Domino Bit Fracture

[Birdhunter]

My #5 domino bit broke today. I was cutting mortises into 1/2" Baltic birch plywood and the tip of the bit broke off after entering the wood less that 1/8". I somehow started off 2 years ago when I bought the 500 with 2 of the #5 bits so the usage has probably been split between the two. His bit is my most used size.

I've gotten a lot of use from these #5 bits so I am not complaining. I'll buy a replacement Tuesday.

I'm questioning if this bit failure is a common occurance.

 

[mastercabman]

It has happened to me a couple times
I now feed slowly and have been lucky
No problems with the bigger bits

 

[semenza]

  Yes, the 5mm will break on occasion. It is just that they are thinner and can't take the usage as well. They are more likely to break than the larger sizes if something hard is encountered or on a fast plunge  for the same reason. I had one break the corner of the tip once when it ran into a really hard knot in softer surrounding material.

Seth

 

[roblg3]

I've found it common over my decades of tool usage that smaller drill bits, drill tips, router bits (which is pretty much what a domino cutter is) are the easiest to break.  The less mass of metal means a less durable piece.  Just like smaller nails bend easier and thinner screws snap easier...

 

[Stone Message]

Bits can break if you plunge too fast so try reducing this. It is important to give the bit the chance to work, just like any router bit.

Peter

 

[Birdhunter]

I was plunging at the same rate as the last 30 or so mortises I made that day. I think the bit just failed from metal fatigue.

The theory that smaller bits are more fragile makes a lot of sense.

 

[Brice Burrell]

I was plunging at the same rate as the last 30 or so mortises I made that day. I think the bit just failed from metal fatigue.

The theory that smaller bits are more fragile makes a lot of sense.

So basically you're saying you plunged too fast 30 times, no wonder the bit finally broke. [tongue]  All joking aside, plunging too fast was probably the cause.  Once I figured out the correct speed, it was very apparent when I inadvertently had gone too fast after that.  You can hear the Domino strain a little.  Also plunging too fast can cause the mortices to be slightly askew, not parallel. 

 

[Birdhunter]

Metal fatigue is my story and I'm sticking to it

I now have a new #5 and a spare. I also picked up a backup #4.

 

[greg mann]

While baltic birch ply is better than a lot of other ply around it is also possible you encountered an internal ply that was devoid fo glue or was loose in some other fashion, not the whole ply but just in the area of your plunge. A small part of it could then possibly shift once the bit made a space for it to move into. A sudden extra load of a bit of loose ply on one cutting edge could cause trouble. This is just speculation on my part but it is one more possibility to consider.

 

[chippy]

Things I have found that break the bits are ;plunging to fast
and using without dust extraction connected.

 

[NL-mikkla]

I have noticed that when you switch the machine on it is easy to give a bit of a push downwards/inwards causing the bit to touch the wood before getting to full speed.
This has happenend to me few times now.
I really have to be aware of that everytime I switch it on

 

[RMWW]

I had a 5mm domino bit fracture today on some Doug Fir. Went down to Woodcraft to pick up a new one and shelled out the 42 bucks. I was kind of torqued when the salesman suggested I was stabbing the tool in.  I use a slow plunge rate for accuracy so that the machine stays in alignment with my mark.  I think there might be a problem with the forging or fusing of the carbide tip.  Hope this isn't a regular expense after every 400 dominos.

 

[Naildrivingman]

Is it also possible that mortising a highly bidirectional product like Baltic birch puts higher stress than other material?

 

[LDBecker]

I broke a couple of the 5mm bits. The problem turned out to be that I had damaged my Domino 500 by turning the width knob when the machine wasn't on. It did something to some gears inside. Festool repaired it promptly and it's ok now. I couldn't remember making that error, but apparently did. Does your machine sound different?

Baltic birch is pretty dense, too- lots of glue in there, and different directions of wood grain.

 

[tjbnwi]

I had a 5mm domino bit fracture today on some Doug Fir. Went down to Woodcraft to pick up a new one and shelled out the 42 bucks. I was kind of torqued when the salesman suggested I was stabbing the tool in.  I use a slow plunge rate for accuracy so that the machine stays in alignment with my mark.  I think there might be a problem with the forging or fusing of the carbide tip.  Hope this isn't a regular expense after every 400 dominos.

Like any other cutting tool it's a consumable. Think about the load the cutter has been under over the 800 mortises.

I keep extra bits in stock, same as saw blades.

Try the CMT cutters, I've gotten a little more life out of them.

I had one month, when I went through 12-5 mm cutters.

Tom

 

[Birdhunter]

I'm very careful plunging, but still fail short of perfection using either of my Dominos. My #4 and #5 bits are the most frequent casualties. I use a lot of very hard wood, Ipe, ebony, mesquite, hard maple. Mortising end grain into these woods puts a lot of stress on the bit and the Domino.

I think the carbide bits are brazed onto the bit tips. All my bit failures
have been tips coming off. Thus, I keep 2 spares for theses two sizes and one spare for all the larger sizes.