Fixing the Mini Lathe Saddle - Hand Scraping - Part 1
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- Опубліковано 19 чер 2024
- Continuing to tune up the Chinese Mini Lathe, next job to look at is the lathe saddle.
I have had a lot of problems with surface finish and the tool cutting on the outfeed. In this series we're working through the various problems with the lathe saddle as it came out of the factory and working out how to improve its accuracy and rigidity.
In part 1 we look at the problem, take some measurements and start to hand scrape the bearing surfaces of the saddle in order to start to bring it into truth.
The fix applies to the following lathe models: CJ0618, Crenex 7"x14", Clarke CL300M, Warco Mini lathe, Sieg C2 and many other brands which are based off the Chinese mini lathe design. However the techniques could be applied to other makes, models and sizes of lathe and aren't limited to this particular model. - Навчання та стиль
Now that was funny when you transitioned from tapping to Morse Code to SOS “my lathes in trouble, please send help”. I actually burst out laughing. I’ve been there with stuff that’s just so screwed up all you can do is make a joke and laugh.
With a mini lathe, if you don't laugh you'd cry 😂
I stoned mine... took all the mill marks out that aren't supposed to be there and it helped a ton.
Nice job Richard , takes a while to do but it,s worth all the effort, good for you mate
Regards
Mike
Cheers Mike 👍
About the studs, if the torque you give to the studs or to the nuts where over the elastic limits or the force applied during work is over the limit, then definitely will stretch. If you remember, olds cars had to go back to the dealer after several miles, to "retie". After 1975, with the torque and angle control does not need.
Nylock nuts are not reliable. You either need to double nut the studs and jam them together or add jack screws ao you can tighten the nuts to the plate like you mentioned earlier.
I've recently embarked on a project to build an air bearing, and you have provided a heep of info on achieving precision without extremely expensive equipment like precision grinders.
Nice one! I am continually amazed as to the incredible tolerances that can be achieved with little more than a block of stone, a sharp metal stick and some "oil paint" 👍
@@radboogie I did have a question about hand scraping, could you use a steel chisel as a scraper or is there a flaw in that thinking.
It really depends on how hard the chisel is. If it's hardened steel you could grind the end to a 60mm radius with a 5 degree negative rake (95 degree angle) and it would work. You could also do the same with an old file.
Nice start on the tail chasing I have to say. Been there, not quite happy with what I wound up still.
I went to brass gibs and studs for the carriage , wound up shimming them.
The thing still doesn't sit level from front to back. This is going to wind up being a big project I predict...
Best of luck.
Thanks mate, I think tail chasing sums it up perfectly 👍
BTW, I subscribed.
How does the saddle being level with the bed ways effect cutting? Hw do you level the saddle out?
If the saddle isn't level it's not too much of a problem, all will mean is that the tool height might be slightly off depending on how far in you wind the cross slide. For me it was more that I needed a flat reference surface to fix the geometry of the saddle gib contact faces.
Found your channel through plane scraping video. Really enjoying the do it right mentality.
It's possible the studs have stretched or the gib has wore due to small contact area. But: Nylon lock nuts don't really hold very well in vibrating conditions. They will back out until loose and stop. Proper way to go is to shim the gibs and torque the nuts. Of course nyloc won't hurt anything.
Thanks for the info. I'll see how they hold, the number of times they've been on and off already means the nylon has worn out and they need replacing with new. The gibs have been shimmed, if the Nylocs don't hold I could try two plain nuts on each stud locked against each other. 👍
Hi, total lathe newbie here, got mine last week so please forgive for any inaccuracy on my side, I'm still on the steep part of the learning curve 😬
I went straight for the carbide tools right from the start, thinking they were more practical (no sharpening, replaceable, consistent cutting) but now I get they are less effective in cutting compared to HSS...
So I followed attentively the part where you explain the "push back" effect due to the forces applied to the not-so-sharp carbide insert and the resulting spring effect.
