Below you will see a pic of a dead 1/4″ straight router bit. I was trying to slightly widen a through slot in a piece of 5/8″ oak when I got the feed direction wrong and got “router kickback.” Scared the daylights out of me, but no bodily harm done. Then I saw the bit, one edge fractured badly.
Question is: Is that fracture to be expected with such a mistep, or was this a bad bit? It’s a Rockler bit I’ve had around for awhile, but had never used, so it was sharp. Or, was something else wrong, bit speed, whatever?
forestgirl — you can take the girl out of the forest, but you can’t take the forest out of the girl 😉
Replies
PS: In case it isn't obvious, I was performing this operation on a router table.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
I had the same thing happen a few years ago. I took it back to where I bought it and the gave me a free replacement. The little piece flew out and hit me in the chest. Luckily I was wearing a leather apron.Scott C. Frankland
Newfoundland Wood Worker
Gives new meaning to the term tatoo, doesn't it. I'm just glad I'm religious about wearing my safety glasses. Thanks for the info Scott.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Forest Girl,
No, this is not normal. I've abused my router bits without having them chip on me. This is only my opinion, but I have two suggestions: (1) Don't use Rockler bits. They tend to get pretty bad reviews generally. Please don't take this as a criticism. When I first started woodworking, I bought Harbor Freight bits! You can buy bits from Home Depot (Oldham Viper) which are miles ahead of Rockler. (2) Think of your router bits as disposables. If you've been getting heavy usage from a straight bit for a year, consider that it's time to toss it.
Hope this helps!
Hi Matt. This is the only Rockler bit I've ever purchased. All my other bits are either Freud, CMT or Jesada. Guess this little incident will prevent me from ever buying another Rockler -- occasionally I go over to their store for a speciality item, it's easy to get drawwwwnnnnn over to the router bit section. Thanks for your insights.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
How deep a cut were you taking? Maybe the bit was undersized for the job. Who knows but thats why I only use bits from manufacturers that I trust. Who is the manufacturer of the Rockler bit. ertainly not Rockler. just my opinion Darkworksite4: When the job is to small for everyone else, Its just about right for me"
Hi Ron, in this particular instance I wasn't exactly "taking a cut" but rather widening an already-made through-slot in the wood by just a tad. That's what got me in trouble, since on a very small scale I was routing inside a workpiece rather than on the outside edge, and forgot that I needed to change the feed direction when doing that.
The slot was 1/4"W x 1.5" long, and I just needed to add a tiny fraction to the 1/4" width. Live and learn.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
My students tend to make the same mistake frequently. I make it once every ten years or so. It's a hard concept to grasp, I guess. By feeding the wrong way to trim the inside edge of a slot, the router start to "climb", and pull the wood into it. But since the wood was between the bit and the fence, and the climbing bit didn't have enough chance to remove it, there came to be no space for the bit, and the wood edge or the wood had to give. In your case the bit lost.
I'm glad you survived, ForestGirl. Now you're much less likely to make the same mistake again. Had you perished, the lesson would have been lost. ;-)
Dave B.
The kickback, not the breakage is a common problem when making deep plunge cuts. Especially so with straight bits. That's why I prefer spiral bits, there's way less edge exposed to grab and dig in.John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
I'm not surprised that your bit shattered like that I have seen it before usually in hard wood when the router or the wood in this case gets away from you. I use Ocemco replacable tip bits a lot and have had them fail on occasion just as you described. I'm not sure that I would condemn Rockler bits out of hand for this type of failure I believe it was the process that caused the problem. Carbide is hard and that equates to brittle- one should always remember that. I am actually somewhat amazed that we don't see these types of problems more often talked about here. Oh well Joe
Carbide is brittle so I expect that during the misshap the bit got "slammed" just right to cause it to break.
A hard lesson to learn about feed direction I know. Have done it myself ONCE and that's enough! Kick-back can be brutal. Let us all be careful and try to expect the unexpected.
I too buy Jasada and CMT bits. They are the best as far as I am concerned. I once dropped a bit, broke it, told Jasada about it and they replaced it, no questins asked.
FG,
I too have had problems with Rockler bits. Once I had taken the bit straight from the package, cleaned of the protective coating, chucked it up, and went to routing. After 6" of use, the guide bearing loosened up and started a terrible vibration. I learned from that experience to always tighten up the set collar on a bearing-over bit.
-Del
Hi Girl:
Judging from the shape of the carbide breakout, it looks to me like you took a whole face cut in an already exiting slot. That sounds real dangerous to me. Even when you're only "taking off a little" you still need to do stepped cuts. My view is that what you did was almost guaranteed to happen.
