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Mini lathe help
JeffHs - 6/4/20 at 11:45 AM

I've been tuning up my Clarke CL300 and due to improper adjustment (that's a polite way of saying I'm a pillock), I have cracked and need to replace the saddle shear plates(retaining plates). They are flat plates 100 x 20 x 6 and would be very easy to duplicate with bright steel bar, but the question is:
Why were the originals made from cast iron?
Would steel be OK? Would steel allow the saddle to slide freely without damaging the underside of the bed, or should I try to find iron ones?

David Jenkins - 6/4/20 at 12:23 PM

I would guess that they were cast iron for various reasons:


  1. Cheapness - a Chinese sub-manufacturer can make fancy blanks very cheaply, I suspect. These would be machined to size.
  2. Iron is very stable, and is unlikely to warp or otherwise change shape, once it's 'matured' a bit.
  3. Cast iron is quite a 'slippery' material due to the carbon granules within it, especially if it's running against another cast iron surface.

If you used steel you'd have to consider the material it was running against - the bed is probably cast iron, which may wear if there is a mis-match on materials. Saying that, my ancient lathe uses steel gib strips (used to adjust and take up slack) running against the cast iron bed, so it should be OK.

Are the broken bits precision items? If so, it might be an idea to use steel gauge plate, which has a precise thickness - easy to get hold of by mail order, but the price might make your eyes water a bit! (it's not too silly a price). If you're feeling really flash, you could consider bronze, but then you'd really need a good bank balance!

Post a picture of the broken parts - we might understand the problem a bit better...

rj - 6/4/20 at 03:44 PM

Steel should be fine, both of my lathes (Myford 7 & Weiler Condor) both have steel gibs running on cast iron beds, suspect the originals are cast iron for cheapness

paulf - 7/4/20 at 11:14 AM

Most machine tools tend too have steel gib strips running on iron bed ways, just keep them well lubricated when in use and after use flood with oil and work the slides backwards and forwards to spread the oil if not using for a while.There are special slide way oils but cheap engine oil works fine for home use.
Paul.

trextr7monkey - 7/4/20 at 06:49 PM

I agree with what is sai above it’s quite a small machine so we are not dealing with massive forces. Plenty of lubrication will help it last for years. I have had loads of old Myf and Drummonds several more than 100 years old not showing much wear at all, but all have lived their lives dropping g in oil.
I use air compressor oil for oiling my lathe as it’s pretty thin and is regularly replaced.
Atb
Miley

JeffHs - 7/4/20 at 07:57 PM

Thanks guys
I've found a source for genuine replacements - Arc Euro Trade , but they're closed for lockdown, so I'll knock up some steel ones.

After scouring the web, it seems there's a general consensus that the mini lathe saddle is a crap design. There's loads of stuff on there about modifying it. So I'll see how the steel ones fare and then maybe tear the whole thing down and re-engineer it. It's not as though I'm going anywhere soon.

Can't post pictures at present. The site seems to think jpegs are an unsupported file type?

Jeff

suzcruz - 7/4/20 at 10:02 PM

Dont use steel, use brass strip.
Why? Chinese castings very low quality like cheap brake discs.
Those old lathes myford, hercus, norton were using premium castings.