# Tongue and groove tapering



## gcordoba (Nov 5, 2012)

hi, I am new to the forum, i have been doing some projects as a hobby but i have some issues i need help on. one is while doing tongue and groove joints.

I made my router table and i am using it to do the joints. The problem I am having is that the groove seems to taper off, as if the board is "droping" and the groove is not parallel to the board. I have tried doing the groove with and without feather boards, also work very much on insuring my router insert is alligned. still can't make it right.

In the end my issue is that when I put the boards togheter on one end the joint is flush but in the other end the board is 1 mm off. don't understand why this happen and I don't what to sand this off.

all the components of my router table i build myself, could this be the problem?

any comments?

regards

gabriel


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## Steve Neul (Sep 2, 2011)

Try checking to see if the router bit is bent. It could cause the bit to run out of round and pull the board up off the table a little. Another thing you might check and see if the bit is staying in the same position. I've had bits that were out of balance and they would move outward in the collet. Something is wrong. You should be able to run the board free hand and the bit stay in the router and the board stay flat on the table. If the board is just rising off the table you might make a feather board that has short fingers so it doesn't give so much.


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## jschaben (Apr 1, 2010)

gcordoba said:


> hi, I am new to the forum, i have been doing some projects as a hobby but i have some issues i need help on. one is while doing tongue and groove joints.
> 
> I made my router table and i am using it to do the joints. The problem I am having is that the groove seems to taper off, as if the board is "droping" and the groove is not parallel to the board. I have tried doing the groove with and without feather boards, also work very much on insuring my router insert is alligned. still can't make it right.
> 
> ...


Hi gabriel - sounds like the board is either raising or lowering (which edge is the groove getting closer to?) as, or after it passes the bit. Is your table flat all the way across? Does the stock have sufficient support for the full length of the cut?:huh:


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## woodnthings (Jan 24, 2009)

*Test*

Rout a groove in a 3 ft long board holding firmly down on the table either by hand or with a feather board.

Check the height of the initial groove with the trailing end of the groove by placing it under the cutter. It should fit at the start as well as at the end. It should be the same ... unless the bit is changing it's height in the collect OR the router is changing it's height in the base, OR the router is not securely mounted to the table.

If you use a router lift make sure it's not changing height as you go. Older ones did not have a lock for the height. Newer ones do. Jess Em Mast R Lift II has the lock and is a big improvement over the old style which used to vibrate out of adjustment.


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## gcordoba (Nov 5, 2012)

Steve Neul said:


> Try checking to see if the router bit is bent. It could cause the bit to run out of round and pull the board up off the table a little. Another thing you might check and see if the bit is staying in the same position. I've had bits that were out of balance and they would move outward in the collet. Something is wrong. You should be able to run the board free hand and the bit stay in the router and the board stay flat on the table. If the board is just rising off the table you might make a feather board that has short fingers so it doesn't give so much.


I check the bit and it look like the bearing on the bit is not rotating as freely as it should. do you think this could the factor that is causing the board to up? Still, i did several pieces of wood and all have the same error, so it seems to be something else. can my aluminum insert be warping?


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## Steve Neul (Sep 2, 2011)

gcordoba said:


> I check the bit and it look like the bearing on the bit is not rotating as freely as it should. do you think this could the factor that is causing the board to up? Still, i did several pieces of wood and all have the same error, so it seems to be something else. can my aluminum insert be warping?


No don't pay any attention to the bearing for the problem you have. If the bearing was completely locked up it would at most make a burn mark on the wood. Many of the old fashion bits didn't have a bearing on them at all and you had to control the amount of pressure on the bit to keep from leaving a burn on the wood. Without being there it's hard to say what the problem is but I would keep looking at the bit as the problem. You might set something solid and stationary to where the edge of the bit barely touches it. Then by hand rotate the bit around and see how close the opposing bit comes. Occasionally I will buy a new bit that one cutting surface is completely different than the other side. Each side of the router bit should be the same length. Otherwise it would be like driving a car with one side of the tire being heaver than the other. Also you might measure the distance between the table and the bit on each side and see if it is the same. If one side was higher than the other, that alone would be enough to raise the board up when it's running. This is why I was guessing the bit may be bent. At one time I worked for a cabinet mfg that used a spine cutting router bit to mortise cabinet faceplates. Occasionally someone would bend the bit and it would throw the bit so far out of balance you couldn't attempt to run it. It doesn’t take very much to screw everything up. If the router bit is in balance you should be able to run the groove bit with or without the featherboard without it raising off the table. The featherboard just adds a safety element and also helps mash a board down that might be a little warped.


