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Summer 1990 Rotary Table

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Dr. MC Black06/01/2022 12:44:02
286 forum posts
1 photos

Ladies & Gentlemen

Has anybody made the Rotary Table described in the Summer 1990 issue, please?

I have looked at the drawings and carefully read the article.

The list of screws on Sheet 2 of the Drawings mentions an EIGHT INCH long 4BA socket cap screw but I can't see where this is used in the finished article.

The photograph on page 56 of the article doesn't have sufficient clarity for me to see how it's used.

I intend to replace 4BA with M4 throughout but cannot find a 200mm long M4 Cap screw from any of my usual sources.

I have tried to access the Archive to see if I can see detail in the article that was lost when I saved it as pdf - but without a total lack of success.

Happy New Year and Very many thanks for reading this


HOWARDT06/01/2022 13:14:46
908 forum posts
39 photos

Don’t think you would find either 4BA or M4 in those lengths. According to Unbrako catalogue M4 max is 40mm. During my hydraulic design days we used to use long M5 socket heads upto 200mm for holding valve stacks, so maybe longer M4 are available for special uses but you would have to ask around. I would redesign to use a rod and short screw or whatever is practical, long screws can be easily twisted if overtightened.

Ady106/01/2022 19:13:03
5089 forum posts
736 photos

A threaded rod with a nut each end?

Even if you fabricated your own long screws up, as mentioned there is a real twisting issue with 8inches of 4mm

Howard Lewis06/01/2022 20:20:24
6104 forum posts
14 photos

Are you sure that the requirement is not for 4BA SHC screws 1 inch long, 8 off?

Not seen the article( s ) but probably 8 inches would be bigger than any dimension on the table?


JasonB06/01/2022 20:32:42
22747 forum posts
2653 photos
1 articles

Certainly says 8" lg but can;t see where it goes, second drawing here

Durhambuilder06/01/2022 20:44:54
72 forum posts
5 photos

Appears to screw in to item four the bottom collar, I wonder if it should be 5/8 or 7/8 and not just 8?

Peter Cook 606/01/2022 20:53:15
275 forum posts
79 photos

Agree with Durham builder as to location. Suspect the length is [0].8", and the scan has made the decimal point invisible.

Edited By Peter Cook 6 on 06/01/2022 20:53:48

SillyOldDuffer06/01/2022 21:17:34
8682 forum posts
1967 photos

Another vote for Durham Builder.


Looks like the 4ba screw that clamps the collar, a bit over twice 0.320" long. Typo: could be 0.8" or ⅞"


Neil Wyatt06/01/2022 21:24:18
19033 forum posts
734 photos
80 articles

I agree with Dave. I'd guess 5/8".


Circlip06/01/2022 21:24:27
1510 forum posts

Beat me to it, Assy drawing states Item 4 and B for location. Made mine way back in Stainless (cos I had access to some), all metricated, my item 'B' is M3 x 20mm SHCS.

Regards Ian.

Nicholas Farr06/01/2022 21:30:51
3360 forum posts
1542 photos

Hi, the socket head cap screw B nips the collar item 4 on page 2 of the drawing, which Durhambuilder suggests is 5/8", a 7/8" would protrude through the the threaded hole, though that may not matter. The socket head can be seen in the top drawing, shown by the circles 4 & B on page 1. So a M4 x 16mm should be OK.

Regards Nick.#

Well everyone beat me! P.S. there is no decimal point on the original drawing for the scan to miss.

Edited By Nicholas Farr on 06/01/2022 21:38:28

Circlip06/01/2022 22:05:53
1510 forum posts

Not the first time the magazines graphics "Draughtsmen" have got it wrong.

Regards Ian.

Dr. MC Black07/01/2022 01:04:29
286 forum posts
1 photos

Very many thanks to everybody for your contributions and comments.

I was always taught (I passed O'level Technical Drawing with grade A over 50 years ago) never to write a number less than unity without a zero in front of the decimal point.

