Making one long board from two shorter ones...

[Brian Eaton]

I am making a sharpening station out of the scrap Doug fir 2x4s from my old workbench. Let’s say I need a 22” long 2x4 but only have 17” scraps left. Is there a structurally sound way to join two pieces end to end to make one longer board? I’m thinking just a half lap joint glued up really well? It wouldn’t be load bearing but would be providing stability to the frame of the table.


Thoughts?

[Jim Koepke]

The joint you are asking about is called a scarf joint.

Dr. Google will give more ways than you will want to know on the various ways to make this joint.

jtk

[Pat Barry]

I'd go half lap or bridle joint depending on how ambitious you are feeling. I'd make the overlap length longer than shorter, about 4 inches for best strength.

[David Myers]

I'd vote for bridle, and consider pinning it if it is going to be a stretcher.

[steven c newman]

There is a glue joint, machine-made, used all the time. Companies will cut all the knots and other defects out. Then a cutter head cuts a "finger joint" on the ends of the good parts. Then those are glued up to make as long of a clear stick of lumber as needed.....

[glenn bradley]

Wood Mag Issue 207 had an article on this.

388821

If I wanted max strength I would do a bridle. A half lap is almost as good but, consider the purpose of the board. Something simple may be your "right" answer.

[Bob Glenn]

Make a trip to your local lumber yard.........two by fours are cheap.

[Simon MacGowen]

Make a trip to your local lumber yard.........two by fours are cheap.

This is the best advice, unless the OP is looking for an opportunity to practice his joinery skill.

Simon

[Brian Eaton]

I know 2x4s are cheap, but why not try to use some of the scrap AND get some practice at joinery? I will give half laps a try.

[Mike Henderson]

I've used dovetails to join two boards end-to-end. In this case, both boards use tails - no pins. I'll try to post a picture later. It's pretty easy to do.

This is a sample board that I show to my students.

388861

Mike

[steven c newman]

Some places sell a router bit, some a shaper cutter..
388862388863
When I had to trim the screen door to size..this showed up.

[Patrick Walsh]

I have yet to dear but it’s on my short list...

You know with all my free time.’

I’d go buy another couple 2x4...

https://m.youtube.com/watch?v=Ru1KSv3pw4s

[Simon MacGowen]

I have yet to dear but it’s on my short list...

You know with all my free time.’

I’d go buy another couple 2x4...

https://m.youtube.com/watch?v=Ru1KSv3pw4s

Nice showoff.

Simon

[Matt Lau]

Or here's a big version:
https://youtu.be/QPUPyuz_ink

I think that Stan Covington would be the best guy to ask if you go the Japanese route.

[Simon MacGowen]

I think that Stan Covington would be the best guy to ask if you go the Japanese route.

There was a member very good with Japanese woodworking got banned. The thread was removed. Is this Stan the banned member or a different person?

Simon

[Jim Koepke]

There was a member very good with Japanese woodworking got banned. The thread was removed. Is this Stan the banned member or a different person?

Simon

Was he banned? My understanding was he left after a post of his was edited in a way that he felt was unwarranted?

jtk

[Simon MacGowen]

Was he banned? My understanding was he left after a post of his was edited in a way that he felt was unwarranted?

jtk

If he indeed is the same person (no way for me to check as the thread was gone), I don't think he can take part in this forum anymore. Someone may be to confirm this. At least, I have not seen anything from him since.

Simon

[James Waldron]

I have Stan Covington's e-mail address. If anyone wants to reach him, you can PM me and I'll ask if he's willing to permit me to share it. He is indeed quite knowledgeable about Japanese tools, tool makers and joinery techniques.

Back to the lengthwise joinery: as a boat builder, I have made many a scarf joint. Unlike scarfs illustrated in FWW, cited above showing a 45 degree 1:1 joint, boat builders typically use a 12:1 joint when planking a hull, i.e., one where the taper of the board is stretched out 12 inches long for every inch of thickness. When properly made and glued, 12:1 scarf joints have survived as long as a century on planks of old boats and ships. To the best of my understanding, the reason a scarf is used rather than a lap or bridle joint is because the scarf permits the plank to be bent to shape without forming a localized "hard spot" that deforms the shape of the plank. And it's long enough that the joint is substantially long grain to long grain; a 1:1 scarf is pretty much end grain to end grain.

Experience has shown that a 12:1 scarf, properly made, is very little different in performance to running down to the BORG to get a 46 foot plank. (Those 46 foot planks are hard to find at times!) Before the advent of water-proof glues, scarf joints were often screwed or through bolted for security, but in today's world, epoxy adhesives sometimes do the job alone. Boatbuilders routinely send many souls to sea on boats planked with 12:1 scarf joints, a more demanding test than the OP's diagonal brace for a garden table.

Not that hard to make. Some folks make jigs to guide a hand plane. One company sells an attachment for a circular saw to guide the blade at the proper angle for the cut. I, like many others, just line out the taper on the edges of the planks and take it down to close with a jack plane going cross grain, and then use a foreplane to begin to smooth the surface as I get close to the marks. For fine "yachty-snotty" work, I'll finish up with a smoother on the feather edges so the margins of the scarf will look very crisp and exactly aligned. For the most part, however, getting the faces to mate well is the key to a good scarf; smoothing is not that important since it's a glue surface that will never be seen by the guy who will be paying the bill.

[Pete Taran]

Stan's posts are still up, but his profile is marked as "guest". Not sure what that means, but it likely is a way to leave a member's posts in place and restrict them from the site. He has not been active since 29 April. Pity, I always found Stan's posts useful and well thought out.

[Kees Heiden]

Stan gone? That's a loss indeed!

