Small job - riving knives

[critterjg]

Hi all

This is my first post in the metalwork section so apologies if this is the wrong area. I would like two riving knives made for my table saw as I am currently experiencing a few issues with the one I have (and don't currently have a thin kerf riving knife anyway). I am willing to pay for each (please let me know what you think is fair) and also happy to send a trace of the riving knife via post to you (photo with scale as attached). I am after the following:

1 x 2.5mm thick riving knife
1 x 1.5 mm thick riving knife

Any help would be greatly appreciated as I would like to use my table saw, but am currently nothing but frustrated! Please PM what you think is fair for the work (I have no idea) if you are interested and I'll proceed from there.

Cheers

James

[danielhobby]

hi mate,first thoughts are go to a laser cutters and get a quote for the two thicknesses,shouldnt be a great deal.keep the program and you can get them cut in mild steel,ssteel,brass alli and in any thickness you want.my cutter in melb would probably do it for around30 to 40 dollars for me.

[China]

Thats cheap in SA it would cost $50.00+ just to set up the program then the cutting cost would be added

[critterjg]

hi mate,first thoughts are go to a laser cutters and get a quote for the two thicknesses,shouldnt be a great deal.keep the program and you can get them cut in mild steel,ssteel,brass alli and in any thickness you want.my cutter in melb would probably do it for around30 to 40 dollars for me.

Thank you for the suggestion. I have sent a quote request to two companies and will see what they come back with. For reference is that price for both or each?

Thanks

James

[RayG]

Hi James,

The only critical dimensions I imagine would be the thickness, and the arc that follows the saw blade. If that's the case, why not just hacksaw or grind and file it out of some sheet stock.

Do you have a preference for material, mild steel, aluminium, brass?

Regards
Ray

[critterjg]

Hi Ray

It is all a matter of expediency for me right now. I probably could go and do that, but I would have to invest more time than what it is worth to source the steel, buy the files to then file down the knives without a way to clamp it as I need the saw working properly to build my bench!

The DIY path is what I will go down should this fail; however I'd prefer the quicker and more precise option albeit at a higher cost. I am looking at steel as the material for this as I don't trust aluminium and brass to hold up to the task at that thickness (please advise if that is incorrect).

Cheers

James

[RayG]

Hi Ray

<snip> I need the saw working properly to build my bench!
<snip>
Cheers

James

Hi James,

I see the dilemma...:)

Can you trace out accurately the shape, put dimensions on it, and scan it, then send it (PM) to me, I'll have a go at it for you tomorrow. Steel is the best choice, it will withstand side loads better.

Regards
Ray

[Geoff Dean]

How thick should the riving knife be in relation to the blade it is behind. If the blade is 2.0mm with the teeth 2.25mm thick what should the riving knife be.

To thick and it jams and too thin and the back of the blade could start binding on the wood.

I need to make a knife to go with a thin kerf ripping blade I have.

[Greg Q]

The riving knife does need to be of steel, and preferably spring steel. Any tendency for the saw to kickback can only be countered by the knife, and it needs to have resistance to being bent or twisted.

While I almost always take a DIY approach to life, I'm wondering if your saw dealer offers knives in the correct thickness for narrow kerf blades?

Greg

[QC Inspector]

For what it's worth I have a SawStop saw and the riving knife that comes with it is 2.0 mm and if I remember correctly the original blade was a touch under 1/8" (3.0 mm). I have a Forrest standard blade in it that is .125 (3.2 mm) and also their thin kerf blade of about .093 (2.36 mm). Both work with the 2 mm knife but I can't say if it is the optimum for both blades. Maybe some digging in the European regulations would give better info as they are very strict about such things.

Pete

[BRADFORD]

I made a thin riving knife out of an old saw blade, the type without the TC tips, I think it is about 2mm thick, anyway it has been on the saw for years and works a treat.

[Greg Q]

I made a thin riving knife out of an old saw blade, the type without the TC tips, I think it is about 2mm thick, anyway it has been on the saw for years and works a treat.

Now that there is a great idea!:2tsup::2tsup:

[critterjg]

Thanks all for the replies. I've done a little bit of reading (no regulation, just forums) about it and it does not appear a hard and fast rule the riving knife should be exactly the width or a hair under, which is why I have chosen 2.5mm and 1.5mm. My Freud blade is stated as 1/8" (3.175mm), however is actually 0.118 (2.997mm). That spare 0.178mm is less than the clearance on my original riving knife at a thickness of 3.1mm. After a significant amount of frustration I found out where the problem was and arrived at the requirement for a more forgiving riving knife.

