I've had a 55" rail with a track saw for a while now, which has been working well. I also had a 118" Makita rail that I used for ripping 8ft lengths of plywood. As it happened, I never needed accurate cuts, I was always rough sizing the pieces. Recently I needed to make an accurate, 8ft long cut and it turns out the Makita rail was not straight. Using parallel guides the dimension in the middle of the cut was almost 1/8" different than the ends. I just went out a bought a FS 2700 (106") rail to try and get a straight edge. I adjusted my saw to take out all the play and made some test cuts where I rip a piece and then fold the cut edges over. The edges are much better, but there is still almost 1/16" difference in the middle. If I rip two pieces and lay them next to each other there are very visible gaps. What type of tolerance should these rails have? Is there a trick to getting straight cuts?
FS 2700 Straightness
- Thread starter mkurtis
- Start date
First, welcome to the forum.
Second, sorry that you are not getting the perfect cuts we all expect.
Next, and please do not take this personally: When using the long rails to make long cuts often we hear about issues. Technique often seems to come into play. I certainly know that I did it until I got advice here but making sure that you are not supplying side ways pressure to the rail - especially about midway may be something to look at. That might not be the case in your situation but might be worth a try.
Peter
Second, sorry that you are not getting the perfect cuts we all expect.
Next, and please do not take this personally: When using the long rails to make long cuts often we hear about issues. Technique often seems to come into play. I certainly know that I did it until I got advice here but making sure that you are not supplying side ways pressure to the rail - especially about midway may be something to look at. That might not be the case in your situation but might be worth a try.
Peter
Hi,
Welcome to the forum! [smile]
What is the material supported on? If there is up / down flex that can also cause side ways deflection.
Seth
Welcome to the forum! [smile]
What is the material supported on? If there is up / down flex that can also cause side ways deflection.
Seth
ear3
Member
When you set the rail, also make sure you're not stressing the end too much. It's naturally straight, but can flex a bit under pressure.
I'm always curious why people choose to get the 2700 rather than the 3000mm rail? If you find that there is an actual problem with the rail, you might consider exchanging it for the longer 3000mm one, which would allow you full diagonal cuts on a 4x8 sheet, and edge jointing/ripping a 9ft board. I think the premium cost is worth the extra capacity.
I'm always curious why people choose to get the 2700 rather than the 3000mm rail? If you find that there is an actual problem with the rail, you might consider exchanging it for the longer 3000mm one, which would allow you full diagonal cuts on a 4x8 sheet, and edge jointing/ripping a 9ft board. I think the premium cost is worth the extra capacity.
The piece is supported on some 8020 rails running between sawhorses. Then I laid a old piece of 3/4 AC plywood on those to act as a sacrificial surface.
How do you set the rail? I've been laying on end down and then gradually laying down along the length to try and minimize side load. I have a woodpecker 36" straight edge that I clamped down to the wood along the back edge in the middle to try and stiffen the rail and it made no difference in the cut. If I slide the straight edge along the back side I can't tell that the rail isn't straight. It's very frustrating because I've had the same problem with two different rails from two different manufacturers. It seems unlikely they are both warped.
Ed: I got the 2700 because it was the longest rail I could fit in my car. The Makita 3000 I bought online and had shipped so I thought maybe it got bent in shipping. I wanted to eliminate that possibility with the Festool.
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How do you set the rail? I've been laying on end down and then gradually laying down along the length to try and minimize side load. I have a woodpecker 36" straight edge that I clamped down to the wood along the back edge in the middle to try and stiffen the rail and it made no difference in the cut. If I slide the straight edge along the back side I can't tell that the rail isn't straight. It's very frustrating because I've had the same problem with two different rails from two different manufacturers. It seems unlikely they are both warped.
Ed: I got the 2700 because it was the longest rail I could fit in my car. The Makita 3000 I bought online and had shipped so I thought maybe it got bent in shipping. I wanted to eliminate that possibility with the Festool.
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From what you are saying it sounds more like technique to me, have you tried a test cut by just laying the track down with no clamps and seeing what the results are like, some here use clamps all the time where as some never use clamps, on ply wood I don't as a rule use clamps, I'm right handed but when I cut with the track saw I use my left hand.
Maybe you could check the straightness by drawing a line using one side of the rail, turn it over and draw a new line, next to the previous one?
If there's a probleem with the rail there should be a distance (in the middle) between the lines. When the lines are parallel, the rail is not the problem.
Using an extra 'support', square on the rail somewhere in the middle of the lenght, maybe can solve the problem of bending sideways.
On the other hand, the warping could be a result of tension in the plywood, I think.
This can be resolved by cutting the plywood with rough dimensions first and then 'format' it.
If there's a probleem with the rail there should be a distance (in the middle) between the lines. When the lines are parallel, the rail is not the problem.
Using an extra 'support', square on the rail somewhere in the middle of the lenght, maybe can solve the problem of bending sideways.
On the other hand, the warping could be a result of tension in the plywood, I think.
This can be resolved by cutting the plywood with rough dimensions first and then 'format' it.
Michael Kellough
Member
mkurtis said:
A Festool rail is pretty straight but it isn't a precision instrument.
It is straight enough for general joining needs such as when you will attach a bendable strip of wood to the ripped edge.
It might not be straight enough to join two wide stiff boards like plywood.
Considering that it's difficult to know if the rail is perfectly straight you could just assume that it is not perfect.
There is a trick for getting tight fitting pieces even with a bent rail.
If your goal is to join two pieces of wood with the minimum gap then set up for a mutual cut so that the out-of-straightness is complementary.
Fit the two boards as close together as possible.
If they have both been ripped with the same rail the same way there will be a bit of space between the boards in the middle and they'll be touching at the ends. [If the rail is concave along the cutting side. The boards will touch in the middle and be appart at the ends if the rail is convex.]
Set the guide rail so that the width of the kerf covers the edges of both mating boards and simply cut again. This is one of the oldest tricks in the book, or at least on this forum. Sometimes it's described as "jointing with the 55" if you want to read more.
Also, like Holmz said, some plywood has internal tension so it bends after you cut it.
Natural solid wood is even more likely to bend after ripping so it best in both cases to rip each side a few mm proud and let the tension out and then re-rip to final size.
Michael Kellough said:
I am not so sure. I did the mark and flip test with all of my rails. Used a pfeil precision marking knife. On the 3000 rail there was no visible difference what so ever. Only on two rails did I find any deviation. The 1400 and the 800. Less than 0,1 mm over the lenght. Divided by two because of the flip method used. So less than ,05 mm.
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