# Tear Out And Best Cutter For Edge Jointing



## Gaia (Feb 20, 2010)

I have some 18mm MDF that I want to edge joint and they are about 300mm long. What diameter and length of cutter, and type of cutter would members suggest I use, speed of running etc?
Also how to avoid tear out at the end and any occurring along edge?
Cheers.


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## Cherryville Chuck (Sep 28, 2010)

Peter you don't normally get tear out when going with the grain unless you are taking a really deep bite. When that happens the cutting edge of the router bit is exiting the wood at a steep angle. I would use a straight bit at least 19mm / .75". Speed is usually determined by bit diameter and at that diameter it would be full speed.


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## Quillman (Aug 16, 2010)

Tearout with MDF?
In my experience, MDF tearout = 0 under all conditions.
Best cutter: Any carbide straight bit, with or without bottom cutting capability, ~as long as the work is thick + 1/8" or so. D.min .75".
Would not sweat flute design; MDF will cut with near dead cutters, very forgiving.
RPM = max, feed rate >20/'.


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## Gaia (Feb 20, 2010)

Cherryville Chuck said:


> Peter you don't normally get tear out when going with the grain unless you are taking a really deep bite. When that happens the cutting edge of the router bit is exiting the wood at a steep angle. I would use a straight bit at least 19mm / .75". Speed is usually determined by bit diameter and at that diameter it would be full speed.


OK thanks just searched MDF on net and no grain so no tear out.


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## Gaia (Feb 20, 2010)

Quillman said:


> Tearout with MDF?
> In my experience, MDF tearout = 0 under all conditions.
> Best cutter: Any carbide straight bit, with or without bottom cutting capability, ~as long as the work is thick + 1/8" or so. D.min .75".
> Would not sweat flute design; MDF will cut with near dead cutters, very forgiving.
> RPM = max, feed rate >20/'.


OK cheers, just searched MDF on net and found out no grain, no tear out.


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## Cherryville Chuck (Sep 28, 2010)

I saw the tear out part and forgot about the mdf part. If you were jointing wood, you probably wouldn't need to worry because you would only be taking a few thousands off at a time. The exception to that is if the grain dived in and out of parallel and there is nothing you can do in that case except maybe try a spiral bit but that will leave one edge fuzzy.


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## Gaia (Feb 20, 2010)

Cherryville Chuck said:


> I saw the tear out part and forgot about the mdf part. If you were jointing wood, you probably wouldn't need to worry because you would only be taking a few thousands off at a time. The exception to that is if the grain dived in and out of parallel and there is nothing you can do in that case except maybe try a spiral bit but that will leave one edge fuzzy.


OK thanks.


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