riving knife on table saw

[NOTTNICK]

I have a Makita table saw (MLT100)
It comes with a riving knife.
I need to cut some rabbets and grooves into quite a lot of timber for a project.
I can't do this with the knife in place an it projects above the blade.
I guess I need to remove the knife to do this.
However, I read about kickback and safety, so am not sure if I should be doing this.
The manual says it shouldn't be removed.
I'd appreciate advice on this.
Cheers
Nick

 

[woodbrains]

Hello,

There should also be a guard connected to the riving knife.

Neither should be removed without an alternative fitted, as they both constitute the first line of safety on the saw. No one here should advise you to remove them, as simply, if you have an accident, their advice may well have contributed to it.

That said, if you do want to make partial thickness cuts, you have to do two things. Get another riving knife that can be cut down so it is a few millimeters below the top of the saw blade. Keep the other one so it can be re- fitted with the guard for normal sawing. With the short riving knife, you now need to provide some guarding so you are safe. A tunnel guard will do the job, look it up on the internet.

Alternatively, and a better solution, is to cut rebates and grooves on a spindle moulder or router table. But i guess you have neither of these!

Mike.

 

[NOTTNICK]

Hi Mike
Thanks for this. It is what I thought, and that's why I checked.
The cut down knife looks like a good idea.
I do have a router table and have used that in the past. It takes quite a while as I have to make quite a few passes (it is a sturdy table with a 1/2" Dewalt router).
I thought the table saw would be quicker and easier.
Can't find tunnel guards with a search though. Not too sure what you mean.
Cheers
Nick

 

[woodbrains]

Hello,

https://www.google.co.uk/url?sa=t&sourc ... 7YK8ekZXGA

Try here!

Mike.

 

[andersonec]

Just one thing, If you are cutting completely through timber the riving knife is there to stop the timber pinching onto the blade and then being lifted off the table and thrown forwards. When cutting grooves or rebates you will not be cutting all the way through so the wood cannot pinch onto the blade. Read into that what you like.

For anybody to fire Health and Safety at you they must first do a risk assessment.

 

[NOTTNICK]

Thanks for the link Mike.
Andersonec - I'll make my own interpretation of your post; appreciated. I'll bear in mind Mike's advice also.
Nick

 

[PAC1]

Just one thing, If you are cutting completely through timber the riving knife is there to stop the timber pinching onto the blade and then being lifted off the table and thrown forwards. When cutting grooves or rebates you will not be cutting all the way through so the wood cannot pinch onto the blade. Read into that what you like.

For anybody to fire Health and Safety at you they must first do a risk assessment.

That is not correct. The wood fibres can still move and trap the blade. Then there are two choices either the saw stops or more likely the wood is fired back at you at 100mph. Neither are good but the latter needs to be prevented so you need a Shaw guard or tunnel to stop the wood riding up the back of the blade and becoming a projectile. I have seen this happen and do not wish to see it again
Look up case hardening of kiln dried wood if you doubt the fibres can move.

 

[Mr T]

Woodbrains advice is quite correct, but I am sure it is regularly ignored in numerous one man workshops without mishap. That includes my workshop, however I would not allow a student to do this for obvious negligence liability reasons!

Chris

 

[Sawyer]

Removing the riving knife is a very bad idea. Alternatively, a portable circular saw can perform such cuts in reasonable safety, albeit a little less accurately.

 

[Mr T]

Woodbrains advice is quite correct, but I am sure it is regularly ignored in numerous one man workshops without mishap. That includes my workshop, however I would not allow a student to do this for obvious negligence liability reasons!

Chris

Before people think I regularly run my table saw without the riving knife please let me elaborate.

For most sawing operations it is a very bad idea to remove the riving knife or crown guard. However in the specific case of shallow (max 10mm) grooving I occasionally find it convenient to cut the groove on the saw with the knife at the level of the top of the teeth. I use push sticks and, as ever, stand well clear of the kick back firing line.

I have weighed up the risks of this procedure and decided that the risks and likely damage in the case of mishap are within acceptable bounds. This is something I can do in a one man workshop situation. As I said I would not allow anyone else to do this in my workshop.

I would be interested to know if other experienced one man operations take a similar, may I say "sensible" approach to machine safety. For instance do you always fit the guard when doing minor cuts on the router table? Or is it just me that likes to live dangerously?

