Inconsistent Dimensions of Guide Rail Extrusion

Joined
Dec 16, 2014
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78
Location
Canada
I've found that my guide rails vary in size. Is this expected? Has anyone else noticed/solved this?

My sample size consists of 3 Festool guide rails. On 2/3 rails, the slot which guides a tool measures 0.633". The slot on the third guide rail measures 0.631".

I realize a difference of 2 thou sounds like nothing, but I've found it actually makes a very big difference – especially when making an extended rail using the thinner rail (0.631) and a wider one (0.633)! I need to set the adjustment knobs such that the tool is stable on the thinner rail, but in doing so it requires substantial effort to slide the tool on the wider rail.

Photos attached below, in the following order:
- 1x 55" (measures 0.631")
- 1x 32" (measures 0.633")
- 1x 55" LR 32 (measures 0.633")

P.S. Sorry about the imperial measurements... forgot to switch my calliper into metric and didn't want to retake the photos :(
 

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They are extruded aluminum. The fact you are only seeing a 0.002" difference is pretty incredible for a non-machined surface. Inevitable variations in extrusion are the reason why the tools have adjustment gibs.
 
I have a 1.4m rail and 3m rail, I have to adjust the saw each time I swap rails which is a real pain. I thought maybe it was because my old 1.4m rail had a lot of use compared to newer 3m rail. Must really be a problem if you have to join rails?

Doug
 
In a perfect world everything would be the same to the 1 millionth of an inch.  But we don't live in one so we have to use our tools.  It was simpler when we all had to use axes and rocks I guess. 

Try joining the rails together and see what the results are when you cut.  That is all that really matters.

Peter

 
I second Rick's opinion on the .002". A tolerance that small would be difficult to hold consistently on an aluminum extrusion. It would make for a lot of scrap rails. But, I seriously doubt that Festool is calling out a tolerance that tight. My thought is that the actual tolerance Festool calls out on the drawing will be closer to +.005/-.010. That way a TS will probably always fit on a rail albeit a tad loose but then the saw could be tweaked.
 
I must add that I was gobsmacked that when I joined my newly acquired 1400 track (i bought a second track) using the Festool joiners, that they didn't line up perfectly either!  [eek]
I didn't need a magnifying glass either. Quite noticeable. I never had to even think about this happening when I bought my first tracks 7 yrs ago.
 
Just caught this tread and two points sprang to mind (and I am not trying to play devils advocate..he has plenty of paid ones)
1) even digital calipers have a designed tolerance +/- 0.00?
2) are you holding the calipers at exactly the same point and square to the rail section as I suspect that actual part has a slight bevel to make seating of the tools easier.
As Rick mentioned the tools have adjustment gibs, however, my understanding is that these are primarily so they can be adjusted due to wear rather that wear out either the rail or tool platten, it is why they are replaceable as are the green sliding strips and the edge strip you cut through then use to line up your cuts.

Rob.
 
Rob,

It's not that I suddenly felt like measuring my guide rails – I was prompted to measure after I noticed that while having two guide rails connected, the friction required to move a tool increased substantially when transitioning rails. The measurements were just to provide some quantitative data.

You're probably correct about the tolerance of digital callipers, but I believe the tolerance stated in that way applies to absolute values. For a relative difference between two measurements, it shouldn't be much issue.

Anyway, all I hoped to get out of this question is find out whether anyone else had noticed this kind of thing with their guide rails – which it does seem so. It's not a major issue; I understand the inevitable variance in any manufacturing process, and I do appreciate that my rails are within 2 thou in the first place. Anyway, feel free to laugh, but this is something that would make me shop for my next guide rail with a measuring tool in hand, because matched rails exist, it's just a matter of finding them!
 
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