Kity 619 Riving Knife

[CaptainBarnacles]

I have just bought a Kity 619. It's over ten years old so it's one of the original French made ones (if that makes any difference!?) but it's missing it's riving knife. I called NMA who were incredibly knowledgable and helpful however they wanted almost £60 for a replacement riving knife.

I'm not much of a metalworker but if there's a chance to save £60 I'll have a go at trying to make my own riving knife. To save me a lot of time (and swearing etc) does anyone have a 619 that they could remove the riving knife from and draw around it to make a template for me? As long as one or two dimensions are included I should be able to scale it from a scanned or photographed image.

Thanks,
PJ.

 

[Steve Maskery]

Can't help you with a template, but making your own is not difficult, just make sure you choose a suitable material. Mild steel is no good, you'll never keep it flat.
Gauge plate is a good choice and is easy to cut and drill as long as you don't let it get hot, otherwise it will harden. On a similar thread recently someone was going to make is t from an old CS blade. I don't know how he went on with it, but it's a thought.
Good luck
Steve

 

[marcros]

when the 618 arrives, i can photocopy it for you, although it will be next week.

 

[CaptainBarnacles]

Can't help you with a template, but making your own is not difficult, just make sure you choose a suitable material. Mild steel is no good, you'll never keep it flat.
Gauge plate is a good choice and is easy to cut and drill as long as you don't let it get hot, otherwise it will harden. On a similar thread recently someone was going to make is t from an old CC blade. I don't know how he went on with it, but it's a thought.
Good luck
Steve

Thanks for the info Steve. I have a couple of old blades lying around so I may well give that a try. I had considered making one from some 3mm aluminium plate that I have but I'm not sure if it's up to the job.

when the 618 arrives, i can photocopy it for you, although it will be next week.

That would be great - many thanks.

 

[marcros]

i dont think Aluminium is much good for riving knives. what thickness is your blade kerf and plate?

 

[Steve Maskery]

No, not ali. You need something stiff.
S

 

[CaptainBarnacles]

i dont think Aluminium is much good for riving knives. what thickness is your blade kerf and plate?

I have a few blades with the thickest being 3mm kerf / 2.15 plate and the thinnest at 2.5mm kerf / 1.8mm plate.

Is it worth making two riving knives, one for thin kerf and one for standard blades?

 

[Steve Maskery]

Not only is it worth it, it is essential that you do.
If you use a standard RK with a TK blade, your workpiece will jam on the RK. Conversely, if you use a TK RK with a standard blade, it will not protect you from kickbacks, which is its primary purpose.
S

 

[MickCheese]

Ok Steve, I know I'm going to kick myself for asking this but I have wracked my brains and cannot fathom out what a CC blade is?

I know you are going to make me regret asking as it's going to be obvious but I have broad shoulders.

My first thought was circular saw but that's CS.

So here goes.

Mick

 

[Steve Maskery]

CC is a technical term also known a "typo written when one is not wearing one's contact lenses".
You could also use a CS blade or a TS as a substitute if you can't find a CC blade.
S

 

[CaptainBarnacles]

:lol: I had interpreted CC blade as cross cut blade :lol:

I couldn't work out why a rip blade wouldn't work just as well though :wink:

OK, so it looks like I have a fair bit of metal butchering ahead of me if I have to make two riving knives. Obviously the easy way is to go and spend a grand or two on a plasma cutter but in the interest of saving money do you think I should hack out the rough shape with a 4.5" grinder then set to with the files etc? If there's a more effective/efficient way I am all ears because at this point the only thing stopping me ringing up and ordering one from NMA tomorrow is Mrs Barnacles. As much as I like spending time in the workshop I am not ready to sleep in there as well.

So to summarise: I'll be making a TKRK and a SKRK from an old TS/CS/CC blade or calling NMA whilst dodging SWMBO for fear of being in DS! Sound about right? :?

 

[Steve Maskery]

Spot on!
I've not use saw blade as a base material myself, but I have used gauge plate, and whist it is a good workout it is not actually difficult (unless you let it get hot in which case it just hardens and then you are back in the DS).
S

 

[ossieosborne]

CaptainBarnacles - Do you have a 270mm blade on your machine? My saw was fitted with a 250mm blade when I bought it (secondhand) and I had to re-profile the riving knife to fit the (correct size) larger blade.

Oz

 

[Myfordman]

i dont think Aluminium is much good for riving knives. what thickness is your blade kerf and plate?

I have a few blades with the thickest being 3mm kerf / 2.15 plate and the thinnest at 2.5mm kerf / 1.8mm plate.

Is it worth making two riving knives, one for thin kerf and one for standard blades?

