Circular saw safety

[Stu_2]

Where possible, I never stand directly behind any circular saw. Tend to use the TS55 for most stuff now.

The anti-kickback blocks that attaches to the track are really useful in stopping the saw moving backwards a bit when plunging, which is especially useful when plunging into worktops etc.

Looks like there are some great deals on the TS55 knocking about now.

 

[markturner]

I have been using the Festool plunge saws since they first came out, many times plunge cutting worktops ( kitchen fitting my main occupation before I got stuck behind this desk... )

You have to be careful and sensible, I see so many of my guys using these saws unsafely, their rails with scars across them and chunks cut out of them, usually caused by not supporting the workpiece properly and going at it like a bull in a china shop. I have never had a problem, you have to listen to what the saw is telling you. Festool also sell a little plastic attachment to the rail, that clamps over the end of the saw to prevent kickback.

Spend the extra money and get the Festool....you wont regret it.

 

[Hugo_Wolfwhistle]

Must be a new 'feature' on the Bosch saws then (and yes, that is a Bosch approved pencil)]

I think it must just be the big Bosch that seems to still have the riving knife. Just out of interest, how well do you find the dust collection works on that saw? Is it pretty easy to handle given the size/weight/power? I had assumed it would be a bit bigger than what I would need, but would be interested to hear what you reckon.

Looks like there are some great deals on the TS55 knocking about now.

Spend the extra money and get the Festool....you wont regret it.

You guys have pretty much convinced me to spend the cash and get the TS55, it does look a fantastic bit of kit. Only thing is I am worried about depth of cut with it. I am confused as to whether it would be able to cut through 2 inch rough sawn timber given that it states it has 50mm depth of cut on the rail, and 2 inches is a touch more than that (50.8mm I think). Does anyone know if in reality it can cut 2 inch timber on the track?

What confuses me is that as I understand it, the makita and festool rails are pretty much identical, however Makita tech support told me the SP6000 has 56mm depth of cut off the rail, and they reckon it only looses 2mm when used on the rail, so how come the festool goes from 55mm off the rail to 50mm on the same rails? Or have Makita given me mis-information?
Haven't ruled out the Metabo on festool/makita rails. It is still tempting me too because then I would only need 1 tool for both rail use and more general work (plus the extra depth if I need it later) only problem is it doesn't maintain the cut line when beveling on the track unfortunately, so would either have to bevel off the track, or remove the splinter strip when bevelling, or maybe just tilt the whole track and clamp.

If the TS55 doesn't have enough depth of cut to do 2 inches, then I guess my only other options would be to either look at the Dewalt track saw (claims 59mm off the rail, 55mm on, but had heard reviews saying there were quality issues with it, not sure if they are true though).
Possibly I could see if it would be possible to add a kind of retrofitted wedge/fin type thing to the back of the SP6000 to act as a sort of riving knife and make sure the kerf cant close up.

I reckon if I did get the TS55 (or dewalt or sp6000) then I would also need to pick up a 2nd hand standard saw (with riving knife!) like the Makita 5703/4 or Hitachi for rougher off the rails work too.

One thing is for certain though, I am now convinced I definitely want a riving knife, no matter which saw I choose.

 

[Mar_mite]

I've had my dewalt track saw for about 2 1/2 years. In that time it's been used virtually every day, been dropped off the bench a dozen times, had paint spilled on it. And been left out in the rain. It hasn't missed a beat. I'd buy another in tomorrow if it packed in. I've used it side by side with the festool and while the festool feels a bit slicker, I've never felt the dewalt to be a poor mans equivalent.

 

[petermillard]

You guys have pretty much convinced me to spend the cash and get the TS55, it does look a fantastic bit of kit.

Don't know of anyone who's bought one and regretted it.

Only thing is I am worried about depth of cut with it. I am confused as to whether it would be able to cut through 2 inch rough sawn timber given that it states it has 50mm depth of cut on the rail, and 2 inches is a touch more than that (50.8mm I think). Does anyone know if in reality it can cut 2 inch timber on the track?

Can't remember the last time I saw 'rough sawn timber' in my local yard - it's all 'regularised' now, and tbh was only ever nominally 2" timber, but yes, I have used my TS55 to cut 8x2" without any issues - but that's 8x2 from my timber yard...

