Dumb and Dangerous . . . . (me, not Festool)

[BC6738F5BCE98B4]

Earlier today I was happily cutting a 6 foot long piece of wood at an angle which would produce a piece of wood 7/8" at one end and 0" at the other.  I did this (as I have done two other pieces) by combining two of of the Festool guides and supporting them on the same thickness (3/4") wood as I was cutting.  I placed the support wood (and the piece to be cut) on pieces of 2 x 4 on my MFT so that I wouldn't cut the top of the MFT (again). 

I clamped the 2 x 4s to the MFT.  I clamped one end of the guides to the piece I was cutting and the other to the same depth wood I was using to support the Festool guides.  I clamped the supporting wood to the piece that I was going to cut.

I proceeded to make the cut (very smoothly) and everything was fine.  When I was finished cutting (I thought) I went to separate the cut piece from what it had been cut from and noticed that at the very end there was a small (less than 1" ) of wood that needed to be cut. 

I (think) placed the saw back on the guide depressed the trigger and started lowering the blade.  At this point the saw "jumped" backward and left gouges in the Festool guides.

I am perfectly willing to say that I must have screwed up in some manner, and can think of one thing that might have caused this particular problem.  I suspect that I did not get the saw fully and properly lined up on the guide before starting the blade.  I have had similar events with a radial arm saw, but over the years have taken a number of steps to try to avoid those situations or minimize the damage (to me and the surroundings) from the radial arm saw.

I would like the thoughts of others as to the most likely cause(s) of this event and the steps they would take to make sure that a) it didn't happen again and b) it didn't harm them (or other things) if it did happen again.

I would also appreciate any thoughts people might have on how to check to see if the blade was damaged (assuming that a visual inspection of the teeth didn't show anything obvious) or if the guide was so damaged that I should get another (after mounting the damaged one prominently as a reminder . . . )

 

[Eli]

I'd say plunge the saw fully and then start it to spinnin'. Since it's a do-over.

*I didn't read carefully at first, and having read comments below, I'm amending my post. I think my advice to plunge first and then fire up the saw is bad, even maybe dangerous in this situation. Sorry for the bum steer, read below*

 

[Corwin]

You might want to slide the saw along the Guide Rail with the blade up and power off just to assure yourself that the saw is set properly on the Guide Rail.  And since you have just made a cut, make sure the Guide Rail and underside of saw are free of any sawdust that might throw things off.

Better luck next time,
Corwin

 

[Tinker]

I gouged my guide rail the very first time i used my ATF 55.  A couple of fancy gouges in the to, a little cut into the edge rubber.  The guide rail is still quite usable and i used it all the time until i got one of the newer rails with the two T-slots in the top. 

Even tho I don't use the damaged rail except as a second rail for longer cuts (the old will mate to the new), when it is not in use, I hang it where it is in full view as a reminder.

The cause of my damaging cut: Improper proceedure making the plunge cut.  I tried raising the saw plate before dropping the saw into the cut.  That might have been ok, except i depressed the power switch BEFORE dropping the plate back down onto the rail.  Quite exciting stuff.

I would guess that in removing the saw and then resetting, you may have not properly lined up the rail to the cut and as you lowered the saw, you may not have lowered it properly.  Even tho the TS and guide rails make an almost fool proof combination, there are probably many ways for a fool to screw up.  The consolation is that if the saw does kick back, by the time it becomes airborne, the blade becomes safely tucked away, even tho some damage can ocurr before the saw does become airborne
Tinker

 

[ccmviking]

I believe is caused by the cutting member moving under the rail.  I've had it happen to me on small stock if I'm plunging into it.  If It moves it's as if you are high speed plunging and will bind up the teeth into the wood.  If I have to re-cut something like that I will back up and make sure the blade fits into the already cut kerf, will get the saw up to speed, slowly plunge into the kerf, and then slowly proceed into the wood that still needs to be cut.

Chris...

 

[Brice Burrell]

To add to what has already been said.

  BC, there are a couple of things that I think that my have contributed to your incident. The first thing I mention is I don't like the idea of using 2x4s to cut on top of. 2xs are never flat making a poor surface, if your stock moves during the cut you are going to have problems.  What can happen is the warped 2x gets pressed down flat as you are cutting, as soon as relive some of that pressure the twist can cause the work piece to move, rock or twist a little. This in turn can bind the blade between the work and the cutoff, kick back. I don't know if that was the problem here. Solution, use foam or MDF to cut on top of, something you know will sit flat.

