# Speed or Feed Rate = Burnt wood



## Greeneyedeagle (Feb 15, 2009)

This is for all those router experts out there.
If you have a new quality bit.... is it speed of the bit or rate of feed or maybe both that causes surface burns in the wood?
I understand that if I stop my feed... it could cause heat in that area and leave a slight surface burn but what is the most common cause?
And with routers that go from 1 - 6.... what is the general rule of thumb, if there is one, for setting the speed (rpm) of a bit. I'd have to look back at the manual but I'm sure it tells me what the speed is per 1 -6 setting.

Thanks
Palmer


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## Bogydave (Nov 14, 2008)

Palmer
see if this post helps
http://www.routerforums.com/general-routing/10399-router-speeds.html
Wood type, slow feed rate, bit sharpness are also part of it


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## dan_house (Feb 18, 2009)

But both routers are single speed..... a slow and steady feed rate and dont stop?


also does the buildup of crud on cutting contribute to burning? 

Is the an easy way to sand the burn off? Nursing a big bubble on my thumb from sanding out two burns last night....


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## dovetail_65 (Jan 22, 2008)

Oh yes a build up of crud, glue, whatever certainly can contribute or even be the main cause of burning.

In my experience sometimes depending on your bit and the specific wood you are using, burning will happen with a single speed router no matter what you do. 

If you are using a new bit and eliminate the crud and experiment with various speeds at moving the router past the work and it still burns you must go to a variable speed router and then try changing speeds. Once you eliminate the bit and your speed of router movement there is nothing else you can do but change the wood or the rotational speed of the bit.

This is one reason the variable speed router are made in the first place and of course to accommodate different size cutters safely as well.

You may be surprised that sometimes just changing the rotational speed of the bit by 500rpm or even less can make a huge difference in eliminating or contributing to burning.

Nick


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## bobj3 (Jan 17, 2006)

Hi Guys

Just a add a note *** when was the last time you put burn marks on some wood with a hand saw 
Feed rate and the speed of the cutting tool ..

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## dan_house (Feb 18, 2009)

bobj3 said:


> when was the last time you put burn marks on some wood with a hand saw


Point taken


I'll check for crud, as I'm sure thats part of it. I'll have to work on the "me" for a while......


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## curiousgeorge (Nov 6, 2006)

dan_house said:


> But both routers are single speed..... a slow and steady feed rate and dont stop?
> 
> 
> also does the buildup of crud on cutting contribute to burning?
> ...


Dan,
Have you thought about a speed reducer? They work good and aren't expensive...
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060

There is an easier way to sand the burn off... let someone else do it.


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## dan_house (Feb 18, 2009)

Speed reducer?

No, but I'm gonna get one!

Thanx George!

My project.. I'll sand. I'll consider it..._motivation_ to learn better technique.


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## Bogydave (Nov 14, 2008)

I'm not sure why I sometimes get burn marks, but I suspect I feed too slow.
When I slow the router down, I get less burn marks.
Probably most of us hobby users don't get the feel for feed speed for a long time.
"The Feel" is difficult to know. It is how hard & fast your are pushing the wood into the bit & the sound. 
I rarely get it right but am getting better a knowing when I do. It truly is experience learned over time. Keeping a steady feed rate for some cuts is difficult, but i keep trying. I'm getting better. It's like my golf game, I'm getting better but still have look for my ball sometimes.
A trick I've learned is to not make the cut in one pass, leave "just a little" to take off in one final quick pass. The quick last pass, for me, takes the burn marks off when I have them & has less or no splintering.


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## Greeneyedeagle (Feb 15, 2009)

That may be one of my issues also... trying to take too much off in one pass..or better yet..to know how much is too much. It's kind of weird.. 
I wanted to do some serious learning about the bits that I have so I cut some pieces of wood 5" long that were 3/4" by 1.5" wide. I then ran each bit that I had on a seperate piece. I did do the round overs on one side and then replaced the .5" bearing with the .375 one ( now a beading bit) and did it on the other side. Labeled all pieces and then took measurements on beading edges, distance inward that each bit routed..etc. I really learned a lot. but the weird thing... no burn marks at all on any of the cuts that I did. Agreed that all were done with the grain so that may have been the reason.
But now I know with all my measurements that if I want a base to have a 3/8's clearance around the body that is 4" square and my roman ogee routes in from the edge 7/16th's, I can just add those together. 3/8 + 7/16 per side equals 13/16th so I'll need a blank that is 4 + 13/16 + 13/16 = 5 5/8 x 5 5/8. This may be the long way ..... but it has helped me.


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