# Minimum RPM for Router Bits



## joprinz (Dec 19, 2010)

Hello everyone, I'm Joe n I'm New here. Good to be part of Router Forums 

I have built a CNC Router and have a little problem with MDF. I am burning the Bits along with the work piece (I use 1/4" 2 flute Straight Bits to cut out MDF at .2" Cutting depth passes). The problem is something that is discussed widely in many threads. However there seems to be one aspect about router Bits that i couldn't find, The Minimum RPM at which router bits can be run without causing tear. 

The most common solution given for MDF burning problem is to increase feed rates or decrease RPM or both. Now being a Home made CNC my feed rate has a max limit of about 200IPM. So using a 2 flute bit i need almost twice that Feed rate to get a chip load of about 0.013 @ 15000 RPM. So my other option is to reduce the RPM. I'm using a 2.2kW Chinese High Frequency Spindle as my router. So It can run from about 5000RPM to 24000 RPM. But I do not know if it is wise to run a 1/4" 2 Flute Straight Bit under 10000 RPM.

Hope some one can shed some light at a practical lower RPM limit for router bits.

Thanks,

Joe


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## Cherryville Chuck (Sep 28, 2010)

Hi Jo (good to add your first name, we're all friends here),
Not sure there is a lower rpm limit as feed speed is just as important. I have a homemade contraption that turns 10 to 12,000 rpm and it works well with small bits. I have to sand a little whether I am turning 10,000 or 25,000. Can you give me details about the spindle you are using?


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## bobj3 (Jan 17, 2006)

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http://www.routerforums.com/attachm...676205-new-life-dead-router-overhead-view.jpg

http://www.routerforums.com/attachm...-life-dead-router-side-view-wi-depth-adj..jpg
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cherryville chuck said:


> hi jo (good to add your first name, we're all friends here),
> not sure there is a lower rpm limit as feed speed is just as important. I have a homemade contration that turns 10 to 12,000 rpm and it works well with small bits. I have to sand a little whether i am turning 10,000 or 25,000. Can you give me details about the spindle you are using?


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## joprinz (Dec 19, 2010)

Cherryville Chuck said:


> Hi Jo (good to add your first name, we're all friends here),
> Not sure there is a lower rpm limit as feed speed is just as important. I have a homemade contration that turns 10 to 12,000 rpm and it works well with small bits. I have to sand a little whether I am turning 10,000 or 25,000. Can you give me details about the spindle you are using?


Thanks for your reply 

My Spindle is a common Chinese Make 2.2kW Water cooled Spindle. Owing to its lower price It is very common among CNC Hobbyists like me. You can find a few of those listed in Ebay all the time(They ship international too). They come with an ER20 Collet. It is water cooled and requires a VFD to run it. I cant post links as i'm new here but if you are interested in these spindles you could search for *"2.2kW Spindle"* on Ebay. They cost about $400. Pretty neat n capable spindles from my experience (been using one for about 6 months now). They run very quiet and don't blow air downwards like most routers. So dust management is a lot easier. With a good water cooling setup they hardly get hot too.

Joe


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## Cherryville Chuck (Sep 28, 2010)

Thanks Joe,
sounds interesting.


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