Tablesaw miter fence that pivots around the kerf edge

[smorgasbord]

So, I'm watching yet another woodworking video (still away from my shop for another week), and the guy is using a Woodpecker's AutoScale miter sled. He's got a sacrificial wood block at the end, kind of like what I did on my miter saw some month's ago, but when I looked at the Woodpecker's site/video, their claim to fame is that fence pivots around a point on the edge of the kerf, so the ruler on top remains accurate at any angle.

Video here:=1s

Still frame here:
[attachimg=1]

My question is: How did they do this? I've looked at the sled base, and it has a few round holes, but nothing that itself slides or arcs, so there must be something in the fence. I haven't yet done a patent search, but perhaps that's next?

Anyone have this? It's, as expected, quite expensive, and won't fit my Inca tablesaw, so I'm looking to see if the pivot mechanism is something I can replicate for my own use.

 

[tsmi243]

Looks like a centerless trunion.  Same thing that lets a table saw blade pivot about the top surface.  The bottom of the fence probably has a curved piece that fits in the slot, so it follows the slot instead of a pivot pin.

 

[smorgasbord]

Looks like a centerless trunion.  Same thing that lets a table saw blade pivot about the top surface.  The bottom of the fence probably has a curved piece that fits in the slot, so it follows the slot instead of a pivot pin.

OK, that kind of makes sense. Any chance you've got a link to drawing of what that might look like, or how to calculate what I'd need to replicate that on my shop-built sled fence?

 

[tsmi243]

You're gonna want a REALLY precise fit.  Any slop in the slot will be amplified over on the right side, where your blade is. 

 

[Tom the Remodeler]

Hi smorgasbord,

As tsmi243 suggests, it's a similar design to a center less trunnion.

If there was ever a patent on the idea it has long since expired since there are several other products out there which have the same feature.

One example would be the MFA fence available for the Mafell Erika saws, which features a length-compensating feature where, no matter the angle, the fence will read the correct length. I absolutely love this feature, and find it particularly handy when cutting wood glazing stops.

I believe many of the double miter fences for the sliding miter saws (Altendorf, Martin, SCM, Felder, etc...) feature a mechanical length compensation design, though I could be wrong as I haven't handled all of them.

Another similar solution is the miter index system, which I included as an option on my KF700. The miter index system is not continuous like the Mafell MFA or Woodpeckers product, but does provide pre-set positions where the miter fence will read correctly:

[attachimg=1]

My suspicion is that this would not be impossible to achieve in a shop-built solution, but depending on how you value your time you'll likely be money ahead buying an engineered solution.... 

 

[smorgasbord]

My suspicion is that this would not be impossible to achieve in a shop-built solution, but depending on how you value your time you'll likely be money ahead buying an engineered solution....

I'm assuming/hoping that my CNC will give me the accuracy I need once I come up with an appropriate design.

 

[smorgasbord]

Fixed video link in first post, so it's not cat chaos anymore!

 

[Svar]

Trunnion is easy to make. I just don't see the point of it. In most designs the fence slides along the miter gauge protractor. You can always bring it to the blade at the turn of a thumbscrew.

 

[Birdhunter]

Woodpeckers has a video that shows the pivot design. I see it as an excentric cam. It would be very difficult to home build.

 

[Svar]

Woodpeckers has a video that shows the pivot design. I see it as an excentric cam. It would be very difficult to home build.

Indeed, Woodpeckers design is not a trunnion, but I wouldn't call that an eccentric cum. The arch that you see in the sled is a section of an oval. It can actually be easily made with a simple router jig: a straight bar with a router on one end and two follower (middle and the opposite end) both sliding along straight perpendicular slots. I could make a drawing later if I have time. The jig is essentially a half of a common oval router jig.

 

[smorgasbord]

Woodpeckers has a video that shows the pivot design. I see it as an excentric cam. It would be very difficult to home build.

Can you post the link? I've looked at 3 different Woodpeckers videos and couldn't spot it.

 

[Birdhunter]

On YouTube, I typed in “autoscale woodpeckers”.

 

[smorgasbord]

On YouTube, I typed in “autoscale woodpeckers”.

Like I said, I've seen a bunch of videos, but none showed the mechanism that I could see.

Not in:=ygUVYXV0b3NjYWxlIHdvb2RwZWNrZXJz=105s&pp=ygUVYXV0b3NjYWxlIHdvb2RwZWNrZXJz=ygUVYXV0b3NjYWxlIHdvb2RwZWNrZXJz

 

[Birdhunter]

What I saw on the YouTube video was just a couple of minutes where a man was showing how the fence moved on a CAD screen. From what I saw, the fence appears to be attached to an arm that moves along an ellipse. This is just an assumption on my part based on just a few minutes of video.

 

[woodferret]

That'd be the 2nd video "AutoScale Miter Sled" he's got listed.  It's an ellipse.  One side looks to be pinned under the extrusion and can slide to and from the elipse arc, which is fixed.  In the "Making of" video, the pivot hole is one right on the edge, forward of the miter slot access opening.

 

[Michael Kellough]

Maybe the arc is an ellipse. The product guy said it’s a spline curve. Whatever you call it a simple curved skate/piece can’t be used because it would jamb wherever the radius changed. I did see that the piece that rides the arc on the underside is round so something very clever is happening on the underside of the drive handle.

I can’t figure it out. I did see the head of a nut protruding above the table when Jeff was sliding the fence into position but you can’t have the fence move like it does if the nodal point is at the front of the fence? Or maybe the nut is a pivot point and the reason for the non-simple arc?

All in all it’s not a trivial thing to replicate even if you have the cad file. In addition to the precise location of the laser engraving relative to the routing which is done on the opposite side of the table, the fence is a custom extrusion. I agree with Tom, if you think this is interesting the practical thing to do is buy it.

I’m very curious about it but do not yet see the need for it.

 

[smorgasbord]

I agree with Tom, if you think this is interesting the practical thing to do is buy it.

I’m very curious about it but do not yet see the need for it.

Unfortunately, my Tablesaw, an Inca 2100, does not have standard width miter slots (they're 20mm wide) and so any miter accessories such as this don't fit without surgery, so if I'm doing surgery might as well try to replicate it on my own.

 

[woodferret]

I hate repeating myself but will explain better.  Make a pivot hole in a board, diameter of a dowel that can be captured by your extrusion.  Draw a set mark 30cm (arbitrary) away on the extension.  For each angle, mark where that previous mark is on the board.  Slide the extrusion along the dowel as need be to maintain the kerf line.  You now have your ellipse from all the marks.  A bracket-pin at your mark on the extrusion will follow your ellipse track and push-pull the extension toward or away from the kerf edge.

 

[edwarmr]

[member=77266]smorgasbord[/member]

Here it is
https://www.woodpeck.com/amfile/file/download/file/VtFPNAtXlEQGluw5uqhHjSnKjbj7iRyx/product/32139/

[attachimg=1]

 

[tsmi243]

I hate repeating myself but will explain better.  Make a pivot hole in a board, diameter of a dowel that can be captured by your extrusion.  Draw a set mark 30cm (arbitrary) away on the extension.  For each angle, mark where that previous mark is on the board.  Slide the extrusion along the dowel as need be to maintain the kerf line.  You now have your ellipse from all the marks.  A bracket-pin at your mark on the extrusion will follow your ellipse track and push-pull the extension toward or away from the kerf edge.

Took me a minute to follow you.  But I get it.  That's clever  [cool]

It also means you're not completely dependent on one end of the fence for location, like I was concerned about- the pivot pin on the opposite end keeps the fence from tweaking/binding.