Author Topic: Scarf Joints?  (Read 7098 times)

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Offline Prarie Bowyer

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Scarf Joints?
« on: March 11, 2012, 11:20:35 am »
Hey guys.

I need to make some scarf joints.  What is the best way to do that?  Router Jig?  Drum sanding sled?  Shooting Board?

If it's not Drum Sanding jig then anyone have the tools for precision jig making and want to trade for a scraping shave? 

Offline Pat B

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Re: Scarf Joints?
« Reply #1 on: March 11, 2012, 12:23:11 pm »
I've done a few scarf joints and always did it by hand on a belt sander.
Make the most of all that comes and the least of all that goes!    Pat Brennan  Brevard, NC

Offline Wildernesshunter

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Re: Scarf Joints?
« Reply #2 on: March 11, 2012, 02:02:21 pm »
I would clamp both pieces together and use the belt sander (stationary).  We use planes in boat building to do this, but we are also scarfing plywood sheets together.  Easy process as long as the ends match perfectly for gluing.

Offline Prarie Bowyer

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Re: Scarf Joints?
« Reply #3 on: March 11, 2012, 02:11:54 pm »
Dont have stationary belt sander. 

Target wood is carbonized bamboo flooring.

Offline Buckeye Guy

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Re: Scarf Joints?
« Reply #4 on: March 11, 2012, 05:45:10 pm »
Belt sander, disc sander, miter saw ,ect.
What tools do you have !
What are you calling a drum sander (sand paper on a drum in the drill press)
done with patience and a sled maybe ,but not the best option
guy
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Offline vinemaplebows

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Re: Scarf Joints?
« Reply #5 on: March 11, 2012, 06:29:25 pm »
I just use a miter saw...
Debating is an intellectual exchange of differing views...with no winners.

Offline bubby

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Re: Scarf Joints?
« Reply #6 on: March 11, 2012, 06:31:37 pm »
failure is an option, everyone fails, it's how you handle it that matters.
The few the proud the 27🏹

Offline sleek

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Re: Scarf Joints?
« Reply #7 on: March 11, 2012, 06:52:04 pm »
Here is a very simple way to make a solid splice.

Take both limbs, and set them end to end laid out as if they were one bow already.

Overlap them 6 inches. ( 6 is the minimum, 8 is best )

Have the upper limb to the left of the lower with that 6 inch overlap.

Using a straight edge and a sharpie, draw a straight line from the upper corner of one limb to the lower opposite corner of the other.

That is the line that will define your splice. Its just a line that resembles a not equal to symbol. Where the equal symbol are you limbs, the slash is your splice.

If you are good with your basic handsaw, clamp both limbs side by side and cut them both on the line at once. You may want to fashion a miter box of sorts to keep you straight.

After the cut is made, test fit the limbs togeather. Any inconsistancies in the cut can be fixed with a 2x4 clamped to a table with 8 grit on top. Pretend this sanding block is a belt sander, and rub the cut limb over it to fix any uneveness ( that word looks strange ) in your joint. Some gap is ok, but anything over 1/8 inch I would for sure fix. Use a good gap filling glue or epoxy. I use tighbond 3. It has worked for me on bows up to 55 lbs no worries.
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline Prarie Bowyer

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Re: Scarf Joints?
« Reply #8 on: March 12, 2012, 01:46:14 pm »
Belt sander, disc sander, miter saw ,ect.
What tools do you have !
What are you calling a drum sander (sand paper on a drum in the drill press)
done with patience and a sled maybe ,but not the best option
guy

I made a drum sander around solid maple slug that I tured up in my lathe.  Mounted it on a 5/16 stainless rod.  Made an adjustable floor under it that bolts to the lathe table

Offline Prarie Bowyer

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Re: Scarf Joints?
« Reply #9 on: March 12, 2012, 01:50:24 pm »
Here is a very simple way to make a solid splice.

Take both limbs, and set them end to end laid out as if they were one bow already.

Overlap them 6 inches. ( 6 is the minimum, 8 is best )

Have the upper limb to the left of the lower with that 6 inch overlap.

Using a straight edge and a sharpie, draw a straight line from the upper corner of one limb to the lower opposite corner of the other.

That is the line that will define your splice. Its just a line that resembles a not equal to symbol. Where the equal symbol are you limbs, the slash is your splice.

If you are good with your basic handsaw, clamp both limbs side by side and cut them both on the line at once. You may want to fashion a miter box of sorts to keep you straight.

After the cut is made, test fit the limbs togeather. Any inconsistancies in the cut can be fixed with a 2x4 clamped to a table with 8 grit on top. Pretend this sanding block is a belt sander, and rub the cut limb over it to fix any uneveness ( that word looks strange ) in your joint. Some gap is ok, but anything over 1/8 inch I would for sure fix. Use a good gap filling glue or epoxy. I use tighbond 3. It has worked for me on bows up to 55 lbs no worries.

These will be for bamboo core laminations  Say 1/4" thick?  That kind of overlap still necessary?  I'm trying to pieces long enough to stick into an ELB design.

Offline sleek

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Re: Scarf Joints?
« Reply #10 on: March 12, 2012, 02:21:08 pm »
The goal in a scarf splice is to have a 6 inch long to 1 inch thick ( 6:1 ) ratio splice. This is optimal.
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

mikekeswick

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Re: Scarf Joints?
« Reply #11 on: March 12, 2012, 05:07:08 pm »
For a core lam you only need them 1/2 inch long, 1/4 is enough.
I make reflex/deflex flatbows with tapered cores that are made with a drum sander so they have to be spliced somehow. The simplest core splice is a scarf joint. If however you intend to make the elb's bend in the handle it is safer to use a fishtail splice.

Offline sleek

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Re: Scarf Joints?
« Reply #12 on: March 12, 2012, 05:09:04 pm »
I have never made a core lam, so I would go with mike on this one. However, if it were just a self bow, I stay with what I said.
Tread softly and carry a bent stick.

Dont seek your happiness through the approval of others

Offline vinemaplebows

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Re: Scarf Joints?
« Reply #13 on: March 12, 2012, 05:14:25 pm »
If the splice is in the handle area I totally disagree, a 45 degree cut is plenty. If you are making a lam bow, it would have to shear from the back, or the handle would have to pop off for there to be any danger. If that happened you have bigger problems.....
Debating is an intellectual exchange of differing views...with no winners.

Offline Prarie Bowyer

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Re: Scarf Joints?
« Reply #14 on: March 12, 2012, 06:45:02 pm »
If that happened you have bigger problems.....

I bet.

So I'll plan on 1/4" lam for the first one and 1 1/4" overlap.  The elb design I'm considering won't bend in the handle or not right at the handle.  I may pin them with 1/8" dowels to assure alignment during glue up.  Oh wait.  I'll need to grind the lam any way... So I'll just clamp them to a straight form with news paper under them and use a bit of tight bond.  Then when the 3 lams come togeather I'll use the almighty URAC (heavenly light and music).