Post by Dave BakerPost by newshoundThe local brewery uses immersion heaters in the hot liquor tank. This
runs at about 78 C so develops a fair amount of limescale. Any idea where
we might find a 2 1/4 bsp thread chaser to clean up the threads when
replacing elements? (£300 for a "proper" tap is a bit of an investment).
I'd wondered about fabricating something from three or four 5/8 BSW or
UNC taps (which also have 11 tpi) on an adjustable or "soft" mandrel.
Tank and bosses are stainless, so hydrochloric acid not a good idea.
(Chief beer taster. I get to check a pint out of every barrel they
produce. £50 a week; not much, I know, but it's all I can afford)
As has been suggested the standard trick to make a "poor man's tap" is to
grind flutes into any bolt or fitting of the same thread size such that A)
the flutes are completely below the root diameter of the thread and B) the
leading edge of the flute is vertical in the clockwise direction so it
acts as a cutting edge just like a proper reamer.
I make these routinely for non standard thread sizes for cleaning out bolt
threads in engines using old bolts and the edge of the wheel of my bench
grinder. You only need to flute the first few threads for it to work
nicely. They'll clean out crap and corrosion and even correct light damage
in soft materials although of course they won't cut a new thread like a
proper hardened tap.
Alternatively as the tanks are stainless steel not soft brass you could
use a small rotary wire brush in an electric drill such as these.
http://www.tool-wise.com/products/spindle_mounted_crimped_wheel_light_duty/index.html
One of those would whiz through limescale without hurting the thread
itself. I use those in my high speed rotary grinding equipment for
cleaning out cylinder heads and engine blocks. You can get smaller ones
for use in Dremels and similar and in fact the high speed of the Dremel
would maybe make it worth getting one of those too. A cordless one like
this
http://www.argos.co.uk/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=1500002201&productId=1500642739&langId=-1&engine=froogle&keyword=Dremel+Lithium-Ion+Cordless+Rotary+Tool&_$ja=tsid:11527|cc:|prd:0072492|cat:Power+Tools
would make it easier to use without having to rig up extension cables to
each tank. Dremel do their own brushes in carbon steel, stainless steel
and brass. Brass would be very gentle on the steel of the thread while
still removing the limescale although I doubt they'd last very long.
Ideally for a steel brush you'd want wire of 0.3mm diameter or less. The
0.35mm wire is more aggressive and less able to reach into the roots of
the threads. With 0.3mm wire brushes I can even clean up aluminium
cylinder heads without marking the alloy if I don't run the brushes at too
high a speed. With 0.35mm wire it tends to scratch a bit at high speed
although on stainless steel it would be fine.
Be aware though you do tend to lose strands of wire from time to time so
you'd need it to not be a problem if one of those fell into the tank. I'm
sure everything is filtered at some later stage though.
http://www.dremeleurope.com/gb/en/start/index.html
--
Dave Baker
coming up so might just drop hints around the family.
But I'll also try to knock up something from an old element.
you say they don't last long. I'll order myself some better ones.
hops which would probably catch any lost wires. Also, it's "real", i.e. cask
layer at the bottom, and anyone who drinks that probably wouldn't notice....