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Fixing sloppy joinery

Started by TFwannabe, September 19, 2018, 02:07:53 AM

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TFwannabe

Hello all - after lurking on this blog fo quite a while i thought I'd draw on the collective wisdom to move me along. At 65, I thought I'd  scratch a long-standing itch and try my hand a timber framing. My first project is what should be a simple 10x14 shed-roofed shed.

I've read everything I can get my hands on, watched hours and hours of video but the gap between theory and application is a wide one. Where I'm located it's hundreds of miles to anybody who even knows what a timber frame is, so I'm my own onsite teacher...and I've not got the best student to work with. So far it's been an exercise in humility.

Now, I know nobody posting in this forum other than me has ever made a mistake ;-) , but I have and do on a regular basis.  

My latest challenge is figuring what to do to fix my sloppy joinery. I've checked an old thread on acceptable tolerances.  

Tolerances in frame construction part two in Timber Framing/Log construction

I'd hoped that when I saw 1/8 and the like, the references were to feet, not inches, but my hopes were dashed when I saw other references to  the thickness of a business card. :D

Cutting new timbers is not an option given the availability of material and budget. So what's a wannabe to do - -how can I make adjustments to compensate for a couple M&T joints with as much as 1/4"+ of slop?

I'd be thankful for any advice.

Jim_Rogers

Put in some 1/4" shims pushing the joint together in the correct direction.

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

TFwannabe

Well thanks for the straightforward response Jim. This solution was too obvious for me to think it would work. It was my naive expectation that there would be some sort of TF voodoo called for. 


Jim_Rogers

As we are usually cutting joints in green timbers we try and make our joints the correct size. Not too big and not too sloppy, as the timbers are going to dry out and shrink some, we don't want them to be sloppy now because they will be sloppier later on.
Due you best to not make your joints sloppy.

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

Ljohnsaw

Quote from: TFwannabe on September 19, 2018, 02:07:53 AM

Tolerances in frame construction part two in Timber Framing/Log construction
What a great read!  After cutting my first set of brace pockets (that will be hidden anyway), this couldn't have been more timely!  Cutting into a 8x14x26' sill - making two 14"x14" lap joints at the ends, four brace pockets, four 6" deep notches (for Simpson straps later) and a 2x10 post tenon pocket - 6 hours later I have a new appreciation for tolerances.  My forth pocket went a whole lot faster than the first!
So for 11 "½ joints" that comes to 1 hour per joint, though I hope my tenons go quicker then the mortises.
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

D L Bahler

In Switzerland I was taught that where visual concerns weren't that important, tolerances needed to be within 2mm or about 1/16". Where they were highly visible they should be within 1 mm, or about 1/32". That's quite a bit more than the "business card thickness" mentioned in the link, but as is pointed out that is preference, and I have no wish to argue against it. (You know the saying; opinions are like rear ends: Everyone's got one, and everyone thinks the other guy's stinks)  

It's also worth noting that the direction of tolerance is important, as is the relative position of a joint, and whether the actual mortise and tenon part of the joint does anything other than locate the timber.
So for example, if I have a bearing tenon and I cut the mortise 1/4" to tall, it doesn't matter. The top of the joint doesn't matter in this case anyway. Just plug it if you don't like the looks of it. If I locate the bottom of the mortise 1/8" too low, then it does matter. It would need to be shimmed. It's not unheard of to see a mortise in an old barn cut inches too low, then re-cut and a wood block shoved in under the adjoining tenon. I always worry about the parts of the joint that matter the most. I don't fret things like mortise depth or other aspects that don't affect the engineering properties of the joint (in fact I prefer my mortises to be a bit deep, as it allows me to cut them more quickly) 

There are some cases where it really doesn't matter if the joints are tight at all. Floor joist pockets, for example, can have some horizontal slop because they'll be secured by the flooring anyway. Doesn't mean you shouldn't try to make them nice, just that it's not detrimental if they're not perfect. 


Jim_Rogers

Yes, so the correct answer is "it all depends".....

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

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