Haven't ruled out the Metabo on festool/makita rails. It is still tempting me too because then I would only need 1 tool for both rail use and more general work (plus the extra depth if I need it later) only problem is it doesn't maintain the cut line when beveling on the track unfortunately, so would either have to bevel off the track, or remove the splinter strip when bevelling, or maybe just tilt the whole track and clamp.

Second rail dedicated to bevel cuts would be the safe option.

I reckon if I did get the TS55 (or dewalt or sp6000) then I would also need to pick up a 2nd hand standard saw (with riving knife!) like the Makita 5703/4 or Hitachi for rougher off the rails work too.

Sounds like a plan, if you expect to do a significant amount of 'rougher off the rails work'. Let us know what you decide.

Cheers, Pete

 

[busy builder]

I've had a Festool TS55 for about 5 years now, use it almost daily. Mainly for cutting doors but also sheet materials. It is a cracking saw, I also have a Mafell KSP40, this is also a very good tool to have about but only cuts 40mm.

If I were to replace my TS55 it would be with the Mafell equivalent, the MT55, as Mafell are superior in many ways to Festool for site work. And they all have a riving knife that moves with the plunge. I've never once had any kickback either.

 

[dm65]

I think it must just be the big Bosch that seems to still have the riving knife. Just out of interest, how well do you find the dust collection works on that saw? Is it pretty easy to handle given the size/weight/power? I had assumed it would be a bit bigger than what I would need, but would be interested to hear what you reckon.

The way I've used it up to now, it's not as bad as you may think given it's size, but I have only used it with guides (now have two 4ft rails but haven't used them yet) and never freehand nor plunging

It's only been used outside so haven't bothered with extraction and can't answer your question - sorry

Smooth as you like on startup though

And something this big is always too big until you need either it's power or cutting capacity imho

I only have this cos I got it for an absolute steal - I won't even torment you with the price :wink:

 

[chippy1970]

Another vote for ts55 here I've owned one since 2007 and now have the newer version. Try a company called nuts & bolts if not ffx and toolfest are good too.

Sent from my HTC One using Tapatalk

 

[shed9]

Another vote for the Festool, and N&B ( http://www.powertool-supplies.co.uk/ ) as they generally have very good pricing and their service is spot on every time. I tend to use N&B for core Festool items but sometimes get bits and pieces from FFX.

For me, the only downside to the Festool is that I didn't get it earlier. I used to scoff at Festool prices however since becoming a user I can say it is definitely worth the extra. Be warned, its a slippery slope when you start buying Festool - it can be addictive for some.

They have a 15 day try out option so if you don't think its for you then you can send it back for a full refund. If you keep it, you get a 3 year warranty against defect and theft (who else does this?), plus they will guarantee to stock spares for ten years for your model.

Also, not sure if it was mentioned up there but you may need to consider dust extraction depending on where you intend to do your cutting.

 

[Distinterior]

Ditto to what Shed9 said.

A good dust extractor makes a big difference, not having to clear up all the sawdust at the end of a working day is a real bonus. I have 2, one for work whilst out on a jobsite and the bigger CT26 for my workshop. Super efficient and quiet.

But, as Shed9 said, be warned!!!!.........it is a very slippery slope when you get used to using tools of this quality. I find now, that every time I need to replace one of my existing tools, the first thing I look for is the latest Festool catalogue.

 

[Hugo_Wolfwhistle]

I've had my dewalt track saw for about 2 1/2 years. In that time it's been used virtually every day, been dropped off the bench a dozen times, had paint spilled on it. And been left out in the rain. It hasn't missed a beat. I'd buy another in tomorrow if it packed in. I've used it side by side with the festool and while the festool feels a bit slicker, I've never felt the dewalt to be a poor mans equivalent.

Thats re-assuring to know. I had just seen a review from someone calling themselves lumberjackass that wasn't very complimentary about the quality, but the problem with a lot of online reviews is that they are often based on very short term impressions, so good to hear that your longer term experience has been good. I will now seriously consider the dewalt too since it appears to be about the only other plunge saw to have the riving knife (well except for some of those Mafell KSS ones that I can't afford anyway).
If I did go for the dewalt I think I would put it on festool rails though so that I can get compatibility with all the festool/makita accessories. Do you know if the Dewalt's adjusters for rail tolerance work on both the central (Dewalt) rail groove and it's other (festool) rail groove? Do you find the bevel setting accurate?

