I have a 4-jaw to mount on a D1-3 backplate.
The chuck came with a threaded backplate, that seems a little unusual.
It appears to be 'about' 2 1/4" x 3 mm.
All the threaded holes are 3/8" x 16 tpi.
To test the measurement I made up a dummy cast iron spindle register and mounted the backplate.
I started with OD 57.1 mm (2.249 "), 3 mm pitch and a carbide tool.
Progressively reduced diameter, recutting the thread as I went, until the backplate slipped on nicely and tightened up on the (very small) shoulder.
The feel of the fit is close to what I remember when mounting chucks on my Sheraton 9A.
The final values were:
- OD 55.4 mm 2.18",
- Thread pitch 3.0 mm,
- Thread depth 1.9 mm 0.0748".
The TIR is difficult to measure as there is no circular track available for the DTI, but my limited observation is that it is quite good.
The photos show the situation.
Note the threaded holes breaking into the periphery.
Now that I have done the job, it is tempting to make up a steel version to use this backplate as a mini-faceplate mounted on the 4-jaw.
(I cannot use this CI component because it shows the typical longitudinal cracks of stock sourced from the TAFE scrap bin)
Backplate 4-jaw.JPGTest Register 4-Jaw.JPG
If someone can identify the true thread details, and can make use of the backplate, happy to dispose of it at mates rates.
John.
The chuck came with a threaded backplate, that seems a little unusual.
It appears to be 'about' 2 1/4" x 3 mm.
All the threaded holes are 3/8" x 16 tpi.
To test the measurement I made up a dummy cast iron spindle register and mounted the backplate.
I started with OD 57.1 mm (2.249 "), 3 mm pitch and a carbide tool.
Progressively reduced diameter, recutting the thread as I went, until the backplate slipped on nicely and tightened up on the (very small) shoulder.
The feel of the fit is close to what I remember when mounting chucks on my Sheraton 9A.
The final values were:
- OD 55.4 mm 2.18",
- Thread pitch 3.0 mm,
- Thread depth 1.9 mm 0.0748".
The TIR is difficult to measure as there is no circular track available for the DTI, but my limited observation is that it is quite good.
The photos show the situation.
Note the threaded holes breaking into the periphery.
Now that I have done the job, it is tempting to make up a steel version to use this backplate as a mini-faceplate mounted on the 4-jaw.
(I cannot use this CI component because it shows the typical longitudinal cracks of stock sourced from the TAFE scrap bin)
Backplate 4-jaw.JPGTest Register 4-Jaw.JPG
If someone can identify the true thread details, and can make use of the backplate, happy to dispose of it at mates rates.
John.
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