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Pultra lead screw

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david bennett 807/10/2022 20:47:55
245 forum posts
19 photos

Dell, mine is metric,but your nut looks rather long. I wonder if yours was made with the intention of being cut into two at a later date. If not , can you see a purpose for the grub screw holes?

dave.

Michael Gilligan07/10/2022 21:22:17
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Posted by david bennett 8 on 07/10/2022 20:47:55:

[…] I wonder if yours was made with the intention of being cut into two at a later date. If not , can you see a purpose for the grub screw holes?

dave.

.

I had the same thought, Dave … but you expressed it so well that I shall just add +1 yes

MichaelG.

Dell07/10/2022 21:37:23
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Posted by Michael Gilligan on 07/10/2022 21:22:17:
Posted by david bennett 8 on 07/10/2022 20:47:55:

[…] I wonder if yours was made with the intention of being cut into two at a later date. If not , can you see a purpose for the grub screw holes?

dave.

.

I had the same thought, Dave … but you expressed it so well that I shall just add +1 yes

the only thing I can think of is when one gets wears adjusting one grub screw over the other it puts a slight twist on the nut , so effectively putting the thread on an angle and taking up play because putting the thread on an angle tightens it up , the overall length of my nut is 11mm same as the split two together, my Pultra is mid 1940’s so perhaps the one in the picture posted earlier is later and metric.
a friend has a crosslide ( metric ) with smashed T slot on the bottom and I am hopeful he will sell it to me so I can convert my crosslide to metric and that one has split leadscrew nuts, it has bigger dials as well the same as the picture earlier, having gout in both hand it would be easier to use.

Dell

also I see the nut in picture has a shoulder on one part and a recess on the other , yes please PM me and explain, if it was a antique clock I would be fine.

MichaelG.

 

Edited By Dell on 07/10/2022 21:41:18

david bennett 807/10/2022 21:40:31
245 forum posts
19 photos

Dell If you "search" this site for "pultra" ( stripped thread) there is one identical to yours.

dave

Michael Gilligan07/10/2022 22:07:59
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23121 forum posts
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Another useful reference from this forum: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=146290

MichaelG.

Michael Gilligan07/10/2022 22:47:59
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23121 forum posts
1360 photos

This might be handy for general reference:

.

92989257-8f7e-48b7-941c-4c95c07c8cc2.jpeg

.

MichaelG.

david bennett 807/10/2022 22:54:11
245 forum posts
19 photos

Dell, the anti backlash idea is not to put a twist in there, but to adjust both sides together (and parallel) to remove thread siackness.

dave.

Michael Gilligan07/10/2022 22:57:55
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23121 forum posts
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Posted by Dell on 07/10/2022 21:37:23:

also I see the nut in picture has a shoulder on one part and a recess on the other

.

The shoulder slides neatly into the recess … which prevents tilt between the two components.

The adjustment is designed to be axial

MichaelG.

.

Edit: __ Dave posted whilst I was typing that

Edited By Michael Gilligan on 07/10/2022 22:59:17

Michael Gilligan07/10/2022 23:11:16
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23121 forum posts
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Posted by Dell on 07/10/2022 21:37:23:
.

[…] yes please PM me and explain […]

.

Sorry to intrude, Dell … Was that line meant for NDIY’s attention ?

MichaelG.

david bennett 807/10/2022 23:47:43
245 forum posts
19 photos

Dell ,I think I have seen the reason for your confusion. You effectively have through holes for the grubscrews. If you look at the earlier pics you will see the smaller threaded piece has no grubscrew holes. That is what the grubscrews bear against. You probably had them bearing against the topslide casting.

dave.

Dell08/10/2022 07:54:38
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230 forum posts
44 photos

6536a112-c6f0-46aa-85bc-a7eb4ee49bee.jpegHere is an extract from Pultra paperwork it seems they changed the nut to two piece in the 60’s and to metric .

And yes sorry Michael it was for NDIY

a1f73a04-a18f-41b8-9bef-16b2dffddbdd.jpeg

Michael Gilligan08/10/2022 08:03:39
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23121 forum posts
1360 photos
Posted by Dell on 08/10/2022 07:54:38:

6536a112-c6f0-46aa-85bc-a7eb4ee49bee.jpegHere is an extract from Pultra paperwork it seems they changed the nut to two piece in the 60’s and to metric .

And yes sorry Michael it was for NDIY

a1f73a04-a18f-41b8-9bef-16b2dffddbdd.jpeg

.

Those are interesting references, Dell

Thanks for sharing them

MichaelG.

Dell08/10/2022 08:18:22
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230 forum posts
44 photos
Posted by david bennett 8 on 07/10/2022 23:47:43:

Dell ,I think I have seen the reason for your confusion. You effectively have through holes for the grubscrews. If you look at the earlier pics you will see the smaller threaded piece has no grubscrew holes. That is what the grubscrews bear against. You probably had them bearing against the topslide casting.

dave.

Hi dave

I can see the logic when the nut is 2 piece but with the 1 piece if they are adjusted up evenly then all you are doing is moving the nut out not taking any slack up unless it’s adjusted at a slight angle, even then it’s not taking slack it’s just making the nut tighter on the thread.

anyway my friend has decided to sell me some metric dials leadscrews and 2 piece nuts so I can convert my on to metric and have bigger handles.

thanks for all the input Dell

david bennett 808/10/2022 12:36:30
245 forum posts
19 photos

Dell, I know this has dragged on a bit,but could I ask one more question? I could kick myself for not asking sooner,but does your other slide look the same?

dave

Dell08/10/2022 12:45:34
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230 forum posts
44 photos
Posted by david bennett 8 on 08/10/2022 12:36:30:

Dell, I know this has dragged on a bit,but could I ask one more question? I could kick myself for not asking sooner,but does your other slide look the same?

dave

Looks identical in the picture but until I get it I can’t be sure.

Dell

Dell08/10/2022 13:16:00
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230 forum posts
44 photos

This is what I have coming hope they fit.

Dell

146c31ff-61b5-403c-a72b-fcc4a693fa1c.jpeg

david bennett 808/10/2022 13:16:30
245 forum posts
19 photos

No, I meant does your present cross slide look the same as your present topslide regarding the feed nuts?

dave

Edited By david bennett 8 on 08/10/2022 13:17:29

Edited By david bennett 8 on 08/10/2022 13:18:12

Dell08/10/2022 16:15:57
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230 forum posts
44 photos

Sorry David

I misunderstood yes the nuts are identical, the screws I have coming have two piece nuts and I think that is a much better idea.

Dell

Dell13/10/2022 08:23:05
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230 forum posts
44 photos

Well the metric leadscrew and nuts arrived the reason for the earlier crosslide only having one single nut is that the leadscrew also screws into the brass part in the centre of the slide, and the later ones don’t hence the 2 part nuts, also the leadscrew nuts on the later metric ones are larger although the are very similar shape, hence the later metric lead screws and nuts won’t fit earlier slides.
Dell

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