concrete base for lathe

[woodfarmer]

I intend to install my Holbrook lathe in the barn. the current floor is cobbles/really heavy clay or granite. The plinth for the lathe will be four metres by two metres. Question is, how thick should the concrete be? I hope to use ready mixed gravel and sand adding portland cement powder to suit. I have a small mixer and hope to be able to shovel the sand/gravel directly from trailer to mixer and then tip the mixer straight to where it is needed. the cement would be measured by a container to so many shovel fulls. what ratio by volume should the cement be to the sand and gravel mix??

eventually (possibly never) I would cover the entire barn floor to the same depth, but that is a huge project.

 

[StevieB]

I tend to use 5:1 as a standard mix, 4:1 for a strong mix and 6:1 as a dry/lean mix where strong support is not essential. Best way to ensure consistency is using a bucket eg 2 and a half buckets of ballast to half a bucket of cement for a 5:1 ratio (my mixer will also only take approx 3 buckets to be full without splashing!) and then add water to suit. You can do the same thing with shovel-fulls, but getting a shovel into a bag of dust can be difficult. In your case I would go with 5:1 unless the lathe is particularly heavy or prone to move, in which case 4:1 and bolt it to the floor respectively!

Steve

 

[woodfarmer]

It is a little over a ton.

 

[Cheshirechappie]

I had quite a bit to do with the setting up of a machine shop on one of the bigger preserved railways. We used about a 6" thickness of 4-2-1 mix for the shop floor, and had some pretty big machines stood on it with no problems at all over about a decade and a half. Don't worry too much about perfect level on the top, but when you install the lathe, level it up with steel shims under the feet, and run a thin grout around the base for a really solid job. You could bolt it down, but a Holbrook is a fairly stable machine and should be fine free standing, especially if you're careful with the levelling and packing.

Finally, a simple wooden duckboard in front of the lathe makes a big difference to operator comfort, especially in cold weather. Make it easy to lift up to sweep up the swarf, though.

 

[Myfordman]

Consider making the base large enough to stand on when working on the lathe.
Generally, most comfortable when the centre height is level with your elbow making your forearm more or less horizontal.

MM

 

[John15]

A 5:1 mix as mentioned by Steve should be strong enough. Try to keep the added water to a minimum to avoid shrinkage cracking - just enough to make the concrete workable. For compaction on a base such as this you can pun it with a piece of timber to drive out the trapped pockets of air. Also it's a good idea to keep the base wet for 3 or 4 days to allow time for the cement to hydrate, again to avoid cracking and to give the concrete every chance of reaching a good strength.

John

 

[woodfarmer]

Thanks for all your advice....Hopefully it will work out well, just trying to avoid as much work as possible

 

[hansonread]

If you are unsure on the ground that you are laying the concrete on, if its prone to movements and cracking etc, you may be worth adding some A142 Mesh to the base to stop any future cracking. Its around 20 quid a sheet, but well worth it in the long run.

 

[bellringer]

for metal lathe the min recommended is 6 inch and at work we have a 12 inch thich floor with 8 cnc machines on it 2 Manuel lathes 6 Manuel mills and loads of grinders but 6 inch is recommended min