Cutting down a riving knife.

[Steve Maskery]

Jacob is mistaken, I have never filmed what can go wrong with an overarm (also called a SUVA-style) guard. I HAVE filmed how to make and use one, it's on my Tablesaw Safety DVD, which is part of my Tablesaw DVD set.. I'm not supposed to advertise, but you did specifically ask for a link about it.

I have a different view to Jacob. He is right about a RK-mounted one being more convenient and always there, but, as you are finding out, such an arrangement is restricting. A SUVA guard offers all the protection and greater flexibility regarding non-severing cuts.

The biggest challenge with SUVA guards is that of rigidity. Its mounting point is a long way away from where it is used and so it can easily waggle about. I don't like things waggling about on my TS, thank you very much. So my support arm is supported at TWO positions, the far RH corner of my TS and in a shoe mounted to the top of my fence. The boom arm rides in this shoe wherever the fence is set.

It has two lateral positions, centrally of the blade for 90 deg cuts, and a tad further over to the right for when the blade is canted over.

I think it is excellent and I wouldn't go back to the RK-mouted one, even if I still had it.

However, the event Jacob has in mind is not a film but a post after I had an accident with it.

However, this was not a fault with the design, it was because I had failed to ensure that it was adjusted correctly and secured. A loose RK guard could have done the same. It was user-error. Particularly embarrassing user-error, given my high-profile stance on TS safety, but user-error, nonetheless. And the accident happened in the presence of a Senior H&S Officer.....

There are some operations I do when even this guard is unsuitable, for example when I am using my tenon jig or deep-ripping, so I have a magnetic stand-alone guard which I can set right up to the workpiece and stops me getting my fingers too close. It would not prevent me falling onto the blade, though, which is a common cause of injury as people learn over to retrieve the workpiece, so I'm not suggesting that it would pass H&S approval. But I use it when the only other alternative would be not to use a guard at all. I NEVER use the TS totally unguarded and I try to persuade other people not to as well.

 

[Jacob]

...... A loose RK guard could have done the same. ....l.

My point is that it would not do the same. It's in line with the blade so if it comes into contact then it just gets nicked - it doesn't get yanked sideways.
In fact mine has several saw marks on it where it has been pressed against the blade accidentally - with no consequence - you'd hardly notice it happening. This in turn means you can set it very close to the blade and further reduce possibility of accidental contact.

 

[MJP]

Thanks Steve. There's a lot there for me to think about.

 

[MJP]

Well, having read through Steve's experiences and followed all the comments I think the only sensible thing for me to do is buy another riving knife and fix the crown guard back on the machine when I'm not using the sled. easy enough to change - just slacken two allen bolts, a thirty second job, no alignment problems. So, the question now is where do I find a replacement RK for my Ryobi ETS 1525 TS, which appears to be the same as the Clarke CTS10D? Anyone got the handbook on the CTS10D which shows the RK for me to check if it's the same? I suppose that I can buy a new Clarke RK through Machine Mart?

 

[Jacob]

Riving knives tend to be similar so if a new one for a different machine fits the blade diameter it might possible to file/drill to make it fit the mounting points.

 

[murrmac]

I have never quite "got" this UK fixation with riving knives.

I worked for many years in cabinet shops in the US back in the 90's and the riving knife was non-existent... leastways at that time, although I believe the H&S mafia have implemented some changes since my day.

Admittedly, almost all the work was with sheet materials ... mostly maple ply of different grades, and occasionally some melamine ... the riving knife played no part whatsoever ... a total irrelevancy.

When it came to ripping solid timber, the first rip would be done freehand on the bandsaw, the stock would then be surfaced and edged on the planer and jointer, and then trimmed to size on the tablesaw prior to final dimensioning in the planer (thicknesser). The offcuts would by definition fall off to the left of the blade, and were so thin that kickback was not ever going to be a problem.

We just never needed a riving knife.

As far as blade guards were concerned, (which was and is a totally different issue from riving knives) the more sophisticated and advanced shops used overarm guards, but these guards invariably incorporated ports for additional dust extraction, which IMO is the main advantage of an overarm guard in the first place.

Back in the UK , I still don't have a riving knife on my tablesaw ... for me, it would be a totally unnecessary PITA , since I am never going to have any kickback on any workpiece ... prior and proper use of bandsaw and jointer ensures this. I do have polycarbonate overarm guards, (ie plywood guards with polycarbonate windows) but their main function is to provide additional dust extraction.

btw, if you are going to fabric ate overarm guards, the moving adjustable parts need to be made out of square box section , not out of round tube.

