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The Kohnen Scarfing Jig


Randy Torgerson
 

Back in January, John Kohnen and I were discussing scarfing jigs and I showed the jig I used on my table saw.  John said “I've been thinking about a jig (or would it be a fixture? I never can keep that straight) for using a handheld circular saw, so I don't need to clean such a wide behind the tablesaw” 

I have been under house arrest these last few weeks and I have not been allowed to work on the Tolman so I am working on the long neglected Puddle Duck Canoe. 

I will need to scarf some parts for the gunwales so I decided to build the Kohnen Scarfing Jig.   The jig would use my track saw and be portable so I could take it to RiversWest to cut the splash rail for the Tolman.  The jig cuts a 1:8 scarf for material up to 1 inch tall and 1 inch wide.  Since I cut both pieces at the same time the jig opens up to 2 plus change wide.  This was arbitrary since and I can change it in the future. 

The design goals were to:

1.    Not hurt myself
2.    Not hurt the blade by cutting any screws. 
3.    Easy to setup.
4.    Keep myself busy.

I jointed some four foot long 2x4’s on two sides and then planed the boards to 1-1/4 thick.  Two of the 2x4’s will be put on the bottom to keep the jig together in case the plywood was cut though and to allow space to clamp the track to the jig.  I jockeyed the track around and found that 12 inches by 45 inches was the best size for the plywood. 

I screwed the two support 2x4’s on the bottom and then worked out the size of the clamping 2x4’s should be 28 inches.  One of the clamping 2x4’s is screwed to the jig and the other is held in with clamps but I may use wedges in the future since I can now easily cut wedges quickly.

I clamped some scrap in the jig and gave it a whorl.  As you can see from the pictures the jig worked very well.

 

Randy  


Case Turner
 

Last time I used binder clip clamps is when Blake and I built a model PDR for a class project he had in elementary school. 





Sent from not here

On Mar 28, 2020, at 11:57 AM, Randy Torgerson <coots@...> wrote:



Back in January, John Kohnen and I were discussing scarfing jigs and I showed the jig I used on my table saw.  John said “I've been thinking about a jig (or would it be a fixture? I never can keep that straight) for using a handheld circular saw, so I don't need to clean such a wide behind the tablesaw” 

I have been under house arrest these last few weeks and I have not been allowed to work on the Tolman so I am working on the long neglected Puddle Duck Canoe. 

<0121121627 _Medium_.jpg>

I will need to scarf some parts for the gunwales so I decided to build the Kohnen Scarfing Jig.   The jig would use my track saw and be portable so I could take it to RiversWest to cut the splash rail for the Tolman.  The jig cuts a 1:8 scarf for material up to 1 inch tall and 1 inch wide.  Since I cut both pieces at the same time the jig opens up to 2 plus change wide.  This was arbitrary since and I can change it in the future. 

The design goals were to:

1.    Not hurt myself
2.    Not hurt the blade by cutting any screws. 
3.    Easy to setup.
4.    Keep myself busy.

<2020-03-28 11.08.47 _Medium_.jpg>

I jointed some four foot long 2x4’s on two sides and then planed the boards to 1-1/4 thick.  Two of the 2x4’s will be put on the bottom to keep the jig together in case the plywood was cut though and to allow space to clamp the track to the jig.  I jockeyed the track around and found that 12 inches by 45 inches was the best size for the plywood. 
<2020-03-28 11.08.17 _Medium_.jpg>

I screwed the two support 2x4’s on the bottom and then worked out the size of the clamping 2x4’s should be 28 inches.  One of the clamping 2x4’s is screwed to the jig and the other is held in with clamps but I may use wedges in the future since I can now easily cut wedges quickly.
<dummyfile.0.part>

I clamped some scrap in the jig and gave it a whorl.  As you can see from the pictures the jig worked very well.