 

[PAC1]

As you say for shallow grooves with a riving knife set just below the top of the blade the technique is sensible as the chance of the wood catching on the back of the blade is minimal. My only concern comes from a freak accident at college doing just as you say but the lecturer was on the other end and pulled the wood the last 6 inches or so. I was not expecting this and my push stick dropped off onto the blade. Being left handed the next thing I knew I was laid out. The push stick hit my abdomen and floored me. No damage done but lucky. Since then I have been very weary of the position of the push stick and learnt to use it right handed.
One technique I have adopted for grooves is to use the slider. Clamp the wood in place and push the slider to safely cut grooves

 

[woodbrains]

Woodbrains advice is quite correct, but I am sure it is regularly ignored in numerous one man workshops without mishap. That includes my workshop, however I would not allow a student to do this for obvious negligence liability reasons!

Chris

Before people think I regularly run my table saw without the riving knife please let nme elaborate.

For most sxawingb operations it is a very bad idea to remlve the riving knife or crown guard. However in the specific case of shallow (max 10mm) grooving I occasionally find it convenient to cut the groove on the saw with the knife at the level of the top of the teeth. I use push sticks and, as ever, stand well clear of the kick back firing line.

I have weighed up the risks of this procedure and decided that the risks and likely damage in the case of mishap are within acceptable bounds. This is something I can do in a one man workshop situation. As I said I would not allow anyone else to do this in my workshop.

I would be interested to know if other experienced one man operations take a similar, may I say "sensible" approach to machine safety. For instance do you always fit the fence when doing minor cuts on the router table? Or is it just me that likes to live dangerously?

Hello,

I got a kick back once, and swore it wouldn't happen to me again. This was a very long time ago, in my employers workshop, which was a signmaker's, rather than a proper cabinetmaker's shop. The tablesaw was shared with anyone who needed to make cuts, and as a consequence, people left the saw in a terrible state. Some used to regularly cut 8 by 4 sheets of ply freehand with no fence, guard or riving knife. So here I come trying to make something in my lunch break, so time being of the essence, didn't waste any by refitting the knife/guard. Anyway, I got hit in the eye by a lump of oak; luckily my cheekbone, eyebrow and nose took the main impact, and my eye survived fine. I had stitches in my eyebrow, and did look like John Merrick for about a week.

So I never remove any guards or the knife from my saw. I do use a cut down riving knife which is permanently fixed and use a SUVA guard, fixed to a post on the left of the saw. So I can do partial thickness cuts safely, but seldom do, I prefer a small spindle.

Save yourself the bother of learning the hard way, get a guarding system that never leaves the saw.

Mike.

 

[Paddy Roxburgh]

Hi Notnick,
I would be surprised if you found that grooves or housings were quicker on the table saw than the router table. You need to make many passes then clean up with a chisel or router plane. Rebates can be quick on on the TS as you can do them with only two cuts. If you only have a few to do you might be pleasantly surprised how quick a grooving plane/rebate plane can be, with the bonus of no dust and much less danger (there still is some danger, particularly getting your little finger caught between the work and the plane ooouuucchhh).
Paddy

 

[Mr T]

I got a kick back once, and swore it wouldn't happen to me again. This was a very long time ago, in my employers workshop, which was a signmaker's, rather than a proper cabinetmaker's shop. The tablesaw was shared with anyone who needed to make cuts, and as a consequence, people left the saw in a terrible state. Some used to regularly cut 8 by 4 sheets of ply freehand with no fence, guard or riving knife. So here I come trying to make something in my lunch break, so time being of the essence, didn't waste any by refitting the knife/guard. Anyway, I got hit in the eye by a lump of oak; luckily my cheekbone, eyebrow and nose took the main impact, and my eye survived fine. I had stitches in my eyebrow, and did look like John Merrick for about a week.

This is why I specified one man workshops in my posts. H&S regulations were designed for the sort of workshop you describe Mike. Unfortunately they ignored them!

