What factors affect bandsaw drift?


All of the blurbs I've read which tell how to deal with bandsaw drift tell you to just saw a straight line down a straight piece of wood, stop half-way, and mark the angle on your saw table, and then clamp a fence on the table to that angle, and you're done.Don't forget to tip your waitress and drive safe on your way home everybody!
They make it sound as though you've divined the magic angle for your bandsaw once and for all. I'm surprised they don't tell you to just paint the drift angle right onto the table. In fact, the only time I've heard anyone say that drift angle depends on anything, they said that it depended on the particular blade... and that *all*!
I'm not buying it. So, I gotta ask... in everyone's experience, what of the following factors will, if changed, change the drift angle of your bandsaw:
- Blade width - Blade tension - Feed rate - Hardness of the wood - Thickness of the wood - Grain of the wood - Height of the upper guide above the wood. - Slack in the thrust bearing
I would think that the wood would make a difference, but nobody ever seems to suggest using a similar wood of similar thickness and grain when initially finding the drift angle.
So, what about it? Once I find my drift angle, what can I change without having to go find the angle again. And are there any other factors I've missed?
- Joe
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I had some trouble with my Jet 14" shortly after I bought it. What I did to correct the drift:
1. Remove blade and clean tires (my saw was pretty new - if tires are older, replace) 2. Remove guide blocks and sand to a smooth and square edge 3. Install new blade - making sure that blade is centered on tires 4. Check tension setting - my saw seems to cut straighter with a bit higher tension than specified for the particular blade width 5. Adjust guide blocks - just shy of touching the blade on the sides, and just behind the teeth 6. Set thrust bearing so that even the slightest pressure on the blade will cause the bearing to spin.
After doing all of this, the saw cuts pretty much dead on straight.
I'd say the two most important things to look at are centering the blade on the tire and properly adjusting the guide blocks/bearings. (assuming the blade is in decent condition)
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I've got an 18" Jet band saw and haven't experienced this problem. I don't know it it's inherent to this saw or if I simply have a knack for installing blades... I don't do anything special while installing blades, it's all done by eye and feel. I don't have a problem with the Jet brand blades nor with Timberwolf blades. I haven't tried other brands so I cannot rule out blades as the problem for others.
John
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IMHO the quality of your saw lends a big hand in elimilating many adjustments that have to be dead on.
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Snip

I commented on Andy's similar question after you posted this. When you have your fence set up to compensate for drift on a particular blade it is set up only for that blade and that tension. Depending on the sharpness, quality, blade size, and BS tension settings another blade may require difference fence settings to compensate for drift. Drift can be caused by the blade or the BS it self.

On my old Craftsman saw, Yes. On my new Laguna, VERY little to no change.

My old saw, Absolutely My new saw, none so far.

Old saw, yes New saw, no signs yet.

Old, I don't recall. New, no change.

Old, yes New, resawing through 11", No.

Old, don"t recall. New, so far with sharp blades, No.

Old, Yes. New, makes no difference

Old, Yes. New, No.

If you tried everything, perhaps a new saw will be required to remedy the problem. Remember, a lot of factors come into play that differ with each blade. IMHO the more rock solid the saw is the less you will have to tweek blade tension and for each individual blade.
And are there any other

Blade quality? Blade sharpness? Band saw build quality?
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On 18 Aug 2006 02:47:48 -0700, snipped-for-privacy@emenaker.com wrote:
Others will be more scientific, I'm sure, but in my experience, blade sharpness or lack of is the #1 cause of drift, assuming that the saw is set up correctly..
My cheapy Ridgid cuts the same angle with 3/8" or 3/4" blade and only drifts if the blade is dull or not tensioned properly...
OTOH, I might have accidently bought the one BS that Ridgid made right.. *lol*

Mac
https://home.comcast.net/~mac.davis https://home.comcast.net/~mac.davis/wood_stuff.htm
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wrote:

Mac, I got it's twin then! Mine's exactly the same way as yours.
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Hey Chris, you nailed it! I never thought about twist being a result of the wheels! Thank you!
One thing that has helped me to adjust my saw is turn the wheels by hand while looking straight down from above on the blade. Watch the blade leave the upper wheel and travel down through the blocks. I have found that if I only adjust the blocks from the front, the blade will actually be "tweaked" just a tiny bit when looking down from the top.
II
Tim Taylor wrote:

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It is the tooth set of the blade that contributes the most to blade drift. Sharpness will have some influence but the largest contributor is set.
Drift can be overpowered by blade tension and bearing/block adjustments and the use of other gizmos. But why bother - set the saw tension correctly for the blade and just adjust for the drift and go back to work!
Dave
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snipped-for-privacy@emenaker.com wrote:

I'm surprised that nobody has pointed out the fact that you can *adjust* your drift angle.
The tire is crowned, so depending on where the blade rides on the tire it can be made to angle one way or the other. By adjusting the blade tracking you can compensate for any drift.
On some scrap, draw a series of straight lines parallel to one of the sides.
Freehand cut a couple inches along the first line then turn off the saw. This will give you your drift angle.
Now adjust the tracking. Bringing the blade towards the operator will tend to twist it clockwise.
Now cut a few more inches and check the effect of your adjustment.
A few iterations of this and you should be able to get rid of the drift.
Chris
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wrote:

Chris,
You win the cigar. You are absolutely correct.
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that the crown is there so that the blade will track in the same place. The blade naturally tries to ride along the highest point of the tire. Additionally, many band saw tires have very little crown at all.
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articles I've read say the same thing.
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correct. ;~)
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welcome to the world of proper tracking.. *g* Mac
https://home.comcast.net/~mac.davis https://home.comcast.net/~mac.davis/wood_stuff.htm
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I also have the Ridgid, with riser. It's no more cheapie than any other chaiwanese saw. Yes I still dream of a laguna some day.
Tune it up (Duginske's bandsaw book). I didn't get wheels completely coplanar - they were close and futzing with washers wasn't worth it.
Biggest improvement. Spend the $ for a good blade. I have a timberwolf 1/2" 3tpi blade. And, per Timberwolf instructions, low tension (it happens to be 1/2 turn past the 3/8" mark on my saw). It cuts "straight enough". What that means is, using the curved fence (like Duginske suggests), given the relatively slow feed rate (if I want to rip lumber, I'll use the TS, which is faaaar faster), I can resaw lumber and it 'cuts the line'. I just resawed many feed of 8/4 cherry for bookmatched cabinet drawers and no wandering or bow or drift. I've also cut 1/8" veneers, ready for the drum sander, this way. If I need to cut 1/32" veneers maybe I'll sweat it.
Like others have said, when drift appears, my experience is the blades are getting dull. I use these blades for rough work like bowl blank cutting. I use my new blades for furniture work like resawing where tolerances are more important.
I'd suggest that after you align your saw and get a good blade, you follow my other hobby's maxim. "Relax. Don't worry. Have a homebrew." After the power tools are off, of course.
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Top five:
1. Blade 2. Blade 3. Blade 4. Blade 5. Blade
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Yes, indeed! To confirm this try stretching an elastic band between index finger and thumb and the pressing an edge.
What happens?
Of course the harder you press, the greater the deflection.
Jeff G
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Jeff Gorman, West Yorkshire, UK
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