The safer way would have been to clamp the work and use a jig. Glad to hear you didn't get hurt.
Dave
Router bits are perishable tooling. The mishap you described will make them perish more quickly. Just replace the bit. When I still used electric tools I eventually had my entire router bit inventory exclusively in CMT bits.
Edited 7/12/2002 3:02:25 PM ET by CHASSTANFORD
"Just replace the bit" Well, yeah, don't see many options outside of that, LOL. The reason I posted this question was to get some info on how easily fractured they are in general. Given the price of bits, there's no doubt I will continue on my current path of buying only Freud, CMT and Jesada. forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
forest girl, you might want to try taking a trip down to a machinists supply house. i have found that center cutting endmills make incredible router bits. not only do you have the helical flutes, you can get them in much better grades of carbide than woodworking bits, and they're usually the same price or less when compared to a straight router bit.
Thanks for the tip Andrew! I'm kinda out in the sticks here, but I have a couple of catalogs that might carry 'em, so I'll take a look.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
If you don't find them in your catalogs, call MSC at (800)645-7270 and request a free catalog. The 98/99 catalog - the latest one I have - has 142 pages of end mills. Of course not all of them are suitable for use in a router. :)
If anyone is interested the MSC (end mills) website and Jesada (router bits) websites shortcuts are below.
http://www.mscdirect.com/IWCatSectionView.process?Merchant_Id=1&Section_Id=708
http://iseek.com/omnicat5/index.php?cat_id=0
Thanks for the tip on MSC, any other tips on using end mills versus router bits?
>> ... any other tips ...
Probably nothing you didn't already know. :) Any spiral fluted tool encounters forces that tend to pull it out of the collet. (Think of the bit as a big screw.) So make sure the collet is in good condition, the collet and the bit are scrupulously clean, and the collet is well tightened. Take small bites. If the depth is critical, stop and check it occasionally.
HiYa F_G
Sorry to read about your routing crisis but glad to read you are safe,That kind of thing happens sooooooooo fast.So this brings me to a question I was going to post tonight .Yesterday we picked up a round butcher block table top that needs to be cut down,it belongs to the daughter of a old friend of my parents so it one of those jobs (ever been there). So this table is 54" in Diameter and it needs to be cut down to 48". Instead of using a jigsaw on this beast I thought of the plunge router with a circle guide .This top is 2 1/4 thick so I will need to take a couple of passes, at least, So heres the dumb question; what is the right direction. I am only going to get one shot at this so I would like to be safe and end up with a slightly smaller table.
If the Viper bits at Home-Depot are better than Rockler bits YEEeeeeeow what does that say about Rockler. I have mostly P-C bits with Jesda and CMT. Just ordered a Bosch straight cut bit for the table, it has a 2 1/4 max cutting depth it is 4 5/8 long and has a 5/8 diameter cut, its a big ol bad boy. Have a great (safe) weekend Rick.....
Cut it close with a jigsaw, (or bandsaw if available and support is to hand) and follow up with a trammel and router working anti-clockwise with the biggest diameter bit you've got operating at a fairly slow RPM. 32 mm diameter bits, or 1-1/8" with 1/2" shanks are common enough, and if you're worried about spelch or tearing out on the short grain, do a careful climb cut or two close to the mark, and finish with a very, very light shaving rotating the the router anti-clockwise off the trammel. And then smooth it with hand tools such as planes, spokeshaves, scrapers, and sandpaper. Slainte, RJ.
RJFurniture
Edited 7/12/2002 11:30:02 PM ET by Sgian Dubh
Thank you RJ.
Two more quick questions for you before I move in on this beast. The jigsaw is going to do the brunt of the cutting while the plunge router is coming in second to do a pre-finish, sort of tuning the circle followed by sanders etc.Were do you get a 1 1/8 diameter bit the largest I have found is 5/8 dia. by 4 3/8 long, this is what I am using. Also when you say slow RPM what are you meaning. The Makita 3 1/4 hp is a older model and is single speed, this is the one I've made the jig for. It mounts to the base and can be set to cut (or trim ) up to a 5' diameter circle. I also have a Fien 3 1/4 hp. variable speed, It sounds like this is the animal to use on this project.Guess that was 3 quick questions. Living out in the Boons is really tough sometimes, if it weren't for mail order I would be screwed. Thank you again for your fine advice. Very helpful. Rick...............
