# Plunge Routing Deep Mortises & Kick Back



## aronson (Apr 30, 2010)

Hi all,

My setup for this particular operation was a PC 890 w/edge guide, 8931 (type 3) and a Whiteside 2" spiral upcut carbide bit 1/2" shank.

I was routing 9/16" W x 3 1/4" L x 2" D mortises in ash and even with light passes (1/8") I was experiencing frequent kickback. Mostly this occurred at the end of the cut on either the first pass (routing the 1/2" W cut) or on the second pass finishing the last 1/16" inch). I routed the first channel to depth and then worked on widening the mortise - again, 1/8" per cut. I am fresh to routing mortises and certainly have never routed any this deep. I tried various speeds between 10K and 23K to no effect.

Any tips from the more experienced here are greatly appreciated. Googl'ing around all I read are tips to take light passes which I thought I was doing.

Also, the mortises are intact but in some cases widened by the kickback. No way I'm starting over here... what is the suggested approach...? Wedges? Epoxy? I'm also adding draw bores to these mortises so they'll have some substantial backup.

Thanks!


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## Quillman (Aug 16, 2010)

Some data here on morticing with a router.
I'm not surprised you're being surprised.
And with edge guides set for a 1/16" slop with a 1/2 cutter in play: You waste the 9/16/pass, not in 2 separate stages. Templets should also be sized for a single depth/pass; moving the templet for a second stage invites registration and other problems.
Your mortice is quite deep. A slight tip of the router or dislodging the work ever so slightly will have that long grabby cutter in new wood. That recipe is one for self feeding, kick back, a busted cutter.


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## aronson (Apr 30, 2010)

Thanks for the kickback... Er, uh I mean feedback, Quillman. Am I lost without hope? Is there a safe method for cutting these mortises that doesn't involve muscle, mallet and mortise chisel? Or, should I be using a drill press?


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## Quillman (Aug 16, 2010)

Router is good. But you cannot neglect your fixturing. Don't trade this set of problems for worse at the drill press; ace out this router stuff.
It does take time, but it is easy, if that's any consolation!


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## bobj3 (Jan 17, 2006)

Hi

Here's a easy way and No kick back at all 

JessEm Zip Slot Mortise Mill - YouTube

===


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## aronson (Apr 30, 2010)

Quill,

I had mucho better results plunging to depth at the start and end before routing between. Most of the kickback was due to contact with the endgrain at the end of the rout.

Bob, got an extra one of those lying around? ;-)


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## aronson (Apr 30, 2010)

bobj3 said:


> Hi
> 
> Here's a easy way and No kick back at all
> 
> ===


Floating tenons? Pshhh-ah! :dirol:


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## Mike (Nov 22, 2004)

N/A, there are better ways to go about the mortise cut. Two pins like the 
Rockler base plate; a couple roller bearings for centering like this plate by BJ(Bobj3) or a guide bushing in a jig.

PS: Quillman is Pat Warner... you may of read one of his books.


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## aronson (Apr 30, 2010)

Thanks Mike,

In this case the mortises were off center so the guides in your photos might not have worked.

I was incorrect about the width of the mortise - it was actually 5/8". What ultimately worked was plunging to full depth at the beginning and end of the mortise and then sweeping between them in 1/8" depth increments. I had a chop or two but for the most part this worked well.

Pat, I see that you sell guides. I'll check them out as I'm not thrilled with the PC offering. The "micro adjustment" is indeed sloppy as is the method for locking them into the base. I'm thinking of replacing the SS philips head screws with hex studs so I can torque them a bit more.

Or, buy yours.


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