My question is: besides the imperative quest for increasing the overall rigidity and eliminating plays, could a slower cutting feed help to alleviate this undesired effect, by giving the tool "more time" to chew into the piece and thus allowing the spring tension to relieve?
Welcome to the wonderful World of turning 👍
Slower feed and shallower cuts would reduce the spring problem but carbide tools are designed to be run at high speed with deep cuts so they aren't very well suited to small lathes.
You can buy "positive rake" carbide inserts that are designed for cutting aluminium. These have a sharper point and a greater rake angle which (so I am told) makes them better suited for cutting steel on small lathes due to the reduced tool pressure. Might be worth a try.
@@radboogie
Hi Richard, and thanks for confirming!
And yes, after looking around I got that positive rake insert were the best compromise, and in fact all inserts I have are of that kind.
I'm still in the "tuning" phase, since the machine arrived in very poor adjustment conditions, but luckily it seems that, after a whole day of fiddling around I got a better response from all the commands, with smooth enough movements and small play.
The first tests (aluminum and brass rods) have a very shiny and smooth appearance and feel, both lengthwise and face cuts, so I'm very happy for now, since I will probably stick with softer metals for a while, before doing the steel test.
Still a lot to learn but with patience, curiosity and the precious help of video tutorials like yours, I feel more confident and in good company 😀
Thanks again, keep up the good work and greetings from Italy!
Roberto
Good luck Roberto 👍
@@radboogie problem with those brittle sharp for-aluminium inserts on a springy / loose mini-lathe will be that they tend to break very easily IMHO
Oh jeeze louise... I was just filming my own baby lathe from back in the days when Yugoslavia was a kingdom of sibling nations... I don`t know how large you lathe is, but my baby is around this size if my eyes do not deceive me... She is 70kg(150lbs) of iron and bearings, plus another 30kg of bench and pulleys and motor, but that doesn`t count as the lathe... Nonetheless, i had to machine down an engine head bolt down to make a retention pin for my winch... The factory original 4.8 bolt sheared and shot into my wrist some months ago... I decided to upgrade the hardware to some proper alloy, not 4.8 crap... Long story short, i had to turn down M10x1.5 thread down to 8mm, which gave me 1.5mm of thread depth, or interrupted cut work, and 0.5mm of solid rod work thereafter... I done did some terror in chucking the furthermost bit of the bolt head flange, and supporting it from the rear with a center, so the finish was terrible, like proper terrible, thankfully i smudged the lens with oil at a certain point, so the finish nightmares are not really visible anyway... Long story short, that little baby lathe of mine can actually cut some decent cuts, 0.5 radial, or 1mm diametral cut, even more when roughing, but i keep it civilized, i love my machines, so spending more time with them through shallower cuts doesn`t pain me, but this what you took as a deep cut appears to be no deeper than .3mm diametral d.o.c. am i wrong? That is quite shallow, even for a mini lathe... Or is my standard just a result of an old properly made little beast of a machine? Also, she has 0.25kw motor, 3phase, but 0.25kw - I`ve seen sex toys with stronger motors than that...
I would seriously consider making a full lathe revamp, adding machined steel braces in the bed hollow, drilling into the carriage and the cross-slide if possible and differential cooling fitting carbide rods into them to beef up the components... Using a thick plate to mount the lathe onto after match scraping and lapping the feet and the plate in for a leveled, rigid fit... Maybe fabricating a frame-brace for the headstock aswell... There is always stuff that can be added onto or made a part of a machine, as to add immense rigidity to the already existing body... I would get a high tensile bolt, something big, and turn that down to hold the toolpost, actually, just swap out all the fasteners for high tensile 12.9s... Make a brass, rulon/turcite faced gib for the compound and the carriage, and have those snug, like 0.01mm of play at max... Add some injection oilers and that should wipe out most of your play, because .5mm of total possible oscillation is ridiculous... I have done almost nothing with my baby lathe, and i can barely get 0.04mm of play in the toolpost, and while it is just a good old 4way slab, it can`t account for too much if the rest of the system were fucked like you have shown here... Like damn, 0.5mm... Whoever made that poor little lathe deserves to fall into a bin of mill formed climb cut chips... It`s like they just slapped the parts on and called the job good enough... She deserved better... Glad that she found the way to your doorstep...
