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Discussion Starter #1
About a year and a half ago I bought an inch and a half diameter CMT router bit with the intent of using to plane a wood surface. I am now in the process of building myself a workbench and want to use this bit for surfacing. I got to looking at it and noticed it has about a 9 degree negative rake angle. Will this cause me any problem? I plan to give it a try in a week or two regardless, but I was wondering what to expect. This bit has a bottom mount bearing,that is, the bearing is between the cutter and the shaft. I think it is a rabbeting bit, but I want to use it to plane a surface. Is this what a negative rake bit is used for? Any information will be most appreciated, thank you.
 

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Sawdust Creator
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If there is a bearing below the bit......you can't surface with it......do you have a picture of the bit?
 

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crosseyed & dyslexic
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I'm thinking it's a pattern bit, or a top bearing bit like this?

I don't I've ever seen what you are describing, can you post a pic?
 

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John
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About a year and a half ago I bought an inch and a half diameter CMT router bit with the intent of using to plane a wood surface. I am now in the process of building myself a workbench and want to use this bit for surfacing. I got to looking at it and noticed it has about a 9 degree negative rake angle. Will this cause me any problem? I plan to give it a try in a week or two regardless, but I was wondering what to expect. This bit has a bottom mount bearing,that is, the bearing is between the cutter and the shaft. I think it is a rabbeting bit, but I want to use it to plane a surface. Is this what a negative rake bit is used for? Any information will be most appreciated, thank you.
I'm not exactly sure what you mean by "negative rake" but many rabbeting bits have what I call a "shear" angle on the cutter which leaves smoother sides on the rabbet. It should still plane OK because you are just concerned with the cutting edges on the end of the bit. Those cutters likely do not go across the full diameter of the bit so plunging is not an option, you must start off the edge and move in. I'm not sure I have ever seen a rabbeting bit with a shank mounted bearing though.
I use a bit like this
http://www.ebay.com/itm/1-pc-1-2-Sh...953218283?pt=Routers_Bits&hash=item20d1776ceb
Except mine is only 1-3/4", when it wears out I will likely go to this one. :smile:
 

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Discussion Starter #5
Reply to helpful answers

Thanks,all. It is a top bearing bit. If you look at a side view of the bit with the shank at the bottom, it is shank,bearing,cutter,in that order. A neutral rake cutter will have the edge of the cutter in line with the shank,on the centerline. A positive rake cutter will have the leading edge of the cutter contacting the wood ahead of the centerline, negative rake will contact the wood behind the centerline. It is said,in metalworking,that a positive rake cutter cuts the metal off, and a negative rake cutter pushes the metal off. Of course,metal and wood do react differently in some respects when being machined. I asked this question on another forum and was told I should take light cuts,as the negative rake might tend to lift the router,this does make sense. I am thinking it might leave a fuzzy surface where a neutral or straight cutter or one with a positive rake would cut more cleanly. I guess I will find out for sure when I give it a try.
 

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Discussion Starter #6
Maybe i will use my#5 Jackplane.

I have been encouraged to use my Jackplane, that I could do it much faster by hand.It is a chance to bolster my mastery of handplanes, my skills in that area are sadly lacking. I will start on the bottom surface and see which method gives superior results.
 

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where's my table saw?
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it depends on the wood and surface finish you want

The 3 types of bits are:

Down shear bitleaves a clean top surface:
http://www.ebay.com/itm/Amana-Down-...204?pt=LH_DefaultDomain_0&hash=item56516ffcf4

Up cut bit leaves a clean bottom surface:
http://www.ebay.com/itm/Freud-75-10...491?pt=LH_DefaultDomain_0&hash=item1e7d74153b

Straight cut flush trim may leave some burr on either or both surfaces:
http://www.ebay.com/itm/1-pc-1-2-SH...976414084?pt=Routers_Bits&hash=item20d2d95d84

You may have one of these as rrbrown posted...link didn't work for me:

http://www.infinitytools.com/Dado-Planer-Router-Bits/products/1016/
Dado & Planer Router Bits
These Dado & Planer router bits allow you to clean out dadoes, rout signs, finish rough stock, and even remove paint or varnish! Our unique down shear design produces an extremely smooth surface and our extra-thick micro-grain carbide tips on our dado & planer router bits allow for multiple sharpening.​
 

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Discussion Starter #9
To rrbrown

Yes,that is the exact same bit that I have. Good to hear it is designed to leave a smooth surface.
 
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