Far be it from me to contradict Steve M a man who I very much respect!
However, with the blade dimensions quoted, a RK made from 2.2 to 2.4 mm steel ought to cover the range of blades?

3/32" gauge plate ought to be just right according to my reckoning.

Machining that I have done on sawbade plates to open up the bore for example, has shown this steel to be very tough indeed requiring tungsten tipped lathe tools and the swarf coming off blue. For this reason, I would not suggest this as a source of material.

https://www.cromwell.co.uk/CTL4130322Z 3" wide

or
https://www.cromwell.co.uk/CTL4130326C 4" wide

MM

 

[rafezetter]

Although smaller, I had to remake a riving knife for my old circular saw (as I'd binned it years ago as it kept catching when I used it normally) when I bolted it to a bit of wood upside down as a makeshift TS.

I used an old SK blade from the same saw with a few chipped teeth from an unseen nail. I roughed out a shape, cut it pretty close with an angle grinder and fettled with a file. It fit pretty good and did what I needed, it's stayed flat and true so far.

I'm sure it can be done better, but this is just my take on it.

 

[Steve Maskery]

Far be it from me to contradict Steve M

Hey Bob, you are far more of an engineer than I am, so no problem on this. Are you saying that it is perfectly possible to have a RK that is is thinner than the kerf of a TK blade but thicker than the plate of a standard blade? If it is, then we are at one, I just didn't realise that was feasible, from a home engineering point of view.

BTW I did film the making of a replacement RK for one of my DVDs. Unfortunately the tape was faulty and the footage was unusable, and I had to vacate my workshop before I could re-shoot, so it didn't appear in the finished film. I might make a YouTube Short one day as I think many people would find it constructive.

S

 

[Myfordman]

Far be it from me to contradict Steve M

Hey Bob, you are far more of an engineer than I am, so no problem on this. Are you saying that it is perfectly possible to have a RK that is is thinner than the kerf of a TK blade but thicker than the plate of a standard blade? If it is, then we are at one, I just didn't realise that was feasible, from a home engineering point of view.

BTW I did film the making of a replacement RK for one of my DVDs. Unfortunately the tape was faulty and the footage was unusual, and I had to vacate my workshop before I could re-shoot, so it didn't appear in the finished film. I might make a YouTube Short one day as I think many people would find it constructive.

S

I was simply looking at the dimensions given.
3/32" is smaller than the narrowest quoted kerf and wider than than the thickest plate so by my reckoning one RK will do both jobs - obviously with a shim fitted to keep it centred on each blade.

I've sure that a video would inspire confidence in those needing RKs

 

[MickCheese]

CC is a technical term also known a "typo written when one is not wearing one's contact lenses".
You could also use a CS blade or a TS as a substitute if you can't find a CC blade.
S

Fantastic

Made me laugh out loud, wife thinks I've gone mad.

Mick

 

[CaptainBarnacles]

CaptainBarnacles - Do you have a 270mm blade on your machine? My saw was fitted with a 250mm blade when I bought it (secondhand) and I had to re-profile the riving knife to fit the (correct size) larger blade.

Oz

I have both. I have a 270mm ripping blade and various other blades, all of which are 250mm. My previous table saw had a RK that was adjustable for different blade diameters by having an elongated mounting hole it allowed the angle and position of the knife to be adjusted to suit the blade. I gather that can't really be done with the Kity as the knife is fixed into a sort of slot.

I imagine I am about to liberate more worms from the comfort of their tin can but; how close to the blade should the knife be? If I made a knife that was profiled for the larger blade would it still be possible to use it with the smaller blades despite the 10mm-ish gap, or is that too far away from the blade?

Far be it from me to contradict Steve M a man who I very much respect!
However, with the blade dimensions quoted, a RK made from 2.2 to 2.4 mm steel ought to cover the range of blades?

3/32" gauge plate ought to be just right according to my reckoning.

Machining that I have done on sawbade plates to open up the bore for example, has shown this steel to be very tough indeed requiring tungsten tipped lathe tools and the swarf coming off blue. For this reason, I would not suggest this as a source of material.

https://www.cromwell.co.uk/CTL4130322Z 3" wide

or
https://www.cromwell.co.uk/CTL4130326C 4" wide

MM

Many thanks for the info and the links MM. Looks like gauge plate would be the sensible way to go. Once I have made the knife would it be an idea to heat treat it? I just read "Relatively soft and easy to machine. High wear resistance after heat treatment." on Cromwell's site - does "relatively soft" refer to a comparison with something like silicon carbide or something more common-place like stainless?

Am I thinking too much? :?

 

[Myfordman]

Leave in the state it is supplied. Hardening in this context would be to make it into a cutting tool and potentially brittle if you did not get the tempering right. It will be more than tough enough for woodworking use in this application.

MM