Clearly the draftsman who created the scanned drawings never heard of that convention.

Having read all the comments, I now think the screw should have been 5/8 inch long

I am sorry to write that I found the "overlapping printable Pdf pages"to which JasonB referred NOT very helpful because the some of the parts appear on two sheets. But I enlarged the pdf and printed each element entirely on an A4 sheet. (I'll be happy to send those to anybody interested if you send me your email address, off-list.)

Has anybody (apart from Circlip) actually build this Rotary Table, please?

I came across some 4"diameter Aluminium this afternoon and may be able to acquire a slice 1/2" thick. Can anybody see any problems in using Aluminium rather than steel for the turntable, please?

With best wishes and Very many thanks again


Neil Lickfold07/01/2022 03:34:36
861 forum posts
195 photos

If the fastener was shown on the assembly, all the guesses would have been eliminated. Sometimes no matter how much care is taken, important dimensions can also be left off of drawings as well, even when being checked by an independent check person. It is a good reason to have an over view of the part you are making and what it has to be connected to. I made a very basic rotary table to make a liner for a model engine back in 1989. It used a bronze gear and was mostly made of Al alloys. Only now do I wish that I had made it with a thin section thrust bearing and a miniature series ball bearing to give it longevity and concentricity.

Dr. MC Black07/01/2022 08:54:19
286 forum posts
1 photos

There is a photograph of the underside of the assembly in the article but it has reproduced poorly.

That would give confirmation of the way that the table was constructed.

If anybody has a copy of the printed magazine it would be very helpful to have a high resolution colour photograph of the top of page 56.

Although I have a digital and print subscription, the scanned image in the magazine in the archive is rather "washed out"

With best wishes and thanks again.


Michael Gilligan07/01/2022 09:09:34
20182 forum posts
1053 photos
Posted by Dr. MC Black on 07/01/2022 01:04:29:


I am sorry to write that I found the "overlapping printable Pdf pages"to which JasonB referred NOT very helpful because the some of the parts appear on two sheets. But I enlarged the pdf and printed each element entirely on an A4 sheet. (I'll be happy to send those to anybody interested if you send me your email address, off-list.)



That’s an excellent idea, and very generous of you yes

[However] Personally; I have no need of them, because I save the full sheets onto the iPad, and can simply view details on-screen.




For any future readers of this thread: I must just add that Nick’s scans are superb and I am quite sure, from this screen grab, that the error is in original drawing:


Nicholas Farr07/01/2022 09:55:33
3360 forum posts
1542 photos

Hi Dr. MC Black, don't know how they compare, but the photos in the magazine are not brilliant.

rt-pic 1.jpg

rt-pic 2.jpg

For those that don't know, the free plans were printed on each side of an off white sheet of paper measuring 793 x 296mm and was folded three times and stapled in between the centre pages of the magazine.

Below is a photo of the original drawing from the magazine, showing similar to the grab that MichaelG has posted.

rt-pic 3.jpg

Regards Nick.

Michael Gilligan07/01/2022 10:26:20
20182 forum posts
1053 photos

Thanks for the post, Nick yes

You are a star

The resolution of your scans is now evident for all to admire:

Comparing your photo of the print with my screenshot of the PDF we see that the dot which follows the A has not been fully resolved from the x [which is, of course, mis-placed]



Edit: Demonstrandum



Edited By Michael Gilligan on 07/01/2022 10:40:10

Dr. MC Black07/01/2022 10:36:04
286 forum posts
1 photos

Dear Nicholas

Thank you for taking the time to write.

Those photographs are far better than the ones in the pdf that I downloaded from the archive. The second shows detail of construction much more clearly.

I hope that I did NOT offend when I wrote about the overlapping sheets breaking parts of the assembly.

With best wishes and thanks again.


Nicholas Farr07/01/2022 10:47:56
3360 forum posts
1542 photos

Hi MichaelG, well spotted, I have never noticed that myself.

rt-pic 4.jpg

Regards Nick.

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