Tabel Saw Blade thickness and riving knife

[RedMist]

I'm fairly new to using table saws. I'm changing out the blade my Bosch GTS 10 J to one more suited for cutting wood via rip.

But for the life of me I cannot understand what the manual is telling me...

My new blade is 2.8 thick. Will this cause a problem? In my mind, the `cut` is .5 thicker than the riving knife so how can the riving knife come into contact with the wood in any way?

 

[LancsRick]

The point is just the riving knife SHOULD be in contact so that the wood tries to bind on the knife not the blade. Personally I'd swap the blade, but some people with more experience might tell you it's ok, I don't know.

 

[SteveF]

are you sure new blade is 2.8?
or are you measuring the teeth?

Steve

 

[RedMist]

The blade i am getting is

I must admit initially i had the opposite problem. The first replacemant blade i bought was too thin, i was 254x 2 x30 and I found when ripping through wood the riving knife was too thick. The wood couldnt get past it.

Options for wood blades for this machine seem limited. If this cant do it, I'm worried !

I'm not 100% if the blade is 2.8 thick or if thats including the teeth width.

 

[PAC1]

2.8mm is accross the teeth so that is the correct size for your riving knife

 

[Steve Maskery]

You really do need to understand this.

The width of the cut is called the kerf. Traditionally this is 1/8", or 3.2mm.
But the body of the blade, called the plate, is thinner, because the teeth stick out each side. The difference between the two is called the clearance.

Wood can, and does, move as it is being cut, as stresses in the wood are being released. It can move in a way which opens up the kerf, which is why we use a short fence for ripping, or it can move to close up, which is why we fit a riving knife. Without one the risk of kickback, which is not at all trivial, is increased.

With increased technology, blades can be made thinner. So a rip blade can be only 2.4mm kerf, on a 2mm plate, for example.

The riving knife (RK) must be at least the thickness of the plate but no thicker than the kerf. So yes, if you have different thickness blades, you need different thickness RKs, and that often means making your own from ground flat stock.

This is all important if you want to use your saw safely.

 

[RedMist]

Thanks Steve that helps a lot !

But what does this mean "which is why we use a short fence for ripping" is this an extra fence on the opposite side to the main fence? I was thinking of putting a featherboard there...

 

[PAC1]

Read this http://www.hse.gov.uk/pubns/wis16.pdf

 

[meccarroll]

A must view, how stupid is this:

https://www.youtube.com/watch?v=u7sRrC2Jpp4


A riving knife and crown guard would help prevent this.

 

[Steve Maskery]

https://www.youtube.com/watch?v=d7QXIN2X8-w

This is an earlier version of the one I use now, and yes it looks dated, but the essence of it is sound.

 

[Jacob]

I'm fairly new to using table saws. I'm changing out the blade my Bosch GTS 10 J to one more suited for cutting wood via rip.

But for the life of me I cannot understand what the manual is telling me...

My new blade is 2.8 thick. Will this cause a problem? In my mind, the `cut` is .5 thicker than the riving knife so how can the riving knife come into contact with the wood in any way?

The cut has to be as wide as or wider (2.3 or more) than the riving knife (2.3) or it could bind. It's a confusing bit of text though - not sure what the "blade body thickness" bit refers too - the saw blade or the riving knife blade?
The diagram - the 79mm is max depth of cut - the 2.3 solid line is the riving knife (from above) and the dotted line is the saw blade - which needs to cut a 2.3mm or thicker kerf.

 

[Jacob]

A must view, how stupid is this:

https://www.youtube.com/watch?v=u7sRrC2Jpp4


A riving knife and crown guard would help prevent this.

That fat american berk again! The kick-back is the least of his problems - he nearly loses a finger but hardly seems to notice!
This is because he is using grippers instead of long birds-mouth push sticks.
Grippers and blocks like that are inherently dangerous - they bring your hand nearer to the blade instead of further away. Should be banned.
And yes - riving knife and crown guard.

 

[meccarroll]

Hi RedMist,

Try looking at the CMT range of saw blades:

http://www.3dtoolingltd.co.uk/CMTCircularSawBladesUK-Category-385.html

Their 250mm range have a Kerf of 3.2 and a Plate thickness of 2.2 so will all fit with your riving knife. You will not have to change your riving knife even if you change your saw blade so long as you use either the CMT range or a similar specified range.

