Thread: Fitting a riving knife to hare and Forbes 12 inch table saws

I wondered about this a while ago and it appeared the design differences between a saw designed for a splitter and that for a riving knife made a conversion problematic.

General in Canada provide a kit for one of their saws #650RNK and it's interesting looking at the installation guide, but the price also seemed pretty steep New retro-fit kits let you add riving knife to some General tablesaws - Fine Woodworking

I have seen the advert for BORk, and itm look pretty complicated, but the one from general was a cracker.. The BORK one had to handle too many varients so was complex.

I approached H&F but the answer was obvious. Buy a new saw.. probably cheaper in the long run.. But I will give it a bash and see what i can come up with.

I've got an old 12 inch contractor saw without a riving knife. As an engineer i couldn't help myself and came up with four mechanisms for different designs for to solve this issue. None were like the bork version mentioned earlier.

Unless you intend doing a proper knife as a challenge and have access to a good tool shop I'd recommend taking the easy way out and making your own zero clearance insert with a micro splitter made of a folded 20 mm wide piece of steel plate screwed to the underside of the throat plate. Make several for differing ranges of blade protrusion and you're done.

Four designs I did draw up are:

1. Linear slide
2. Parallelogram
3. Single component linear approximate
4. geared mechanism similar to the laguna platinum system.

All only worked with a 250 mm blade, as I used the space behind for the knife.

Linear slide has the most expensive components. There's a well fabricated one on the net, but I believe it can be dumbed down a bit.

Parallelogram is an obvious solution. I think one of the home made table saws on woodgears.ca had a variant on this.

I was going to build the approximate one as it is pretty simple with one degree of freedom and built with only a few parts. The tradeoff for simplicity is the clearance to the blade changes by a few mm for a 250 mm blade through the range of height adjustment. You set the riving knife to move along a path parallel to the tangent of the arbour radius with the blade set at mid height. I've not seen anything on the net resembling this mechanism.

The most elegant and compact is the geared design, but this is a pain to fabricate without some expensive gear. Download the platinum table saw for an exploded view of this style of mechanism.

As I said above I wouldn't take on the challenge, but I can dig up my sketches if you would like a copy. If you really want a knife, I personally would buy a saw that has one. (And I did in the end.)

--
zzpanic

This is the linear slide example I was talking about:

Cleanup and riving knife on Delta 36-650 contractor saw - MANY pictures

This is the parallelogram mechanism.

Hector Acevedo's homemade table saw

Laguna manual:

Platinum Series Tablesaw w/ Dovetail Mech Left-tilt

I'm a a bit bemused by this post.
I have spent many hours tracking down and buying and then reselling the old Wadkin, Wolfenden and even Hyco small table saws.
These being English designs or Oz copies of same.
Although all these saws are a descendent of the 30s Delta uni saw the Poms included a riving knife in their design from the start.
The yanks never did although some did make a splitter available.
The Tiawanese of course after the big market copied the yank design and the locals scare and fords and carba crap imported these dangerous bits of junk into Oz. They then switched to China for an even cheaper piece of ?
If you are an engineer why not source a quality older unit and rebuild it?
A pigs ear will never be a silk purse.
Sorry about the rave but won't/don't have any of that crap in my workshop.
There is a Wadkin on gumtree at Penrith as we type for $550 and he can't get a buyer?
H.

A table saw can be used safely without a rivng knife or splitter, although it is a good bit of gear to have

I agree with man made boards but timber has built in stresses that can be very spectacular.
I was at ANU under the great guru George Ingham when a student had a knuckle shattered by a piece flung back at high speed.
George knew it all but that didn't help John he dropped out of the course soon after.
Unless you have a very knowledgeable tailer out its suicide with some stuff.
H

Sorry China but IMHO I don't think you should promote the use of a table saw without at least a spitter,there that's my 20 cents worth.

Agree, given the vast majority of people visiting the forum are amateurs, using saws without riving knives or splitters is high risk and asking for trouble.

I'm ex trade, using a cheap saw with a splitter and I am far from happy. On the odd occasion I take it off for a specific cut, I cringe despite attaching every guard and feather board I own.

Originally Posted by China

A table saw can be used safely without a rivng knife or splitter, although it is a good bit of gear to have

Whole heartedly agree with you China. One can quickly tell if timber is going to bind and take the appropriate action.

I was a benchman no1 and no2 in both pine and hardwood mills and so I have a fair idea of what can go wrong and it does not matter to me if it has a 10 12 or 40inch blade it is bloody dangerous to not have one. to say that one can tell if timber is going to bind and has time to take action is just plain being a suicide jockey and rather it be you than me. just my thoughts that is all. regards peter(grandad)

Originally Posted by rod1949

Whole heartedly agree with you China. One can quickly tell if timber is going to bind and take the appropriate action.

I have mate who's grandfather ran a mill down the south coast.They were cutting hardwood and a large sliver was flung back at him.
It went thru his guts sticking out both front and rear.
The rest of the crew promptly fainted at the sight so he had to walk to the phone and ring for help himself.
Another mate of my brother a boatbuilder was using a table saw to split a small piece of trim, he pushed it thru the saw and took hold of it at the back of the saw closing it up on the back of the blade.He lost 3 fingers.
Dodging this sort of stuff is like kissing your 'A' goodbye when they drop the big one.
Remember most of the punters on here are amateurs whether they think so or not. The number of properly time served tradesmen or even dilutys would be less than one percent.
H