By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Oct 22nd

Linear division in early 20th century

As in the '20s

All Topics | Latest Posts

Search for:  in Thread Title in  
Bazyle31/03/2012 12:17:13
avatar
4761 forum posts
187 photos

Does anyone know specifically what the preferred method of linear indexing would be in a workshop nearly 100 years ago?

Today things are different but when vertical mills were less common would a rotary dividing head and gear engaging a rack be the preference over a leadscrew with changewheels? The aim being 1 turn per division to make production foolproof.

Some special precision linear dividers were screw based but what would a small production shop use?

Swarf, Mostly!31/03/2012 19:47:07
498 forum posts
41 photos

Hi there, all,

There's a device called a 'Merton Nut', basically a sleeve of cork or other naturally elastic material, that engages with several threads of the most precise screw you can make. The idea is that it averages out the pitch errors of the screw.

It isn't load-bearing so you can't use it as a leadscrew.

Best regards,

Swarf, Mostly.

Stub Mandrel01/04/2012 10:04:04
avatar
4306 forum posts
291 photos

I thoughtMaudsley generated his 'master leadscrew' by using an angled blade mounted on a free-moving carrier against a rotating bar of soft metal. This created a groove sufficient to guide a cutter that could replicate the accurately cut spiral to make a proper screw... and some have argued that all modern screws are descended from taht one!

Neil

Ian S C01/04/2012 11:33:54
avatar
7447 forum posts
230 photos

I think it's some where in vol 1 ME (1898), an artical about cutting threads free hand with chasers.

Ian S C

Billy Mills01/04/2012 20:42:18
377 forum posts

Sorry Michael but you CAN improve on the internal reference by adding complexity. Maudsley's template corrected leadscrew was one such example as was his method of using an auxillary screw to compensate for errors in the average pitch of a leadscrew.

Billy.

Ian P01/04/2012 20:44:49
avatar
2217 forum posts
90 photos
Posted by Billy Mills on 01/04/2012 20:42:18:

Sorry Michael but you CAN improve on the internal reference by adding complexity. Maudsley's template corrected leadscrew was one such example as was his method of using an auxillary screw to compensate for errors in the average pitch of a leadscrew.

Billy.

But how did he know he had pitch errors unless he had something accurate as a reference?

Ian

John Stevenson01/04/2012 21:11:26
avatar
Moderator
5068 forum posts
3 photos

I have a Hauser rotary table here that has a band around the bottom of the table.

This band is scraped to compensate for any errors and these errors are transmitted by a bell crank assembly to the zero mark on the dial.

So in effect it moves the zero to compensate for any errors.

A lot of jig borer's also had this hand scaped linear beam to compensate for pitch errors

John S.

Michael Gilligan02/04/2012 08:18:13
avatar
14139 forum posts
616 photos

Bazyle,

http://www.practicalmachinist.com/vb/general/expiriments-leadscrew-lapping-218177/

is worth reading ... especially Posts #19 and #20

MichaelG.

Bazyle02/04/2012 09:41:40
avatar
4761 forum posts
187 photos

Thanks for the responses and some interesting insights. Actually I wasn't so interested in accuracy as 'hackuracy' and whether for a drilling jig a local works machine shop who certainly wouldn't have a jig borer or want to sub out would be more likely to use the rack method or a geared leadscrew.

Terryd02/04/2012 16:44:15
1926 forum posts
179 photos
Posted by Stub Mandrel on 01/04/2012 10:04:04:

I thoughtMaudsley generated his 'master leadscrew' by using an angled blade mounted on a free-moving carrier against a rotating bar of soft metal. This created a groove sufficient to guide a cutter that could replicate the accurately cut spiral to make a proper screw... and some have argued that all modern screws are descended from taht one!

Neil

Ho Neil,

You are quite right. Maudslay built a screw generating machine that held a blade at the required helix angle and cut into a soft metal bar, this was followed by a cutting tool which actally cut the reference thread in the bar. He built a table micrometer known as 'The Lord Chancellor' with a thread around 5 feet long which could measure to within 0.0001 (ten thousandth) of an inch.

James Watt claimed that his later micrometer (shown at the Great Exhibition 1851, could measure to within one millionth of an inch, but this was later disproven by the National Physical Laboratory - it could only manage to within one fortythousandth. So very accurate threads were available from the early 19th century. In fact Jesse Ramsden was making some extremely accurate machinery in the 1770s.

