Ya learn something everyday

[Geoff Beale]

- Make??

[Andy Hall]

No they are not.

It is an indirect by-product of the EU Machinery Directive.

There are specific standards for circular saw benches which require that the blade comes to a halt within 10 seconds of pressing the stop button.

Many products sold or imported for sale in the EU have to carry the CE mark as an indication that they meet the relevant standards for the product. For most electrical appliances, this involves self certification by the manufacturer, normally backed up with test lab reports, but not mandatory. In other words, I can choose to sell hairdryers, put a CE label on them and hope that they conform to relevant standards. However, if there is a problem and I don't have the lab report backup, then I am somewhat exposed.

For certain classes of machinery, saw benches included, there is a specific legal requirement to go to an independent test lab and have tests and reports produced.

The problem with a lot of saw benches of small size and relatively simple controls is that when fitted with a dado blade set, the rotating mass becomes such that the saw can't be brought to a halt in less than

10 seconds.

Because of this, not wanting to change designs and product liability, a lot of manufacturers opted to solve the issue by having models of their saws for sale in Europe with arbors too short to take a dado set.

Others solved it by not bothering to sell in Europe - for example many of the U.S. brands are not available on the market here.

However, there are at least two scenarios where it is perfectly possible and legal to have a saw capable of taking dado tooling in Europe. I've used both.

a) I can import a saw personally, for my own use. This is provided that I don't use it for industrial purposes (i.e. where health and safety legislation would apply), and that I don't sell it (because this is considered to be "placing it on the market" and CE requirements would apply.

So I have a portable table saw with long 5/8" arbor, quite capable of taking dado sets. Curiously, the tooling is available in Europe - Freud makes it in Italy, for example.

It certainly doesn't meet the 10 second stopping rule.

Equally, I could have purchased a second hand saw, so longer in use in an industrial environment, able to take dado sets, for my own use.

b) Table saws can be designed with appropriate controls and tooling in order to meet the 10 second stopping requirement. For example, my combination machine has electronic braking through its VFD controller. It will stop a normal 315mm saw blade in about 3 seconds after pressing the stop button.

For dado cutting, there is a set of tooling specifically for it which resembles spindle moulder tooling - basically two overlapping steel components with replaceable cutters which can be shimmed to provide the width of cut required. The saw arbor is designed to take them and even with this mass of metal (more than a typical dado set), the machine will come to a halt in around 5 seconds.

None of this is to suggest that dado cutting in any form with a saw bench is the safest of activities. I always take a lot of care with my machinery, but with dado cutting even more so. One obvious factor is that the blade has to be unguarded (at least in terms of a conventional guard fitted to the riving knife. This can be got around by having a cantilevered guard mounted from above. I don't have one of those, but do use a power feeder when I can so that hands are nowhere near the business area.

[Guy King]

The message from Andy Hall contains these words:

Neither does my Rexon.

As I understood it the difficulty was not stopping the mass in time, but that deccelerating that much mass that fast lead to the blade-nut unscrewing itself.

How long does the arbor need to be to take a dado set? I've longed for one for ages.

[dingbat]

Mines an old Wadkin, converted to single phase and without braking. It stops quickly enough with my lightweight Freud dado sets on it, but I imagine that a heavier dado set would be slow enough to breach the PUWER rules.

I've also used a modern Czech machine (the green and white ones - forgotten the name) that was supplied with a long arbor and clever enough electrical braking that they slowed down in time, but not so quickly that you couldn't still use a simple LH nut to lock the blade.

[Andy Hall]

The nut should not undo. If there were a tendency to that, it should be a left hand one anyway.

Probably a good 30mm. the dado packs are normally 20 or 22mm.

[Andy Hall]

[Guy King]

The message from Andy Hall contains these words:

My Rexon rotates anti-clockwise as you look at the nut. If the shaft stopped suddenly the momentum of the blade could undo the nut, which is a normal right-hand thread.

[Roger]

The message from Andy Hall contains these words:

Which would leave the blade able to unscrew the nut under load which is surely worse. You can't have it both ways unless the blade has a keyway or some other means of prevented unwanted rotation in which case the handedness of the nut becomes irrelevant.