Popular Mechanics (South Africa)
BAR CLAMPS
These all-wood clamps are really easy to construct, so find some well-seasoned straight-grained and knot-free pieces for the bars. The headstocks, tailstocks and wedges can be made from any appropriately sized strong timber.
We have chosen to make two sets of clamps, one set at 600 mm functional length and the other set at 1 000 mm.
LOCKING MECHANISM
As with the panel marking gauge in the previous issue, the clamps work on the time-tested principle of wedging. The headstocks are permanently attached to the bars and the pivoting tailstocks have thick dowels that fit into the holes drilled along the length of the bars.
The double-wedge method is perfect for applying the correct amount of clamping pressure to the glue-up, and the clamp remains perfectly aligned. Simple, easy and repeatable!
MATERIALS
» Headstocks and tailstocks: Laminated from three pieces of 25 mm stock.
» Dowels: Turned on a lathe; but 16 mm diameter hardwood dowels can be store-bought. » Bars for clamps: Straightgrained stock from goodquality softwood.
STOCK DIMENSIONS
» Headstock: 156 mm long × 64 mm wide × 60 mm thick » Tailstock: 156 mm long ×
64 mm wide × 60 mm thick » Long clamp bar: 1 200 mm long × 40 mm wide × 30 mm thick; short clamp bar: 800 mm long × 40 mm wide × 30 mm thick » Dowel: 16 mm straightgrained hardwood
TOOL LIST
We recommend building the clamps using hand tools. Not only will you gain excellent tool skills and fine-tune your handwork abilities in the process, but you’ll have the pure satisfaction of using the clamps for years to come, knowing that you built them entirely by hand.
» Marking/cutting gauge » Marking knife
» Tape measure
» Steel ruler, 1 000 mm » Mechanical pencil, 0.5 mm » Japanese dozuki or Western
tenon saw
» Bow saw
» Mallet
» Jointer plane
» Jack and router planes » Smoothing plane » Low-angle block plane » Bevel-edge bench chisels » French curve
» Try square
» Combination gauge
» Set of dividers
» Cabinet scrapers
» 16 mm Forstner bit
PROCESS
STEP 1: Select the stock for your project and proceed to cut it all to rough size. Glue up your required laminations and set aside to cure. Plane and cut all the stock to exact dimensions, making sure all of your work pieces are absolutely square and true.
STEP 2: On the four headstocks, mark out the middle of the stocks. Working from these centre lines, lay out the housing cutouts 30 mm deep × 40 mm wide for the beams to fit into, using a sharp marking knife. We suggest using 3M blue painter’s tape so it’s easier to see the markings when cutting out the housings.
STEP 3: Repeat the process on all of the tailstocks – the only difference is that you should make the housing recesses 5 mm wider on either side, so the total width of a tailstock housing is 50 mm. This ‘play’ will allow the tailstock to pivot on its dowel, ensuring the accompanying wedges do their jobs effectively.
STEP 4: The concave recesses on the outer sides of the stocks are not structurally necessary, however they will make the clamps easier to handle and in our opinion give the clamps a neat and well-finished look. For executing the concave recesses, we simply worked off a small section of a French curve, but if you prefer, you can make a template for the profile. This makes sense if you intend making more of these clamps in the future, as you’ll then already have the exact template made up.
The quickest way to shape the profiles is with a narrow blade fitted to a bandsaw, and then to use a dedicated spindle sander or drumsanding attachment fitted to a drill press. We went old school, using relief cuts with a tenon saw, final cuts with a bow saw fitted with a narrow blade, and final shaping with chisels, rasps, files and a little sandpaper.
STEP 5: Mark out and drill the two dowel holes in the headstocks according to the CAD drawing. They are centred at 24 mm and 50 mm from the face of the stock respectively. For the tailstocks, repeat the procedure with a single centred dowel hole 40 mm from the face of the stock.
STEP 6:
Lay out and drill the dowel holes in the beams. Find the absolute centre line on the face of the beams (the 40 mm wide face). Draw a crisp pencil line down the full length of all the beams. Next, position each headstock on its corresponding beam and tap it backwards until the rear of the headstock is 40 mm from the end of the beam.
Using the holes that are already in the headstock and making sure the face of the headstock is at 90° to the beam, clamp the headstock and beam together and drill headstock mounting holes in the beam.
We suggest that all of your dowel holes, including those in the headstock and tailstock, are drilled on a drill press, using a 16 mm Forstner bit for precise and accurate results.
Using a pair of dividers, mark out and continue to drill holes 50 mm apart, centred down the length of the beam.
STEP 7:
Cut all of the dowels a bit longer than the required length of 58 mm. Now is the right time to sand all the parts prior to glue-up.
STEP 8:
Glue the headstocks to the beams and glue in the two dowels. Make sure the headstocks are at 90° in both axes to the beams and clamp them, setting them aside to cure. Glue the single dowels into the tailstocks only, making sure you have no squeezeout within the housings.
STEP 9: While these parts are curing, make up the wedges according to the CAD drawing. They should be longer than the width of the tailstock, allowing them to be tapped in and out of position without your mallet hitting the stock itself. You can attach the wedges to the tailstock with lengths of thin parachute cord. We opted against this, as we keep a good supply of wedges in a small box at the clamp rack instead.
STEP 10: Apply your preferred finish to the project. We chose OSMO 3032 Polyx-Oil after sanding to 150 grit. A couple of liberal coats of paste wax will prevent any adhesive from sticking to your clamps and they will be ready for years of use.
STARTED BY Seamus and Brendan’s dad Rory Harcourt-Wood back in 1982, and based in Epping Industria in Cape Town, with a branch in Knysna, Rare Woods has the largest and most diverse selection of timber available on the African continent. There is more than 8 000 m³ of timber available, made up of more than 130 domestic and exotic species.
Whether you need large slabs, turning blanks, lutherie parts or anything in-between, you can order your timber online and it’ll be delivered by courier to your workshop door – it couldn’t be simpler.
If you’re looking for some really special woods for your latest project, log on to rarewoods.co.za or ring the Cape Town office on 021 535 2004, or the Knysna team on 044 382 6575. Sign up to the Rare Woods newsletter and receive a R100 discount off your first order of R1 000 or more. All online purchases to the value of R1 000 or more qualify for free delivery throughout South Africa.