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The ongoing saga of John's floor

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John Stevenson	08/06/2011 22:52:43
5068 forum posts 3 photos	So decided to treat myself to a couple of those magnetic pickup tools that ARC sells to try to clear up a bit. Strong magnet inside a closed tube, stick where all the crap is and it all sticks to the tube, place over skip, pull handle and it all drops off - brilliant. So Mark 1 test. Open doors and decide to start in the front shop. Starting to look a tat bit untidy, so a few applications of the bigger pick up tool and voilà. Impressive or not ?? Just need to get the skip emptied now John S.
Martin W	08/06/2011 22:59:00
940 forum posts 30 photos	Hey John Where is the skip parked as looks like you may have put some things in it I would be willing to recycle . Cheers Martin
John Stevenson	08/06/2011 23:10:00
5068 forum posts 3 photos	I was waiting for that. You are welcome to those bloody rotors, I'm getting decidedly pi$$ed with doing these. 24 got dropped off today with end covers and wanted back for Monday. Spent all afternoon making an 8 start nut 1" lead and 1/2" diameter, right pain in the butt but came out nice. Hopefully Mr Rolls Royce will be able to get his crack testing machine working again tomorrow. John S.
Andrew Johnston	09/06/2011 08:36:26
7061 forum posts 719 photos	Ok John, so I can think of ways to machine an eight start screw, but how on earth do you make the nut? Andrew
John Stevenson	09/06/2011 09:04:33
5068 forum posts 3 photos	Not by CNC I'll throw it open first for all the manual guys to have a guess. John S.
harold	09/06/2011 09:13:54
35 forum posts	I'd always assumed that tales of the existence of this floor were cruel myths. We now know that the floor does exist. Another myth busted. Another entry for snopes. John
Tony Jeffree	09/06/2011 11:03:25
569 forum posts 20 photos	I always thought saga was an old English name for rice pudding... Regards, Tony
Nicholas Farr	09/06/2011 11:40:02
3988 forum posts 1799 photos	Hi John, I've not done any multi start screw cutting, but as for the eight start nut, how about fixing the mandrel gear to an index bush/plate of some kind, so it could be adjusted without loosing position on the leadscrew. Nice lot of rotors BTW. Regards Nick
blowlamp	09/06/2011 11:51:05
1885 forum posts 111 photos	Posted by John Stevenson on 09/06/2011 09:04:33: Not by CNC I'll throw it open first for all the manual guys to have a guess. John S. You've gotta tap! Martin.
John Stevenson	09/06/2011 12:44:10
5068 forum posts 3 photos	No no tap and no spare bit of screw. The screw in question is the only bit, it's 4 feet long and has a bearing diameter at both ends. John S.
David Clark 1	09/06/2011 12:58:07
3357 forum posts 112 photos 10 articles	Hi John I would think move the top slide along by one 1/8inch for each pitch until you have cut the thread in 8 different places. Probably have to leave the leadscrew engaged depending on pitch of the leadscrew. If the leadscrew was 1/8in. pitch, you could probably use all eight markings on the thread indicator, the numbered ones and the halfway between ones. I could of course be totally wrong and probably am. regards David
Tony Jeffree	09/06/2011 13:21:58
569 forum posts 20 photos	Posted by David Clark 1 on 09/06/2011 12:58:07: I could of course be totally wrong and probably am. regards David Fraid so David. But then, John told me how he did it the other day - and a very useful technique it is too. When he first mentioned the problem to me, my immediate reaction was "Use Moglice", but that wasn't how he did it either. Regards, Tony
Tony Jeffree	09/06/2011 14:22:31
569 forum posts 20 photos	Posted by harold on 09/06/2011 09:13:54: I'd always assumed that tales of the existence of this floor were cruel myths. We now know that the floor does exist. Another myth busted. Another entry for snopes. John It doesn't really exist. Photoshop can do some wonderful things these days... Regards, Tony
Ian S C	09/06/2011 14:27:27
7468 forum posts 230 photos	My guess would be a broach of some sort, rotated as its drawn through the hole. The external thread I would expect to be done on the mill, but what do I know? Ian S C
Andrew Johnston	09/06/2011 18:48:52
7061 forum posts 719 photos	Well, you could use a helical broach, but I suspect it's not the sort of tool you have lying about on the off chance. Could use EDM, but again not the sort of machine most people have. It would be possible to do it on the lathe, but it would be a funny looking tool to get the right clearances. More of a shaping action. So it could be done on a shaper or slotter with the right feed mechanism. It could probably be done on a manual mill if the nut was split and done in two halves. However, the nut looks like plastic or anodised aluminium? If plastic then the thread could be made by a heated screw, or a simple home made broach. But, since this was presumably a repair job, and was done in an afternoon, I prefer the 'slap some goo around the screw and make a moulding' approach. Could use resin or one of 'liquid metals' for better strength. Whatever way, it's out of my league. Regards, Andrew
Jimbo	10/06/2011 17:57:16
7 forum posts	I think if I were going to attempt this and assuming there was a piece of the external thread available as a gauge I'd screwcut off 7 of the 8 starts with a suitable grooving tool just leaving one. This would enable each start to be gauged. For each pitch advance the top slide by .125. Regards, Jim
John Stevenson	10/06/2011 23:45:37
5068 forum posts 3 photos	Jim, No spare thread to hand but I like your reasoning. John S.
Jimbo	11/06/2011 10:50:07
7 forum posts	John, Only other way I can think of with no gauge but the finished male part is to take a pass through each start at each depth of cut. Bit of a chore but at least all the starts would be at the same depth. Take the tailstock off if necessary to make room to get the 4 foot long screw lined up to test the fit. Jim Edited By Jimbo on 11/06/2011 10:50:52
Richard Parsons	11/06/2011 13:29:25
645 forum posts 33 photos	So you have a ‘bit’ of the 8 start thread. Oh ‘goodie-goodie’! I would a bit of it to the rear of the head pipe and using the bottom of the thread as a ‘dividing head’. I would use it to set and then cut no 1 ‘start’ thread to depth. Disengage the saddle nut, rotate the head stock 1/8^th of a turn, re engaging the saddle, and cut start no 2 to depth. Repeat as required until all 8 starts are cut. I would use the other bit of the spare thread as a gauge. I can repeat this procedure ad-nausiam until I got a good fit. But as usual there is another way! This is to cast the nut using something like ‘Babbit’ or ‘Hoyte’ metal (or the thermo setting plastic if that is what it is). I am going to have to use this method sometime next year to restore cross slide nut on my 36 year old Myford – it is getting a bit sloppy. ATB Dick Edited By Richard Parsons on 11/06/2011 13:31:05
blowlamp	11/06/2011 14:16:29
1885 forum posts 111 photos	Assuming the old nut was still usable: Bolt it to your miller bed and in alignment with the (also bolted down) bore of your new nut. You could somehow attach a single point cutting tool to the end of the threaded rod (a bit like a between centres boring bar) and use it to cut one of the starts. Repeat the operation seven more times by indexing the threaded rod within the old nut. Martin. Edited By blowlamp on 11/06/2011 14:17:51

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