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## woodnthings (Jan 24, 2009)

*I'd be surprized if it's the bit*

Any deviation in the width or height of the cutters will end up a wash. When the cutter rotates it takes care of any deviation. 

Either the work is shifting, the table is sagging with pressure, or the mounting plate is sagging/shifting. 

If the bit were changing it's elevation, then beginning of the next cut would be "off" the amount the previous cut on the end was off. 

It's still a bit of a mystery....... 

Be certain the work is perfectly flat and square before any table routing operation.


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## Steve Neul (Sep 2, 2011)

OK another thing you might try is take the router off the router table and try running the groove freehand on a board clamped to a bench. If there is nothing wrong with the router or bit then you shouldn't experience any undo vibration running it. Since it's a large bit be sure to hold on to the router with both hands. At least you may be able to narrow down where the problem is.


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## Hammer1 (Aug 1, 2010)

It might help if you were more specific about what type of bit you are using and how, work flat, up on edge, a slotting cutter or something else, loose wing cutter, washers and a securing nut, 1/4" or 1/2" shank, dust collection, depth of cut, type of wood, how much variation, using a fence or just the bearing. A failing bearing could be a sign of heat build up. That may be evidence of over loading. A picture might show the issue.


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## jschaben (Apr 1, 2010)

gcordoba said:


> In the end my issue is that when I put the boards togheter on one end the joint is flush but in the other end the board is 1 mm off. don't understand why this happen and I don't what to sand this off.
> 
> gabriel


 
This says to me, that the board is changing plane with the cutter. Were the cutter angled, bent or otherwise, I would think the groove would be wider and the tongue narrower. Which way the board is traveling would be shown by which way the groove was moving, either toward the top or toward the bottom of the board. :smile:


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## rrbell (Oct 22, 2012)

Are you using feather boards?


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## rrbell (Oct 22, 2012)

rrbell said:


> Are you using feather boards?


Sorry, posted before I read everything! The only thing that I can think of that might do this is if your material is somehow lifting away from your work surface but if you've tried several pieces the problem would not be in the material. Is your table surface one single piece? Lay a straightedge across your table and look for any signs of it being warped or bent..


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## GeorgeC (Jul 30, 2008)

When you start a new cut on a new board has the location of the cut returned to the original location? Or does this new cut start off by the amount that it ended up on the first board?

George


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## gcordoba (Nov 5, 2012)

Steve Neul said:


> OK another thing you might try is take the router off the router table and try running the groove freehand on a board clamped to a bench. If there is nothing wrong with the router or bit then you shouldn't experience any undo vibration running it. Since it's a large bit be sure to hold on to the router with both hands. At least you may be able to narrow down where the problem is.



I am going to try this, sound like a good way to start eliminating variables. 

thanks


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## gcordoba (Nov 5, 2012)

GeorgeC said:


> When you start a new cut on a new board has the location of the cut returned to the original location? Or does this new cut start off by the amount that it ended up on the first board?
> 
> George



No all cuts start and end at the same point, the odd thing is that i did first the tongue portion and all seem straight, then I cut all the grooves and all are "tapering", so the bit wasn't moving. I the end I have fliped the boards and cut from the other end, this gave me a wider groove that is allowing some movement to adjust for flushness, but I am getting consistent variation. One thing I notice is that when I do the groove the strain on the router is bigger (removing more material) this seems to be causing some defletion/movement when i cut. don't know were???


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## woodnthings (Jan 24, 2009)

*how are you making both?*



gcordoba said:


> hi, I am new to the forum, i have been doing some projects as a hobby but i have some issues i need help on. one is while doing tongue and groove joints.
> 
> I made my router table and i am using it to do the joints. The problem I am having is that the groove seems to taper off, as if the board is "droping" and the groove is not parallel to the board. I have tried doing the groove with and without feather boards, also work very much on insuring my router insert is alligned. still can't make it right.
> 
> ...


R U using a slot cutter? OR are you using tongue and groove cutters?

Using a slot cutter to form the two sides of the tongue requires a pass and then a flip. The groove could be done the same way with a cutter that is slightly less wide than the desired groove. By flipping it the groove will be centered.

If using dedicated cutters, the parts "should fit like a glove."
If so what brand of cutters are you using? This is a far less time consuming way to make the pieces than by "pass and flip" so it would be the best solution if you can afford the cutters.... :blink:

http://www.rockler.com/product.cfm?page=2134&site=ROCKLER


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