Router bit burn

Julio Navarro

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Tampa
I am getting a lot of burn trying to route a panel mould. I am using a CMT panel bit on my router table with a Hitachi variable speed 3hp router mounted on it. I have tried several speeds from slow to the fastest but the burn doesn't seem to go away.

The bit is almost new, I have only used it a few times.

How can I get rid of the burn and how can I avoid it.


Thanks in advance.
 

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Sharp bit, bit speed and feed rate are a lot of it. Just because the bit was used little doesn't mean it didn't get into something a little abrasive (like wenge for instance). Material control can also have a large effect on burn. Do you have feather boards in use? Its interesting that it only appears to be burning at the outer edge where the speed is slightly greater. I usually get burn in the arch. As to getting rid of what you have; I use a scraper as soon as I can after the cut.
 
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I am using two feather boards, top and side and I am doing partial bites at a time. I did run some at high speed and fed the peices as fast as I could so I think your comment of feed speed is the key here.
 
You didn't say what the wood is. Some, like cherry and maple, burn easily.

Try feeding as fast as you can feel safe with, and also sneaking up on the final cut. I usually take at least three passes to rais a panel - one 'hogging' cut to get rid of most of the waste, then just raise the bit maybe a sixteenth for a 'pre-finish' cut, and finally another thirty-secondth or so for the finish cut. That seems to minimize problems for me.

I'm about to make ten doors and three drawer fronts myself. I'm using Hickory this time. Never used it before, so this might turn out to be a learning experience. Wish me luck!
 
Occasionally I will run into a wood, or have to make a cut with a bit that is marginal at best and a way to get through it is to change bearings. Put a bearing on that is a wee bit bigger, hog off the majority of the wood, put the correct bit back on and take a fast pass.

If you are using a router table, just adjust the fence out for the rough, and then set it for the final.

Its a bandaid, but I live where such things as good bits and sharpening are mail order, so I fudge it once in a while.

Just a thought........

Larry2

Oh, guess I should have read the rest of the posts first, but it seems to be a consensious.
 
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I am routing ash and maple, the maple burns much easier than the ash. I am using two passes but I am going to make it three with the last pass just enough to cut out the burn if any.
 
I am routing ash and maple, the maple burns much easier than the ash. I am using two passes but I am going to make it three with the last pass just enough to cut out the burn if any.

Likely you are feeding too slowly, you should go along at a pretty good clip but not enough to cause the material to split out. I will occasionally, when having a little burn trouble, climb cut the material on the first cut then the final pass the right way. Climb cutting is a good technique but you should not attempt it if you do not understand the physics.
 
Likely you are feeding too slowly, you should go along at a pretty good clip but not enough to cause the material to split out. I will occasionally, when having a little burn trouble, climb cut the material on the first cut then the final pass the right way. Climb cutting is a good technique but you should not attempt it if you do not understand the physics.

Or at the lest a stock feeder :eek::eek:
 
I have found that using bits with a slight angle on the cutter seems to cut better then the bits with straight cutters. Maple wll get burn marks if the bits are getting dull or fed to slow.
 
Likely you are feeding too slowly, you should go along at a pretty good clip but not enough to cause the material to split out. I will occasionally, when having a little burn trouble, climb cut the material on the first cut then the final pass the right way. Climb cutting is a good technique but you should not attempt it if you do not understand the physics.

I agree, but that being said I always hesitate to suggest it. I do it without even thinking about it now, but every manual for every tool tells you not to do it so I worry about someone getting hurt and looking me up with their lawyer.
 
Can you show me an example of a bit with an angle on the cutter?

Cynthia

You may already have bits like he is talking about. Most of Freuds new stuff is made this way. If the cutting edge leads forward in the cut at the bottom, in other words the cutting edge does not line up with the shaft, that bit has a shear angle. The advantage is that the cutter is not slapping the piece all along its length at one moment, it is making contact at the bottom and slicing its way through. Much less tearout, and much less shock to the cutter itself. Spiral cutters are the next step with more slice, and they always have a cutter in the wood so create even less vibration.
 
A router bit designer told me that the heat is removed by throwing the chips. I don't have a router table, but have two shapers so I am constrained to slow RPM (say, 10,000). The designer was concerned about overheating since I would be running so slow, and not throwing chips as well as expected in the router bit design. If I focus on getting good chips, I rarely get a burn.
 
I managed to find the right router speed and the right feed rate but still on one board I had to change hands and that small pause caused the only burn.
 

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I managed to find the right router speed and the right feed rate but still on one board I had to change hands and that small pause caused the only burn.

Pausing only slightly will cause burn on some woods like maple, if you can plan your cut so as not to pause it will help a lot. Use push blocks to help you control what operation you are doing. I use a power feeder on all my shaper operations and seldom use a router table. You can get a power feeder that will work on your router table and it would be a good investment depending on how much work like this you are going to do.
 
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