Scary moment, router cutter snaps

[Sawyer]

Clearly I am extremely glad the cutter did not have the scope to take off into the air at a possibly deadly velocity. Having gathered my composure I wanted to get some thoughts on the cause. My initial guess is that by cutting a groove the same depth as the router cutter is wide I pushing the cutter way too hard. Should this have been done in 2 or even 3 passes?

Terry.

These small ones break easily, even Trend ones. You need to do a series of very light cuts. I don't think there's too much danger from a flying fragment however. It it's just spinning on a small axis, the tip seems to just stop where it is. All the same, safety specs are advisable for all routing operations.

 

[SteveF]

this any good?

http://www.axminster.co.uk/axcaliber-tw ... m-ax807619

Steve

 

[mooed]

I've had two scary moments with a router, one also involved a snapped bit. A 1/4 inch 6mm straight bit, also from a Trend set that came free with the router (a T4, I love those even though on my third). I was rebating a slot for a drawer bottom, it should have been the second last pass strictly speaking but it was only 4mm so it should be safe so thought to do it in one last pass. I was coming up to a big dense knot so slowed down ready to counteract any bulging, I don't know what happened but next thing I know is the bit had cut though side of the wood and snapped, the end hit my safety specs. The specs were only cheap JSP ones but apart from a chip they did the job, left a big enough chip to render them useless , I used to be a bit lax at times with eye protection but not since then.

The scariest moment was when I first routed to a template alone. I'd watch it been done a few times and when I was first did it someone started me off. First time solo I moved the wood and template to the router and nearly had a heart attack as a huge thunk sounded as the workpiece was flung out of my hand. I never noticed and no one ever mentioned the need to lead in. I had to sit down for 30 mins to recover.

 

[geoffshep]

I had the same breakage, with the same cutter, from the same set. Since it was the first outing for it, I contacted Trend who replaced the cutter but also gave the following advice:

Where possible in future, you may consider getting this size tool on a 1/4'' shank, as it is inherently stronger. The reason being, it has undergone less machining processes during manufacture.

We have higher grade cutters of this design of tool, however this design of cutter can struggle on abrasive materials, for the reason I mentioned.

Trend ref: S55/2X1/4STC may be a better choice for your application.

 

[Wizard9999]

I had the same breakage, with the same cutter, from the same set. Since it was the first outing for it, I contacted Trend who replaced the cutter but also gave the following advice:

Where possible in future, you may consider getting this size tool on a 1/4'' shank, as it is inherently stronger. The reason being, it has undergone less machining processes during manufacture.

We have higher grade cutters of this design of tool, however this design of cutter can struggle on abrasive materials, for the reason I mentioned.

Trend ref: S55/2X1/4STC may be a better choice for your application.

Amusing that they put it into the set and then tell you that you should maybe get a different tool, how does that work?

Terry.

 

[Mike Jordan]

As I mentioned earlier the smaller cutters seem to be weakest at the point where the TCT tips are brazed to the base material as shown in the above photo. Solid carbide is much better.

 

[Eric The Viking]

I read Mooed's comment with disappointment.

Up to that point I had assumed that if a 6mm cutter broke it probably hadn't got enough kinetic energy to be really dangerous. But that could have been a serious eye injury, obviously. It just shows you can't be too careful.

That said, the big panel raisers, such as the ones Steve is presently using, need real respect. Because of the need for stiffness at the outer ends of the cutters, and the modern anti-kickback design* there is a lot of mass whizzing round fast at the circumference, and therefore huge amounts of kinetic energy, in comparison to a 1/4" straight cutter.

If Steve is panel raising using the cutter I think he is, then at 11000 rpm (the recommended maximum speed), the wingtips are doing roughly 107mph**. That's a bit less than half that of a slow musket ball, I think, but still somewhat damaging.

Hmm.

E.
*also supposed to limit how far a finger can get in, as if that makes much difference!
**Someone check my calc please - diameter is around 76mm, max speed 11000 RPM.

 

[Racers]

Makes moulding planes look much more attractive.

Pete

 

[AJB Temple]

This has been an illuminating thread. I have been using Trend cutters as will (mostly pro ones), but I will be careful with the others. I do buy the point that a reduced size cutter is better on a 1/4" shank due to less manufacturing stresses - that seems to make sense to me. I have never had a router cutter break in I think 30 years of using routers but the experience above is thought provoking. I will be more diligent in wearing safety glasses (I usually do anyway - but occasionally lapse for a quick job).

 

[Wizard9999]

Thanks all, really helpful comments and I hope my posting of my incident will be helpful to others.

I have just placed an order with Wealden for a replacement cutter, I went for the solid carbide version. None the less I will be making smaller cuts in future.

But hey, there was a silver lining as my order of the replacement cutter gave me the opportunity to buy myself a few other bits and pieces :lol:

Thanks again to everyone for the helpful advice and guidance.

Terry.

 

[Adam9453]

This topic has certainly been thought provoking and I was browsing through wealdens range of solid carbide spiral cutters. The bit I was surprised to read is that you should expect a feed rate of 6-10m per minute and that a typical cause of failure is insufficient feed rate. This surprised me as I would have expected failure because of too fast a feed rate. 6-10m a minute means pushing through a half metre length very quickly in my opinion.
What are your thoughts/experience on this guys?

 

[skipdiver]

This topic has certainly been thought provoking and I was browsing through wealdens range of solid carbide spiral cutters. The bit I was surprised to read is that you should expect a feed rate of 6-10m per minute and that a typical cause of failure is insufficient feed rate. This surprised me as I would have expected failure because of too fast a feed rate. 6-10m a minute means pushing through a half metre length very quickly in my opinion.
What are your thoughts/experience on this guys?

I think this only applies to the solid carbide spiral cutters, which are the ones used in industry i believe for CNC machines and the like. They also stay sharp much longer, which is why they are more expensive but cheaper in the long run because of the greater speeds the work can be fed at and also the downtime of changing bits.

 

[mooed]

I read Mooed's comment with disappointment.

Up to that point I had assumed that if a 6mm cutter broke it probably hadn't got enough kinetic energy to be really dangerous. But that could have been a serious eye injury, obviously. It just shows you can't be too careful.

I've had a couple of other small bits break and they've just been left embedded in the work. When this happened, the bit came out of the rebate though the bottom of the drawer side , it then was cutting at the full depth of the rebate, it looked like it may have snapped as it was coming out so nothing to capture it, I've probably tilted the router forward a little as it jolter out.

 

[MattRoberts]

This has been an illuminating thread. I have been using Trend cutters as will (mostly pro ones), but I will be careful with the others. I do buy the point that a reduced size cutter is better on a 1/4" shank due to less manufacturing stresses - that seems to make sense to me. I have never had a router cutter break in I think 30 years of using routers but the experience above is thought provoking. I will be more diligent in wearing safety glasses (I usually do anyway - but occasionally lapse for a quick job).

Quick tip - buy some really lightweight safety glasses. If they're so light that you hardly know they're there, you shouldn't need to ever take them off