Edit - Looking at the cross-slide carriage half, the feedscrew is unsupported on the rear, you should mill that square out, turn the screw down a bit, and use a bushing or a bearing of some sort to support that... If you do a good job, that alone could take out some free play, as with just one side supported, i would bet they didn`t even really preload the screw to any level, as it`s hard to do so with one bearing only... Just make a little bit of square metal, go grab a scrapped vehicular wheel arm from your local mechanic, you will find one that is cast iron and big enough to extract that little square chunk outta it... Vehicle cast iron is great, but it`s always in shit shapes and has reduced sections as to make it as light as possible, so you won`t be able to use it for much, but some great iron for small projects can be had from such parts of a car or larger vehicles... Older vehicles especially...
Regarding the carriage anti-lift gibs, you could mill the carriage slanted where the gib rests, and mill the gib slanted aswell where it touches the carriage, then slotting the holes slightly and tapping a little screw into the side of the carriage, axially aligned to the spindle axis, which would give you an ``adjustable parallel`` type of gib actuation, allowing you to tighten the gib as much as you want(within a certain range), while maintaining parallelism with the bed`s underside flat part of the ways... Shimming works, but not as well if all is well done... You could also put rulon or turcite on that parallel section of the gib if you want to remake the gib from thicker material...
All the best and kind regards!
Steuss
Thanks for the great comment Steuss - interesting to hear your story. I believe my lathe was assembled from reject parts and bits that were found in the dumpster outside the back of the lathe factory. Was branded as "Crenex" which I reckon is a make believe brand used to sell scrap parts on eBay. Having said that, I only paid £375 GBP for the lathe as new including shipping so am grateful to have got such a great entry price. Fixing all the errors is good fun and I hope the videos provide some interest and entertainment. Am hoping to get the thing running accurately and smoothly, in the meantime will save up for a grown up size lathe like a Colchester or a Harris for when I need to do heavier work. All the best - Richard 👍
@@radboogie Oh, the Colchester, lovely... Harris lathes are also great, but they are more known to me for their box-ish style design, and i prefer the oldies with a lot of curvature(the worst for any restoration or modifications)... My machines are all at least 40 years old, so they aren`t really comparable with the new stuff...
I get your point of snagging the lathe for pennies, tho, what with the nature of cheap imports being what it is, i would argue that it`s better to gamble on an old machine and contend with the wear as one learns how to do so, than getting a cheap import with no wear but shit geometry nonetheless... Old machines may be worn, but there are always some near virgin reference surfaces that were done with care and dedication, making them a great starting or a reference point for any restoration or similar wear blueprinting and sanation... Tho, the new machine does have the benefit of often coming with the full set of hardware and ancillaries, whereas the oldies oft come barren and lacking a lot of original equipment that is mad costly to obtain individually... I got my deckel s1 t&c grinder for pennies, and i wanted to get an array of oem dust shields for the stones... A 3 piece dust shield set costs more than i paid for the machine... Ridiculous...
I gladly await your new acquisitions, you just got a new subscriber!
Best regards!
Steuss
Very true - real machines have curves! When I was an apprentice in the 80s we had a selection of older Bridgeport and brand new Ajax mills. As youngsters we used to flock around the new Ajax's with their angular lines and smart grey paint. Our instructors always advised us to use the older machines as they were nicely bedded in and smoother to operate. How right they were!
You were getting an automatic spring pass before you fixed it. 😂
😂
That’s why I didn’t bought a mini lathe. Their are cheap but mostly not useable in their shipped state.
And good small lathes are rather expensive.
Maybe the branded ones go through better QA than the dog that I ended up with... Saying that, even with this "pile of spares" there's a decent little lathe in there trying to get out. Buying at this end of the market is certainly a lottery and you have to enjoy fixing the problems if you do. Cheers 👍
SOS?
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