Trapped Router Cut

[rrich]

Nobody KNOWINGLY makes a trapped cut on a router table. But how often does it happen without us realizing it until we're fighting the cut?

How does it happen? Well, I need to make a dado the bottom of a drawer. So I zing all four sides of the drawer through the router and cut a 1/4" dado about 1/4" from the bottom of the side. So now I cut the bottom from a piece of 1/4" melamine.

Now to the dry fitting and the drawer bottom won't fit into the dado that I just cut. (Oh bat poop!) We all know that plywood is usually skinny while melamine is almost always fat. (Or perhaps you were sold a 6mm bit disguised as a 1/4" bit.)

Well, the solution is simple as the router is still set up. Just make the dado a bit wider. (About 1/64" + or 3/128") I'll just move the fence a bit and re-cut.

Without thinking it is easier to move the fence toward the router bit because I can feel the front of the fence moving against a stationary finger. (Put your finger against the fence and push the fence toward the finger.) The fence is adjusted so now lets cut.

What has happened is that the drawer side is now being cut in a trapped condition. Granted the depth of cut is just 3/128" but it is still trapped. If you are not expecting the trapped condition, the best that will happen is the drawer side is flying across the shop. The worst leaves very little to the imagination and perhaps one less finger.

So where did I go wrong? I moved the fence TOWARD the router bit. The correct procedure is to move fence away or back from the fence.

[Beamer]

GREAT post, Rich!

These are the kinds of things that the words "Pay attention while in the shop..." means ... it's paramount to not get caught up in the passion of building something and forget something like this.

VERY good post!

[cabinetman]

I do drawer rabbets and grooves on the TS. If the bottom is too tight, instead of changing a router set up I would just lightly belt sand the underside edge a bit to get a fit. Even with 1/4" bottoms the edge doesn't make the bottom any less reliable.

If the groove has to be made wider, it may be just a matter of seeing which edge has to be milled. Knowing the direction of the bit, and which way the stock has to be fed, may take a few seconds to figure out. Not taking the time to do that can be hazardous. This is a common mistake when in a rush.

[Leo Voisine]

Real Nice point Rich,

I would add though - the direction that you push the piece through the trapped condition will dictate if you are in "climb cut" or "conventional cut".

A climb cut will grab and pull the piece out of your hand - while the conventional cut will try to push back at you.

Conventional cutting is always best on a router - either hand held or router table.

In a trapped cut position - you will most likely be settting up a climb cut scenerio.

[sawduster]

Actually, it will be a climb cut regardless of the direction of feed. If you are aware of it being a climb cut, then you can take precautions that will make it safe, i.e. feeding in the opposite direction than normal, using feather boards to help you hold the piece and being on guard against the tendency for the work to be yanked out of your hand.

I habitually use a trapped cut for narrowing the width of the tail for sliding dovetails. Using a micro adjustable router fence I can sneak up on the final width two hairs widths at a time, and when it gets really close, I can make a final one hair width cut to only one side of the tail. Feeding left to right on the router table and using a feather board makes these cuts without nervous tension.

As usual, though, if you are not comfortable doing this, then come up with another method which increases your comfort level.

[Ruffnek]

Good tip, Rich. I've experienced that event when "centering" an edge groove using the router table...you know, cut the groove, then reverse the stock and run it through again. One had better have a good grip. That's one reason why, unless it's a stopped groove, I prefer to use the TS for that particular operation.

In addition, unless you are purposely doing a climb cut, move the stock/router as follows;

• Router table - right to left
  
• Free hand router - left to right
  
• Inside circle - clockwise
  
• Outside circle - counter clockwise
  

[imahic]

Never even thought about it until your post, but it makes perfect sense. Thanks for the heads up warning. I knew the right to left, left to right stuff like Cody posted but never stopped to think about the situation you posted happening.

Mike

[rrich]

Jan 1, 2010 10:05:25 GMT -6 imahic said:

... but never stopped to think about the situation you posted happening.

Mike,
That was the intent of the post. It was one of those "Holy Bat Poop" moments!

BTW - The knee switch on the router table paid for itself that day.

[Joe Lyddon]

Rich,

Very good...

It's very surprising to see the board go ZOOoooommm isn't it?

[rrich]

Jan 1, 2010 23:30:49 GMT -6 Joe Lyddon said:

Rich,

Very good...

It's very surprising to see the board go ZOOoooommm isn't it?

Joe,
It was a bit exciting! I always use push pad blocks and as the stock started to want to fly away I stopped and hit the knee switch.

Then I sat down and had one of those "WTF talks with self".

[sawduster]

Rich said,
Joe,
It was a bit exciting! I always use push pad blocks and as the stock started to want to fly away I stopped and hit the knee switch.

Then I changed underwear and sat down and had one of those "WTF talks with self".

There, fixed it for ya.

[rrich]

Jan 2, 2010 15:34:23 GMT -6 sawduster said:

Rich said,
Joe,
It was a bit exciting! I always use push pad blocks and as the stock started to want to fly away I stopped and hit the knee switch.

Then I changed underwear and sat down and had one of those "WTF talks with self".

There, fixed it for ya.

ROTFLMAO ! !

Where is the emoticon when you need it?