I think they may be slightly dearer than the bosch saw blades but they are quite good quality and give good results. Precision saw blades give a much better finish and are quieter than cheap ones (they run true). It all depends upon the work and finish you need to end up with but also on your finances too.

You should have an Auxiliary parallel fence (item 49 in your saw manual) that can be used as a short fence fixed to the main fence.

Mark

 

[Vann]

...But what does this mean "which is why we use a short fence for ripping" is this an extra fence on the opposite side to the main fence?...

No. It means a short main fence.

I assume your fence (like most) is to the right of the blade. If you're ripping a length of timber and the right-hand piece of the cut bows to the right, it will extend harmlessly beyond the short fence. If you have a long fence it will try to bow to the right, but the fence will prevent that, forcing the piece you're cutting left and into the blade - which markedly increases the likelihood of a kick-back.

If you only have a long fence, you can attach a timber packer that terminates at the blade, to act as a short fence.

HTH.

Cheers, Vann.

 

[Lons]

...But what does this mean "which is why we use a short fence for ripping" is this an extra fence on the opposite side to the main fence?...

No. It means a short main fence.

I assume your fence (like most) is to the right of the blade. If you're ripping a length of timber and the right-hand piece of the cut bows to the right, it will extend harmlessly beyond the short fence. If you have a long fence it will try to bow to the right, but the fence will prevent that, forcing the piece you're cutting left and into the blade - which markedly increases the likelihood of a kick-back.

If you only have a long fence, you can attach a timber packer that terminates at the blade, to act as a short fence.

HTH.

Cheers, Vann.

My saw is a SIP 01332. Full length fence so I fitted a length of 15mm thick Corian which extends as far as the centre of the blade, works a treat as the Corian is very smooth and offers little resistance.

All I did was countersink 3 bolts into it with square nuts on the back which slide inside the aluminium fence profile so If I wanted to adjust it is very quick and easy.
Remember that after fitting the auxilliary fence you need to adjust the main fence to the rule or you'll be cutting undersize.

Bob

 

[Bodgers]

A must view, how stupid is this:

https://www.youtube.com/watch?v=u7sRrC2Jpp4


A riving knife and crown guard would help prevent this.

That fat american berk again! The kick-back is the least of his problems - he nearly loses a finger but hardly seems to notice!
This is because he is using grippers instead of long birds-mouth push sticks.
Grippers and blocks like that are inherently dangerous - they bring your hand nearer to the blade instead of further away. Should be banned.
And yes - riving knife and crown guard.

In all fairness, it was his intention to induce kick back, so he did a series of wrong things to demonstrate it. He also mentioned afterwards just how close he got. The daft thing was trying to demonstrate it to begin with.

A better (I.e. Safer) video for a kickback demo is Mattias Wandel's...he is also a fan of birds mouth push sticks rather than blocks grippers where you end having to pass your arm/hand over the top.

 

[JohnPW]

A must view, how stupid is this:

https://www.youtube.com/watch?v=u7sRrC2Jpp4


A riving knife and crown guard would help prevent this.

That fat american berk again! The kick-back is the least of his problems - he nearly loses a finger but hardly seems to notice!
This is because he is using grippers instead of long birds-mouth push sticks.
Grippers and blocks like that are inherently dangerous - they bring your hand nearer to the blade instead of further away. Should be banned.
And yes - riving knife and crown guard.

In all fairness, it was his intention to induce kick back, so he did a series of wrong things to demonstrate it. He also mentioned afterwards just how close he got. The daft thing was trying to demonstrate it to begin with.

A better (I.e. Safer) video for a kickback demo is Mattias Wandel's...he is also a fan of birds mouth push sticks rather than blocks grippers where you end having to pass your arm/hand over the top.

If you mean this:
https://www.youtube.com/watch?v=xFkHmgRIkOI

then he is either deliberately being misleading or is just stupid.

because kickback is caused by the rising blade and he only makes short cuts so that the rising blade is not touching the wood.