Handy
Hint No 1 - Centring work in the Four Jaw Chuck:
There have been many methods described over the years in the pages
of the ME and EIM for centring work in the four jaw chuck. Most
of them require some sought of gadget to be constructed, ranging
from quite complex to reasonably simple.
The following method which was shown to me many years ago by Mike
Chrisp, now Technical Editor of ME, only requires a DTI ( Dial Test
Indicator) and two tail stock centres.
Method
Place the material to machined in the four jaw chuck and centre
as accurately as possible using one fixed centre in the tail stock.
When satisfied, place the second centre between the fixed centre
and the work locating the tip in the centre pop. Position the DTI
on the second centre as close to the work as possible and adjust
the jaws of the chuck until the DTI reads zero
If the centres are in good condition it is possible to achieve a
fine degree of accuracy but bear in mind you are wasting your time
if the centre pop is out.
Handy Hint No 2 - Accurate marking out:
I often wondered how the clockmakers of earlier years managed to
mark out and drill the holes in the front and back plates of a clock
so that all the wheels ran freely. When I came to make my own clock
I realised that that they did not mark out as such but set the wheels
and arbors in their correct running position in a device called
a depthing tool. This was then used in a similar manner to a pair
of dividers to position the centres of the holes.
As Baldrick would say " a cunning plan".
Unfortunately I have not found a similar device for use in marking
out the location of holes to be drilled in general engineering items
but have to rely on hand tools and a good eye. Having said that
one piece of equipment which I find invaluable is a Jewellers loupe
with a times 10 magnification which I use to check the position
of centre pop marks before drilling.
Method; Clean the surface of the metal with a drop of meths or turps,
coat the surface with marking blue. A broad marker pen from W H
Smiths is ideal for this job, for castings use thinned emulsion
paint.
Use whatever method is appropriate to position the co-ordinates
which locate the centre of the hole. Push the scriber, point first,
along one of the co-ordinates and you should feel the point where
the second one crosses it. Bring the scriber up to the vertical
position and twiddle it round between the fingers. This will form
a small indentation which can be checked with the eye glass. If
the spot is not accurately located at the intersection of the co-ordinates
lean the scriber over at a slight angle, twiddle it round again
and move the spot into the correct position. Use a punch ground
at an included angle of 60o to form the centre pop mark, check again
with eye glass. Leaning the punch over at a slight angle before
striking with the hammer will also move the centre pop mark if needed.
Finally, scribers and punches are cutting tools and as such should
be finely ground and honed to a keen edge. Store them by pushing
the points into a block of polystyrene
Handy Hint No 3 - Two hints this time one for setting the height
of a lathe tool, the other for lining up the centre of a drill or
milling cutter with a previously marked centre:
1. Setting the height of a lathe tool.
Place a piece of circular bar in the chuck and set the cutter to
the approximate height by eye. Trap a 6 ins rule between the cutter
and the circular bar if it leans back at the top then the cutter
is too high, if it leans forward then it is too low. Correct by
adding shims or what ever.
The accuracy of this technique will be improved if the material
is truly centred in the chuck by turning.
2. Lining up the centre of a drill or milling cutter with a previously
marked centre.
Place a piece of rod ( about 6 mm dia.) in the chuck with a small
piece of blue tack on the end. Press a dress makers pin head first
in to the blue tack and start up the machine. While it is still
running use your fingers to make the pin run true, once this is
achieved use your eye glass to line up the co-ordinates on the material
with the pin. The centre line of the tool and the hole to be drilled
are now in accurate alignment.
There in no need to use a centre pop just line the pin up with intersection
between the two co-ordinates and start the hole with a centre drill.
Handy Hint No 4 - Dividing in the lathe:
The Bull Wheel which forms part of the back gear in the headstock
of a Myford Super Seven has 60 teeth, which, with a suitable adapter
can be used as a dividing head.
This technique can be used to mark out the ring of holes on cylinder
end covers or anything which requires a ring of holes located on
a pitch circle. If you are fortunate enough to own a toolpost drill
it is an easy process dispense with the marking out, and drill the
holes without removing the stock from the lathe. It is also possible,
with the aid of a filing rest, to form the squares on the end of
valve spindles or clock winding arbors.
