Smithy 1220 taper

M

mac1911

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Have had this lathe a bit over a year and maybe 40 hours total of actual use. Most of which has been fixing and tweaking the lath.

Taper was awful when I got the machine and has improved with some cleaning , tightening , measuring and help from members here.

Today I was bored and braved the cold 22’F temp of the “shop”
Found a piece if scrap 6” long 15/16 or so in dia , un known steel.

4” stick out did a few light cleaning passes. Then a .002” light cut

Max speed of my lathe is 1600 rpm
Gear set up for .003” on L and .006” on H
Carbide insert tool with new tip

Finish was improvement over some 1BFC2BE5-1ECF-4E1D-BB04-F9CEC916868C.jpegimage.jpgpast attempts .
With my measuring abilities I came up with .0008” taper over 4”
Much better than past attempts and rook a bit of work to improve.
Not sure if I should chase this any more.

Next is better tail stock alignment.
I thought I had it aligned pretty well but turned a 12” long piece and had .010” which I thought was to much and I already made the part it was supposed to fit in. Vs fitting that part to the shaft. It was not critical by any means but sucked one end fit great and the other not so much.
 
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That's a lot of taper over 4". Have you attempted to level (remove twist) from lathe?
 
ShagDog said:
That's a lot of taper over 4". Have you attempted to level (remove twist) from lathe?
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Been attempting it here and there all summer. I only get short intervals to get to the lathe.
Im at the point I dont know if the gear head is still canted or its in the ways?
When I first picked up the lathe is was pretty badly aligned. Had lots of vibration and chatter along with a really bad taper.
Not until I got a copy of the parts diagram did I find the screws and pins securing the gear head to the bed where loose. Parts 69 and 70. Not shown they are hidden behind electrical panel
Im at a point I think I need something better than a .001”
To do better and a level to proof out the ways.?
 
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mac1911 said:
Is it a lot over all or a lot for this level of machine?
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It is a lot over all, at least for me.

Edit: not too bad actually. I made a mistake in reading the measurements and came up with a significant taper. See my pot below (post # 19)
 
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I haven’t tried this with my smithy yet, but I do know the 3 jaw on my smithy has less runout than the 3 jaw on my south bend. I probably just got lucky with that.
 
Tincamp67 said:
I haven’t tried this with my smithy yet, but I do know the 3 jaw on my smithy has less runout than the 3 jaw on my south bend. I probably just got lucky with that.
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If I put my 001” indicator on the body of my chuck its under .001”
I have not tried placing any know good quality straight stock in the jaws to check run out.
I also need to get face plate and dogs to tey running between centers
 
To turn between centers when you only have a 3 jaw chuck , just chuck a piece of round stock up. Then turn a 60 point on it. If not removed from the chuck the home made center is perfectly centered to the spindle of the lathe. A drive dog will still be needed. The bent arm will drive off the side of the jaw.
 
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