Anchoring lathe - should I or shouldn't I and how to?

[mikoyan31]

Shopped concrete work is expensive for a reason. Spent all morning prepping the area, setting up the forms etc. Then after lunch I started mixing, lugging and finishing the concrete. And that was just a 4x8 slab. Now I know it's probably at about 1950's level concrete technology considering what I have to work with and the garage is still chock-a-block full of crap.

So I dug out roughly 1 foot wide under where the legs will attach. I also dug out a connection between the two. Not sure if it will help but I wanted to tie it all together.

All dug out. I put rebar at about 1/2 the depth (approximately 10" or so) and ran rebar across the "key." Tied them all together and then laid the mesh down and tied it all in. I managed to forget to take a photo of this.

Spent way too much time with string and level.

And after a lot of sweat and back ache.

It may not work, it may be crap. It's mine and I made it. I'll take the forms off in a few days and see what's what. In a month or so I'll at least set the lathe bed on the slab at the very least to get it back out of the middle of the garage.

 

[Former Member]

Co

That is nice looking old lathe. I don't usually bolt mine (they are quite heavy or light enough to sit on a bench) but that one looks like it could easily be top heavy, esspecially with a motor and backgear up top. Probably a good idea to bolt it.



and not just float, the concrete itself moves about. It doesn't stop curing in 28 days, that's just when its usable, but keeps curing and moving basically forever. I couldn't quantify that, just pointing it out...it can be easily be enough to affect a lathe cut. i.e. levelling is not a one time event.

As for the strength of a slab, I've been involved in millions of square feet of industrial design builds and while fiber or rebar or mesh is important, what a slab really does is distribute a point load over the base. The thickness and compaction of the base (layer(s) of aggregate between soil and slab) is key. It gets engineered along with with the slab and soil bearing and is what lets a floor support a load. That 6" inch floor they pour in a new building might have 8 or 12" of compacted crushed aggregate underneath and wouldn't stand up without it.

I know you are just pouring a little slab with minimal weight on it, so I'm not trying to make a meal out of it, but its germane to the topic of slabs: how they perform is not just the slab, but the slab, base and soil bearing conditions.

Concrete hits 80% at 3 days, full strength is considered at 28 days (unless you have some specialty mixes). For concrete to cure properly it must remain damp, dry it out and curing stops. Its is a chemical reaction.

Yes concrete deforms under load, so does steel, stone and so on. This is called creep.

Proper rim footings and correct reinforcement prevents flexing particularly for the light weight loads we have with the machines we use.

I would go with a 6" slab because we do have point loads.

Seriously don't over think things here, go thick, do a rim footing (ie thicker (8"w x 10"d) greatly reduces movement due to heave and stiffens the slab to prevent flexing.

One the machine is mounted and levelled (trued on axises) no matter how the slab moves the lathe remains true.