The adapter which is shown in the following diagram, bolts on to
the lathe headstock using the 3/8 ins BSW tapped hole situated at
the rear of the spindle nose and intended for the chuck guard.
Check that the key dimensions are correct for your machine.
Once in place the 3/4 ins diameter cross member should position
the detent so that it engages in the gullet of the teeth.
It is worth marking the side of the Bull Wheel with different coloured
felt pens to indicate the more common pitches.
The adapter is easy to make and you will wonder how you ever managed
without it.
Handy Hint No 5 - Turning small diameters:
On occasions there is a need to produce items on the lathe with
quite small diameters. For example; special BA screws or bolts or
pivots on clock arbors.
Short lengths are usually possible providing that the cutter is
sharp and set exactly on the lathe centre and they are not too long.
Anything above a 1/4 inch long usually tries to climb on top of
the cutter or ends up tapered.
The tool shown in the drawing will produce very small diameters
of almost any length and keep to tight tolerances.
The main body of the tool can be almost any size providing that
it can be held in the toolpost. The milled slot in the side needs
to be positioned so that the cutter which is held in place by two
grub screws, lies on the centre line of the lathe . The Allen cap
screw at the rear provides a fine adjustment for the cutter.
The button which is held in place by a small grub screw can be made
of brass or Silver steel ( Hardened or unhardened ) depending on
the quantity of items to be made. The hole in the centre is drilled
to suit the parent stock.
In use the tool is held in the toolpost and the hole in the button
is lined up with the parent stock and the cutter is adjusted to
produce the finished diameter.
If countersunk headed screws are required just grind the corner
of the cutter away to the appropriate angle.
Handy Hint - No 6 - Two hints this time one for setting the height
of a lathe tool, the other for lining up the centre of a drill or
milling cutter with a previously marked centre:
1. Setting the height of a lathe tool.
Place a piece of circular bar in the chuck and set the cutter to
the approximate height by eye. Trap a 6 ins rule between the cutter
and the circular bar if it leans back at the top then the cutter
is too high, if it leans forward then it is too low. Correct by
adding shims or what ever.
The accuracy of this technique will be improved if the material
is truly centred in the chuck by turning.
2. Lining up the centre of a drill or milling cutter with a previously
marked centre.
Place a piece of rod ( about 6 mm dia.) in the chuck with a small
piece of blue tack on the end. Press a dress makers pin head first
in to the blue tack and start up the machine. While it is still
running use your fingers to make the pin run true, once this is
achieved use your eye glass to line up the co-ordinates on the material
with the pin. The centre line of the tool and the hole to be drilled
are now in accurate alignment.
There in no need to use a centre pop just line the pin up with intersection
between the two co-ordinates and start the hole with a centre drill.
Handy Hint - No 7 - Filing Buttons:
There are many components in Model Engineering that comprise a length
of metal with a hole drilled at each end and rounded off to suit
the hole. Coupling rods are a good example but there are many others.
The Martin Evans method of placing the component on a pin and turning
it against a revolving cutter on the milling machine seems to me
to be a bit hairy. A safer way particularly with large components
such as those found on valve gear would be to use a revolving table.
However, small items are still a problem as they are far too small
to hold by hand and may be difficult to secure on a revolving table.
One solution would be to use a pair of filing buttons
Method;
Lets assume that the item to be made is 1/2 " wide by 1/8 "
thick material with a 1/8" hole drilled on the centre line
1/4 " from the end. This is finished off with a semicircular
end taken from the centre of the hole.
To make the filing buttons you will need a length of 1/2 "
Silver Steel. Place this in the lathe, face the end and drill a
1/8 " hole 1/2 " deep. Part off two discs approximately
1/8 " thick. Remove any burrs and harden them right out by
suspending them on a piece of wire, heating them to cherry red and
immersing them in cold water. There is no need to temper them.
To use the buttons, place one either side of the hole in the metal
strip and bolt together with a 5 BA nut and bolt. Use an old file
to remove the waste and finish with a suitable grade of emery paper.
Always keep an old file just for this job as the hardened buttons
will soon ruin a new file and when drilling the hole always check
that you have a bolt that is a close fit.
Finally, keep the buttons and the nut and bolt together in a tin
or whatever, you will be amazed how many times you will find a job
for them in the future.
