Do you detension your bandsaw blade?

[RogerS]

I've read somewhere (think it was in a magazine article about how to tune your bandsaw) that it's not a good idea to continually cycle your bandsaw blade through a tension/detension cycle. But the decision might also have been linked to whether or not the framework can stand contant blade tension..???

What do members do?

 

[devonwoody]

Since installing the M42 type blade I release after every cut unless using agian after some fence adjustment.

The reason for me is that the M42 blade is so firm it does not need fine tuning to perform straight and decent cuts , therefore there is no time lost in turning up the tension wheel as long as it is tight. Also being a very robust blade it would put a strain on the bandsaw bearings if left long periods at full stretch perhaps.

 

[SVB]

I don't through laziness only. The adjustment on my B/S is via a fine pitched screw with raised the top wheel (as are most I think) but the knob is level with the top of the casing (knuckles do come into play!) and there is no quick release / reset.

However, if it was easy and has a Q/R then I would as I am a little concerned of the effect on the rubber tyre when it is not used for extended periods.

 

[Johnboy]

I don't 'cos I didn't know you were supposed to. This is a quote from the Stiles and Bates website on their bandsaw blades.
"It is worth mentioning that about two years ago, we threw the book away and stopped taking the tension off the blades at the end of the day.
Apart from on the 4in. bandsaws, we haven’t taken the tension off a narrow blade since early in 2002 (except for changing blades of course!) and we reckon our breakages have been reduced considerably. We put it down to keeping the blade under steady pressure."

Link to the site http://www.stilesandbates.co.uk/shop/showmproduct.cfm?pid=373

John

 

[Scrit]

The flip side to that argument is that fabricated bandsaws (i.e. the majority) will tend to bend over time if a wide blade is left on at full tension all the time - that's according to a Centauro rep I spoke to on Woodmex many years back.

If you have a 1-1/4in thick-back TCT blade (like our resaw blade) on the bandsaw that can put sufficient tension on the frame to distort it over time if fully tensioned. Distortion is much less likely to occur with cast-iron bandsaws like the Wadkin BZB or White SH, for example. Maybe a point to make here is that almost all small bandsaws are physically incapable of exerting the ideal tension specified by the blade manufacturers to achieve the optimum beam strength - all the tension gauges I've ever seen on saws are all but useless (that includes my two bandsaws both of which are "highly optimistic") which is why I use a Starrett blade tension gauge. And the amount of tension you are putting the frame under will also vary depending on the width and thickness of the blade. But think the biggest argument against leaving the tension on all the time is that it does tend to cause flats (or for very narrow blades, grooves) on the tyres in the long term. If you have never bought a secondhand bandsaw you may never have seen this.

If you look at the structure of a blade there is a harder more brittle section of the blade at the weld and this will be much more likely to break in use than the rest if the blade. The brittleness of the weld becomes more of a problem on smaller bandsaw wheels as the blade flexes and straightens more times every minute of operation than on a big saw. My experience of small saws (14inches and below) versus larger ones (i.e. 20in and above) is that you get more breakages on small saws.

Incidentally I tend to turn the tension down at the end of the day, but I don't get many breakages (last one more than 3 years ago - never had a bimetallic, stellite or TCT blade break yet - only carbon steel).

Scrit