BORE HOLE IN THE BASE
Before starting this actual operation some decisions have to be made. Almost all
existing machined surfaces are to be machined, and as a result the vice would rest
lower at the handle end. This would be due to machining both the underneath of the
vice itself, and also the pads at the handle end of the base, on which it rests.
To overcome this, the pad could be raised by the addition of a pad, typically a large
flat headed rivet. This approach was rejected in favour of lowering the pivot pin
in the base.
It had already been decided to open up the holes and fit a larger pin, lowering the
hole added very little extra complication. The decision to increase the diameter
was due to the existing pin not being a good fit.
It will be required to place a long rod through the pivot holes on a number of occasions.
This is so that the part can be checked with a dial test indicator, to establish
that it is correctly positioned on the machine table. In view of this, preferably
chose a pin diameter for which a suitable rod is available, this will avoid having
to turn a long length specially. If a reamer is also available at that diameter,
ensuring the holes are a close fit will be easy.
If a reamer is not available, then first turn a plug gauge to the required diameter.
This will be used to test the bore, to see if it is at the correct size. Make the
gauge as is frequently advised, with one, or maybe two steps, at 5 thou. and 10 thou.
under size. These are used as early indication that the hole approaches its required
When machining the base of the vice itself, and the pads on which it rests, it is
probable that about 10 thou. will be machined from each. The hole in the base should
therefore be lowered by a little under 1/32 inch, this will also allow for the pin
to be increased in diameter by 1/16 inch. Of course check the vice to see if these
figures are appropriate for the one being machined.
Now set up the base on the lathe cross slide as shown in Photograph 1. It is essential
the the packing to bring the pivot hole to the correct level has parallel faces.
This is to ensure the the pin will be parallel to the base. If it is not, the accuracy
of the finished assembly will not be as required.
The holes can be bored using a top slide boring tool, mounted in a four jaw chuck
as shown. The four jaw chuck will enable adjustments to the hole diameter to be easily
made. Alternatively the hole can be bored with a boring bar between centres. The
latter benefits from greater rigidity, but then it becomes more difficult to test
the hole diameter.
Tee Slotted Cross Slide
If your lathe does not have a tee slotted cross slide, consider adding a plate secured
using the top slide’s fixings.
The plate can then be drilled and tapped to take fixing studs with which you can
secure the item being machined, the vices base in the above case.
You will of course need in some cases to add further tapped holes as new tasks for
the plate emerge.
Personally, I consider that all lathes in the home workshop should be equipped with
a tee slotted cross slide, or similar.