Fixing the Mini Lathe Saddle - Flattening the Ski Jump - Part 4
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- Опубликовано: 11 окт 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 looked 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.
In part 2 we identified a problem with the alignment of the saddle bed ways which we need to sort out before we can move onto the actual gib strips.
In part 3 we refined the saddle gibs themselves and started to re-assemble the lathe. Optimism for a swift conclusion of the problem was high, yet premature.
Here in part 4 we're addressing a bend in the lathe bed and are once more taking to the hand scraper to fix the problems that came out of the factory.
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.
See part #1 here - • Fixing the Mini Lathe ...
See part #2 here - • Fixing the Mini Lathe ...
See part #3 here - • Fixing the Mini Lathe ...
Handy Links
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Carbide Hand Scrapers - ebay.us/uKTQmc
Carbide Scraper Inserts - ebay.us/FZUxmO
Engineers Blue - amzn.to/3XoBMSM
Rubber Roller - ebay.us/RMBsyo
Surface Plate - ebay.us/2yrNIh
Slip Stone - amzn.to/4d8aJB8
I have thoroughly enjoyed the videos you’ve posted on improving your minilathe. The idea of using tools commonly available in the home shop to bring more precision to a Chinese metal lathe resonates with me. I am very eager to see how to straighten the lathe bedways with a straightedge or flat surface that is shorter than the ways themselves. I’m here to learn, thank you for teaching!
Thanks Ken, I'm glad you're enjoying it!
Thanks for returning to this Sir been waiting for the follow up. I using watch your tutorials in the early morning. Right now it's 2:43 in American Canyon USA which is in Napa County. Look forward to this tutorial and future ones. Hope you'll be able to get a Mini Mill in the near Future. So many up grades you can make to these also . Thanks again I'll be watching this one while my daughter makes dinner to night.😊
Thanks for checking in - I hope you enjoy it! The next one should follow quite quickly now. Would love to get a mini mill, but I might have an option on a mini hand powered planer/shaper which would be a really fun and useful addition to the shop. Will upload a video if I manage to secure it 👍
Great episode, as you have gone that far I would scrape the whole bed for oil retention, improved sliding all over 😁
Thanks Russell, good idea 👍
There is a technique in Metrology called the reversal method. Technically you can use it to get a measurement of any surface without having a reference flat surface. Realistically you need a sturdy, flat enough surfaces that won't flex under the weight of what you're trying to measure, or flex under your measurement tool.
The TLDR of it is if your gauge follows a set path, let's call it surface A, and follows that path to measure surface B, you get your set of reference points that measure the distance from A to B. But then you flip that surface upside down, and measure to the exact same points on surface B, following the same path on surface A, so that the correlation between the distances from A to B are maintained. But because you flipped surface B, you now get the inverse of the measurement from A to B. With that, you can make a simple equation that solves for surface A, then knowing surface A you can solve for surface B.
It's a bit of algebra and a little hard to explain, but it's an extremely powerful tool that is very common in machining to take the error out of measurements.
Thanks for sharing the technique Stephanie, interesting 👍 Although it sound like it would be tricky to flip surface B without it changing position in space.
@@radboogie a change in position is okay, even a tilt can be calculated out, but what needs to stay the same is the reference from A to B at the same points. The simplest method would be to add a guide for surface A, like a straightedge or a straight piece of steel, and to mark the start and stop points on surface B, and just align it. Since you're not chasing angstroms or anything, getting close enough will give you something useful. I've thought about mounting a linear rail to a cheap piece of granite countertop for this purpose.
Check out the video by Dan Gelbart on the building prototypes, #17 ruclips.net/video/cwdoUjynpEk/видео.html
If you haven't watched his videos, they're stuffed with so much engineering knowledge that's easy to understand.
Interesting comment, I'm going to look into this!
I was very interested in this topic as I have done some work on the retaining strips as well. I also found the same binding issue near the tail end of the ways. I really enjoy your practical approach to investigating and resolving these issues. I am very interested to see what you come up with in the next episode.
Thanks Thomas, I'm glad you like the videos. Interesting that you also have the binding problem, sounds like the factory has a problem with their grinding machine! Not long now and the next part will be out.
I have the EXACT same lathe except with metal gears and have had all the same problems and more with mine. I’ve learned to live with it that binding on the ways since I don’t move the carriage that far to the right.
Great vids. Thanks for sharing. Improvise, adapt, & overcome.
Thanks for watching!
How could we find some hardened steel plate to mount on the bed so all the problems because cast iron can be solved.
I take it you are going to use your flattened plane as a straight edge.
🤜🤛
@@radboogie well it does have easy to use handles and a flat surface.🙂
order and sequence, ...
Richard, you should take care of the lathe bed guides first and then deal with the lathe saddle problems.
Ideally yes. But the aim here is to get a useable lathe with the minimum of work, so the strategy is easiest fix first not ground up restoration.
You realize that anybody who sees this bed without having watched the video is going to have a serious WTF moment - "Why would they hand scrape the end of the bed that the saddle DOESN"T ride on?!?!"
😂
But the tailstock does.
Sorry but the real problem is the underside of the rear way & that’s why it was only the rear was binding
I had the very same problem with my Chinese thing of never ending joy
oooh, gentleman, you open a can of worms for yourself 😅
in theory, you also have to consider the height of the center of the chuck to the rail, to the height of the live center in tail stock to the rail. it had to be the same height to prove parallel. otherwise, if the rail bed is not parallel to the chuck spindle, you still got a taper. no matter how smooth the rail is.....
the rail under the chuck, suppose to be no worn out. the end of the rail where the tail stock sit also have no worn out. the difficult part is, it is always a u shape because of wear and tear in the middle.
i would have a humble suggestion, you also check the height the between the chuck spindle to the rail before further processing the rail.