Thread: A Mini Lathe
I have done a fair amount of work on these mini lathes for a few people, mainly putting them right and adjusting them to run like a lathe should.
What you must realise with all these small lathes, no matter where they are bought from, that they do require a fair amount of stripping down, cleaning and reassembly, and that is even before you start to set them up to cut.
If you know what you are doing, allow a day to complete the setup, if you don't, then your guess is as good as mine.
If you are contemplating CNC, then there are a few pitfalls that would need to be sorted before even starting. The gibs are a nightmare, just strips of plate bolted on to hold the bits in position. The first job to give you the accuracy you require would be fit tapered gibs instead of the plate ones. This would require access to milling facilities and maybe surface grinding as well.
This is a post where I showed a very bad example of these lathes being put to rights, and it also shows how the new tapered gibs were done.
BTW, this was the worst case I ever came across, they are usually a lot better now. But still not perfect.
The Following User Says Thank You to bogstandard For This Useful Post:
Thats an impressive fix John, not sure I'd have the confidence to do that on my mill.
One of the reasons I am considering buying one is to aid in the restoration of my 90y old one primarily to make new leadscrew nuts and/or shafts - the lathe in its current state is just not accurate enough to do a bootstrapping exercise. However I don't want to spend a lot of time and effort making the new lathe work right... I have too many old ones that don't (yet)!
Your thoughts on how to approach these things is inspirational - to the extent of rethinking how I might rebore the bearings by hanging the bed vertically from the mill table instead of making up some form of spindle assembly. I also learnt a lot about tapered gibs and the making thereof. Now I have the dilemma of whether to consider making them for the old lathe or not... is it a restoration or refurbishment & improvement I want to do?! I am still trying to figure out what part of the bed/saddle/spindle 'moves' under cutting load to determine why it cuts inverse tapers.
I have 'fixed' over half a dozen of these machines from various suppliers, This was the worst ever, but all needed a little tweak to the main casting runners, most were no more than a couple of thou, but a couple needed 5 or 6 thou truing up.
With the gibs that come on these machines from whichever factory, those sorts of errors would preclude them from being used as CNC machines as is.
But as I showed, maybe not with that machine, but with a normal one, a good days work by a competent machinist can turn them into being a reasonably high precision machine.
With regards to your old machine, it all depends what you want it for, if it is for personal use, then I would have no qualms about bringing it up to modern day standards.
Leaving it restored to original standards, I doubt if it could be used in a workshop for any sort of accurate work.
Many years ago, I bought a badly damaged 1938 Atlas 10f. Most of it came in a big sack. By making and buying a few new parts, I got it running so that at least I could use it. Over the years, I gradually brought it up to modern day specs, and even the mighty Myford couldn't shine a light on it's accuracy and reliability. I used that lathe for many years, until it was replaced by the one I have now. I only replaced it because the Atlas just wasn't large enough for the jobs that were to be done.
It is now in the hands of a newish model engineer, and if it is looked after well (I threatened him when he took it), it will give another 70 years of good, accurate service.
Just because it is old, doesn't mean it is no good. If the castings are in good condition, you can end up with a small lathe that is better than any of the modern stuff. But you must be prepared to put the time and love into it.
Many thanks for that... its the words 'competent machinist' that gives me cause for concern I'm not sure i'm that yet - I can competently turn perfectly good blocks of alloy into something resembling wirewool and scrap...:heehee: but i am learning still.... you can see some of my 'learning' experiences on this thread... its the bigger brother of that lathe that I want to do a repour and bore out on, as discussed in post 73 onward of that thread - I'd be interested in your opinion on the best way to approach the problem...
I read your post all the way thru, without looking at the second link you gave. I got to the 7th page and started to think to myself, how would they have done the lathe when first made. It then occured to me that at the factory, they most probably just bolted a drilling head to the slideways (where the tailstock fitted) and then just drilled and reamed the head, most probably with some sort of manually turned drill.
Just the same sort of conclusions you came to from page 8 onwards.
I don't think the offset holes in the bearing shells is that important. The castings were most probably so badly twisted, the pre cast holes for the shells were just filled up solid with white metal and then drilled, they just turned out the way they did for no other reason. As long as the tailstock and leadscrew were in line with the spindle, that was all that would be required. The bearings would most probably then be hand scraped and clamped up to get everything corrected. Near enough was most probably good enough in those days.
You will notice, that a lot of lathes in this era had bolt down headstocks, most probably to allow the head to be put in a more central position before drilling. I did the same sort of fix on my old Myford ML2/3, but I actually fitted very finely turned bronze bushes, and repositioned and shimmed the head until everything was perfectly in line. My friend still uses that lathe in his small shop, and it still runs perfectly true after over 20 years.
If I was to do your old lathe, I would have gone the way of bronze bushes, just locked in with an anti rotation pin, then drilled or bored from the tailstock position.
The back bearing casting of the Myford also broke in roughly the same way as the other lathe you showed, and I got around that by machining the whole top half away, and bolted a new top piece on, made from steel. I never did paint it and cover it up, and if I get the chance, I will go down and take a picture for you to study, it just might solve that problem for you.
It is a real shame you live so far away, we could have had it machined up in no time.
Why are all the good bargains on eBay always at the wrong end of the country?
The more I look the more I am not sure..
I could spend £400 on a new minilathe from Hugh in East London and collect it myself to save the £45 carriage.. or the same on a 1950's Boxford BUD/CUD or a less well preserved A/AUD or about the same on a Denford Viceroy TDS or similar... and it'll cost me £100 carrier or van hire to go get it... with the possibility the eBay one turns out to be a load of crud.. then again so could the minilathe.. I just read the Arctools preparation guides for the C3 - its quite extensive re-engineering of some parts not including replacing the main bearings!
I nearly won a Hobbymat - yes I know its a tad small but it would do to make the new leadscrew nuts and leadscrews for the big lathe so that could be used - and it was literally just up the road from me but just as it was about to go for a reasonable sum some idiot lept in an bid way over the top for it...
Have you looked at a ready made cnc mini lathe, I have a few denford starturn lathes and a couple of Boxford slant beds that i am converting to mach3.
The Starturns are much more sturdy than a standard mini lathe and have been hardly used, and the Boxfords are amazingly sturdy being slant beds. This would save you a lot of work and give you very good accuracy off the shelf.
I've looked at a lot of things... its finding something in my price range that isnt going to cost as much again to get it home thats proving the problem... the last one on eBay went for over £1000 and a Orac went for nearly £700 earlier this week...and thats before shipping...
Of course if you have one at a sensible price...
i went to see that orac as it was close to me, and I wouldn't have paid that much for it. The Starturns i have will be around £400+ mark, and could be delivered at cost.
That's with a computer and flat screen monitor, with a demo version of mach3 setup and ready to use.
By fragger6662000 in forum Milling Machines, Builds & ConversionsReplies: 2Last Post: 15-11-2011, 06:13 PM
FOR SALE: Sieg C3 Mini LatheBy Jonathan in forum Items For SaleReplies: 1Last Post: 07-05-2011, 05:19 PM
By GeorgeD in forum Lathes, Lathe Rebuilding & ConversionsReplies: 7Last Post: 28-07-2010, 09:00 AM
WANTED: SIEG C3 Mini LatheBy derekm in forum Items WantedReplies: 5Last Post: 07-04-2010, 07:35 PM
By pequod in forum Lathes, Lathe Rebuilding & ConversionsReplies: 2Last Post: 29-06-2009, 05:40 PM