How to Prevent Router Burning - Woodworking Talk - Woodworkers Forum

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post #1 of 22 Old 07-18-2011, 07:51 PM Thread Starter
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How to Prevent Router Burning

Hello all. I got a new Hitachi KM12VC router last week and this is my first run with it. Actually, this is my first run with a router ever! I am using a flush trim router bit (from MLCS) to try and repair some mistakes I made in building a desk. First I need to smooth out the edging pieces. They were previously glued on - I sawed them off to start over and they are a little uneven due to that. I need them to be flush to re-attach to the tabletop.

Since I'm new to routers, I'm not sure what's causing 2 things: burning and grooves. The burning I think is caused by the shaft below the cutter. I had to extend the bit pretty low to place the bearing on the surface I wanted, and I think the shaft below the cutter was causing the burning. The grooves I'm not so sure about. I'm not sure if that's the right term. My routing seemed to go in waves, there are crests and troughs instead of a flat surface. Here are some pictures below to show what I'm talking about.

[IMG][/IMG]

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post #2 of 22 Old 07-18-2011, 08:56 PM
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I don't see any pictures... I'm sure I can help ya with a few decent pics...

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...
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post #3 of 22 Old 07-18-2011, 08:59 PM
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Looks like the shank of the bit was rubbing the wood. I can see some build up un the shank.
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post #4 of 22 Old 07-18-2011, 09:13 PM
where's my table saw?
 
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Yup !
You are using that combination in a manner in which it was not intended. The bearing is meant to ride on a templet or a finished surface to flush trim a thickness that fits within the cutter to the same profile or dimension.
bill

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo

Last edited by woodnthings; 07-18-2011 at 09:22 PM.
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post #5 of 22 Old 07-18-2011, 09:20 PM
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When did we get pictures??? I don't see em!...

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...
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post #6 of 22 Old 07-18-2011, 09:21 PM
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The bit in the picture doesn't have a long enough flute length for the size stock shown. To flush trim with a bit with a bearing, there has to be a smooth guide for the bearing to ride on. The flutes should be longer than the stock to be trimmed.








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post #7 of 22 Old 07-18-2011, 09:22 PM
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Magic sensory vision, lol

Go in with your browser, it'll be there.
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post #8 of 22 Old 07-18-2011, 09:29 PM
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Quote:
Originally Posted by Brink
Magic sensory vision, lol

Go in with your browser, it'll be there.
Nahhh... Too much work, I'm busy relaxing... I'm sure y'all got it handled...

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...
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post #9 of 22 Old 07-18-2011, 09:38 PM
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There you go Tom
Attached Images
  
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post #10 of 22 Old 07-18-2011, 09:47 PM Thread Starter
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Ok, that was what I figured. Any idea how to fix the "grooves" as I roll the router along? The router has a dial setting to adjust the RPMs but I'm just leaving that as is for the moment since I'm clueless.
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post #11 of 22 Old 07-18-2011, 09:51 PM
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Quote:
Originally Posted by Brink
There you go Tom
Your not a meanie after all, Brink! haha

Bar sounds and looks like your attempting to use your router as an edge jointer.

Do you have a router table? What you are trying to do would be better accomplished with a 1/2" flush trim bit with a cutting flute longer than your stock is thick. Clamp a straight edge (known flat and straight piece of wood) to the piece and adjust your router bit where the guide bearing rides along the straight edge.

Do not attempt to hog off more material thickness that 1/3 the router bits cutting diameter, it's not designed for plunging.

Use medium speed with these bits despite their small diameter to reduce chatter and burning...

There is a better way if you have a router table though...

~tom ...it's better to remain silent and be thought a fool than to open one's mouth and remove all doubt...
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post #12 of 22 Old 07-18-2011, 09:56 PM Thread Starter
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No router table as of yet but I was considering building one as seen in a youtube video:





Can you give me a hint how to do it better with a table?
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post #13 of 22 Old 07-18-2011, 09:57 PM
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The neat thing with a flush trim bit, any undulation that the bearing rides over, will be transferred to the cutter.

If the goal is to smooth the side of a board, two things to try.

1) use a plane to smooth it, or,

2) remove the bearing, then set up a guide for the router to ride against while taking a shallow cut.

