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    Default Concrete machine tools

    We have seen on Gunsite the frustration of guys who’d like to be gunsmiths but are frustrated not only by legislation and a prohibitively minded police, but by the prohibitive cost of tools, machine tools in particular. But there are many more who’d like a lathe for hobby work, whether amateur gunsmithing or other things. In my short but very educational career as a part time gunsmith, I found my old Myford lathe by far the most important tool in my armoury; indeed I couldn’t have managed without it, because, as well as making unobtainable parts, making jigs fixtures and tools are a big part of a gunsmith’s life in SA because they are prohibitively expensive to import.

    Yesterday I stumbled, entirely by accident, on something very interesting. It was the story of how Pat Delaney has resurrected a century old method of building lathes from concrete. Yes I know it sounds crazy but read on.

    It was the idea of Lucien Yeomans who in WW1 realised that there’d be a capacity problem with the manufacture of artillery shells. The scale of the problem can be understood from the 1.70 million shells fired by the British in the week before the battle of the Somme. Shells are first cast then machined. Machining artillery shells needs big lathes and lots of them. But a lathe takes several months to build, while the shells were needed immediately and thousands of lathes were needed with which to make them. Yeomans’ inspired idea was to cast the bed and headstock from concrete, leaving holes in the casting for accurate grouting into position of the precision items like the spindle and bed shears. A team of four men could assemble a complete lathe in one day. The lathes were completely successful and several thousand were built. Yeomans’ biographer Shannon DeWolfe wrote that they were instrumental in winning WW1. In 1916 “Machinery” magazine published a three page article with photos that explains how it was done in detail. I downloaded the article and will gladly send it to anyone who is interested.

    If there is a downside to those lathes as an example for us, it is that machining a single product like artillery shells means that the lathe can be built to very simple design. Machining artillery shells doesn’t need a movable tailstock or even one with much movement of the tailstock ram, and it is no surprise that they made the lathes in four sizes presumably to take care of that. But its a detail that I mention just for completeness.

    The technology was found and resurrected a century later by Pat Delaney. His interest is figuring out how to bring affordable technology to poor third world societies, and his comments about the challenges faced by those societies are instructive to say the least. Delaney points out that the lathe is the key tool to everything, but that lathes are prohibitively expensive. Unless, that is, they are made by Lucien Yeomans’ methods.

    Delaney published a description of construction methods and instructions on how to build one, entitled “The multimachine open source concrete lathe project.” I downloaded that too, and will send it to anyone who is interested.

    Aside from the basic frame of the lathe being concrete there are other differences from what we think of as a “normal” lathe, the most obvious being that its bed is a pair of round bars (shears) instead of the usual V ways. Those familiar with lathes will remember the little Unimat that had a double round bar bed, and Emco later marketed a dedicated CNC version also with the two round bars.

    Less obvious is that the carriage and tailstock run on the same pair of shears, which makes it more difficult for the tailstock ram to reach the chuck for drilling work from the tailstock, but there are ways to handle that in the design of the tailstock. Delaney’s idea is to make the machine dirt cheap, little more than zero cost, by using scrap materials. For example, scrap hydraulic rams are the perfect material for the shears, various car parts can be used, eg flywheels for face plates. Cycle chains and sprockets make good gearing for threading instead of conventional spur gears. But these lathes can be built as simply or as sophisticated as you like. And if you don’t mind spending a modest sum, some items can be purchased, like precision ground round bars for the shears, and a big variety of drive belts, pulleys, chains, sprockets and conventional spur gears is available. A little research revealed that threaded bar is available up to 25mm diameter for lead screws for big lathes.

    It is of course a lot of work and only viable for those who will put in the effort for something they really need and can’t get any other way. Re materials, let me say something about concrete, about which I know something from a lifetime in construction. The standard stone component in concrete is 19mm size. But sometimes, when concrete must be poured into very tight spaces and must fill out properly, smaller stone is used, 13mm or 10mm. For hard wearing floor screeds known as grano (granolithic), 6mm granite chips are used as the stone ingredient because anything bigger will prevent a smooth finish. This might have some relevance to the quality of the finished casting, and there is a photo on the internet that shows a poor casting and others that are very smooth. I’ll need to check but I suspect that a concrete with 10mm stone will be best.

    But a very interesting special type of concrete exists, called polymer concrete. It contains no stone and one of its fine ingredients is a type of polymer. The resulting product looks and feels like concrete but is very smooth. I know a company that has pioneered its use for all kinds of products including window frames. I feel that it might be the perfect product for a concrete lathe, but I’ll need to check.

    I said earlier that the possibilities for sophistication are unlimited. A virtually unlimited number of threaded sockets can be cast into the concrete for attaching whatever fittings might be desired later. For example, if a complete change wheel gear set up for threading is wanted, it could all be assembled on a steel plate that could be attached to the concrete headstock.

    This is a path to ingenuity. Pat Delany shows an old drawing of an improvised three jaw chuck. Such a chuck can be made with any number of jaws using a motor car flywheel as the basic material. I can say from some related experience that it can be made without the need to cut grooves in the metal, and thus much more easily. Such chucks are more time consuming to use than modern three jaw scroll chucks but are much more accurate. For what it is worth, a modern four jaw chuck is about that slow, but I found mine so versatile that I used it almost exclusively despite its slowness.

    A small lathe, say no bigger than a Myford, might be better made of steel on a steel I-beam bed. But the beauty of concrete is that a lathe can be made as big as you like, any layout you like eg gap bed. Long bed lathes, facing lathes, milling machines and drill presses can be made with equal ease.

    Not that anyone will ever do this, but lathes built in this way could be mass produced and sold cheaply. And they could be very precisely made because big volume would allow jigs to be made for precise assembly rather than the painstaking hand assembly that we presently must do.

