Help- Advice Request

[kvt]

Obtaining a new to me lathe, but need backing plate for chucks. I know that cast is supposed to be best for backing plates, but will normal steel work.
Second part of the question. what is the best way to start the new backing plate, when the main thing I have is a face plate.
One thought is to drill 4 holes in the blank, Then mount it to the face plate. and indicate it as best possible.
Then bore out the center hole, face off the area for mounting, then start threading.
Would it be better to space it off of the face plate so that you do not hit the face plate when boring and threading. I figure once it is treaded, then mount it on the spindle and finish turning it to size and face it off properly. Then turn it around and finish off the back.

Hopefully the last part, how to figure out what size whole to bore for a 52mm x 8 tpi thread.

New to doing internal threading. have done some external but have not done internal watching some you tube but that is it.

 

[Wreck™Wreck]

Obtaining a new to me lathe, but need backing plate for chucks. I know that cast is supposed to be best for backing plates, but will normal steel work.
Second part of the question. what is the best way to start the new backing plate, when the main thing I have is a face plate.
One thought is to drill 4 holes in the blank, Then mount it to the face plate. and indicate it as best possible.
Then bore out the center hole, face off the area for mounting, then start threading.
Would it be better to space it off of the face plate so that you do not hit the face plate when boring and threading. I figure once it is treaded, then mount it on the spindle and finish turning it to size and face it off properly. Then turn it around and finish off the back.

Hopefully the last part, how to figure out what size whole to bore for a 52mm x 8 tpi thread.

New to doing internal threading. have done some external but have not done internal watching some you tube but that is it.

In 25 years in the machine shop business I have never seen anyone mix a metric thread diameter with a TPI lead, 52MM is 2.o47" 8 TPI is of course a lead of .125.
Check the numbers.
As to the question about bore size for an internal thread, subtract the thread lead from the nominal external thread diameter in your case a 2"-8 internal thread would have a minor diameter of roughly 1 7/8", this assumes a 60 Deg. included angle.

 

[4GSR]

Ken,

Do you know the brand of the lathe you are getting? Wreck is probably correct that it may be a 2"-8 pitch thread. But I have seen stupid engineers specify things in metric with imperial pitches. Oops, wait a minute, I'm a engineer.

 

[Wreck™Wreck]

Ken,

Do you know the brand of the lathe you are getting? Wreck is probably correct that it may be a 2"-8 pitch thread. But I have seen stupid engineers specify things in metric with imperial pitches. Oops, wait a minute, I'm a engineer.

Where I work now they have been making repeating parts for several customers for 20 or more years, these are all inch based components and the drawings have not changed in that time. In the last year 40-50 of the old drawings we had are now dimensioned in millimeters yet the parts are the same, I suspect that this is an ISO requirement.

 

[kvt]

It is an old Taiwan made lathe LAM 1024b (1977) also the old Jet 1024p if not mistaken was made by the same shop, and uses the same oddball thread on the spindle. Have found many refs to it, and to a 54mm X 8 TIP for a larger JET 1236 of the same era as well. All were supposedly made in the same shop in Taiwan . And most information I have found is that most have to make their own back plates and Jet will almost not acknowledge that they even had that old lathe. Some people actually call it a 2inch by 8TPI but everything I have found is that it actually is a mix of MM size with 8tpi which is probably why it is so hard to find.

 

[Wreck™Wreck]

It is an old Taiwan made lathe LAM 1024b (1977) also the old Jet 1024p if not mistaken was made by the same shop, and uses the same oddball thread on the spindle. Have found many refs to it, and to a 54mm X 8 TIP for a larger JET 1236 of the same era as well. All were supposedly made in the same shop in Taiwan . And most information I have found is that most have to make their own back plates and Jet will almost not acknowledge that they even had that old lathe. Some people actually call it a 2inch by 8TPI but everything I have found is that it actually is a mix of MM size with 8tpi which is probably why it is so hard to find.

If you have the tools measure the pitch diameter over wires then look in the thread specification section of Machinery's Handbook for a similar PD, lead and major diameter. If there is nothing close then it may well be a proprietary spindle mount.

 

[4GSR]

It wouldn't surprise me that Jet did such a thing back in their beginnings. 54mm= 2.125984". Wreck is right, take you a M.O.W. provided you have a set. If you don't, let me know and I'll send you .081" wires to use.

Wreck, as for ISO saying you have to provide measurements in "mm" is B.S. They encourage you to use dual dimensions on your drawings....More European noxi crap we have to deal with! Hitler didn't win the war but ISO is...