The Big Project

Clean large metal parts like a pro for under £300

Theo shows you how to make your own wet abrasive blaster at home for a fraction of the cost of an off-the-shelf unit.

1 Cut out material for cabinet

Professional wet-grit-blaster cabinets are usually made from stainless-steel, folded and/or welded to create a corrosion resistant structure. We’re making our cabinet from plywood, and waterproofing it with

3 Make hopper

Cut two triangles the width of the cabinet top, minus two board thickness, for the front and back of the hopper. Use a flap-disc/plane to bevel the edges.

Cut two more pieces, clamp, glue, screw and sand.

6 Door

We’re making a space-efficient clamshell-type cabinet, with the whole front panel, including gloves, hinging from the top panel. We’ve cut out a 5mm gap for a seal at the top and sides. glass-reinforced-plastic (GRP). Any sheet material/ board could be used. This will stand on steel legs. The sheets are 2440 x 1220mm, so we’ve opted to make the blaster 1220mm wide and 610mm deep.

4 Remedial strengthening

To take the weight of heavy components, the mesh floor will eventually sit on a steel frame that’s bolted through the cabinet to this girdle made from 75 x 50 x 6mm unequal angle, which also imparts rigidity.

7 Ergonomics

Mock up the blaster’s finished height so that it’s comfortable: you need to be able to see through the viewing aperture and the gloves should be at elbow height. Adjust until correct then mark the arm holes.

2 Assemble cabinet top

Using the back as a starting point, drill pilot holes, apply some wood glue and screw the two sides into position. Countersink or bury the screw heads.

Fix the front glove-, viewing- and top-panels, too.

5 Cut glass aperture

You will need to order either some toughened or laminated safety glass for the window. Mark out and cut an aperture about 20mm smaller than the glass all round, sanding/bevelling the inside edges.

8 Hopper treatment

If your blaster will be dry, the hopper should terminate in a boss for a pick-up pipe; if it’s wet like ours, you need to think about drain types. We’ve used a 100mm gully pot here.

9 Prepare to waterproof

Use a cheap polyester body filler to squeeze into the joints in the cabinet, creating gentle radii for the GRP. Fit the drain and blend it into the hopper with filler. Sand with P40-80 paper for a smooth profile.

12 Prepare door

Use the gauntlets’ mounting rings as a template to cut the arm holes. Screw a drip bar to the base of the door. Apply filler, sand, straighten any wavy edges, prime, lay-up GRP, then finish with some flowcoat.

15 Fabricate stand 10 Start waterproofing

Source general lay-up resin, catalyst, strips of chopped strand matting, brushes and a paddle roller. Clean the surface, mix up the resin, brush it into the wood, and use the matting to reinforce joints.

13 Hinge and glass prep

Mark out the door for hinges. Drill holes, countersink, and epoxy countersunk screws in place. Screw four strips of batten the thickness of the glass, and cut out a retainer. Drill and countersink the glove rings.

Remove the unequal-angle iron girdle tacked-up earlier and continuously weld it. Make a similar girdle (50 x 50 x 6mm) for the base, and cut four legs from the same steel, either short or long depending on whether it will be bench-top or free-standing. Cut and drill four plates for castors. Tack weld together, check its alignment, and continuously weld to finish. We’ve also made up some steel enclosures for the fittings.

11 Finish waterproofing

Cut some matting to the shape of the hopper. Lay up the matting with standard resin. Finish with tissue, if required. Finally, paint on a white flowcoat to add a bright, smooth finish to aid draining.

14 Fit door seals

UPVC strip (60mm x 5mm) will provide a labyrinthtype seal for the top and sides. Stand it off with 30mm x 1mm aluminium strip. With the edges sealed, apply the 13mm x 8mm self-adhesive seal.

16 Paint external surfaces

With the interior waterproofed, it’s also worth finishing off the exterior. Trim off any overlaps, squeeze filler into the joints and sand all over. Prime with a thinned oil-based paint, then overcoat.

17 Slurry pump

A submersible-pump (£40) fits into a plasterer’s bucket (£6) on a simple trivet with BSP fittings to culminate in a suitable hose-tail. The valve is for fine-tuning the delivery to the blast nozzle.

22 Setting up

This will take a bit of trial and error as there’s adjustable slurry flow, using the valve in the bucket; the ratio of medium to water; the blast-nozzle’s adjustment; and air pressure to consider.

18 Compressed air

Route the slurry and air hoses into the cabinet, via bulkhead fittings if possible. Affix a regulator to the frame and place a foot valve in line with the nozzle for control. A one-way valve will prevent back-flow.

20 Lighting

Adequate lighting is essential. You must use waterproof fittings and fit the glands correctly to exclude moisture. Consider using LED lights, or 12-volt lights and a transformer for safety.

23 How to use it

Remove the worst of the grot and grime before blasting. It won’t remove vitreous or rubbery coatings, though. Turn on the slurry first, then add air. Blast methodically.

19 Electrics

You could leave the pump’s plug in-situ and turn it on/off as required, but it’s more convenient to use a splashproof enclosure, glands, and wire in a footoperated switch. Ensure the frame is earthed.

21 Final assembly

Fit the door then fit a stainless mesh in the hopper to act as a work-surface. Fabricate stays for the door, or use gas struts to elevate the lid, latching with over-centre catches. Finally, tidy all wiring/plumbing.

24 Pimp your blaster

Fancy some upgrades? The mist can be largely controlled by a 12-volt bilge fan or

Ip-rated bathroom extractor. Fitting a windscreen wiper to the glass will also help.