What saw to saw a saw?

[Essex Barn Workshop]

I recently bought a Startrite TA255 but it came without a riving knife, so decided to have a go at making my own from one of the many old blades that it did come with.

Not the prettiest or best, but all I had to cut it with was an angle grinder. It works, which is really the only test that matters, but is there a jig saw blade or scroll saw blade that could cut a table saw blade so I could try again and make a neater job of it?

Thanks.

 

[Phil Pascoe]

You could tidy it up with a fairly coarse flap wheel.

 

[AES]

I don't know what sort of steel such saw blades are made of, but at a GUESS, I'd say some sort of hardened & tempered tool steel. In which case I DOUBT any scroll saw blade (or jig saw blade) would last long very long at all when trying to cut that.

The angle grinder plus Phil Pascoe's suggestion of flap wheel clean up sounds "good" to me.

If you want a "neater/easier to handle" initial cut, then a small cut-off disc in a Dremel-type tool would be my go to, but again if the saw blade is as hard/tough as I suspect, then I'd also expect to get through at least a couple of the Dremel-type cut off discs. But at least those cut-off discs are not too expensive (relatively speaking!) and the Dremel-type tool is smaller/lighter/easier to handle than the average angle grinder, especially on tight curves.

 

[Bingy man]

personally I’d be looking at a plasma cutter if you have access to one . You might get lucky if you have any metal fabrication firms near to where you live and you ask nicely..

 

[Inspector]

To use an angle grinder on the inside curve of the riving knife mark the saw blade. Lay the grinder blade off vertical such that the perimeter of the blade can follow the arc, maybe 45º. You are aiming for a groove that resembles a laid over L where the short leg of the L is following the marked line and is closer to vertical. Go about half way through and then flip the riving knife over to do the other half. Don't press hard on the cutting disc, let it cut at its own pace. It wears one side of the cutting disc more than the other so flip the disc over to even up the wear. When the cut is done you can clean up the arc. Easier to do than explain. What you have now more closely resembles a splitter rather than a riving knife which matches the circumference of the blade. You are close to being there, just need a little more practice with the angle grinder.

Ideally a plasma, laser, water jet cutter would be easier but most people with one want to make money and for one or two it would get spendy.

Pete

 

[Distinterior]

I made a riving knife for a Startrite saw recently and also used an old saw blade as the source for the metal......I did have the advantage of having an original riving knife to use as a template though.
Saw blade plate material is a bit harder to work with than normal mild steel, but I only used an angle grinder to do the bulk of the cutting.
I think the discs I used were 1.0 or 1.5mm thick....
(Worn down diameter discs work well as they help in cutting slightly tighter curves than the 115mm diameter originals)
Final detail and finishing was done on a 300mm sanding disc and a couple of decent hand files before blackening.

Original on the right and copy on the left....

 

[Cabinetman]

Ideally the riving knife should be curved to follow the curve of the blade, with a minimum gap of 8mm and no closer than 3mm. But well done I bet it wasn’t easy cutting that old saw blade!

 

[Yojevol]

Your blade material looks too thin
The aim of the riving knife is to keep the kerf riven so that the workpiece doesn't close up and get caught on the back teeth. The knife, therefore, needs to be the same thickness as the teeth.
Brian

 

[mccpe]

Your blade material looks too thin
The aim of the riving knife is to keep the kerf riven so that the workpiece doesn't close up and get caught on the back teeth. The knife, therefore, needs to be the same thickness as the teeth.
Brian

Not so. The riving knife should be thinner than the width of the teeth, but preferably wider than the saw blade plate.

 

[Distinterior]

.......The riving knife should be thinner than the width of the teeth, but preferably wider than the saw blade plate.

Agreed!
Just use a Vernier to measure the thickness of the material you want to use to check that its thicker than the blade plate, but narrower than the kerf of the blade in the saw.

 

[Essex Barn Workshop]

Not so. The riving knife should be thinner than the width of the teeth, but preferably wider than the saw blade plate.

Yes this is what I thought, so that led me to choose the blade to cut from as it fitted this formula.

