One Long Rail or Will Two Work?

[Corwin]

My MFT rail tends to stay on the MFT.  Don't know if I'd want to take it on/off to use for extended cuts elsewhere.

Agree with that Jay.

Bob

I also agree.  And the reason is that if you are mounting your FS 1080/2 rail to your MFT/3 via the MFT's guide-rail brackets and locating the rail with the MFT's side-profile stops, it is far better to leave your guide rail connect to the rear hinged guide-rail bracket.  Otherwise, us perfectionists would notice that reinstalling their rail onto the guide-railbrackets may not install in exactly the same position and thus would have to recalibrate for square -- those side-profile stops may then need readjustment.  Leaving that rail connected saves us all that.  [big grin]

 

[jonny round boy]

I've just cut 6 sheets of ply for some cabinets. In the past I only had one 1400 rail and one 800 rail, and cutting up a full sheet was a pain. The ones I've just done I used 2x1400 rails joined with 2 of the joining bars.

My experience was that it is quite hard to get them 'spot on', but fairly straightforward to get them 'close enough' (and I am a bit of a perfectionist too!).

My first cuts after joining, I trimmed a few mm off the factory edge, then rotated the joined rails 180 degrees to cut the ply strip to the desired width. When I checked, the strip was just shy of 1mm wider in the centre than at the ends (therefore the rail assembly was bowed by less than 0.5mm).

Even with my longest (1800mm/6') level, I wasn't able to measure any deviation in the rail. I couldn't detect it by eye either, looking down the length (not surprising, really - 0.5mm over 2800mm is, as far as I'm concerned, negligible). It really didn't make much difference, but on the future rips instead of measuring/marking the required width just at the ends, I also did so in the centre, and lined up the rail at all three points. If the centre was out, just a slight nudge in the centre of the rail (with the ends clamped) was sufficient to move it slightly. Having said that, I would guess that based on the flexibility of aluminium, you could move the centre of a 3m rail by a few tenths of a mm in the same fashion (though I don't have a 3m rail to check that with).

Checking the rips after cutting, there was still some slight deviation in the widths, generally around 0.5mm. Realistically, that's as accurate as you can expect from timber, marked with a pencil. If you're trying to achieve better accuracy than that, then in my opinion you're going to fail, frustrating yourself in the process.

As a slight aside, I used to work in a kitchen factory where 3050mm long MFC sheets were cut up all day long on a very large & expensive panel saw; it was common to find that the finished pieces were sometimes +/-0.5mm from where they were supposed to be.

If you can afford it, and have room to store it securely, buy the 3m rail if it makes you feel better. If not, join the shorter rails, and take care whilst aligning & using them. It's not a big deal. Get over it (meant in the nicest possible way!).

 

[promark747]

Seems to me that the best way to join two rails seamlessly would be to cut about 1/4" off on a miter saw, taking care to cut the ends in the same orientation as they would be if connected (any miter saw deviation from 90 would be complementary so the errors would exactly cancel each other out).  You could then connect them without the recommended gap, which would make the connection more secure and less prone to twisting or coming slightly out of alignment.

Having said that, I just use the standard joining method.

 

[Bob Marino]

Seems to me that the best way to join two rails seamlessly would be to cut about 1/4" off on a miter saw, taking care to cut the ends in the same orientation as they would be if connected (any miter saw deviation from 90 would be complementary so the errors would exactly cancel each other out).  You could then connect them without the recommended gap, which would make the connection more secure and less prone to twisting or coming slightly out of alignment.

Having said that, I just use the standard joining method.

That would make sense, but  you must be extremely careful about the rail's end touching the floor and getting even a small ping, as that could introduce errors in joining them.

B

 

[Corwin]

Seems to me that the best way to join two rails seamlessly would be to cut about 1/4" off on a miter saw, taking care to cut the ends in the same orientation as they would be if connected (any miter saw deviation from 90 would be complementary so the errors would exactly cancel each other out).  You could then connect them without the recommended gap, which would make the connection more secure and less prone to twisting or coming slightly out of alignment.

