|Lee Cooper||14/05/2021 22:02:22|
|6 forum posts|
Total greenhorn here, no flame please I'm just looking for input from more knowledgable machinists.
So I have the beginnings (only the beginnings) of an idea for a lathe design which I like the idea of making an open hardware collaborative project and I would like some input as to if it could work well or if it's a non-starter.
So what's the impetus behind this? I've been looking into getting a small lathe and my takeaway from quite a lot of investigation is that I can either go for a micro-lathe (sherline/Taig) and get a decently accurate machine more or less ready-to-go from the box, or go for a Chinese mini-lathe and get a far more capable machine, but one that basically turns into a substantial project to turn into a reasonably accurate machine. There's just no middle ground in the mini lathe options in terms of quality, even if I was prepared to spend 2-3 times the money. There are some suppliers that may fettle these machines up a little, but they still have many rough edges.
So since there are a lot of people out there willing to put substantial work into their lathes, could we produce an open design that will give something more accurate off the bat? I'm not qualified to answer that, but I was inspired by this video:
https://www.youtube.com/ Link removed see Code of Conduct
In particular I love the use of these off-the-shelf components to quickly produce what looks like a smooth, sturdy rail and cross-slide assembly.
I was thinking if the base was created from an I-beam, you could mount a pair of tubular rails on the top edges of the beam (as in the video) and a second set on the underside of the top lip of the I-beam. Connecting the top and bottom sets of linear bearings with a box-section would to my mind create a very sturdy and accurate slide.
To lower the bar somewhat, commercial components could be options for some builds. GlockCNC springs to mind as a versatile and accurate option for motors and headstocks but no need to limit to just one configuration.
Any thoughts as to the accuracy of that rail concept? Anyone interested in this?
Edited By JasonB on 15/05/2021 07:01:17
|Andy Carlson||15/05/2021 08:57:32|
|387 forum posts|
I think what you are proposing is very much in line with the spirit of things here so good luck with it. There are some threads on here that amount to such major re-engineering of a mini lathe that they are not far short of starting from scratch,
Lathes come in many shapes and sizes and each major component tends to be in proportion to the others so it would probably be a good idea to define the sort of shape and size that you are intending - comparable with the Taig/Sherline perhaps? Or bigger? Or smaller?
Another fertile ground would be providing components as the basis for upgrading other lathes - for example I've seen several examples of Taig/Sherline spindles being used as a vertical milling add-on to an existing lathe... or using components to make other things altogether... like a gear hobbing machine perhaps.
I allready have four lathes though so am not really in the market for another one
|Chris Evans 6||15/05/2021 09:31:07|
1950 forum posts
The idea has some merit but as I see it most people who a mini lathe appeals to are very inexperienced.
5998 forum posts
If you think tweaking a Chinese lathe for better accuracy etc is a lotof work then surely starting from scratch is even more work. Seems a little illogical. You can also consider if you actually need such accuracy. Mostly you don't in model engineering and home shop work.
21300 forum posts
Would also depend on what accuracy is needed, some good work comes off the chinese machines in the right hands.
I've not watched all of the video yet but you ask what accuracy might be obtained. I was rather put off in the first 20seconds when the welded C section was sat on the bench and rocked from side to side by a large amount and the rails were screwed straight to that. I can't see how a lathe could turn true or parallel with such a twisted foundation. In a similar way the toolpost when tightened can be seen to be pulled upright as it sits so crooked when loose.
The concept may be there but all the parts would need accurately making and assembling if you were going to be aiming for an accurate machine and that would cost money if it were offered as a kit and probably beyound most people working with little more than a bench drill who can't weld. Take a look at some of the lower end hobby CNC kits that are about and even without steppers and control gear the component parts cost more than a Sherline let alone a minilathe.
|Michael Gilligan||15/05/2021 10:35:08|
18704 forum posts
... and the rest of us don’t get to watch any of it
”https://www.youtube.com/ Link removed see Code of Conduct”
|John Haine||15/05/2021 10:35:45|
|4096 forum posts|
Good to see the moderation policy working in line with the proposal...
I think the issue is that the people to whom this would appeal by definition don't have the equipment or probably the skills to make it work. Might be worth looking at Vinland.com - he describes making some special purpose machines from standard components - but then he is a highly skilled engineer.
|Bob Stevenson||15/05/2021 10:54:34|
|546 forum posts|
Lee,...Interesting post and subject but I feel that I must take you to task a little!....hope you don't mind!
In your third para. you make some statements and assumptions about lathes and mini-lathes which are, for me anyway, not properly analysed..... I used a Chinese mini-lathe for 10 years and eventually did some good work on it and without any changes apart from removing the rubber feet and dumping the dangerous chuck guard. I made my first clock largely on that lathe and I'm still waiting for someone to look critically at it and mention how they can see which bits were made on the Schaublin lathe.
