I was on the brink of buying myself a small benchtop vise, but then I thought: As it won't be used for heavy duty tasks, why not build one myself, and save a few cents? So this is what I came up with with cheap materials I had on hand.
Step 1: The Basic Idea
The first image shows how the vise works. The main frame, with a fixed jaw at the top, is clamped to the workbench, while the other jaw is mounted on parallel arms which can be adjusted by means of an adjustment screw to open and close the jaws.
The second picture shows the main parts before final assembly. The third picture shows the adjusting arms fixed to the main frame, and in the fourth picture the adjusting screw is fitted. The final picture shows the jaws being closed/opened by turning the adjustment screw.
A benefit of this design is that it has a small footprint. A con is that the movable jaw travels in an arc, which changes its height and angle as it is opened/closed. As long as it is not opened too wide, the change in height is not really a problem. The solution for the changing angle is to allow the jaw to swivel between its mounting points. The angle is then automatically adjusted when you clamp something between the jaws.
Of course the sturdiness of the vise depends on the materials used. If you just want to clamp things firmly, wood does a good job. But of course if made from metal the vise should have impressive strength.
In my case I used shelving pine (softwood) for the main frame, and for the jaws and adjustment arms I used hardwood, harvested from an unwanted thorn tree in my backyard.
Step 2: The Measurements
The picture shows all the basic measurements I used. Of course the size can be adapted to one's needs.
The main parts are all 40mm wide: The main frame, the jaws and the fixture (not visible in the picture) between the arms for the nut in which the adjustment bolt turns.
Step 3: Building the Vise: the Main Frame
Best is to first build the main frame, shown in the first picture. I used 45mm drywall screws and white (PVA) wood glue to fix the horizontal parts to the upright back part (second picture). However, I later had to replace the screws holding the middle part with wooden dowels, as the screws fouled the smaller screws holding the adjustment arms.
The distance between the two horizontal parts will depend on the thickness of your bench top. My bench top is 37mm thick, so I went for a space of 42mm.
The next step is to drill the holes for the clamping screw in the bottom part, as well as the hole in the upright part to accommodate the adjustment bolt, 40mm up from the middle part. The size in both cases was 8mm: The bottom part was fitted with a T-nut which required an 8 mm hole, and the hole for the 6mm adjustment bolt was also 8mm as the bolt has to fit loosely in order to accommodate the changing angle of the adjustment arms.
Step 4: Building Continued: the Hardwood Bits
I made the adjustment arms, the jaws, and the fitting holding the nut for the adjustment bolt from hardwood, as they are all load bearing parts.
The swivelling jaw and the fixture for the adjustment nut are both the same size: 15mm x 12mm x 40mm long. Both are fixed between the adjustment arms with 3mm x 25mm wood screws (first picture), and the same screw size is also used to fix the arms' bottom ends to the main frame. I drilled 3,5mm holes at the appropriate places in the arms, and 3mm holes in the centre of both sides of the swivelling jaw and the nut fixture (second picture). The bigger holes for the shafts of the screws are to allow for movement of the different parts as the jaws are opened and closed.
Some kind of nut has to be fitted to the adjustment nut fixture (third picture). I glued a regular nut into a hole in the fixture, but a T-nut or threaded insert can also be used (fourth picture). To fit the nut, I drilled a 12mm hole in the top half of the fixture into which the nut was glued, with a 8 mm hole from the bottom to accommodate the bolt, but preventing the nut from being pulled through the hole when a load is applied (last two pictures).
Step 5: Screwing It All Together
The fixed jaw can just be glued to the top part of the main frame (first picture).
Then the swivelling jaw can be screwed to the arms, but note the offset of the holes in the arms (second picture). This lets the jaw's face protrude a few millimeters beyond the arms, and also provides a bigger load bearing area on the arms.
Next are the holes to fit the bottom ends of the adjustment arms to the main frame. To ensure that the jaws will align correctly, I suggest clamping the jaws together (third picture), while drilling the holes. Lastly the holes for the adjustment nut fixture can be drilled in line with the hole drilled earlier in the main frame for the adjustment bolt.
The last picture shows the holes drilled in the arms, and the screws ready to be fitted. They must fit reasonably tight, but must still allow movement of the different parts (the jaw swivels, as does the fixture for the adjustment nut, and of course the arms itself turns on their fixing screws at the bottom as the jaws is opened/closed).
Step 6: The Adjustment Screws
The vise has two adjustment screws: One at the bottom for fixing the vise to the bench top, and one on the back to open and close the jaws with.
For the bottom adjustment screw I used something called an "adjustable leg" (first photo). I think it is used on the bottom of table legs to adjust the height of the leg, but I have found it very useful as a adjustment knob for other purposes. The ones I bought have a threaded part 6mm x 30mm long, which works nicely with the 18mm pine shelving I use for many of my projects. To accommodate the screw, I used a T-nut, treated with a dollop of contact glue before pressing it into place. I first drilled an 8mm hole for the stem of the T-nut, and countersunk the top of the nut with a 19mm spade drill bit (second picture).
The most important adjustment screw is of course the bolt opening and closing the jaws of the vice. A 6mm bolt, 75mm long, worked perfectly. The knob I fashioned out of a plastic Coke bottle top. First I drilled a 6mm hole through the middle of the cap, through which I pushed the bolt, fitted with washers on both sides of the cap. A locknut holds everything in place (third and fourth pictures). My version of a locknut is to just damage the threads of the bolt with a punch to keep an ordinary nut firmly in place.
The bolt then fits through a washer (last picture) and the opening in the back of the main frame, and is screwed into the nut fixture between the adjustment arms.
Step 7: Finished!
And there you are: Your home made vice ready for (not so heavy) use!