scarf joint sled trubles

Steve-atl · Jan 9, 2019

I’ve made a scarf joint sled for my tablesaw. I checked and double checked to make sure that the sled fence and the blade are parallel and the sled and blade or perpendicular to the top of the saw. So why isn’t my line not straight. See photo

I used a 40 tooth combination blade to cut it. could it be from deflection of the blade

The red line is the edge of the scarf joint

Thanks

DPO · Jan 10, 2019

Steve-atl said:
I’ve made a scarf joint sled for my tablesaw. I checked and double checked to make sure that the sled fence and the blade are parallel and the sled and blade or perpendicular to the top of the saw. So why isn’t my line not straight. See photo

I used a 40 tooth combination blade to cut it. could it be from deflection of the blade

The red line is the edge of the scarf joint

Thanks

Forty tooth blade is for rough cuts, you need an eighty tooth blade for fine work.

jcalkin · Jan 11, 2019

Perhaps from growing up with crappy table saws, as well as the way wood can move around after cutting, I don't depend on them to cut anything perfectly square (though it sure would be nice). Even on quality saws, I've noticed that the stock fence can bow sometimes after tightening. Nevertheless, I glue up the scarf joints as they come off the saw, 40-tooth blades and all. I've gotten to be an ace at squaring everything up on the belt sander, and it's faster than fiddling forever with the table saw. I've known a bunch of luthiers, and none of them have used table saws except for rough work. Scarfing and glueing a dozen necks is quick fun, then they sit around patiently while I use up the previous batch. I give them plenty of time to get squirrelly if they are so inclined, though uke necks are so short that it's not really a problem.

DPO · Jan 11, 2019

jcalkin said:
Perhaps from growing up with crappy table saws, as well as the way wood can move around after cutting, I don't depend on them to cut anything perfectly square (though it sure would be nice). Even on quality saws, I've noticed that the stock fence can bow sometimes after tightening. Nevertheless, I glue up the scarf joints as they come off the saw, 40-tooth blades and all. I've gotten to be an ace at squaring everything up on the belt sander, and it's faster than fiddling forever with the table saw. I've known a bunch of luthiers, and none of them have used table saws except for rough work. Scarfing and glueing a dozen necks is quick fun, then they sit around patiently while I use up the previous batch. I give them plenty of time to get squirrelly if they are so inclined, though uke necks are so short that it's not really a problem.

None have used a table saw except for rough work? Seriously!!
Well I make banjo ukes utilising solid block construction bodies made up of a minimum of 48 small segments cut at very precise angles, all done on the table saw. Google segmented woodturning and find out what a craftsman can do on a table saw. Rough work LOL!!!

DPO · Jan 11, 2019

Done on the table saw.

Steve-atl · Jan 11, 2019

DPO said:
Done on the table saw.

That for posting

Now I want to make one, That's awesome

Steve-atl · Jan 11, 2019

Kekani said:
You got good answers from the OLF already, but your setup has your stock twisting, my guess. Your blade looks good.

Personally, I moved to a sliding miter the other year. At a UGH workshop I taught, oddly, this was THE most asked about and photographed jig.

I saw your post and got my miter saw out. Did you build a jig? My saw will not turn enough to cut a 12º scarf joint using the fence. Will you post a photo of the jig?

Thanks

jcalkin · Jan 11, 2019

DPO said:
Done on the table saw.

I make segmented banjo rims, too. They are fast to make, but the last piece never quite fits. Its not a big deal, as it can be quickly altered on a disk sander to fit. Or the 8 piece layers can be made 4 and 4, then the halves custom fit. Friends of mine made their table saw jigs on a CNC and the eight pieces never quite fit together perfectly for them, either. But, honestly, rims are so easy to make that I'm not inclined to tweak the table saw anymore. I'll try to post some photos later. Your rims look nice. I'm glad the table saw has worked out so well for you.

DPO · Jan 11, 2019

jcalkin said:
I make segmented banjo rims, too. They are fast to make, but the last piece never quite fits. Its not a big deal, as it can be quickly altered on a disk sander to fit. Or the 8 piece layers can be made 4 and 4, then the halves custom fit. Friends of mine made their table saw jigs on a CNC and the eight pieces never quite fit together perfectly for them, either. But, honestly, rims are so easy to make that I'm not inclined to tweak the table saw anymore. I'll try to post some photos later. Your rims look nice. I'm glad the table saw has worked out so well for you.