Lathes are just tool for crafts and they are best chosen for the particular craft just as ancient man cast around for a better boulder or a sharper twig etc., but you have not addressed this essential matter. For every 20 or 30 or however many lathes in well loved pristine condition there is a bloke in a shed with a clapped out Myford making fantastic little gem-like items. Both 'camps' have a viable and honest hobby which keeps them happy, but NOT the SAME hobby!
In the end I changed my Chinese mini-lathe for a slightly better lathe not because I saw it as a " substantial project to turn into a reasonably accurate machine" but because I realised that it was of fatally flawed design.....you can't make a silk purse out of a pigs ear!
|Paul Kemp||15/05/2021 11:32:05|
|683 forum posts|
Well said Michael, censorship at its very best!
|2238 forum posts|
Is there any reason why the OP should not give sufficient clues/tags to allow the video to be found?
7473 forum posts
I like the idea, but there's something of a false premise in the business plan! It's the assumption that a Chinese mini-lathe is a substantial project to turn into a reasonably accurate machine.
Um, maybe. Mine all worked out of the box, and only required minor fettling. They are a bit rough, certainly not as smooth to operate as more expensive machines but the achievable accuracy is similar. What exactly is meant by 'accuracy' in the context of a lathe? Is it run-out, or dial-calibrations, or repeatability, or what? I like to see measurements and specifications rather than assumptions one machine is 'better' than another. Truth is, for many hobby purposes, manual lathes in poor condition are good enough because the operator can work around many deficiencies, such as a worn bed and excessive backlash. Diameter accuracy is achieved with a micrometer, not by relying on the dials and perfect leadscrews. The professionals spend serious money buying the best because they can't afford to waste time on clapped out old-bangers or ropey hobby machines. It's not because top-end machines are essential to do top end work, just that its faster.
In a double blind test could anyone identify the lathe used to turn one of a selection of 30mm long 10mm diameter brass rods? What would the difference be between rods made on a Myford ML4, a Myford ML7, a Myford Connoisseur, Chinese Mini-lathe, a bigger Chinese hobby lathe, Sherline, Cowells, or a Dean Smith and Grace Toolroom lathe?
Not trying to put anyone off just noting the competition is ferocious. To succeed, the open machine has to do something special, either a niche advantage, or 'must have' features, or some new appeal. Above all it must be affordable, ideally inexpensive, and simple to operate.
Have a trawl through lathes.co.uk It lists many lathes, mostly well-made and often with useful features. They tried hard to sell them in the 20th century, and most of the makers failed commercially. Why? I suggest too many lathes chasing too few buyers, with similar features for much the same cost.
On a positive note, many things are possible today that weren't before:
|Nigel Graham 2||15/05/2021 11:54:25|
|1666 forum posts|
By "accurate", how many decimal places are we talking, be they of inches or mm?
And to what end use?
Many people buy the "Chinese" (or Taiwanese...) made hobby-grade machine-tools from our reputable suppliers, and most seem to manage a decent standard of workmanship and accuracy. I would not dismiss "most" owners of the smallest "mini lathes" as "very inexperienced", as their choice may reflect what they actually make.
What is the lathe for? Many unique or very low-batch items, or many of a small range of identical items? Hence....
Are we simply re-working what is still a lathe, irrespective of how it is operated; or an exercise in building a numerically-controlled lathe?
That distinction is important. We could design a conventional lathe with future NC drives in mind, a lathe built from the outset with both manual and computer options, or a fully-NC lathe inoperable manually.
A lot of model-engineers now are using NC-machines, some converting manually-controlled machines to NC; and learning the programming adds a stimulating extra challenge to the hobby. So, pros and cons?
Fully-CNC lathes include turrets, milling/drilling spindles, auto bar-feed, through-tool coolant etc. They cannot be used manually, but are enormously valuable in industry for churning out very accurate, very precise items at prodigious rates.
How far can we design a practical all-CNC lathe for a hobby workshop? We would still need a conventional lathe for most projects, to avoid spending more time programming and machine-setting for just a few parts, than machining them manually. For best CNC advantage you are also confined to insert-tooling, economical in the trade (the customers pay!), and possibly industry-standard tool-mountings too. Getting expensive.....
The trade-off: the NC lathe happily sits making the two or three dozen union nuts you can probably buy for less than the cost of the electricity and brass you would use; but what of the two or three larger parts for the same project?
SO I would suggest if you want CNC, either make the thing useable in both modes, or make sure you keep the conventional lathe too.
If we design and build any machine-tool for our own workshops I suggest first thinking deeply why. Is it an exercise in its own right? What is to be used for? How frequently?
What of the lathe itself?
Many manufacturers have used different forms, but it must be more than mere conservatism that modern lathes are still basically what a Victorian engineer would recognise.
Drummond Bros. produced both round-bed (ground-steel tube) and conventional box-bed lathes, and typically fitted the leadscrew along the bed axis. That gives more balanced forces on the saddle. On the round-beds, this also shields the screw and nut from the swarf. Many refurbished specimens of both are still returning good work, used with sufficient skill and care.
Many CNC lathes place the saddle above and behind the bed. This lets the swarf fall clear of it, but I think also allow space for active tailstock tooling.
