Author Topic: Bad cut with TS55 or springing plywood?  (Read 1699 times)

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Offline Ulmus

  • Posts: 9
Bad cut with TS55 or springing plywood?
« on: March 03, 2018, 10:06 PM »
It has been exciting to get acquainted with my first track saw, the TS55 (with two connected 1400-mm guide rails).  One of my first tasks was to cut two 3-1/2" strips off the side (i.e. full length, 8') of a new sheet of plywood (New Zealand pine, 18-mm, 11-ply, pre-finished).  When I layed the strips flat and together edge-to-edge in the same orientation as cut from the original sheet, I was surprised to see opposite bows so that the edges were tight together at the ends but with a gap between them of nearly 1/8" at mid-length.  When I put the back of the track against the cut edge of the whole sheet, there are no gaps wide enough to accommodate a piece of paper.  Am I correct in concluding that my poor side-by-side fit of a single cut is the result of released tensions in the plywood, or am I not using the saw properly?  All advice from more experienced workers will be appreciated!  Thanks.

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Offline live4ever

  • Posts: 757
Re: Bad cut with TS55 or springing plywood?
« Reply #1 on: March 03, 2018, 10:34 PM »
Welcome!

There are several possibilities, some of which you mention. 

One of the biggest that jumps out to me is that you are connecting guide rails.  It would be very easy to get a slight bow in your cut if the rail is "kinked" at the joint.  Are you using two guide rail connectors, and how are you verifying (if at all) that the rails are connected perfectly in-line? 
Current systainer to productivity ratio:  very high

Offline Untidy Shop

  • Posts: 2632
Re: Bad cut with TS55 or springing plywood?
« Reply #2 on: March 03, 2018, 11:06 PM »
You may be doing this, but to be sure. Leave a slight gap between the rails (they are not always cut 90 degrees to the edge during manufacturing) and set the rails against a straight edge before finally tensioning connector screws.

Also ensure you have a straight alignment of hand, wrist and elbow behind handle when pushing the saw. This should eliminate any sideway preassure from saw to rail.
« Last Edit: March 03, 2018, 11:11 PM by Untidy Shop »
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Offline Ulmus

  • Posts: 9
Re: Bad cut with TS55 or springing plywood?
« Reply #3 on: March 03, 2018, 11:37 PM »
Thanks for the quick replies with good questions.  My new tracks are joined with proper new connectors and spaced about 1mm apart.  They were nicely aligned on their own, but I confirmed that with my 4' level before tightening the screws. Both ends of the track were clamped when I made my cuts.  I may not have been clear enough pointing out that the bow occurs in both sides of the same cut.  Even if I'd made this cut freehand with my jig saw, wouldn't both sides of the same cut match?  I'm still getting the hang of pushing the saw along the track so handle / wrist / arm alignment is certainly something to work on.
« Last Edit: March 03, 2018, 11:54 PM by Ulmus »

Offline fshanno

  • Posts: 949
Re: Bad cut with TS55 or springing plywood?
« Reply #4 on: March 04, 2018, 01:25 AM »
Doesn't surprise me a bit.  The plywood you buy sounds like the plywood I buy here in Texas. 

There's nothing wrong with your saw or your guides or your technique.  You're fine.  You plywood strips are crooking (and probably bowing too) right as the cut is made or soon thereafter.  Try the cut on a table saw with the same material.  You'll get the same crooking and bowing.
 
And it could happen on wider strips than 3 1/2"  I've had 8" wide strips crook a little and bow a lot.  You can't depend on plywood for flatness any more.  They used to make doors out of plywood around here.  Today that would be laughable. 

Neither can you absolutely depend on particle board and MDF.  They are better but they too will bow and crook.  I make concrete counter tops.  I occasionally cut 2" strips of 3/4" melamine for forms.  Those strips frequently have some bow and some crook.



