BC's KAPEX Problem

The only way I can think of this cut NOT throwing the offcut away at projectile speeds, is when the blade is large enough / positioned in a way that the front teeth have cleared the wood when the back teeth complete the cut and there was some sort of non-stick coating to the blade, so the weight of the offcut wouldn't be enough to bind while the saw spins down.

But that's a lot of requirements compounded....

Regards,

Job
 
Could a guy put a board on the offcut side, held down with a clamp to imobilize the offcut?
 
WarnerConstCo. said:
jvsteenb said:
If THAT was really the cut he tried to make, I'm not at all surprised by the fact that the Kapex did it's cannonball-trick.
But I DO wonder how anyone managed to do this with any other chopsaw WITHOUT somehow entering the projectile-phase ???

Regards,

Job
Click to expand...

That is the cut, and I don't know either.

I tried the same cut on 3 different saws this morning and had bad results.

He said he has done it 1000's of times though without one problem on his makita.
Click to expand...

Same bad result like Kapex on all 3 different saw?Seems like Makita didn't have this problem?
 
Wonderwino said:
Could a guy put a board on the offcut side, held down with a clamp to imobilize the offcut?
Click to expand...

I think the only thing to do is have more off cut to the right.

I had the same results on a rigid, dewalt and older makita.

It is just a dangerous cut to make.

I have no issues with making mitered returns. 
 
Same bad result like Kapex on all 3 different saw?Seems like Makita didn't have this problem?
Click to expand...
That's what he said, so either he's been unbelievably lucky, or there's something different that I can't yet grasp.
Just to be sure, I tried the same cut with my Electra Beckum non-sliding CMS ( nowadays Metabo ) just a minute ago: and it was as I expected: a VERY bad idea....
I have brick walls and a steel door in my shop, and made sure the window wasn't in the projected path so no harm done but this certainly isn't a cut one would want to perform in general...

BC: did you use the sliding function when makin the cut on either saw, and were you cutting on the pullstroke or on the pushstroke?

Regards,

Job
 
Interesting thread guys. The problem does exist to some degree whatever mitre saw you use,( or even a radial arm saw) usually the smaller the workpiece the more reaction you get.
My get out for those times when the offcut is small is to creep up on it (No! that does not mean take it by surprise ;D)
When the waste portion is too small to use its own weight to stay put, I take several small passes to remove the waste, while it takes a few moments longer it prevents a random projectile clipping someones ear or worse. It is most prevelant in my experience when mitreing mouldings to fit under stair treads or small glazing beads. It also seems more likely with blades with a lower tooth count/coarser cut.
Rob.
 
jvsteenb said:
Same bad result like Kapex on all 3 different saw?Seems like Makita didn't have this problem?
Click to expand...
That's what he said, so either he's been unbelievably lucky, or there's something different that I can't yet grasp.
Just to be sure, I tried the same cut with my Electra Beckum non-sliding CMS ( nowadays Metabo ) just a minute ago: and it was as I expected: a VERY bad idea....
I have brick walls and a steel door in my shop, and made sure the window wasn't in the projected path so no harm done but this certainly isn't a cut one would want to perform in general...

BC: did you use the sliding function when makin the cut on either saw, and were you cutting on the pullstroke or on the pushstroke?

Regards,

Job
Click to expand...

You have to slide the head out and push back, it is a 1x8".
 
Yes, that would be the "logical" way to do it. But I see a lot of guys doing it reversed, more or less like using a RAS.
So: Spin up the saw, lower it, and pull it through the wood.
As long as the saw doesn't prevent either method, there's at least these two methods to make the cut.

All the times I used a stationary RAS, this was percieved as the preferred way of using it.
The force of the blade was more then adequate to pull the workpiece into the fence instead of pushing it away, and it was the surest way to expose the blade for the shortest possible time.
And a RAS on full speed can be quite an intimidating tool...

So perhaps the OP has inherited this habit and uses his SCMS on the pull stroke ?
I'm just trying to figure out how it's possible to do this cut with ANY SCMS without it skyrocketing the offcut....

Regards,

Job
 
WarnerConstCo. said:
I don't think it is but, he seems to say he can with his makita.
Click to expand...

