Broken domino bits, I'm getting frustrated

[endgrain]

I broke my second set of 5mm domino bits this weekend while creating mortices on bamboo. I didn't realize the festool bits were so fragile 
The first one broke with less than 20 plunges, the second with less than 40 plunges. I am sure I did not drop them or hit anything metallic and I believe I know how to handle carbide bits (at least the ones for my router).

Here it is, still embedded in the piece of bamboo I was plunging it in.
[attachthumb=1]

Tip extracted.
[attachthumb=2]

At 33 bucks a pop, this is obviously not going to be sustainable (not to mention the time lost driving to get another one plus the potentially ruined workpiece).

Is there potentially something I am doing wrong (plunging too fast)? I can't believe though that incorrect plunging technique will break the bit.

Does anyone have experience with the CMT bits, do they perform as well or better than the OEM festool domino bits?

 

[woodie]

Two bits in a short period of time does sound like your plunging too fast. I've only had one bit break in 3 years and that was from clipping the tip of screw.

 

[Kev]

Are you using a DC? Debris buildup with the oscillating bit will be a real problem if you are.

 

[tallgrass]

Yea, you should be using vacuum, keeps but cool and keeps chips from clogging.

 

[endgrain]

I always have it connected to my MIDI vac.

 

[tjbnwi]

CMT's are now my go to bit.

Tom

 

[Stephen B]

[size=11pt]

Apart from vac and speed, the other possibility is that Bamboo is known to be very abrasive on saw blades and drill  bits.

But then these are supposed to be high quality cutters, so I am still surprised.

 

[John Bates]

+1 for CMT, then I would say that

 

[ceddy]

Strange indeed, unless you are plugging way to fast then this shouldn't happen. Mind you I don't have experience with bamboo.

 

[ajones]

Interesting to see the damaged bit, hard to work out the issue, it does appear as if the bit is being wound up, and plunge speed could play a part in that.

there is a lot of glue used with bamboo which may be part of the issue..

I would try a much slower plunge speed and see how that went.

 

[Worm Drive]

Bamboo is extremely hard on blades and cutters.

 

[Brice Burrell]

Bamboo is extremely hard on blades and cutters.

Yes, and if you don't take it easy plunging you're far more likely to kill the bit.  This especially true of the 5mm bits.

 

[RKA]

Have you tried plunging slower and in small increments, backing the bit up periodically to allow the chips to clear and prevent the bit from overheating?

Edit:  On second thought, there is a lot of scoring on the shaft of the bit just below the fracture point.  Do you know what that is all about?  Did it happen just before the fracture or just after?  Can you try a different type of wood and see if you get the same result?

 

[grbmds]

Have you called Festool service? I am curious what their response is. There is something unusual and unique (obviously) sinc others have not had the same experirnce with the bits.

 

[Brice Burrell]

Have you called Festool service? I am curious what their response is. There is something unusual and unique (obviously) sinc others have not had the same experirnce with the bits.

If you do a search on here you find this isn't unheard of for 5mm bit.  Hard material coupled with a hasty plunge and the likelihood of broken bit goes way up. 

 

[iamnothim]

Not sure this is covered elsewhere.....
I am a very new Domino user, here's what I've found works best to get a "feel" for the bit and the material.

Just like pointing your index finger forward when using a hand saw, I point my thumb toward the workpiece during the plunge.
This helps me to remember to keep my arm parallel with the plunge and not apply lateral or side to side force.

The image of your broken bit is amazing.  [eek]  I know manufactured bamboo is incredibly hard.... but.

 

[Administrator_JSVN]

I would agree with what others have said. Try slowing your plunge rate. We have customers using the Domino with Ipe and other extremely dense hardwoods. So, I doubt the bamboo is the cause. But, like others, I don't have any experience specifically with using the Domino and bamboo.

Shane

 

[Brice Burrell]

Not sure this is covered elsewhere.....
I am a very new Domino user, here's what I've found works best to get a "feel" for the bit and the material.

Just like pointing your index finger forward when using a hand saw, I point my thumb toward the workpiece during the plunge.
This helps me to remember to keep my arm parallel with the plunge and not apply lateral or side to side force.

The image of your broken bit is amazing.  [eek]  I know manufactured bamboo is incredibly hard.... but.

Think about the forces acting against the tip of the bit that is drilling/routing and oscillating, now add bamboo.

 

[Sparktrician]

Be sure to hold the Domino by the PlugIt connector and DE hose connection.  When you plunge, listen to the motor.  If you're plunging too fast for the material you'll hear the motor slow noticeably.  The right plunge rate is one in which you hear very little change in the motor speed as you plunge. 

 

[bkharman]

I am not buying the bamboo being the main issue. It may very well exasperate the issue but I am with others on this:

Slow down the plunge rate.
And make sure the bit is up to speed before plunging.

I have plunged into ipe and hickory, but with an 8mm bit. Probably put in about 100 mortises and have used the bit elsewhere without issue (or dulling)

Cheers. Bryan.