Everything you ever wanted to know about Dado Heads.
The major points to note are:
- The HSE state it is perfectly acceptable to use saws fitted with a dado blade if the saw table is designed to accept it.
- The current BSI guidelines allow for saw tables to be manufactured for sale in the UK today with a dado up to 15.5mm, possibly wider see below.
- Riving knives can be removed during grooving operations as long as the blade is guarded. A safety guard doesn't have to be attached to a riving knife.
For more details on this issue please read on....
One of the things we get asked most about is the use of Dado Head cutters in the UK. The table saw David uses in the show is his personal equipment, he's had it for years and in fact imported it from Australia where extended arbors are available.
It was strange when we started talking to people in the UK woodworking industry and finding out that they were just as surprised as we were that saw tables couldn't take these wide blades because they always used to be able to. It is a fairly recent change to the UK safety recommendations. There are actually a lot of English saws around that will accept a Dado blade but they are older saws. None of the ones on the market currently will take these blades and it is a mistake to try and make one fit. So if you want this ability you have to either buy an old saw second hand here in the UK or buy one from an overseas supplier and import it yourself, a lot of countries in Europe have saws capable of using this type of blade as does, US, Canada, Australia, New Zealand but there is good news afoot. Read on!
A saw has to be designed to accept this type of tooling and still function within the manufacturer’s specs. It isn't just a matter of bolting on an extra long arbor or spindle and then get to work cutting dados. There are many safety related reasons why this should not be attempted.
The other misunderstanding is that people think it is illegal to use a saw with this facility. This is totally false. It is not an issue of legality or safety. We spoke to the Health and Safety Executive and to the BSI and here's the reality of this issue.
The Health and Safety Exec. are an advisory board making recommendations on the safe operation of woodworking machinery. They are interested to see that businesses ensure their staff operate equipment safely and within the recommended guidelines. If a company does not fulfil their duty of care and an accident happens, a company can be held responsible and prosecuted and they frequently are. The Table Saw in particular is one of the most dangerous tools in any woodworking shop.
This is not the same as you working in your on home workshop. Safety is your responsibility and if you have an accident it's your fault. This is why on all the TV shows involving the use of machinery a safety announcement is made to remind people of the importance of understanding the proper use of equipment and to make sure you follow the safety guidelines as there is no one there to supervise you.
The safety guards are sometimes removed on the show to allow the camera to show you what operation is being performed more clearly, this is not a recommendation for the audience to do the same, you should always treat your tools with the greatest of respect. Power tools can be dangerous and they don't mind what they cut, they leave that up to you, so work safely at all times and take your time, DON’T RUSH a job.
The next piece of information is hardly known at all even to manufacturers it seems.
The specification for saw tables as issued by the British Standards Institute, (this is the body that issues the CE certification to tool manufacturers), states that the maximum width of cutting blade (currently acceptable to the BSI) must not exceed 15.5mm, that’s over a half an inch in width, and this is what is currently allowable, but none of the manufacturers we have seen are taking advantage of this, we are not sure why. That's a pretty wide dado and would certainly make life easier for all the British woodworkers that long to perform this type of operation.
There are a couple of other issues that must be accommodated for example, the blade must come to a standstill within 10 seconds of the machine being stopped, a restriction on the saw blade diameter, they must make sure the saw blade can not come loose during start up, running, run down or braking and recommendations are made in the BSI document on how this can be achieved and flanged bushes need to be provided where the spindle diameter is different from the bore size of the saw blade. All these things considered there certainly seems room for manufactures to take advantage of grooving operations for UK saws. The other point to make is that manufacturers do not have to follow the guidelines outlined in the BSI document. These are purely guidelines, any manufacture can submit a design to the BSI and they will check it and test it to ensure it meets their requirements and if it does it will be passed even if it’s not exactly the way the guidelines are currently written. This allows the manufacturer room to be inventive in how they design their equipment.
If you want to use a dado blade in a saw capable of accepting it then the blade should be effectively guarded but there are many options available to achieve this. The Health and Safety Exec. publish a document explaining how to effectively guard a dado head blade. It is called “Woodworking Sheet No 16 (rev) and it discusses the Safe working practices for Circular saw benches. It certainly seems possible that such saw tables should be available on the market in the future.
We have also learnt that a submission has been made by a member state ( i.e. a member of the council that votes on, and agrees to changes to manufacturing guidelines that countries have to abide by. Each country in Europe has a representative on this council) to increase the width from 15.5mm to a greater width. This would possibly bring the blade width to 3/4" as is available in the US, perfect for all that grooving work. This submission is currently under review and there should be an answer on this in 2004.
Check out the HSE website by clicking on the link to the left to view their safety booklets and other information. The BSI will issue a copy of the standard relating to this issue which is "BS EN 1870-1, 1999 Safety of woodworking machines - Circular sawing machines, Part 1: Circular saw benches (with and without sliding table) and dimension saws" but this is not free.
The first manufacturer to release a saw table that can take the wider blade will certainly be popular. Let’s keep our fingers crossed.