Handy Hint No 8 - Chatter free Countersinking:
Producing a chatter free recess for a countersunk headed screw can
sometimes be a problem. The traditional rose bit counter sink is
usually the main offender and seems to leave a corrugated recess
in metal or wood whatever speed is used.
A simple modification can sometimes bring about an improvement.
This involves removing every other tooth on the grinding machine.
Aim to finish with an odd but evenly spaced number of cutting edges
and run it on slow speed.
Try it on an old cutter and see if it works.
Alternatively, make a D - Bit with the end turned to a 45 degree
included angle. Again run it on slow speed with a spot of cutting
fluid applied with a brush. This method is very successful but the
cutting edge needs to be kept sharp, otherwise the cutting action
raises a small burr round the recess which will need to be removed
before fitting the screw.
Handy Hint No 9 - I visited Reeves at Birmingham recently and picked
up two tips which I think are worth passing on:
1. If you follow Martin Evan's advice and use brown paper to make
gaskets, the grade of paper used by Reeves to wrap up your goodies
is just the job. It is a heavy weight paper and when soaked in oil
makes a first class gasket.
The disadvantage is that you will have to buy something first.
2. The steps leading up to the cab on locomotives, and there are
usually four sets on both the tender and locomotive, have a diamond
pattern none slip surface. If you would like to reproduce this in
five inch gauge then the plastic banding used on heavy parcels has
exactly the same pattern.
Either stick a piece on each step with a suitable adhesive or use
an epoxy resin and when it has cured peel the banding away and the
diamond pattern will be left in the resin.
Handy Hint No 10 - Having difficulty reading your steel rule?
File a bit of cast iron, mix the dust with a drop of oil and use
the paste to clean your rule. The result should be a clean rule
with black easy to read markings.
Handy Hint No 11 - Filing:
If you have need to remove a lot of waste metal with a file the
quickest way is to use a large round file This will really cut the
custard. Once near the line finish with a flat file.
Having said that, the quickest way of removing metal by hand is
with a hacksaw and cut along the line in the first place.
Handy Hint No 12 - Vice Jaws:
An Engineers vice when purchased new will have serrated jaws fitted.
Usually these are far too aggressive for model engineering work.
The solution offered in the text books is to fit a pair of ' vice
safes'. These are more often than not of light metal construction
with a plastic [ Tufnol ] insert. In my experience they spend more
time on the floor than in the vice.
It is much better to replace them with jaws made from mild steel.
It is a simple job to remove the serrated jaws and use them as a
drilling jig to produce new ones of the same size.
Whilst you are at it why not make some extra pairs with vertical
or horizontal vees for holding round stock
Handy Hint No 13 - Holding thin sheet metal:
Holding thin strips of metal in the vice for filing or finishing
is always a problem. One technique is to place a thicker piece of
metal in the vice and hold the piece to be filed with double sided
Selotape.
Alternatively, if you made a pair of mild steel jaws as described
in Handy Hints No 12 then a shallow rebate milled along the top
edge of each jaw will do the trick.
If you are into a bit of tool making then you may wish to make a
proper 'Thin Piece Vice'. I acquired one from a club sale some years
ago and it has proved to be invaluable. There is an excellent description
in Model Engineer on how to make one by Tubal Cain. (Vol. 166 No.
3893. 1991 p.324.)
Similarly, the original was printed in the Model Engineer in September
20 1928 and reprinted in The Machinists Second Bedside Reader by
Guy Lautard on page 97.
Handy Hint No 14 - Tool stands:
Blocks of wood with holes drilled in the top face is a handy way
of keeping drills or milling cutters organised. So what's new ?
I can hear you say ? Well nothing, but do not use Oak or the tannic
acid which it contains will corrode ferric metals.
Secondly, on timbers where the growth rings are visible, drill the
holes on the heart side of the block so that they will open out
when the wood dries and not trap the tools, which may happen if
the other side is drilled.
For small tools such as scribers screwdrivers punches, etc. use
a block of polystyrene. Just push them in and they will be ready
for use when needed.
A chap I used to work with many years ago, used to insist that the
bench top was for working on not for the storage of discarded tools.
Not many people know that !