 

[Essex Barn Workshop]

I made a riving knife for a Startrite saw recently and also used an old saw blade as the source for the metal......I did have the advantage of having an original riving knife to use as a template though.
Saw blade plate material is a bit harder to work with than normal mild steel, but I only used an angle grinder to do the bulk of the cutting.
I think the discs I used were 1.0 or 1.5mm thick....
(Worn down diameter discs work well as they help in cutting slightly tighter curves than the 115mm diameter originals)
Final detail and finishing was done on a 300mm sanding disc and a couple of decent hand files before blackening.

Original on the right and copy on the left....

View attachment 176807

These are wonderful and put mine to shame! Can I ask the purpose of the cut outs on top of the knife, are they for the blade safety cover? I don't have one of those either!

 

[Lampost46]

Recently i needed to replace my riving knife of my AW264 table saw as i had modified the original to enable me to cut slots in some sheet material. The supplied original was too high. I therefore reduced the originals height. At the same time so ordered a replacement. hence i know they do the replacements
Judging from the fixing in your photo the Axminster replacement riving knife for the " AW254TS 254MM TABLE SAW may well be a solution
"

 

[Yojevol]

Not so. The riving knife should be thinner than the width of the teeth, but preferably wider than the saw blade plate.

What's the theory behind that?
The only thing I can think of is that it allows for some thinning of the teeth on sharpening

 

[Distinterior]

....Can I ask the purpose of the cut outs on top of the knife, are they for the blade safety cover? I don't have one of those either!

Yes, the small slot at the back is for a horizontal pin and the larger cutout is for the clamping bolt/lever, allowing for easy removal & refitting.

This is what they look like when fitted on a Startrite.....early ones were red and later ones were yellow!

 

[Distinterior]

What's the theory behind that?
The only thing I can think of is that it allows for some thinning of the teeth on sharpening

It's all to do with preventing possible kickback......Say your saws blade has a 2.4mm Kerf and the blades plate is 1.8mm. Your riving knife would ideally be about 2.0/2.2 mm thick.
The idea being, that any wood getting cut cant move over into the teeth of the blade any further than the edge of the riving knife, thus preventing it from kicking back.

When a saw blade is sharpened, there is an absolute minimum of material removed from the overall kerf width of the blade, and it's not an issue.

 

[Agent_zed]

What's the theory behind that?
The only thing I can think of is that it allows for some thinning of the teeth on sharpening

Mostly a guess but my take on it is a few factors come into play.

1. There is some variation in blades so if I have a riving knife that is exactly 2.4mm and a blade with exactly 2.4mm then all good. But if I change brand and the new blade is 2.37mm my riving knife is now bigger than the kerf so is going to possibly create friction.

2. Your riving knife will have to be 100% in line with your blade. 0.2-0.4mm is not a lot of space but might just be enough to account for a very slight deviation or bend. Even a layer of rust or sap on an exact matching size riving knife is going to cause it to be bigger than the kerf.

3. Blades will wear so will become smaller. Riving knives are unlikely to sustain as much wear.

4. Wood expands slightly as it is cut as the pressure are taken off the fibres and/or the heat generated in the cut.


I wonder if a riving knife that is tapered would be a good idea as it would still prevent the blade binding but reduce friction on the back edge?

 

[Distinterior]

I wonder if a riving knife that is tapered would be a good idea as it would still prevent the blade binding but reduce friction on the back edge?

The original Startrite riving knives have a faceted front edge on them, bringing the very front to almost a sharpish edge.
You can just see it when you zoom in on those two knives in my first picture.....

 

[HOJ]

Made one for my Laguna, needed one that was level with the blade height as I do a lot of rebating with it, all done with a 4 1/2" grinder with a thin metal cutting disc and a grinding disc.




Oh, and a drill for the 2 holes, be nice if it was blackened but I don't know how too.

 

[Distinterior]

......be nice if it was blackened but I don't know how too.

It's easy enough to do.....you can buy a small blackening kit that comes with all the relevant fluids that are required.

As long as the material you've used to make your riving knife from is made of steel ( not Stainless Steel!), it will blacken up, no problem.

I'd be happy to do it for you if you wanted to send it to me...?

Edit.
Is the steel galvanized...? If so, that would need to be removed before the blackening process!