Those are some basic ideas. Can we develop them?
Thoughts I have had for some years - but I own enough machine-tools and unfinished projects already! These are for fully-manual or optional manual / NC; not full NC.
- Bed: three cylindrical members, full machine length, the top two far enough apart for full use of the faceplate above the central, lower, third rail. Also gives greater support for the cross-slide. The parts mounted on it are based on plates with identically-patterned borings for rigid or bearing mountings.
- Spindle bore: as large as possible for machine size; cam or similar nose-fitting.
- Lead-screw and feed-shaft placed axially (re Drummond).
- Tailstock set-over has definite centre-location - or use an easily-fitted taper attachment plus cross-slide half-nut.
- Boring-table saddle. (Myford, Drummond, Ehrlich...)
- Top-slide on worm-wheel: simple taper-setting even for facing shallow cones; also for forming partial spheres.
- Self-acting cross and long; optionally inter-geared for generating tapers including tapered threads. That idea is not original either!
- Feed / lead clutches: repeated travel limiting, including for fast screw-cutting. Think Ainjest.
- Gearbox: Imperial and Metric threads, fine feeds.
- All gears, bearings etc, stock commercial items.
- Drive. Optional 1ph or 3ph+ with VFD. Still needs countershaft / reduction gearing in primary drive.
|Dave Halford||15/05/2021 12:17:04|
|1665 forum posts|
That's all true but you don't get much fight back from hot plastic compared to a 10mm milling cutter operated in a screwed together 3mm steel frame. I suspect the mass appeal of 3d printers is more in the lack of mess and noise and it comes with a keyboard
The too many lathes chasing too few buyers etc ought to apply to the Mini lathe.
|Nick Clarke 3||15/05/2021 14:32:33|
1247 forum posts
While not open hardware, what about looking at the Gingery designs for workshop equipment?
|Neil Lickfold||15/05/2021 15:31:29|
|717 forum posts|
Having made my own spindles for a Cue making lathe, I can tell you, it is cheaper to just buy a machine and rework it of need be. In my case, no one was offering an ER40 collet spindle for the Taig based cue making lathes that were on the market at the time. I also made a second one that takes the 5c collets. Again, would have been far cheaper to have bought it of they were making them at the time, but 10 years ago that was not the case.
I have not seen the video, but from what is being described, it won't be precision at all. There is a reason that commercial machines are expensive, as there is a lot of time goes into checking parts etc and they need to be made on accurate machines. Yes people can scrap slide etc, but that take time and is a highly skilled thing to learn.
To get good precision from the mini lathes etc, they work best when they are at an even temperature. Yes some cheaper lathes need some attention to make them right, but the time you spend correcting what little may not be right or it maybe and your not aware of it, is still far quicker and more accurate than a scratch build. I had a cheaper lathe, stripped it down, stoned some of the bed area that was a little rough, recut the saddle plate with the cross slide dovetail,(it was a little out of square) and then recut the top slide dovetails as well, not parallel, and now have a very accurate machine for facing and for cutting short tapers with the refurbished top slide. This is all way quicker than starting from castings or fabricated parts or from 3d printed metal parts.
Keep thinking and see where you end up. There is a plethora of lathe ideas out there that people have made. But all of them cost way more than any mini lathe I have seen for sale.
|2894 forum posts|
I think the video may be of interest to me. Can anyone suggest a search term I might use to find it or is that against the rules as well? TIA.
|Lee Cooper||15/05/2021 16:04:17|
|6 forum posts|
Thanks folks for all the constructive comments. Too much to reply individually but I'm reading them all. A few general responses to things I've read:
- I'm aware of the limitations of my own skills and I'm not planning to dive in and start trying to build a lathe. It's a Sherline for me at this stage. It was more about throwing some ideas around. As I look around more I see a lot of people (on Youtube and others) are having the same ideas.
- I'm not knocking the Chines lathes. I think they're fantastic for the price point and I'm aware of the fantastic work being produced on them.
-Interested to read some of the links people have mentioned for some inspiration.
-Broadly speaking, if you're interested in Youtube videos on the subject try searching something like 'homemade lathe machine'
Not sure what the problem with the Youtube link was. It's not my video, I'm not selling anything or promoting any products.
21300 forum posts
But the guy has a load of links to a particular supplier/market place.
Well I watched it all and it actually cut metal quite well, as to weather the cylinders are parallel I have my doubts as I'm sure many here would not consider an old rusty roofers square the ideal look to set the head true to the bed horizontally and I saw nothing to check it was lined up vertically
Edited By JasonB on 15/05/2021 16:18:15
|Lee Cooper||15/05/2021 16:21:41|
|6 forum posts|
Fair point, Jason RE supplier.
I'm not commenting so much on this guy's particular build - more that I liked the linear slide on tubular rails as a building block. It was new to me but I now realise there are plenty of builds using these components.
|Andy Carlson||15/05/2021 22:10:36|
|387 forum posts|
Coincidentally... an interesting 'shop made' lathe with bed bars on eBay just now...
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