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19th Sep 2020, 07:07 PM #1Golden Member
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Vertex dividing head BS0 Spindle nose and Hercus not the same?
I have just taken possession of a Vertex BS0 dividing head. It is supposed to be a 1½" x 8 Threads per inch spindle nose. It measures at 1½" x 8 t but my 3 Hercus 1½" x 8 backplates won't even make a full revolution before they get stuck. I don't believe I would be the first to have this problem since both bits of kit are so common in this country. I have two machines that these 3 chucks fit on so am somewhat surprised they don't fit the Vertex dividing head.
In fact the chuck that came with the DH will fit both the other machines. In an ideal world I would like all my chucks to be interchangeable so getting the DH's hardened shaft thread ground to suit the others seems my only choice. But before I do, does anybody know what is going on here?
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19th Sep 2020, 07:30 PM #2Diamond Member
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I think the Hercus is 1-1/2" x 8 USS thread whilst the Vertex is 1-1/2" x 8 BSW
Last edited by Com_VC; 19th Sep 2020 at 07:31 PM. Reason: font size
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19th Sep 2020, 08:10 PM #3Golden Member
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19th Sep 2020, 08:14 PM #4Most Valued Member
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That would be my bet, another thing may be the thread crest/root radius. There will be an almost fully rounded root on the Whitworth threads.
The BSx heads from Asia seem to vary in details a fair bit. Especially some have morse tapers, some brown and sharpe and I've even seen a Jarno. I wouldnt be surprised if spindle threads were the same.
Sent from my SM-G973F using Tapatalk
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20th Sep 2020, 04:44 PM #5Golden Member
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I have examined the threads much more closely. I believe they are both 60 degree thread angle and 8 TPI. I am however sure that the pitch circle of the DH thread is larger than that of the Hercus Nose. I note also that the register on the Vertex is 0.015" oversize.
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26th Sep 2020, 11:17 AM #6Most Valued Member
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Yeah went through this 30+ years ago. It's oversize for a Hercus standard spindle nose, you just need to machine the backplate to suit. Not much of a job really, I made 3 back in the day out of cast iron offcuts.
PITA factor is the chucks don't really interchange if you've a Hercus lathe as the thread is sloppy and the register is a different diameter.
Could be worse - my heavy K&T DH has a Cat 50 taper only. Now that is a pain to make tooling for.
PDW
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27th Sep 2020, 12:42 PM #7Golden Member
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PDW,
Thanks for confirming this is a known problem.
I am going to go the other direction and make the spindle match my other spindles (Hercus T&C grinder workhead and a Precision Grinding UNIMAC). It will be a once off annoyance.
Worst outcome is I will have to make a new spindle if I screw up. But even that would have the upside of replacing the B&S #7 taper with a MT2.
That would be a lot worse. With my equipment I have a good chance of fixing this spindle, I would have no chance of making Cat 50 tooling.
Eric
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