bandsaw table square

[sunnybob]

Just changed the blade on the bandsaw, while re checking everything I've noticed the table and blade are slightly out of square. Not the normal lefty righty, but front to back.

The table is very slightly (i mean SLIGHTLY) tipping towards the front. Using an 8" (200mm) square, with the base on the table and touching the lowest tooth, the blade is a half mm out at the top. See, told you it was slight.
But as always, the question is, is it worth undoing all the table clamps and shimming the bolts for a half mm over 200mm length?

 

[Phil Pascoe]

Doubtful it's worth the worry. If it tilted away it would be different - your cut would overshoot the line on the underside.

 

[Rorschach]

As long as its tilted in the manner that yours is I wouldn't worry.

 

[sunnybob]

Phil, its tilted such that the cut will be past the lower line when the visible line is reached.

 

[Rorschach]

Ahh bugger. Sorry I misread. In your case I would shim it.

 

[Steve Maskery]

0.5mm over 200? I wouldn't bother, I really wouldn't. It's a bandsaw, not a CNC machine.
If you are cutting 1" material, that is out by less than the thickness of a human hair.

 

[sunnybob]

Steve, I thought the same, but I'm still an engineer at heart, despite 2 years retired. Its hard to dislodge old habits.
i think its best left alone.

 

[graduate_owner]

Could it be the blade that needs slight adjustment rather than the table? Or perhaps the blade rear thrust bearings?

Just a thought - might save you some work adjusting the table.

K

 

[Phil Pascoe]

Phil, its tilted such that the cut will be past the lower line when the visible line is reached.

Yes, of course - sorry.

 

[sunnybob]

No, the blade is running free and clear of all bearings. Its so small that i dont think I have a thin enough shim to correct it. Looks like manufacturing tolerances.

 

[Lons]

I don't quite understand that. :?:
Apart from it being a miniscule amount am I wrong in thinking that where the blade runs on the crown of the top wheel will tip the blade fractionally forwards or backwards in relation to the table? :?

 

[sunnybob]

Yes, the blade position on the crown will affect the angle. But the important point is that the blade is adjusted properly first, with no sideways movement on the cut. Then the table needs to be squared to the blade, especially side to side, or the cut will be angled. The table needs to be squared every time you change the blade, for that very reason.

 

[Alexam]

Are you able to adjust the blade to the correct psition and still have a 90° front to back and side to side on the table, beause this is what you need for complete accuracy?

 

[CHJ]

....... The table needs to be squared every time you change the blade, .....

This is April the First isn't it?
Best of luck with this one:-

I don't quite understand that. :?:
Apart from it being a miniscule amount am I wrong in thinking that where the blade runs on the crown of the top wheel will tip the blade fractionally forwards or backwards in relation to the table? :?

Precisely.

 

[sunnybob]

I will go back and try to move the blade, but I took a lot of trial cuts to get a consistently straight cut in relation to the fence before checking table square.

As I say, its small enough to not affect my level of skill, but I do try to get things accurate.

 

[CHJ]

If Table is set correctly in the first instance to a Blade Band alignment (not it's direction of cut deviation) and the Fence is set parallel to table slots then any deviation of cut is down to blade tracking and performance, the geometry of the wheel peripheries and the vertical (east-west) track of the blade does not change significantly.


Fore -Aft (north-south ) alignment of blade must be checked when blade is in contact with rear thrust bearings as well as running free if highest accuracy is attempted.

 

[sunnybob]

ok thanks.

 

[woodpig]

As you mentioned earlier you're going to need some pretty thin shim stock to attempt to correct the error. Probably worth getting or making a hole punch as well so you can make thin washers as shims just put in place would be guaranteed to move or fall out if I did it!

 

[Lons]

The table needs to be squared every time you change the blade.

It's already been answered but I would never personally adjust the table once it's been set up, unless I've tilted it to cut an angle.
Tthe blade tracking will change as it wears and depending on the material you cut and whether straight or curved cuts. Adjusting the fence and mitre guage is much quicker if the blade isn't tracking straight anymore.IMO.

I admit I also thought initially an April fool joke but it seems not.

 

[CHJ]

......The blade tracking will change as it wears and depending on the material you cut and whether straight or curved cuts. Adjusting the fence and mitre guage is much quicker if the blade isn't tracking straight anymore.IMO.

Must admit any blade that starts to move off the straight and narrow due to wear is just used up rough cutting log blanks or freehand circles, possibly with a re-sharpen if it will stand it.

If re-sawing and thin slicing is the order of the day I fit a new one because my fence is rather crude on the settings front and is more trouble than its worth to move.