6 November 2014 at 12:05 am #120610Matt McGraneParticipant
OK, so this might go better in the “Cutting Board” project forum, but nobody seems to be going there anymore …
I’ve just finished the cutting board project and am very happy with it. But each of my tenons split when I drove in the draw-bore pins (see the close-up picture). I offset the 3/8″ diameter holes approx 1/16″. The wood is maple (fairly hard wood). The tenons are approx 3/8″ thick. The pins were right at 3/8″, maybe 1/128″ oversize in spots, so I don’t think oversize pins was the issue. I took great care to bore the holes square to the surface and I think the holes in the tenons are properly in line vertically relative to the holes in the end boards. There is a little slop in each mortise hole.
Can anyone comment on why the tenons might have split? The joints are very tight, so the split tenons seem not to be a functional issue. Thanks in advance for any comments or advice.
Matt, Northern California - Started a blog in 2016: http://tinyshopww.blogspot.com/
You must be logged in to access attached files.6 November 2014 at 1:07 am #120621BrianJParticipant
First off its a great looking cutting board. Well done!
I might first suspect since it occured on each of the 4 tenons, did you taper the leading edge before driving them through? If so perhaps by not enough?
Ontario, Canada6 November 2014 at 1:40 am #120627
Maybe the tenons split during the bore this happened to me once before other than that what Brian suggested to taper the ends of the pins. I like to cover the pins with glue to provide lubrication but if you wait to long they set and cause friction. Other than that I really dont know what else caused it.
The Lost Scrolls of HANDWORK
(Hand tool only woodworking magazine)6 November 2014 at 2:11 am #120628Jim AllenParticipant
This is a nice cutting board. You did neat work! I’ve had the same problem a few years ago but not on a cutting board. What caused my problem was too much wedging across the grain. The wood can stand a lot of pressure/ wedging with the grain but not crossways. The draw-bore acts like a glut (wooden wedge) if too tight across the grain. I make my draw-bore pins sort of oval shaped so that they just fill the hole across the grain but do the tighten-up with the grain. I hope this helps.
Jim from the mythical State of Jefferson – Oregon side6 November 2014 at 2:12 am #120629Greg MerrittParticipant
Nice looking cutting board. Sorry your tenons split. The split won’t be a functional issue however.
Drawboring can be a bit tricky. A few things that I found help are as follows.
1. Make the tenon tight across the width. The less room there is for the tenon to spread, the less chance of a split.
2. Make the pin ever so slightly oval shaped. Drive the pin in with the narrower sides facing the long grain.
3. Alternative to #2 is to make the hole in the tenon oval shaped to lessen the pressure across the grain.
4. Make the pin long and taper generously.
5. Slow and steady as you drive the pin in. Slower allows the pieces to compress and adjust for the pressure that the pin is exerting.
Hope that you might find some of that useful.
http://hillbillydaiku.com6 November 2014 at 2:35 am #120630Matt McGraneParticipant
Thanks for the input, guys.
Brian, I did put a taper on the pin, starting about 1/2″ up the pin with final diameter at the end of less than 1/4″. Maybe I need a longer taper.
Salko, that’s a great point about possibly splitting the tenons while boring the hole (not while driving the pins). I don’t remember hearing anything and I didn’t look specifically, but you never know.
Jim and Greg, that’s interesting about the oval shaped pins. I can see driving the 3/8″ thick tenon apart with the peg acting as a wedge. I’ll have to try the oval shape next time. And I may have driven the pins in too aggressively, too.
Excellent lessons learned. Thanks.
Matt, Northern California - Started a blog in 2016: http://tinyshopww.blogspot.com/6 November 2014 at 2:55 am #120631
I believe in this case that Greg is more spot on than the rest of us, had you split the tenon whilst boring you would of heard and seen it as I did mine it’s a prominant sound wood splitting and a visual OMG why oh Lord I was doing so well, all that planing and sweat poured into this type effect, horror, heartbreak.
The Lost Scrolls of HANDWORK
(Hand tool only woodworking magazine)6 November 2014 at 3:10 am #120632Greg MerrittParticipant
I would like to add that all of the suggestions that I offer above were learned the hard way. I’ve split my fair share of tenons with drawboring. Mostly in practice pieces though. Just make up a bunch of practice pieces and try several different options. It’s great practice for mortise and tenons at any rate. 🙂
http://hillbillydaiku.com6 November 2014 at 3:16 am #120633Dave RiendeauParticipant
Does the species of wood factor into this? Maple being extremely hard and dense?
-Canada6 November 2014 at 3:38 am #120636
I support Greg’s theory because when you look at a cut nail it’s wider in width not round very much representing the oval theory of what our learned friend Greg suggested.
When you drive a cut nail into timber you turn the nail so the widest part of the nail is going along the grain. If you turned the nail so it’s widest part go across the grain you will without a doubt split the wood.
Now Shanon Rodgers suggests you make a pilot hole to avoid but this is not necessary if you follow this simply procedure I outlined. So Greg’s theory makes sense to me.
The Lost Scrolls of HANDWORK
(Hand tool only woodworking magazine)
- You must be logged in to reply to this topic.