Any chance?

Was wondering if anyone out there might happen to have a bolt kicking around that has a thread diameter of 1 3/4 inch with 6 threads per inch.
Have been considering getting a vicmarc chuck to suit my larger lathe however they don't offer an insert with this size thread.
For them to make up an insert they need a male thread of the right size, I have female threads of the right size on my faceplates but apparently a male thread is better so they can make sure sure the inserts fit properly.
Tried a nut and bolt specialist here in Hobart and they did have one high tensile bolt with the right sized thread but the cost was lofty.
Doesn't really matter if the bolt/thread is hollow, like on a pipe etc, or what sort of metal it's made from.

Artful,

My 20th edition of Machinery's Handbook specifies for Unified Screw Thread 1 3/4-6 UN, internal thread, class 2B, minor diameter min 1.570 max 1.600, pitch diameter min 1.6417 max 1.6525, major diameter, 1.750. All in inches.

The British Standard Whitworth is 1 3/4 - 5 and the British Standard Fine is 1 3/4 - 7, so your spindle is probably the above.

The specifications above and your nicely fitting face plate should be able to get a chuck to fit.

If not a plain chuck and a trip to an engineer is in order. You might have a chat with the engineer as to cost first.

I had an old Sorby chuck bored and threaded by a machine shop (engineer) and he asked for the spindle. It was a 1 X 8 tpi so I took the headstock, as it was easily detached and not heavy. The chuck fit perfectly.

It is not likely that a commercial bolt is going to have the class of fit that you would want for a chuck on a spindle. Keeping in mind that the register is on the flat and / or on the unthreaded part behind the threads on the spindle.

They're not quite what you asked for, and definitely not cheap, but 1 7/8" x 6tpi spindle adaptors can be got here:

http://bestwoodtools.stores.yahoo.net/prstspadwith.html

They come in tool sizes of 1" x 8tpi, 1 1/4" x 8tpi, 1 1/2" x 8tpi and 33 x 3.5mm, part numbers ADS3001 to ADS 3004, near the bottom of the page.

I just found this by chance and remembered your post while looking for a 1" 10tpi spindle to 1" 8tpi tool size adaptor to suit an 'Easy' 4" chuck.

Quote:

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Originally Posted by artful bodger

Was wondering if anyone out there might happen to have a bolt kicking around that has a thread diameter of 1 3/4 inch with 6 threads per inch.
Have been considering getting a vicmarc chuck to suit my larger lathe however they don't offer an insert with this size thread.
For them to make up an insert they need a male thread of the right size, I have female threads of the right size on my faceplates but apparently a male thread is better so they can make sure sure the inserts fit properly.
Tried a nut and bolt specialist here in Hobart and they did have one high tensile bolt with the right sized thread but the cost was lofty.
Doesn't really matter if the bolt/thread is hollow, like on a pipe etc, or what sort of metal it's made from.

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I had a spindle adaptor made up by Vermec (Enzo) for my vicmarc chuck .They were quite happy with a female thread as a sample,had to wait for about 6 weeks for it to be made.
Their machining is first class fitted perfectly well worth the wait and cost.They made up a sample male thread first to make sure it fitted into my female sample before making up the adaptor

Quote:

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Originally Posted by greyhound

I had a spindle adaptor made up by Vermec (Enzo) for my vicmarc chuck .They were quite happy with a female thread as a sample,had to wait for about 6 weeks for it to be made.
Their machining is first class fitted perfectly well worth the wait and cost.They made up a sample male thread first to make sure it fitted into my female sample before making up the adaptor

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Thanks for the tip Greyhound. I'd never heard of Vermec before. Just sent them an inquiring email and waiting for response.

Finally got my mits upon the 1 3/4 inch thread adapter(insert) for the vicmarc 120 chuck.
Decided not to buy the $90 non refundable bolt (of correct size) from boltshop and then send it up to Vicmarc in Queensland for them to make adapter and send it back here.
Instead went with a local engineer who operates near the bolt shop and knows them well.
This is what he made me.....
Attachment 319111 Picture shows from left to right. 1 inch x 10tpi adapter that came with the chuck and fits my woodfast lathe if need be. The new 1 3/4 inch adapter(for my big lathe), and the 120vm chuck.
When I got the new insert home it would only screw onto my lathes thread about one and a quarter turns before refusing to go on any more.
I took it back to the engineer who shaved a bit more off the thread. Picked it up a few days later and this time it screwed on nearly all the way bar 8-9mm. So had to take it back yet again.
3rd time lucky and it fits like a glove. Thankfully the engineer did not charge me for the 2 follow up visits.
The initial price of $240 for the adapter/insert is pretty well what the chuck cost me in the first place however I guess there is not much point in having the chuck if you cant use it. Also makes you realise how reasonably priced the standard range of inserts/adapters are from vicmarc.
Just out of interest I weighed the 2 inserts. The 1 inch x 10 tpi was 434grams....The 1 3/4 inch one is 1.254KG.