 

[Jacob]

OK there are other ways and means of avoiding problems. It sounds like you were doing repetitive work on industrial machines, I expect with large sliding tables and procedures well sorted out
We are talking about small machines in one man shops where there is likely to be very diverse patterns of work. The riving knife solves a lot of problems e.g. you can rip much more accurately and quickly with a TS rather than a bandsaw, in one operation , not several as you describe. Some small shops won't even have a bandsaw. I have a Startrite 352 which I occasionally use for ripping but not if I can help it - expensive to use - ripping drastically shortens blade life and it is difficult to handle large pieces.
And blade guards aren't a totally different issue from riving knives - the riving knife plus crown guard is the safest and simplest possible set up and you can't have the guard without the riving knife.

PS nearly all riving knife crown guards have dust extraction too via a very effective port, close to the blade. Picture here with one not in use. Most extraction is from below but for MDF etc. using the crown guard extractor would be a good idea and better than one slightly more remote on an over the top guard.

PS just noticed the picture I lifted is same machine as mine (Minimax). Thought it looked familiar! Very good machine IMHO.

 

[MJP]

Jacob - thanks.

Found a pic of the Clarke CTS10D RV, which has the same base but slightly different top, so I'm trying to acquire one of these - should work OK. Found a parts & price list of Ryobi ETS1525 TS showing the RV but can't find any contact details to enquire about buying one!

 

[PAC1]

Murrmac, I am not sure it is helpful to suggest riving knives are generally not needed simply because you are able to work in a way that reduces the risk of kickback. The reality is in the UK we use table saws to rip timber. As such a riving knife is an essential safety device and a legal requirement. Also most UK machines rely upon the riving knife to mount the crown guard.
I am not knocking your method of using a bandsaw to rip timber, but my experience is that bandsaws in the UK are not set up for ripping and are not fast enough. It also depends on what you are doing. If I am making 20 doors there is no way I would use my bandsaw to rip 100m of 150 x 75/68 material down. If I am making lipping out of very expensive hardwood I would use my bandsaw to minimise waste.
Even cutting sheet material on a table saw can be dangerous without a riving knife and there is a wonderful USA video to prove it
Further in the UK the HSE require that a riving knife should be fitted and properly adjusted on all table saws.
What you missed when telling us that in the USA they do not have riving knives fitted to table saws is the high level of injuries caused by this omission, all the litigation that follows and the market for sawstop device to do hundreds of US$ damage to your saw all because you do not have a 20$ riving knife and crown guard.
In the UK we cannot "get" the USA's fixation with taking an unnecessary risk.

 

[Jacob]

....
Further in the UK the HSE require that a riving knife should be fitted and properly adjusted on all table saws.....

HSE allows a low riving knife without attached guard but only if there is over arm guarding or similar protection in place.
Not having either form of knife seems insane - it's such a simple, cheap and effective device.

 

[murrmac]

The tablesaw I use is one which I purchased new in the States ...a Grizzly 1023 left-tilting saw, which I shipped back here in 2002. It doesn't have a facility for fitting a riving knife (although the modern versions do have a riving knife). If I had the choice again, I would in fact choose to have a riving knife, but I have long grown familiar with using the machine as is.

On the occasions when I do rip solid timber on the tablesaw , I just tap a wedge into the kerf after the front edge of the workpiece has come past the back of the blade by about 8". This prevents any binding on the back edge of the blade. Needless to say, I am never ripping huge quantities at any one time ...I do get that if you are doing hundreds of rip cuts, a riving knife would be necessary.

One other thing I like about the American saw (in addition to the left tilting blade) is that the arbor is long enough to fit a stackable dado head ...I understand that the EEC has decreed that all modern tablesaws in Europe must have a much shorter arbor which makes fitting a dado head impossible. It is a most useful accessory, however, one which I use regularly.

 

[Jacob]

... ...I do get that if you are doing hundreds of rip cuts, a riving knife would be necessary.....

Helps if you are just doing one cut. Numbers don't come into it.

 

[Ttrees]

I am not knocking your method of using a bandsaw to rip timber, but my experience is that bandsaws in the UK are not set up for ripping and are not fast enough. It also depends on what you are doing. If I am making 20 doors there is no way I would use my bandsaw to rip 100m of 150 x 75/68 material down. If I am making lipping out of very expensive hardwood I would use my bandsaw to minimise waste.
.

I was just going to ask a question relating to this
I'm waiting to receive a 1.3TPI blade for my 24" bandsaw, and wondering about how much more expensive it's gonna be..eg
Would I go through 3 bandsaw blades for every TS blade for a given amount of timber ?
I need to cut a lot window frames with putty on them, and want to minimise waste.
This putty cannot be hacked off completely, so I need to cut beyond it, and waste a bit more timber than I want.
I might try Louis Sauzedde's bandsaw sharpening regime, if I happen to blunt it...https://www.youtube.com/watch?v=SoaOkqi-xxs
Hopefully this blade can get this arduous task done.

