Large miters

[Coop]

2 hours ago, drzaius said:

Glad it's working out, but rough cutting with a circ saw & then cleaning it up with a straight edge & router is much easier, faster, and you're guaranteed a perfectly jointed edge.

Maybe in Alberta but not in Houston 

[drzaius]

I think the key to success is to only take a very small amount on the final pass. Maybe 1/32".

[Ron Swanson Jr.]

2 minutes ago, drzaius said:

I think the key to success is to only take a very small amount on the final pass. Maybe 1/32".

I had trouble with the setup. Straight edge would move a hair. Correct that. Clamps in the way. Correct that, something else. Correct that, well, you get the picture. But like I said, that's not where I spend a lot of my time, so for some maybe it's really easy. I was stupidly trying to use a pattern bit. Should just used a straight bit with no bearing. Oh well.

[drzaius]

Just now, applejackson said:

I had trouble with the setup. Straight edge would move a hair. Correct that. Clamps in the way. Correct that, something else. Correct that, well, you get the picture. But like I said, that's not where I spend a lot of my time, so for some maybe it's really easy. I was stupidly trying to use a pattern bit. Should just used a straight bit with no bearing. Oh well.

A pattern bit works fine, better than running the base against a straight edge. With the pattern bit, the straight edge goes exactly where you want the cut to be, eliminating that possible source for error. And the base may not be perfectly concentric to the bit, so if the base isn't contacting the straight edge in exactly the same spot for the entire cut, then the cut won't be perfect.

[Ron Swanson Jr.]

Yep I know how a pattern bit works. It didn't work for me in this setup. Probably user error. Take care.

[Coop]

While on the subject, what is the difference between a pattern bit and a flush trim bit, the bearing location? One used in a hand held and the other on a table? 

[Ron Swanson Jr.]

Just now, K Cooper said:

While on the subject, what is the difference between a pattern bit and a flush trim bit, the bearing location? One used in a hand held and the other on a table? 

No difference. They're the same thing. You can get the bearing on top or bottom but as far as I know that's the same thing.

[Chestnut]

I've never gotten the pattern bit and strait edge to work either. Something ALWAYS seems to move and then your worse off then you were before. Glad you got it figured out.

[drzaius]

Okay guys, I'm not being critical here, but just what isn't working for you with the pattern bit & straight edge. My experience is that at first I was trying to take too big a cut, which made the router harder to control & bad things just seemed to happen. I found that if I took cuts of 1/16th or less to get close & then just a very small cut to bring it to the line, that seemed to work great. Of course, the straight edge needs to be very securely clamped. Spring clamps just wont suffice.

By taking small cuts it allows the router to move at a good even pace and avoid tear out & burning. Oh, and be sure to keep lots of down force on the side of the base away from the work edge. Wax on the base & straight edge help tremendously.

[Ron Swanson Jr.]

@drzaius howdy. 

So here's where the challenge lies when I tried it on my shelves. 

I really struggled to get my 24" straight edge clamped effectively. If the bearing is going to ride on the side grain of the straight edge, then the top has to be completely free of clamps or the router will hit them.

Then, there is so little margin for error on miters. If it slips a half a degree, your joint will not be tight. 

I spent several hours on trying this and did not end up with a good joint.

Like I said before, maybe guys who do this all the time are better or have different to technique. Also, the fact your clamping that straight edge at a 45° angle limits your clamping options. And of course the work piece had to be elevated. These were nearly 6 feet long.

In principle this sounds straight forward and easy but it's not. Or, it wasn't for me anyhow. 

I do appreciate you and your suggestions and your willingness to assist so please don't take any of this as defensiveness. Your probably 20 times more skilled than I am and maybe for you this is child's play. My experience was different.

Once I ripped them into 2 I was able to cut the joint on the table saw with great results.

Take care

[Chestnut]

I know i was using the wrong strait edge but it was the best i had at the time. Mine was more the vibrations from the router were shaking everything loose. It'd go great for 20" then something would loosen and it'd slip. I was taking a small shaving like you said. It seemed that the piece was large and i didn't have a good place to clamp it down to mitigate the vibration.

I think i'd have better luck if i had a strait edge i could put some adhesive sand paper on and clamp down. but now i have a track saw and well that has basically solved all the problems i once had.

[drzaius]

Now I understand the frustration. When I said straight edge, I should have said a thin board about a foot wide with one edge straight. That leaves room for clamping that won't interfere with the router. Having sandpaper glued to it would sure help it stay put, but I find that using a couple of C clamps well tightened will hold it fine. Having it tight is crucial because vibration from the router will move it otherwise. 

And to emphasize what I posted above, be sure to hold that base down tight to the board so the bit doesn't tip into the cut.

When doing a 45* cut it really helps to do a climb cut when you're doing the edge that is cutting at an acute angle to the grain. For those who don't like to do climb cuts, try it both ways & tell me which is safer (in this case).

[curlyoak]

When I clean up a long cut for a glue joint, I cut using a circular saw close to the line and clean it up with the router. Take a beater board. clamp a straight edge moving the router along the edge for an inch. Now you know the exact distance needed to set up the edge. I rip a piece of scrap to use to add speed to set up the straight edge. The direction is always to pull the router to the straight edge. I use a straight flute no bearing. I like to start with a freshly sharpened bit. And small cuts are easier... A large project might require 2 bits...

[Ron Swanson Jr.]

Closing the loop on this thread. Installed today, happy customer. I had the large miter air tight in my shop but as the desk that it's fastened to wasn't a perfect 90, it opened a little bit on one end. 

Shelves were an extension of the desktop, plus the upper shelves and a little space filling triangle. 

Nothing to write home about.