What is normal router bit life while surfacing round tree slabs

[David Waltin]

In the middle of my first attempt to surfacing round tree slabs and am surprised at how quickly the bit went dull. I am curious as to whether it is me, or the router bit?

I have three slabs which I am surfacing both sides on each slab. The slabs are red oak about 16" diameter (97 years old so it is a dense tight end grain). The tree and slabs were cut about 10 years ago and the slabs have been stored inside and are dry & clean. I am using a CMT 852.503.11 Dado & Planer Bit, 1/2-Inch Shank, 1-1/4-Inch Diameter in an old Milwaukee 5670 router. The router is a fixed speed 26,000rpm which may be a bit fast for a 1-1/4" bit depending which chart I look at.

I started with a new bit. I am taking 1/16" cuts on each pass and the maximum that I have to take off each side to flatten the slabs is about 3/8". By the time I got started on slab #2 (side 3 of 6), the bit has gotten noticeably dull to where it is taking considerable increase in effort to both push the router and also keep the router from riding up due to the downward shear angle of the bit. And the bit is starting to burn the wood face. By the time I got to slab #3 the bit is shot and will not even take a 1/64" cut. I was not able to finish slab #3 with this bit. I have a lot of router and shaper bits. (Only 3 or 4 are CMT). I have never had a carbide router bit go dull like this. Most of my bits are 25-30 years old and still in great shape.

Is it normal to dull a bit this quick while surfacing round slabs? I plane my own wood and have no trouble with premature dulling of my planer blades so I am fairly certain if there were sand in these slabs that i would have realized it.

[Kevin Jenness]

The router is a fixed speed 26,000rpm which may be a bit fast for a 1-1/4" bit depending which chart I look at.

It would be difficult to hand feed that large a bit at 26k rpm without excessive heat. As well, if you are surfacing endgrain slabs with the bark on there may well be grit embedded in the bark, especially if the tree was grown near a roadway with auto traffic. Dry, hard, dense wood makes for more of a challenge. I doubt the problem is with the bit itself although that is possible.

[Mel Fulks]

You need a “ single flute bit “ , a big one. Cuts fast !

[Andrew Hughes]

Too me it sounds like your surfacing end grain cookies. End grain will store dirt and that’s a bit killer.
Have you looked at the bit under magnification is the edge chipped or worn smooth.
I don’t see anyway to know what’s normal too many variables
Good Luck

[Jim Becker]

My opinion...for this kind of work you are best served with tooling that has rotatable/replaceable cutting elements and yes, 26K RPM is way to high for both the size of the tool and for the application. It's causing excessive heat because the chip load is way off...chips are what takes away the heat and at that RPM, the chips start to be dust. I have both Amana and SpeTool insert cutters for flattening type work and my most recent purchase was from SpeTool.

[Tom M King]

Call around to local sawyers with bandsaw mills to ask if anyone has a cookie attachment and can resurface some cookies for you. You will probably have to pay for any band damage but it will still be cheaper than burning up a number of router bits, plus all the time.

https://woodmizer.com/store/Product/index?id=40605

https://www.youtube.com/watch?v=tXK1R0tEJYw&t=17s

[Richard Coers]

There are very few normal/common wear statistics in machining wood. Too many variables such as material density, any grit in the bark, and operators choice of feed speed and depth of cut. in your case 1/16" is way to light of cut and your rpm is too high. as mentioned. A 16" cookie is small and red oak is easy to cut. Sorry to say it's you.

[Brian Gumpper]

I'll second what Jim said about the insert bit if you have that much to surface. Also, heat is the enemy of carbide so if you are running those bits hard and maybe getting some pitch buildup you could be heating it up too much.

[David Waltin]

Thank you for all the responses to my question. I was hoping the old Milwaukee router would have worked for this, but apparently not. I will try again with a variable speed router after I go bit shopping. Thanks again.

[Rod Sheridan]

With that many passes per side (up to 6), you’re cutting your tool life down to less than 17%.

Regards, Rod

[Dave Sabo]

You need a newer, better, more powerful router if you're going to be surfacing slabs. There's really nothing to debate about it. Slower speed and more torque are what's called for.

This is the kind of bit Jim was referencing - it has shearing and scraping cutters:


https://www.amazon.com/SpeTool-Spoilboard-Surfacing-Replacement-Flattening/dp/B0C8HDXSTB/ref=asc_df_B0C8HDXSTB/?tag=hyprod-20&linkCode=df0&hvadid=674152721718&hvpos=&hvnetw=g&hvrand=11122300834139215426&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1015392&hvtargid=pla-2205228711551&psc=1&mcid=aa248989dd893e9694d09daf4a62a9e9