Table saw blade kerf

[matt carpenter]

Hi, I have just got myself a new blade for my Dewalt DW 745 and it is a thin kerf 2.1mm
The supplied riving knife is 2.3mm
Is this safe to use? I can see that it will be very close but is this within tolerances?
Any help on this would be appreciated.
Thanks.

 

[Doug71]

The riving knife should be thinner than the kerf of the blade but thicker than the plate.

 

[Sideways]

Send the blade back and get another. 2.6mm kerf, say, will probably be a decent fit with the riving knife that should be (about half way, ish) between the width of the plate and the width of the kerf as Doug says above.

 

[matt carpenter]

The riving knife should be thinner than the kerf of the blade but thicker than the plate.

Thanks Doug that is how i understood it also, i was just wandering if i could get away with the .2mm difference over or if anyone had tried, but on reflection i dont think it is worth the risk and have anwsered my own question.
Thanks for your help.

 

[matt carpenter]

Send the blade back and get another. 2.6mm kerf, say, will probably be a decent fit with the riving knife that should be (about half way, ish) between the width of the plate and the width of the kerf as Doug says above.

Thanks Sideways i think that is my best option and will do that.

 

[matt carpenter]

On a side note can anyone see a problem with me using the 250mm 2.1kerf 40T blade on my mitre saw instead?
The saw has the same bore but requires a 254mm blade, would this be ok to use in anyones opinion?

 

[ChaiLatte]

...I was just wandering if i could get away with the 0.2mm difference...

Just some food for thought:

If the blade is not running perfectly true on the spindle/arbor, it will cut wider than its nominal measurement. If you have the measuring kit, you could do a rough calculation of this with your existing blade (because you cannot open the new one to test it or then you cannot send it back).

There will be manufacturing tolerances in the blade - I wonder if these tend to make it wider or narrower.

The riving knife might have a thick coat of paint on it such that sanding off the paint would reduce its width. Is the riving knife measurement quoted above one you have actually measured or quoted from the manufacturer? A replacement riving knife is probably cheaper than another blade and could be modified to suit.

 

[Doug71]

On a side note can anyone see a problem with me using the 250mm 2.1kerf 40T blade on my mitre saw instead?
The saw has the same bore but requires a 254mm blade, would this be ok to use in anyones opinion?

Table saws use positive hook blades but on a mitre saw or radial arm saw you should use a negative hook blade. Theory is if you use a positive hook blade on a mitre saw or RAS the blade wants to grab and feed towards you when you are cutting (also lifts the wood), you can get away with a bit of positive hook on mitre saws but it's not a good idea on a RAS.

Sorry, all my responses make me sound like the blade police

 

[matt carpenter]

Table saws use positive hook blades but on a mitre saw or radial arm saw you should use a negative hook blade. Theory is if you use a positive hook blade on a mitre saw or RAS the blade wants to grab and feed towards you when you are cutting (also lifts the wood), you can get away with a bit of positive hook on mitre saws but it's not a good idea on a RAS.

Sorry, all my responses make me sound like the blade police

Thanks again Doug your advice is much appreciated, i had not heard of +/- hook on blades before so its good to know, i also have not seen this described in the sales blurb when looking to purchase a blade so will do some more research.
Thanks again.

 

[johnnyb]

usual 250 blade is 3.2mm kerf. 2.xxx is thin kerf. easier to swap your riving knife(an old saw plate makes a perfect one as it's the right size!)
I say because I reckon a thin kerf will suit your small saw much better on thick rips. I will draw way less amps.

 

[matt carpenter]

Table saws use positive hook blades but on a mitre saw or radial arm saw you should use a negative hook blade. Theory is if you use a positive hook blade on a mitre saw or RAS the blade wants to grab and feed towards you when you are cutting (also lifts the wood), you can get away with a bit of positive hook on mitre saws but it's not a good idea on a RAS.

Sorry, all my responses make me sound like the blade police

Have done some research on the +/- rake on blades, found it very interesting and learnt a lot thanks again.
One thing i noticed though is how many companies out there are selling 15degree positive rake as good for mitre saw, after reading about it i dont know how they can get away with it!