Does the kerf size decrease

[mattsutton29]

Hi everyone. Just a quick question. I have a Mafell plunge saw and the fine cut blade is starting to feel blunt. I’ve cleaned all the teeth of resin etc.but still doesn’t feel on point. Pardon the pun. I was thinking of sending it off to be resharpened and was wondering if afterwards the kerf size would be altered as the splinter strip is cut for the particular kerf. And don’t want to replace the strips as it’s set for other (sharp) blades also?

 

[baldkev]

I guess it depends on the tooth geometry. If flat ground ( unlikely ) then no. if alternate bevel, it may reduce the kerf half a mm at most. If the teeth are not damaged, they wont take much off..

 

[Spectric]

It is not as simple as that, the Kerf is not what cuts the rubber strip but the combination of blade thickness and kerf which determines the offset. This means you can use blades with different kerfs but they do not re cut the rubber strip. Diagram below shows the calculations.

 

[Jameshow]

I guess it depends on the tooth geometry. If flat ground ( unlikely ) then no. if alternate bevel, it may reduce the kerf half a mm at most. If the teeth are not damaged, they wont take much off..

Would not the bevel be tapering into the kerf???
So no change to the kerf?

Thinking about it unless you lost all the teeth the kerf will not change, I'm getting there though...!

 

[baldkev]

@Jameshow
Flat ground teeth will be square with the blade, but alternate bevel teeth are often tapered ( but not always )
Edit: The top of the teeth will bevel down behind the cutting edge to create relief, so if it were ground down say 3mm, the overall diameter will shrink a bit and the width of kerf would shrink a bit. But just skimming a touch off to freshen the blade wont likely make a difference

 

[baldkev]

Lets put it a different way. Look at the teeth in question and see if the teeth edges are parallel to the blade / plate. If they taper down, there will be a slight change but not enough that you'll notice in operation. If they are parallel, it'll stay the same.
Either way, id just get it sharpened and carry on

 

[hlvd]

A blunt saw is a blunt saw, it’s either re sharpen or buy another.

 

[mattsutton29]

Thanks guys for the info. Yes I’ll get it sharpened

 

[Keith 66]

I always thought that saw sharpeners grind the front face of the teeth & maybe the top face. I have never had a blade come back where the sides had been ground unless it had had teeth replaced. Then the amount removed would be minimal.
So it should not make a difference

 

[ChaiLatte]

Consider the geometric shape of the carbide tip.

Is it a true cuboid with three pairs of faces perpendicular to each other? If it is, then removing material off the front face will not change its width (its area is constant with depth).

In reality, the carbide tip is the frustum of a (not necessarily right) rectangular pyramid. Therefore, removal of material from the front face (the base of the pyramid) will change its area (both its height and width will decrease). So when run along the track, the cutting tip will be a tiny bit further from the plastic strip but not enough to worry about.

Thinking about it, and it is something I have never seen mentioned, when mounting a brand new blade, if you put one or more paper washers between blade and flange on the track side, you could remove a washer each time it is sharpened. Would only work though if you never changed blades.

 

[johna.clements]

It is not as simple as that, the Kerf is not what cuts the rubber strip but the combination of blade thickness and kerf which determines the offset. This means you can use blades with different kerfs but they do not re cut the rubber strip. Diagram below shows the calculations.

View attachment 140705

I am knew to plunge saws but this does not make sense to me.

The teeth in the kerf do cut the rubber strip. If you ground off the teeth and just had a toothless blade then the kerf would be the blade width (a flat toothless blade would not cut much but that is a different story.)

Your diagram ignores the fact that the blade and hence the teeth/kerf rotate. The teeth run down and up the side of the splinter guard/ rubber strip as the blade rotates. If you move the centre line of the blade and kerf over 0.3mm the teeth will be 0.3mm into the splinter guard so you will re-trim it.

 

[Spectric]

We know the blade rotates so we just look at a single stationary tooth because all the others will unless the blade is deformed follow this one.

The cutting edge of the blade is determined by the thickness of the actual blade and the width of the teeth attached, so for a given Kerf the thicker the blade then the greater the offset and the less will be cut from the rubber strip.

As an example I use Makita blades and the B-09260 is 1.6mm thick with a 2.2mm Kerf and has an offset of 0.3mm, the B-09232 is 1mm thick with a 1.6mm Kerf but again has a 0.3mm offset so using either blade has not effect on my rubber strip.

 

[TheTiddles]

What a lot of words for the answer… no

 

[Spectric]

Often understanding why is much better than just knowing!

 

[johna.clements]

We know the blade rotates so we just look at a single stationary tooth because all the others will unless the blade is deformed follow this one.

The cutting edge of the blade is determined by the thickness of the actual blade and the width of the teeth attached, so for a given Kerf the thicker the blade then the greater the offset and the less will be cut from the rubber strip.

As an example I use Makita blades and the B-09260 is 1.6mm thick with a 2.2mm Kerf and has an offset of 0.3mm, the B-09232 is 1mm thick with a 1.6mm Kerf but again has a 0.3mm offset so using either blade has not effect on my rubber strip.

I now understand what you were trying to say. I would have said that;

The difference between blade width and kerf width must be constant to maintain the distance to the splinter guard (assuming that they are no packers that change and they are both on the same center line ~ don't know if any blades do have offsets within in them don't think it would be a good idea)

 

[Herr Nilsson]

@mattsutton29
Not sure if you have the Mafell MT55cc, but I found a very good value alternative to the stock 48T blade (Mafell 163x1.8x20 092584 Z48) from TREND - part of a range called ‘CRAFTPRO Sawblades’: CSB/16248 (Tungsten Carbide Tipped). The 48 teeth are ‘alternate top bevel’, dimensions are:-
D:162mm;
Blade:1.2mm;
Kerf:1.8mm;
Bore: 20mm.

It’s a perfect match/fit for the MT55cc!

Although you might be referring to the Z56 blade, which I have not forked out for - still bankrupt from buying the MT55cc and the DDF40!

Might be useful nonetheless.

FYI, I also run the Z12 Festool Panther rip blade, which has the exact same dimensions: 160x1.8(kerf)x20, with the blade thickness being 1.2mm too. Shop around and you can get a good deal on this one. NOTE: There are at least two Panther variants AFAIK, I have the one that’s meant for “TS 55F / TSC 55K / HK (C) 55” - as written on the blade.

 

[mattsutton29]

Thanks yes I have the MT55