Passing timber diagonally over saw blade to create curve ?

[Aled Dafis]

Well, i may be in the minority, but i have also done this in the past week.

As has been said before, i think it is safe enough for a competent person to do if they are sensible about it.
ie. clamp fences both sides of the work piece, a bridge between them over the blade and take very small cuts feeding the wood slowly.

the riving knife isn't an issue as you aren't cutting a kerf that can close on the blade.

Same here, I've done it a couple of times and as long as you've got your wits about you and clamp lengths of wood to act as fences both sides with a "bridge" screwed in place over the spinning blade, it's pretty safe. I wouldn't hesitate to do it again if the need arose.

Cheers
Aled

 

[Aled Dafis]

For those who want to use this method, here is a calculator for the set up.
http://woodgears.ca/cove/calculate.html

Bob

That site also gives a pretty good description of how to go about cutting said coves

http://woodgears.ca/cove/index.html

I would however advise users to use a second "fence" on the left hand side of the work and screw a "bridge" over the spinning blade.

Cheers
Aled

 

[9fingers]

There are two ways to manage the risk when using machines for jobs they were not designed to do.

1) Find another way to do it

2) be aware of the things that might go wrong and take measures to reduce the probability of them happening to near zero.

Either method is acceptable. What is not acceptable is to dive into doing something you've not done before without thought as to the consequences.

Bob

 

[Hudson Carpentry]

I have done it to make a cornice. In all honestly I would do it again.

I used two lengths of timber to guide it top and bottom, went slow and only taken a few mm off at a time. My guard is supported over the table so its still in place.

I naturally was worried and caucasus the first time but didn't once feel out of control or in danger. The result was rough but it didn't take long to clean up with some 120grit paper.

 

[jordec66]

I'm also with chems on this one. Any machining operation has inherent dangers, as long as the workpiece is clamped to minimise movement it should be no more dangerous than many other woodworking techniques, spindle moulding for example. It is all about risk management. If you don't feel competent or safe, then don't do it.

 

[Dodge]

Norm abram demonstrated this on the NYW cant remember which show

Well that sums it up in my opinion - i wonder how many people have ended up in A&E after trying to copy Norm - personally I cannot stand the guy and so many of his methods are just plain dangerous!

Hey Dodge...around here that's fightin' talk! :mrgreen: :mrgreen:

Couldn't agree with you more mate...can't stand the guy either!

You watch the front door...I'll cover the back! :mrgreen:

Jim

:lol: :lol: :lol: :lol: :lol:

I've got some 4by2 (hammer) (hammer)

 

[Hudson Carpentry]

:lol: :lol: :lol: :lol: :lol:

I've got some 4by2 (hammer) (hammer)

Poplar or Cherry :wink: :lol:

 

[flanajb]

Based on the replies on page one, I thought creating a cove with the saw was a big no no, but having read page 2 I have changed my mind. It does look like a neat way to create a cove for cornice.

 

[woodbloke]

I have seen this sort of thing done in a pro 'shop on a spindle moulder, which is the only way (or was in this particular 'shop) that it could be done. However the guarding constructed to make the cut(s) was pretty phenomenal :shock: - Rob

 

[jimi43]

Clearly there are those willing to sacrifice body parts for some coving.

Personally...I would rather buy it. :wink:

But if anyone wants to go ahead and try it...who are we to stop you? It's a free country after all.

Just bear in mind that 50% of the thread said don't...I guess that's fairly good odds.... :mrgreen:

Jim

 

[Digit]

On the safety issue, my basic training goes back over half a century, and one item arises on here regularly, so I'm going to ask an apparently daft question.
What is the function of a riving knife?

Roy.

 

[Chems]

I've started a pro TS coving movement!

But if anyone wants to go ahead and try it...who are we to stop you? It's a free country after all.

That's exactly the point, we are dictated to in all walks of life and treated as if we are idiots, at least let us use our own judgement in our own workshops, everythings dangerous when your working with cutting blades. I used to go into burning buildings as a day job, very unsafe, but with the right precautions, protections and training it was deemed ok by the powers that be. Just apply the same logic to everything you do in the WS.