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    Default

    Very interesting stuff also have a look at epoxy granite machine tool bases it's used in the same way but it's much stiffer and has better vibration dampening lots of videos on YouTube but mainly small machines I would guess concrete would be more economical on large units

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    Default Re: Concrete machine tools

    Fascinating insight. Thank you.
    "Always remember to pillage before you burn"
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    Default Re: Concrete machine tools

    very interesting, please send me the articles

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    Default Re: Concrete machine tools

    Quote Originally Posted by moose View Post
    very interesting, please send me the articles
    Will do, Moose, but please send your e mail addy to boothroyd@polka.co.za

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    Default Re: Concrete machine tools

    Y’all must have realized that the catch I didn’t mention is that you need a lathe to make many of the parts for the new lathe. Or access to one. The only other alternative is to have a machine shop make them for you, at considerable expense but still a fraction of the cost of a conventional lathe.

    Another alternative is to recondition a used lathe. Good used lathes are expensive – even those advertised as “in good condition” don’t look too good in the pics. But lathes that need work can be had cheaply. I remember an acquaintance getting a DSG that was in fine nick except that its saddle had got damaged when it fell off a truck, for a giveaway price, and a colleague that got an older but still good DSG because its cast iron base was broken. Many years ago when working for a construction company I got word of a lathe that had been retired from the workshop. I looked at it, and although it was well worn it was complete and could have been restored. They told me I could have it for nothing. Unfortunately I had nowhere to put it. Probably just as well as it was much bigger than I could have used.

    For those who accept the challenge, lathe reconditioning can be done. Edward Connelly wrote a thick book entitled “Machine Tool Reconditioning – the art of bed scraping” in 1955, which has been praised as the bible of reconditioning by guys who have used it. It is still sold as hardback by the heirs of his estate for astronomical prices – I saw as much as $700 advertised. But it is, if the websites are to be believed, available as a free download. Unfortunately I wasn’t able to download it – maybe others will be more successful – but it can be read online, which I intend to start tonight.

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    Default Re: Concrete machine tools

    A pleasing read - thank you I will look this up further.

  8. #8

    Default Re: Concrete machine tools

    Quote Originally Posted by geopat View Post
    Very interesting stuff also have a look at epoxy granite machine tool bases it's used in the same way but it's much stiffer and has better vibration dampening lots of videos on YouTube but mainly small machines I would guess concrete would be more economical on large units
    Thanks for this. When I started this I had no idea of the education I would get. I found some amazing photos of machines of all kinds standing on synthetic concrete bases, and in many cases much of the machine is made from it. All because, as you say, of its vibration damping properties. But it is also apparent that ease of construction compared with iron castings is a significant factor, and that it is more widely used than Pat Delany mentioned.

    There is some variance in what it is called. The company I know in Cape Town calls it polymer concrete, you call it epoxy granite, and other sources call it synthetic granite. The mix varies but the common factor is no stone. As far as I can see, they are all pretty much the same thing.

    I said before that because the carriage and tailstock run on the same shears, that can cause a small problem of the tailstock ram not reaching the chuck for drilling. Playing with diagrams has convinced me that it is less of a problem than I thought, and solvable quite easily. What does happen, though, for the same reason, is that carriage travel is reduced. For the benefit of those not familiar with lathes, carriage travel is less than distance between centres, simply because some of that space is taken up by the carriage. Put simply, the carriage bumps against the tailstock before the tool reaches the end of the workpiece. The "shortage" varies according to size of lathe, but roughly, a lathe 1000mm between centres will machine a workpiece 850mm long. With these concrete lathes that will be as little as 750mm. That, essentially, is the downside of the double round bar bed arrangement. I don't see it as a problem as long as we are aware of it.

    Re that particular aspect, let me offer my "take" on the matters of diameter and length of work. To start with, there is an axiom that no lathe is ever big enough, and that is certainly my experience. What it means is that you can buy a lathe that will do 99% of what you need, but from time to time you will find yourself frustrated by the fact that your lathe is not big enough to machine a vital component. That is of course inevitable because the price of lathes seems to be directly related to size, and few of us can afford the price of a lathe whose maximum capacity is needed only occasionally.

    My experience (others may have different experience) was that most work is short, and diameter is more important than length. My work was seldom longer than 200mm and usually shorter. The longest item a gunsmith will machine is a rifle barrel, and even that is not necessary because barrels can be bought already profiled. The longest items I machined were scope lapping rods about 300mm long. Conversely, I regularly machined items of 150mm diameter, usually discs of some sort or other, like special faceplates for special jobs. And if you are a motor workshop owner it is useful to be able to skim brake discs and drums.

    A short high lathe is therefore better than a long one of low centre height. Usually. Of course we don't have that choice because a longer lathe is usually higher as well. But you do have the choice if you build your own, and that is relevant to my point about carriage travel - you can make your concrete lathe whatever length or height you like.

    As for speed - slow speeds are more useful than fast. But if you use roller bearings you can have a full range from very slow to very fast.

    On a personal note, despite my enthusiasm I'm not likely to attempt this. For one thing I'm getting too old for the effort. But mostly I don't have a workshop or other venue big enough. But I'm enthusiastic because this technology opens the way to build a lathe any desired size, of any degree of sophistication, at a cost within the reach of almost anyone.

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    Default Re: Concrete machine tools

    Fascinating topic. I followed the build of a concrete lathe lathe on Youtube a while back which may be of interest.


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    Default Re: Concrete machine tools

    I've done some concrete casting and agree with the idea of using finer aggregate to achieve finer finish and detail. Plasticizer and thorough vibration also help.

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