New 4" Backplate For NovaTurn Will Not Fit

[cskipper]

I had a new 4 inch backplate machined and it will not fit the spindle taper! I used the taper dimensions from the ST5/108 drawing!

I am replacing a pneumatic chuck made by MicroCentric model 4-120-3 with a Pratt model 9580-01005 100mm chuck size.

Did Denford or MicroCentric make the backplate? Did Denford use a special or different taper for the MicroCentric chuck?

Is there a drawing with dimensions for the chuck mounting area of the spindle?

Find attached pictures! The DSCN0398 is with the MicroCentric backplate mounted.

Carl

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Added pictures of new chuck back on lathe. One shows that I now am down to .014" gap on the back and the other shows the new back mounted!

Carl

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Added model view of dimensions to enlarge the taper thru hole. At .011 gap at this time!

Carl

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5-6-2022
Down to .003". Will put a chamfer on the corner and check that out!

Carl

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5-26-2022
The Pratt 100mm chuck mounted with .0002 TIR.

Carl