Can't remember the last time I saw 'rough sawn timber' in my local yard - it's all 'regularised' now, and tbh was only ever nominally 2" timber, but yes, I have used my TS55 to cut 8x2" without any issues - but that's 8x2 from my timber yard...

Thanks for confirming, if it can do that, then I think that is all I need in terms of cut depth, at least for now.

Try a company called nuts & bolts if not ffx and toolfest are good too

Yeah, someone already posted a link to them earlier and the prices do look great. The festool was out of my price range until I saw their prices. I have a couple of other things I need though, so might see if the FFX multi-buy discount makes them cheaper.

Wish I had a local dealer in the tyneside area who carried track saws though so I could have a good look at a couple before making my decision (would be happy to pay a little more just for that to be honest), but all the tool companies round here don't seem to carry them.

A good dust extractor makes a big difference

I did have a quick look round for a new shop vacuum, but can't justify spending too much on this. Would an old home vacuum do OK (it is a vax cylone type), as I have one spare? If not do you have any suggestions for a cheap one ( <£100 ). I find that they hardly ever mention what particle sizes they filter.
Will any shop vacuum fitted with a dust bag give adequate filtration?

In terms of my question about the lack of riving knives on newer saws, I have now heard back from a few manufacturers, and Makita have given me the contact of their technical director to ask him the question, so when I hear back from him, and also the HSE, I will post the summary of all the reasons they have given.

Cheers

 

[shed9]

Will any shop vacuum fitted with a dust bag give adequate filtration?

Depends on what your cutting and the type of dust. Also, its likely that most sheet goods will contain formaldehyde based glues. If your in an environment which could expose you to the dust, do as much research on the extraction of it as you have on the saw itself.

Just my opinion, but don't skimp on this aspect; being exposed to wood dust is serious business these days, it catches up on you.

 

[Hugo_Wolfwhistle]

Right,
I have had a few responses back from various manufacturers on the riving knife issue, so thought I would post them here and see what you all think.
Although all of the emails/phone conversations were slightly different, I asked all of the manufacturers the following questions;

1. Why do many new circular saws in their ranges lack a riving knife?
2. Do the saws without the riving knife have an alternative safety feature instead of the riving knife?
3. Are saws without the knife only for particular uses (e.g. crosscuts or sheet goods)?
4. If doing rip cuts in natural timber, is it safer to use a saw with or without a riving knife?

Bosch:
They no longer have riving knives on any of their current corded circular saws, with the exception of the GKS 85 G Professional. I initially emailed them for an answer, but they didn't reply, so I called them and spoke to a service/tech support guy who then also involved a few other people, their answers were as follows;

1. Don't know why not fitted any more, apart from to say that if they don't have it on their saws then it must not be a useful feature.
2. No alternative safety feature instead of knife
3. No, can be used for all cuts
4. They just said they think all of their saws are as safe as possible.

To be honest, I was pretty disappointed with their responses, they didn't seem to have any real reasons or explanations, just sales propaganda.


Evolution Tools;
This company makes 3 circular saws, 1 with riving knives, 2 without. I spoke to their tech support department on the phone. The main expert was on holiday, but his colleague was still very helpful. His answers were as follows;

