Handcut Thru Tenons - Help

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Forum topic by Eric posted 10-16-2010 11:47 PM 1806 views 0 times favorited 19 replies Add to Favorites Watch
View Eric's profile


43 posts in 4022 days

10-16-2010 11:47 PM

Topic tags/keywords: question

I am making a ladder for a loft bed. The rungs of the ladder are going to be wedged thru tenons. I cut the tenons first then used each tenon as a guide to lay out the mortis. The side where I made the lines for the mortise came out pretty good but the outside of the ladder kind of got blown out. Is there a better way of doing this using hand tools? I do not own a tablesaw or a router.

-- Eric

19 replies so far

View richgreer's profile


4541 posts in 3312 days

#1 posted 10-16-2010 11:56 PM

I’m a power tool user so I don’t have directly applicable experience. Nonetheless, I always cut my mortised first and, if you do that, you should be able to accurately mark both sides. Then you cut from both sides and meet in the middle.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View Sarit's profile


550 posts in 3377 days

#2 posted 10-17-2010 12:44 AM

I don’t know how to do it with hand tools either, but perhaps you can clamp a scrap board to the outside and cut through both so that the edge of your cut is still supported by the scrap piece.

View interpim's profile


1170 posts in 3696 days

#3 posted 10-17-2010 01:03 AM

I’ve never had good luck cutting mortises in pine either… same problem happens to me.

-- San Diego, CA

View Eric's profile


43 posts in 4022 days

#4 posted 10-17-2010 01:05 AM

I did put a scrap piece of wood underneath to support the edge but it still “chunked out”. This is pine by the way and I don’t know if this is happening because of the soft wood.

-- Eric

View Sarit's profile


550 posts in 3377 days

#5 posted 10-17-2010 01:11 AM

Maybe its better to cut from the opposite direction since the shoulder of your tenon will cover any blowout.

View shipwright's profile


8187 posts in 3035 days

#6 posted 10-17-2010 01:50 AM

If you through drill first with an undersized forstner or even a speedbore with a backup piece clamped behind your work, you could then finish from both sides to the middle with a chisel. The drilled holes would allow you to pare a little at a time and would allow you to accurately mark the back side.

Paul M

-- Paul M ..............the early bird may get the worm but it’s the second mouse that gets the cheese!

View JJohnston's profile


1622 posts in 3528 days

#7 posted 10-17-2010 01:54 AM

I’ve never done these, but guru Roy Underhill would cut from both sides and meet in the middle. Seems like that would make sense.

To fix it, how about putting a chamfer along the edge of the mortise? If you can’t hide it, emphasize it!

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln

View Eric's profile


43 posts in 4022 days

#8 posted 10-17-2010 02:38 AM

Chamfered mortise? Very interesting. Thanks!

-- Eric

View swirt's profile


3555 posts in 3209 days

#9 posted 10-17-2010 06:16 AM

Knife cutting both sides would help. It kind of limits the blowout. Not always possible if you can’t get the location defined on both sides.

If you can’t work from both sides, as others suggested, working from the outside (visible) to the inside (hidden) would probably be the best option like sarit suggested.

-- Galootish log blog,

View KayBee's profile


1083 posts in 3483 days

#10 posted 10-17-2010 07:05 AM

Like shipwright said. Drill out as much waste as you can. Mark both sides, chop in from both sides.

-- Karen - a little bit of stupid goes a long way

View Eric's profile


43 posts in 4022 days

#11 posted 10-18-2010 01:07 AM

Thanks for all of the tips. I will try them on the other side of ladder.

-- Eric

View rance's profile


4267 posts in 3398 days

#12 posted 10-18-2010 01:26 AM

What Sarit, JJohnson, and Swirt said. I would cut the mortises first, then do the tennons to match. One bunged up mortise could be fixed by enlarged ever so slightly without noticing. Oh, and one more thing, the one with the blowouts goes against the wall. Ha ha ha. REALLY! What do you think penturners use the clips for? Its not about doing a perfect job, its about how good you are at hiding the mistakes. :D

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Gregn's profile


1642 posts in 3221 days

#13 posted 10-18-2010 04:52 PM

Try putting masking tape where your cut lines will be and then draw your cut lines on the tape and score your cut lines with a sharp utility knife. This will help to prevent blow out by the tape keeping the fibers more in place during the cut. Also ease into the final end cut to avoid excess pressure, also be sure your chisel is sharp to help prevent tearing of the fibers. Pine fibers tend to tear quicker and crush with a dull tool. Hope this helps.

-- I don't make mistakes, I have great learning lessons, Greg

View TheDane's profile


5575 posts in 3900 days

#14 posted 10-18-2010 07:30 PM

When you cut your mortises, did you clamp a backer board to them? I usually lay a scrap on the drill press table with the workpiece on top of it, then clamp both. I drill a slightly undersized hole all of the way thru with a Forstner bit, then chisel from both sides.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View RonTanc's profile


23 posts in 3015 days

#15 posted 10-19-2010 07:16 PM

Lay out your morrtises, then drill through at each corner with a forstner bit using a backer board to eliminate tearout. Draw outside tangent lines to your four holes on the opposite side. Run a sharp utility knife on the pencil line using a straight edge to establish the cutting edge. Using a chisel, hand push into the knife line (no mallet) and begin to pare away the waste.

You’ll end up with a clean crisp shoulder. With the mallet, pare away from each side towards the center of the board. Once you have a good shoulder established, tilt the chisel a degrees or so toward the openning to establish a clearance for the tennon.

-- Cut the hole twice and it's still too big!

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