AD, all the,-- no, let's not say all-- but all the router bit manufacturing specialists that I come across sell a wide range of bits, from the common or garden straight plunge bit to very fancy matching bits for door construction, and other operations. Whiteside, Amana, Freud in the US are three names that come readily to mind that supply a comprehensive range, and they all have websites, I think. In the UK, Trend is a name that springs to mind. Any one of these companies-- and others-- haves large diameter bits, and large diameter bits tend to work better for trimming profiles than small diameter bits, whether they be pattern cutting bits or simple straight bits. The better results of large diameter bits is to do with the action, the angle of attack of the cutting edge, the size of the shank resulting in stiffness, and the circumferential speed, and more engineering stuff that I'm not good at explaining. The bits aren't cheap, but they'll do a lot of work between sharpenings. They should be run at about 12,000- 15,000 rpm if memory serves me right, and this can be set on your variable speed router. A good quality big diameter pattern cutting bit-- with bearing-- might cost in excess of US$60.
The Fein you have sounds like the best tool for a large diameter bit-- you benefit from a slower (bit) circumferential speed for large diameter bits to reduce, amongst other things, excessive burning. If you cut close to the line with your jigsaw, I'd expect you to be able to get a good result from final very light trimming anti clockwise using a trammel with your 3+ hp Fein and large diameter bit in one pass, but you always have to be wary of short grain, so a bit of reading of the grain and some climb cutting might be in order. There is always the chance of failure. Give it a whirl, and best of luck. Slainte, RJ.RJFurniture
Hi Rick, best of luck with the project, and please be careful! (I still get goose-bumps thinking about that jointer accident you had). Those big bits can be pretty dangerous. According to Patrick Spielman's Router Handbook, the following speeds are (generally) recomended, and might be modified depending on many factors including type of material being cut, number of flutes and sharpess, HP of router:
Up to 1" diameter 22,000-24,000 rpm
1.25" to 2" diameter 18,000 rpm
2.25" to 2.5" diameter 16,000 rpm
2.5" to 3.5" diameter 8,000 - 12,000 rpm
Your best buy on the big bit might be Jesada (from their web site, jesada.com).
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
HiYa F_G................
I am going to check with Jesda tonight and see what they have (could be trouble). The table project went off with out incident, I was however thinking about you while I was hanging on to 3 1/4 hp. of screaming router. I received some great advice here this weekend and followed it to the letter and all went well. I have done tons of routing for trim and some plunge routing but this is the first time I used a straight cut bit for cutting. Pre-cutting with the jig saw was the answer, guess that practice is common but being as though it was my first time it was new but very rewarding. I felt very much the same way after I ran my finger through the jointer. I threw a blanket over it for a couple of days,then went back cleaned it up and ran a board over it ( BIG board) and moved on. Kinda like gettin back on the horse again.
Have a great day.............Rick.
Congrats Rick on doing such a great job on the table top! Know what you mean about the first time being rewarding. Every time I follow and succeed in a process that zillions of others have done before me, I feel great. It's such a surprise when nothing goes wrong.
I've got to call Jesada tomorrow morning. Pulled out my new rabetting set, and wouldn'tcha know it the one bearing that I wanted to use was kerfluuey -- center of the bearing came out.
So, I decided to rabbet on the tablesaw, which was ok except I forgot that I hadn't wanted to do the rabbet all the way from end-to-end of the workpieces (so the tablesaw wasn't such a good idea after all). So now my box will go from being butt-joined to being mitered, and a bit smaller over all. But then, I need a zero-clearance throatplate for 45-degree miters, so I've got to make that first. But then I've not had dinner or lunch today, and there's no food in the house, so I guess I'll go to the grocery store instead. Sheesh!
On a positive note, I did get most of one of those giant oak cabinet sides stripped this afternoon. forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Hi A, Can you support the top (in a way that it won't move), then build a circular track jig for your band saw? Move the band saw around the top instead of moving top. I know this is time consuming, but with only one shot at it this may decrease the possiblity of error. I have done this for a 5' diameter and it worked better than I had envisioned, and with my childish imagination that is saying somthing!
FG
The other day I was cleaning up my tools. I looked at the router bits under a lens. Some of these are fairly old bits. Several had bits of carbide missing. I pitched them and am slowly replacing them with new ones.
These things wear out and warrant close inspection.
Typically I also wear a leather apron and lexan face shield when routing.
Frank
I've been converted to a leather-apron fan I think. Gonna start looking for one right away, 'cause I really don't want to have a piece of carbide decorating my midriff!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
HiYa F_G
If my memory serves me correctly I think WOODCRAFT has some nice Leather-Apron's. I at this time do not have one but after reading all these posts it is begining to sound like a pretty good idea. I ran about 200 ft. of Hickory picture molding through my Bell-Saw today,That wood is nasty................Would have been a good day for a leather shop apron. All went well. Be safe. Rick...................
