Video of tablesaw kickback

[White House Workshop]

On long versus short fences... When I was being taught to use the tablesaw the instructor stressed that there were always two measurements to take, the first was at the front of the blade for the correct width of cut and the second was at the back of the blade to make sure it was the same! Most tablesaws come with fences that are notoriously inaccurate and that clamp front and back. One day I'll be able to afford a Biesemeyer fence set-up......

 

[head clansman]

hi guys

its not the machine that causes kick back , after all if its set up properly with all guards fitted it wont hurt you anyway that's what the guards are there for in the first place , the cause of kick back is i was going to say if there no guards fitted but that not true,
( not that i recommend the use of machine with no guards i don't i can't stress enough the use of guards)

It can be the operator lack of experience and usually not paying enough attention whist operating the saw i e : allowing the timber to wander off course slightly which is the cause of many kickbacks but most kick backs are caused because of poor quality timber choices IE.. bad grain run in the timber ,it 's moisture content is to high, and lack of knowledge in the operators experience.

With the fence set to it correct length just pass the the front teeth on the saw blade, (most modern saws fences cannot be adjusted in it length like the older saw were ) so a lot of you have a problem straightaway as nearly all modern fences are the length of the saw bed and are lockable at both ends, the riving knife fitted but most importantly the over head guard set so it just clearing the top edge of the work piece .

if your timber closes on the riving knife then switch off withdraw his work piece and start again where the timber has closed the second cut will open the thickness of cut cut allowing the timber to slide through if this happens on the second cut then this is down to poor quality timber scrap it and get some more for your own safety , also if the over head guard is fitted to the correct height just clearing your work piece this will stop the timber rising to eliminate any kickback again if your workpiece trying to rise again switch off and try again , again if it happen the second time scrap it. oops nearly forgot to mention on saws with blade height adjustment make sure your blade is set to the correct height don't lower the blade so it just breaking the surface of your work piece that to shallow a cut, it can cause the work piece to rise certainly if the operator lacks experience and is pushing to fast it will tend to ride up over that's because there's not enough downward motion cut from the teeth to keep the workpiece down on the saw bed.

 

[Shultzy]

Talking about the kerf closing up, I've noticed that on a piece of pine I cut recently the rear saw teeth have left marks on the wood. Is the kerf closing up before it gets to the riving knife or is the fence not parallel to the blade?

 

[Steve Maskery]

Hi Steve
It could be either. It could also be that your riving knife is too thin for the blade.

Sometimes the stresses are so great that the wood tightens on the riving knife so much that it prevents you cutting. I've had that recently. All you can do really is stop the saw. wedge the kerf open and carefully continue the cut.

I've been cutting idigbo this week for my windows. One board was rather wonky so I snapped a chalk line and bandsawed it. I didn't have to cut the last 8", it just went BANG and split itself. That snapped chalk line is now a curve with a 3" rise over an 8' length! I've never seen anything like it, and I wish I'd taken a photograph. On the plus side, the other edge, which was very wonky before, was not reasonably straight, as, of course, it would have been cut at the mill in the first place.

Cheers
Steve

 

[Digit]

I have used table saws where the riving knife, if it had one, didn't sit in one plane or another with the blade, which means trouble. But if the knife lines up properly in all directions it will keep the timber running in a straight line once past the blade.
How many of us have actually checked that the knife is vertical when the blade is, does not aim the timber to the left or right, and does not have a bend in it?
I have, I had no choice as it was visibly out when the saw was delivered, and it took me 2 hrs to get it aligned.

Roy.

 

[steve tighe]

In Steve's second clip you can see the piece riding up a bit off the table

Do you know, I didn't realize that that had happened until quite some time after I'd published the video, I certainly wasn't aware of it at the time, nor during editing, which seems astonishing now.

I think the problem was that I was trying to be a super-good boy and use the push stick too early. Pushing down off the front edge of the table raises the workpiece. I should have used my hands until the workpiece was entirely on the table an only then picked up the pushstick.

Cheers
Steve

Tell you what else I noticed there last night watching the vid Steve,your riving knife is set to high.Shouldn't be any daylight between the top of the blade & the guard,mate.

When the piece starting riding up I thought "hope it doesn't catch the teeth at the top of the blade" then you would've had a kick back and an 'alf,Think bows & arrows.

That's a good vid all the same mate,it wouldn't be something I'd ever want to do mind,but there's different reasons for that,where you've got the pressure jig on the left of the blade you might want to think about incorporating something similar along the fence you've made to hold the piece down to the bed to prevent any riding up,think of it as an extra hand.