Chris

 

[NOTTNICK]

Really helpful dialogue. All posts appreciated.
I'll try the router table first (I found the WR Cedar was splitting and clogging the table when I last tried cutting rebates, but this'll be Douglas fir, so maybe it'll be cleaner).
Otherwise I'll try a cut down riving knife.
I don't think I'll be needing a guard on top as there will be timber over the blade when cutting.
It's a few weeks yet so I'll have time to experiment first.
Cheers
Nick

 

[woodbrains]

I got a kick back once, and swore it wouldn't happen to me again. This was a very long time ago, in my employers workshop, which was a signmaker's, rather than a proper cabinetmaker's shop. The tablesaw was shared with anyone who needed to make cuts, and as a consequence, people left the saw in a terrible state. Some used to regularly cut 8 by 4 sheets of ply freehand with no fence, guard or riving knife. So here I come trying to make something in my lunch break, so time being of the essence, didn't waste any by refitting the knife/guard. Anyway, I got hit in the eye by a lump of oak; luckily my cheekbone, eyebrow and nose took the main impact, and my eye survived fine. I had stitches in my eyebrow, and did look like John Merrick for about a week.

This is why I specified one man workshops in my posts. H&S regulations were designed for the sort of workshop you describe Mike. Unfortunately they ignored them!

Chris

Hello,

Yes, I know one man workshops generally don't always follow strict H and S rules, as they don't legally have to. The point I was trying to make ( failed to make) was that once I had been bitten, even when I had my one man shop, I tried to be much safer, even though no one was watching! It was a nuisance initially, to make preparations to do work safer, when I could have just got the job done, but once the steps were taken, things then were always at hand, and I didn't have to worry about not being guarded. If I had just whipped the guard and knife off for a quick groove, then I would never had have made the right guards etc. I have now. We just need the discipline to tell ourselves not to make that cut until I get that guard sorted, and stick to it. Perhaps I wouldn't have had the self discipline myself if I hadn't had the kick back. I don't think others should chance a near miss to prompt them into taking the right action.

Mike.

 

[dynax]

Safety should be the primary concern when using any power tools, a few years ago i was working for a bloke and i needed to cut some 45 degree fillets, i spent about 20 mins looking for the guard for the saw, couldn't find it, anyway the bloke said haven't you cut them fillets yet, i said no i can't find the guard for the saw, he said don't worry about it just do it, i said no not without the guard, he muttered something and i said you do it then, so he did, first piece he rammed it through the saw, came back at him like a bullet, i said to him told you and walked out,

 

[Ttrees]

I have some questions and wish to clarify some things ....

Is it best practice to have the riving knife exactly the same height as the top tooth line on the saw blade ?

And is a low profile knife inferior to a riving knife with a flat top ?

Tom

 

[woodbrains]

I have some questions and wish to clarify some things ....

Is it best practice to have the riving knife exactly the same height as the top tooth line on the saw blade ?

And is a low profile knife inferior to a riving knife with a flat top ?

Tom

Hello,

The riving knife can be higher then the top of the tooth line and almost always is on as standard equipment on a TS. This has nothing to do with its effectiveness as a splitter, but is something to fix the crown guard to. This is the problem; people want to do partial thickness cuts so both the riving knife and guard get removed. Then they get forgotten about and the saw gets used for ripping etc. with neither fitted.

A riving knife cut short so partial thickness cuts can be made is no less effective than a high one. If it can be set level with the top of the teeth then it is most effective, but a mm or two below is practical; it is difficult to set the knife level to a curved blade and a smidge higher than the teeth is useless for partial thickness cuts, as it will bind. A touch lower is a safe compromise.

I don't think the shape of the knife is important as long as the leading edge conforms to the blade shape and is no more than about 8mm away (H and S advise) mine is about 4-5 mm. As long as the plate it is made from is the correct thickness, the flat topped ones or shark's fin shaped one or whatever, are effective. If you do cut your own down, it will have a flat top, regardless of the starting shape. The knife's thickness should be a little thicker than the saw plate and a little thinner than the tooth kerf. It is important to always buy the same kerfed blade, unless you have different thickness knives and swap them accordingly. But let's face it, who can be bothered, it is easier to get the right blades and leave the knife fitted permanently.

Mike.

 

[meccarroll]

I don't think I'll be needing a guard on top as there will be timber over the blade when cutting.
It's a few weeks yet so I'll have time to experiment first.
Cheers
Nick

In this case you should use a guard both on the side and top of timber being machined (areas exposing the rotating cutting edge) and one type of guard is a (pressure) shaw guard, which will help hold the timber in place when machining and protect you from coming into contact with the revolving blade. If for any reason the blade is exposed with no guarding then you could touch it by accident, guarding is really sensible to use.

Mark