More noob MFT help/advice required.. Or MFT rail VS Bench Dogs...

[Glasside]

Hi

I've been using my MFT for breaking down sheet good into panels for some acoustic absorbers I'm making.

It took me quite a long time to get it so everything squared up. And I've pretty much gotten there. More or less. 

My only issue is this.

To make the panels I'm starting by cutting a reference edge with a TS55 and rail.  Then with the MFT I make two sides perpendicular to the reference and this works pretty good. The issue arises when I make the edge parallel to the reference edge. 

It's ever so slightly out of square.  Maybe ~.5mm over 550mm (not more).  This hasn't been a problem until now, but the units I'm making this week have mitred corners and the error is noticeable on the mitres. I'm guessing any tiny error in squaring the MFT is compounding.

My question is - do you think I'd get more accurate 90 degree cuts more easily using a bench dog system as opposed to the MFT + rail?  Or should I be able to get the panel perfectly square with the MFT stock set up? (For info the biggest panel I have to make is 550x570)

Many thanks for any help/opinions...

 

[afish]

been a few discussions here before about this. I got much better results with a 8020 fence and a track hinge should be able to search my posts and see more details 

 

[tsmi243]

How are you lining up for that 4th cut?  Parallel to the 1st, or perpendicular to the ends?

 

[MaineShop]

When I read your post it sounds to me like you may already have the answer that maybe you are out of square by fraction of a mm in terms of your fence to you rail and that issue is compounding by the fourth cut. You may have already done this but I would take a big piece of scrap, the biggest piece you can fit on your mft that you can verify it is parallel and do a scoring cut, not going all the way through, while making sure to reference one of the two parallel edges off the fence, then flip and make another score off the other parallel edge, if the second cut doesn't line up with the first you are out of square and need to calibrate that.

Also I am not sure what you are using for material but when you are doing mitered corners be aware that the thickness of plywood can vary a lot. Not just from sheet to sheet but sometimes within the same sheet, that can be a problem some times if you are concerned about half a mm in variation. Less of an issue with mdf or particle board but not really materials you are often mitering unless they are veneer.

 

[dashboardpws]

Keep in mind that the MFT top has to be slightly smaller than the space where it fits so you can get it in there without having to jump up and down on it. This can lead to a small misalignment between the grid of holes and the frame, which will influence everything you want to do in terms of squaring. With that in mind you might try loosening all four bolts that hold the top, pulling it hard against one side and one end, and retightening the bolts. Then, proceed with your normal squaring process.

 

[Glasside]

How are you lining up for that 4th cut?  Parallel to the 1st, or perpendicular to the ends?

Hi there - for the 4th cut I'm doing it perpendicular to one of the ends.

 

[Birdhunter]

I only use the MFT holes plus dogs for alignment. I check everything with the Woodpecker framing square before cutting. I do use the drop down rail, but square it up the wood with dogs. The protractor has never been used. This method is fast and reliable.

 

[Glasside]

When I read your post it sounds to me like you may already have the answer that maybe you are out of square by fraction of a mm in terms of your fence to you rail and that issue is compounding by the fourth cut. You may have already done this but I would take a big piece of scrap, the biggest piece you can fit on your mft that you can verify it is parallel and do a scoring cut, not going all the way through, while making sure to reference one of the two parallel edges off the fence, then flip and make another score off the other parallel edge, if the second cut doesn't line up with the first you are out of square and need to calibrate that.

Also I am not sure what you are using for material but when you are doing mitered corners be aware that the thickness of plywood can vary a lot. Not just from sheet to sheet but sometimes within the same sheet, that can be a problem some times if you are concerned about half a mm in variation. Less of an issue with mdf or particle board but not really materials you are often mitering unless they are veneer.

Hi there, I think just by sheer logic it must be this.  I'm tempted to try a rail square system to see if I can get squarer.  I try to be as precise as possible is squaring the fence to the rail but there is an error creeping in somewhere!

 

[Glasside]

I only use the MFT holes plus dogs for alignment. I check everything with the Woodpecker framing square before cutting. I do use the drop down rail, but square it up the wood with dogs. The protractor has never been used. This method is fast and reliable.

Thanks for this - I'm rapidly coming to the same conclusion. I have some of the original parf dogs, but they do move around in the holes a little, so I think I may get some of the ones you can tighten.

I'd LOVE to get that framing square but I'm in (not so sunny) Ireland and Woodpecker's are like hen's teeth here - backordered til the end of the year..

 

[Glasside]

Keep in mind that the MFT top has to be slightly smaller than the space where it fits so you can get it in there without having to jump up and down on it. This can lead to a small misalignment between the grid of holes and the frame, which will influence everything you want to do in terms of squaring. With that in mind you might try loosening all four bolts that hold the top, pulling it hard against one side and one end, and retightening the bolts. Then, proceed with your normal squaring process.

I'll certainly give that a go - thanks for the tip.  Much appreciated.

 

[MikeGE]

...

 

[tsmi243]

It's definitely a compounding problem, then. 

Have you seen the 5-cut method?  A $6 set of feeler gauges will make it possible to fix in under an hour. 

Beyond that, this is why some guys prefer parallel guides.  It won't fix the ends being out of square, but it WILL eliminate any deviance on that 4th cut.  I don't have the Festool ones, I just use a ruler with a stop and it works fine. 

 

[Birdhunter]

Re the difficulty of finding a Woodpeckers framing square.... I wonder if a CNC shop could mill a square for you? I use just about any dogs, but really like the ones I can snug up.

 

[Michael Kellough]

“It took me quite a long time to get it so everything squared up. And I've pretty much gotten there. More or less.”

Have you squared the fence to the rail using the 4 cut method or not? If not then you’ve got it less than square and every time you make a less than square cut around the perimeter of the panel it will get farther from square.

Using only dog holes for multiple cuts around the perimeter might be successful but it might not. Festool put the holes in a grid by for clamping convenience not for using dogs instead of the fence but because they are cut by machine the grid is sometimes precise enough for that purpose.

Using a rail square for multiple square cuts might be successful.

If you want to get the squarest possible cuts you should use the 4 cut method to make the fence square to the rail. The possibility to fine tune the fit of a rail square to the fence is very limited. The ability to fine tune the grid of holes is virtually impossible.

When you successfully tune the fence with the 4 cut method you will have a panel that is extremely square. Label that panel and save it so you can make easily make the fence square again in the future.

Keep what dashboard said in mind, every time you fold up the MFT it’s possible that the mdf panel can shift slightly within the aluminum frame. Since the protractor is fixed to the mdf and the fence to the frame they may not remain perfectly square after you fold up or move the MFT.

So, before you do the 4 cut procedure, loosen the screws that secure the mdf to the frame and use a pair of clamps to pull the mdf tight into a corner of the frame (I use the one closest to the protractor) then tighten the screws and do the 4 cut process making adjustments to the fence not the rail.