1. Believes that the regulations for circular saws changed a few years ago (possibly 2008/9) , meaning that new saws don’t have to have a riving knife. He said that he thinks that their saw with a knife (the original Rage) was designed before the regulation changes, whereas their other 2 saws without the knife (Rage B and Rage 230) were designed after the change.
   When I asked why not still design them with a riving knife anyway, he pointed out that their saws are aimed at metal cutting where kerf closing is less of a problem, and therefore a riving knife wasn’t a priority. He said that their saws are based on existing/generic designs which are then modified to feature their proprietary high torque motor/gearbox and multi-material blade technology, so probably the generic designs they based their later saws on just didn’t have a riving knife.
   Interestingly the rep also thinks (but stresses he couldn't be sure) that the change in regulations was at least partly due to TCT blades becoming the norm. He points out that TCT blades have a thicker kerf with respect to the blade body thickness meaning that pinching is less likely than old HSS blades. Also he thinks that on a TCT blade, the teeth at the back of the blade remain quite efficient at cutting, and therefore with modern powerful saws can often cut themselves free if they do start to get pinched. The rep has promised to double check this with their main expert/engineer when he returns from holiday to see if he was correct.
2. The rep said that the new saws comply with the latest safety regulations for saws without riving knives, but that he was not sure of any particular additional safety devices on the saws without the riving knife.
3. The support rep said that whilst the saws could be used for any cuts, although they don’t recommend plunge cuts, and he points out that their saws are meant for doing multi material cutting.
4. The rep said that he is not sure of the answer to this, but personally he would choose to use a saw with a riving knife for long cuts in natural timber.

I have to say I was very impressed by the approach of the support rep when answering the questions. He was helpful, friendly and sounded genuinely interested. I have an Evolution SCMS and I am very happy with it, and combined with the experience of talking to their rep, I have to say I really like this company and hope they go far.


Hitachi:
Hitachi also put me straight through to a very knowledgeable chap who was helpful.

1. He pointed out that Hitachi offer both types of saw, and therefore leave it up to the buyer to decide. When I asked why not have the ability to fit a riving knife to all saws and then just leave it up to the operator to choose if they want to fit it or not, instead of having separate models, he didn't know why.
   He also mentioned the change in regulations a few years back which relaxed the requirement for the riving knife, and that he thinks the use of TCT blades (with the thicker kerf compared to blade body thickness) had something to do with the change in regulations.
2. He said that he didn't know of any additional safety features on the saws without riving knives though. Although he did say that all of their saws meet the relevant safety standards.
3. He said that their saws without the knife are designed more for plunge cutting, whilst the saws with a knife are designed more for ripping
4. When I then asked if that meant that the saws without the knife are less safe if doing ripping, he agreed that he thought this was the case.

Makita:
I contacted Makita 3 times, first was an email from before I started this thread asking some questions about the SP6000 as follows;

Good afternoon, I am very interested in the Maikta SP6000 plunge/track saw system, however before buying, I have a few questions about it that I was hoping you may be able to answer for me.
1) What is the max depth of cut for the saw when it is on the rails, I could not tell if the depth stated on your website was with or without the rails?
2) I noticed that the saw does not feature a riving knife (unlike some competitor’s saws), I was under the impression that for circular saws sold in the EU, a riving knife should be fitted unless there is some sort of active and/or passive mitigation designed into the saw to prevent kickbacks. I realize that your saw features a latch to prevent the saw tipping off the rail when doing bevel cuts, does this also prevent the saw jumping up and off the rail as well during a kickback? If this is not the case, then does the saw feature any other safety systems to protect against kick-back and mitigate the lack of a riving knife? As an example of what I mean, Mafell have stated that their mt55 saw has additional safety features to account for the lack of riving knife as discussed here; http://festoolownersgroup.com/other-too ... e/40/?wap2 )
3) Will an anti chip accessory be available for the offcut side like there is for the festool saws?
4) If the speed is reduced, and an appropriate blade is fitted, is it possible to use the SP6000 to cut mild steel?
5) is it safe and/or practical to use the SP6000 free hand off the track?

Makita replied with the following;

Good Morning, to answer your questions, the SP6000 is designed to be used with or without a guide rail, if used with it will take approx 2mm of the max depth of cut. The unit does not feature a riving knife, it is a plunge saw with fully encased guard, with high speed retraction, in reference to the kickback questions I will quote from the manual - 'Kickback is the result of saw misuse and/or incorrect operating procedures or conditions and can be avoided by taking proper precaution as given... '. There is no anti chip accessory available and we do not recommend or supply blades for circular saws to cut steel.