 

Randy  


--
Dirt


Jove Lachman-Curl
 

Back when I was making my SOF kayak I scarfed all the stringers and gunnels from 10’ wood.
It was a bit tricky to get them with no twist.  Any off squareness of the cut resulted in an eventuated twist from one piece to the next. After my table say jig didn’t work out I ended up clamping then to the bench and using a hand plane. Reading this thread I was just thinking that if the jig was made to overlap the two pieces the way they’d be in the boat -end to end, then any angular inaccuracy would cancel out.
Im a big fan of moving the smaller object, long skinny noodles of wood in a table saw is a pain. Next time I rip stringers i want to try it with the wood clamped to a long bench or saw horses, and a skill saw with a good fence.
-Jove


On Mar 28, 2020, at 2:04 PM, Case Turner <casesturner@...> wrote:

Last time I used binder clip clamps is when Blake and I built a model PDR for a class project he had in elementary school. 

<image0.jpeg>



Sent from not here

On Mar 28, 2020, at 11:57 AM, Randy Torgerson <coots@...> wrote:



Back in January, John Kohnen and I were discussing scarfing jigs and I showed the jig I used on my table saw.  John said “I've been thinking about a jig (or would it be a fixture? I never can keep that straight) for using a handheld circular saw, so I don't need to clean such a wide behind the tablesaw” 

I have been under house arrest these last few weeks and I have not been allowed to work on the Tolman so I am working on the long neglected Puddle Duck Canoe. 

<0121121627 _Medium_.jpg>

I will need to scarf some parts for the gunwales so I decided to build the Kohnen Scarfing Jig.   The jig would use my track saw and be portable so I could take it to RiversWest to cut the splash rail for the Tolman.  The jig cuts a 1:8 scarf for material up to 1 inch tall and 1 inch wide.  Since I cut both pieces at the same time the jig opens up to 2 plus change wide.  This was arbitrary since and I can change it in the future. 

The design goals were to:

1.    Not hurt myself
2.    Not hurt the blade by cutting any screws. 
3.    Easy to setup.
4.    Keep myself busy.

<2020-03-28 11.08.47 _Medium_.jpg>

I jointed some four foot long 2x4’s on two sides and then planed the boards to 1-1/4 thick.  Two of the 2x4’s will be put on the bottom to keep the jig together in case the plywood was cut though and to allow space to clamp the track to the jig.  I jockeyed the track around and found that 12 inches by 45 inches was the best size for the plywood. 
<2020-03-28 11.08.17 _Medium_.jpg>

I screwed the two support 2x4’s on the bottom and then worked out the size of the clamping 2x4’s should be 28 inches.  One of the clamping 2x4’s is screwed to the jig and the other is held in with clamps but I may use wedges in the future since I can now easily cut wedges quickly.
<dummyfile.0.part>

I clamped some scrap in the jig and gave it a whorl.  As you can see from the pictures the jig worked very well.

 

Randy  


--
Dirt


Richard Green
 

Whenever I’ve needed long wood, over say 12’, for a toe rail or somesuch I’ve knocked together a jig on a table saw sled piece of ply with a couple 1X2 or 2X2 as available for a 12 to 1 scarf.  Maybe done this four or five times over the years.  Always works well, easy to control the wood to assemble a 24’ rail length.  Small boats, small dimensional wood.  Below, gluing a 12 to 1 scarf for the toe rail when I built Jaunty.  When gluing it’s important to have good support to hold the joint, visible between the clamps, firmly in place, straight and level or perhaps flat.

Rich


On Mar 28, 2020, at 3:25 PM, Jove Lachman-Curl <jovelc87@...> wrote:

Back when I was making my SOF kayak I scarfed all the stringers and gunnels from 10’ wood.
It was a bit tricky to get them with no twist.  Any off squareness of the cut resulted in an eventuated twist from one piece to the next. After my table say jig didn’t work out I ended up clamping then to the bench and using a hand plane. Reading this thread I was just thinking that if the jig was made to overlap the two pieces the way they’d be in the boat -end to end, then any angular inaccuracy would cancel out.
Im a big fan of moving the smaller object, long skinny noodles of wood in a table saw is a pain. Next time I rip stringers i want to try it with the wood clamped to a long bench or saw horses, and a skill saw with a good fence.
-Jove


On Mar 28, 2020, at 2:04 PM, Case Turner <casesturner@...> wrote:

Last time I used binder clip clamps is when Blake and I built a model PDR for a class project he had in elementary school. 

