Grip-a-disc

Len Piers who was a Fellow of the Worshipful Company, developed this sanding system a long time ago basically because he needed it and the systems then on the market were no good. There have been attempts to copy it but so far none have been fully successful.

Len’s breakthrough was to place a layer of polyurethane foam under the abrasive where it protects the nylon hooks from the heat of over-enthusiastic sanding. Everybody else made the abrasive disc as cheap as possible with no foam so that in use new holder heads were required very frequently from melting the hooks, wiping out any possible savings on discs.

The other advantage Len’s design had over the opposition was the use of Vitex abrasive, the good stuff that is, with stearate lubrication. Vitex gives cooler running and much longer life, more than offsetting the extra cost of the quality abrasive.

Len died a few years ago and the family carried on but soon hit a major snag. All the laminator companies one by one refused to handle the product because the grit ruined the machinery for their other work. I got involved when Len’s son Donald asked me to help him find some more laminators as he had no access to the internet and he had exhausted all the other avenues.

After many evenings searching I had only found the firms already aware of our product and its problems so I tried a fresh approach. None of the firms the Piers family had used would give up the technical details of their processes so I researched the available glue systems Eventually some convincing laminates were produced so then I made a simple punch to cut discs. The only ones that worked used glues that were extremely expensive however so we had to do our sums very carefully.

By now I had made and destroyed literally hundreds of samples of film glues but the chemistry was becoming clear. We now knew the common denominators of the nearly successful ones and so could concentrate the search. Eventually I identified both glue film chemistry and source  and the research shifted to machinery. I measured the pressures being used to make one successful laminate and scaled it up to the size needed to be efficient as a production run. It was a monster mangle basically, known to the plywood manufacturing industry as a glue spreader. Via the internet again I found an old well used one and Donald went and bought it. It soon made good laminate by the square metre but wouldn’t take the multiple disc cutters. Back in my workshop I put a long lever on my hand press and by multiplying my weight by the length of the lever got a shock, we were way up in the tons for quite a small number of ganged cutters.

I then used my account with Draper to get a 20 ton hydraulic press and adapted it with massive slabs of steel plate to back up the multi-cutter boards and production started, doing up to 50 discs at a time. Very soon Donald was in trouble however, pumping the hydraulic ram by hand was destroying his darts arm. I found a local hydraulic components supplier and with their engineer worked out from the dimensions of our hydraulic ram the requirements on an air driven hydraulic pump then from there calculated the size of air compressor needed. Draper again. Production then got properly under way with a fully powered cutting rig. Then of course more snags, we had been driving the cutters down onto wood but we were destroying as much wood as we were making area of discs, we tried self healing cutting mats and the same thing happened, we found a solution but of course that too is now a trade secret.

With just minor snags since then, production has continued. The foam we were using became unavailable and the glue refused to function properly during the winter. With machinery this size the workshop is the wood store barn, virtually impossible to heat.

After all the trials and tribulations we now realise that somewhere along the way we caught up with Len’s original work and surpassed it. The expense of the higher quality glue has paid off handsomely. The durability of the current product is significantly better than the old. So now we too will keep our technical details to ourselves.

Our pads outlast the old significantly and they can be abused a lot without delaminating, I use them a lot and as I am working mine for a living I am working against the clock always. They go in the bin completely worn out now. My holders however do not get melted now and last years.

One bit of advice however, no not press too hard, if you squash the foam flat you defeat the purpose of putting it there, it in no way needs that much pressure and if you persist the heat will damage the holder and spoil the job at the same time. Let the machinery do the work.