How to set a lathe tool height March 2011

Digital machinist work shop February 2011

Mark

Another member who wishes anonymity showed his results from
acid sharpening files. He found that a file card scrubbing of the file
followed by careful removal of any pins (I use a piece of brass sheet
attached to the back of the card) then followed by a thorough wash in
solvent was necessary for proper sharpening. I have boiled the file in
detergent and water as a final cleaning. Then etching in Hydrochloric
(Muriatic), Nitric, or Acetic (Vinegar) to sharpen. His best success
came with 54 hours in the Vinegar! At the next meeting I will be asking
for comments and reports on others efforts in sharpening files!
On another note I tried a trick of rubbing a fine oilstone over the
teeth of a fine file against the cutting direction. It will develop a
shine indicating that the tops of the teeth have leveled off. This file
now will take very fine cuts and leave a very smooth surface!

I will be sending a report on the meeting shortly. About 16 members
attended and several took home bargains! Bill

Ken, thought you might like to know that the web site is used
even from as far away as England. It is also a tribute to Google
that they will find stuff buried deep within a web site. I have also
received e-mail from a man in Wisconsin that had googled for
"Farwell Gear Hobber", and had questions for me. Truly amazing.

John B. Beall
303 424-8118 jbeall303@juno.com

From: "adrian gough" UK

Subject: Removing a broken tap from bronz casting.

Dear sir

I have been making a small beam engine of late. The cylinder was turned from
a piece of cored bronze bar. At each end are 8 holes all 10BA which is 1.4mm
tapping (about your number 0 ANF). It was the last but one hole that caused
the problem, I must have been getting careless as it all seemed so easy.

I had drilled the holes using a rotary table with a 4 jaw chuck mounted on it
and an expanding mandrel in the chuck. This meant that I could align the bore accurately.

To help align the tap I used a number 3 morse taper with a small spring
oaded conical plunger sticking out from it. The tap holder had a conical

center in the back so that the taper on the plunger located in the back of
the tap holder and kept everything at right angles. The spring kept
everything in contact so that the quill of the miller didn't have to be
moved when the tap holder was moved backwards and forwards. For the last but
one hole I took out this support early, then the tap snapped, leaving a
flush broken tap with nothing to grab hold of.

After asking friends at my model club in Bristol if anyone had had this
problem and drawing a blank, I turned to the internet typing in 'removing

broken taps' and up came your web site. You described using a chemical
called Alum whatever that is. I was fortunate that where I work we have a

few chemists I could talk to.

I found a supply of Aluminium Potassium Sulphate or Potash of Alum as it is
also known.
It seemed almost impossible to dissolve in cold water so I gently warmed the
water up over a small sprit lamp and as the water got hotter so I could
dissolve more crystals. Eventually I dissolved a suprising amount.

I then put in a small piece of brass just to make sure that this would not
dissolve. After about half an hour the brass was untouched.

I propped up the cylinder on this piece of brass to give clearance at both
ends of the hole: fortunatley it was a through hole. After a few seconds a
small stream of bubbles came from the blocked hole. As long as the
temperature was kept as close to boiling as possible then these bubbles
continued. After two and a half hours I could push out what was left of the
tap and had a completely undamaged cylinder.

So, very many thanks for the information.
Adrian Gough
Member of the Bristol society of model and expermental Engineers. UK

Bristol society of model and experimental Engineers. UK