<image0.jpeg>



Sent from not here

On Mar 28, 2020, at 11:57 AM, Randy Torgerson <coots@...> wrote:



Back in January, John Kohnen and I were discussing scarfing jigs and I showed the jig I used on my table saw.  John said “I've been thinking about a jig (or would it be a fixture? I never can keep that straight) for using a handheld circular saw, so I don't need to clean such a wide behind the tablesaw”  
I have been under house arrest these last few weeks and I have not been allowed to work on the Tolman so I am working on the long neglected Puddle Duck Canoe. 
<0121121627 _Medium_.jpg>

I will need to scarf some parts for the gunwales so I decided to build the Kohnen Scarfing Jig.   The jig would use my track saw and be portable so I could take it to RiversWest to cut the splash rail for the Tolman.  The jig cuts a 1:8 scarf for material up to 1 inch tall and 1 inch wide.  Since I cut both pieces at the same time the jig opens up to 2 plus change wide.  This was arbitrary since and I can change it in the future.  


The design goals were to:

1.    Not hurt myself
2.    Not hurt the blade by cutting any screws.  
3.    Easy to setup.
4.    Keep myself busy.
<2020-03-28 11.08.47 _Medium_.jpg>

I jointed some four foot long 2x4’s on two sides and then planed the boards to 1-1/4 thick.  Two of the 2x4’s will be put on the bottom to keep the jig together in case the plywood was cut though and to allow space to clamp the track to the jig.  I jockeyed the track around and found that 12 inches by 45 inches was the best size for the plywood. 
<2020-03-28 11.08.17 _Medium_.jpg>

I screwed the two support 2x4’s on the bottom and then worked out the size of the clamping 2x4’s should be 28 inches.  One of the clamping 2x4’s is screwed to the jig and the other is held in with clamps but I may use wedges in the future since I can now easily cut wedges quickly. 
<dummyfile.0.part>

I clamped some scrap in the jig and gave it a whorl.  As you can see from the pictures the jig worked very well.

 

Randy  

-- 
Dirt


 

That's real neat, Randy, very clever! And thanks fpr naming it after me. <blush> ;o) That's very much the sort of thing I was thinking of, but I don't have a track saw, so I was thinking of using a fence. That'd require more attention from the operator, but could be mounted permanently to the contraption. Does anyone know if it's a "jig", or a "fixture"?

Congratulations on actually building yours, and not just thinking about it. <g>

On 3/28/2020 11:57 AM, Randt T wrote:
Back in January, John Kohnen and I were discussing scarfing jigs and I showed the jig I used on my table saw. John said “I've been thinking about a jig (or would it be a fixture? I never can keep that straight) for using a handheld circular saw, so I don't need to clean such a wide behind the tablesaw”
I have been under house arrest these last few weeks and I have not been allowed to work on the Tolman so I am working on the long neglected Puddle Duck Canoe.
I will need to scarf some parts for the gunwales so I decided to build the _Kohnen Scarfing Jig._The jig would use my track saw and be portable so I could take it to RiversWest to cut the splash rail for the Tolman.The jig cuts a 1:8 scarf for material up to 1 inch tall and 1 inch wide.Since I cut both pieces at the same time the jig opens up to 2 plus change wide.This was arbitrary since and I can change it in the future.
The design goals were to:
1.    Not hurt myself
2.    Not hurt the blade by cutting any screws.
3.    Easy to setup.
4.    Keep myself busy.
...
--
John <@Jkohnen>
Self respect: the secure feeling that no one, as yet, is suspicious. (H. L. Mencken)
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Randy Torgerson
 

John,

You are very welcome for the naming.   Cutting the scarfs with the track saw is much less scary than cutting the scarfs with the tablesaw.  In the next few days I will cut the scarfs for the gunwales and then glue them up. 

