A lathe made of concrete "Historical"

[ddmunroe]

Back in 1916 there was a lathe made of concrete thus saving valueble resources during the war effort
dd

 

[Big Rack]

Hardinge at one time and maybe still made some of their lathe beds from 'Harcrete' which is actually ground stone and epoxy they had granite 'replicators' they moled them with. The idea was plenty of mass and much less seasoning. Worked pretty good I used one of their standard swiss style lathes for years it would hold .00015 all day. Look below the headstock 'Harcrete' may be cast into it. Also have seen it on SP lathes. Not the supertrick SP I last ran though it had a fabricated frame the spindle would raise and grow laterally .001 till warmed then it held well.

 

[TOOLMASTER]

Do the Flintstones know about this?

 

[Ulma Doctor]

i saw a diy concrete lathe in MAKE Magazine.
https://www.google.com/url?sa=t&rct...nud25wFFS9BfnLGKMqTPN3A&bvm=bv.67720277,d.aWw

interesting idea, but i wonder how accurate a diy lathe could possibly be?

 

[TOOLMASTER]

might not be accurate but it is solid as a rock.

 

[Baithog]

I seem to remember seeing pictures of concrete based lathes that were being used to turn Artillery and naval gun shells during WWII. I think there is also an article in popular mechanics on concrete framed machines for the hobbyist.

Accuracy is determined by manufacturing and engineering goals. They would be at least as accurate as the flood of Chinese lathes... but how much accuracy do you really need for the job?

Cancrete and cast iron have similar coefficients of expansion, but different heat conductivity. Designs could be similar in section, but the concrete would probably need enhanced heat management.

It may be better to fabricate a concrete column for some of the low end mills than grafting on hunks of steel. Steel, by the way, has a higher coefficient of expansion than cast iron. Concrete takes a long time to cure and moves a lot while doing it, but thinner sections might be interesting to mess around with. The CNC site has a forum for polymer granite. That's another cast in place alternative to cast iron... and doesn't require a foundry to do it. But that group seems to be more for dreamers than machinists and mechanics.

 

[jererp]

It seems a lot of "new ideas" are not all that new. It was interesting to read that article.

Here's my experience with composite machine bases on production equipment....for precision work (0.0001"), you need to have thermal stability. Composites take forever to achieve thermal stability. Cast iron becomes stable at a much faster rate. You have to adjust size until the machine base stabilizes. We would run heaters and chillers on the coolant system to maintain a constant temperature, to overcome changes in temperature through out the day.

 

[Andre]

I contemplated making one once, but didn't want to mess with machining concrete with diamond tools...

 

[Baithog]

I contemplated making one once, but didn't want to mess with machining concrete with diamond tools...

Don't need to machine the concrete if it is designed right... well maybe a bolt hole or two. Ways, headstock mount and such can be rough machined first, then cast into the structure and finished latter. Or you can grout the stuff in after the base is cast.

jererp makes a good point for precision machining in a production environment. Most hobby or one off work can get around the precision limitations. I made a lot of nickle silver fly rod ferrules on a 7X mini lathe. Fit had to be less than a tenth. Hand lapping made up for the sloppy lathe.

Not saying we should switch everything to concrete, but there is more than one way to slay the dragon when you don't have access to store bought.

 

[hvontres]

We actually used polymer concrete for some parts on our equipment at work. It sounds great on paper, but we had some issues getting the parts made correctly. The biggest issues we had were actually with the threads in the cast-in inserts beleive it or not. The knuckleheads at our vendor were so blind that I once managed to spot an oversize minor diameter from accross the room. It was so bad that the "thread" was more like a helical scratch... One other issue we ran into was that they could only get one part per mold per 24 hours (if you were lucky). So if we needed more than 20 in a month, we were hosed. Eventually we went back to a metal casting without any real performance loss.

But then again, an entire lathe bed made from that stuff would really dampen out vibration