pull mitre saw disasters again

[devonwoody]

I reported an accident last week (cutting through a metal ruler) Pleased to say no more accidents but are readers aware that if they hold down a piece of timber on the saw bed of these type of machines instead of locking down, the blade can throw the timber back to the fence and trap your fingers between the timber and fence. OUCH!!!!

 

[Alf]

Oooooouchhh, indeed. I can safely say I'm now aware of that, DW. I assume this is a "DAMHIKT" type of post...? :roll:

Cheers, Alf

 

[Mike.C]

Hi Devonwoody,

Great tip. The reason this happens is because a mitre saw has a special blade (i forget the name of it) which to stop it kicking the work towards the operator as a table saw would, it pushes it towards the mitre saw fence. Because of this you can only use a blade made for a mitre saw and not one made for a table saw.

Silly really because i am sure you all know this.

Regards

Mike.C

 

[Midnight]

Devon.... you realise that if this keeps up, we'll have to have a whip round to donate you a hand saw....

:wink:

 

[wood1000]

If rember right blade has a negative hook. As on a tablesaw the balde has a positive hook.

 

[Aragorn]

I would take issue with this a little - some mitre saws require a negative angle blade, but others do not. I don't know which is which - but I suppose the blade that comes with your machine will set the standard, and the instructions should make it clear.
Negative angle blades are intended to reduce kickback in mitresaw use, but many saws are designed to allow for positive angle blades instead.
I found out about this when changing from my EB mitresaw (negative angle) to the Makita (positive).
Hope that helps!

 

[Mike.C]

Hi All,

Wood1000 yes i believe you are right.

Ohio, that brings back memories. A couple of years ago i lived just outside Madison for a few months.
I then moved down to a place called Carson in L.A. California. I regally drove between L.A. and San francisco along Highway 1 (or pacific Coast Highway as they call it). Just before you get to San francisco is a place called Big Sur. Now thats a place with plenty of wood. I have never seen trees as big as the ones they have there. To give you an idea of how big they can get, someone had carved a room out of the inside of one, i believe it was a red wood. They had even carved a staircase. brilliant.

Thats enough of that.

Regards

Mike.C

 

[Mike.C]

Hi Aragorn,

I stand corrected. My mitre saw is also an Elektra Beckum and in the instruction manual it states that you must only use a negative angle blade. They even make out that it can be dangerous to use any other blade. This is why i thought that they were all the same.

It just shows that we can all get it wrong.

Regards

Mike.C

 

[johnjin]

Hi All
There is no difference between a blade for a mitre saw and a table saw.
Normally you would have more teeth in a mitre saw blade if you were troubled by tearout. A negative rake blade is for very high amount of teeth to reduce tearout but also used for cutting some materials like plastic. The problem that Devon experienced sounds to me like he was holding the wood on the table instead of pushing it against the fence and holding it down at the same time. It is imperative that you push the wood against the fence on a mitre saw. It is impossible to trap your finger between the wood and the fence if you are using the saw properly regardless of what blade you are using.

All the best

John

 

[Anonymous]

Did you know radial arm saws do the same , i do ,i ended up with a compound fracture to my thumb .Thats what you get for stacking timber for repeat cuts near the blade .Slight lack of consentration and the blade grabs it and drags it at high speed towards the hand holding the piece your cutting

 

[Aragorn]

With respect to everyone making these warnings, it does make me wonder how you are using your mitre-saws/RAS! Why is there a gap to trap your fingers in between the wood and the fence to start with? Unless I've understood this wrongly I strongly recommend a review of the manual!

 

[Anonymous]

Aragorn you misunderstood me i trapped my thumb between the piece i was cutting (held firmly against the fence) while i had a pile of spindles ready for cutting near the blade . I thought they were far enough away not to get caught but i was wrong .
P.S that was nearly 20 years ago when i was a mere apprentice, i was of the age when you know everything (hammer) . My thunb still does not bend quite right so its a constant reminder to be careful . Could have been worse at leats its still attached :lol:

 

[Mike.C]

Hi Johnjin,

My ELEKTRA BECKUM manual states:

Saw Blades

Important!

