Broken Router Bit?

[Dave Fifield]

I'm mystified. One of my router bits, a 1/4" spiral up-cut bit with 1/4" shaft, broke right at the base of the spiral in mid-route last night. I was routing a 1/8" deep slot in a piece of birch ply. The ply was pinned hard up against the fence on my router table and I was going slow - there was hardly any vibration. Darned thing just snapped off without any warning.

Why? I'm leaning towards it being a defective bit as I wasn't stressing it at all. Weird.

This is the first bit that's ever broken on me. Are defective bits common? Have any of you had a bit break on you like this before?

Dave F.

[Jim DeLaney]

Was it a solid carbide bit? Most spiral bits are...

Solid carbide bits are very brittle. They can shatter with just a slight 'shock," like hitting a knot.

You said yours broke at the base of the flutes. That's actually just about the weakest spot on it. The cross section of the bit is at its smallest (weakest) there, so that's where they usually break.

And, to answer your question: Yeah, I've broken several of them over the years. Had one come flying out and imbed itself in the adjacent wall. Exciting!

[Mark Hollingsworth]

Dave, I had a two flute carbide 1/4 straight bit do the same thing a couple of weeks ago. I didn't think I was putting much pressure on it either, but sometimes I get to rockin along and don't realize I'm pushing a little harder than I probably should have. Fortunately I had another one so I just put it in and kept going. Mark

[Ian Barley]

Dave

I have little luck with spirals. I now use them only in Cedar and plastics. Like Jim says most are solid carbide and are very brittle. I'm afraid that I hardly ever find that the spiral gives me any advantage that justifies the cost.

[Chris Barton]

I like spirals and carbide but, any 1/4" bit is a little on the fragile side. Stuff happens:confused: .

[Steve Clardy]

!/4 and 3/8 spirals. Have broke a lot of them. HSS, solid carbide.
I have a 7hp overhead router that I run 3/8 spirals in. It eats them like candy.

[Dave Fifield]

Thanks for your replies guys. Yes, it was a solid carbide bit. I seem to recall it wasn't cheap either. I had another one spare (not sure how/why I ever bought two, but lucky I did!), so work continues....

I will proceed with caution.

Cheers,
Dave F.

[Ralph Barhorst]

I have had this problem with 1/4" spiral bits. I use solid carbide bits that I bid on at the notorious web site. These are actually end mills. I use 1/4", 3/8" and 1/2" end mills. I just bought a 1/2" spiral bit yesterday. It is 3-1/4" long with 1-3/8" LOC and 2 flutes. I paid $4.95 for it with an additional $3.00 for shipping.

The cost is low and the performance is great.

[Cliff Rohrabacher]

Carbide can also fail when subjected to vibtration. The high freq finds the internal stresses and relieve's 'em by breaking the bit.

[Jerry Strojny]

I was just about ready to throw in the towel on the project. I was at the store 3 times for a stupid 1/4" bit. All three of them broke at the base of the cutters. It is nice to know others eat through them also and it wasn't something that I was doing wrong.

[pat warner]

Common indeed, especially with skinny long bits. A twin flute 1/4 solid carbide spiral has <1/8" web, hardly enough to do much routing without breaking.
An 1/8" deep cut is quite modest, however, and if the cutter was new it should not have failed.
More on cutters? See the Bits link. (http://patwarner.com/routerbits.html)

[Dave Fifield]

Yep, it was a twin flute bit Pat. I (ahem) may have been less than gentle with this bit in the past - it wasn't new. I guess I'll be more kind to my new one.

BTW, nice website Pat....seems you know a thing or two about routers! ;) I'll be exploring it fully this weekend.

Cheers,
Dave F.

[Dick Strauss]

Dave,
I contacted Freud with exactly the same issue on a 1/4" spiral bit. They asked that I send the bit to their QA folks and replaced the bit free of charge. Check with the manufacturers to see if they might be willing to replace it for you given that it doesn't sound like abuse or misuse.

Good luck!