# Burning Bits



## Implementitis (Oct 24, 2009)

This is my first real post on this forum (and for that matter my first real router project). 

I am having trouble with burning on the bit I am using - it is a 1/2" straight and I am using it to cut MDF. I am running the router at about 20,000 RPM and keeping each pass to about 1/8" deep cuts. The router seems to run easy enough and yet every once and awhile, I see burning of the MDF and the blade tips are looking brown. I don't really care about the MDF but I am worried about wrecking the bit. Frankly i don't know if I am feeding too fast or too slow, or running to high or too low an RPM or what. 

Any guidance on selecting the RPM, etc., is greatly appreciated.


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## bobj3 (Jan 17, 2006)

Hi Eric

MDF is very hard on router bits,,are you by change plunging the bit in...you may have cooked the bit right off the bat...most of the work is done right at the tip of the router bit and if you took off the edge it may burn the stock...

It's best to use solid carb.bits on MDF they will stay sharper than the standard router bits..and last longer..

MLCS solid carbide router bits

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Implementitis said:


> This is my first real post on this forum (and for that matter my first real router project).
> 
> I am having trouble with burning on the bit I am using - it is a 1/2" straight and I am using it to cut MDF. I am running the router at about 20,000 RPM and keeping each pass to about 1/8" deep cuts. The router seems to run easy enough and yet every once and awhile, I see burning of the MDF and the blade tips are looking brown. I don't really care about the MDF but I am worried about wrecking the bit. Frankly i don't know if I am feeding too fast or too slow, or running to high or too low an RPM or what.
> 
> Any guidance on selecting the RPM, etc., is greatly appreciated.


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## Dr.Zook (Sep 10, 2004)

Welcome to the RouterForums Eric.


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## BigJimAK (Mar 13, 2009)

Implementitis said:


> This is my first real post on this forum (and for that matter my first real router project).
> 
> I am having trouble with burning on the bit I am using - it is a 1/2" straight and I am using it to cut MDF. I am running the router at about 20,000 RPM and keeping each pass to about 1/8" deep cuts. The router seems to run easy enough and yet every once and awhile, I see burning of the MDF and the blade tips are looking brown. I don't really care about the MDF but I am worried about wrecking the bit. Frankly i don't know if I am feeding too fast or too slow, or running to high or too low an RPM or what.
> 
> Any guidance on selecting the RPM, etc., is greatly appreciated.


Eric,

+1 on BJ's: carbide bits, MDF is very tuff to cut and hard on tools.

About an hour ago I finished adding a second router to my router table (1-1/2" thick MDF), so I made quite a bit of fine dust today with my 1/2" bit. 

Overheating is primarily caused by moving too slowly or having a dull (by wear or burning) bit. When I route MDF I like to used some kind of fence, guide or bearing with it because I've found that I get my best cut and no burning when I keep the router moving right along. That said, the cut depth should never exceed the diameter of the bit.

Please be aware that if you burn a bit once (i.e. turning it blue) it modifies the metallurgy and needs to be replaced (unless you're a metalworker with furnaces, quenching, etc.). Once burned it will never work correctly again. It must be replaced.


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## Hamlin (Dec 25, 2005)

I was going to recommend carbide spiral bits but, I see Bj beat me to it.  

MDF is man made material in which, bits, blades don't like. A burnt bit only becomes a good paper weight.


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## Implementitis (Oct 24, 2009)

Thanks everyone - things seem to be working better now. A big clue was BigJimAK's "Overheating is primarily caused by moving too slowly or having a dull (by wear or burning) bit." Well I was definitely moving slowly ('cause I really didn't know what the @#$% I was doing) so I set up a fence and got that "router moving right along". Presto - no more Smokey the Bear.

I did burn one bit but it turned brown, not blue, so maybe there is still a little bit of life in it. Anyone know how to tell? But frankly it was a cheap one to start with so no big loss. And I did have one good quality bit and there was NO burning on when I ran it.

Finally, hunting through the forum I found a URL to an article called Speeds.pdf at Jesada Tools (being a Newie I can't post a URL so this is my best attempt). Anyway, it was pretty useful for a Newbie, especially if you guys didn't come along.

I'll try to post the resulting "project" (aka "disaster") as soon as i figure out how this Gallery thing works.

Thanks


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## Hamlin (Dec 25, 2005)

Hi Eric,

If the bit has turned blue, it's trashed. The brown color is more likely the MDF itself.


