CNC users - Mortising bits?

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Forum topic by JohnMcClure posted 03-31-2019 02:07 AM 283 views 0 times favorited 3 replies Add to Favorites Watch
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622 posts in 1028 days

03-31-2019 02:07 AM

CNC-using Lumberjocks,
I have a project coming up that requires a lot of mortises in hard maple. I’m happy to do it because I have a bad-a new CNC router with 2HP spindle and up to 1/2” shank. I plan on using it to hog out 20 mortises in hard maple; each mortise will be about 3” high x 0.5” wide x 1.5” deep or deeper.

Then I looked at the endmills I have and realized I need to buy a new one for this. What bits do y’all recommend for this application? Is there an extended reach endmill that will allow me to go deeper than this? The vast majority seem to have a 2.5” overall length and only 1” or 1.25” fluted length.

I did find an Amana bit that’s super long but the catalog says it’s for slot mortisers only, NOT for CNC.


-- I'd rather be a hammer than a nail

3 replies so far

View Mainiac Matt 's profile

Mainiac Matt

9127 posts in 2716 days

#1 posted 03-31-2019 04:06 AM

I’d try a spiral up so you can extract the chips. You might get a hairy edge at the top, but if your tennons have a shoulder, it will be covered.

You could probably use a straight fluted bit if you blow air into the hole to remove the chips during the cut.

The Onsrud catalog is your friend

-- Matt -- I yam what I yam and that's all what I yam

View Tmanpdx's profile


23 posts in 99 days

#2 posted 03-31-2019 06:16 PM

I use this and have had great experience with it:

It’s a Whiteside RU5200T 1/2 shank 2” cutter length.

Also CMT makes some nice ones:

View DS's profile


3163 posts in 2808 days

#3 posted 04-01-2019 01:41 PM

Onsrud is good, Allied tool is also good. Sometimes is comes down to what is available in your area.

Solid Carbide is brittle and the longer lengths apply more leverage to them and make them more susceptible to breaking, so care must be taken with longer bits.

They are out there for sale, but they start to get pricey.
I think the 5/8” diameter low-helix 2-flute up-cutter we got with 2.5” of active cutting length was $345.00, It is a LOT of carbide, (nearly 5” long) but a beast for material removal.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

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