Trouble routing a blind grove

[Al Bacon]

I have been trying to route this grove for two days and still think I don't have the correct idea. I have tried going to the left and to the right but still have found that at times the router will try to move towards me. The grove is 3/4" wide by 1 1/2" deep. I am only trying to go less that 1/4" deep with each pass but at some point the router will do it's own thing.

So far I have managed to mangle three test pieces and I'm afraid I will have all the wood for the winter if I keep going.

This is the first time I have needed to put a grove this big this deep. I really need to know what I am doing wrong.

320405

[pat warner]

Groves are for trees, grooves we make in lumber from those trees.
Would fabricate a u-shaped templet that will accommodate a templet guide. Take no more than 3/16"/pass with a new cutter. Practice on scrap. The templet will stop the router; no need for an edge guide.

Or maybe a down-grain groove, AKA a mortise, is that what you want?.
If you can get an edge guide on both sides of the work you can control the machine that is trying to control you! Use a new cutter take it easy.

[Al Bacon]

Cool Pat. Maybe that's whats wrong :)

Great idea with the U shaped templet guide. I have a new bit and will set up the guide tonight.

Thanks And I will be making a mortise or for you other guys a down-grain groove. :)

Al

[Peter Quinn]

You can do it with that edge guide you have, you just need some sort of a stop on the other side of the board, so your router is held captive on both sides. Coolest thing I've seen is somebody bought two edge guides and put one on each side of the board, sort of an expensive way to go, probably can achieve the same functionality cheaper. Doesn't matter what direction you go with a groove, one side of the cutter is always a climb cut, and even though you may take light passes any bobbling instantly introduces lots of cutter to the complete thickness of uncut stock..so big climb cut at 1 1/2" depth. You didn't mention how long that groove is? If its just a mortise, or say under 8" length I like the template idea, though the template guides tend to trap the dust in the hole more so than an open router base with some suction on it. You may need to blow or suck it out a few times. If this is a long plow IME templates tend to flex a bit in the center as you push through, it can help to have a few "bridges" that joint the two sides , means you have to move the template. I've found spiral bits tend to get real directional with grooves. particularly down shears which seem to be pushing the router up off the work if given a chance. They work great on the CNC but aren't always ideal free hand such as with a single sided edge guide. Some times a good old two flute plunge bit with a bit of shear is easier to control.

[David Hawxhurst]

i did what peter suggests. didn't use two edge guides but used a piece of maple on the other side of the router to hold the router captive.

[Art Mann]

That Festool router looks clumsy to me for that application. The asymmetrical knobs seem to be in the wrong places. I cut mortises with my Dewalt 618 with just the plunge base and the Dewalt edge guide and I don't normally have any trouble. The direction of travel of the router is also important. Have you tried changing directions?

[Lee Schierer]

It sounds like you are trying to cut a deep groove all in one pass. That router looks pretty top heavy and the grips aren't where you really need them for this type of operation. You need to grip the router right down at the base so you can push the fence against the work piece as you slide it along the length of your cut. Adding a guide behind the router will not do anything to help get a straight cut as the edge guide won't let the router move in that direction. Try taking just 1/8-1/4" of depth at a time.

[Al Bacon]

The mortise needs to be 3/4" wide by 1 1/2" deep by 48" long. What do you all thing about using two edge guides and starting at each end use an up-cut spiral bit to plunge a series of holes about 4" long. Clean out the points between the cuts so there is a place for the chips to go.
Then use a 3/4" straight flute bit and take 1/8" deep passes the full length of the mortise. Using two edge guides gives a way to hold the router down low for more control.
Would this work without putting to much strain on the router?

Al

[glenn bradley]

It sounds like you are trying to cut a deep groove all in one pass.

I also think this is your control issue. 1/4" x 1/4" is my maximum area to remove in a single pass while free hand routing. At 3/4" wide and being a captured cut I would take no more than 1/8" per pass. If the router and the cutting action are pulling the tool from your control, you must come up with a better control idea. At about 5' 11" and 170 pounds I am on the smaller side and cannot control such cuts through brute force.

Are you tying to route this groove along your bench as shown in the pic? If not, knowing the size and shape of the material you are trying to put the groove in will help. If you are cutting the groove in the location shown in the pic and the single edge guide is not sufficient I would use a template. I would mount a 7/8" I.D. by 1" O.D. collar (or whatever works) in your router, build a template similar to the one shown, clamp the template to the work and route in 1/8" steps.

320451

For a 48" run I would be tempted to make a 30" template and shift it to make the desired length as opposed to making a template massive enough to do it in one shot while remaining stable. Route 28" or so to full depth in multiple passes, shift the template and complete the work. You can clamp a long straight edge to the surface to reference the template against for a perfect alignment. I use pocket holes to quickly make such things. They can be disassembled after use and the screws/parts used for other things later.

[Peter Quinn]

I'd just hold the router captive with two edge guides, or an edge guide and a block with bushings/set screws, etc to act as the stop on the other side, and do it all with a sharp 2 flute using 1/8" passes. Best accuracy IME comes from keeping it simple. More steps equals more chances to screw up.

[Al Launier]

Using a template as Glenn suggests should work well, but I would add that in addition to taking shallow depths of cut, I would also consider using smaller diameter router bits, starting at 1/2" and stepping them up according to your comfort level, and leaving ~ 1/32" on each side to finish the width.

[Al Bacon]

Thanks for all the reply's.


Using a template as Glenn suggests should work well, but I would add that in addition to taking shallow depths of cut, I would also consider using smaller diameter router bits, starting at 1/2" and stepping them up according to your comfort level, and leaving ~ 1/32" on each side to finish the width.

In the end I started with a 1/4" up-cut spiral bit down the center making 3 passes for depth. Then switched to a 3/8" up-cut spiral bit down the center. then keeping the 3/8" bit I moved to the sides 1/8" in three passes. I followed that by moving to the sides 1/16". This was done using only one edge guide but the small cuts left very good control.
I was concerned about using a 3/4" bit because as was pointed out one side would always be a climb cut. Not good for router control.

Thanks Al, for the suggestion of using smaller bits. That did the trip nicely. The mortise came out with perfect sides and the dimensions are on the money.

You folks are a great resource, :)

Al