I then sent them some more emails asking for more information about why some of their saws lack the riving knife. Basically asking the same 4 questions I asked the other manufacturers. I initially received no response, but after chasing it up over the phone, I was given the contact information for their technical coordinator (Makita UK), a helpful and knowledgeable guy called Terry Wooding. I had a good phone conversation with him on 19th June, and this is the summary of his answers;

1. Newer Makita saws don't have riving knife due to changes to BS EN 60745-2-5 meaning that they are no longer mandatory. The saws which Makita produce with the riving knife are of older existing designs, whereas all of their new saw designs lack a riving knife.
   He believes that going forward all new Makita circular saw designs will not have the riving knife, although he is not ruling out the possibility of designing new model featuring a riving knife completely. He also believes that this is the way that the industry as a whole will go.
   He did however mention that Makita likes to keep existing models (albeit with some slight updates) on the market for a long time, maybe decades, and therefore Makita will continue to produce their existing models with riving knives for the foreseeable future.
2. In terms of the reasons for the change to the regulations and leaving the riving knife off new models, Terry said that the riving knife only protects against kickbacks due to kerf closing, and that he doesn't think that the riving knife actually did much even in this case on modern saws.
   He said that the new saws without the riving knives have more powerful motors which cut more quickly and don’t get slowed down as easily as on old saws (I got the impression he meant that they maintain the speed under load), and with the TCT teeth on modern saws the teeth are less likely to bind when pinched and more likely to cut themselves free.
   The 2nd factor he mentioned was that when the regulations changed, they placed a much greater emphasis on blade guard safety. In particular the regulations now require the guard to snap closed more quickly and reliably. Terry points out that a saw with a riving knife needs to have a slit in the blade guard or a 2 part guard to go around the knife (because the knife needs to be so close to the blade), therefore when designing their new saws Makita decided to leave off the riving knife so that they could use a much more solid blade guard in conjunction with a stronger, more reliable guard closing system. Makita’s reasoning for this is that a faster closing and more reliable guard can protect the user from danger in the event of any form of kickback or accident, whereas a riving knife can only reduce the chance of certain kickbacks happening. Further to this he said that if a saw has a riving knife and the riving knife and/or the blade guard becomes bent or misaligned then it can easily interfere with the blade guard which slows or in extreme cases prevents the guard closing. With the more robust guards featured on saws without the riving knife, the guard is less likely to be bent or damaged due to knocks and drops, and therefore is less likely to be slowed down or jammed.
3. No, can be used for all cuts
4. Terry said that both saws with and without the knife are safe for rip cuts

I also asked specifically about kickback on the SP6000. Terry said that the regulations for fast blade retraction also apply to plunge saws and that during a kickback, and that the kickback forces on plunge saws should push the blade up into the blade housing before it can leave the rail.


HSE:
I also contacted the HSE to see what they thought, and this was their reply;

There is a standard for this type of tool that hand held circular saw manufacturers should comply with.

This is BS EN 60745-2-5:2010 Hand-held motor-operated electric tools — Safety Part 2-5: Particular requirements for circular saws.

The standard includes requirements for saws that are designed to have a riving knife and those which are not i.e. both options are acceptable. It advises that :

Each one of these guarding system types can be designed with or without the riving knife.........If a guarding system is designed with a riving knife, it shall meet the additional requirements of Annex AA. If a guarding system is designed without a riving knife, it shall meet the additional requirements of Annex BB.

The Standard also includes further safety instructions for all saws on kickback causes and related warnings.

I hope that this is of help.”

These standards are not, however, drawn up by HSE, and are not HSE documents, copies may be available through good books sellers, libraries or BSI http://www.bsigroup.com/en-GB/

Kind regards

Keith (fro HSE Advice)

So, what do you guys make of those answers?

 

[Eric The Viking]

The thin saw-plate thing strikes me as hubris. It's the teeth of the saw that catch, not the plate pinching (at least, not for many years on handheld saws), and, of all the saw types, handhelds are probably the most likely to be forced through stock when blunt.

With a hand-held saw, the most likely reason for kickback is the operator twisting it off-line in use, and there are two axes in which this can occur: direction left-right, and tipping-over.

As the owner of a Makita (which I like a lot, incidentally), I'm reluctant to say this, but I think Festool have it right (with, IIRC, a spring-loaded, retractable riving knife). On a rail, it's relatively safe. Freehand or against a guide, not so good.

E.