Ray, having just come on now I will draw the specs up. Do you use SketchUp?

Cheers

James

[RayG]

Hi James,

Sketchup is fine. I think you can post the files as attachments here. If not PM them to me.

Regards
Ray

[critterjg]

Hi James,

Sketchup is fine. I think you can post the files as attachments here. If not PM them to me.

Regards
Ray

Ray

As mentioned here are the dimensions. The inner radius has a slight 20 degree bevel on each side, however I would be able to grind that with my fake Dremel. Ideal material is high carbon steel, however I'm sure mild steel will do the job fine! Please PM me price per knife inc. postage. If I have missed any dimensions please let me know or open up the attached SketchUp file.

Cheers

James

[RayG]

Hi James,

Drawings are all good, I'll PM you tomorrow with the details, I think the local saw repair place might have some reject circular saw blades, and as Bradford suggested earlier that would be perfect material.

Regards
Ray

[RayG]

Hi James,

I got one finished, the other one will have to wait for a couple of days, I've got some on-site work to do.

For anyone interested in making a riving knife, here are a few pictures.

Old 14" saw blade from the local saw sharpening place, no charge, if you ask nicely they will be happy to give you an old blade, just watch out for cracks and warps, this one was nice and straight and only a few minor cracks close to the teeth, which was most likely why it was scrapped. Thickness 100 thou ( pretty close to 2.5mm :) )

http://www.backsaw.net/pics/Misc/DSCN0535.JPG

Make paper template. and figure out where to do the rough cuts

http://www.backsaw.net/pics/Misc/DSCN0537.JPG

Stick paper template in place for initial shaping
http://www.backsaw.net/pics/Misc/DSCN0538.JPG

Rough out the shape with angle grinder and thin cut off wheel, the slot for the mounting bolt was filed by hand, and then the edges finished off on the linisher. I started forming the bevel, but James can finish that to suit his setup. (I don't think its critical, so long as the riving knife enters the kerf cleanly.

Here is the finished part, after surface grinding, finished size 97 thou..

http://www.backsaw.net/pics/Misc/DSCN0541.JPG

http://www.backsaw.net/pics/Misc/DSCN0542.JPG

Regards
Ray

[Stustoys]

Looks great Ray.
Whats that you're using to measure the blade thickness?(and does BT have one:D)

Stuart

[RayG]

Whats that you're using to measure the blade thickness?(and does BT have one)

Hi Stuart,

I've got my fingers crossed, BT doesn't have one, but I wouldn't be surprised...

http://www.backsaw.net/pics/Misc/DSCN0543.JPG


It was a pickup from Denman Robinson, spring loaded, measures up to 1/4" and up to 2 1/2 inches depth. No brand that I can see, and the label inside the box is mostly missing. It's the perfect thing for measuring saw plate thickness.

Regards
Ray

[critterjg]

Hi James,

I got one finished, the other one will have to wait for a couple of days, I've got some on-site work to do.

For anyone interested in making a riving knife, here are a few pictures.

Old 14" saw blade from the local saw sharpening place, no charge, if you ask nicely they will be happy to give you an old blade, just watch out for cracks and warps, this one was nice and straight and only a few minor cracks close to the teeth, which was most likely why it was scrapped. Thickness 100 thou ( pretty close to 2.5mm :) )

http://www.backsaw.net/pics/Misc/DSCN0535.JPG

Make paper template. and figure out where to do the rough cuts

http://www.backsaw.net/pics/Misc/DSCN0537.JPG

Stick paper template in place for initial shaping
http://www.backsaw.net/pics/Misc/DSCN0538.JPG

Rough out the shape with angle grinder and thin cut off wheel, the slot for the mounting bolt was filed by hand, and then the edges finished off on the linisher. I started forming the bevel, but James can finish that to suit his setup. (I don't think its critical, so long as the riving knife enters the kerf cleanly.

Here is the finished part, after surface grinding, finished size 97 thou..

http://www.backsaw.net/pics/Misc/DSCN0541.JPG

http://www.backsaw.net/pics/Misc/DSCN0542.JPG

Regards
Ray

Ray

It looks superb! Thanks again and obviously no worries about the wait!

Cheers

James

[Stustoys]

Certainly a neat piece of kit Ray.
Thanks
Stuart

[BRADFORD]

Nice job.
Mine didn't come out as neat as that