I'm another one that has had good luck with my Makita saw. I can make the same type of cut with little chance of producing a wooden missile.
 
Brice Burrell said:
WarnerConstCo. said:
I don't think it is but, he seems to say he can with his makita.
Click to expand...

I'm another one that has had good luck with my Makita saw. I can make the same type of cut with little chance of producing a wooden missile.
Click to expand...

what model Brice?

Not the new one but, the one before it?
 
Could it be that the Makita uses a 12" blade vs a 10" blade on the Kapex.

With the bigger blade you will less likely have the teeth that enter the workpiece touching the material when it's completely cut.  This isn't a great difference, about 10mm when I make a quick sketch in autocad, but it might be just enough.
This measurement changes whit how much your sawblade is below the table.  The lower it is the more clear distance you have.

a picture says more than a thousand words, so they say...

10_vs_12.jpg


On the left a 10" Kapex blade, 5mm below the table.  a piece 150mm wide will still be in contact with the spinning tooth when it's cut off.

On the right a 12" blade, 10mm below the table.  the same 150mm piece is clear of the tooth when it's completely cut
 
That's exactly what I was referring to in my reply a couple of posts above.
Will this prove to be the discerning factor ?
In that case it might be interesting to determine the size per saw that could/would turn your saw into a projectile thrower.
But however useful that might be, it should be stated very clearly that a cut like this is inherently unsafe, whatever size stock you cut and should be avoided.
Rob has offered a perfect solution: Sneak up on the cutline. Sawdust doesn't make very effective projectiles,

Regards,

Job
 
Thanks to WarnerConstCo for taking the time to take some photos! Hopefully he won't mind me altering one of them and using it for my post...

In the example shown below, it seems to me that the centre of gravity of the offcut (green arrow) is outwith the base of the offcut, meaning that it will fall over to the left (red arrow) as soon as the blade has severed it. And when it topples to the left, it will fall on the still-spinning blade, which then throws it backwards and/or upwards.

[attachimg=1]

If the offcut was longer, even just by a little bit, the centre of gravity would remain within the base of the offcut and it wouldn't topple onto the spinning blade when severed. Naturally, the longer the offcut, the less likely it is to move into the path of the spinning blade by other factors, eg blade draught or vibration

[attachimg=2]

Forrest

 
By all means Forrest, feel free to use whatever you want.

That is why I took some pictures.

Like you said that off-cut falls back into the blade while it is still spinning.

To solve this, you just need more meat on the off cut side.

The 4th picture is what that little off-cut did to my throat plate, that was a hard smack.

Next time I may not choose to participate in a scary science experiment though. [unsure]
 
This sounds like something that could be solved with a little bit of blue tape.

Using Werner's pictures as a reference, run the tape across the top of the board and then pulling it to the right.  When the scrap piece comes free, the tape will pull it right slightly keeping it away from the blade.

An extra step, yes, but should avoid creating a projectile.
 
Darcy, I had the Makita 1214, that's the model with a 12" blade.

The problem with making multiple cuts is unless you make a dozen of so cuts that only produce sawdust you'll still get projectiles. And the problem with leaving a bigger cutoff is you need a (much) bigger cutoff than you'd think. This wastes material. Okay, then don't make this cut right? I make this cut all the time for coping, I have to do, too often to stop.
 
Thanks for posting that link Warner. As you guys can see i am using a 10" Makita but i may have not explained correctly but my bevel is the other way around. Not that it makes any difference because it does it with both 45 bevels. I have gone back to using the Makita for now and cut maybe 40-50 cuts of all different sizes and didnt have the kick back problem.
 
You must log in or register to reply here.

Similar threads

R
Replacing broken "Dust Extraction Attachment" on Kapex 120
Replies
2
Views
269
RonMiller
R
S
Best track saw blade assortment for 5.5" blades
Replies
8
Views
577
peter halle
peter halle
onocoffee
Wood Tension While Cutting with TS 55 FEQ
Replies
3
Views
142
smorgasbord
S
S
Kapex center of miter angle rotation?
Replies
16
Views
617
smorgasbord
S
B
Aluminum blade for Kapex120
Replies
1
Views
111
tjbnwi
tjbnwi
Back
Top