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Help for a beginner

Started by Jim_Rogers, January 12, 2016, 09:27:12 PM

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Jim_Rogers

A beginner timber framer has send me a list of questions and he felt that my answers may help others, here.

This is his story:

QuoteThe frame plan I purchased was a 12x16, 10' wall with 12/12 common rafter. I am actually only going to 12x12, 9' wall (gets me to 15' overall height, which is the county guidelines) and using 6x6 instead of 8x8. 3x5 braces vs. 4x6

I am using doug fir species for my frame. It is supposed to be full dimension rough sawn, SFA, FOHC. when i picked it up, the actual size of the timber was 5 3/4"

Bought the timbers through Capital Lumber in Phoenix. My wholesaler says I should expect 5 7/8" typically, but since i got 5 3/4", the timber must be quite dry.

When reading a plan, laying out and cutting the joints, how do you account for undersized timbers with respect to tenon/mortise size, housing and reduction?

Answer:
If you are establishing some "general frame rules" then the rule would be 1/2" under the size you ordered.
If you ordered 6x6 then your housings are going to be laid out 5 1/2" off the layout side/arris. That means if your timbers are 5 3/4" then they will only have a 1/4" housing. This shouldn't be a problem unless the tie beam needs some support for any loft load.
Quote
Why size down the tenon width/mortise length to the nearest 1/2"? Is this for exposing the 'inner timber'?

Yes, and to standardize the size of the joints that will mate.
Quote
If I am working with 6x6 timbers which are actually 5 3/4", and I size tenons to nearest 1/2", is my reduction 1/4"

Yes.

Quote
If my plan call for a 5 1/2" tenon. Should I cut the 5 1/2" tenon/mortise and use a 1/4" reduction and 1/2" housing, or cut a 5 1/4" tenon/mortise with 1/2" reduction/housing or a 5" tenon/mortise with a 3/4" reduction and 1/2" housing?

Cut a 5 1/2" long tenon and create the housing at 5 1/2" from the layout side/arris, thereby making a 1/4" deep housing.
Quote
Why does the reduction it extend 1 1/2" beyond the tenon and have a 45 deg. chamfer? Is this aesthetic or does it server another purpose?

It extends beyond the tenon 1 1/2" so that there is no chance of a fat timber interfering with the other timber.
The 45° chamfer is mostly for decoration but it also reduces the risk of the timber splitting at a 90° corner.

Quote
As a general rule, I understand that the tenon thickness should be 1/4 width of the timber, so that is 1.4375 (5.75 x .25). Can I assume I should round to 1 1/2"?
Yes, use 1 1/2" for the tenon thickness, 1/4 the requested size, not 1/4 the delivered size. Keep your dimensions standard to your layout tools, like the framing square.

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If the peg is to be 1/2 the thickness of the tenon, I should be using 3/4" pegs?

Yes, 3/4" diameter pegs for 1 1/2" thick tenons.

Jim Rogers
PS. I hope you find these questions and answers helpful.

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

Brad_bb

Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

dad2nine

You are so right... That was very informative :thumbs_up

fishfighter

Thanks for posting that Jim. I kind of figured those questions out myself. ;D But then again, I have many years of boat building experience along with woodworking behind me. ;D

terrifictimbersllc

Jim could you define "reduction", found all the other terms in the TF glossary but not this one. thanks.
DJ Hoover, Terrific Timbers LLC,  Mystic CT Woodmizer Million Board Foot Club member. 2019 LT70 Super Wide 55 Yanmar,  LogRite fetching arch, WM BMS250 sharpener/BMT250 setter.  2001 F350 7.3L PSD 6 spd manual ZF 4x4 Crew Cab Long Bed

Jim_Rogers

The "reduction" is the end of the timber that is reduced to a smaller size so that the timber is a standard dimension other than the rough sawn size.



 

In the above drawing the area of the post where the dimension "C" is labeled is the reduction of the post to the smaller inner timber. This 6x6 has been reduced down to a 5 1/2" size post at the end.

The beam above it has also been reduced down from a 6x6 down to 5 1/2" at the joint to the smaller prefect timber inside. This reduction or it is also called a housing on this timber has been made to 5 1/2" from the end of the timber.

Here is a shot of a tenon with the interior side of the post up showing the reduction:



 

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

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