Like c-man said, your cutter isn't as wide as your work piece, and that makes it a little more difficult. And, unless your comfortable with a router, and setting up guides and such, you might not want to experiment on an important piece.
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post #14 of 22 Old 07-18-2011, 09:58 PM
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It's the wrong set up

The bearing wants to ride on a smooth surface. The wood is too thick for the cutter. The grooves are cause by the router bearing "bumping" along on the wood below. It's not meant to be used this way. It's meant to trim a thinner piece than you are using with a finished piece/template used below. If you want to practice use a round over bit with a bearing below. Make certain the surface below on which the bearing rises is smooth, since it will pick up any dents or lumps and make your cut the same ...lumpy and bumpy. bill
BTW you can get router bit with a bearing either above or below the cutter.

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo

Last edited by woodnthings; 07-18-2011 at 10:02 PM.
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post #15 of 22 Old 07-18-2011, 10:13 PM Thread Starter
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Well, shoot. Thought I had come up with a creative fix.
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post #16 of 22 Old 07-18-2011, 10:38 PM
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Quote:
Originally Posted by BarclayWood
Well, shoot. Thought I had come up with a creative fix.
This is the best way to learn what works, and what doesn't.
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post #17 of 22 Old 07-18-2011, 10:55 PM
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Hi Barclay - Get a pattern flush trim bit like this one
http://www.rockler.com/product.cfm?page=11083&rrt=1

Tack a smooth strip of MDF along the top edge of your workpiece and let the bearing ride on that. The bit will trim the stock even with the MDF guide strip. If the cutting length isn't enough, just lower the bit for a second pass with the bearing riding the surface that has just been cut.
How stable was the router? Pics look like you may have wobbled a llittle. Most of the wavyness is from the bearing following the saw marks though.

John

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Last edited by jschaben; 07-18-2011 at 10:59 PM.
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post #18 of 22 Old 07-19-2011, 01:28 PM Thread Starter
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Well, here's an update. I accomplished what I wanted to do by switching out the flush trim bit for the 3/16" straight bit! It ain't pretty, but I have a pretty steady hand and shaved the edging down to where I wanted it. Hope I didn't offend the woodworking gods in the process.
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post #19 of 22 Old 07-19-2011, 03:54 PM
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Thumbs up There's 4 ways...

Freehand like you did. (not accurate)
From the top with the router base against a straight edge or guide.
With a guide bushing riding on a smooth surface or between the edges of a guide.
With a bearing bit riiding on a template above the work or below the work. (requires a template)
The last way, no. 5 , requires a router table and fence. bill

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo
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post #20 of 22 Old 07-19-2011, 05:46 PM
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A Simple Method

There's an easy way to straighten out (joint) the edge of wood or laminate. Very similar to this method, You need no trim bit with a bearing. You need no template as a straight edge guide. This is a simple table/fence set up for a router.

Pretty much as the link shows, but more simply, any substrate...plywood, MDF, particle board, or melamine (which is very smooth and works well), is used as a table top. It can be 12" wide and 3' long.

Take any 3/4" substrate, 2"-3" wide, and maybe 3' long, and laminate the 3/4" straight edge with HPL (like Formica). At the middle of the 3" piece, laminate on top of the laminate another strip with 1/32" Formica. This will be the take up for what gets milled off (kinda like the outfeed table on a jointer). Trim off the mica on top and bottom.

Lay the 3" strip on the table so the back edges line up. Make a mark in the center, right where the add on 2nd piece starts. Drill a hole in the table for the router bit you will use...1/4" straight faced carbide tipped bit will do fine. Or, you could use any size bit that's straight faced, like 1/2" will work too. For that bit, drill a 1/2" hole.

Mount the router from underneath, so the bit sticks through. Turn on the router, and feed the face (with the laminate on it) slowly into the bit straight so it makes a slot further into the 3" piece than the thickness of the bit, right where the add on piece of mica is glued. Looking right at it, have the add on piece to the left of the bit.

When positioning the 3" piece, have the cutting edge of the bit line up with the right side face, and fasten the fence down. So, what you have is a nifty jointer set-up that takes 1/32" off on each pass. With the router off, and the bit retracted, take a file and put a small bevel on the add on mica, as a feed in bevel. It won't need much, just take it down to knock off the square edge.

Now, when making a pass, The stock will slide real nice, and only 1/32" will come off. You can make as many passes as necessary to get a straight smooth edge. Looking at it the feed direction would be from right to left. The bit should be turning into the wood as you push the wood.








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