Handy Hint No 15 - Cutting small bolts or screws to length:
Nothing looks worse on a model than bolts or screws with badly finished
ends.
Lets assume that you have a batch of ½" shank bolts
which need reducing to ¼". You will need a section of
mild steel ¼" thick, the other dimensions are unimportant
so long as it can be held in the vice. Drill through and tap to
suit the bolt. It also speeds things up if the hole is opened up
with a clearing drill to at least half way through the thickness
of the plate.
To use, simply insert the bolt or screw, cut the waste portion off
and file flush with the plate. Hey presto! a batch of bolts all
the same length with finished ends.
A small piece of silver steel with two vees cut at right angles
to each other on the end, properly hardened and tempered will form
a small chamfer on the ends of the bolts if required.
John Wilding in his book 'How to repair Antique Clocks,' Vol. 2,
gives a detailed description on how to make what he calls a pin
chamfering tool which is a posh version of the above.
Handy Hint No 16 - Cross Drilling:
There are numerous methods of accurately cross drilling round stock,
here are four of them.
1. Place a piece of material in the drill chuck the same diameter
as the one which is to be drilled. With the machine vice floating
bring the head down and grip the round stock in the vice jaws.
Carefully secure the vice to the table.
Replace the piece of stock in the chuck with an appropriate centre
or drill and place the material to be drilled in the vice and away
you go.
2. If you need to cross drill lots of small pins similar to the
ones used on locomotive brake gear then this method will be useful.
Drill a hole centrally in the end of a piece of ½ "
x ½" bar. The diameter and depth of the hole needs to
be the same as the pin
Carefully mark out the position of the cross hole, and drill through,
using the same drill as required on the finished job.
To drill the holes, simply place the pins in the hole and drill
through.
It is important that the pins are a close fit in the drilling jig,
otherwise there is a tendency for them to roll and break the drill.
3. If you have access to a machine with a compound table such as
a milling machine, then this method can prove to be very useful.
Assuming that the vice is secured to the table and square in both
axis, place a piece of round stock the same diameter as the material
to be drilled in the vice and secure. Place a sticky pin in the
chuck and set it to run true. Using a good rule and a hand lens,
set the pin to run dead centre in the gap between the vice jaws,
and lock the table.
Replace the sticky pin with a centre or drill, similarly replace
the material in the vice with the piece to be drilled, and once
again you are in business.
4. Finally, using the same technique as described in 3, a light
milling cut across the round bar will leave a small flat this will
show the position of the cross hole. Use the Sticky pin to line
up the head.
Handy Hint No 17 - BA Threads:
If you still prefer to use number drills for use with BA taps and
have difficulty in remembering the correct sizes for tapping and
clearance holes then the following may be of help.
The rule of 4 :-
If you stick with even numbers then the tapping drill becomes the
clearance for the next smaller.
Tapping drill size Clearance drill
2 BA 24
4 BA 34 24
6 BA 44 34
8 BA 54 44
Not perfect but good enough and it saves having to look it up in
the tables every time.
Handy Hint No 18 - Filing lumps off:
If you need to file a small lump or bolt end down without scratching
the surrounding area, then take a piece of acetate sheet cut a hole
the size of the area to filed then place it over the work while
filing.
For small BA bolts place one of the sprocket holes in a piece of
35 mm film over the bolt end and Bobs your Uncle.
Sometimes it is difficult to reach a bolt in the centre of a wide
piece of material with a normal file. If this is the case try a
'Bulls foot ' file, These are available from any good clock makers
supplies, they are not expensive and it is the tool for the job.
As always you will wonder how you managed without one.
Handy Hint No 19 - Materials Storage:
If your workshop is a bit cluttered with lengths of metal lying
under the bench or propped up against the wall then make this your
next project.
An effective and inexpensive storage system for short lengths of
metal can easily be made using plastic pipe.
Obtain a length of 100 mm plastic soil pipe from your local Builders
Merchant or DIY outlet. Cut the pipe to about 450 mm long or to
suit the space available. Next you need to devise a method of holding
the pipes together, stack them between the legs of a bench or alternatively
make up a suitable wooden frame to hold them in place.
My own rack has two plywood ends with circular holes cut to hold
the pipes, the whole thing is mounted on castors so that it can
be moved about.
It is amazing what rolls underneath when I am not looking.
