New Oakie, Burned Round Over Detail

[John McKissick]

New to working with oak, red oak in this case, and I used a 3/8 round over bit with bearing and the surface was burned. Not 100% but something like 10-20% of it. Sanded most of it out but that was not fun...

The tool, although a box store special set with 3 sizes, feels sharp to my finger with no visible damage. Does well with pine/spruce (softwoods). I had the router (a big Bosch) pretty high speed but feed very slowly with one pass.

I know I did something wrong but which is most likely causing my burning? Slow the router, crappy bits or should I have taken multiple passes?
I don't have much stock for testing. Pretty much used up what I had on hand or more precisely what my son left when he moved out...

[Mike Kees]

I think you went to slow. Try feeding faster.

[John McKissick]

I think you went to slow. Try feeding faster.

Hmmm, last answer I expected but with limited remaing scrap wood I'll give it a try

[Richard Coers]

3 options; slow the rpm of the router if it's variable speed, feed faster, raise the bit for the first pass, then drop it to the right height for a second pass. But I've never had to do a two pass with a 3/8" round over. You got what you paid for with the cheap bits. Red oak is a very easy wood to work with.

[Zachary Hoyt]

Yes, I have had this problem with hardwoods, feed too slow and it will burn. As was said above, if you have a variable speed router turn it down, or move the router faster. I have to routinely rout an S curve freehand to a line with a tray bit, and I turn the speed way down so I can move the router slowly as I get close to the line. This is routing jatoba, ebony, rosewood and the like, so they're very hard woods.

[John McKissick]

Thanks Mike, Richard and Zach for your help

Tough project for me trying to make furniture grade peice with limited stock, skill and experience. Coming out pretty okay so far but taking a long time. Good thing my customer (free for my daughter) is an easy client and not in a hurry. She is having a friend heat carve a design in the side panels.
I'll try to remember to post a pic when done but here is the top so far. A shoe bench with shoe starage underneath

Can see the faint remnants of the burning mostly sanded out

430239

[Lee Schierer]

Three things are important with router bits.

1. You get what you pay for in terms of cut quality in router bits. Cheaper bits tend to burn more. Carbide bits last longer than High speed steel. Multiple light passes will reduce burning to some extent.
2. Too much speed of feed or rpms leads to tear out and scalloped cuts.
3. Too little speed or stopping causes burn marks.

When working with plain sawed red oak watch the grain carefully. Deep cuts in grain ends can cause lifting of the grain and splintering.

[glenn bradley]

The rule of thumb I have read for the amount of material to "eat" in a pass is 3/8" x 3/8". I'm more conservative and go for about a square 1/4" of material in a pass. Even so, materials vary; red oak, cherry and hard maple can be burn prone. Adjusting speed of bit, speed of feed or taking multiple passes can solve this. A great trick for edge profiles on burn prone woods with bearing guided bits is as follows:
- Run a strip of blue painter's tape along the edge that the bearing will ride against.
- Make your pass(es) as usual.
- Remove the tape and make your last pass.

[Mel Fulks]

I climb cut pretty fast without letting the bearing contact the work. Then finish the cut moving router in standard direction
making sure the router is being moved along fast enough to obviate any burning.

[John McKissick]

The rule of thumb I have read for the amount of material to "eat" in a pass is 3/8" x 3/8". I'm more conservative and go for about a square 1/4" of material in a pass. Even so, materials vary; red oak, cherry and hard maple can be burn prone. Adjusting speed of bit, speed of feed or taking multiple passes can solve this. A great trick for edge profiles on burn prone woods with bearing guided bits is as follows:
- Run a strip of blue painter's tape along the edge that the bearing will ride against.
- Make your pass(es) as usual.
- Remove the tape and make your last pass.

Interesting idea. Get most of the material and then a final light clean up pass. I have an adjustable rabbet bit I might be able to borrow a larger OD bearing. Have you tried that?

[Jim Becker]

Unless you have optimal RPM combined with optimal speed of cut, burning can result because not enough chips are being formed to take away the heat. This is something that those of us with CNC machines have to live by. But the same principle applies to hand-held or router table use. One of the best ways to avoid it is to not take the full cut on the first passes. Take it almost there ... you may get a little burning ... and then do a final pass that is super light to get you to the final place. And yea...sharp is important, too. Make sure you have a diamond hone that you can touch up the flat side of the cutters with.

[Mark Daily]

Unless you have optimal RPM combined with optimal speed of cut, burning can result because not enough chips are being formed to take away the heat. This is something that those of us with CNC machines have to live by. But the same principle applies to hand-held or router table use. One of the best ways to avoid it is to not take the full cut on the first passes. Take it almost there ... you may get a little burning ... and then do a final pass that is super light to get you to the final place. And yea...sharp is important, too. Make sure you have a diamond hone that you can touch up the flat side of the cutters with.

+1 on the super light final pass- that always works for me.

[Warren Lake]

Mel answered how I do it.

Jims way is close but slower to readjust. Since he is going forward still chance blowout and if its enough it could be below the final pass. Then is the stop going to be exactly the same every time? Its no precision system how a router goes up and down on the posts.

Mels way you need a feel for what you are doing but its the best way. Fastest and cleanest.

Coming to mind is you talk about the bit going dull, you are not sanding first are you before you router? that will dull your tooling faster if so.

Not so sure about touching up router bits, times I did with a diamond file access was crappy and there was little change.

[Jim Dwight]

I will agree with the other recommendations but also add that I like MLCS Woodworking for router bits. They may be cheaper than the big box stores and are not high end but they've worked well for me. The prices are good and include shipping which has always been quick.

I use my router table when possible partially because it has pretty decent dust collection but also because it is easy to set it to make multiple passes. I find oak more prone to splintering than burning. I get more burning with cherry and especially maple. It helps to know what to expect so you can adjust.