 Since you said you joined two rails together, I don't think guide rail length was the problem. However, I'd like to offer my opinion about guide rails length. When I'm want to make a cut I choose a guide rail long enough to run the full length of the stock with ideally about 14" hanging over each end. This allows the saw to be started without having to be plunged into the work piece, and enough length to complete the cut on the other end. It's tempting to use the guide rail you already have out ever though it is a little short, don't do it. Get a longer one  or another one to join to it so you don't end with the last little bit of the piece uncut. And that brings my to the real culprit, that last tiny amount left uncut. We can get into trouble in two ways. The trouble starts because now we are in a hurry to make up for our mistake of leaving that little bit uncut.  The first, you know you misses the end as you are cutting, so you try to go backwards to finish the cut. Well the saw doesn't like that, the rotation of the blade can cause kickback. The second is your problem, the saw not being fully seated in the guide rail, same thing happens, the blade throws the saw out of the cut (kickback). Again, the issue here is always rushing your work or being distracted be your mistake.

  I think that addresses what could have been your problems, I'll add one more thing to be careful of. Cutting warped, or twisted stock. This is a great way to bind the blade and getting fierce kickback. Some tips to help prevent kickback, don't put yourself in a situation where you know if can happen, da. Being prepared for kickback is the best way to eliminate it. Hang on to the saw with a sense of purpose. Not the a death grip, but in a way that in kickback wants to happen you are ready for it.

Good luck.

 

[BC6738F5BCE98B4]

Thanks to all.

I intend to copy all of your responces, cut and paste into a word processor and distill the advice into (hopefully) less than a half dozen BLACK LETTER rules for future use.  I have such sheets for other tools and am consistently surprized (pleasantly) at how much trouble they keep me out of.

 

[Bill in seattle]

Bc,
As a veteran rail gouger myself, the # 1 thing I see that people do to make the saw kick back and rabbit track across the rail is not let the blade get up to full speed before plunging or moving into the workpiece. the slow start takes a second or two and if you start the blade into the piece too soon a tooth catches and kicks the saw back. your reaction time is not fast enough to stop it. I show this and a bunged up rail to everyone that picks up a saw from me to empathize this.
The other most common reason so far is setting the blade depth too deep for what your cutting . This is a a plunge saw and  has a spring loaded return. When the blade is too deep and you plunge into a cut, right after the blade breaks thru the workpiece ,the spinning blades front edge has a tendency to grab the workpiece and slam the back of the saw down because of excess depth. It moves the saw just enough backwards, thus lifting the front enough to catch the blade on a slight angle and cause a kickback. It happens so fast but I have watched it several times when someone else has been cutting, as well as to myself. In addition, the blades spinning direction is ccw and as it starts to contact the material it will naturally want to go backwards.
If you are going to make plunge cuts in material, the correct way is to use a limit stop (pt# 491582 and  it comes with the saw,as well as being called a kickback preventer  in the catalog ) on the rail and to start with the saw against it so it cannot make the creep backwards. There are two marks on the saws cover that reference where the blade will cut at full plunge. One for the rear and one for the front. use these points to set the limit stops. Some people can hold it tight but it can be very risky. Preventing backwards movement is the best way to prevent kickback.

For normal cutting your blade depth should only be set to approximately 1/2 the carbide tooth depth protruding below the work piece. If you are cutting say, 18mm material and you have the depth set to like 40mm this is a perfect setup for kickback when starting the blade into the material close to the end or plunging. Only add 5mm for the rail and about 3-5 mm for the blades tooth depth. this should be ideal.

The rails are tough, clean any burrs away and make smooth. You may have to readjust the splinterguard, and unless you bent the rail you should be fine. I have plunged, gouged, routed an dinged most all my rails and as long as they guide strait with no hiccups I just consider them well seasoned.

You could check your blade by making a deep cut on a piece thick wood and look at the finish of the cut. If it is clean and smooth your probably fine. If it is scalloped or rough, unplug the saw ,set the blade depth to max, turn it upside down with the blade plunged, and spin the blade by hand. With a keen eye look at the teeth in reference to a point on the base. You could tape a block to the base at tooth point and watch the blade/teeth as you spin it. You might be able to see a warp or a bent tooth. If it is Just get a new blade. Most places will charge as much to resharpen and fix it as a new one. Keep the old one for cutting up non important stuff thou it may affect your guide line.

Using a rail that extends both ends of the piece your cutting by at least the length of what ever saw base your using will help make sure that you start and finish you cuts with the best results is the first choice. If not you have to be more careful on your placement and how you start and stop.
hope this helps a little,
Bill

 

[chughes]

  Bill is right.  As long as the rail is straight only two other things to check are, your rubber splinter guard and make sure the track the saw mates with is in good form.  Those guys at Festool think of everything.  That scar adds character and will be a good reminder of what can go wrong.  One other thing that could have caused binding when you re-inserted your saw blade is, your riving knife that keeps tension of the blade follows the plunge. Just for your own awareness watch the knife as you drop a plunge.  See where the knife is in relation to the blade.  That being said, all of the other observations situations I've encountered as well ( I have a lot of dings)..