Handy Hint No 20 - Silver Soldering:
Holding complex fabrications together for silver soldering is always
a problem. The late George Kay showed me a method in which he used
1/16 " diameter welding rod as pins. The fabrication was assembled
using the pins in a similar manner to how a cabinet maker would
use dowels in a piece of furniture The trick was to leave the pins
slightly protruding which when hit with a hammer would expand in
the hole and hold the components together.
Needless to say do not forget to flux all the joints before getting
enthusiastic with the hammer.
All the frame stretchers on George's L M S Crab were fabricated
using this method.
For similar work I cut small grooves or housings so that the components
are accurately located and then hold them together with one or two
10 BA screws.
Finally, if you use silver solder in the fine wire form try threading
it through a length of small bore copper or brass tube leaving ½"
protruding
from the end. The tube will give you a lot better control of the
solder when applying it to the joint.
Handy Hint No 21 - Bending small channel or angle:
The joint between the spectacle plate and the boiler cladding is
usually sealed by a length of angle. On a full size locomotive this
would have been shaped to follow the contour of the boiler by a
skilled Blacksmith. Not a job for the faint hearted.
It is still a bit of a problem when the angle is only 1/8 by an
1/8 on a model.
The solution is to soft solder a strip of copper of similar size
inside the angle. This will prevent the section from distorting
whilst it is bent to follow the contour of the boiler.
Gently warm the angle to melt the solder and remove the now unwanted
copper strip.
A hot air paint stripper will apply just the right amount of heat
for this type of work.
Handy Hint No 22 - Filing Squares or Hexagons:
It is sometimes necessary to produce a square on the end of a piece
of rod. The end of a valve spindle where it is used to locate the
hand wheel and prevent it from spinning on the shaft is a good example.
A simple way to do this is to use a jig.
Take a short piece of square stock, say ½" by ½"
section, drill a hole in the centre of one end, the same size as
the spindle.
Drill and tap a second hole in one side and fit a small grub screw.
To use the jig, place the spindle in the hole and hold it in place
by tightening the grub screw.
Place the jig in the vice and file the first flat, keep turning
the jig over until all four flats are produced. The end of the jig
can be used as a
guide for the file to keep the shoulders of the four flats in line.
If greater accuracy is required, clamp the jig on to the milling
machine table and produce the flats using a small end mill.
If the jig is to be used on a machine then for the best results,
the hole in jig must be truly in the centre.
Using the same technique, bolt heads can be produced by making the
jig from a piece of hexagonal bar.
Handy Hint No 22 - Described methods of producing a square on the
end of a piece of rod:
The example given was the valve spindle of a small boiler fitting.
It follows that to complete the job a similar square hole will be
needed in the hand wheel.The most difficult part of the operation
is keeping the hole square. If this is a problem, try filing one
side at a time and turning the wheel 900 before filing the next
side. Use one of the spokes or a punch mark as a sight line against
the vice jaws to index the wheel.
If you have a number of hand wheels to make it may be worth making
a small broach, this will ensure that all the holes are all the
same size.
To make a broach, file a square on the end of a piece of silver
steel rod. Make the length about three or four time the thickness
of the hand wheel. Obviously the size of the square needs to be
the same as the one on the valve spindle.
Before hardening and tempering use a fine file to produce one or
two degrees of clearance behind the cutting edge.
The completed broach can be tapped through a slightly undersize
hole to bring it to size or pressed through using the drilling machine.
Postscript
Handy Hint No 23 - Producing small square Holes:
First drill a hole a few thou smaller than the square required and
using a square needle file remove four corners to form the square.
Watch the drill hole to judge how much metal is being removed and
whether it is square across the wheel. A three square file can be
used to sharpen up the corners.
Having written Handy Hints no's. 22 and 23 well in advance of publication
of the King Pin I noticed that Keith Wilson described how to file
squares on the end of shafts in the October edition of EIM.
By coincidence, in the September M E (No 4155) Stan Bray has described
how to produce small square holes.
Ah well !
Handy Hint No 24 - Hot Air Guns:
These tools are becoming increasingly popular and now relatively
cheap to buy. They were originally designed to replace the blow
lamp for paint stripping.
