Replies

1. 
   NickC | Feb 10, 2003 10:31pm | #1

   Your instict is correct--you were feeding the stock the wrong direction. On a router table you feed from right to left. It's possible to go the other way if you take a VERY light cut--this is sometimes called a "climbing" cut--and sometimes you need to do this to avoid tearout when going against the grain, but most of your routing will not require this. Nick

2. 
   fredsmart48 | Feb 10, 2003 11:19pm | #2

   IT IS IMPORTANT TO ALWAYS MOVE THE ROUTER OR THE STOCK SO THAT YOU ARE WORKING INTO THE CUT. RATHER THAN WITH IT.

   ( UNPLUG THE ROUTER )

   The easiest way to make sure you are doing things right , especially if the router is mounted in the table is to get your eye at table level and look at the bit. You will want to push the stock into that bit so that the carbide cutting edge hits the material first. When you are looking at the bit at table notice where the carbide edge is and make sure you push the stock toward that edge, and NOT toward the back of the bit.

   May not have finish describing this above.

   when cutting the relief cuts on the back end you only cut a about 1/4 inch at the very end of the board while pushing the board into the cutter you also move the board from right to left, (you do not make a clime cut). then you go to the start of the board and make the regular cut from Right to Left. 

   To me it sound more like your piece of wood you had the grain went toward the out side of the cut. I have found in that kind of case you need to move the board to end of the cut and take the board just push the board into the cutter to make a relief cut once or twice so as you finish the cut you have nothing to tear out. Make shallow cuts it will also help.  

   
   

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   Edited 2/10/2003 5:56:48 PM ET by fredsmart

1. 
   Elcoholic | Feb 11, 2003 12:21am | #3

   Normally feed into the cut.  If you're climb cutting the cutter may try to overfeed and tear the piece right out of your hands pulling them in to the cutter in the process.  Birdseye is a bitch to machine.  Take light cuts.  If that doesn't work try cutting the rabbets on your table saw if you can.  Sometimes I do find it necessary to climb cut.  If I have to, I will, but I'll make a jig to hold the part so as to keep my hands well away form the action and use oversized bearings or a fence setting to limit the bite to very light cuts.John O'Connell - JKO Handcrafted Woodworking

   Life is tough.  It's tougher if you're stupid - John Wayne

1. 
   GrouchieGrum | Feb 11, 2003 01:05am | #4

   lets see if I can draw this....

   =================================

                                                                         /O 

   w/board going <--------------------

   vs

                                                                            /O

   ===================================

   w/board going  <----------------------------------

   in both cases the "bit = /O"  was moving in a counter clockwise direction..

   I was doing the top diagram...... as I think about it.. the top diagram would seem to want to chunk more wood out to the left of the bit(e.g.-what I am routing)  like someone sticking a wedge into wood and prying up the wood...

   whereas with the lower diagram you are nibling into the wood piece as you move... the wood can not splinter out cause it is pushing into itself......

   totally confused in Indianapolis, 

1. 
   SVSander | Feb 11, 2003 01:48am | #5

   Grouchie,

   There were several things working against you in your attempt with the birdseye maple.

   1. That particular material can be very difficult to begin with.

   2. It sounds like the grain direction was such that it "encouraged" the fracturing that you saw.

   3. The feed direction was opposite of what is "normal."

   For most purposes you want to feed *into* the cutting bit edge rather than in the same direction as the bit edge rotation. Your diagram number 1 shows that the stock feed and the bit rotation were in the same direction. As others have said this is called a climbing cut and can be dangerous -- the bit can catch the material and attempt to "pull it in" and it sometimes brings your hands along with it. It is safer to feed in a direction like that shown in your diagram number 2. Make sure you use push blocks or whatever is necessary to keep your hands/fingers protected even when working in the "normal" direction.

   With problem materials (either because of the species of wood or the grain direction) it is often necessary to install or adjust the fence so that it limits the amount of wood that the bit can take on each pass. I was working with some troublesome cherry at one time that I ended up taking between 1/32 and 1/16 on each pass. Took several passes to make a rabbet that was 3/8 by 3/8. When I tried to take deeper cuts it fractured in a manner very similar to what you described.

   As mentioned before, there are times when a climbing cut (feeding with the bit cutting direction) can be prefereable. In fact, if properly used, it should *reduce* the fracturing or tearout that you described. However, for safety reasons, you must limit the bit to very light cuts and make a fixture to hold the stock. Be sure that you control the feed rate and don't let the bit take charge.

   By the way, I have limited experience with mahogony (only worked with it once) but I believe it is one of the easier materials to machine. Although you must always be aware of grain direction, especially if it changes from one portion of the material to another.

   Good luck,

   Dick Baker

   Sunnyvale, CA

2. 
   JHarveyB | Feb 11, 2003 08:41am | #7

   Hey, Grouchie!

   There is some confusion in the answers to your questions.

   1) Agreed that curly maple is hard to machine in general.

   2) However, the problem you describe is common when working any wood with a router bit (or even a shaper.) As you surmised, the cutting edge of the bit acts as a wedge between the fibers of the wood and splits pieces of wood off ahead of the bit's arc of cut. When one is lucky, the grain of the wood is sloping from the cut toward the edge of the wood, so the splits head for the edge, and the splitting is all cut away as the bit moves past. (This also makes the cutting easier, as part of the wood to be cut has already flown off in a chunk.) When we are unlucky, the grain of the wood slopes away from the edge, and the splitting moves deeper into the wood than the bit is going to cut, leaving a rough, chunked out edge like you got.

   3) You certainly moved the board past the router bit in the proper direction. Any attempt to rout in the wrong direction (a "climb cut") with a normal sized cut would have sent the board out of your hands and across the room. The proper direction is so that the cutter is trying to push the board back toward your hands. Climb cuts are extremely dangerous except when taking the most minute cuts (eg, the purfling cut on a guitar body.) It would be like feeding a board thru your tablesaw from the back, watching it shoot across the room.

   4) What can be done to minimize the problem? Light cuts help a bunch. Gives a smaller amount of wood (that will cut or bend instead of tearing out a chunk.) Using a larger diameter bit helps a bunch, because it is tending to push the wood into itself instead of ripping it out of the edge at a sharp angle. Slower feed rates help a bunch as well, tho it sometimes means you get burn marks from the wood overheating instead. Another replyer suggested a 1/2" bit; I'd use a 3/4 or 1" bit if I had it. Or if I wanted a really clean cut, I'd cut that edge with a tablesaw first, or the whole rebate.

   Routers are the most versatile power tools in the shop. Enjoy yours!

   Harvey

3. 
   fredsmart48 | Feb 11, 2003 02:10am | #6

   Another tip for making a 1/4 rabbet cut you use a 1/2 router bit so you only need to use half diameter of the bit.

   set your fence so the bit so you get a 1/4 width and it just clears the side of bit. If you get the infeed fence so it just clears the bit you get the fence to act like a chip breaker.

   ps.  you cut the end grain first then the long grain.  so if the end grain splinters out the next cut removes the damage. 

   
   

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   Edited 2/10/2003 6:14:42 PM ET by fredsmart

4. 
   noone51 | Feb 11, 2003 08:32pm | #8

   Having worked a lot with birdseye lately I can relate to your problem. All of the prior advice is excellent and I would like to further suggest the use of a 1/2" (1/2" diameter and 1/2" shaft) spiral upcut bit. I use a Whiteside that is razor sharp and it produces excellent results where other bits fail. It solved my problem maybe it will work for you too.

   Best of luck