26 http://www.model-engineer.co.uk Model Engineers’ WorkshopRust
Sub-Plates
Knurling
Southbend
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YOUR CHANCE TO TALK TO US!
Drop us a line and share your advice, questions and opinions with other readers.
Dear Neil, Chris Sayers-Leavy asks about liquids to get rid of rust. I
worked in the printing industry for years, and we used phosphoric
acid in the plate making process. we used a solution with it in. I
some how found the solution got rid of rust. That led me to try
phosphoric to get rid of rust. I had to dilute it with water, for it to
work properly. I can not remember the ratio but something like 25
% acid / 75% water. Always add acid to water!
You must clean with water to get rid of the acid, then coat with
oil, or primer. It rusts again in seconds. One good thing about
Phosphoric, it is not as dangerous as other acids, Sulphuric,
hydrochloric being two.John R. Yeoman, YorkDear Neil, I read with interest the article by Keith Keen about sub-
plates for workholding - a very useful idea and one that I will keep
in mind. It struck me while reading the article that an alternative
approach would be to drill/tap similar hole patterns in a lathe
faceplate; on a gap-bed lathe this would have the advantage that
larger diameters could be held for peripheral machining than would
be possible with the chuck.
Of course, very few ideas are really new - I discovered that later
in the issue, Geoff Harding shows a Unimat 3 faceplate drilled with
hole patterns for a very similar purpose!Tony Jefree, MullDear Neil, As a self-taught model engineer I continue to learn a
great deal from MEW. One discipline that eludes me however is
what I have heard is the “brutal art of knurling”. Every machinist I
have asked about this tells me that they have only ever done it on
large industrial lathes and that even then they were not comfortable
with the process. Reading various trades publication suggest
strategies that I have not found entirely helpful on a Myford Super 7
using scissor knurls.
To explain the mixed results I have had so far, I reasoned that if
a set of knurls was say 22 TPI, then the piece being knurled must
have a diameter (circumference) that supports this pitch much like
a gear wheel. Exploring this option, I placed a bit of 1”MS in the
chuck and supported the end with a tailstock centre. 1” bar gives a
circumference of Pi, and my knurls seem to have a pitch of 19.75TPI
so this works out at very close to 62 impressions around the bar. I
set the scissor knurls over the centre of the bar and fi nger tightened
the wheels against it. I then withdrew the top slide and closed the
knurls together by about 15 thou. Starting the lathe in top back gear,
I plunged the knurls fi rmly back over the centre of the bar with lots of
lube. The result was very encouragingly good but aft er I stopped the
machine and engaged a much higher speed for a few seconds, I was
surprised to fi nd the knurls self-feeding towards the chuck.
Should I be feeding in from the side of the job as some suggest
or doing as I have seen some demos on YouTube and just plunging
straight in? I ran the knurls over a piece of carbon paper on
cardboard to produce the image included. This seems to show the
pitch as 19.75 TPI (although advertised as 22 TPI) and also that
the impression is advancing around the wheels. Is the advancing
pattern normal?
I am hoping that one of your reader with experience and
knowledge might be tempted to prepare on informative article on
this subject as I am probably breaking every rule in the book and am
reluctant to impose heavy loads on my machine by experimenting
too much.Graham Lill, by emailDear Neil, You probably already have had a response but in the last
issue of MEW someone was asking about spares for a Southbend
lathe — I would suggest he goes on the Home Shop Machinist HSM
forum and asks the question, I feel sure he will get a response.
Southbend seem very popular over the pond and I understand
there are several clones so a good chance depending on what parts
he wants.John Fawcett, Lancaster