Hot air guns are also useful in other areas such as defrosting pipes,
shaping and bending plastics and with the correct adapters welding
plastics.
A standard 1600 watt gun can generate up to 1000 C which will easily
melt soft solder and make it flow along a joint. This is a very
useful method of sealing tender tanks. Similarly the same technique
will make an epoxy resin such as Araldite flow along a joint filling
every crevice.
If there are those of you who still like to make small tools from
silver steel. A hot air gun provides a much more controllable source
of heat for tempering or just bluing.
Handy Hint No 25 - Removing a Broken Tap:
Recently I broke a 6 BA tap in a cast iron cylinder block, fortunately
part of the tap was still sticking out of the hole so I felt I had
a chance of removing it with the pliers. No luck it broke off flush
with the surface.
In the past I have made hollow cutters for removing rusty nails
from wood when restoring a piece of furniture.
These cutters are easily made from silver steel and if correctly
hardened and tempered will work as well on cast iron and with care
on mild steel.
The diameter of the cutter will depend upon the size of the broken
tap, but as a rough guide add 1/16" to the diameter of the
clearance drill for the tap.
Using a clearance size drill, drill a hole up the centre of the
steel slightly deeper that the length of the broken tap.
Use a small file to form four teeth round the rim of the hole so
that it resembles a small holesaw. Which of course is what it is.
Harden and temper.
In use, ensure that the cutter is concentric to the hole, use a
slow speed and frequently withdraw the cutter to clear the swarf.
To finish plug the hole with the nearest available bolt and file
flush
Handy Hint No 26 - Machining Squares on round stock:
The following will give the depth of cut needed to produce a square
section on a piece of round stock. Where the diameter of the stock
is the diameter of the circle, multiply the radius by 0.707, subtract
the result from the radius and that is the depth of cut.
If you need to produce a square or hexagon on a piece of round stock,
the following will give the minimum diameter.
Square :- AF multiplied by 1.415
Hexagon :- AF multiplied by 1.083
Handy Hint No 27 - Injectors :- Known faults and their remedy.
Feeds to pressure but spills water.
Annular gap too large.
Tries to feed but steam comes from overflow
Gap too small.
Performance deteriorates
Needs de-scaling. (use dilute citric acid.)
Won't suck water.
Ball valve not seating.
Tries to feed but water and steam escape.
Bad concentricity
Works on test but not on model.
Water supply constricted or leaking.
Stops working on model and steam issues from overflow.
Clack valve leaking.
Handy Hint No 28 - Injectors :- A useful bibliography for those
who wish to make their own:
Keiller, SMEE journal Jan 1962
The definitive source of all.
Keiller, M.E. 14th Jan 1943.
No 80 delivery cone; the smallest model.
D E Lawrence’ M.E. Apr - Oct 1986.
A great collection of other’s ideas.
W A Carter’ M.E. 15th Aug 75.
Testing rig, every club should have one.
B Palmer, M.E. 7th May 79.
Sizing, Some useful variations of size.
R Amsbury, M.E. 17th Feb 84.
Adjustable steam cone.
Handy Hint No 29 - Turning Tapers:
To find the angle of a taper
1.
Measure the large and small end.
2. Subtract the latter from the former.
3. Multiply by 57.
4. Divide by length of taper.
Answer
is the included angle in degrees.
Handy Hint No 30 - Making Half Round Beading:
Two methods both involve using brass rod.
For the first method a small fixture is required. Take a piece of
mild steel about 2” by ¾” by ½”
(the dimensions are not crucial.) Drill a hole the same diameter
as the rod along the length of the MS block. About ¼”
from one edge. Place the block in the milling machine vice and using
a ½” fast moving cutter mill a slot at right angles
to the drilled hole until half the hole is exposed.
To use the fixture, simply feed the rod through the hole and adjust
the cut to produce the correct section of moulding required. To
stop the beading rolling over reduce the outfeed end of the drilled
hole by a half with a small clamp placed across the hole.
For the second method, a piece of large diameter tube or bar is
required, which has to be set to run accurately between centres
in the lathe.
To produce the beading coil the brass rod round the tube and clamp
the ends. Set the lathe in motion and reduce the section of rod
by a half.
I have not tried this method as yet, but two points occur to me.