The table saw has almost nothing to do with it strangely enough. It's all about how the wood moves past the blade, and that comes down to the sled. And the secret to a good sled is the runner and how it fits in the slot, there can be absolutely NO slop or sideways movement
or the angle will be wrong. I cut sixteen blocks per ring, more on a feature ring and they fit together with no sanding.

jcalkin · Jan 11, 2019

DPO said:
The table saw has almost nothing to do with it strangely enough. It's all about how the wood moves past the blade, and that comes down to the sled. And the secret to a good sled is the runner and how it fits in the slot, there can be absolutely NO slop or sideways movement
or the angle will be wrong. I cut sixteen blocks per ring, more on a feature ring and they fit together with no sanding.

That's impressive, Dennis, I must say.

DPO · Jan 11, 2019

jcalkin said:
That's impressive, Dennis, I must say.

I wasted a lot of time and wood with sleds that simply did not work correctly. Then I stumbled upon segmented wood turning and these guys do amazing work with very complex designs using a very simple home made sled. Google ' wedgie sled' if you are interested in the subect. pretty fascinating stuff.

printer2 · Jan 11, 2019

Could it be using a $100 blade rather than a $20?

DPO · Jan 11, 2019

printer2 said:
Could it be using a $100 blade rather than a $20?

Well the finer toothed blade the better imho, however the real cause is almost always the sled, if you are pushing wood past a spinning blade there can be NO unwanted movement in the sled. 90% of the problems are because there is sideways movement between the runner and the table saw slot. Eliminate that and you eliminate most, if not all, of the issues.

Steve-atl · Jan 11, 2019

I have rebuilt the sled with a new design. It is a lot beefier. Right now I am using the fence of the table saw. We Will see if that's better

Thanks

Kekani · Jan 11, 2019

DPO said:
Well the finer toothed blade the better imho, however the real cause is almost always the sled, if you are pushing wood past a spinning blade there can be NO unwanted movement in the sled. 90% of the problems are because there is sideways movement between the runner and the table saw slot. Eliminate that and you eliminate most, if not all, of the issues.

When I used the table for scarfs, I went from a sled to an attachment on my Incra Miter fence; no slop, but because I use blade stiffener, I couldn't go through the whole cut, and the joint still needed some planing on the cutoff section.

In reference to blade teeth, I went through a lot of BB ply at one point and found a CMT combo blade worked well, even for the scarf. When I held my Workshop at the UGH, part of the discussion for scarfs was the use of a ripping, or crosscut because of the angle of cut. There was no consensus other that "use what works". My crosscut in the sliding miter saw works the best for me, and fully cuts the joint. I think it's either 60 or 80, but my combo was 40.

Edited: autocorrect threw in some funky wording.

DPO · Jan 11, 2019

Kekani said:
When I used the table for scarfs, I went from a sled to an attachment on my Incra Miter fence; no slop, but because I use blade stiffener, I couldn't go through the whole cut, and the joint still needed some planning on the cutoff section.

In reference to blade teeth, I went through a lot of BB ply at one point and found a CMT combo blade worked well, even for the scarf. When I had my workshop at the UGH, part of the discussion for scarfs was the use of a tipping, or crosscut because of the angle of cut. There was no consensus other that "use what works". My crosscut in the sliding miter saw works the best for me, and fully cuts the joint. I think it's either 60 or 80, but my combo was 40.

Yes the Incra works well because the runner has adjustment points to take out the slop. Homemade sleds don't tend to, but a simple workaround is to cut a 1 inch slot either ends of the wooden runner and screw a woodscrew part way in to adjust out any play.

Steve-atl · Jan 11, 2019

DPO said:
a simple workaround is to cut a 1 inch slot either ends of the wooden runner and screw a woodscrew part way in to adjust out any play.

Sorry, but are you saying when you screw a woodscrew part way in it spreads the wood and takes out the slop?

DPO · Jan 12, 2019

Steve-atl said:
Sorry, but are you saying when you screw a woodscrew part way in it spreads the wood and takes out the slop?

Correct, take out the slop/play at each end of the runner and you are heading for accurate cuts.

Titchtheclown · Jan 12, 2019

I use my sliding compound mitre saw. Straight out of the box it has positive lock engagement at 15 22.5 30 and 45. The only jig reqirement was a block of wood for length. I used the glue for two halves and flat sand method when it is in two halves it can easily be rough cut on the bandsaw which would make turning easier though I just sanded smooth using a flap wheel on the inside and a grinder on the outside. I only ever did 8 segment and my cheap Ozito is hardly a precision machine and I only made half a dozen or so.
Going back on topic to the 15 degree scarf join, I had to make a jig to get the mitre saw to do 15 (75 relative to vertical) but replaced that with a sled on the bandsaw. I still have to tidy up the ends but the cutting feels more in control the compound mitre saw does not get much use otherwise and the loose end has been known to get catapulted or chewed by the spinning blade which I largely solved by holding it in the jig with masking tape. I much prefer the bandsaw sled and the bandsaw in general.

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