Riving knife higher than the blade! - Potential Mod?

[bp122]

Thank you all for the responses, suggestions and the caution!

I have started a new job, two weeks ago, which has extremely minimal internet access for outside stuff and quite fast paced than my previous place. hence I am a little slow on the responses.

It is a shame, as my previous place had a laser cutting machine where I could have designed and get a riving knife cut out of pretty much any thickness wanted. Maybe I'll call in a favour

Since the riving knife on mine has a slot (as almost all of them do) for the adjustment bolts, I thought if I should extend the slot upwards, I'd be able to position it further down to get underneath the cutting height line of the saw blade. But no matter how much I played around with it, the curve on the RK wasn't concentric or had enough clearance with the blade curve. Hence I have to get a new knife or make (get one cut- as I don't have any metal cutting tools other than a hacksaw and a drill, not even a bench vise)

On another note, for people who have seen using cross cut sleds etc take the RK out and use a perspex guard across the sled (along the full length of the blade slit) - Is this still safe? - reason I ask is because I am building a sled myself, was wondering if it had the merit.

Thanks guys!

 

[Steve Maskery]

Perspex is not a great choice, actually, as it can shatter. You are much better off using Polycarbonate or even a thick piece of HDPE. It is soft, yes, but it doesn't shatter.

 

[SamTheJarvis]

I second using a harder steel for a riving knife if you're making your own. Mild steel will invariably end up bent and is surprisngly difficult to get adequately flat again.

 

[bp122]

I second using a harder steel for a riving knife if you're making your own. Mild steel will invariably end up bent and is surprisngly difficult to get adequately flat again.

Thanks, Sam.
Would you know of a place to buy flat hard steel? My current RK is 2.2mm thick, any thicker and the workpiece won't push through as easily. And I don't have a milling machine to bring standard thickness to my size. Any suggestions?

 

[Steve Maskery]

You can buy 2mm stock from places like Cromwell's.

 

[AJB Temple]

This kind of topic always gives me the heebie jeebies. I really think table saws are fundamentally dangerous for beginners with no training. I have seen site carpenters (who are supposedly professionals) do the most amazingly stupid things with table saws). Fiddling about with RK and guards is not great if people are not very careful with a safe and robust set up. Examples of experience on property developments:

Cutting 8 x 4 sheets on portable TS with no support
Cutting mitres with guard off and leaning over the saw to see the line
Removing RK because the wood gets stuck on it
Forcing wood through because it is binding on the blade
Dropping stuff on an unguarded spinning blade
Dispensing with inconvenient or missing push sticks
Standing right in the path of the kick back
Trying to shove tiny bits of wood through (parquet)

etc....

 

[Trainee neophyte]

This kind of topic always gives me the heebie jeebies. I really think table saws are fundamentally dangerous for beginners with no training. I have seen site carpenters (who are supposedly professionals) do the most amazingly stupid things with table saws). Fiddling about with RK and guards is not great if people are not very careful with a safe and robust set up. Examples of experience on property developments:

Cutting 8 x 4 sheets on portable TS with no support
Cutting mitres with guard off and leaning over the saw to see the line
Removing RK because the wood gets stuck on it
Forcing wood through because it is binding on the blade
Dropping stuff on an unguarded spinning blade
Dispensing with inconvenient or missing push sticks
Standing right in the path of the kick back
Trying to shove tiny bits of wood through (parquet)

etc....

I

I am pleased to say that I only managed one on your list - dropping a piece of wood on the blade - I won't be doing that again!

However, I do cut rebates on the saw, and to do that I have to remove both guard and riving knife. Could someone correct my ignorance if necessary, but I was under the impression that a riving knife serves no useful purpose in a rebate, because the wood is a single solid piece, so nothing is going to move and bind on the blade. All my knowledge is from here, or YouTube, and this little nugget is definitely of YouTube provenance, so a definitive ruling would be nice.

Thanking you in anticipation...

 

[Steve Maskery]

A rebate involves TWO cuts...

 

[doctor Bob]

A rebate involves TWO cuts...

Well that depends .............. i could do a rebate 4mm wide with one cut ..........

 

[MusicMan]

That's true for a small rebate, but if using two cuts, as Steve implied, there is a possibility of binding on the second one.

 

[Steve Maskery]

A rebate involves TWO cuts...

Well that depends .............. i could do a rebate 4mm wide with one cut ..........

Yes, that is fair enough.
And I could do a rebate up to 3/4" in one pass because I have a dado head, so nah, nah, na-na, nah!

But I'm sure you take my point.