The rod will probably need to be annealed and a method of holding
the ends of the brass rod will have to be devised. My suggestion
would be soft solder, plastic tape or jubilee clips.
Handy Hint No 31 - Tee Handled Hexagon Wrenches:
Tee handled hexagon wrenches are useful tools but expensive to buy
and usually only available in sets. In order to change the belts
on my Sharp milling machine I have to slacken off three socket cap
screws. Unfortunately a standard hexagon wrench is a bit too short
and does not provide enough leverage to adequately tighten the screw.
To make a tee handled wrench take a spare key and shorten it to
about an inch long. This is not as easy as it sounds as it is hardened.
Use a grinding wheel to make a nick all the way round place it in
the vice and knock it off with a well aimed blow from a hammer.
Remember, wear safety glasses and cover the end with a rag as it
will probably fly across the workshop.
Now, measure across the flats of the key and subtract this from
the dimension across the corners, divide the answer by 2 and add
it to the across the flats measurement. A drill of this size should
give a reasonable press fit for the key.
Next make up the Tee handle to suit your requirements. Using a drill
closest to the dimension calculated above drill a hole about ½“
deep in the end of the tee handle.
Grind a small taper round the cut end of the key and drive or press
it into the hole. Finally close the annular gaps round the key using
the vice.
For small keys a drop of Loctite (601) will improve things but on
larger keys a spot weld may be advisable.
Handy Hint No 32 - Improving accuracy with cigarette papers:
Cigarette papers are one thou thick, or near enough for our use.
Setting up the milling machine. Place the item to be milled in the
vice, dampen the face to be cut and place a piece of cigarette paper
on the surface. Move the cutter toward the material, when it whips
the paper away you are within one thou of the job. Set the dial
to zero. Do the same in the other direction and you can work to
co-ordinates without the expensive numerical control gizmos.
Testing the flatness of a work piece. Place the item on a surface
plate and trap pieces of paper between it and the surface plate.
With the tip of the finger try and remove the paper. The loose pieces
are in the hollows.
When using a square, trap pieces of paper between the top and bottom
of the blade, if one piece pulls out, the work is not square.
Similarly, the same procedure can be used with a straight edge held
against an edge.
Handy Hint No 33 - Parallels:
Parallels are nearly always required when setting up and can range
from the tool room variety which are very expensive down to the
cheap and cheerful made from short lengths of BMS.
The latter are easy to make and are accurate enough for most set
ups. The late George Thomas recommended that three sets of 8 pieces
each would cover most eventualities.
One set in each of the following thickness :- 1/8”, 3/16”
and 5/16”.
The height will need to suit the equipment available, mine range
from ¼” to 1 ½ “ in increments of 1/16”.
All the sections are available in stock sizes and just need cutting
to length.
Avoid reducing the width of a large section to create the smaller
as BMS will distort if cut and the accuracy will be lost.
Once made store them carefully and treat them as Precision tools.
If you have any money burning a hole in your pocket then a number
of the trade stands at the recent ME Exhibition had sets of wavy
parallels for sale at quite reasonable prices.
( I’m not going to attempt to describe what wavy parallels
look like.)
Handy Hint No 34 - Centre Punches:
Centre punches and scribers need to be sharp if they are to produce
accurate work. Here’s an easy method of restoring a worn point.
Place an ‘O’ ring over the end of the tool to act as
a stop then place the tool into the centre of a V- block.
Place the Vee-block on the rest of an off hand grinder at 300 (
or 450 ) to the wheel. Revolve the punch against the wheel keeping
the ‘O’ ring against end of Vee-block to control the
depth of cut..
It is worth finishing the point off with a fine oil stone.
Handy Hint No 35 - More on Files and Filing:
Filing soft metals such as copper or aluminium can quickly clog
up a file. The usual method of preventing this is to fill the teeth
with chalk. WD40 works just as well. Next time give it a try.
If you use a file to touch up work in the lathe, use a fine file
which has been dipped in a cutting fluid.
Filing long edges of sheet steel or brass when making plate work
can be difficult. The same difficulty arises when preparing joints
in veneers. The technique is to clamp two pieces of straight BMS
on each side and use these as a guide for filing.
For veneers substitute wooden straight edges for the BMS and use
a plane.
Safety. Never use a file without a well fitted handle.
