Reducing rail guide slop when in MFT/3 rail system

[dan1000]

I'm new to Festool and to woodworking. I'm trained as a computer scientist, so precision, repeatability, and elimination of errors are all things that are in my blood.

The guide rail on my MFT/3 is imprecisely held by the guide rail system. Specifically, there is about 0.25mm of left-right slop allowed by the tooth that engages in the underside of the rail once the rail is lowered. Although the tooth is tapered to allow easy insertion when lowering the rail, the tooth is not quite wide enough to truly "hold" the rail in a slop-free fashion.

Here are two pictures of me measuring the distance between the rail and a clamped block, showing the extent of the slop. I was careful not to move the gauge.

Why do I care? I suppose it's just for overall repeatability when cutting a series of pieces with the work up against a stop. I can certainly arrange for the workpieces to be repeatably positioned, but if the guide rail slops around (albeit only 0.25mm), that repeatability is diminished. The TS55 that I use has a slop adjustment for the rail, and that works very well. It seems silly to have that fairly tight, only to have the rail itself move about. Is it much ado about nothing? Probably, but one of the things I know about errors is that they multiply over the course of a project, so every reduction probably helps.

Here's my rocket science fix: I affixed a piece of masking tape to the tooth, increasing its width enough to remove the slop. Perhaps I can do a little better than this over time, since masking tape will likely wear out. But the price and minimal effort were both right, and it seems to work well.

Here are a couple of pics showing the left/right slop that remains - about 100 micrometers. I'm not sure I'll do much better than that, even with a harder tooth-build-up material (epoxy?).

Thanks to everyone on this board for the wealth of information that is allowing a newbie like me to actually build precision-joined items. My contribution in this post is extremely small, but it's what I have available to give back right now, so there it is.

Questions: 1) Why didn't Festool make the tooth a little wider at the bottom, removing this slop issue completely? 2) Has anyone come up with a longer-lasting solution than masking tape?

Dan Freedman,
Honolulu

 

[Brice Burrell]

Dan welcome to the FOG, one method is to torque the rail a little while mounting it to the rear mounting bracket of the MFT table so it doesn't fit exactly in the tooth or tab in the front bracket without being twisted or torqued slightly. This torque holds the rail in the same position each time.

 

[dan1000]

Brice - great idea, I will try that out. However, I'm also keen to keep the guide square to the rails, and also to keep the tabletop square to the rails too. That way, all of the other hints and tricks about repeatably positioning the workpiece at various angles (such as 45 degrees) will still work.

Thanks

Dan

Dan welcome to the FOG, one method is to torque the rail a little while mounting it to the rear mounting bracket of the MFT table so it doesn't fit exactly in the tooth or tab in the front bracket without being twisted or torqued slightly. This torque holds the rail in the same position each time.

 

[Brice Burrell]

Dan, with the method I described you still set the rail square, the tooth/tab should be adjusted to hold the rail perfectly square.

 

[Pete Pedisich]

Dan,

Been doing the same thing with the tape on the tab for 3 years now. I have wondered if the self adhesive foil tape for HVAC would last longer....

Pete

 

[Les]

Brice's technique has been used by many users here successfully. You only need to have 1mm of lateral pressure to maintain squareness and repeatability.

As I've found out, if you think Festool has screwed up, they probably haven't and there is an answer you haven't come up yet. I've been bitten more than once. :

 

[dan1000]

Thanks to all for the information and suggestions.

Dan

 

[Gabriel]

After months of using the MFT/3 I still find it extremely imprecise. I can't use it without investing a huge amount of time checking its squareness with an engineer square, and it's never perfect. Even worse: neither the crosscut is square because the guide is never completeley parallel to the mdf top...

 

[MarkF]

Strange...after 3 years of using my MFT I find it very precise.  Unless I need to take the guiderail off I never have to adjust it. To square it I use an 18in long, 45degree drafting triangle and a ~12in square of 1/2in plywood on the table to lift the triangle to the bottom edge of the guiderail.  The triangle meets the edge of the guiderail and the fence. Takes all of 15 seconds. 

