Ongoing SB renovations - mistaken change wheels - if not SB, then what?


Rob Kovacs <rnkjma@...>
 

Hi, All,

After several months of being away from home, I am back and getting on
with renovating my couple of SB 9 inche lathes. I have come up with
several questions about parts, sub-assemblies and
re-building/aligning/calibrating the lathe when they are finally
re-assembled, but as they are still in the soaking-and-painting stage,
I will leave that till later...

The question that I have relates to a couple of change wheels that I
bought off eBay from a guy in Scotland. I already have
two-and-three-quarters complete SB nine inch lathes, with about 20 or
more change wheels between them. All the change wheels match each
other perfecrly, and most of them were fitted to the lathe spindles
when I picked them up from previous owners. Additionally, I have
checked the sizes and arithmetic on the tooth DP's (18DP on SB's),
just to convince myself that the numbers work, and work out centre
ditances, etc.

This guy in Scotland is breaking a SB nine inch lathe. He advertised
these change wheels along with other nine-inch parts that I
recognised, so I (wrongly) assumed that they would actually be SB
change wheels. I bought them, but when I got them delivered, I found
that they were not the same tooth pattern as a SB nine-inch, so are no
use to me. I have not decided what to do with them yet (...might sell
them on eBay), but before I can make a decision, I need to identify
them. If I sell them on eBay, they will need to be correctly listed as
what they REALLY are...

Here's what I have:-

127 tooth (Metric transposition!) gear, measuring 205mm (8.071")
accross the outside of the diameter over the teeth. (i.e. the maximum
diameter, tooth tip to the diametrically opposite tooth tip, NOT the PCD)

70 tooth wheel, measuring 115mm (4.528") over he outside daimeter of
the teeth, measured as above.

By my calculations, that makes them 16DP, as :-

DP value = (tooth count + 2)/overall diameter in inches

DP value = (127+2)/8.071 = 15.98

and

DP value = (70+2)/4.5276 = 15.90

Both of these numbers approximate to 16 DP, and the teeth are bigger
than the others in my SB collection. In addition, the bore hole
through the centre of these wheels is within a thou of 0.750", with a
similar type of keyway to the SB gears. Also, the casting are marked
with some lettering. The 127 tooth wheel has the legend AM233 cast
into the original blank, and the 70 tooth wheel has the legens AM227
cast into it.

Can anyone help to identify these change wheels for me? What machine
are they from? What are they worth? More or less than SB wheels of the
same size?

Any info or advice would be welcomed at this stage. I STILL don't have
a useable 127 SB metric transposition gear! Actually, I don't have a
working lathe yet, just a garage full of stripped-down dirty bits in
soak, and an oven full of bits with paint curing...

Many thanks,

Rob

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