[James Pallas]

I have Stan Covington's e-mail address. If anyone wants to reach him, you can PM me and I'll ask if he's willing to permit me to share it. He is indeed quite knowledgeable about Japanese tools, tool makers and joinery techniques.

Back to the lengthwise joinery: as a boat builder, I have made many a scarf joint. Unlike scarfs illustrated in FWW, cited above showing a 45 degree 1:1 joint, boat builders typically use a 12:1 joint when planking a hull, i.e., one where the taper of the board is stretched out 12 inches long for every inch of thickness. When properly made and glued, 12:1 scarf joints have survived as long as a century on planks of old boats and ships. To the best of my understanding, the reason a scarf is used rather than a lap or bridle joint is because the scarf permits the plank to be bent to shape without forming a localized "hard spot" that deforms the shape of the plank. And it's long enough that the joint is substantially long grain to long grain; a 1:1 scarf is pretty much end grain to end grain.

Experience has shown that a 12:1 scarf, properly made, is very little different in performance to running down to the BORG to get a 46 foot plank. (Those 46 foot planks are hard to find at times!) Before the advent of water-proof glues, scarf joints were often screwed or through bolted for security, but in today's world, epoxy adhesives sometimes do the job alone. Boatbuilders routinely send many souls to sea on boats planked with 12:1 scarf joints, a more demanding test than the OP's diagonal brace for a garden table.

Not that hard to make. Some folks make jigs to guide a hand plane. One company sells an attachment for a circular saw to guide the blade at the proper angle for the cut. I, like many others, just line out the taper on the edges of the planks and take it down to close with a jack plane going cross grain, and then use a foreplane to begin to smooth the surface as I get close to the marks. For fine "yachty-snotty" work, I'll finish up with a smoother on the feather edges so the margins of the scarf will look very crisp and exactly aligned. For the most part, however, getting the faces to mate well is the key to a good scarf; smoothing is not that important since it's a glue surface that will never be seen by the guy who will be paying the bill.
Thats very good James. Scarf joints are so common in boat building that there can't be many wood hulls around without some. You know far more than me about them I very sure. From being around wood boats I've made a few for reasons other than boat building. I understand that boat builders even used them to take out knots and grain run out to make planks sound. They are very strong they will break at the ends maybe but not in the joint if done properly.
Jim

[Marshall Harrison]

I was going to suggest pocket screws. :D

I am curious which way the stress will be applied to the board. Down on the face or on the long edge? As that could dictate the type of joint to use.

[Brian Eaton]

Thanks for all of the feedback! I did end up going to easy route and picked up one more 2x4 to complete the frame. That being said, here is an impressive scarf joint!
https://youtu.be/0NtALAKg_xs
1

[bridger berdel]

I've used long scarfs to make rails for decks and such. Done right it's plenty strong.

[Bruce Haugen]

I built an 18’6” canoe from 12’ boards, making the long strips with scarfed joints. You really need to know what you’re looking for in order to find any of those joints. The scarf was 1:8.

[Mike Henderson]

For people who make those long scarf joints (1:12 or even 1:8) - how do you make them so that the two scarfs fit together perfectly? Do you do them by hand or is it a machine operation?

Mike

[Bruce Haugen]

I made a jig that ran against the tablesaw fence.

[Mike Henderson]

I made a jig that ran against the tablesaw fence.

Okay, thanks.

Mike

[James Waldron]

For people who make those long scarf joints (1:12 or even 1:8) - how do you make them so that the two scarfs fit together perfectly? Do you do them by hand or is it a machine operation?

Mike

I've made 'em by hand and by machine. One technique when working with 8/4 mahogany planking when there were about 30 joints to make, I made a "cradle" for a router on a slide that went side to side and up and down 12:1 tapered sides set to fit the width of the planks. That worked reasonably quickly and made very tight fitting faces. Helped out in a shop once where a scarf of two sheets of plywood were made using a guide attached to a circular saw that worked okay. I believe the guide was purchased from West Systems, as I recall. They still have it on offer. https://www.westsystem.com/tools-supplies/scarffer/ When working on Western Red Cedar 5/8 inch stips, 1-1/2 inches wide, I did a bunch by hand. I made a "cradle" with tapered sides and used a jack plane from side to side to cut 'em down close and a "first smoother" to take 'em down to the line. That worked well, but doing enough for a strip planked canoe, it got to be right tedious. I"ve used a router cradle for that work since. I've done plywood planked boats where scarfs of the plywood got done by hand. It's actually easy, since the glue lines serve as guides for making the taper uniform (since marine grade plywood has reliably uniform ply thicknesses and reliably uniform glue line thicknesses).

I once took a turn scarfing some 12/4 white oak planks six inches wide for a historic build. There were four of us in rotation: Step one was to rough cut the taper with an adze and broad axe. Step two was to flatten the surface a bit with a draw knife and take it down to the ball park of the line. Then a scrub plane was used to get close, followed by a jack plane with a good bit of camber. I was on the job for two weeks, and the crew I served on started with two scarfs the first day, four the second day and thereafter we managed seven or eight a day. With enough cheap labor, machines aren't needed. [n.b.: for compliance with Coast Guard requirements, our scarfs were glued with epoxy adhesives and not using historically accurate techniques. The ship's mission includes ocean sailing with volunteer and professional crew and periodic passenger carriage for day trips in ports of call.]

After you've done one by hand, they end up being pretty easy to do. With modern structural glues, the joints are as strong or stronger than the plank itself. Back in the day, the joints would be "glued" with pitch and clench nailed or through bolted for structural strength. Those dudes make scarf joints that survived a century and more on even large hulls in ocean-going ships.