Scrubber Part 2

figure 2

Cutting The Spacers :

If you have purchased the nylon or acrylic as one large block then you will need to cut the spacers from this larger block of material. Using a pencil or texture, mark the larger block of acrylic or nylon into 40 x 40mm squares. As described previously, mark across the diagonals of each small square and centre punch the centre the cross only of each of the small squares. see figure 3.

figure 3. (4 @ 40mm x 40mm )

Now fit the 40mm holesaw (with 6mm drill bit) into the drilling machine. Important, be sure that the drill bit in the centre of the holesaw is 5.5 or 6mm diameter, as the centre of the spacer/collars are fixed at this 5.5 - 6mm diameter. Align the holesaw drill bit to the centre punch mark of each square. Drill through the acrylic/nylon until you have gone right through with the holesaw. You have now created your first plate spacer. Carefully remove the cut spacer from the holesaw cutting blade and continue on cutting the rest. The dimension of each spacer should equal ~38mm x 9-10 mm (x 6 mm hole in the centre). Repeat the process until all 4 spacers have been drill with the holesaw. Alternatively, you may also purchase a round rod of 40mm diameter nylon/acrylic and cut the above spacers to 9-10mm thick... Note : drilling the centre hole of this round rod type material is much harder when trying to locate the drill bit in the absolute centre.

figure 4. (3 of the 4 spaces. )

Lathing the collar on the spacer:

Once you have all the spacers cut out you will need to modify only 3 of these spacers to hold the 3 middle plates in the centre. The 4th spacer does not require a collar. These 3 collars prevent the plates from making contact and shorting out with the 75mm x 6mm main fixing bolt of the unit. A 12.5mm x 0.75 -1mm collar will be lathed onto the face of each of these 3 spacers. See figure 4 above for the collar dimensions.

Making the miniature lathe for the job:
Obtain a 6mm dia x 50 mm long bolt with 2 nuts. Cut the head of the bolt off as close to the head as possible. Now place the bolt in a hand drilling machine with the cut off end foremost in the chuck. Tighten the bolt into the drill chuck securely. Place the first nut on the bolt about half way down the threaded shaft of the bolt in the chuck. Now place one of the 3 nylon/acrylic spacers on the bolt and secure with the second nut. Tighten the nuts firmly, but not overly tight, with a spanner. Secure the hand drilling machine in a wood vice or similar clamping utility and fix the machine firmly. Turn the drilling machine on and fix the power button with a rubber band to stay on for the duration of each job. With a block of wood clamped securely to the bench top as a cantilever, carve away the nylon/acrylic spacer face with a sharp chisel or sharp screw driver. You may like to remove a small checkout or mortice the width of the chisel from the block of wood cantilever. This will allow you to maintain firm control over the tool while lathing these collars. (see figure 5.) Start at the edge of the nylon or acrylic spacer and work your way into the centre. You must leave the centre section with a 12.5 mm x 0.75 -1 mm deep collar . This collar is the main object of importance that you are trying to accomplish with this exercise. This is the collar that holds the plates centre most on the scrubber unit.(refer to figure 4.) With out this collar the plates can fall away and short out on the main centre fixing rod of the assembled unit, which may burn out your battery charger or power supply. You should not make the depth of this collar any more than the thickness of your stainless steel plates, as the plates will not tighten up, which will leave the plates flimsy and prone to cause problems.

figure 5. (Drill machine used as a mini lathe.)

Centre Spacer Modification:

Ok, once you have all the spacer collars lathed out you will need to modify one more of these spacers to hold the centre electrode in the centre position on the middle plate of the unit. This centre spacer must be one of the spacers with the lathed out collar as done above. Turn the previously lathed spaced over and put it back on the mini lathe then tighten the locking nuts. Now, starting at the outer rim of the spacer come in 7mm and lathe a groove 2mm deep by 3-5mm wide. This groove is where the centre electrode gets looped around and presses against the centre plate. Do not make this groove too deep, else the 2.5mm dia electrode will not contact the middle plate with firm pressure when the overall main fixing bolt is tightened. This groove prevents the centre electrode from falling away or making contact with the 75mm main fixing bolt of the assembled unit. The centre spacer is the only spacer to get this extract groove. You will also need to use a small round file to file an extra vertical slot coming from the newly lathed groove to the outer rim of this centre spacer. This is were the centre electrode shaft comes through the side of the centre spacer. This vertical slot will be 7mm long by 2.5 mm wide/deep into the spacer material. The vertical slot depth is not critical, as this slot can be deeper than the 2mm previous groove. See figure 6 for the centre spacer dimensions.