Model Engineers’ Workshop – July 2019

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Chop Saw

July 2019

to cut reasonable sizes of sheet metal and
plate, not just bar stock, so it was essential
for me to be able to slide the angle grinder
accurately in a straight line.
The recycled saw table-top shown in
photo 2 was 305 x 290mm, and obviously
it would be unlikely that other readers
would fi nd a similar item to be recycled.
However, this article is not intended to be
a blow by blow account of how to make an
identical item but to give readers ideas as to
how a similar item could be constructed. My
table had a substantial cast iron surround
on it, so that a slot could be ground across
the top without destroying the integrity
and strength of the base. In the absence
of a base such as mine, a suitable base
could be constructed out of angle iron and
a sheet metal top, either by welding or
riveting. Alternatively, the base could be
made from thick ply and a steel channel
rebated into it across the length of the cut
line. However, this is to be constructed,
it is important that there is a place for
the grinder blade to cut right through
the surface of the base, without setting a
wooden base on fi re.

The Choice of Angle Grinder
Most builders would probably utilize an
existing angle grinder from their workshop,
but I saw a new angle grinder in a local
budget store for the unbelievable price
of £18.00. It seemed to be ideal for my
purposes. The name of the grinder is
“Saber” and this is shown in photo 3.
If you are using an existing angle grinder,
then you will have to design your own
mounting system, but the Saber grinder
has the advantage of having three positions
where one could attach the handle, one on
the top and one on each side. This meant
that I could use two mounting points to
attach a mounting bracket and use the third
to attach the supplied handle which came
with the grinder.
I had some aluminium channel 100mm
x 50mm x 5mm thick which I had acquired
when I removed a domestic elevator from
my parent’s house. I cut a 110mm length
of this and removed one side to make
an aluminium angle 100x50mm. You will
see that, in photo 3, I have milled away a

“window” from the 100mm side, to allow

the angle cradle to fi t snugly to the top of

the grinder and to allow access to the on/off

switch. I was pleased to fi nd that the top of

the grinder was fl at, and parallel to the blade

where the mounting point was situated,

thus ensuring a rigid mount. The grinder

handle uses an M8 thread, so the cradle was

attached with two M8 countersunk bolts.

The rear corner of the cradle was drilled and

tapped M8 ensuring that the tapped hole

was absolutely square to the aluminium

surface of the bracket. A 120mm length

of 8mm silver steel rod (drill rod to our

American friends) was threaded in the lathe

and screwed tightly into the tapped hole.

An M8 Nyloc security nut was fi xed to the

underside to act as a locknut and there was

just room to accommodate this underneath

the bracket. This rod is to act as a swivel

shaft to allow the grinder to swivel on the

sliding rail to give the “chop saw” action to

the movement of the blade.

Great thought was given to the fi nal

relative positions of the blade centre, the

swivel rod and the height of the sliding rail.

This paid off by eventually fi nding the action

of the device both comfortable and practical

in use. I am not including any drawings as

this tool was designed around “what was

available” but, to help a prospective builder,

the radial distance between the swivel

shaft and the grinder spindle, is, in my

case, 140mm. Please ignore the hexagonal

section on the end of the swivel shaft , it just

happened to be there!

The Slide Rail

The next task in the design was to decide

how to slide the angle grinder back and

forth and at the same time being able to

adjust the height of the grinding wheel

above the table. I did consider using two

parallel tubes on which to slide the grinder,

but I was concerned about grinding dust

clogging up the sliding surfaces. I also

debated whether the sliding rail should

be able to hinge up and down as in a chop

saw, or whether to make the sliding rail

fi xed, parallel to the base, and create a

swivel action on the grinder as it slides on

the rail to control the depth of cut. Any

reader building this will have to decide what

method to use according to which materials

are available and the engineering facilities

to hand.

For what it is worth, I considered using

heavyweight ball bearing drawer slides and

3 4

5

Saber’ angle grinder with mounting cradle Slide rail arrangement

Front edge of the slide rail