Drawbore Pin Broke

[Jak3]

Was just about to glue up a draw bore mortise and tenon for a small table project when I had everything ready with glue applied and as I was driving in the pin, it fractured and broke sharply in the middle of the joint. My heart literally sank... I had to frantically try and drive it out with another part of the dowel, and it broke too, so I had to use a screw driver to remove the broken dowel. (the dowel did not break because I glanced it in the hammer, it broke in the middle partway down the shaft of the dowel.) I was very stressed and have never seen this happen before. Almost ruined the joint.

Did my Lowe's white oak dowel have junky grain or was my drawbore too tight? I did not measure 1/32 to offset the hole I just took my awl and move the hole a tiny bit by eye but not 1/16th toward the shoulder... So I don't think I over did it.

Maybe I shouldn't buy dowels from Lowe's...?

 

[Chris C]

I always make my own pins from dry white oak. I split (rive) it from a blank and then shape it. That way I know I have strong pins with straight grain.

That being said... .. sometimes they break. When that happens I drive another pin through. That usually works.

I use glue solely to lubricate the pin.... It seems to help.

 

[TENdriver]

I think if you look into why we split out our own riven pins, you’ll also see why we virtually never would use home center dowels. Dowels are probably okay for cosmetic pinning but not drawbore.

Have you watched any of the material by Peter Follansbee? He has some great insights into 17th century workmanship and how they did drawbore pinning.

It may also be helpful to do a post-mortem on you pin break.

Were there any other factors?

Did you taper your pin?

Was there grain runout or just a weak piece of wood?


EDIT: so this is about green joinery, but there is a useful discussion on draw bore.

The Woodwright's Shop | Paneled Chest with Peter Follansbee | Season 33 | Episode 9 | PBS

How to fiHow to fit the beveled panels and storage till into a chest from the Pilgrim era.

www.pbs.org

The Woodwright's Shop | Elizabethan Joint Stool with Peter Follansbee | Season 31 | Episode 7 | PBS

The master joiner of Plimoth Plantation shows us...

www.pbs.org

 

[Graywolf]

Another yes you should split out your draw bore pins, White Oak is a great choice for its strength and resilience. That being said I have used other woods with success.

 

[Chris C]

Did your pin make it through the tenon? If you drove it completely through before it broke then you're probably ok. It doesn't have to be one solid pin through the entire bore to hold the joint tight. I always check the joint to see if it's solid.

Just cut two plugs to fill the holes on either side and nobody will ever know.

 

[Jak3]

I whittled the end to help it through. It broke directly in the center, and didn't make it all the way through.

In fact now that you mention making your own pins, I might try and do that.

I have some straight grain stock, what grain orientation is best for a pin, quarter sawn or rift sawn or flat sawn? I could just rip down some quarter inch strips on the table saw and use a block plane to make my own octagonal pins. It wouldn't be unwelcome in the overall look of the project.

 

[Jak3]

Is there a reason you all specifically said you split (Rive) your own pins rather than ripping them down on a table saw?

Does splitting them remove stress from the wood or something?

 

[Jak3]

Thanks for all your insight. I need to get out in the shop and fix this. I had all my parts sanded and ready for finish until this glue up fiasco happened.

 

[TENdriver]

Did you get a chance to watch the first video? There is some discussion of riven pins at the beginning of it.

That’s a 3/4” dowel that was sawn and not riven. Sawn stock usually has some degree of grain runout. In this case, the dowel fractured along the grain.

In riven stock, the grain will mostly run from end to end. You get the strength across the entire dowel. Riven is the strongest way to make a pin.




BTW, what type of table are you making? Is it a small side table or a large “harvest” style dining table?

Strictly speaking, a smaller table may not require any pins.



This table has been in use in a family room for over three years.

It’s just a dry fit without any glue or pins. Just plain old mortise and tenons.

In fact, if you zoom in and look closely, you can see the tenons aren’t even fully seated to the shoulder.

 

[JohnnyR]

Splitting them insures straight grain along the length. Rip only if truly straight. Can also make a round dowel with four passes with a round over bit.

 

[Jak3]

I see. My dowel broke exactly like that. Diagonally just like that picture.

 

[Jak3]

I am making this table. I have glued the arched rails to the supports underneath the table top. Last night I was going to glue the small roped cross members to the legs, then attach them to the long rails. The finish will be arm r seal satin.

Now that I am in the shop by the heater I will take the time to watch those videos before I split my own pins.

 

[Jak3]

This was everything before being sanded or glued

 

[marinosr]

I would like to pipe up for the "You don't have to rive your own pins" minority! I have had just fine luck with Home Despot dowels... just dump the bin out on the floor and pick the ones with the straightest grain... five minutes of fishing will find you plenty of good dowels. If there's a small wonky section on one, just cut around it when making the drawbore pins. Sharpen the ends with a pencil sharpener so they can easily find their way through the drawbore, and use plenty of bar soap or wax on them so they drive smooth. Easy peasy, you'll have no split pins.

Of course, riven pins are best, but totally not a necessity IMO.

 

[TENdriver]

The photo helps. I see the bridle joints. They will benefit from a mechanical fastener. In your case the pins.


BTW, Marinosr is absolutely correct that the pins don’t have to be riven if you “carefully” select for straight grain from end to end. If you understand how and why, then it will work fine. But you weren’t familiar, so explaining riven stock made more sense to me.

My home center sell dowels made from Chinese mystery wood. Not oak. I have some bone dry white oak for pin stock. I don’t use that much so I stick with the oak.


EDIT: I posted too quickly and forgot to say nice looking table!

 

[Jak3]

Thanks y'all for for all the help. I had thought I chose a decent dowel from lowes... I thought I chose a white oak one from mostly red oak. I gonna try and split my own I think. But I'm having mixed results with my hatchet.. I may or may not go pick through some more dowels.

 

[Jak3]

I've just tried to split some pieces... I reckon they don't have to be perfect ...?

 

[Chris C]

I think your picture shows exactly what we're trying to describe. The grain "runs" off to one side resulting in a taper. But what's left in those pieces is straight grained. Just start with split pieces a little bigger than you need and whittle them down to rough size.

After that I drive them through a piece of steel into which I drilled several different sized holes. That produces a roundish pin that's ready to go.

I think Lee Valley and LN both sell plates for this purpose but easy to make your own.

 

[Jak3]

Heres what I've got so far....

I think after this project I will invest in a dowel plate like you reccomend.

 

[Chris C]

Your pin should look like a pencil. If you're trying to drive a wedged /tapered shaped pin into a drawbore you're asking for trouble.