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Pegs per tenon

Started by sailorman, December 01, 2011, 08:35:29 AM

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sailorman

Hello all, first post, but I think I have read every post in the TF section prior to starting a small tf wood shed earlier this summer. Dimensions are  8' x 16', The frame members are 6x6 EWP, with 4x6 braces.(hopefully the sketch is attached) No previous training or experince in TF but have lots of building experience in  residential housing, furniture and cabinet making. The frame has been dry fit  (peg holes not bored yet) and I am now ready to assemble and raise the frame but have a question on the number and layout for the pegs in the M/T joints.  Should I place one peg per M/T joint or two? M/T dimensions are 1.5"x 6",  timbers sized to 5.5". All tenons are through tenons, placed at 1.5" from reference face. I understand the layout for the brace pegs, but the layout for the M/T joints has wondering what the best layout would be? Are two pegs best for joint strengh or would two pegs actually weaken the joints due to the removal of stock? What would the correct layout be for the Pegs if 1, or if 2? Could I just use 1.5" from shoulder and 1.5" from reference face?  Should I  use two for the grits to posts and one for the top plate to posts? After having cut the frame and dry assembled I realize that I made several mistakes in the cutting of the frame, with the biggest being the the mixing of 6" wide M/T with housing at 5.5", kind of screwed the brace locations up. Oh well thats why I started with a wood shed! Thanks

Jim_Rogers

sailorman:
You need to create an album and place your pictures there. Then you can post a link to the picture in your thread.
Read up on the instruction of how to post a picture.
My computer can't open the file you attached. I don't know what program I should use.

As far as pegs go they are one per brace tenon. The layout is 1 1/2" off the shoulder of the housing and 2" off the bearing end. See my brace drawing and layout stories. Search here for them.

Next, your tie beam through tenons should be also 1 1/2" off the shoulder and 2" up from the bottom.

Peg are not laid out from the reference face. They are laid out from the housing in the post, which of course is laid out from the reference edge. But my point is that the peg can't be too close to the end of the tenon.

Your pegs should be 3/4" in diameter.

I don't have time right now to post some drawings or pictures. But I will.

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

dukndog

Welcome to the FF Sailorman!!

I've opened your file and the plan looks good. I'm still new as well, but Jim and some of the others should be able to help you soon.

Jim, his file opens with Sketchup, if that helps.

Thanks,
DnD
WM LT-15G25 w/PwrFeed, Mahindra 3510, Husky 385xp, Stihl MS261 and a wife who supports my hobby!!

jander3


sailorman

Jim, As dukndog points out it is a sketch up drawing, i will post in gallery once i fugure out how to save skp. file as a jpeg and post in gallery, i am not so good with the file convesrion stuff. I will read through the gallery instuction.
Yes pegs are 3/4 inch, red oak. I did read the brace layout posts previously and it was a big help. Actually by reading all the post here, is how I learned how to do this shed build. Your instuctions on layouts, cutting and over all information was of the greatest help. The brief discription of M/T peg layout helps also,  now just wonering if I need two pegs? I am inclined to think that one per joint would be sufficent for a small strucure like this. Thanks

canopy

In a properly designed TF, pegs are not used to provide structural strength. They just keep things from moving around. For 6" or smaller tenon use 1 peg, 2 pegs for 7-10".

shinnlinger

I will also suggest that two pegs is superfluous and perhaps even weaken the frame if not just waste materials and double the chances of a blowout and splitting.  I have never seen two pegs used in a basic mortice and tendon joint
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

piller

Have you seen the Historic American Timber Joinery series, it's a free download from the timber framers guild site, you want to look at the first one, Tying Joints, Tie Below Plate, here:
http://www.tfguild.org/joinery/part1.pdf

See figure 5, it says that members 6 inches deep or less usually have one peg, members 7 - 10 inches deep usually have two pegs.  Your post is a 6x6 which is reduced to 5.5" so I think you would want one peg.  Jim suggested a peg layout 1.5" from shoulder and 2" from bottom and that might be best.

Your roof design will create some outward thrust on the plates (but not a whole lot because your frame is 8 feet wide and your bents are 8 feet apart) which must be resisted by the tie beam to post joint, it will be a tension joint and is probably the most important joint in your frame.   I'm not positive on this, perhaps others will comment, but I think that the roof overhang probably helps to reduce the outward thrust.  I think with the single peg layout as Jim suggested you are good to go.

By the way,  nice looking sketchup model!  I really need to learn how to do that. 

Jim_Rogers

I did manage to get the sketchup file open, and review the frame design.

For the through tenon on the tie to post as mentioned it is the join that is in tension. But as it is a narrow frame you should be ok with one peg.

Also, I didn't see a tying joist in the sills assembly. There was a youtube video about a guy who wanted to build a cabin "off the grid" and he cut the frame as you have, without a tying joist, back in his garage before he moved it to his hilltop location. While it was there and drying out, it started moving and the sills spread apart, in a short time. He had to drill and install lag bolts into the end grain of his floor joists as measure to stop it from spreading any more.
This can happen and that's is why we use a tying joist. To hold the sills together in the middle from end to end.
If your joist pockets are already cut then you may need to secure the middle ones with lag screws or bolts once you get them frame assembled and square.

Good luck with your project.

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

sailorman

Thanks all for the reply's. So 1 peg is the right way to go, which I kind of assumed was the best way but wanted to check. Thanks for the TF guild document, i have not read that before, but will do so. Regarding the roof, rafter over hang will be supported by three posts and a beam. This will provide a covered area on the back side of the shed for part of dog kennel to be under and provide a little covered storgae area. I have considered adding  short post to  each tie beam to support a ridge beam with rafters, in the thinking that it would reduce the outward thrust of the low pitch roof. We do get a fair amout of snow here. Metal roof pannels will be used to help shed the snow. (no pun intended)  I should be assembling the floor and the bents this weekend and raise  next weekend.
Jim, Orginally I was going to put a tie joist in the floor frame but i figured that at 8Ft wide it should be fairly stable. A timber lock screw will be placed at each intersection of floor joist to sill.  Sill to Floor joist is a double step joint. As a further strengthing means the 2 x 6 floor boards will span the joint as well. Or maybe I will run them at a 45 degree angle to the sill to tie the joist to sill together.
Thanks for the info.

Jim_Rogers

If you add a ridge beam and a post to support it then you are changing the load(s) on the tie beam.

It will reduce the thrust at the plate, but now your tie beam maybe too small. I can't really say without "running the numbers".

Another time if you were to do something similar, I wouldn't cut the birds mouth in long rafter that deep. They should be less then 1/4 the vertical height of the rafter at the point of the birds mouth. But you should have at lease 2" or more of bearing on the plate.

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

sailorman

The rafters have not been cut yet so I will keep your advice in mind when cutting the birds month. At this point  I am under the gun to get the frame up and out of the garage! My wife is getting tried of scrapping frost from the car windows in the am and if it snows....oh boy! Now I dont mind the frame parts being in the garage since my car still can fit! HAHA The next frame for a wood shop will be better planned and engineered!

Piston

Sailorman,
Welcome to the forum.  In order to save pictures of your sketchup drawing, go to File, then Export 2d Drawing and save it to your desktop (or wherever you want to save it).  You can then upload it to your gallery and include it in your post. 

I believe the photo upload tool is still being updated at this time so it might be a little while before we can upload photos, but that is how I've done it in the past. 
-Matt
"What the Lion is to the Cat the Mastiff is to the Dog, the noblest of the family; he stands alone, and all others sink before him. His courage does not exceed his temper and generosity, and in attachment he equals the kindest of his race."

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