PS: Of course, a properly set up rail saw also has the blade on a very slight skew to the forward movement (thickness of 80g paper front-to-back). This is to give a clean finish to the stock under the rail, BUT it must also increase the chance of kickback. Another point in favour of Festool...

 

[GLFaria]

So, what do you guys make of those answers?

Thank you very much for this report

The answers, or lack theroff, from Bosch are apalling, and only confirm a feeling I already had for some years - Bosch couldn't care less for their smaller products customers (I guess they may act differentelly when they are dealing with a big company, trying to sell heavy equipment).
It will hit back someday. As for me, unless I have no other choice, Bosch is written off.

One thing strikes me - all makers seem to shield themselves behind legislation for not supplying a riving knife provision. Never mind if this may be a safety issue for the operator, as the regulations say there is no need for it, they choose not to supply it. A bit it shocking.

 

[petermillard]

Perhaps the retracting/sprung riving knife is still a Festool patent, like the click-stop depth adjustment?? Would certainly explain why no other manufacturer uses it.

 

[Hugo_Wolfwhistle]

The thin saw-plate thing strikes me as hubris. It's the teeth of the saw that catch, not the plate pinching (at least, not for many years on handheld saws), and, of all the saw types, handhelds are probably the most likely to be forced through stock when blunt.

They seemed to be suggesting that if the teeth do begin to get a bit pinched, then if the saw is powerful enough and the teeth are sharp, then they should just cut rather than bind, and it would only be if the teeth were blunt or the disk of the blade got pinched that it would actually grab the blade. As I said, not sure if this is true or not, but I could sort of see how it could be true, especially on the more powerful saws with the constant speed electronics.

I guess that it would only apply with sharp teeth though, but then again the manufacturers probably say you should always use sharp blades anyway. You are obviously right though, I imagine a lot of people use fairly blunt blades in real life.


Incidentally, I just noticed that screwfix's deal of the day was this circular saw blade from Dewalt;
http://www.screwfix.com/p/dewalt-dt...-of-3/24169?cm_sp=Landing_page-_-DOTD-_-24169
In the description I noticed that it said "Suitable for Corded Saws with No Riving Knife", and also if you look at the picture of the blade it's self, then there is clearly a diagram indicating that it should not be used in conjunction with a riving knife. I have never seen that on a blade before though, and I can't think of a good reason for it either, however maybe it does suggest that the blade does have an impact on if a riving knife is needed or not.

With a hand-held saw, the most likely reason for kickback is the operator twisting it off-line in use, and there are two axes in which this can occur: direction left-right, and tipping-over.

As the owner of a Makita (which I like a lot, incidentally), I'm reluctant to say this, but I think Festool have it right (with, IIRC, a spring-loaded, retractable riving knife). On a rail, it's relatively safe. Freehand or against a guide, not so good.

Makita's point on this was that a riving knife wouldn't actually be very effective at preventing a kickback due to operator twisting off-line/tipping as the knife isn't rigid enough. The Makita guy was saying that the riving knife on the hand held saws was only really designed to prevent kickback due to the timber pinching the blade (e.g. due to natural wood tension stress movement or due to incorrectly supporting the wood). Therefore he was saying that they think it is better to give up the riving knife (which only protects against some types of kickback) so that they can make a better guard which reduces the damage if the saw kicks regardless of what caused it.
I don't think this applies to the riving knives on table saws though which I assume must be more substantial or something.

One thing strikes me - all makers seem to shield themselves behind legislation for not supplying a riving knife provision. Never mind if this may be a safety issue for the operator, as the regulations say there is no need for it, they choose not to supply it. A bit it shocking.

I suspect I maybe just couldn't get to speak to the right person at Bosch, I reckon if they would have bothered to forward my questions on to their design team, then they would have been able to answer similar to the others. Just a shame that they didn't seem to want to do that.

In terms of the hiding behind regulations, I can see why they do that. I work in Engineering, and it is quite common that companies, even rivals, will group together into industry bodies, and then they decide how they are going to interpret national standards and regulations in a common way between all companies. That way if they all stick to the common interpretation and way of doing things, then it becomes much harder for one of them to be taken to sued.

