Poll: For Those with a Festool MFT...

@ Patrick Cox

Good Morning Patrick,

Look at the kerf in your MFT/3.  Assuming you have not moved your "key" stops for the fence , the kerf should be pretty much the thickness of the blade.  If it is not, it possible is a result of unequal hand side-to-side hand-pressure/force being applied to the saw as you move thru the cut - a problem I've had and which has been discussed here before.  Once you get "used" to moving the saw thru the cut in consistent fashion - side-to-side pressure on saw, speed, down-ward pressure/force, etc., 2 things happen, kerf in table more closely approximates blade thickness and your width of the cut pieces becomes more uniform like your 1st 2 cuts.

Just my 2 cents worth.  If you are still seeking that "nth" degree of uniformity, see previous articles by Peter Halle or QWAS on squaring up cuts on MFT/3.  I have my MFT/3s set up like Peter, using the fence, dogs, and, depending on the situation, I may check set-up before cutting using either an Anderson plywood square mentioned earlier or a Woodpecker 1281 or Woodpecker OTT 26x16 Precision Square.  The secret - just enjoy the saw dust, there are few activities as rewarding as working with wood.

Don
 
Hi Patrick

Check the green rail adjusters on your TS55. It could be that your saw is not running snuggly on the track and so you have a random variable.

As for your results of the 4 cut test...

These figures do appear acceptable but they could be a little better. I was lucky enough to get a difference of 0.34 mm over 402 mm for the final cut. So, check the rail adjusters and add a bit of extra down pressure on the rail to overcome any lateral force from your saw action.

Peter
 
BTW, have you checked the dogs themselves with digital calipers to see if they are the same size?  There are tolerances with those.
 
Michael Kellough said:
1mm difference on the fourth cut means your angle is 1/4mm off at 430 or so mm.

That is an angular difference of only 0.03 degrees. Considering that the best digital angle finders are only accurate to 0.1 degrees you are more than close enough for woodworking.

Get a bigger scrap of plywood and cut it at 90.03 degrees and save it for re-setting the fence if it gets out of wack in the future.

You can take a break from angle finding and make something.

Thanks Michael.  This is helpful.  1/4mm over 430mm is much better than I was getting before so it sounds like I may have corrected my problem.  And good idea on cutting a square.  Now back to my Sysports and hopefully my cuts are better this time!
 
DrD said:
@ Patrick Cox

Good Morning Patrick,

Look at the kerf in your MFT/3.  Assuming you have not moved your "key" stops for the fence , the kerf should be pretty much the thickness of the blade.  If it is not, it possible is a result of unequal hand side-to-side hand-pressure/force being applied to the saw as you move thru the cut - a problem I've had and which has been discussed here before.  Once you get "used" to moving the saw thru the cut in consistent fashion - side-to-side pressure on saw, speed, down-ward pressure/force, etc., 2 things happen, kerf in table more closely approximates blade thickness and your width of the cut pieces becomes more uniform like your 1st 2 cuts.

Just my 2 cents worth.  If you are still seeking that "nth" degree of uniformity, see previous articles by Peter Halle or QWAS on squaring up cuts on MFT/3.  I have my MFT/3s set up like Peter, using the fence, dogs, and, depending on the situation, I may check set-up before cutting using either an Anderson plywood square mentioned earlier or a Woodpecker 1281 or Woodpecker OTT 26x16 Precision Square.  The secret - just enjoy the saw dust, there are few activities as rewarding as working with wood.

Don

Hi Don,
On my most recent adjustments I did move my feather keys to align them with dog holes like Peter Halle described in his video so that is why my saw kerf in the table is wide.  And on squaring the MFT3, I started out using a Woodpecker 1281 square and I was not successful using that alone to square everything up.  I guess the registration edges were not long enough for me to truly get everything square.  So I will probably go ahead and cut my own larger square for future use.
 
Edward A Reno III said:
BTW, have you checked the dogs themselves with digital calipers to see if they are the same size?  There are tolerances with those.

Hi Ed,
OK, I just checked them...

2 dogs measure 20.5 at the top and 19.96 on the bottom
1 measures 20.48 at the top and 19.95 on the bottom
1 measures 20.47 at the top and 19.93 on the bottom.

So two measure the same and the other two are slightly off.  I am not sure of the significance of this when using these dogs to square up my table.  Although it seems that my safest option now is to use the matched pair to line up my fence if I am going to use dogs to line up my fence.  And that is how I went about it this time.

Thanks for the reminder.
 
As Peter said you can certainly get closer to the elusive 90 degrees.

I once spent hours fine tuning a custom cutting table until the fourth cut
was within 0.001" over 40". So ridiculously close to perfect that I couldn't repeat
the result. Tiny differences in how the rail is secured or how the saw is pushed etc.
show up in the 4 cut trial.

To really get finer than you have you need (as Roger Savatteri once said here) "to have perfect cutting hygiene" which means consistent technique in every aspect of rail/fence placement and saw tracking/pushing as well as keeping the work/fence clear of debris.

Scroll to the bottom of this interesting page to see something Roger made. Search this forum for Roger's name to see more.
 
Michael Kellough said:
As Peter said you can certainly get closer to the elusive 90 degrees.

I once spent hours fine tuning a custom cutting table until the fourth cut
was within 0.001" over 40". So ridiculously close to perfect that I couldn't repeat
the result. Tiny differences in how the rail is secured or how the saw is pushed etc.
show up in the 4 cut trial.

