# Routing deep mortise



## Dalec (Feb 13, 2009)

I am in the process of building a workbench and have eight 2-1/4" x 1-1/2" x 3" deep mortises I need to cut. Of the many ways I could go about producing these mortises, it seems using my plunge router would result in cleaner and more accurate mortises. 

How would you recommend I go about routing a deep mortise: process?, type of bit (most plunge bits I have seen don't have the length to cut that deep)? and where to get such a bit if one were available? 

Thanks,

Dalec


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## bobj3 (Jan 17, 2006)

Hi Dalec

I would suggest using a spade bit to hog out most of the wood and then use the bits below to clean up the hole with a template and/or brass guide on your plunge router base plate.

1 pc 1/2"SH 2-1/2" Blade Top Bearing Trim Router Bit - eBay (item 130425183413 end time Sep-25-10 15:53:21 PDT)

1 pc 1/2" SH 3" Blade Extra Long Straight Router Bit - eBay (item 130426568658 end time Sep-29-10 16:37:46 PDT)

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Dalec said:


> I am in the process of building a workbench and have eight 2-1/4" x 1-1/2" x 3" deep mortises I need to cut. Of the many ways I could go about producing these mortises, it seems using my plunge router would result in cleaner and more accurate mortises.
> 
> How would you recommend I go about routing a deep mortise: process?, type of bit (most plunge bits I have seen don't have the length to cut that deep)? and where to get such a bit if one were available?
> 
> ...


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## istracpsboss (Sep 14, 2008)

Hi dalec

3" bits are available, but you will probably find they exceed the travel of the plunge so would make using them for such deep mortising complicated. Ones like 1 pc 1/2" SH 3" Extra Long Flush Trim Router Bit - eBay (item 130426115276 end time Sep-05-10 11:23:34 PDT) with the bearing removed might do. Better still
1 pc 1/2" SH 3" Blade Extra Long Straight Router Bit - eBay (item 130426568658 end time Sep-29-10 16:37:46 PDT)

I must stop looking on that web site. There are too many temptations !

Cheers

Peter


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## Dalec (Feb 13, 2009)

Thanks Bobj3. 

I got stuck in routing out the entire mortise. Had not even thought about drilling out most of the waste before using a trim bit to clean up the mortise.

Dalec


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## istracpsboss (Sep 14, 2008)

Snap ! I was looking while you were writing, Bob !

Cheers

Peter


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## Dalec (Feb 13, 2009)

Peter,

Thinking with bearing guided trim bits, that I could gain some additional depth by using two different length trim bits so I can step my way down to a deeper mortise or use differing thickness template material and step down that way. Don't know if this would gain me much more depth however. 

Dalec


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## bobj3 (Jan 17, 2006)

Hi Dalec

Once you clean out the hole down ,than route the hole out to say 1 1/2" the rim of the hole will give you a nice edge to ride on with the bearing or the brass guide template..I have push my bit to 3 1/2" deep without any error..

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Dalec said:


> Peter,
> 
> Thinking with bearing guided trim bits, that I could gain some additional depth by using two different length trim bits so I can step my way down to a deeper mortise or use differing thickness template material and step down that way. Don't know if this would gain me much more depth however.
> 
> Dalec


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## Dalec (Feb 13, 2009)

Thanks Bobj3 and Peter. 

I appreciate the suggestions and can see the solution.

Dalec


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## Quillman (Aug 16, 2010)

Key here is good and repeatable/indexable fixturing; without it , forget my proposal.
Indeed drill out most of the waste. Then rout all mortices with with generic HSS cutter maybe 1/2 x 2-1/2 long. Stay inside of the net dimensions x ~1/16" all around.
Now change to long (4-5" OAL) SC up-spiral or another longer HSS straight bit to waste to depth and width. All stock most go back into the fixturing just the way it came out in step one. Note this longer cutter will already have an inch or so of projection whence the motor head is all the way up the tubes. So take these first, tho modest cuts, with care.


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## Dalec (Feb 13, 2009)

Thanks Quillman. 

I really appreciate the responses I have gotten. It is like talking over a problem with a number of people in person and as the discussion continues suggestions begin to form into a process that will work for me. Quillman, even when I thought I had it figured out, your description of how to go about it, added to my thinking about what is now my approach.

Thanks everyone who had contributed your suggestions.

Dalec


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## Phil P (Jul 25, 2010)

A belated suggestion for you. I use deep pocket cutters like these from Wealden Tool in the UK in my Trend lock mortising jig (Trend make similar cutters, but they cost more) and I've recently started using the 16mm (5/8in diameter) x 150mm long (6in) cutters to produce mortises 85mm deep (3-1/2in) x 30mm wide (1-1/4in) x 100mm (4in) long in pine using a deWalt DW625 router, a 30mm guide bush and a home made plywood template jig. The trick is to be very gentle and take passes of only 3 to 5mm (1/8in to 3/16in) depth each time.

I've fitted hundreds of house/office door mortise locks using the smaller 12mm diameter cutter and where the cutter doesn't go quite deep enough I simply hog out the last bit of depth with a corded electric drill and an appropriatly-sized spade bit


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## Raymondabel (Dec 18, 2009)

look arround & find somebody that have something like this

General 75-050, 5/8 inch hollow chisel mortiser

this realy do that king of job!


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## Dalec (Feb 13, 2009)

Raymnndabel,

Unfortunately, I am out of room in my garage/workshop not to mention saving $'s to buy wood for my projects. Have been test cutting mortises in scrap by drilling out waste and cleaning up with a long straight router bit and shop made mortising jig. It's coming along pretty well. Think I can get accurate, clean mortises to the depth I need.

