Model Engineers’ Workshop – August 2019

18 http://www.model-engineer.co.uk Model Engineers’ Workshop

Milling a large radius

Bearing removal recipe

Another Electronic

Leadscrew

Beam Design

Scribe a line

YOUR CHANCE TO TALK TO US!

Drop us a line and share your advice, questions and opinions with other readers.

Dear Neil, I read with great interest Richard Wightman’s “An eleven

inch Rotary table” and will am sure follow his example using a car

brake disc.

I am contemplating a similar project where an expansion link

is required for a 12” to the foot small stationary steam engine. A

much enlarged version of Richard’s set up will not be possible as my

milling machine throat depth is too small.

I have sketched up a method that might work. A rotary table is

used to move a jig plate in a semi circular arc. A pivot is locked into

the tee slot at the end of the milling machine table. A fi xed pin is

attached to the tee slot of the rotary which drives through a slot

in the jig plate. In addition, a pinch nut is added to this pin to keep

the jig plate lift ing during milling. Additional support will be needed

under the jig plate at the work end. Suitable bolt holes will be drilled

and tapped to the workspace end of the jig plate to suit the job.

Geoff Harding by email

Dear Neil, Regarding the article on removing bearings from blind

holes (MEW, July, page 29), the conventional use of grease tends

to be messy, as the author described. I was intrigued when

a friend told me that he uses papier maché made from paper

kitchen towels and water – it’s less prone to escape through the

bearing than grease. I’m wary that there’s often nothing new

under the sun (confirmed by Tony Jefree on page 26 of the same

issue) so, before presenting this solution to Scribe a line as a

novel idea, I resorted to Googling: “bearing removal with paper”.

Omitting the inverted commas produces numerous articles and

videos of that recipe and a variation using damp bread.

As Tony said: “Few ideas are really new.” I shan’t be applying for

a patent.

Ian Moignard, Jersey

Dear Neil, I can’t imagine that you are not aware of this, but just in case

(!) I’d like to draw your attention to this You Tube series. To my mind

it is being very well presented. Maybe you could give it a mention in

the magazine? I have no link or any other interest with the author and

James does not know that I am approaching you about this.

https://youtu.be/7QaQrqn4yeI

It may be that a commercial kit will become available - there has

been to my recollection no indication that this will happen despite

my lobbying for one.

Bob Hawtin, Hartsholme

Hi Neil, I’d like to congratulate Mr. Finch and yourself for

publishing such a comprehensive treatment. It’s an area I

studied many, many, moons ago and the first time I have

seen an author and a magazine editor with the ‘bottle’ to

publish an article on it.

I carried out a similar exercise for an existing rolled steel

joist in my garage some years ago. I my case the weakest

points were the two rather ‘flimsy’ brick piers holding up

the steel beam. Something I thought that could be readily

fixed with a couple of suitable builders acrows.

The methodology Mr Finch so carefully outlined is of

course applicable to many other areas where ‘beams’ of one

sort or another are proposed. Most workshop machinery

involves cutting tools suspended by beams - although they

are not always so easily recognised.

I suspect that it comes as quite a surprise to many people

that halving a beam length reduces the displacement under

a given load by a factor of eight - something to bear in mind

with boring bars and lathe tool holders.

I think this article has great educational value, far beyond

the already wide gamut of our interesting hobby. Hopefully

it will be picked up by technical colleges and universities

and it would be nice if Mr. Finch and My Time Media would

consider waving any copyright restrictions on its use.

Once again, well done the pair of you.

Bob Hawtin, by email.

Thanks for the appreciation, Bob. I believe that academic

institutions are allowed to make copies of single magazine

articles for educational purposes under existing copyright

law – Neil.