To really get finer than you have you need (as Roger Savatteri once said here) "to have perfect cutting hygiene" which means consistent technique in every aspect of rail/fence placement and saw tracking/pushing as well as keeping the work/fence clear of debris.

...

"Ridiculously close" is a nice observation.

There is no such thing as perfect, only ridiculously close (which I admire).  My day job is electronic measurement where we measure precision (how many digits after the decimal point) and accuracy (how many digits after the decimal point are right) to 6 or more digits, but we can never claim that the measurements are perfect, only ridiculously close.  Furthermore, instruments go out of calibration, and have to be calibrated periodically to make sure they are performing correctly.

Another point - If the precision of a digital tool is two decimal points, two items that measure 20.00 may differ in size more that two items that measure 20.00 and 20.01 respectively.  For example, consider the following three items A, B, and C on a scale:

        A                                                  B                  C
.......^...............................................................^...............................................................^.....
      20.00                                                          20.01                                                            20.02

Note that in this picture, A and B would read 20.00 and C would read 20.01, but the difference in size between A and B is more than the difference between B and C.  When measuring with a digital caliper, this could be deceptive because people tend to believe what the readout says.

When it gets below about 1-2 mm, I trust cutting hygiene more than I trust measurements, unless I'm using stuff that is well designed for precision - router lifts, Incra Ultra positioner, and MicroFence come to mind.  Even those are only good to maybe .2-.3 mm of precision.

While perfect 90 degree miters are a holy grail of sorts, even there you have to be sensitive to the fact the wood shrinks differently in different directions over time.

One important aspect of getting pieces that fit together well is to design them to be forgiving within the limits of the precision that you are willing and able to craft.  A good example of designing for cutting hygiene is to position plugs so you can cut them proud and them trim them to size after gluing them in, rather than having to cut them to the exact length needed to fit flush with a surface.  It's always "perfect" that way.
 
HarveyWildes said:
One important aspect of getting pieces that fit together well is to design them to be forgiving within the limits of the precision that you are willing and able to craft.  A good example of designing for cutting hygiene is to position plugs so you can cut them proud and them trim them to size after gluing them in, rather than having to cut them to the exact length needed to fit flush with a surface.  It's always "perfect" that way.

Lots of great comments in this thread but the above idea and example are particularly good.
 
I had some issues when I first got my MFT . But it was all related to me not having a square,square. You have a decent square.

So the issue must be with either the stock not having a straight edge, small amounts of saw dust between the fence and the stock or the saw not being properly adjusted to the rail.

Do you have any slop when your saw is on the rail?

Are you making sure that you are not pulling the saw to one side or another when making your cuts?

Just trying to figure out if there is something else going on.
 
has anyone seen any stated or measured production tolerances from the makers of Dogs and from FESTOOL?
Hans
 
Well, I could not resist myself and I decided to give it one more try to improve my square cuts.  I used the two dogs that I know are the same size to line up both my fence and my guide rail.  I then also noticed that my fence will move slightly on the end closest to the cut line so since I used my dogs behind the fence when I lined up the fence, I just left one of the dogs behind the fence for support.  I then made sure I took my time and tried to make a straight cut.  And my results did improve.

My 4th cut was 25.5mm at the beginning of the cut and 25.28mm at the end for a difference of 0.22mm over a 378mm 4th cut.  So I believe that is actually 0.22mm over 378x4=1512mm cut, correct?  Anyway, I think I now have my table setup where I need it. 

I also went ahead and cut my sides and tops for my sysports.  Tomorrow I hope to cut the back stretchers and then drill pocket holes or maybe dominos.  If only my day job didn't get in the way!

I appreciate everyone's help.  All very helpful.

Here is a picture of what I did with the Qwas dog to support the end of my fence.

i-fjSjJgG-XL.jpg


Thanks again!

Pat
 
Patrick,

First I must compliment you as the receiver of ideas and also all those who supplied suggestions for the manner in which they were handled.  This thread exhibits what the FOG can be when it is hitting on all cylinders.  Help and Guidance with an absence of attitude.

Secondly,  Your patience is to be commended.

Thirdly,  GLAD to hear that sawdust in the CT is in your future!

Peter
 
Glad you found a way to get good results. 

Positioning the back of the fence against the dogs (and leaving the dogs in place) is what I was trying to explain in post #6. 

I use two dogs of equal size supporting both ends of the fence in addition to the regular protractor and end support, this makes the fence easy to align and much more secure than the protractor and fence end support by themselves.
 
Jeff Zanin said:
Glad you found a way to get good results. 

Positioning the back of the fence against the dogs (and leaving the dogs in place) is what I was trying to explain in post #6. 

I use two dogs of equal size supporting both ends of the fence in addition to the regular protractor and end support, this makes the fence easy to align and much more secure than the protractor and fence end support by themselves.

The logical "next extension" is to remove the fence altogether and push the wood against the dogs. There is then less dust drama with only small contact points, as well as fence flexing drama.
 
[member=40772]Holmz[/member]: The logical "next extension" is to remove the fence altogether and push the wood against the dogs. There is then less dust drama with only small contact points, as well as fence flexing drama.

Not when you want to do repeat cuts using the flipstop on the fence…  [big grin]
 
Fair point [member=5467]Bert Vanderveen[/member]  !
I usually clamp a piece of wood stop to the table, but I can see how everyone's work flow differs. Always good to know a few ways.
 
Yes, I kept the fence not just for one flip stop but for several that correspond to various parts of a project that may be cut at different times.  It reduces crosscut capacity a bit but for most things I don't find this to be an issue.
 
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