Summer 1990 Rotary Table

[Dr. MC BlackParticipant @dr-mcblack73214]

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

MC

[Dr. MC BlackParticipant @dr-mcblack73214]

[HOWARDTParticipant @howardt]

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.

[Ady1Participant @ady1]

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 LewisParticipant @howardlewis46836]

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?

Howard

[JasonBModerator @jasonb]

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

[DurhambuilderParticipant @durhambuilder]

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 6Participant @petercook6]

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

[SillyOldDufferModerator @sillyoldduffer]

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"

Dave

[Neil WyattModerator @neilwyatt]

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

Neil

[CirclipParticipant @circlip]

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 FarrParticipant @nicholasfarr14254]

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

[CirclipParticipant @circlip]

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

Regards Ian.

[Dr. MC BlackParticipant @dr-mcblack73214]

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

MC

[Neil LickfoldParticipant @neillickfold44316]

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 BlackParticipant @dr-mcblack73214]

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.

MC

[Michael GilliganParticipant @michaelgilligan61133]

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

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

MichaelG.

.

.

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 FarrParticipant @nicholasfarr14254]

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

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.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the post, Nick

You are a

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]

MichaelG.

.

Edit: Demonstrandum

 

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

[Dr. MC BlackParticipant @dr-mcblack73214]

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.

MC

[Nicholas FarrParticipant @nicholasfarr14254]

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

Regards Nick.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Dr. MC Black, glad you find the photos better. I was not offended about your comments. Those scans were done many years ago and PDF editable programmes cost more than I was prepared to pay and the idea of the overlapping the sheets, was so that anyone could print them out on an A4 printer, trim a suitable side and attach to the next page and thus produce a drawing of the same size to that of the originals. Being there were a large number of these various plans, they were did this way to produce something useful and I could apply the same template to every drawing, they still took a fair amount of time to scan, as each side had to be scanned from both ends and then stitched together and then each scan had to be cropped four times to produce the separate pages. You can produce a decent size drawing onto a A3 sheet of paper, using the full scans, but of course they will be only a little over 50% the size of the originals.

Regards Nick.

Edited By Nicholas Farr on 07/01/2022 11:15:32

[SillyOldDufferModerator @sillyoldduffer]

Posted by Dr. MC Black on 07/01/2022 01:04:29:

…

I was always taught … 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.

…

Clearly he knew the convention because it's used throughout the rest of the drawing! Just a typo I think. He made another minor mistake in the copyright notice, possibly not corrected because it's too much work by hand:

I found it surprisingly hard to suss out Ⓑ. I didn't tune into the drawings well. If I were building the table, I'd redraw it in CAD to make sure I understood it.

Dave

[Dr. MC BlackParticipant @dr-mcblack73214]

I did nothing more complicated than enlarge the drawing so that the element for each part filled an A4 window on my screen and then printed "Current View" on A4 sheets.

I notice that in many places on the drawing, the draftsman used a " (inch symbol) before the decimal point – but NOT consistently.

I notice that the holes on the 2.5" and 3/4" circles are only shown for part of the circles (say between 1 o'c and 5 o'c) rather than for the entire circle. Any idea why, please?

If Mr. Daish is a subscriber to this forum, is there any way of contacting him, please?

Very many thanks, in anticipation, for your continued assistance.

MC

[SillyOldDufferModerator @sillyoldduffer]

Posted by SillyOldDuffer on 07/01/2022 15:15:24:

Posted by Dr. MC Black on 07/01/2022 01:04:29:

…

I was always taught … 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.

…

Clearly he knew the convention because it's used throughout the rest of the drawing!

…

Dave

I must be losing the plot! The start with a zero convention most certainly isn't used throughout the rest of the drawing. DrMC is right. My excuse, I was looking at another plan at the same time. Sigh…

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