Maudslay's Screw Generating Machine (in the Science Museum):

Best regards

Terry

Edited By Terryd on 02/04/2012 21:22:15

Michael Gilligan02/04/2012 21:31:05
avatar
14139 forum posts
616 photos

Bazyle,

"hackuracy" is a great term ... it made me smile.

I think your local works would have either relied upon a leadscrew, or spaced it out with dividers.

For the benefit of future readers: It's worth mentioning that a Gaertner-style "effective pitch adjuster" could be used [for example] to convert a 26tpi leadscrew to 1mm pitch [or vice versa] ... very handy for those occasional jobs.

MichaelG.

Michael Gilligan02/04/2012 21:45:41
avatar
14139 forum posts
616 photos

Terry,

If you can find it ... "The Whitworth Measuring Machine" by Goodeve and Shelley is well worth reading.

Amongst other things, they note that: "The Millionth machine, as constructed, is rather a machine for comparison than simple measurement."
Whitworth's method of standardising the anvil pressure is fascinating, and very clever!
 
PMichaelG.

Edited By David Clark 1 on 03/04/2012 08:10:43

Terryd03/04/2012 05:55:16
1926 forum posts
179 photos

Thanks Michael,

I found a facsimile reprint sold by Amazon for a good price and have ordered a copy at quite a good price after reading the restricted pages. Looks to be quite a fascinating book.

Best regards

Terry

Springbok03/04/2012 08:09:30
avatar
879 forum posts
34 photos

Michael,

Thank you that was in my mind the most accurate definition.

Bob

Terryd03/04/2012 12:20:32
1926 forum posts
179 photos

Hi Michael W,.

I think that you will find that Maudslays generating machine was very capable of producing long accurate screw threads. His original screw cutting lathe is on display in the Science Museum London and it feels quite strange handling the same handles that Maudslay himself operated. What does interest me is how Jesse Ramsden was able to produce the extremely accurate screws that he used in his dividing engines to generate the very accurate astronomical devices in the early half of the 18thC.

The system for cutting threads in wood using three cutters set in a block at the required helical angle to a bored hole with the intended screw in the form of a wooden blank which was screwed through to generate a thread was in use for many centuries and was certainly used by Gutenberg to produce the hardwood screws for his printing presses. The Greeks at least, used the method to make screws in wood for Olive and Grape presses.

The generated screw was then used to drive a length of wood fitted with a cutting tool to generate a fitted 'nut'.

Best regards

Terry

John Haine03/04/2012 13:05:07
2662 forum posts
136 photos
Why is everyone talking about the early 19th century when the question was about the early 20th century?
Michael Gilligan03/04/2012 20:50:09
avatar
14139 forum posts
616 photos

John,

Probably because it is interesting!

Please feel free to ignore my next post, where I shall reply to Terry regarding Jesse Ramsden [the 18th century Pioneer].

MichaelG

Michael Gilligan03/04/2012 20:58:16
avatar
14139 forum posts
616 photos

Terry,

The full text of Jesse Ramsden's paper is available here: http:// http://www.fer3.com/arc/imgx/Text.pdf

and an excellent commentary, here: http://www.fer3.com/arc/imgx/Commentary-on-Jesse-Ramsdens.pdf

Both thanks to the expert Mr Morris

http://sextantbook.com/category/chasing-tenths-of-an-arcminute/

MichaelG.

John Haine03/04/2012 22:13:52
2662 forum posts
136 photos

My point was that by the early 20th century these problems must have been substantially solved. Lathes had accurate leadscrews, people were making IC engines, diffraction gratings were being ruled etc. So I wasn't quite sure why the question was asked. The earlier history is interesting though, a project to reproduce as a "model" Maudslay's screw generating machine would be an interesting project to prove that he could have done it. Rather like the Science Museum making Babbage's Analytical Engine to show that it was feasible, or the group recreating Harrison's RAS Regulator, or the re-creation of "Rocket".

Michael Gilligan03/04/2012 22:25:49
avatar
14139 forum posts
616 photos

John,

Yes, you are right ... the problems were substantially solved.

What is interesting, and a little depressing, is how much of that knowledge has since been forgotten or ignored. That's why, every once in a while, we need to dig through the history.

MichaelG.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
TRANSWAVE Converters
Ausee.com.au
cowbells
Eccentric Engineering
Meridienne; London MES
Eccentric July 5 2018
ChesterUK
Warco
Allendale Electronics
emcomachinetools
Subscription Offer

Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest