When is a router bit too dull?

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Forum topic by oldnovice posted 07-22-2015 04:30 AM 3090 views 0 times favorited 11 replies Add to Favorites Watch
View oldnovice's profile


6900 posts in 3394 days

07-22-2015 04:30 AM

Topic tags/keywords: router question

I was doing an inventory of my router bits to get an idea of how many I have and, at the same time, to categorize them; i.e. carbide/HSS, piloted, and edge forming when it came upon me that some of these bits are very old and may/may not be good (not sharp) any more!

My question is, what is a simple way to determine if a bit is sharp enough or worn out?

-- "I never met a board I didn't like!"

11 replies so far

View pjones46's profile


1001 posts in 2669 days

#1 posted 07-22-2015 04:52 AM

You may not be able to tell if a router bit is dull just from looking at it. You may need to check the bit’s cutting performance and ease of use – dull bits will be difficult to move through material, even softwoods.

Dull cutting edges will burn the surface of the material rather than slicing through it.

A bit that leaves a rough finish when it usually leaves a smooth one is also likely to be dull.

If your router bit is displaying these characteristics, it is probably time to think about resharpening.

-- Respectfully, Paul

View TheFridge's profile


9608 posts in 1512 days

#2 posted 07-22-2015 05:10 AM


-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View DeLayne Peck's profile

DeLayne Peck

545 posts in 2228 days

#3 posted 07-22-2015 09:33 AM

I usually test my router bit in the same material I am going to shape. I am looking for the pace and speed setting I can move at to get a smooth profile with burning.

There are lots of fine diamond hones on the market. I like to give bits a shot of pitch remover and a few laps with the diamond stone.

-- DJ Peck, Lincoln Nebraska. Lord, keep your arm around my shoulder and your hand over my mouth.

View Dutchy's profile


2987 posts in 2195 days

#4 posted 07-22-2015 12:02 PM

I agree what is said above but when a TC router bit on his cutting top is changing color from “black too white” he,s dull.


View dhazelton's profile


2771 posts in 2323 days

#5 posted 07-22-2015 01:45 PM

You can usually feel the cutting edge to see if it is sharp or is smoothed over. I have a Drill Dr and it works great for twist bits. Spade bits I usually use a small diamond file on.

View madts's profile


1862 posts in 2366 days

#6 posted 07-22-2015 02:42 PM

I was taught, that if the carbide or HSS can scratch you nail easily you are in good shape.

quick rule of thumb nail :)


-- Thor and Odin are still the greatest of Gods.

View Bill White's profile

Bill White

4949 posts in 3987 days

#7 posted 07-22-2015 02:48 PM

I’m with Madts. I also touch ‘em up with a diamond paddle.


View moke's profile


1182 posts in 2803 days

#8 posted 07-22-2015 04:01 PM

+1 with the hone….I have extended the life of many bits. At certrain point though, they are done.

-- Mike

View TopamaxSurvivor's profile


18290 posts in 3702 days

#9 posted 07-22-2015 06:00 PM

I was taught, that if the carbide or HSS can scratch you nail easily you are in good shape.

quick rule of thumb nail :)


- madts

That is my “rule of thumb” for most sharp tests ;-)

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View oldnovice's profile


6900 posts in 3394 days

#10 posted 07-26-2015 06:10 AM

Thanks everyone!
After checking my 60+ older bit I have no thumbnail

-- "I never met a board I didn't like!"

View robscastle's profile


5102 posts in 2230 days

#11 posted 07-26-2015 07:36 AM

Yeeee….dont do it with the machine on!!

Plus you can also check it in the light if there is a shiny edge or refelection its time to sharpen.
Also dont forget to check the bearing for free movement and add a couple of drops of oil for good measure, they are only small but work hard!

-- Regards Rob

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