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General Category => Tool tips & reviews => Topic started by: crazylegs on May 13, 2019, 08:18:02 PM

Title: Nova thread adapter problem
Post by: crazylegs on May 13, 2019, 08:18:02 PM
I have a Nova lathe with a 1 1/4 8tpi headstock thread. I have several chucks which fit the thread  however I have recently bought a new Record chuck that required a thread adapter to fit the lathe. I purchased the adapter that is designed to fit, it even lists the lathe, from record power but this is where the odd things start. It fits the chuck but will not screw onto the headstock thread. As I said other 1 1/4 8 tpi adapters screw on fine. I was a bit perplexed but thought maybe I had a duff one so ordered up another adapter. The exact same thing happened. Now here is the odd bit, take the adapter out of the chuck and it screws on perfectly the wrong way round. They both do?  I have checked and cleaned the threads and found nothing. I have taken a bit of abrasive paper to the end surface in case of a small burr but no improvement. Now as other chucks/adapters fit I conclude the thread is fine. Any suggestions? I have been in contact with record power and have sent them an adapter to look at but to be honest I hold out little hope. It has been suggested the the adapters have been machined with a slight taper but is this likely with two being wrong and purchased from different places?
Anyone got a 1 1/4 inch 8 tpi dye I can run down the thread of the spindle?
Title: Re: Nova thread adapter problem
Post by: Redtails5 on May 14, 2019, 08:55:31 PM
Sorry to hear of your problem and record powers failure to resolve it thats unfortunate.
So down to the nitty gritty they are both not fit for purpose send them back and get a refund.
Second option is to get the threads checked out you need someone who can check the major diameter of the thread, if thats ok you need the effective diameter
Checking one way is to three wires of the correct size
These will give you the effective diameter of that thread . if this diameter is plus it will mean the thread will be tight if the diameter reading you take and is less than the stated diameter it will be loose.
This term effective diameter for any vee shaped thread
55 degrees,(whitworth) 60degrees (metric,unc,unf,anc,anf)and can be found in any engineering book ie machinerys hand book,zeus etc
Also get the thread form checked this can be tipped so the angle on each side of the vertical is not equal.
A tap that size will cost you the earth.
For all of this you can contact a local engineering shop
Good luck with it.