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cutting mortises and tennons?

Started by Dan_Shade, May 14, 2006, 09:12:20 AM

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Dan_Shade

How do you guys cut and handle large timbers and keep things tight and accurate, all while allowing easy fitment together?

I've been playing around the past few days with some 4x6 and 3x4 timbers making a small wagon frame, I've had a heck of a time handling the big stuff.  I ended up cutting the tennons with a small chainsaw,and then the mortises I started off with my delta mortise machine, but gave up on that and went to a drill and chisel.  I got it done, but it's ugly.

Is practice the secret?  even handling this small stuff wore me out, there has to be a trick or two!
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Dan_Shade

I found this: Cutting a Tenon on a Timber thread
am I the only hack that uses a chainsaw to cut tennons (tenons)?
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Dan Miller

I'm probably in the minority, but I do all of my framing with hand tools. The largest timber I've cut so far is an 8x9x26'. I've also built my frames out of pine or hemlock, using white oak for sills.

Cutting is with hand saws - I use an 8ppi crosscut and an old Disston rip saw. The modern Stanley Sharptooth saw is also excellent for crosscutting, is cheap enough to be disposable, and can easily survive a couple of frames.

Waste from mortises are hogged out with a boring machine (fairly common in the antique tool market), and then the mortises are cleaned up with a framing chisel. Peg holes are bored with a brace and bit.

All mortises and tenons are checked using a combination square as depth gage, and the arms of the framing square the check mortise width (assuming you're using 1-1/2 or 2" tenons.

To ease assembly, tenons are tapered in length on all four sides. The housings around mortises are dished to compensate for radial shrinkage of the timber.

Various hand planes can be helpful for trimming tenons, shoulders and housings. I've also hand-planed the interior surfaces of two of my frames.

I don't have any machinery for moving timbers, so I do that "by hand" also. Use your stickers and sawhorses as pivot points - place them near enough together that you can use the weight of your timber to advantage when moving them. I use a cart made of wheelbarrow wheels (wish they were larger diameter) top move things around the yard. Loaded with the wheels amidships of the timber, it takes little effort to move them around. My raisings were by hand, assisted with a gin pole.

I'm not a professional (at least not yet), so I can afford to take more time, perhaps than the pros. However, I think for a lot of it, the hand tool approach is not that much slower than the power tool approach. For me, the hand tools are more accurate.

Its well worth taking a workshop if you can. I learned from Jack Sobon and Dave Carlon at their Hancock Shaker Village workshop.

Cheers,
Dan

scsmith42

For occasional small work, here on the farm I've used a plunge router with a straight bit to make the mortises.
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

Raphael

  All my experience is recent so my approach has been evolving .

  I'll rip scarf joints and long through tennons with a chainsaw.  I can rip to the line (plane close) using a Logosol Timberjig for long straight rips but just free hand close to the line when cutting on a slope and then take it to the line with a slick and hand plane.

  A really long angled shoulder cut I might make with a circular saw if it's convienant otherwise I've got an old panel saw blade made into a copy of the Diston thumb hole rip saw.

  Otherwise I've become totally addicted to my Japanese handsaw (340mm?) and use it everywhere I can.  I find I can cross cut the shoulder and rip a near perfect tennon 95% of the time with this one tool.  Prior to purchasing it I'd cut the shoulders w/ a good stiff backsaw and do the rest with a chisel or rip saw if the tennon was large enough.

  I use an old boring machine for mortices, for what I've done so far and intend to do it's the most economical solution.  You can get a decent Snell or Swan w/bit for the price of a good plunge router and it'll still give good service in another 100yrs.

  Corner chisels can be useful cleaning out 1.5" mortices (less so in 2") but take more time and effort to keep sharp, I left off using one except where I had problem spots.
  A good 1.5" framing chisel and the patience to learn are your best tools...  I'm still working on the patience part. ;)
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

Jim_Rogers

Dan:
I guess it depend on what level of workmanship you want to do.
You can use a chain saw to removed larger volumes of wood from the sides of a tenon or the center of a mortise, but it is not a precision wood cutting tool.
For accurate joints that aren't sloppy you need to make precise cuts.
It again all depends on the level of detail you want in the finished project.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

srjones

For the long part of tennons (cheek cut?) I use a Prazi beam saw with the chain ground down to a good ripping angle.   With a little practice and some jigs, I've been able to get within 1/32" of a 2" tennon.

A plunge router with a pattern bit will make good mortise but the Makita chain mortise will make them a lot faster.

Everyone has hobbies...I hope to live in mine someday.