 

[Slim]

But if the knife lines up properly in all directions it will keep the timber running in a straight line once past the blade.

I don't completely agree with that. The riving knife should be ever so slightly thinner than the teeth of the blade, so there is still a chance that the rear teeth can come into contact with the workpiece and lift it up. ideally, once the end of the timber has passed the last cutting tooth and the cut is complete, it should be guided away from the blade, into the free space behind the fence with the pushstick.

How many of us have actually checked that the knife is vertical when the blade is, does not aim the timber to the left or right, and does not have a bend in it?
I have, I had no choice as it was visibly out when the saw was delivered, and it took me 2 hrs to get it aligned.

I do agree with that. The riving knife assembly on my SIP is poorly designed. The adjustment is far too hit and miss in my opinion. Also, if the knife is removed to enable the use of a tenoning jig, the vibration of the saw loosens all the bolts which hold the riving knife in position. So a complete re-adjustment is required when the knife is refitted. A right PITA.

 

[Digit]

Guess what Simon? I've got a SIP as well!
The HSE state that the riving knife should be slightly thicker than the blade but thinner than the kerf.
That could take some achieving as well!

Roy.

 

[Steve Maskery]

Steve
I know! But there is no adjust ment on the saw for that. That's why I made my replacement guard which you can see in my avatar and also in this month's British Woodworking.

Cheers
Steve

 

[steve tighe]

Bloody hell Steve :shock: :shock: :shock:

The riving knife isn't fixed to the rise & fall carriage ?

I'm definitely gonna start buying mags

 

[Niki]

In my opinion (only),no I wouldn't have the fence set that far forward

Hi Steve

I would like to show you a few pics that I made for some guy in other forum that claimed that "right tilt blade" is very unsafe for bevel cuts.

Please note the fence position...

Yes I know...the guard...but you would not see it clear...

Regards
niki

 

[David C]

Niki,

The thing I dislike about 45 deg cutting as shown above is that the left hand piece is resting on the moving blade and ready to jam in the throat.

I try to do all my 45 deg ripping on the bandsaw, a much friendlier operation? Can then clean up the surface on table saw as you show if necessary.

David

 

[Niki]

Hi David

As you can see on some of the pictures, the throat is very narrow and with all the cuts that I made there was no even tendency of the off-cut to enter into the throat.

A zero clearance insert would be better but this table saw does not have a "normal" throat...it's just a slot.

Sometimes, when the off-cut is very narrow, it is sucked into the throat at the end of the cut...in this case, if the piece is short, it is just sucked down and disappears below the table....if its long, it remains stuck between the blade and the throat...I just hit the STOP switch and when the blade stops, I take it out.

Band saw.......I don't have (nor the space for it)

Regards
niki

 

[Jake]

Bloody hell Steve :shock: :shock: :shock:

The riving knife isn't fixed to the rise & fall carriage ?

If that was the case it would be a splitter, not a riving knife, like on most (crudely engineered) US machines. But I don't think it can be, surely? I know it isn't CE marked so Woodford are gamblers anyway, but promoting and selling a machine without a proper riving knife in an EU market would be insanely risky from a legal perspective. It has to be a riving knife which is just a bit peculiarly high.

 

[Steve Maskery]

It has to be a riving knife which is just a bit peculiarly high.

Very peculiarly high actually, but yes, you are correct. Hence my recent mods.

S

 

[Jake]

Thought so. It does seem odd. Maybe the basic clone was of a machine which had a splitter, and someone knew that it needed to be changed to a riving knife/crownguard, but not how they work?

 

[steve tighe]

Hi Steve

I would like to show you a few pics that I made for some guy in other forum that claimed that "right tilt blade" is very unsafe for bevel cuts.

Please note the fence position...

Yes I know...the guard...but you would not see it clear...

Regards
niki

Alright there,Niki.

No probs about the guard,I know why it was done mate

What interests me,is that for the short piece you're putting through you've got the fence a lot further forward then the longer boards,for those the fence is more or less at the back of the blade on those pics.

I can see the sense now in having the fence well forward for the shorter pieces but I think I'd rather run longer pieces through & cut them to length after,even if it means wasting a lot of material.A tablesaw isn't a tool you can use a shoe on to run short pieces through.

Good pics though,they explain a lot better why some use that method then words do.

 

[OPJ]

Steve (Maskery), did I notice you also made yourself a new riving knife as well?

 

[Steve Maskery]

Steve (Maskery), did I notice you also made yourself a new riving knife as well?

Yes, an hour or two with a hacksaw and file. The hardest part was getting it the right thickness, I eventually got a mate with a surface grinder to fettle it for me. I should have just used 2mm plate to start with.
S