Riving knife height?

**Timless Timber** · 31st August 2013, 04:43 PM

Robland X31 table saw riving knife height?.

I wanted to house out a simple lap joint, using the saw blade lowered to half the timber thickness, as I've done for many years on various table & panel saws. The Robland manual says specifically not to do this...(heck knows why - I've done it for more than 20 years without incident and my father for 50 years+ before that). To do so, I had to remove the riving knife - because it sits ever so fractionally higher than the blade and prevents running the timber over the top of the saw blade without lifting it off the table to clear the riving knife, and thus altering (reducing) the depth of the housing out cuts.

In removing the riving knife, I noticed - that the slot it sits down into is curved to match the blade diameter and arc... so that at any height the clearance space to the teeth remains constant.

The bottom of the riving knife slot, is a half round (i.e probably a 1/2" drill hole or similar) to sit down onto the securing bolt as it's mechanical "stop point" of downward adjustment.

What I am wondering - to prevent me having to remove and replace the riving knife a zillion times...(coz I realize from experience that it's important to have it in place when ripping timber and sheet material to avoid the timber stresses causing the gap to close on the back of the saw blade and result in lifting and throwing the timber or sheet forward with some force...)... is there ANY sound safety or operational reason, that anyone can foresee, or has experienced, for me NOT, to drill another hole (with my drill press) the same diameter maybe half a hole width distance further down the steel riving knife slot (or less), in a continuation of the same arc, that would allow me to drop the adjustment height of the riving knife ever so slightly, (maybe 2 or 3 mm) further down - so that it remains the same set back distance from the blade teeth BUT it sits ever so fractionally lower than the top arc of the blade teeth, such that I CAN house out simple half lap and rebate joints, over the top of the blade, without having to remove & replace the riving knife a zillion times?

Why Robland don't put them out standard like this, beats me. (Similarly why they suggest in the manual not to perform this action similarly flummoxes me, to be frank).

Sure, I could use a router & jig for it - but for one simple joint - it's a LOT of trouble to go too... when a minute or so on the saw achieves the same outcome.

Curious to hear what others think...suggest or if everyone's already done it and I am just "tail end Charlie".

Please spare me the well intentioned "safety lectures"... I still have all ten toes & fingers after more than 20 years now of saw milling, and cabinet, joinery, furniture making, and using all manner of wood working equipment..... so I've been operating this way for a long time, (with and without riving knives) as has my father before me.

It just seems like a very simple suggested modification - that could potentially benefit a LOT of Robland users maybe? I am wondering if anyone's done this before me, and how it's worked out?.

Many thanks in advance gentlemen.

**rustynail** · 31st August 2013, 06:33 PM

I extended the half hole at the base of the knife to allow the top of the rive to be below the teeth but high of the gullets. I hate removing the knife for safety reasons and its a pain taking it on and off all the time. I guess that's why so many people dont use one now that guards are often mounted elsewhere. Personally, I dont use a table saw without a rive, particularly one with a bit of grunt.

**AlexS** · 31st August 2013, 07:54 PM

No reason at all not to extend the slot so the knife sits just below the top of the blade. That's the way it should be.

**Timless Timber** · 31st August 2013, 09:38 PM

Thanks heaps guys - looks like I have me a little project for tonight then!

Between tips and gullets sounds good to me.

Has been a big, but productive day!.

Cheers

**Chief Tiff** · 31st August 2013, 10:51 PM

I don't know that I'd take it down quite as far as the gullet; what if you choose to fit a finer pitched blade later?

2-4mm maybe

?

I like riving knives too, I wish my Tritons had been fitted with them. It pi**es my off that they had to be fitted by law to be sold in the EU but for the domestic market they chose to save a few cents and not bother. I would have liked to have had the option.... Maybe now that they're European owned they fit them for every market?

**chambezio** · 31st August 2013, 11:28 PM

When I started work in the white cabinet making sector (kitchens and wardrobes and stuff) it wasn't long before we lowered the riving knife to be a couple of mm below the top of the blade. As the riving knife and the rise and lower system of the blade were one and the same it was a way to save your self a lot of time without having to remove completely the riving knife.

When I bought my second hand SCM it never had a riving knife at all. Who ever had been using it before me regarded the riving knife as superfluous to proceedings. It was one of the jobs I did after I got the saw home and set up. I used a milling cutter in the drill press and cut the arc using a pivot. Bit hard to describe but it worked a treat. And no I would not use a bench saw without a riving knife. It is one safety feature that should be used!!

**pjt** · 1st September 2013, 12:34 AM

I have drilled an extra hole then filed to shape to lengthen the slot in my riving knife, from memory I did that for 10" blades, I had the same issue as TT, no issues thus far.

Pete

**rustynail** · 1st September 2013, 12:41 AM

Originally Posted by Chief Tiff

I don't know that I'd take it down quite as far as the gullet; what if you choose to fit a finer pitched blade later?

2-4mm maybe

?

I like riving knives too, I wish my Tritons had been fitted with them. It pi**es my off that they had to be fitted by law to be sold in the EU but for the domestic market they chose to save a few cents and not bother. I would have liked to have had the option.... Maybe now that they're European owned they fit them for every market?

If you change blade pitch you raise the knife to suit the blade. Half way between tip of tooth and bottom of gullet works well as a saw blade should be set to have the bottoms of the gullets just clearing the top surface of the timber being cut. This then has the greatest number of teeth in the timber at any given time and allows the gullets to clear the dust, which makes for better cutting efficiency.

**Timless Timber** · 14th September 2013, 06:50 PM

Well it took me a while to get "a round tuit" - but today with the incessant rain and no chance to do anything outside, I spent a while in the shed doing the riving knife mod.

Wasn't as easy as I thought - the slot wasn't curved, it was straight, which means as you lower it - the gap between the blade and teeth closes.

So, I had to scribe it for clearance, and grind away enough to allow me to lower it to just below teeth height. Took a few goes at it...but it fits and clears the teeth fine and now I can house out without taking it off any more.

As it's fitted to the rise & fall mechanism it stays with the blade thru its travel up and down...meaning it stays adjusted.
Altogether a worthwhile exercise IMHO.
Why on earth they do not come standard that way? No idea...

Could have been worse - I COULD have spent the time sweeping the floor!

I badly need to keep organizing my space up there in the shed. Nuts, screws, washers, bolts, & split pins, etc all over the place - no organizational system at all - tools all over in any available spot.

Just won't do at all...

Materials storage? whats that?

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