Randy


Jove Lachman-Curl
 

Ok..... I had to google it!
The most basic difference, is that a jig is a type of tool used to hold and support the workpiece but in addition to this, A Jig also controls the location or motion of tool. On the other hand, a fixture is a support or work holding device used to hold work in place. It never guide the tool.”


On Mar 29, 2020, at 3:42 PM, Randy Torgerson <coots@...> wrote:

John,

You are very welcome for the naming.   Cutting the scarfs with the track saw is much less scary than cutting the scarfs with the tablesaw.  In the next few days I will cut the scarfs for the gunwales and then glue them up. 

Randy


 

Thanks for looking that up, Jove. I'll have to print that out and post it in the shop so I can remember. <g>

So, Randy's Kohnen Scarfing Jig is clearly a "jig". Something that, say, positions stock on a drill press table to bore evenly spaced holes is clearly, a fixture. But what about the device Randy used to cut scarfs on the table saw? It doesn't guide the tool, but it actively guides the stock into the tool. The same conundrum applies to countless table saw sleds and guides. Hmmm... How many angels can dance on the head of a pin? When in doubt, I'll just call them "gizmos". <g>

On 4/1/2020 10:40 PM, Jove wrote:
Ok..... I had to google it!
“The most basic difference, is that a *jig* is a type of tool used to hold and support the workpiece but in addition to this, A *Jig also* controls the location or motion of tool. On the other hand, a *fixture* is a support or work holding device used to hold work in place. It never guide the tool.”
--
John <@Jkohnen>
I am patient with stupidity but not with those who are proud of it. (Edith Sitwell)
--
This email has been checked for viruses by AVG.
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Gerard Mittelstaedt
 

Some years ago I made a "scarfing jig" by welding a few pieces of angle iron, making a frame, and bolting a router on to a heavy plywood carrier to move back & forth across the 4 ft  width of a piece of plywood.  It sort-of worked,but the 1/4 in plywood (yes the plain stuff not the high dollar stuff0 did not want to lie flat enough that there in lied the difficulty.  - - since I have sandwich secured  plywood sheets between layers of 2x stock and scarfed with a belt sander using a rather coarse sanding belt. 
  Then at glue-up doing the thin epoxy first for soak-in and epoxy thickened with corn starch or very fine wood flour for adhesive glue-up seems to work great.  use a couple of very small finishing nails to keep the scarf from squeezing apart as I clamp the whole scarfed area with 2x on each side - wax paper between the 2x and the plywood and some added thickness in the middle (remember I am scarfing whole 8ft x 4ft plywood sheets) to keep the clamping tension sufficient in the middle..  Yes, this is odd business, but what can one do when one wants plywood more than 8 ft long and has decent bending qualities.  It worked for me - may work for you.   - AND the work surface was indeed large to accommodate the length of the 2 pieces being scarfed.  - - Best of luck on your projects -
Gerard Mittelstaedt in McAllen, (deep south) Texas


On Fri, Apr 3, 2020 at 2:20 PM John Kohnen <jkohnen@...> wrote:
Thanks for looking that up, Jove. I'll have to print that out and post
it in the shop so I can remember. <g>

So, Randy's Kohnen Scarfing Jig is clearly a "jig". Something that, say,
positions stock on a drill press table to bore evenly spaced holes is
clearly, a fixture. But what about the device Randy used to cut scarfs
on the table saw? It doesn't guide the tool, but it actively guides the
stock into the tool. The same conundrum applies to countless table saw
sleds and guides. Hmmm... How many angels can dance on the head of a
pin? When in doubt, I'll just call them "gizmos". <g>

On 4/1/2020 10:40 PM, Jove wrote:
> Ok..... I had to google it!
> “The most basic difference, is that a *jig* is a type of tool used to
> hold and support the workpiece but in addition to this, A *Jig
> also* controls the location or motion of tool. On the other hand, a
> *fixture* is a support or work holding device used to hold work in
> place. It never guide the tool.”
--
John <jkohnen@...>
I am patient with stupidity but not with those who are proud of it.
(Edith Sitwell)


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--
Gerard Mittelstaedt  -- mittel48@...
McAllen, Texas
USA