! Noted!

I will post pics once I've got it sorted (hopefully ... if all goes south then maybe not!)

 

[sunnybob]

Nah, we like horror stories.
makes us mere mortals (me) feel better. :lol: 8) 8)

 

[Chris152]

jb - just out of interest, what's a dumbbell stand? I did a search and saw racks but no stand.