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## fredsintheshop (Sep 10, 2004)

A lot of good advice here so far. On MDF, I always stay with spiral bits. I buy mine as end-mills from an industrial supply house. They are designed to use on vertical and horizontal metal milling machines and the solid carbide ones hold up to a lot of abuse in the wood shop. But remember, the high speed of the bit, or moving the router too fast across your workpiece is what burns it up. So you can slow down one, the other or both, and that should help a lot.


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## radios (Sep 30, 2009)

no one asked you, and you never mentioned it, but were you using STEEL bits? you should use carbide on MDF.


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## davcefai (Aug 3, 2009)

As somebody wrote, the brown colour is probably due to the MDF itself. (resin, glue or both). You can dunk the bit in alcohol or acetone and use a toothbrush to get it off. Leaving it on may contribute to future heating.


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## Implementitis (Oct 24, 2009)

"moving the router too fast across your workpiece is what burns it up" - now I am really confused - when I got that router moving right along (with the help of a fence) all my problems seemed to go away... I would think that that bit edge hitting the same piece of MDF too many times in a second might be my problem...

And yes they were cheap steel bits that were given to me with the Router - didn't want to ruin my good carbide ones on MDF - might have been a bad call...


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## Hamlin (Dec 25, 2005)

Hi Eric,

Again, MDF is a man made material, it's one of the worst materials to work with for bits and blades. As has been said, it's likes to "burn" them up. Get yourself an extra set of spiral carbides. I think you'll find that the spirals work the best.


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## Implementitis (Oct 24, 2009)

Thanks everyone - the MDF project is over and that bit will be given to my son for who knows what (probably launching into space via our potato gun).

Thought people might be curious to see what I was building with the MDF as my first router project. It is a Baby Router Table made of some scrap from the shop. Before I invested in one of those works of art I see on this site, I thought that a Mark I version would be a good idea - that way I could see what I like or hate about a table (or if I even like using a router table). Plus I have a shop that is 10'x15', so some of those tables would look like an aircraft carrier in my shop.

So this table is designed to drop into my bench vise when I need it and be very small (18x27x4) when I don't. I borrowed the ideas from an old Shop Notes with a few ideas from American Woodworker and NYW (would love to build something like the NYW table, but then I might need a shop the same size as Norm's).

The top is the from the former desk of my son's (when he was in college) and the edging is bits of Jatoba flooring from the house reno of a few years ago. The router stays in place with three toggle clamps I found in a box. Money had to be spent on the Estop switch and some T-Track, but fortunately both were on sale at Rockler a while ago...

Next task is to build the fence. Thanks everyone for all the help.


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## radios (Sep 30, 2009)

Implementitis said:


> "moving the router too fast across your workpiece is what burns it up" - now I am really confused - when I got that router moving right along (with the help of a fence) all my problems seemed to go away... I would think that that bit edge hitting the same piece of MDF too many times in a second might be my problem...
> 
> And yes they were cheap steel bits that were given to me with the Router - didn't want to ruin my good carbide ones on MDF - might have been a bad call...


 moving too fast on hard wood or aluminum, but it would have to be MUCH too fast, could, but overheating is usually from moving too slowly, and you'd have to do quite a few cuts on MDF to dull a good carbide bit. they do wear quicker on MDF, but not like one sheet and it's dull.


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## BigJimAK (Mar 13, 2009)

Implementitis said:


> Thought people might be curious to see what I was building with the MDF as my first router project. It is a Baby Router Table made of some scrap from the shop. Before I invested in one of those works of art I see on this site, I thought that a Mark I version would be a good idea - that way I could see what I like or hate about a table (or if I even like using a router table). Plus I have a shop that is 10'x15', so some of those tables would look like an aircraft carrier in my shop.
> 
> So this table is designed to drop into my bench vise when I need it and be very small (18x27x4) when I don't. I borrowed the ideas from an old Shop Notes with a few ideas from American Woodworker and NYW (would love to build something like the NYW table, but then I might need a shop the same size as Norm's).
> 
> The top is the from the former desk of my son's (when he was in college) and the edging is bits of Jatoba flooring from the house reno of a few years ago. The router stays in place with three toggle clamps I found in a box. Money had to be spent on the Estop switch and some T-Track, but fortunately both were on sale at Rockler a while ago...


That's a nice design and well implemented, Eric. I like the look of jatoba since Harrysin first showed what it can look like and I then saw it at my local HW supplier.


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## Implementitis (Oct 24, 2009)

Opps - my wife just corrected me that the wood on our floor (and thus the Baby RT) is kempas and not jatoba. Still it is a joy to work with, harder that rock (it has a janka hardness rating of 1710) and looks great.


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