The fact is that there is an increased chance of kick-back with a two-cut rebate, even with a short fence, than there is with an ordinary rip cut.

For anyone who is still in the dark about it all, there is always YouTube

Yes, yes, I know. The videography is very dated, but it was a long time ago. The content is still relevant.

 

[RobinBHM]

Ive spent the last 20 years using an industrial panel saw with an overhead guard - the guard is mounted on 70mm square hollow section steel so it is proper solid.

I have to be honest the guard is almost never adjusted for height :shock: , but any small work is done with 1 or 2 push sticks -always.

I dont see a cut down riving knife as dangerous when rebating, although I would clamp a piece of timber to sit above the blade to prevent hands getting near the blade at the beginning or end of the cut.

My biggest concern with a cut down riving knife is thoss machines where the riving knife is the crown guard mount. -the danger I see is the temptation to use the saw with no guard just because 'its not worth swapping the RK back just for this cut'..........

 

[doctor Bob]

Yes, that is fair enough.
And I could do a rebate up to 3/4" in one pass because I have a dado head, so nah, nah, na-na, nah!

But I'm sure you take my point.

I do, just being a smart ar$e.

 

[Doug71]

However, I do cut rebates on the saw, and to do that I have to remove both guard and riving knife. Could someone correct my ignorance if necessary, but I was under the impression that a riving knife serves no useful purpose in a rebate, because the wood is a single solid piece, so nothing is going to move and bind on the blade. All my knowledge is from here, or YouTube, and this little nugget is definitely of YouTube provenance, so a definitive ruling would be nice.

Thanking you in anticipation...

You still need a riving knife really depending on how deep you are cutting. The wood can still move because of internal tension and try to grip the blade even if you are not going right through, especially if it's case hardened.

 

[doctor Bob]

This is my set up.

The guard just pulls/ pushes up and down. I like to see what I'm doing, but it needs to be low enough to extract efficently.
The riving knife is set 1mm lower than the blade.

I have found over the years the biggest culprit for errors on a saw is firstly user complacency and secondly a dull blade. If you can drag your finger over a blade without it properly catching the skin then it's blunt.
I do a lot of cutting and can easily get through 4-5 saw blades a week.

If you've never used a sliding panel saw it's just a pure luxury compared to a table saw.
Most hobbyists will have the fence between them and the board, I like to have the fence at the end of the board. i.e. most people would have the fence at the other end of the sliding table. Not that unusual in the commercial world.

What ever your set up, take it seriously

 

[Trevanion]

I do a lot of cutting and can easily get through 4-5 saw blades a week.

I can tell just by the single piece of foam matting by the saw, someone spends a lot of time standing in that spot :lol:.

I personally prefer having the fence/arm behind the workpiece but I seldom do work with sheet material, 95% of the work is with solid wood usually over an inch thick so I feel the fence helps to carry the workpiece through the blade whilst I would think if the fence was set up the way yours is it would be more prone to coming away from the fence and binding on the blade. I've never had it set up that way mind so it might be just as easy.

How do you find the Altendorf to use? I only hear good things.

 

[doctor Bob]

The WA 80 is a great mid way size saw. We've had it about 10 years now and i've probably realigned it twice in that time. Rock solid.
I think Altendorf and Martin are the bentley and rolls royce of saws, Martin is probably edging it, but budget is always a consideration.
If I got another I'd stick with another WA80 but with electric fence and a control screen to speed things up a bit.

 

[Trainee neophyte]

Well, I can't compete with the size of Bob's tool, that's for sure. No wonder he needs to wear those special glasses.

However, realising that I know nothing, I have decided to rectify the problem by purchasing Mr Maskery's excellent video tuition guides. I reckon at £5 per finger, it's got to be a worthwhile investment. All I need now is some international internet banking, which is proving trickier than you might think. Money in the post, Steve, I promise!

 

[Trevanion]

I think Altendorf and Martin are the bentley and rolls royce of saws, Martin is probably edging it, but budget is always a consideration.

Saws aren't really my bread and butter, but I've used almost all the makes of spindle moulders like Kity, Jet, Sedgwick, Felder, SCM, Wadkin and Martin. The absolute best machines I ever used were the Martin ones when I was working for another company, which were a large T-25 and a pair of smaller T-12s. The build quality was second to none and was leagues above even the high-end SCM machines in my opinion, they were far better thought-out as well and definitely designed for a very heavy use, high production environment. I loved them very dearly and it was a shame when I had to leave them behind, I think if you can afford it, they are worth every penny more than any other high-end moulder.