If I find my woodworking going toward more mortise & tenon joinery, I may have to find the space for a mortising machine. But for now, I am set. 

Thanks again.

Dale


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## bertsmith (Apr 21, 2011)

Hi

Interesting words 

I'm aiming to create some 5inch deep tenons.

The links in this posting are no longer available and a search on ebay for extra long straight router bits yielded resutls for 3inch lengths at most.

I am looking for a pillar drill for cutting out the bolk of the material but want to get the best finish possible using a router. 

My question(s) is: would collet extenders work and are they effective and accurate enough?


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## bobj3 (Jan 17, 2006)

Hi Bert

If you are going down 5" deep you will need to used two tools, 1st the long router bit and than the sq.corner chisel.

1 pc 1/2" SH 3" Blade Extra Long Straight Router Bit | eBay

Super Carbide Tools items - Get great deals on Single bit, 2 pc Set items on eBay Stores!

" collet extenders work" = NO


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Cabinetmaker Chisel
MLCS Corner Chisel



bertsmith said:


> Hi
> 
> Interesting words
> 
> ...


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## bertsmith (Apr 21, 2011)

bobj3 said:


> Hi Bert
> 
> If you are going down 5" deep you will need to used two tools, 1st the long router bit and than the sq.corner chisel.



hi Bob

are you proposing using the router for the 1st 3 inches and then the chisel for squaring the corners and for cutting the final 2 inches down?

Rob


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## Phil P (Jul 25, 2010)

Raymondabel said:


> look arround & find somebody that have something like this
> 
> General 75-050, 5/8 inch hollow chisel mortiser
> 
> this realy do that king of job!


Hollow chisel mortisers generally won't cut 4in depth, at least not in the smaller sizes like 5/8in. Reason is partly that the chisel ejects waste through the slot/slots in the side(s). The smaller cutters simply aren't designed to cut that deep

Phil


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## Phil P (Jul 25, 2010)

bertsmith said:


> I'm aiming to create some 5inch deep tenons.
> 
> The links in this posting are no longer available and a search on ebay for extra long straight router bits yielded resutls for 3inch lengths at most.


Then allow me to introduce you to Wealden Tools. They sell a "family" of *deep pocket cutters* (see here) which will allow up to about 4in depth of cut - probably the longest cutters anyone sells in the UK. Note that these _aren't_ eBay specials; there simply aren't any cheap Chinese knock-offs available in these sizes. Trend do a similar range of cutters which are also available in the USA, although they do cost somewhat more than the Wealden ones (and having used both I see no advantage in buying the Trend product in the EU). You need to start with a shorter cutter first and work up to the longer ones. Best used with a template and guide bush. I use the 120mm ones regularly to do lock mortises in door sets (using a Trend lock mortise jig) and whilst they are limited to about 3in depth of cut extra depth is easily obtained by finishing the cut with an auger bit. 

As to getting a square corner I'd ask if it is strictly necessary.The hammer type corner squaring chisels aren't particularly accurate and in any case their depth is limited. They're really designed for squaring the corners of hinge recesses. The so-called corner squaring chisels sold by Sorby, Crown, _et al_ are more correctly referred to as "bruzzes". They're often not accurately square, have a limited depth of cut and really weren't designed for this task. They were originally a tool used by wheelwrights to quickly square out spoke holes where absolute accuracy isn't essential as the main aim was to stop the spoke from turning in the mortise (the spoke may well have been oval in section) and in any case the spoke tenons often have four shoulders which completely mask the mortise hole



bertsmith said:


> I am looking for a pillar drill for cutting out the bolk of the material but want to get the best finish possible using a router.


But why? Neither the insides on the mortise nor the faces of the tenon will ever be seen. Yes, I agree that a "piston fit" is very nice in theory but in the real world it isn't 100% essential. I agree that a pillar drill with ship's augers would be the best approach to making the majority of the cut but I just can't see why a perfect finish is required. For a couple of hundred years carpenters chiselled out mortises by hand with little more than a mortise gauge, a mallet and a pig sticker (answers please on a postcard.....). They weren't perfect, but they are often better than the result you'd get from a sqaure chisel mortiser.



bertsmith said:


> My question(s) is: would collet extenders work and are they effective and accurate enough?


In a word, no. The collet extender will give you maybe 1/2 in extra depth of cut in this situation. The extender by its' nature has to have a collet holder and nut at the bottom end and these are obviously larger that the shaft of the cutter. That means that it wouldn't be possible to position the extender too far below the base of the router. The 1/2in deWalt, Bosch, Makita and Hitachi routers I've used all allow the standard collet to drop pretty much to the level of the underside of the baseplate in any case so the only extra you'd get would be the thickness of the template (i.e. 1/2in or less). I also thick it would be dangerous to use these extremely long bits in an extender. Unless the deep pocket cutter is seated well into the collet vibration can build up and wreak havoc with the quality of the cut - and in hardwoods that cut is limited to 3 or 4mm per pass to ensure that you aren't over stressing the cutter (in chipboard door cores you can get away with 10mm per pass)

One more thing I'd like to know is why you need to get a 5in deep tenon? That's the sort of depth generally used in very heavy doors and external gates. Commercially these would be worked by a very large chisel mortiser, such as a Wadkin DM/V or more likely by a chain mortiser and is really outside the scope of a hand router

Regards

Phil


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