files with a convex surface?
bugbear
filing flat a cast iron surface; the process
I'm trying to improve on is written up here:
http://www.geocities.com/plybench/flatten.html
Since most tapered file only taper
towards one end, there is a transition
zone from parallel to taper. It is
this zone that I need for my process.
What I'm looking for is a file where this
zone is large and well defined.
Sadly the details of the tapers
(in width and depth) in catalogues
are not detailed in this respect; they
just say "tapered"
Does anybody know which file would suit
me best?
BugBear
Pat March
Tony Jeffree
Colin MacEke
Bob May
sandpaper so that the tool hangs over each end of the paper.
Next is to get rid of the sandpaper and use loose grit. Loose grit can be
obtained in well graded sizes from the astro community. One place is
www.gotgrit.com but any optical supply place can provide 2Kg sized bottles
of it. Opticians make 1/20th wave (of light) or better accurate flat
surfaces regularly.
You also want to work the plane in only one direction rather than back and
forth for best results.
--
Bob May
Global WARMING???
What I want to know is when I can start growing wheat in Greenland again!
Dave W
@posting.google.com:
You might try scraping again with a less expensive granite surface plate
instead of the glass you were using.
http://www.leevalley.com/wood/page.asp?page=32526&category=1,43513
&ccurrency=3&SID=
Mind the wrap...
--
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James Wilkins
> I'm try to find the best file to use for
> filing flat a cast iron surface; the process
> I'm trying to improve on is written up here:
>
> http://www.geocities.com/plybench/flatten.html
> BugBear
Actually you can bend a file enough with hand pressure to make it file
only where you want it to. Pull up with the left fingers at the tip
and push down with the thumb further in. Or you could tie two together
at the ends with a nail sandwiched in the middle to bow them. Place it
on the work and rock it sideways to get a feel for where the contact
area is before taking a cutting stroke. Some cheap imports come
pre-bent already.
jw
Mike Whittome
Back at the beginning of the year we had an interesting discussion on
apprenticeships - with particular reference to drill grinding.
However, I seem to remember that filing came before drill grinding in my
case, and lasted for an interminable number of weeks!
Prior to choice of file, the height of the work piece is most important
- little guys had thick duck boards! A good rule of thumb is that the
top of the vice (i.e. work piece in most cases) is the height of the
operator's elbow. This ensures at least half a chance of the file moving
in a level straight line across the work surface if the file is
correctly held.
In order to produce a flat surface the file must be kept level for the
duration of the stroke. This is probably the hardest technique to
master in the whole of engineering. Good steady controlled strokes are
the order of the day, at a striking rate of 60/80 strokes per minute.
Keep the file clean by regular use of a file card, and a corner of
aluminium or copper to remove stubborn spoil in the teeth.
Stop frequently to check with a straight edge - its much easier than
removing a well established carriage roof! Turning the work piece so
that the strokes arrive from a different direction I find to be helpful,
and the pattern on the surface gives clue to what is happening and where
the removal is taking place.
Nothing is ever going to get flat until this technique is mastered. No
two 'filers' do it quite the same, but the skill has to be learnt and
practised just as well.
So far as choice of file is concerned there is little , if any,
difference between a flat file and a hand file so far as filing a flat
surface is concerned. My personal choice is for a hand file - i.e. the
one with the square end. The grade is of course according to the amount
of metal being removed, and the initial surface of the work piece.
Working ever towards a smother 'fine' file which gives a greater control
over the elusive flatness.
Please believe that I am not trying to teach anyone to suck eggs, preach
to the converted, or even be a clever-clogs! Very few these days get
the wonderful apprenticeships that were available in the forties and
fifties, which is very sad. Watching some young workers, who have had
no instruction, wield a file, or work furiously with a hacksaw males one
weep. It is not their fault, the generation in front equally has not had
the satisfaction of learning these skills, or even of appreciating that
the skills exist. Thus little if anything is passed on.
Thank goodness for Model Engineering which gives at least an
unstructured apprenticeship to just a few who take to it. Also for
this NG which does a lot to disseminate Best Practice (often from the
roof of a Reliant)
Sob! Sob! :)
Mike
--
Mike Whittome
J. K. Siddorn
will insist on flogging away with a hand saw whilst cutting major joints in
English oak - the wood is 10" square and some tenons need to be ripped down
two feet.. Their technique is to push hard and use the middle of the saw.
Arrgh ... Still, I am making some headway as I get asked to do the difficult
cross bracing joints as I am seen to be accurate. Ho-ho.
My dad taught me to saw properly and then a sadistic woodwork teacher taught
me more with his loathsome length of square yew beading than any number of
nagging words from the softie metalwork teacher next door.
In the early days of my apprenticeship with a medium sized firm of gear
cutting specialists, in between running a 20,000 batch of cast steel bosses
through the slotting thumper, old Malcolm taught me to saw steel, brass,
copper et al and then file up cubes with flat faces. God how I hated that
man! But I can still do it ;o))
Regards,
Kim Siddorn
"Non est tanti."
"Mike Whittome" <mi...@windling.demon.co.uk> wrote in message
news:qiSILTAX...@windling.demon.co.uk...
Mike Whittome
Kim. Siddorn writes................
>But I can still do it ;o))
Its like riding a bike Kim, that's the joy - you never forget!
Mike
--
Mike Whittome
Tony Jeffree
<mi...@windling.demon.co.uk> wrote:
>Kim. Siddorn writes................
>
>>But I can still do it ;o))
>
>Its like riding a bike Kim, that's the joy - you never forget!
