On 2010-03-03, Louis Ohland wrote:
I am trying to get a chuck to mount on my G9972Z 11x26 lathe. After
using thread wires, I think 1 3/4 x 8 tpi is pretty damn close.

Hmm ... the Grizzley is made in China so it is more likely to be
a metric thread. Converting 8 tpi to metric comes out as 3.18mm pitch,
so could it be either 3.00 mm or 3.25 mm (or perhaps 3.20 mm).

I believe that the only one of these which is actually imperial
threads as sold is the Jet -- in which the original threads are turned
off the spindle, a sleeve heat shrunk onto it, and the imperial thread
is turned on the spindle sleeve using the thread gearing of the actual
lathe so it is possible to cut the spindle thread into a blank
backplate.

To me, the measurements look like the bolt holes more or less incline
towards the outside of the chuck .035 to .050, then we expect the poor
mounting bolt to flex back a bit to meet the adapter plate's bolt
circle. This chuck is supposed to adjust akin to a Set-Tru, yet the
mounting bolt heads are an interference fit against the outer edge of
the counterbore. It does not move about the hub when the bolts are
started. Perhaps I am too perfectionist, but this is not what I expect
of a US made chuck.

Who made the chuck? If it came with the Grizzley, it is likely
not US made -- just as the Grizzley is not US made.

Dimensions converted to metric in your table below.

Chuck Chuck Adapter
(Top) (Bottom)
4.454 113.13mm 4.487 113.97mm 4.470 113.54mm
4.451 113.06mm 4.504 114.40mm 4.470 113.54mm
4.454 113.13mm 4.484 113.89mm 4.468 113.49mm

From the measurements, the bolt circle at the top of the chuck is @
4.501+, the bolt circle at the bottom of the chuck is 4.485+, and the
adapter bolt circle is 4.470-.

Hmm ... 113mm, 114mm and 113.5mm would be the metric figures,
which seem to make a bit more sense -- though they are still wrong for
the task.

Adapter plate screws onto spindle from either side about three threads,
then stops. At first glance, the spindle threads are pretty close to 1
3/4 x 8 tpi.

Almost certainly a metric spindle thread. Do you have a set of
metric thread pitch gauges? The diameter (1-3/4) works out as about
44.45mm, and the thread pitch as 3.18mm (likely 3.2mm).

Hmm ... the downloadable spec sheet does *say* 1-3/4 x 8, but
I'm not sure that I trust it.

It does say "Country of origin: China", and they list the
following chucks:

5" 3-Jaw Chuck with Two Sets of Jaws
6-1/2" 4-Jaw Chuck with Reversible Jaws

Are these the ones in question, or did you get a chuck from another
source?

O.K. The manual also says 1-3/4x8 spindle. So, perhaps the
problem is in the chuck backplate.

Good Luck,
DoN.

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