Thanks for the tip Rick! I saw you got your pics on today -- nice job!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Hey J, That bit reminds me of a spouse! Never, never ask them to do just a little bit more! LOL. Similar situation happened to me with a 1/4" spiral from MLCS, except that it broke the bottom 3/16" off in pine (I was only trying a 3/8" plunge). After a change of pants and a mild sedative for my heart, I quit for the day. HA! Thank God you are okay.
B.
Dear forest girl:
The short answer is NO, that should not have happened. I would fully expect Rockler to make good on your "exploding" router bit.
However, There are many pertinent details that you left out of your explanation. The most salient of which is what mechanism did you have in place to limit depth of cut? Was it the router table's fence, a template, or some kind of stop? If you had no such mechanism then might I say that you are a very lucky girl to still be in possession of all ten digits. Given that you were working in 5/8 inch thick oak, and that the bit was only 1/4", I would recommend that your absolute maximum depth of cut be no more than 1/16". Actually 1/32" would be safer, easier on your tools, and yield a smoother cut. This is especially true if you are cutting across end grain. Straight router bits of the type you were using are especially prone to grabbing and digging in when cutting across end grain.
If perchance you had no cut limiting mechanism set up for your cut then count your blessings, do not bother the good folks at Rockler, and NEVER, EVER DO THAT AGAIN.
Edited 7/13/2002 10:14:38 PM ET by KEITHL61
Keith, I appreciate your concern. I can't tell from your response above whether you fully realize I was slightly (read: smidge, fraction-of-a-fraction) enlarging a through slot that was already complete (and, I'll mention, I approached that task in several increments). In other words, the through slot was 1/4" across, and I needed to make it about, say, 9/32.
I was using my fence (I always either have a fence or am using a bearing guided bit when using the table. No end-grain involved since the slot was parallel to the long side of the workpiece (was about 1.25" long).
As "none" said above in #15, I probably should have come up through the slot a little at a time instead of trying to face off the whole thing at once, with such a small-diameter bit, and of course the proper feed direction was obviously crucial. forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Forest Girl:
In previous comments relating to bandsaw blades, I talk about the relationship between bite, feed speed, blade speed and pitch. More or less the same principles apply to this situation except that blade speed becomes rim speed (Sgian's circumferential speed) and pitch is the circumference distance divided by the number of cutting edges.
Somehow, if I can repeat this fundamental information about wood machining, individuals will begin to at least get some intuitive feel for this relationship (not a criticism of you). At some point in time, the bit took too large a bite and like all other woodworking tools, dove into the wood. The breakage occurred because the machining forces exceeded the strength of the tooling. It happens with some regularity in large primary processing mills that utilized band saws. If a sawyer overfeeds a saw, the sawyer can break off several dozen teeth from the blade (which is pretty amazing when you consider that the tooth spacing is 2 inches and the tooth height is 1.25 inches).
When I think about rotary tooling (shaper cutters and router bits), I am generally concerned with the number of knife marks per inch. Knife marks per inch is an indicator of surface quaility. Dimension lumber is likely to have 4 to 6 marks per inch going to as high as 40+ for furniture grade moulding. Given rotary tooling, knive marks per inch are a function of RPM, the number of knives, and the feed rate. As with bandsaw teeth, more is not necessarily better for multiple reasons. As with bandsaws, rubbing generates heat which contributes to excessive tool wear (dulling). For small bits like the one you showed, the heat goes into the shaft and with increased heat, the shaft becomes weaker and more susceptible to breakage especially when you overfeed the bit. And finally, too slow a feed, too rapid of RPM and machine burn becomes more and more likely.
I realize that given the RPM of routers, I will never be able to feed the stock fast enough to get opportune knive marks per inch so the first thing I do is slow the router down as much as possible. As I have said in other posts, I rarely cut with any bit at an RPM rate >10,000. I've thought about getting one of those rheostatic controls for routers that further reduce RPM's.
Whenever you have cutters spinning as fast as they do, it is truly impossible to determine failure cause. I have noticed on different router bits that have broken that there might have been a serious flaw created during manufacturing. In your instance the carbide insert and the metal shaft may have been heated or cooled improperly so that stress and/or fracture lines were created in the cabide. As such, the bit could have been an accident waiting to happen. The other problem that I attribute with broken router bits is martensite which is a form of the steel that is weak and brittle and results from improper heating and cooling or with improper tempering/annealing. For example I got a bunch of bits from the same source that broke just up the shaft from the end of the carbide insert. They were 0.5" shaft bits with a single 3/8" flute. I can only conclude that in brazing the carbide, the thicker shaft was not heated properly and at some point of interface between the thinner cutting end and the thicker shaft, martensite was formed. I'd cut about 5 feet of material and the bit would break off.
I hope this helps!
This forum post is now archived. Commenting has been disabled