Replies

1. 
   cafmotox | Feb 04, 2009 06:38pm | #1

                      good question i never realy thought about that. im no expert and im not sure i have the only answer to your question but i saw your post and thought i would give a reply. so why dont router motors run in the reverse direction to reduce tearout you ask. well the first reason would have to be the bits cutting direction. what do you think would happen if the bit rotated in the oposite dirrection? you would probobly get a whole lot of smoke in the shop and you would have burn marks on the wood, lol. all bits have thier knives or cutting edges facing in one particular direction. the bit is only set to cut in one direction and thats the direction all routers rotate in. its like trying to cut with your tablesaw blade on backwards. we have all done that more than once. that would be the most obviouse reson. unless ofcourse i am mistaken and they make router bits with kives to rotate in two directios. but even then as a router manufacturer you would have to ask your self what liabilties would be at risk if the router could cut in both rotation directions. the operator could accidently feed the work piece through the bit in the wrong direction. i know that that is a force most of us are familiar with as well. the workpiece would fly across the shop like a bullet. and if you had a bit and router that would rotate in the opisite direction then you would only be reverseing the problem to the other end of the workpiece by getting tearout on the opisite end of the board.

                  if reduceing tearout is your primary concern then there are a number of ways to greatly reduce that.

   1.    is to support the corners and edges of the workpiece being routed with a backer board. you can do so by taping gluing or clamping wood to the edges in wich tearout would happen

   2. tearout ocurs more often on end grain so routing the end grain first would help. as the tearout would ocur on the surface that will be eventualy routed over. ask me if that doesnt make any sense to you i could explain it alitle better

   3. use a zero clearance opening on the router table fence. if you make a sacraficial wooden fence.  then clamp one side of the fence to the table.  the carefully pivot the other end of the fence over the back of the bit that you will be using. if you do this correctly you can achieve a fence oppening that is the exact same profile as the bit that you will be using. i use this method for allot of my comon router table bits.

   4. the last method to reducing tearout is a bit more risky but works great if you have a feel for your router and what forces are at work when you use it. at each corner of the workpiece i will run the router in the opisite feed direction verry slowly. going over each corner first in this way before routing the straight edges works great. if you have a router table this method can be quit scary. feed the work in the oposite direction that you would normally feed. take only small cuts with this method. only a 1/8th of an inch to a 1/16th of an inch for each pass. hold on to the workpiece snug but dont put any force on it at all. if the piece decides to fly then let it fly. atleast your hands and fingers will be safe. this method is called back cutting and if done carefully works great to reduce tearout on stringy woods such as mahogany.

   im sorry i went all out with my answer and i am sure you probobly know most of this already i just thought it was a great thing to cover so that other woodworkers could use this info in the archives. as far as router rotation. youl probobly be like "duh" why didnt i think of that but even when i read your question i had to think about it because you even had me thinking.

   
   

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   Edited 2/4/2009 10:50 am ET by cafmotox

1. 
   MikeVan | Feb 04, 2009 07:09pm | #2

   Hello cafmotox, Thank you for your thorough answer! I did assume to have a set of bits with reversed cutting direction, but your thoughts make sense, even though I could think of similar liability issues with other power tools. The router could be constructed so, that when in "reverse mode", there would be no doubt, even for an amateur.

   However, your suggestions to reduce tear-out are good. Thanks.

   I am sure I will never miss the reverse option, when I become more experienced. It was just a thought.

    

   Edited 2/6/2009 6:41 pm ET by MikeVan

2. 
   GLASTARZA | Feb 06, 2009 11:08pm | #3

   M,
   Thank you for your question. I am forwarding it to John White.

   Sincerely,
   Gerald La Starza