Personally I think it is probably a good thing that they all follow the standards and regulations, but I wish it was clearer why the regulations changed in this case. For example, if they could show some reasoning and evidence for why the change is good.
The general opinion from most wood workers I have spoken to seems to be that the riving knife does help, but if the manufacturers or regulatory bodies could show conclusive evidence to the contrary, then that would be something at least.

What was very disappointing was the response from the Health and Safety Executive on the subject. They say to refer to the British Standard BS EN 60745-2-5:2010 (actually a European standard) and then say they are not responsible for the standard themselves, however when I asked British Standards about who writes that particular document, they told me the people on the committee and it is basically the HSE and the trade body for the power tool manufacturers! The other members were more to do with the environmental and electrical aspects.


Anyway I found a copy of the European standard in question and have been reading through it to see what it actually says. Unfortunately it doesn't give reasons for the changes explicitly, however to summarise what I have learned from it so far;

• The main concern of the regulations does indeed seem to be focused on the blade guard and it's speed and reliability. In particular the regulations say;
  

  19.102.2 For saws having a blade with a diameter less than 210 mm, the closing time of the lower guard shall not exceed 0,2 s. For saws having a blade diameter 210 mm and above, the closing time of the lower guard in seconds, shall be less than the numerical equivalent of the largest specified blade diameter, expressed in metres, but not more than 0,3 s.
  Compliance is checked by measurements. The measurement is carried out at maximum depth of cut and 90°. The saw is held with the base plate in horizontal position, the lower guard being at bottom. The lower guard is retracted fully and then allowed to close.

• The regulations also say that the guard must be designed to work at this speed even after a life of at least 50,000 open/close cycles.
• It specifies that the reliability and speed of the guard closing must not be affected by build up of dust from cutting. In particular it says;
  

  17.102 The lower guard, or the guarding system as shown in Figure 104, shall be resistant against environmental and foreseeable dust accumulation.

• The regulations require that the guard closing time of the is tested after the saw has performed 1000 cuts in soft wood, then 1000 in 5 layer ply, then 1000 in MDF. Without any cleaning of the dust, and without dust extraction, the closing time must still meet the time requirements.
• The regulations also require that the guard closing time is met after the saw has been dropped 3 times from a height of 1m onto concrete. The saw must be dropped in what the regulations describe as the most unfavorable positions.
• The regulations also say that on plunge saws, if the blade retracts into the housing, it has to lock in the retracted position automatically
• The regulations has warnings about even light interference between the riving knife and blade guard causing the blade guard not to retract properly or fast enough.
• It also seems concerned about the riving knife getting bent during drops, which it says can actually cause kickbacks.

Having read the regulations, I can see what Makita were saying about doing away with the riving knife in order to improve the blade guard (making it solid with no slit in it). I am not saying that they are right, just that I can see their point.

At work when I have to carry out hazard analysis (e.g. for FMEA or PUWER assessment of equipment I am designing), we assign hazards a category for probability of occurring (Very Low, Low, Medium, High and Very High) and then a category for consequence. We then put them in a matrix which shows the level of hazard. If the level of hazard is medium or high, then we have to do something about it. The hazard level can then be reduced by either reducing the chance of it happening, or by reducing the consequence if it does happen.

It seems to me that having a riving knife reduces the hazard by reducing the probability, whereas the saws without the knife presumably are reducing the hazard by trying to reduce the consequence when an accident does happen.

I did ask a safety consultant if it was better to reduce the probability or consequence (in general, not just for circular saws), and he thought it was better to reduce consequence.

Not that I am saying I know which is best in terms of saws though.

 

[Eric The Viking]

Thanks for all the dogged hard work. It's been really interesting, this thread.

 

[GLFaria]

Hugo_W, thank you very much for all this information.
You have been very thorough in your research and very detailed in your report. Very interesting.

 

[nanscombe]

I use neither circular not table saws but ...

On a table saw, the heavy saw is not likely to move so if the blade is pinched by the wood it's more likely to throw a piece of wood back at you instead so a riving knife would help in avoiding the problem.

With a circular saw the wood is likely to be clamped down so if the blade binds the entire saw, with still spinning blade would likely be pushed towards you. Perhaps the thinking is that it is safer to get the guard around the spinning blade as quickly as possible.