cutting in a straight line

[Lucky Dave]

I use a TS 55 on a dual MFT 3 with guide rail.

Cut a 38" x 20" board. Then, just double checking, took at close look at squareness.

Short story, much to my suprise I found the 38" side not straight! Bulged out about 1/16 then narrowed down to about 1/32 off straight. Checked straightness with MFS 700.

Using Festool 48t blade, speed 6, cutting baltic birch at moderate feed rate.

Inspected blade. Looks good with some resin or whatever buildup. Cleaned with blade cleaner and knocked/brushed off loose sawdust from saw.

What else should I consider.

Thanks

Dave

 

[Administrator_JSVN]

Look at technique.

I would guess the rail was clamped.

You may have unintentionally exerted pressure against the saw.

That's why you see the bow in the cut.

 

[Theshipstore]

Having been there and done that, I agree with Shane as the cut was being made inavertingly side pressure was put on the rail as the cut was being made. It take some time to get used to only applying down pressure during the cut. It is a short learning curve to correct this minor mistake.

 

[wow]

Having been there and done that, I agree with Shane as the cut was being made inavertingly side pressure was put on the rail as the cut was being made. It take some time to get used to only applying down pressure during the cut. It is a short learning curve to correct this minor mistake.

Yep, another vote for (against?) your technique.

You really need to be 'gently guiding' the saw straight through the wood from behind.  Even though your hand is somewhat on top of the saw, you need to 'think' that you are pushing straight forward at the base - no side or downward pressure - just straight forward. I really noticed it on my long guide rail when the saw was new to me!

It probably took me longer to type this than it will take you to figure it out, now that you are aware of it.

I can't leave without saying this, though - have you checked the straightness of your guide rail against a known-good straightedge like a level or the edge of your MFT? It is highly unlikely, but not impossible, that your guide rail isn't straight.

It's worth a quick check...

 

[#Tee]

also check for free play with ts on the rail adjustment knobs.  i would clamp and make a few more practice cuts.

 

[DavidW]

Was this the intial cut you made in the 5x5 baltic birch panel ? If it was, there may of been internal stress in the panel which can cause the panel to bow. I have had this happen when making a rip cut on 4x8 panels of ply and melamine on a vertical panel saw. When I see this happening I over size the panel and recut.
David

 

[Kevin Stricker]

Also check that you are not bowing the guide rail by over clamping and that your two MFT's are co-planar.  When you over tighten the clamps you can create a bow in the rail, which decreases the friction at the center of the rail because it is slightly raised up.  This makes it more likely to deflect to the side.  If your MFT's are not co-planar you can get the same results.

I too have seen panels warp when they are cut.  If you press the panels together after the cut is made and they don't line up together then this is likely the cause as any deflection caused by technique would reflect in both panels.

 

[Stephen B]

[size=12pt]

Seth on another Thread regarding this question, suggested that holding the left edge of the base plate may assist. Since reading this I have used this on occasion when cutting ply and it is helpful.

Just make sure those fingers are on the edge and not hidden under the motor housing and near the rear side of the blade!

 

[Lucky Dave]

Thanks for the suggestions.

 

[Stephen B]

[size=12pt]

Seth on another Thread regarding this question, suggested that holding the left edge of the base plate may assist. Since reading this I have used this on occasion when cutting ply and it is helpful.

Just make sure those fingers are on the edge and not hidden under the motor housing and near the rear side of the blade!

[size=14pt]
Was reminded today when using my TS 55 that this suggestion is a good way to prevent the saw from actually/tending to tip off the rail when blade is set at 45 degrees.