# threaded chuck adapters - confusion...



## jumps (11 Jan 2012)

in an effort to make use of the delivered chuck and jaws (rather than give up and return them - see thread on dakota X450) I have tried to establish exactly what the underlying chuck threads are to give me the widest choice of alternatives.

using somewhat rudimentary measuring devices it would seem that the narrow part of the female thread is 1 3/8" and the widest part just over 1 1/2". It's clearly 8 TPI rather than a 3.5mm pitch.

the male dimesions of the the supplied insert are easier to measure and are 33.5/37.5mm which are just slightly below the above dimensions.

would I be right to conclude that this represents a 1 1/2" x 8tpi thread?

is there a tree somewhere that grows 1 1/2" x 8tpi -> 3/4" x 16tpi internal inserts?

could I aquire a 1 x 8 f to 3/4 x 16 f internal adapter instead - this isn't intended as my heavy chuck solution! do these exist? (the only link I found in hours of searching was to pencrafts 2 months ago but has now gone (I have written to them).

I'm fairly confident that the actual chuck is a copy of the Penn State Ind Barracuda, but the copy may not include the threading, and even if it did the aquisition of an insert from there isn't going to be economical.

thoughts, guidance etc appreciated


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## boysie39 (11 Jan 2012)

I think what you are after is an excert which reduces from your spindle thread down to 3/4" x 16 tpi .
The thing I found wrong with an excert was it moves the work further away from the headstock .
Hope you can understand this.


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## jumps (11 Jan 2012)

thank you Eugene, but my spindle thread is 3/4 x 16

I wouldn't be happy with an excert for this for both the reason you list and the wider implications of hanging the chuck and workpiece on effectively a spindle extension which must at some point bring unwanted flex.


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## Jonzjob (11 Jan 2012)

Jumps, without going through the carp of searching for your "see thread on dakota X450' can you post a link or give more info as to what you are trying to mate to what please?

3/4 16 sounds like a Record CL or DML lathe. Several chucks have adaptors available that nail directly onto the chuck for a variety of spindles and a bit more info may help us to help you? :mrgreen:


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## boysie39 (11 Jan 2012)

Russell at Ask tools is a good person to contact, Very helpful.


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## jumps (11 Jan 2012)

Jonzjob":28bicm7g said:


> Jumps, without going through the carp of searching for your "see thread on dakota X450' can you post a link or give more info as to what you are trying to mate to what please?
> 
> 3/4 16 sounds like a Record CL or DML lathe. Several chucks have adaptors available that nail directly onto the chuck for a variety of spindles and a bit more info may help us to help you? :mrgreen:




John, 

The why is here

https://www.ukworkshop.co.uk/forums/rutlands-dakota-x450-chuck-help-t57367.html

The what is really all in the first post of this thread. 

To save anyone doing the same detective work I spent the day doing...The chuck appears to be a Chinese made copy of the original Barracuda from Penn State Industries, and the jaws are Barracuda items with an additional Rutlands/Dakota badge on the boxes. None of the references to the chuck in the US that I can find confirm the underlying female thread in the chuck body (which is why I give the actual measurements above and was asking for confirmation from a more 'engineering' based member that these most likely represent 1 1/2" x 8tpi ( which is more likely for an older US design but I don't know if these particular spec got changed as part of the market specific build - the addition of the same inserts as the US models, and the measurements, suggest it didn't).

A quick look at the usual suspects didn't give me a match; most better bodies don't use inserts and those that do revolve around m33 and 1 x 8 from Ax

1 x 8 down to 3/4 x 16 seemed a solution, with a reasonable market, but I can't find an obvious supplier - those I have emailed (where an old thread on a forum suggested they might have marketed one at some point) haven't replied yet. Another lead has been provided but will have to wait until tomorrow (and may be un-economical - more than chuck!)

Hope this makes sense!

edit - 

this is interesting

http://www.peterchild.co.uk/osc/patriot-threaded-insert-adaptor-p-356.html

it suggests that there are other chucks with the same size female 'core', and that the thread may not be 1 1/2 x 8tpi but a special 38 x 3mm (the dimensions I took are very very close to these).


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## cambournepete (11 Jan 2012)

Have you tried Robert Sorby?
Most of their Patriot chucks have inserts I believe.


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