# How to make open slot mortises in large timber?



## ajrjmr (Sep 22, 2008)

I need to make an open slot mortises in the end of 6"x6" timber (dressed to 5.5"x5.5"). Each mortise needs to be 9" deep by 3.5" wide, centered on the end.
The timber is pressure-treated pine (probably yellow pine).

The tools and resources I have on hand are:

* 10" radial saw, max depth of cut 3.5" Assortment of blades including dados
* Floor drill press w/ mortise attachment. Drill press spindle travel is 6", mortise bits and chisels work to max 3" depth.
* 12" band saw with 12" depth of cut; assortment of blades
* 3hp plunge router, longest bit will cut to 2.5" depth
* 4.5 amp reciprocal saw with 6" and 12" blades
* 10" table saw with sliding table, max depth of cut 3.5"
* Generous assortment of consumer-level portable power tools, 
clamps, and hand tools 

The timbers are 10 feet long. They will weigh between 80 and 100 lbs each, a bit clumsy to feed into a stationary saw, but it could be done with auxillary rollers.


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## Big Dave (Sep 16, 2006)

When I make mortises in big timbers I will hog out most of the material with a forstner bit first then clean it up with a chisel.

This is what you need.


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## Handyman (Jan 2, 2008)

I would drill the most of it out with a wood bit of any kind and then clean the rest with a wide wood chisel.


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## cabinetman (Jul 5, 2007)

You didn't say how many, but you could use your sawzall with a coarse blade, or a rip hand saw, or bowsaw for the deep cuts. Use a drill bit to drill bordering the 3.5" line, and then do a cleanup with a slick, or a mortising chisel, or a wide bench chisel.


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## mainzy (Mar 8, 2008)

Ajrjmr;
You could use your band saw to cut out a 12 inch piece. Then glue and screw 3 inches back. 

You could also make a jig for your plunge router. Do both sides then chisel out the rest. 

What are you making? 

God Bless:Mainzy


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## Tony B (Jul 30, 2008)

*Drill a hole in the solid end of the mortise.*

make some kind of support to support the weight of the 10' long timber and cut the cheeks with a band saw. Then square up the bottom with a chisel.


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## GeorgeC (Jul 30, 2008)

I have edited this because when I first read I did not see the words OPEN SLOT. Wrote a bunch of garbage that did not apply.



George


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## Tony B (Jul 30, 2008)

*GeorgeC*

He asked for an "Open Slot Mortise" "Each mortise needs to be 9" deep by 3.5" wide". On an open slot mortise, one end is open.
At first, I read the question quickly and it threw me off balance also.


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## pianoman (Jan 16, 2008)

I would build a guide saddle (1/4" thick) with fences for a hand held router. Plunge a little at a time with a 1/2' straight bit as deep as you can go... then flip the beam...route the other side...clean-up the rest by drilling, hand sawing, and then chissel to size. Rick


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