Having stated that this is aimed at the lathe only workshop, by which I mean no milling
machine, I do anticipate there will be a small drilling machine available. Obviously,
there is a minimum size lathe that can accommodate the project but with the Hobbymat
I am using, having a centre height of just 65mm, it should be a possibility for all
but the smallest lathes. Only the Box Bed (29) and the Soleplate (11) of the 10H
were on the borderline.
Of course, the methods suggested will be equally at home on larger machines but working
with a small lathe does place extra complications on some tasks so the methods used
will be taking account of this fact. Typically, the use of a few very simple fixtures
for mounting some of the parts onto the small size faceplate that the smaller lathe
has. I do though consider that in most cases the methods will be the best approach
even on a larger lathe.
As this is primarily aimed at those with limited experience I have gone into rather
more detail than would normally be the case in the Model Engineer magazine. More
experienced workshop owners will I think find some of the methods used of interest
but can bypass the details on the basics should they wish.
The first task, and a vitally important one, is to study the drawings carefully,
both the exploded assembly and individual part drawings, ensuring that they are
fully understood. This is important as whilst the drawings are very clearly drawn
some aspects for a particular part have to be established by reference to the drawing
for another. To help understand the content of these pages take a print of the 10V
exploded assembly drawing
The kit comes complete with all the materials including hardware items, but it is
likely that there will be thread sizes for which you do not have the required taps
and or dies so make a list of the tools required and take this to the workshop and
check if you need to purchase any. This includes checking that you have the tapping
drills sizes for the threads to be made. There are three sizes 8BA (1.9mm) 7BA (2.1mm)
and 5BA (2.7mm), the sizes in brackets being the tapping drill sizes that I used.
If you want guidance on the drill sizes to use in other cases this can be found
elsewhere on my website.
Also needed will be some spanners, flat, and ideally box. These are for the 7BA
screw heads and nuts which are nominally 0.172” AF.
In the case of lathe tools some carbide tipped tools are to be preferred in view
of there being iron castings to machine. The newcomer may be unaware that cast iron
castings can have hard spots that may play havoc with your HSS cutters and even the
carbide tipped tools may struggle unless the machining can get below the hard area
which, if present, is almost always on the surface.
With the part projecting appreciably from the faceplate in some cases only very light
cuts are acceptable, and as a result, in just two cases, I found even the carbide
tipped tool could not remove a hard spot present. This may not be immediately apparent
whilst machining is taking place but can very easily be spotted afterwards by the
offending area having taken on a glazed look and being above the level of the surrounding
surface due to the tool springing.
If this happens you will need to remove the part and grind away the effected area.
However, do take care not to remove too much as you may end up below the level that
the part has to be machined to. On the other hand, you will not want to remove a
very small amount only to find that there is still a problem when returned to the
lathe. The easy way to avoid this is to test the ground area using a scriber, if
the scriber skids over the surface more needs removing.
As HSS cutters will be sharpened in the workshop I will not comment on them here
other than to say that their general shape should follow those of the carbide tipped
tools that I am suggesting. With regard to these the following would be ideal. If
you are apprehensive about forming and sharpening HSS lathe tools, my book, “Tool
and Cutter Sharpening”, number 38 from the Workshop Practice Series may be of help
ISO5 Right Hand, for machining right facing surfaces.
ISO5 Left Hand, for machining left facing surfaces.
ISO3 Outside diameter turning.
ISO8 Through hole boring tool.
If needed, details of these tool shapes can be found in my book “Metalworkers Data
Book” number 42 in the Workshop Practice Series. 217 pages of useful information!