# Cast concrete lathe base



## Masterjuggler (Jul 23, 2020)

I've had the Horrible Freight mini lathe for a few weeks now, and the only place I can currently put it is on a wooden workbench that's older than dirt. No way to level the lathe, and it was really bad, like a 0.015" diameter change over 6" in a piece without tailstock support. I decided to cast this 2" thick slab of concrete both to level the bed, and to give the machine more mass in general. I'm going to be pretty verbose in this so I can either get criticism for how to do it better, or so other people can do this too.

I made a mold out of melamine countertop and put some 1/4-20 bolts in the right spots to act as studs for the lathe feet. I didn't feel like finding a hammer drill for the concrete and getting proper anchor bolts, and it's only a mini lathe, so this is fine. All edges were caulked.



I put in two layers of metal scrim for reinforcement. The concrete isn't any kind of fancy countertop grade, just the regular fiber crack resistant stuff. Ignore the bucket label, it was empty and just used for concrete mixing. Nearly set the drill on fire haha.



It looks pretty wet, but I really didn't over water it, it's just smoothed out.


	

		
			
		

		
	
￼￼￼

I thought 36 hours was long enough to take it out of the mold. I was wrong. The edges got chipped, but nothing major broke. It should have been more like 72 hours. I waited a few more days before mounting the lathe.



I have some level vials down to 20 seconds, but I only have a base made for a 90 second vial. After a quick check with it I went to checking with a 6" long 3/4" piece of 12L14, again unsupported by the tailstock. It took me about an hour to get it down to a 0.0005" difference in diameter end-to-end, which is way more than good enough for now. Maybe once the concrete is actually done curing in a few months I'll get it even better.



Now with the increases rigidity I'll be able to make use of a 1/2hp 3-phase Baldor motor I have coming. The brushed DC motor that came with this is wimpy as crap, and can't quite make a 0.01" pass in 1" 12L14 without stalling, on low gear. Boy do 7.5 thou passes take forever when you've got a lot of material to come off. I can also always stick a 2hp 3ph Baldor I have laying around on it if I really want to blow the machine up from a crash lol.


----------



## hman (Jul 24, 2020)

Your base looks like a great way to stiffen up/level the mini lathe.  Definitely re-check level after it's fully cured.  As for the motor, just keep in mind that there's a set of nylon gears between the motor and the spindle.  Overkill on the motor might well cause tooth decay


----------



## Firstram (Jul 24, 2020)

I use "2hp" treadmill motor with a jack shaft to get the rpm back down, you will break teeth! The gears are easy to change, I would never go back to stock power.  Have fun!!


----------



## Masterjuggler (Jul 24, 2020)

Yeah I'm definitely aware of the strength of the gears in the headstock, which is why I'm first going for the 1/2hp motor which should suit this lathe better than the 2hp motor I already have. I plan to make some metal ones at some point, but if I do snap a gear, I can always 3d print a temporary one out of nylon.

And because it's a Baldor motor, it's actually 1/2hp output, which is a big gripe I have with these chinesium motors the lathes come with, It says 3/4hp, but it also says 110V 3A input (0.44hp), and the model is ZYT-250 for 250W (0.34hp), and you don't know what the actual output efficiency is. It's probably more like 1/4hp or less when it's all said and done.


----------



## Janderso (Jul 24, 2020)

Hey that's great.
I bet that's a good stable base for your lathe.
Concrete is so versatile these days.
I really like the counter tops that are being created.


----------



## MrWhoopee (Jul 24, 2020)

One of the more memorable things I learned in my Properties of Materials class is that concrete will continue to cure, with increasing compressive strength, as long as it is kept wet. Once it has been allowed to dry the curing stops and will not resume. The strongest concrete in the world is the underwater portion of bridge pilings.


----------



## Masterjuggler (Jul 24, 2020)

Yeah, that's fine though, I just need it to not crumble lol. It's just adding some rigidity and allowing me to level. I think if someone were looking for a really bomb proof base for a decent sized lathe, at least 4 inches or so would be far better. Especially if it happens to be a floor with ground beneath it like a basement or garage, so it would be constantly damp from the moisture underneath.

Maybe at some point I'll break out comsol or something and do some structural analysis for kicks lol. I'm working through a physics degree so I have the tools available.


----------



## hman (Jul 25, 2020)

@Masterjuggler - If you decide to go the metal gear route, Little Machine Shop can be your friend:








						Metal Transmission Gear Kit | Steel Gear Set | LittleMachineShop
					

Install these steel gears onto your mini lathe and never worry about breaking the hard-to-replace gears inside the lathe's headstock. These gears fit mini lathes and 3MT mini mills.




					littlemachineshop.com


----------



## JohnG (Jul 25, 2020)

As MrWhoopee points out, concrete is really strong in compression but weak in tension.  You can strengthen a slab like this by pre or post stressing it with steel in tension at the neutral axis.  This doesn't stiffen it but strengthens it so it will undergo greater bending stress without breaking.  You can stiffen it with steel in tension on both sides of the neutral axis.


----------



## Masterjuggler (Jul 30, 2020)

hman said:


> @Masterjuggler - If you decide to go the metal gear route, Little Machine Shop can be your friend:
> 
> 
> 
> ...


