I made some double tenon joint shelving brackets like this and I made an extra one so I could test
it to failure which is what I want to do in this video but I thought I'd also compare it to just
using screws because that's what John Heise likes to do for shelf rackets so I made this one and is
joined with two screws at the top and there's even washers behind the screw heads because screw heads
pulling through is a major source of failure and with these really long screws these might hold
quite well I wouldn't be surprised if two held up as well as these ones and I need to clamp
these shelf brackets so something are there and I figure this column here is actually the best place
to clamp them to it I just have to move that workbench out of the way that should hold Bo
enough and I put plywood behind it to make for a better youtube thumbnail well that was to be
expected I don't want to add any more weight but I figure I'll just extend it to add more leverage
alright I think I just lost a little bit of nerve there
okay let's see how far I'll get before it breaks
Oh balance right here but it's about to go a little bit further balance my foot was right
about here 90 centimeters from the shelf bracket and it broke tenants pulling out I thought it
might be that the wood would rip but it's the tenants that pulled out let's try the screwed
version so I was pretty confident and hold this bar no problem no problem no problem so bad
and screws feel much more gradually this is pretty good so that was right here that's 75 centimeters
from the bracket so let's have a look at how these failed tendon pulling out there okay so what does
some extent that would did break on the bottom part and oh I had really crooked grain on here
we should probably made this one fail earlier than it could have failed yeah that's an unfortunate
choice there of a piece of wood there too crooked a bunch of grain in the Tenon's and two by fours
like that they vary quite a lot in density so I suspect with more dense 2x4 with straight grain
this could have easily been one and a half times stronger than it was and this is the screwed one
which the failure of this one was about 80% the strength of this one so this is actually a pretty
good method of joining these certainly with the screws in here this would have easily held my
weight right there because I was able to go quite a bit beyond there so for the shelves I made just
two big four inch screws would be quite adequate and the way it failed is these screws that start
to pull in here even though I put a washer behind the head so that's a very important aspect there
is to put a washer behind the head maybe an even bigger washer and look at that the wood broke
right there so that started to break the wood and the way I put the screws in is actually not
even in the optimal position because the way to angle them down they should have really come up
a little bit further up there so this could also be easily 20 percent stronger yeah so part of
it is that would just sort of split open this is probably not an ideal piece of wood either
but putting that together was pretty hard no less work than this version except I didn't have to do
very much setup and I actually kind of stripped the screw heads on here when I screwed these in
because it was so much torque on them and I'm kind of curious how well would pocket holes
do for this so I'm just reusing the same piece of wood that I had for my double tenon to make
a pocket hole drink that screwdriver starting camo'd on me and since I'm already using pocket
holes I might as well use that they Walt impact driver the impact driver is good that way because
it hammers the bit back into the screw as it goes I thought using pocket holes would be easier than
that damn it I just screw it to my table saw I'm gonna back up the screws a little bit cuz
I go and I watch the hole in there I hate pocket holes and now the pocket hole test yes I wanted
it to break because I wanted to see how strong it is so the failure mode of this one was not
the pocket holes failing but the actual screws pulling out of the wood yeah that just pulled
this right out of there and what did this one in is that the pocket hole screws that I put in
there just ended up too close together because they're at an angle so they're only grabbing a
small wedge of wood and that wedge just pulled out I guess if I could put these in at a angle
more like this but that'll be quite a challenge because then I need a different kind of jig and
an even longer drill I also put the jig back here a little bit like that so that it have more wood
for those to grab around but of course that meant that the screws ended up being maybe a millimeter
closer together than they needed to be so if I set the jig here instead of here that would have
helped us pranked a bit so that was actually kind of impressive showing for the pocket holes it was
more than half the strength of the double mortise and tenon and it would have been strong enough for
the shelves to climb on like I did to demonstrate them but I still don't like pocket holes