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Riving knives

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Riving knives

Postby Wizard9999 » 17 Oct 2016, 15:29

OK, I'm ready for this one to head off topic, but here goes.

I have the old version of the Xcalibur cabinet saw, I believe it is a clone of a Delta Unisaw. The riving knife on the saw sits significantly proud of the blade. Over the weekend I was watching a few YouTube videos and I stumbled on some polished by Sawstop. On their saw when using it to make non-through cuts (not with the dado stack which is does take, but just the standard blade) a riving knife can be fitted that is no higher than the blade. This replaces what on the videos they call the blade guard, but what is in fact a taller riving knofe to which is fitted the blade guard which is combined with overarm dust extraction.

A couple of questions spring to mind.

First, does anyone have any experience of a saw with a similar height riving knife? I'm pretty sure I have seen other YouTube videos posted from the US with a riving knife that is not higher than the blade, but can't recall seeing or hearing about anything from the UK.

Second, any thoughts on the feasibility of creating such a riving knife for fitting to a saw where the standard riving knife sits above the blade? Of given the way the blade rises and falls in the saw would the riving knife end up changing height relative to the blade. Could such an issue be addressed by creating a riving knife with the right shape of curve at the top?

Anyway, any thoughts on the riving knife question would be much appreciated.

Terry.
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Re: Riving knives

Postby Robert » 17 Oct 2016, 16:29

What you are describing is exactly what I did on my Axminster TS200 saw. I made my own riving knife and did it so it was slightly lower than the blade top. I can make plough cuts with the saw without having to remove the knife.

Pictures in here -

viewtopic.php?f=23&t=1017&p=16646

The bayonet slot at the back is so I can put the crown guard on and off quickly.
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Re: Riving knives

Postby 9fingers » 17 Oct 2016, 17:06

I solve the problem by keeping my riving knife somewhere in a drawer. I know this will not suit everyone's taste :oops:

I have found no need for top extraction on the same saw as yours Terry because I have balanced the airflow in the cabinet by blocking up the gaps between the underside of the table and the arc for the blade angle setting with draught proofing brushes and so the air to satisfy the dust collector pressure reduction virtually all comes down through the blade slot taking the dust with it.

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Re: Riving knives

Postby RogerS » 17 Oct 2016, 18:20

The riving knife on my Dewalt 746 table saw is also like that with the top of the knife slightly below the top of the blade. Of course, it helps to take into account the thickness of the riving knife when ordering a new blade. :oops: DAMHIKT
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Re: Riving knives

Postby 9fingers » 17 Oct 2016, 18:53

For anyone who is not aware, the thickness of the riving knife MUST adhere to the following rule.

Thickness of the blade body < Thickness of the riving knife < Thickness of the cutting tips (or kerf)

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Re: Riving knives

Postby Pinch » 17 Oct 2016, 20:26

My riving knife went on walkabouts like Bob's knife.

It's in the 'man drawer' with lots of my other man stuff collected over the decades.
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Re: Riving knives

Postby 9fingers » 17 Oct 2016, 20:31

Jeez Paul, here is something we agree on at last :lol: :lol:

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Re: Riving knives

Postby Pinch » 17 Oct 2016, 20:33

Easy tiger.... :lol:
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Re: Riving knives

Postby 9fingers » 17 Oct 2016, 20:36

Pinch wrote:Easy tiger.... :lol:


I just knew you were ok really Paul! :lol:

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Re: Riving knives

Postby Pinch » 17 Oct 2016, 20:47

Hey, there's nowt wrong with me chap - mother thinks I'm wonderful. :lol:

Oh okay, I have a few little quirky unconventional ways maybe 8-)

Or possibly quite a few actually.

Hmmm... probably rather a lot maybe.

In fact, I'm always in cloud cuckoo land. :lol:


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Re: Riving knives

Postby Wizard9999 » 17 Oct 2016, 22:26

Robert wrote:What you are describing is exactly what I did on my Axminster TS200 saw. I made my own riving knife and did it so it was slightly lower than the blade top. I can make plough cuts with the saw without having to remove the knife.