You know, I've seriously been thinking about 3d printing some helical gears instead of the usual spurs. Quieter and way more durable. The issue would be the axial thrust created from the tooth angle trying to make the gears slip out of position. I think I might print some up, stick them in, and just see what happens as a test.


----------



## Weldingrod1 (Jul 30, 2020)

I've used 3d printed change gears (super oversized) successfully. Not as much load. Might work...

Arrange your thrust load to pull the spindle into the headstock!

Sent from my SM-G892A using Tapatalk


----------



## Masterjuggler (Jul 30, 2020)

I actually also printed a change gear for myself lol. A 63 tooth for more accurate metric threading. Worked well to machine a longer cross slide lead screw for an extension. Printed it out of Taulman nylon 910 and it's more than strong enough.

I did think about simply angling the teeth in the right direction to pull the sliding gear to the outsides. The problem is when I'm running the lathe in reverse, the axial thrust would switch directions and cause the sliding gear to tend toward the center, out of alignment.

If only herringbone gears could be shifted into place like that, they're just as easy to print haha.


----------



## Masterjuggler (Jul 30, 2020)

You know what? I don't need the gears to slide around. The shafts have a keyway running the full length of the gearbox, so I can just print four stationary herringbone gears and a gear selector collar. Essentially this image I got off wikipedia, but two speed instead of four.



Oh boy I'm getting excited now lmao. I'll make a new thread if (when) I do this.


----------



## Tim9 (Jul 31, 2020)

I’m sure there are some super polymer types for 3-d gears. I know I’ve read some impressive things with metal 3-D  printed items which are then oven treated. Very cool stuff. 
But that’s the total amount of “Learned“ knowledge on my end with printed gears and such.
That said, I did order an eBay thread gauge for my South Bend lathe. The 3-D g ar was pure junk. It just started to shed plastic as I used it to thread items. I made a copy of the thread gauge out of aluminum in which I did use the printed thread gauge as a model. I made a Delrin gear for it. My thread gauge has performed perfectly


----------



## OCJohn (Dec 31, 2021)

Just found this thread searching for tips to the same thing. How's the concrete base working out? 

Can you post a photo or describe your hardware solution for mounting & leveling the lathe on the block? I'm having a mental block about how to use the threaded holes in the lathe bed and still provide adjustability. Likely a simple solution I'll smack my forehead upon seeing, but my brain's in limp mode.


----------



## Masterjuggler (Jan 9, 2022)

OCJohn said:


> Just found this thread searching for tips to the same thing. How's the concrete base working out?
> 
> Can you post a photo or describe your hardware solution for mounting & leveling the lathe on the block? I'm having a mental block about how to use the threaded holes in the lathe bed and still provide adjustability. Likely a simple solution I'll smack my forehead upon seeing, but my brain's in limp mode.


It's been working out pretty well, I'm definitely glad I made the base. All I'm doing to level the lathe is shimming under the feet to get the twist out. I find this more stable overall than trying to use gravity when my wood workbench warps slightly with the weather and the weight of the lathe isn't enough to twist itself much anyway.


----------



## Masterjuggler (Jan 9, 2022)

Realized I didn't answer the question about how the lathe is actually mounted. You can see in the first post's photos how I cast some long bolts into the concrete that serve as studs for the lathe's feet to be fastened to. Definitely weld some rods to the bolt heads to spread the load so they don't just crack the concrete if you do this too.


----------



## OCJohn (Jan 10, 2022)

Got it. For some reason I thought the holes in the lathe base were threaded, but this makes perfect sense.


----------



## L Peterson (Apr 24, 2022)

I really like what you did with the concrete base. I too made a concrete lathe table for my Atlas 10F. However I might have overbuilt it a little after seeing yours.


----------



## Provincial (Apr 24, 2022)

I knew a fellow who mounted a couple of Craftsman (Atlas) 12" lathes (about WWII vintage, basically F10'a with a taller headstock and tailstock, plus the compound built taller to raise the tool post) in concrete.  When I say "in" they were actually imbedded in concrete!

Harry built a pyramid for the headstock, and one for the tailstock.  He bridged between the two pyramids (about 2' x 2' at the base) with a trough.  In pouring the concrete, it filled the forms for the pyramids, and filled the trough.  The top of the pour was above the level of the feet, and was part way up the bed itself, just leaving room for the carriage to travel.  The concrete completely filled the center web of the lathe bed, leaving no place for the swarf to go.

He had to clean out the swarf constantly, as it would bind up the carriage if left to build up.

This made the lathes incredibly rigid.  He put large motors on them and used a roller chain drive.  He had a contract to make 3/4" Acme adjusting screws, 1/2 right hand and 1/2 left hand.  He was cutting the Acme threads in three passes!


----------



## L Peterson (Apr 24, 2022)

That sounds interesting but no where near what I would do. I just made the table top out of 6" channel with a bottom and several cross pieces  welded in. I also made the lower shelf the same way then poured concrete. The lathe is actually bolted to the steel I welded across the top. This allows me to properly shim and true up the lathe.
I also covered the concrete with some table top epoxy to make it nicer looking.


----------



## Yempetryn (Oct 12, 2022)

The three—plate method is a modern technology that allows you to achieve the best results without measuring instruments.


----------

