Mini lathe saddle ways are convex?

Oh, and my saddle ways are definitely convex like I thought. The straightedges rock on them. :-/
 
Have you used your lathe and these divergences from ideal caused you headaches or prevented you from hitting dimensions?

The reason I ask is that it's easy for us beginners to get caught up in watching YouTube videos where people apparently turn their Chinese mini lathes into mountain-range-immovable machines of ultimate precision. It's the hobby-machinist version of unrealistic body images on social media. :grin:

You have a Chinese mini lathe like I do. There's a lot you can do to improve them and learn and have fun in the process but it'll be even more fun to have an assembled machine and make some chips. ;)
 
My facing surface finishes have been good with the carriage locked, but my turning finishes have always been terrible.
 
KKrum said:
My facing surface finishes have been good with the carriage locked, but my turning finishes have always been terrible
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Well, a rockin' and rollin' cross feed could cause that I guess but there are quite a few other causes of bad finish (most of them 'pilot error' and I reckon I'm pretty expert in all of 'em! :grin:).
 
More experiments. With the saddle clamped more firmly to the front way than it would ever normally be, using c-clamps carefully aligned over the top of the prismatic way, the back of the saddle floats .010 off the back way. With the front bottom clamping piece installed just finger tight so the saddle doesn't have vertical play but can still slide, the back makes slight contact on the left and floats .005 on the right. But because of the taper in the ways, the saddle can only move about half the length of the bed before it binds up. Also, the bottom surface of the saddle is above the bottom of the way, so the clamp is angled and not making solid contact with the bottom of the way. With c-clamps forcing the clamping piece into contact with the bottom of the way, there's about a .020 gap between the saddle and clamp. The feeler gauge drags a little more on the left, corresponding to the way being thinner toward the headstock.

I think I have to fix the taper in the ways. I'll do that first and see how everything else falls into place.
 
I found a replacement saddle on AliExpress, surprisingly cheap compared to other parts of my lathe and saddles for other lathes. Maybe the problem was widespread and they made a lot of spares. Or maybe they're selling off the defective ones. But now I know what to look for. If I can fix the thickness taper in the bed ways, it'll be like having a whole new machine.
 
KKrum said:
I found a replacement saddle on AliExpress, surprisingly cheap compared to other parts of my lathe and saddles for other lathes. Maybe the problem was widespread and they made a lot of spares. Or maybe they're selling off the defective ones. But now I know what to look for. If I can fix the thickness taper in the bed ways, it'll be like having a whole new machine.
Click to expand...
Looking forward to the aliexpress results
 
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