parallel guides not cutting parallel

[paulhtremblay]

I used my parallel guides for the first time to cut cabinet parts and my results were not parallel. I used the parallel guide rails on the 2700 Festool guide rails.

After creating a straight edge with an initial cut (without using parallel guides), I set up my parallel guides. I moved the guides to the middle of the rail so the end tabs touched each other, and moved the end tabs so they were at the same exact spot. I felt with my fingers to make sure they both were exactly the same distance away from the guide rail.

I then ripped a standard piece of MDF (49'' X 97 "") 610 mm wide. I made another rip with the guide rails to create another piece 610 mm wide. Both times, I checked 3 times to make sure the guide tabs were flush against the edge. When I finished each cut, I checked again.

When I put the pieces on top of each other, I immediately could see they were not the same width. I measured them. one measured 609 mm on one end, and 610 mm on the other end. The other measured 610 mm at both ends.

Note that if I had made an error in setting my tab guides, each rip would have had the same exact error, measuring 609 mm at one end and 610 mm at the other.

Also, I noticed that there was a slight bow on the edge of the board. So the boards were not parallel and not straight.

Since 1 mm is too big an error for assembling a cabinet, I had to use a router to fix the error and make my sides slightly narrower, 608 mm.

I am thinking that there is a slight big of deflection when making such a long cut. Because of the position of the MDF, I had to make one cut with my left hand, and one with my right.

Unfortunately, I don't think I can simply rely on the parallel guides to rip long pieces of MDF to size before taking it to my MFT table to cross cut it. I think next time I will rip the sides 615 mm wide, then cut the other dimension about 10 mm to long. I will then have a a pieces slightly wider and longer than needed. Next, I will use the parallel guides to rip the pieces to exact width, and finally use the MFT table to cut them to length. By using the parallel guides on much smaller pieces, I should not get the problems I had with deflection.

 

[roblg3]

How often has this happened?  just once?  the fact that you had to do one of your cuts non-dominant handed sounds like the culprit to me.  if you put the 1mm angled side to the back it shouldn't be a problem that can't be corrected while attaching the back.  wood is going to "breathe" almost that much in seasonal changes.

 

[paulhtremblay]

How often has this happened?  just once?  the fact that you had to do one of your cuts non-dominant handed sounds like the culprit to me.  if you put the 1mm angled side to the back it shouldn't be a problem that can't be corrected while attaching the back.  wood is going to "breathe" almost that much in seasonal changes.

It actually happened twice. I cut some 3/4'' plywood about two weeks ago, using the same technique, and got the same results: 1 mm off.

I think the cut with my left hand came out better. At any rate, given how wide sheet goods are, I can't control what hand I use.

 

[sancho57]

did you cut a little of of one side to reference off of. Everything will be referenced off that edge. to tell ya the truth to be 1 mm out over 2400mm isnt that bad.  Thats a lot better then I ever got using a table saw.

 

[roblg3]

Totally agree that 1mm is absolutely acceptable.  I'm just confused that there could be some thing wrong with the tool or the set up when perfect results were achieved at least once.

 

[paulhtremblay]

Totally agree that 1mm is absolutely acceptable.  I'm just confused that there could be some thing wrong with the tool or the set up when perfect results were achieved at least once.

I too agree that 1mm is not a lot over 2400 mm, so maybe I need to re-think the problem, which is how to handle this small difference. You say to hide the 1mm difference at the back of the cabinet, and that now seems correct, in light of another problem I encountered. I want to start another thread on that, though.

So let my state that the error here most likely doesn't mean a tool problem.

 

[Sparktrician]

Since 1 mm is too big an error for assembling a cabinet, I had to use a router to fix the error and make my sides slightly narrower, 608 mm.

Don't know if you'd considered it, but 608mm is a multiple of 32mm.  I use the 32mm standard and try to keep all my parts to a multiple of that number. 

 

[Tinker]

I have tried the parallel guides with not much success at perfection. Even when bringing those side tabs together, I did not get a perfect parallel cut.  I finally purchased a set of rip guides from RMW and problem solved. 

I think the difference in ease of setup is that the Festoy parallel guides have to be set at the extreme ends (at corners) of the sheet I am working on.  I just end up, especially with full sheet where i cannot support both ends of the sheet, with problems of supporting those end clips and a possible sag to the sheet at either one end or both ends.  With RMW's guides, they can be set up at any points along the sheet.  The operation becomes a lot more stable in setting up as well as accuracy of cut. 

I do have a couple of projects in the works for coming spring where i will be cutting a lot more ply wood than usual.  I am planning to construct a cutting table that will support a full sheet with a little space to spare.  Since I will be moving outside to breakdown full sheets and then going back into the shop for the more intricate cutting, I am hoping i can make better use of the Festoy PG's (with better accuracy)out side and keep my RMW rip guides inside.  I still have my old ATF 55 to use outside while i can leave my new TS55REQ inside.  That way, I can leave saw and one set of guides outside at truck and the other set and saw inside.
Tinker

 

[Sparktrician]

I am planning to construct a cutting table that will support a full sheet with a little space to spare.  Since I will be moving outside to breakdown full sheets and then going back into the shop for the more intricate cutting,

That's exactly what I do.  I made a 4' x 8' grid out of 6 - 2 x 4s that I sit on two sawhorses to do the rough dimensioning.  The open grid allows the loops of the Parallel Guide extensions to drop out of the way.  I can clamp as necessary.  When the grid is completely chewed up, it becomes firewood and I build another.  I also use it for painting parts. 

 

[tjbnwi]

Invest a little time into a knock down cutting table. Doubles as a work table if you need the surface.

One 4x8x3/4 sheet of plywood.

A couple of minutes to set up and take down this one.

Tom

 

[Sparktrician]

Tom, I like that design.  Much more refined than my quick-and-dirty, sacrificial version. 

[smile]

 

[Tinker]

Tom, I like that design.  Much more refined than my quick-and-dirty, sacrificial version. 

[smile]

Ditto.

I really like that you make a spot to store your rails.  I had not thought of doing it that way. I am sure I am going to stea... er, borrow the idea.  I am also toying with the idea to make a smaller cutting table to replace my MFT 600 that has become more of a catch all.  i had been planning to make a cutting table of same design for inside shop but with an old car scissors jack to raise and lower.  None of my MFT's are low enough for me to double as assembly tables for larger projects.  I saw an interesting design on YT this morning where the MFT type top was mounted to four legs constructed by making (for each of four legs) a box for the base and four solid 3x3 legs that slide in and out of the boxes. It looked like maybe 18" of up and down motion.  There was a fairly heavy scissors jack of some sort.  I have a couple of ancient car jacks kicking around in the barn that might find a use if not totally rusted.