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Offline jobsworth

  • Posts: 4968
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Re: Bad cut with TS55 or springing plywood?
« Reply #5 on: March 04, 2018, 10:26 AM »
I get that issue to. Someone (when someone else posted about this) here once said that it is technique.  When cutting stand behind the saw and make sure you aren't putting pressure causing the saw to tilt to one side or the other.

Is that the cause?
Heck I dunno.

 I get that myself some times.

Even the solid birch timber, I just cut yesterday with my TS 75 that I own and use for mainly hardwoods and thats not  mounted in a CMS module which I dont have.
« Last Edit: March 04, 2018, 10:28 AM by jobsworth »

Offline SS Teach

  • Posts: 285
Re: Bad cut with TS55 or springing plywood?
« Reply #6 on: March 04, 2018, 07:01 PM »
Welcome to FOG. When I connect my two 1400 rails I use a Betterly Straightline Connector. That with Makita rail connectors does the trick. It seems that you always need something more. C’est la vie.
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Offline simonb

  • Posts: 2
Re: Bad cut with TS55 or springing plywood?
« Reply #7 on: March 05, 2018, 03:41 AM »
hey. where are you getting the ply from (and where abouts are you in NZ?)

I find the stuff from P makers etc pretty pathetic. Am down in Christchurch. Even the 'quality' hard wood faced okoume boards, if they dont splinter all over the place, then they relax the way you are describing or even turn like a spiral.

I have an order coming from plytech of euro stuff that I am hoping is going to be the answer. :)

Offline Gregor

  • Posts: 796
Re: Bad cut with TS55 or springing plywood?
« Reply #8 on: March 05, 2018, 04:34 AM »
Even the 'quality' hard wood faced okoume boards, if they dont splinter all over the place, then they relax the way you are describing or even turn like a spiral.
That property of plywood makes me choose multiplex (which should it twist excessively, rare occasion, makes the return trip to the dealer) instead every time.
« Last Edit: March 05, 2018, 04:42 AM by Gregor »

Offline Ulmus

  • Posts: 9
Re: Bad cut with TS55 or springing plywood?
« Reply #9 on: March 07, 2018, 12:15 AM »
Thank you for your insights.  After some more practice, I'll repeat my testing with other materials and report back if I suspect a problem with saw, track, or technique. 

Ironically, I bought my New Zealand pine plywood here in the heart of Douglas fir country, Oregon USA.

Offline Sanderxpander

  • Posts: 127
Re: Bad cut with TS55 or springing plywood?
« Reply #10 on: March 07, 2018, 02:13 AM »
Even the 'quality' hard wood faced okoume boards, if they dont splinter all over the place, then they relax the way you are describing or even turn like a spiral.
That property of plywood makes me choose multiplex (which should it twist excessively, rare occasion, makes the return trip to the dealer) instead every time.
What's the difference between multiplex and plywood? As I understood it it's the same thing, just EU vs US naming conventions.

Offline Gregor

  • Posts: 796
Re: Bad cut with TS55 or springing plywood?
« Reply #11 on: March 07, 2018, 02:58 AM »
What's the difference between multiplex and plywood? As I understood it it's the same thing, just EU vs US naming conventions.
All Plywood is made from a number (minimum of 3) of 90° rotated grain wood layers, with the outsides acting as veneer.

Multiplex (MPX) as a plywood species is made with an uneven (thus grain direction is identical on both faces) number (minimum of 5) of same thickness (incl. the outer veneer ones) layers and starts at 12 mm. Basically it's the highest quality plywood from a stability standpoint (high stiffness, low flexibility), thanks to the even thickness of all layers the forces of the wood cancel themselves out very well, thus it is unlikely to twist/bend.

The differences become visible when looking at crosscuts of different 'plywoods':
Tischlerplatte (only 3 layers, thick single core, this is where it all started), Plywood (imho low quality stuff), Multiplex (the good stuff).
(links to images on Wikipedia)

Possibly what is known in Europe as 'Multiplex' is available in other places under a different (grade) name.
« Last Edit: March 07, 2018, 03:25 AM by Gregor »