Round tenon on 2x4 fence rail - without turning

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Forum topic by JCantin posted 10-01-2014 12:15 PM 2151 views 0 times favorited 9 replies Add to Favorites Watch
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162 posts in 2834 days

10-01-2014 12:15 PM

I’m replacing the rails and pickets on a cedar fence – but keeping the original posts in place. The rails are dimensional 2×4 with round tenons that go into the posts. I’ve seen the jig used to do this on square stock but am wondering how I might do this on rectangular stock.

9 replies so far

View Rayne's profile


470 posts in 961 days

#1 posted 10-01-2014 12:30 PM

Given what I have in my shop (which is limited), I’d use a multi-function tool to cut away the edges little by little to get a round tenon generally shaped and use sanding blocks or just sandpaper to round it over completely.

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162 posts in 2834 days

#2 posted 10-01-2014 01:23 PM

I wonder about squaring up the 2×4s using 1x stock pinned or double-sided to the 4” sides, then using a jig like this one?

View BinghamtonEd's profile


2263 posts in 1791 days

#3 posted 10-01-2014 02:02 PM

You could add the stock, or if you have a lot to do, I would make a jig that has a circle with a slot sized to the 2×4 cut in the exact center. Make the jig so the circle piece drops in (in the link, theirs has a rectangular guide that drops in). Slip the end of the 2×4 into the circle plate, then when the circle turns in the jig, the tenon will be centered.

I’m not explaining this well…in their picture, the jig insert stays stationary and the stock turns. In my idea, the insert turns with the 2×4 fixed inside it.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View mpounders's profile


821 posts in 2317 days

#4 posted 10-01-2014 02:14 PM

Easy way might just be to drill a hole and use a dowel?

-- Mike P., Arkansas,

View Emaxx3's profile


2 posts in 2588 days

#5 posted 10-01-2014 03:40 PM

Easy way might just be to drill a hole and use a dowel?

- mpounders


View gtbuzz's profile


427 posts in 1863 days

#6 posted 10-01-2014 03:41 PM

What about using a hole saw? Figure with a 2×4, it’s a 1.5” dia tenon, right? You’re not drilling through the piece, so the part that normally gets discarded will remain as the tenon. You’d have to manually get rid of the surrounding wood, but you could use a jigsaw to get up to the tenon and then just chisel away the rest. Might be easier to cut away 1” on each side of what would be the tenon, so you’re left with a 1.5” square tenon. After using the hole saw, you’re left with not much to chisel away.

Since it’s for a fence, doesn’t have to be perfect and seems to me an approach like this would be quicker than building a custom jig (that is unless you’ve got hundreds of these things to do)

Out of curiosity, how do you plan on getting the tenons in the mortise if you’re keeping the original posts? When I built my fence, I mortised the posts to accept the rail itself as a tenon. Recently, one of the rails was damaged so I had to notch out the original post, extract the damaged rail, put in a new one, and fill the notch I put in the post.

View hairy's profile


2377 posts in 2954 days

#7 posted 10-01-2014 04:02 PM

This old tenon cutter was $5 at the flea market, look around , they are out there.

New ones cost dearly.

How many and how big? You could rough shape it with a hand saw, then use a sharp chisel.

-- stay thirsty my friends...

View bondogaposis's profile


3969 posts in 1773 days

#8 posted 10-01-2014 07:27 PM

First make a square tenon on the end of the 2×4 then use the jig you posted.

-- Bondo Gaposis

View runswithscissors's profile


2127 posts in 1447 days

#9 posted 10-02-2014 10:51 PM

Another way would be to chop the mortices out to square or rectangular, and use square or rectangular tenons, which would likely be stronger than round ones.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

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