On this saw only saw blades with a negative chip angle are permitted for use.
The negative chip angle keeps the work pressed against the fence while being cut.
DO NOT USE BLADES WITH A POSITIVE CHIP ANGLE.

As i stated in my first post this blade pushes/keeps the work against the fence.

I mistakenly thought that all mitre saws use these blades. This is because i have only ever used Elektra Beckum mitre saws again with the same sort of blade.
My table saw has a positive chip angle, so i cannot use my table saw blades in my mitre saw. In my view there is a difference between these blades.

Mike.C

 

[Anonymous]

we'll have to have a whip round to donate you a hand saw....

mind ... don't be SO confident: once I've been able to cut my hand with a dozuki !

 

[CYC]

Devon.... you realise that if this keeps up, we'll have to have a whip round to donate you a hand saw....

Midgnight, this may not keep Devon out of trouble! Once a friend/neighbour was cutting a piece of timber with a hand saw when I pulled into my driveway. He looked up to see who was coming and cut his finger down to the bone... Ouch He used to hurt himself so many times woodworking!!! He is gone to scotland now and I believe still has all his fingers working as a carpenter

 

[Aragorn]

Aragorn you misunderstood me...

Fair enough! - thanks for making that clearer AP. Stern remarks withdrawn!

 

[Anonymous]

Morning All,

If I remember correctly, the negative rake is there to try and minimise the saw from racing across the timber on a pullover mitre saw.
These are meant to be used by pulling the head over the work, then dropping into the work from the front and pushing back through the work, not pulled through it.
If it's pulled through, a positive raked tooth will grab and pull quickly which can take you unawares and lead to an accident.
On a static head chop saw you don't have the problem as you address the work directly over it, hence these are normally fitted with a positive rake.

Andy

 

[ike]

Not all crosscut saws are necessarily dangerous if using a positive rake blade. It depends on the amount of rake. For example a +5° rake works very well and is quite safe, as I have a CMT blade fitted on my saw for a long time now. I don't have a clampdown and I have never had a hairy moment with it. I did try a negative rake blade once. It is superb for laminates (also recommended for aluminium -clamping vital!) but not so good for timber. The problem with using positive rake blades on mitre saws is that if the angle is too great, the blade transmits a significant upward force on the timber lifting it into the blade. Obviously, it is the reverse of this on a table saw - pushing the work down onto the bed, hence table saws can use blades with up to +40° rake

I did once in someone elses workshop, use a radial arm saw fitted with a positive hook blade, and by heck, that thing was an accident waiting to happen.

Ike

 

[Guest]

Anybody who has used a r.a.s will know the value of a negative rake blade as the feed is from the opposite side to the saw direction and the positive rake blade will try to run towards the operator, depending on the depth of cut it can jam or even bend the blade.Don't ask me how I know this.

 

[Rattie]

Morning All,

If I remember correctly, the negative rake is there to try and minimise the saw from racing across the timber on a pullover mitre saw.
These are meant to be used by pulling the head over the work, then dropping into the work from the front and pushing back through the work, not pulled through it.
If it's pulled through, a positive raked tooth will grab and pull quickly which can take you unawares and lead to an accident.
On a static head chop saw you don't have the problem as you address the work directly over it, hence these are normally fitted with a positive rake.

Andy

Interesting you say this Andy, because that was my assumption until I got my Elektra Beckum KGS 303.

Reading the manual, which I now do as part of the new toy bonding ritual - also points out any misconceptions I might have had about even the simplest tool - I noticed a written instruction and diagram clearly showing the user to start at the back and do a climbing cut through the workpiece, ending the cut with the blade coming to the point nearest the operator.

Now this seemed odd to me, especially as I'd seen plenty of other users doing the opposite action, namely pullover, chop, slide back while cutting, then lift up, powering off. Obviously the climbing cut could cause runaway toward the user, but in practise it does not. With the saw design the way it is, the climbing force is easily managed with the high leverage handle.

Benefits would seem to include the ability to see the cut in progress, and it would appear easier to hold the workpiece down by hand in a mitre cut, without it trying to crab along the fence in the direction of cut. It also seems to prevent "explosive" breakout at the back of the piece.

Martyn

PS the saw ships with a slightly positive rake blade, which they advise for wood. The negative rake blades are generally only for laminate and aluminium.