What's a bike? ;-)
Regards,
Tony
bugbear
>
> http://www.geocities.com/plybench/flatten.html
>
Thanks for the various replies. I would like
to point that I haven't got a "proper" surface
plate, due to cost.
And I'm asking about files because I *tried*
scraping and found it slow (I have around 10 scrapers
at last count).
I can't "directly" file the surface. It's too big
(2 1/2" x 9") and I'm not skilled enough; I'm aiming
for flat within a thou or better.
In short, I am reasonably happy with the process
I'm using, I just want a better suited file.
I may get a small flat file at the next car boot and try
to bend it - safety specs on , I think.
Rifflers capable of cutting metal (as opposed
to the scultors ones, for wood) are a tad pricy
for my taste.
Bugbear
Andrew Mawson
"bugbear" <pwo...@engage.com> wrote in message
news:7435f6f0.02110...@posting.google.com...
Bugbear,
Why not find someone close to you with a surface grinder and give it a light
skim ?
If you are in the London area you are welcome to use mine.
Regards,
Andrew Mawson
Bromley,
Kent UK
Mike Whittome
>>
>>Its like riding a bike Kim, that's the joy - you never forget!
>
>What's a bike? ;-)
>
--
Mike Whittome
Mike Whittome
Hi Bugbear,
Tell me to .....off or go away if you wish. I am replying direct since
the last thing that I want to do is to embarrass or cause offence.
Honestly, re-read my long reply, and try to put some of the things I
said into practice. It is very possible to file a two and a half by
nine surface flat if you have a mind to do it. The very first piece
that I ever did was about two by seven. They gave us a piece of rusty
two by one bar, and three weeks later we had filed it into a very pretty
and very square machine clamp. No excuses were accepted, and it was
well within your one thou. In passing - you can see light through a
quarter of a thou with a straight edge against the light.
You need a ten or twelve inch second cut 'hand' file to do most of the
work. Put the work piece in the vice, with soft jaws if necessary, and
make sure that you are standing so that you can just rest your elbow on
the job. Hold the file in the right hand, thumb on top, and then take
hold of the end of the file with the left first two fingers and thumb,
with the thumb on top and the first finger against the end of the file.
Take nice steady strokes across the face of the job, so that the area of
contact moves diagonally across the face from closest left to farthest
right. Watch the file marks develop because these are the best
indication of what is happening. After a dozen or so strokes change to
the other diagonal.
The clever bit is of course to keep it flat! Check now with a straight
edge, both straight across and diagonally. The chances are that you
will be developing a 'carriage roof', that is what you have to get rid
of, and the only way is keeping the file level through the length of the
stroke. Nobody said it was easy - it bloody isn't! ;). It may take
all day Sunday to achieve even a moderate success first time. Don't
let the carriage roof develop - try to file the top off it! Watch the
marks the file is making. Check every couple of dozen strokes or so -
specially at the beginning. Eventually the pattern will tell you when
to look.
Keep the file clean so that it does not start to pick up.
Success will gradually start to come, and then it starts to get
rewarding. Then you will begin to have a skill that not a lot of folk
possess in this day and age.
Those who talk to you of 'bent' files for doing this work are talking
twaddle, files are meant to be flat. Do not try to bend one or it will
shatter, they are both enormously hard and enormously brittle. That is
how they come to be files. You need the length I have mentioned to
give a decent stroke.
Scraping is another skill entirely, and is of no value until you have
achieved you stated aim of better than a thou. Scraping removes
minuscule amounts of metal. When scraping a flat surface flatter, then
is the time to use a surface plate. A piece of old mirror is quite
flat enough for the purpose here, anything more expensive is like using
a micrometer to measure a piece of rope - it will do the job but is
totally un-necessary! The reason for using blue is to mark the high
spots, which you then scrape away and try again. You have to do a lot
of filing before you even need to think of this.
Scrapers stay in the drawer, with the ends carefully protected (like
wood chisels). They are tools of great accuracy, or more correctly to
produce great accuracy and should be treated with infinite care.
Sharpening them is another skill to learn. I still have one of my
first ones, made from an old six inch file. The action of using a
scraper is rather like signing your name - you end up doing that little
(gentle) squiggle without out really knowing how you do it. You just
suddenly develop the technique. You can recognise the pattern of some
peoples scraping on the metal surface. It is a very gentle process
with no force whatever - the scraper does all the work.
I see that Andrew Morson offered a surface grinding facility, and if you
just want to get whatever it is flat for another project then his or
someone else's grinder is the way to go. If you want to achieve the
skill then I would be happy to talk to you again if I can help.
In conclusion, I am afraid that you will not get a good twelve inch
second cut or fine file for tuppence-halfpenny they are quite expensive
these days. You really need both, as you progress you will need the
fine one too. Get good file handles also, it is dangerous to use
anything that is cracked or broken, or worse still try to use a file
without one - unless you want to dig it into your hand.
Oh yes, I forgot to mention the blisters - seriously you can expect a
few during the initial stages.
Bugbear, I hope I have not put you off, that is not the intention. But
to learn to file is like learning a musical instrument, to do it
properly requires practice, and lots of horrid noise in the early
stages.
Shout at me if you wish, you have the email address.
Good luck,
Mike
Just for the record I served my apprenticeship at AEC in Southall. They
built most of London's buses in those days. 1953-57. We used to
think of ourselves as the Rolls-Royce of commercial vehicles! I don't
think we were far off.
--
Michael Knights-Whittome - Practically an Engineer!
mi...@windling.demon.co.uk
Adam Smith
Adam
Mike Whittome wrote:
> Hi Bugbear,
>
> Tell me to .....off or go away if you wish. I am replying direct since
> the last thing that I want to do is to embarrass or cause offence.
>
...