How Do I Avoid The Holes?

[darita]

When using bench dogs on my MFT, I can see that my cut line is going to run across the holes.  How do I avoid that?

 

[Packard]

I don’t know why that would be a problem, but place a short length of 3/4” stock between the track and each of the dogs.  That will move it over enough to avoid the holes.

Or use your hole saw to cut a 2” or larger disc of 3/4” material and drill a hole in the center that will accept the dogs. 

But why is the hole location an issue?

 

[Crazyraceguy]

The point of not sawing across the holes is that there is no back-up for the cut.
There are a few work-arounds for this, spacers being the easiest, but there are others.
Cutting a dado (or sliding dovetail) in that row and then filling that slot with a thin strip of MDF.
This will bring your zero-clearance back, but it does obscure that row.

 

[Michael Kellough]

“The point of not sawing across the holes is that there is no back-up for the cut.”

That holes also reduce dust collection.

 

[semenza]

Also it might degrade the integrity of the hole for dog fitment?

Seth

 

[rst]

Just move the stops.  I did that on mine and then made a dovetail slot that I can slip an uhmw pladtic strip into.  The blade groove in the plastic then makes lining up cuts easier also.

 

[Michael Kellough]

Just move the stops.  I did that on mine and then made a dovetail slot that I can slip an uhmw pladtic strip into.  The blade groove in the plastic then makes lining up cuts easier also.

He isn’t using the rail hardware so he isn’t using the stops, just dogs, and they put the business side of the rail over the holes.

 

[squall_line]

The spacing arrows that I purchased with my Dashboard Hinge worked a treat for just this very reason.  They make a nice offset from the dogs that keeps the kerf between holes.

 

[Michael Kellough]

Stepping up to the Dashboard hardware is the best option, especially since this is a 1080 MFT.

 

[MikeGE]

The point of not sawing across the holes is that there is no back-up for the cut.
There are a few work-arounds for this, spacers being the easiest, but there are others.
Cutting a dado (or sliding dovetail) in that row and then filling that slot with a thin strip of MDF.
This will bring your zero-clearance back, but it does obscure that row.

I must be missing something important, but why is missing material in seven 20mm sections a problem?  I also don't understand "no backup for the cut."  Using a sacrificial strip, as I do on my MFT-style table, eventually creates a groove along the path of the guide rail in which the rising teeth of the saw blade ride.  So far, I haven't needed a zero-clearance guide on the bottom of the piece I'm cutting.

 

[Jim_in_PA]

I must be missing something important, but why is missing material in seven 20mm sections a problem?  I also don't understand "no backup for the cut."  Using a sacrificial strip, as I do on my MFT-style table, eventually creates a groove along the path of the guide rail in which the rising teeth of the saw blade ride.  So far, I haven't needed a zero-clearance guide on the bottom of the piece I'm cutting.

Because as the cutline passes over those holes, small as they are at 20mm, they leave material unsupported which raises the risk of tearout on the material edge.

 

[peter halle]

Just an accurate spacer between dogs and rail to position.  Then clamp down if not using the hinges.

Peter

 

[MikeGE]

Because as the cutline passes over those holes, small as they are at 20mm, they leave material unsupported which raises the risk of tearout on the material edge.

Maybe I've lived a charmed life with my tracksaws.  I don't recall seeing any hint of tearout on the underside of plywood, Valchromat, MDF, or melamine even when the cut edge is completely unsupported...and I do look at the finished cuts.

The teeth of the sawblade are not cutting down into the hole, but are coming up from the bottom into the piece being cut.

 

[darita]

So why do you think Festool designed it this way?  Anyways, good to know about the Dashboard rail hinge as I already ordered it.

 

[ChuckS]

Snip.
The teeth of the sawblade are not cutting down into the hole, but are coming up from the bottom into the piece being cut.

This is true.

The purpose of the splinterguard (strip) on the guard rail seeks to prevent splinter on the top side of a board, not the underside.

The cutting into the dog holes won't cause tearout on the board, but as SRSemenza said, it could affect the integrity of the dog holes, which may or may not matter depending on what one uses them for.

 

[squall_line]

So why do you think Festool designed it this way?  Anyways, good to know about the Dashboard rail hinge as I already ordered it.

Festool installs stops on the MFT/3 at the factory that allow you to position the hinge in a way that doesn't cut through holes.

Because there is no guarantee that the frame of the MFT is square to the dog holes, Festool specifically does not recommend aligning the guide rail and hinge using dog holes while using the factory fence that is registered along the frame of the MFT.

So, in that sense, Festool didn't "design it this way", because they never intended for the dog holes to be used to register the track in the first place.

 

[darita]

So why do you think Festool designed it this way?  Anyways, good to know about the Dashboard rail hinge as I already ordered it.

Festool installs stops on the MFT/3 at the factory that allow you to position the hinge in a way that doesn't cut through holes.

Because there is no guarantee that the frame of the MFT is square to the dog holes, Festool specifically does not recommend aligning the guide rail and hinge using dog holes while using the factory fence that is registered along the frame of the MFT.

So, in that sense, Festool didn't "design it this way", because they never intended for the dog holes to be used to register the track in the first place.

Thanks for the explanation.  I thought using dog holes to align rails for cuts was by design.  Now I understand that it just happens to be a good way to get 90* cuts using the dog holes.  I wonder if anyone makes dog spacers for the purpose of missing the holes?

 

[Packard]

The point of not sawing across the holes is that there is no back-up for the cut.
There are a few work-arounds for this, spacers being the easiest, but there are others.
Cutting a dado (or sliding dovetail) in that row and then filling that slot with a thin strip of MDF.
This will bring your zero-clearance back, but it does obscure that row.

Most of these tops that have been in service for a while have scoring marks all over the surface from previous cuts.  Each of those scorings will also allow for no backup for the cut.  But the stock itself becomes the “backup” as the blade is entering from the bottom and cutting up.  I don’t see it.

 

[Packard]

Because as the cutline passes over those holes, small as they are at 20mm, they leave material unsupported which raises the risk of tearout on the material edge.

Maybe I've lived a charmed life with my tracksaws.  I don't recall seeing any hint of tearout on the underside of plywood, Valchromat, MDF, or melamine even when the cut edge is completely unsupported...and I do look at the finished cuts.

The teeth of the sawblade are not cutting down into the hole, but are coming up from the bottom into the piece being cut.

I did not read your post when I wrote mine and I made the same point. 

It is why table saws tear out on the bottom and radial arm saws tear out on the top.

 

[Cheese]

Thanks for the explanation.  I thought using dog holes to align rails for cuts was by design.  Now I understand that it just happens to be a good way to get 90* cuts using the dog holes.  I wonder if anyone makes dog spacers for the purpose of missing the holes?

Just to add to squall_line's information, Festool does not recommend you use the dog holes for anything other than clamping options...that's it. Just a nice system to clamp boards to a flat surface for machining. This information came to light after several MFT tops were measured for dog hole location accuracy and they were found to be not particularly consistent.

As far as a spacer goes, I'd suggest an extruded aluminum flat or tube profile. They're light weight, won't warp and are very straight. You'll also never confuse it for just another piece of wood and cut it up accidentally. [eek]