I have questions about the overarm guard still
It is a prototype yet ...need non shatterable plastic and to work on the upright to make it more rigid.

How close to the blade is your overarm guard folks when your blade is square to the table ?
My guard ended up a bit far away from the blade ... I can adjust it with ease but hopefully it will still clamp the overarm and stay in position...
Along with this, the struts/attaching arms to the guard is kinda in the way of my pushstick.
This might need to be flat stock closer to the guard ...I might take the grinder to the last few inches if it proves to be bothersome.
Hopefully if moving the guard closer to the blade will give me enough space for the pushstick though.

I get the impression some of these designs lift up with the work ? ...doesn't happen with mine.
The back of my riving knife is hitting the thing, so might need to make another shark fin style.
I will try and source the right plastic first though.

Do you guys have a different setup pushstick wise for use with a guard ?
Tom

P.S ....Photo's mocked up for illustration purposes ...I don't use this guard as it's a prototype only

 

[Jacob]

A TS is much better for ripping and is much easier to use especially if you are cutting long lengths or wide pieces. The only advantage of a band saw is depth of cut
If you are cutting through material then the crown guard is far superior to an over arm guard such as your mock up. Lots of reasons see above. Smaller footprint too, so easier with the push sticks.
If you are cutting slots then you guard could be OK as long as it is very strongly mounted and can't be knocked out of place in the ordinary way of things, but possibly more important than the guard would be push sticks - especially as the end of the workpiece passes over the blade and is exposed.
Personally I only use the one pattern of push stick though I make copies from ply or mdf. I really don't see the point of you odd shaped one!
Mine's the 'standard' pattern and it's much better designed than first impressions and widely available dirt cheap.

 

[RogerS]

According to HSE figures, circular saws (table saws/panel saws) are the cause of most accidents. Here's one instance from their website

An employee was left permanently paralysed on one side of his face after his skull was fractured when a crown guard from a circular saw came loose. The two nuts holding the riving knife to the machine are believed to have been loose, allowing the attached crown guard to make contact with the rotating saw. The guard, complete with riving knife, was thrown directly forward, hitting the employee in the head.

Ttrees...there is nothing wrong with your guard set-up. Regarding your bandsaw question and cutting through putty, I'd give Ian at Tuffsaws a call and ask his advice. Maybe one of his M42 blades might be more suitable. I'd be more concerned about hitting any of the metal sprigs with the blade but an M42 blade won't mind too much.

 

[Ttrees]

Roger
I am using the bandsaw to cut past the putty.
Unfortunately, even M42 blades doesn't hold up to putty
Not that I was using it to cut through it at any point, but maybe rubbed against it a bit trying to conserve wood.
As I said the putty cannot be hacked off completely, this effort was to make sure the metal detector wand has the best chance.
No hits yet so far... I always have another check on each piece before each cut.

Jacob
I might make more patterns for trying out.
I think this one feels solid but I feel it might be a bit close, I end up gripping it high like a gear shift on a car, not like, say, a gun grip.
I would guess that pattern you shown would hurt my wrist, although John Heisz has made a compromise between both.
I might play around with that idea.
" Is This The Best Push Stick Ever? I build it scrap bin "
I was looking for alternatives that would go under the guard aswell as the other style.
I might say your displayed one might be the only solution for narrow rips inbetween the guard and fence.

Thanks for comments
Tom

 

[RogerS]

Tom

If you have a lot to do then you could hire a putty softening lamp http://www.rmears.co.uk/putty-lamp-hire/

 

[Steve Maskery]

An employee was left permanently paralysed on one side of his face after his skull was fractured when a crown guard from a circular saw came loose. The two nuts holding the riving knife to the machine are believed to have been loose, allowing the attached crown guard to make contact with the rotating saw. The guard, complete with riving knife, was thrown directly forward, hitting the employee in the head.

That is why RKs should have a closed slot rather than an open one. With an open slot the RK can come off if the bolts just become a bit loose, but with a closed end the bolts have to come right off (or shear completely) before the RK can fly.

 

[Ttrees]

So that's what you were on about Steve :roll:
I was thinking it was a closed slot for the crown guard
I suppose I'll know for again

Thanks for the link Roger
I think Ill be making sure to cut the wood behind the putty any more though....
Hopefully

 

[Jacob]

.
I might make more patterns for trying out.
I think this one feels solid but I feel it might be ....

The important bit is the birds mouth shape. It imitates a hand- when you hold something down with your knuckles and push with your thumb and/or the heel of your hand. The standard pattern also seems spot on for height of typical saw bench and feels very natural. I'd just buy a couple to try out. You will get used to them and find you don't need any other pattern. Took me some time to work that out after several goes with various random stick selections.