50% of people haven't tried it so they can't comment, meaning 100% of people who have thought it was OK! Statistics can be twisted!


@Digit, it stops the wood pinching the blade, closing up after its cut and then the blade getting hold of it and firing it back. It also protects the back of the blade stops offcuts getting launched from the back and also helps to keep the wood straight and not allow it to pivot on the blade and cause major kickback. And it holds the crown guard sometimes too.

 

[houtslager]

I've done it several times,and I do beleive CMT sell a saw blade [10"] specially made with rounded over tungsten tips.

 

[Digit]

All that is so Chems, but was not always so. For example, crown guards on pro machines were not necesarily attached to a riving knife, anti kick back pawls are probably more effective at preventing kick back. In a conversion shop jamming might be a problem, but during my apprenticeship, where only dry timber was in use, I never saw a kickback.
No, on pro machines of yester year short rip fences were the norm, on 'hobby' type machines the long fence is now the norm, mainly for cost purposes I assume. In the past, and on my TS, the riving knife was to keep the timber in line with the short fence.
The long fence on my TS serves only to mount a short fence.

Roy.

 

[tool613]

I do not know if its an American idea but it is very effective at shaping wood with the sides of cutters. If you think that running a board across a TS blade is scary just look at the old Wadkin pattern mills. BAck in the day and no glasses, OH HOW WE LIKE TO SEE THE CUT. :lol:

The riving is for rip cuting and keeps reation timber from pinching the back of the blade a major cause of kick back. seeing this is not a rip operation the only guards i would add is a power feeder and twin fences. It work best with heavy set carbide tiped rip blades.


jack

 

[AndyT]

Yes, definitely not a new idea - this is from Ellis, Modern Practical Joinery, 1908:

- but I still wouldn't fancy doing it, even with one of Jack's Wadkins.

(Incidentally, the text explains that the saw in question is an American one, from the Colburn Machine Tool company in Pennsylvania.)

 

[tool613]

Well Andy that good evidence that is may be American. The old Oliver[1] fences tilted like that and now i know Why.


[1] Oliver did sale the wadkin pattern mill under licence in the US in the 20s


jack

 

[Digit]

It's a strange fact Jack that many people over here are terrified of some of the practices carried out in NA, yet you people seem to have an obsession with kick back. Reaction timber, I find, normally moves away from the blade, so with a long rip fence on the right, without a riving knife it will contact the back of the blade and lift and possibly kick back as it pushes against the fence.
A short fence prevents that situation from arising, I grant that a riving knife is effective if the timber pinches, but my post was that that appears not, in the UK at least, to have been its original useage.
If you use a short fence, as I normally do, then any movement towards the fence does not result in jamming, so that problem is eliminated, but without the riving knife the last part of the cut is not guided. So a riving knife is essential with a short fence.
A riving knife and a long fence only solves the pinching part of the problem.

Roy.

 

[tool613]

Roy
I can tell you here in Canada the safety regulation are p1$$ poor . Many in the US do not understand that the riving knife is used in concert with the high low sliding rip plate fence and crown guard.Most think it in the way and think a splinter is a riving knife. no attention to the knife thickness is made or the placement behind the blade. I do believe that in ten years there will be no more saws with blades and only CNC routers. most saws in the US are sliders(SCMI) and most if not all ripping is straight line no fence. so I could not agree more.


I have thought that the riving knife was from saw mill with carriages as was the short fence like this Stenner. I believe it is older than 1930 too.

http://www.youtube.com/watch?v=0UUwZVIGq7s

jack

 

[Digit]

I know that you have seen the thread about the Wadkin find and as you can see the table saws have a very short fence so once your timber passed the end of that only the riving knife kept it on track.
See here....

http://www.ebay.co.uk/itm/Sedgwick-16-R ... 4cfdf99139

...even modern quality machines have the short fence.
Personally I'm not keen on fences that short, by using a sliding sub fence on the full length fence I can adjust for different blade diameters, to ac as a gauge when cross cutting repeat lengths etc.
In other words, the best of both worlds.
Those pics of the Wadkin shop remind me of my apprenticeship. :lol:
I was the one who swept it clean!

Roy.