Raphael

Greetings srjones:
How well has your Prazi stood up to the the work load?
How often do you stop and oil it?

I've got one I haven't used much and is still setup w/ the original chain.
  My chainsaws are all setup to run Logosol's ripping chains so I can rip the same 1/32 using the timberjig, I'll usually set the tip of the bar 1/16-1/8 high to make sure I don't cross the line I can't see.
... he was middle aged,
and the truth hit him like a man with no parachute.
--Godley & Creme

Stihl 066, MS 362 C-M & 24+ feet of Logosol M7 mill

srjones

Hi Raphael,

The beam saw is holding up very well.  I give it a quick shot of veggie (canola) oil every few cuts to keep it clean, cool and lubed.  The manufacturer clames it only needs a shot of silicon spray once in while but I find that stuff is pretty nasty so I avoid it.

Like most things woodworking...the key to a good cut is a very sharp blade (or chain in the case).
Everyone has hobbies...I hope to live in mine someday.

bigmish

I'm new to timber framing and come from a furniture background. As such I'm considering creating templates for a plunge router and cutting all joints like so:
1. scribe the joint
2. cut the waste with a drill/saw to 1/16 of the sribes
3. pattern  route the joint to the depth achievable by the bit (around 3") with the router riding on the reference faces when possible
3. use the freshly routed surfaces as bearing surfaces for chisels to complete the depth of the cut

While this seems like an extra step (the routing) this should crate extremely accurate joints (I can get dry wood joint with in 1000s of inch in accuracy using pattern raturers). The additional accuracy seems to me to justify the additional time.

Any thoughts?

srjones

hey bigmish,

I like your ideas on using a plunge router.  If you're just roughing it out first, wouldn't you be able to get to within a 1/4" or 1/2" before cleaning it up with the router?

Also, what size router bit do you use?  I primarily use a Freud 1/2" shank  1 1/8" (d) x 1 1/2" (l) bit with a top pattern bearing.  However, I'd really like to find something longer.

At the risk re-opening an old topic about tolerances you might consider this:

1. The joints that people see would be worth the effort to make tight and clean.
2. The tighter the moritise and tennons fit, the tougher its going to be to get the thing assembled.
3. Instead of thinking in terms of 1000ths, think 100rds or 10ths.  This might be hard coming from a furniture background. 

Everyone has hobbies...I hope to live in mine someday.

hardworker

Bigmish,
I came from a home furniture craftsman direction,  too. Last summer I built a sobon garden shed with eastern white pine from, sawed by Jim Rogers. I used a 1 1/2" augar bit to clear out holes and a timber framing chisel to clean things out.  I used  a circular saw and varied cut depths for housings, tenons, etc..
I carried my rafters down to my shop and used  my bandsaw for certain cuts.
One thing people have not mentioned is that generally/ many times the timbers are not seasoned. This is quite different from the hardwoods we furniture guys are usually working with. It is 10X easier to cut the material as it is much softer. 
As far as accuracy, "carpentry" accuracy is required, not furniture accuracy.  The first step in furniture building is milling. Jointing, planing rough length cutting, so everything is square and perfect.  This doesn't happen in TF. If my memory is correct, the  6" square full cut material varied over all pieces by 1/2" .   
Plus, if you are using unseasoned wood, the wood is going to change anyway.
For assembly, you dry fit before erection anyway.
I built up 1 bent and got that right and then built the other two. Same for the rafters, beams, etc...

I understand your thoughts about the jig, as I build them too.  But for TF there really is no need. But you should do what you think works.  You already know wood and you should use your best judgement for what works with you.  A big advantage for a furniture maker  is the measuring capability, and visualizing the joinery. There can be as many joints in a dressor as in my whole shed.

The Sobon shed is pretty small so there aren't that many joints. Cutting joints is a pleasant activity. You build a few sawbucks, lug around  some timbers,  you're out in the sun. Router noise would just disturb things, anyway.
Jonathan

Jim_Rogers

Jonathan:
I can't seem to remember ever sending out a timber for your shed that was either oversize or undersized a 1/2" !
That just doesn't sound right.....

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

hardworker

Jim,
It was just kind of a rough estimate from memory, maybe it was closer to 1/4". The 1/2" was a minimum to maximum number, not an oversize. The smallest piece vs the largest piece I had. Even 1/4" would be huge for a cabinet maker.
I was very happy with the material.  The quality was excellent.  
I do a lot of work around the house, and don't think a lot about most of the work I've done, but I often think about working on the shed.   
Jonathan

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