Pictures in here -

viewtopic.php?f=23&t=1017&p=16646

The bayonet slot at the back is so I can put the crown guard on and off quickly.


Robert

I presume that the path of the blade rise and fall mechanism means the top of the riving knife remains the same relative to the top of the blade?

Terry.
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Re: Riving knives

Postby Wizard9999 » 17 Oct 2016, 22:34

9fingers wrote:I solve the problem by keeping my riving knife somewhere in a drawer. I know this will not suit everyone's taste :oops:

I have found no need for top extraction on the same saw as yours Terry because I have balanced the airflow in the cabinet by blocking up the gaps between the underside of the table and the arc for the blade angle setting with draught proofing brushes and so the air to satisfy the dust collector pressure reduction virtually all comes down through the blade slot taking the dust with it.

Bob


I have previously found a thread on another forum where you posted on the topic. I was thinking of that the other day as it seems that whilst my dust extraction works well on all my other kit I still have mountains of dust in the base of the tablesaw.

But that is another topic, in this instance I am keen on the idea of being able to make non-through cuts with a riving knife in place. In such situations I am not worried about above table dust extraction. I don't suppose you know if it is easy or not to get hold of spares for the Xcalibur we both have? In an ideal world I am thinking that cutting down a standard issue riving knife would be the easiest route, given I don't have the kit to make something from scratch.

What I think I'll do tomorrow is a little bit of testing to see if the riving knife is positioned consistent to the top of the knife at different points on the blades rise and fall.

Terry.
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Re: Riving knives

Postby 9fingers » 17 Oct 2016, 22:49

I would not bank on any spares support especially as Woodford are now selling a different machine.
A new knife is not too hard to cut from a piece of ground flat stock or gauge plate as it is known.

The knife is rigidly fixed to the arm that holds the blade so you can cut the knife to suit the range of blade sizes you might use. It is mounted on slots so pick the range of blades and the slot positions before you cut!


I use blades from 7-1/4" to 10" - the small ones are skill saw blades which are great for narrow kerf cutting less than 1.5mm.

hth
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Re: Riving knives

Postby Wizard9999 » 17 Oct 2016, 23:58

9fingers wrote:I would not bank on any spares support especially as Woodford are now selling a different machine.

I fear you are probably right Bob.

9fingers wrote:A new knife is not too hard to cut from a piece of ground flat stock or gauge plate as it is known.

The knife is rigidly fixed to the arm that holds the blade so you can cut the knife to suit the range of blade sizes you might use. It is mounted on slots so pick the range of blades and the slot positions before you cut!

What would you recommend a non-metal worker use to cut it Bob, are we talking jigsaw with a metal cutting blade or does it need something a bit more manly?

Thanks,
Terry.
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Re: Riving knives

Postby Rod » 18 Oct 2016, 02:46

Hacksaw, files or even a belt sander to finish off.

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Re: Riving knives

Postby kirkpoore1 » 18 Oct 2016, 03:58

Jigsaw with a metal cutting blade will work easily. Noisy, though.:)

My Oliver TS has a riving knife that can be adjusted vertically. I had to trim down some of the area at the bottom to let it drop far enough, but I have it just below the top of the blade. You have adjust the height if you change blade diameters. I have a 14" blade on the saw now, but can easily put a 12" on there.

I'm not going to pick a fight here, but as somebody who's used saws with and without splitters and guards, my riving knife makes me feel much safer. I do use my guard, but it is in no way attached to riving knife and does not include any dust collection.

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Re: Riving knives

Postby Tusses » 18 Oct 2016, 11:57

kirkpoore1 wrote:Jigsaw with a metal cutting blade will work easily. Noisy, though.:)

Kirk


I'd say that too .. and as they say , let the blade do the work .. if you push, it will blunt , just like that !

My "splitter" is in a drawer somewhere too.
I mainly cut MDF, and most of the time I have a sled on the table.

as for the knife .. mines a 60's wadkin, with the slot type fixing , which can have it's own disasters.
I don't think that's been mentioned so far ?
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