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I used a new ½” shank Amana 2 ½” flush trim bit with lower bearing to route some Cocobolo (hardwood from Mexico). I had a pattern piece with 2 pieces of ½” Cocobolo attached using double sided tape. I band sawed the pieces as close to the finish line as possible. During the flush trim routing on the end grain portion of the pieces, the bit grabbed the end grain and literally ripped the assembly out of my hands and threw it across the shop. Luckily, no one was hurt. I became a little more wary of using this procedure. Maybe it was my setup. I mounted my Porter Cable router in a table and had the bit protrude until the bearing was resting on the pattern piece (to clarify, the layer was hardwood, hardwood, pattern piece on top). I didn’t use a fence rather just fed the assembly into the bit until the pattern piece touched the bearing. All went fine until I hit the end grain. Wow, that was scary. My question is…was my setup wrong or are some hardwoods just not conducive to routing?

End grain can be difficult no matter what kind of wood you are talking about. You are working with one of the harder or hard woods.

I am thankful that you were in no way physically hurt.

Are you certain that you were not attempting a climb cut (working against the rotation of the bit).

You did not say how wide the pieces you were routing are.
Freehand routing end grain on narrow pieces is not recommended. Use a miter gauge or a backer board which will hold the piece steady with the backer board riding against the fence. My hunch is that you lost control when the piece got cocked slightly if you were routing freehand. If the end grain piece is not a straight line cut and must be routed freehand use some grip assist such as the SS hold downs that are included with the jointer or make similar ones yourself. End grain routing of the piece should be done first and then the straight grain. The tear out of the end grain will generally be removed when the straight grain (edge grain) is routed. Firm gripping and securing of the workpiece is essantial in any woodworkiing operation.
Bill V

My guess is that you were maybe routing into or against the grain. Especially on a rounded piece you have to watch the grain and turn the piece over at a certain point so as not to be going against the grain. This will also help reduce tear-out on the ends. On a table, using no fence, you also should be using a starter pin to help safely feed the piece into the bit without it grabbing the piece out of your hand. After initial contact you can cease using the starter pin. It's just for initial contact (starter).

curiousgeorge wrote:My guess is that you were maybe routing into or against the grain. Especially on a rounded piece you have to watch the grain and turn the piece over at a certain point so as not to be going against the grain. This will also help reduce tear-out on the ends. On a table, using no fence, you also should be using a starter pin to help safely feed the piece into the bit without it grabbing the piece out of your hand. After initial contact you can cease using the starter pin. It's just for initial contact (starter).

He said he was pattern routing. In this case it would not be possible to turn the piece over. I do pattern routing quite a bit and here is my method.

First I use a spiral flush trim bit whenever possible; these cut cleaner and have less tendency to grab.

I would also made sure I had trimmed the blank to within 1/8" of the pattern.

I ALWAYS plan my cut with the machine off and check to see where my hands are going to be during the cut. If I feel uncomfortable, I will devise a holder or some other way to safely hold the piece.

I use a starter pin when possible to help control the piece for the initial contact.

Once the cut is started if anything looks or sounds wrong; stop and re-examine your set-up.

tdubnik is right on the mark. What I think may have happened is that some of your double sided tape failed and suddenly you were trimming more material than you had planned. Other than that you seemed to be dong it pretty well. You might try trimming one piece at a time though.

Merry Christmas

Paul M

This type of question is a common occurrence on the TDPRI.com Home Depot forum for DIY guitar builders. The common answer is: a router bit is a rotary planer. It can only take off a very small shaving safely. I had a very similar experience with a brand-new router bit that a friend wanted to use to take off about 1/8" in one pass on rock hard maple neck blank. It grabbed the maple at the end grain and split it in half the whole length of neck blank. After that experience I use a band saw and get within 1/16" of the line and use a dull bit to shave off part of the height of the blank (3/8" max. with a 1" long bit) and make several passes to get the 1" total thickness shaved down. If you have a Robo-Sander (http://www.luthiersfriend.com/) or a Sur-Form Microplane (http://us.microplane.com/rotaryshaper.aspx) rotary planer to take it as close as possible then you could safely use a full-height router bit. Some of the builders don't risk use of router if they have the 2 drill press mounted tools suggested above.

BTW: Never router uphill.

I think the problem was the router bit!

Your wood is hardwood by definition but it is also HARD wood in fact.
A spiral cutter would have probably eliminated your problem because spiral cutters by design take a smaller cut and their shearing action tends to shear the cross grain instead of tearing it.

Also I would say you should be using a good quality spiral cutter. I prefer Infinity Tools router bits for any problem wood. For me they have solved so many of my router problems.

Test what I say out get yourself an Infinity Tools spiral flush cutter router bit and using the same setup see if you have the problem.

Ed in Tampa wrote:I think the problem was the router bit!

Your wood is hardwood by definition but it is also HARD wood in fact.
A spiral cutter would have probably eliminated your problem because spiral cutters by design take a smaller cut and their shearing action tends to shear the cross grain instead of tearing it.

Also I would say you should be using a good quality spiral cutter. I prefer Infinity Tools router bits for any problem wood. For me they have solved so many of my router problems.

Test what I say out get yourself an Infinity Tools spiral flush cutter router bit and using the same setup see if you have the problem.

They make 'shaped' spiral bits? Sorry I just always think of router bits as being something other than straight sided.

JPG40504 wrote:They make 'shaped' spiral bits? Sorry I just always think of router bits as being something other than straight sided.

Not sure what you are saying but yes Infinity tools does make spiral shaped router bits. Unlike normal bits with a profile cut in the vertical axis. Infinity does make many of the common profiles in what I would call spiral. In the otherwords the the profile is cut on a angled vertical angle so the bit actually begins the cut at the top or bottom of the profile (depending if it is an upcut or downcut bit) and continues shearing the wood until the profile is complete.

This designed saved my bacon when I was cutting a rather intricate profile in some really hard maple. Every other bit I tried caused chip out, tearing of the grain, catching and etc. The angled profile router bit from infinity cut the profile like butter and I am totally sold on infinity bits.