 

[Michael Kellough]

After months of using the MFT/3 I still find it extremely imprecise. I can't use it without investing a huge amount of time checking its squareness with an engineer square, and it's never perfect. Even worse: neither the crosscut is square because the guide is never completeley parallel to the mdf top...

You might prefer orienting your guide rail and fence to the grid
of holes in the MFT surface rather than the frame. The hole pattern
is amazingly precise so simply using well fitted pegs in the holes
the guide rail and fence can be set to 90 degrees to one another
with great precision. QWAS Dogs are made to fit those holes. 

Check out the Manuals links for more info.

 

[Gabriel]

Thanks! I'll try these ideas.

 

[kave]

After months of using the MFT/3 I still find it extremely imprecise. I can't use it without investing a huge amount of time checking its squareness with an engineer square, and it's never perfect. Even worse: neither the crosscut is square because the guide is never completeley parallel to the mdf top...

I found out exactly the same. I feel I get more precision with the guide rail loose.
In my book the MFT/3 is better suited for other work than repeatable quick cuts.
I see when I get the table saw in to the garage. Maybe I'll just sell the four weeks old MFT/3.

 

[kev carpenter]

heres my mft [big grin]

 

[Peter Hamilton-Scott]

heres my mft [big grin]

Kev, I have exactly the same stands that you show in your picture. Your MFT is perhaps less polished than the Festool MFT but it's functional, I'm sure. Have you securely mounted the MDF top to the stands somehow? That is, is there something under the MDF we can't see in the photo or does it just rest on top?

Your MFT gives me some ideas about how to use my stands. I bought mine originally to make it a bit easier for slopping on coving cement when I did the coving in all the rooms. Since then, my stands have not been used. Your MFT gives me some ideas.

 

[Peter Hamilton-Scott]

Dan welcome to the FOG, one method is to torque the rail a little while mounting it to the rear mounting bracket of the MFT table so it doesn't fit exactly in the tooth or tab in the front bracket without being twisted or torqued slightly. This torque holds the rail in the same position each time.

Dan, like Brice suggests, torquing the rail, albeit ever so lightly is the best approach. When I got my MFT/3 I was a bit disturbed about doing it as I thought the rail stops were out of alignment. I did post about this elsewhere and Shane PM'd me to put my mind at ease and explained the way it's meant to be. Even with slop my TS55 cuts were still accurate enough and with the rail torqued the cuts were better still. So, torque the rail and throw the masking tape away. The rail and the tab were meant for each other.

 

[Dave Ronyak]

Dan,

Have you checked your TS 55 saw to determine the amount of slop possible in the kerf due to free play in the hinge pin of the plunge mechanism?  In my saw, that freedom of movement exists.  I don't have a means to measure it precisely, but I suspect it may be near the order of magnitude of that in the fitment of the Guide Rail tapered tab mechanism.  I have not found the slight amount of free play in that tab mechanism to cause any problems, although I can imagine them if bevel cutting wide panels which are thereafter to be joined to form mitred corners.  Pre-stressing the Guide Rail laterally a slight amount is the favored way of dealing with this issue, as Brice stated.  Consistent position of the operator relative to the sawing operation is also helpful to minimize errors due to imposing side forces during the cut.

Dave R.

 

[wnagle]

I often wonder why Festool didn't design the alignment pin as a hardened cone shaped pin in a mating cone shaped socket.  And the socket could even have a slight concentric adjustment side to side to fine tune the alignment. 

I may try to modify mine to see if I can improve on the repeatability of the alignment.

 

[sl_1800]

In my book the MFT/3 is better suited for other work than repeatable quick cuts.
I see when I get the table saw in to the garage. Maybe I'll just sell the four weeks old MFT/3.

I just bought a MFT3 this week and I love it.  I only see a slight issue with the fence, it needs a measuring system on it.

 

[tom.smith]

Throw one of these on your fence and you've got it. They just stick on and cost $4.

 

[jcierra]

Months later, and the problem still exists with new MFT/3 rails.  After my own frustrations with it, I complained to the shop where I bought it, only to find that theirs had the same problem.  Even the small amount of wiggle translates to cutting errors.

Yours is a good hack to fix the problem.  For all the advertised repeatability of the table and saw, this was Festool's poor design.