I just learned something regarding blade tension!

[OzarkSawdust]

On 11/9/2019 at 4:33 PM, Sycamore67 said:

The question remains about retensioning.  If the blade returns to the original length as Jim suggests, then you would not need to re-tension.

The coefficient of thermal expansion is 0.0000072.  So you would multiply the blade length by the temperature (C)increase times the coefficient to get the expansion.  Even if the blade temperature reaches 500 F. The expansion of a 5" blade is only about 0.018" .

I think that in some conditions of you are pushing your wood hard you could deform the blade.  Or a bit of blade slip in the clamp could cause issues.  I just have not been able to measure or see any increase in blade length.  I am hoping that others will try to measure.

No matter if it is stretch or clamp slipoage, losing blade tension is an issue.

The skin temperatures of the SST were not too extreme compared to the SR72 Blackbird.  It leaked fuel until the plane got hit enough to expand and seal the tanks

Oh Heck...you didn't tell me this hobby required math!! 

Edited November 16, 2019 by OzarkSawdust

[NC Scroller]

I am of the school that the blade did not stretch. If the blade did stretch you are talking a micron or less.  A micron is .00003937007874015748".  Too small to detect with the human eye and too small to affect the tension.  Easy to prove.  Take the used blade and compare to a new unused one.  I am thinking there was a slippage in the clamp or there is too much play in the bearing where the clamps (top or bottom or both) attaches to the arms.

[Scrappile]

I have to agree with NC Scroller.  Just my opinion, I have nothing to back it, but, to stretch the blade, I think you would break the tension lever first.  The one exception to that may be a spiral blade.  The it is not really stretching the blade, it may tighten the twist of the blade a little.  Again not proof just my opinion and sometimes my opinion gets twisted.

Edited November 16, 2019 by Scrappile

[JimErn]

Might be slippage in the clamp, if it is, then that must rough up the blade cause when you re-tighten it that seems to fix the "slippage"

I sand the blade before using it, seems that would do it, but sometimes I get the slippage/stretch

No matter what you call it, when you release the tension and the blade bows, that is a problem and that is why I run the saw for 30 seconds or so and then release the tension to check

[kmmcrafts]

I'm quite certain as I said before.. that it's slop in the bearings.. How about you guys try something..  Put the blade in.. apply tension.. release the tension and clamp the blade again and re tension the blade again before you even run the saw at all.. This is my method and I don't get stretch or whatever you want to call it when I do this.. My hands are already there and it's only a second more to re-do the clamping each time you move the blade.. No need for me to run the saw for a few seconds.. This is why I stand behind my theory of the slop in all of the pivot points on this type of saws.. Used to have to do the same thing on my DeWalt.. Never had to do this on any of the 3 Hawks or any of the older saws I've owned that I believe I mentioned in another replay on this thread.. 

If you look closely at the upper arm as you apply tension to the blade.. you can see it move / pull down.. I'm not saying it's for sure a bearing slop issue.. It may be the upper arm slop issue and it's not coming all the way down to it's resting point until it is forced to when you initially apply the tension.. Whatever it is.. it only seems to be an issue with these Ex and like saws.. If it were a blade issue.. it'd do it on all saws I would think..