Having said that, I just use the standard joining method.

Skip this business of cutting off the end of your rail and just do as you state in the last six words of your post.  Your idea of cutting the ends may make sense in theory, but in the the real world you may not get perfect results due to any slight amount play in your saw or any slight variation in the way you operate your saw.  Any method that relies on the narrow ends to align a much longer rail is not the best practice and has the highest risk of error.

 

[sancho57]

I think you guys are killing it.  I was getting accuracy of 1-2 mm over and 8' sheet of ply  ripped to 23.75" wide widths. With joining 2 rails…

 

[JoggleStick]

So, it seems to me... that whether you choose to use a single long rail or joined rails to 'build' a long rail...
Either way, whether you achieve the accuracy you desire or not has as much, if not more to do, with operator care and skill as it does with the equipment being used.
On the other hand, a skilled and careful operator can achieve the desired accuracy using a range of various equipment and is not 'confined' in this regard; except to the speed and efficiency that the equipment will consistently and reliably perform at- which again, in part, comes back to operator care and skill and perhaps experience.

Have I missed something?

 

[mouppe]

No you haven't missed anything.

 

[Paul G]

I think you guys are killing it.  I was getting accuracy of 1-2 mm over and 8' sheet of ply  ripped to 23.75" wide widths. With joining 2 rails…

Honestly I would generally characterize 1-2 mm variance to be inaccuracy. But that's me, I understand everyone has different expectations.

 

[tiralie]

- which again, in part, comes back to operator care and skill and perhaps experience.

Well said/put.
Doesn't matter if the tool is a TS55 or a hard rock drill operator care, skill and experience make all the difference.

 

[sancho57]

I think you guys are killing it.  I was getting accuracy of 1-2 mm over and 8' sheet of ply  ripped to 23.75" wide widths. With joining 2 rails…

Honestly I would generally characterize 1-2 mm variance to be inaccuracy. But that's me, I understand everyone has different expectations.

over a 8' length?  thats better then I ever got with my table saw. 2mm = .078" thats pretty darned good dood IMO.

Printing paper is about 0.004, my nose hair was about 0.005 (dont ask how I know that).

Also that figure is before I re-adjusted my PGs, now its less then that.

Thats pretty darned accurate If ya ask me.

 

[Paul G]

I think you guys are killing it.  I was getting accuracy of 1-2 mm over and 8' sheet of ply  ripped to 23.75" wide widths. With joining 2 rails…

Honestly I would generally characterize 1-2 mm variance to be inaccuracy. But that's me, I understand everyone has different expectations.

over a 8' length?  thats better then I ever got with my table saw. 2mm = .078" thats pretty darned good dood IMO.

Printing paper is about 0.004, my nose hair was about 0.005 (dont ask how I know that).

Also that figure is before I re-adjusted my PGs, now its less then that.

Thats pretty darned accurate If ya ask me.

That's over a 1/16". At the cabinet shop I worked at many moons ago, if my panels varried that much I'd have been quickly fired. But with a clientele in places like Beverly Hills perhaps my boss had extremely high standards for a reason. Like I was saying, everyone comes to the party with different expectations.

 

[ccarrolladams]

Making accurate cuts with a track saw still requires experience and an attitude of working for high quality.

Perhaps there are circumstances where depending on the anti-skid strips to hold the guide rail in place is good enough, but not when sawing material I bought! Then after the rail, be that one piece or connected rails, are clamped to the correct marks, the next important step is to run the saw along the rail without causing strain and flex. Unless you are making a pocket plunge cut, you want enough rail before the cut so the saw is clear of the work before it is allowed to come to full speed and fully plunged. At the end of the cut you want enough rail the blade is clear of the work before it needs to return to its raised position and then slows down. There will be less tear-out if the work is fully supported firmly. Dust collection will be improved if there is a wide enough sacrificial piece at the end of the cut so that is where the blade can rise, still clear of the work.