Thread: Cannot remove drift on blade

Dengue

Have you checked to see if the blade is parallel to the slot in the table i.e. square in relation to the table. Sometimes the table needs to be adjusted slightly to bring it into square in relation to the blade

Hi Dengue,
Just looking at the Photos, it appears that the Blade is not in the Centre of the Wheel.
You Have the Teeth sticking out over the edge.
Not sure if that will make any Difference, but it may.
I wood like to believe that when you are cutting any wood, that you are bringing down the Support with the Top Guides, so as it just clears the wood.
Of course your Blade is Sharp.
I'm sorry if I'm trying to teach you how to suck eggs.

Good point mat, will check it out tomorrow. Will need a lot of turning to reduce the drift from 15 mm to zero, measured as the differences in distance to the mitre slot, measured along the ends of the table.

Isatree, thanks for your comments. I started out with the blade fully supported, then gradually moved it forward. The photos show the last test which gave the least drift, with the blade as far forward as I dared.

Yes, when doing the tests, the guide was just a centimetre above the test piece.

I tend to agree with Mat. Hopefully with the bolts loosened your table will rotate enough to cancel the drift.

Edit: Also it wouldn't hurt to check that the guides themselves are parallel to the fence. Mine was slightly out, so I removed the blade and clamped a short straight-edge between the guides and checked that it was parallel to the fence. Had to adjust slightly. (Mine's a Hafco 12", though, not a nice Laguna.)

A fun morning in the shed, covered in sweat.

Sorry I didn't explain myself properly above. The standard test for drift and adjusting the fence for drift is to draw a line on a piece of timber, cut through it following the line until it reaches the far end of the table. If there is drift, the piece of timber will be at an angle to the mitre slot. What I was doing was measuring the distance from the angled piece of timber (after cutting) to the mitre slot along both the infeed side of the table and the outfeed side of the table. The distance was greater along the outfeed side of the table by 8mm i.e the timber was angled to the left of the blade line, away from the mitre slot. The angle is calculated as inverse tan (8/400 ) = 1.1 degrees drift. I want it to be zero degrees drift, so that the blade is parallel to the mitre slot, which is how the fence is set too. This is not an unreasonable expectation, as indicated by Alex Snodgrass and Michael Fortune.

I decided to start afresh today, so I removed all the guides, tensioned the 1/2" 3tpi bimetal blade as shown in photo 9 attached, set the blade in the centre of the tyre, removed the cord from the power supply and did some basic checks.

9. blade tension gauge.jpg

1. Rotating the top flywheel by hand, there was an intermittent grating noise, which turned out to be the blade frequently rubbing against the plastic blanking insert block under the table. This rubbing can be seen in Photo 1 attached. The problem is that it was intermittent, hitting several seconds at times while I rotated the upper flywheel by hand one full revolution of the blade. This makes me think something is wrong with the blade tracking. This noise was also intermittently present when I had the guides in place.

1. Insert block.jpg


2. I then decided to measure the amount of blade twist in the horizontal plane by attaching a peg to the blade just below the gullet and turning it, as shown in photos 2 and 3 attached. Over the length of the 50mm peg, the twisting movement of the blade was 2.7mm as I turned the wheel by hand. You can see the travel of the peg shown by the two pencil lines marked on the right side of the insertion plate. This would confirm the blade was twisting and one of the reasons why the blade was hitting the insert block under the table.

2. Peg test.jpg 3. peg test result.jpg

3. The tests which I did yesterday showed the drift of the sawblade relative to the mitre slot. Today I decided to see if the 1/2" blade was parallel to the mitre slot by putting a long steel rule against the blade and measuring the distance from the rule to the mitre slot at each end of the table and determining the difference as an indication to the amount of drift. ( see photos 4, 5 and 6 ) The results varied, but the distances were typically 56 -58mm along the infeed side of the table, to the mitre slot edge, and 62- 64mm from the outfeed side of the i.e the blade was out of parallel with the mitre slot of 8mm over the 400mm table length.

4. parallel blade test _01.jpg 5. parallel blade test _02.jpg 6. parallel blade test _03.jpg

4. I then decided to measure the horizontal deflection of the blade at a point 100mm above the table, as shown in photos 7 and 8. I put a dial gauge on the blade and rotated the blade. The end result was that in one complete turn of the blade, the deflection measured on the dial gauge varied between zero and 0.35mm. Hopefully that will reduce once the guides are applied, otherwise it will be difficult to cut 1mm veneers.

7. Dial gauge setup.jpg 8. horizontal deflection.jpg
I am not sure which of these tests gives significant results. Do any of them give anybody any idea as to why I cannot set the blade drift to zero by tracking the blade on the flywheel? I hope someone out there can help.

Still have to remove the blade and check that the side guides are parallel to the mitre slot, as per Hermits suggestion

I am no bandsaw expert, but I just set up a Laguna 14"SUV and she is running very well.

The issues I struck were:

1. The upper ceramic guides were not parallel to the blade. See this thread to see how this was fixed ... not difficult. https://www.woodworkforums.com/f27/re...nd-saw-180486/
2. Laguna recommends the blade be centred in the top wheel. I did that (using a Re-Saw King blade).
3. Drift was out, but every blade has it's own drift. The way I checked mine was to run a piece of wood along the fence into the blade and then stop the saw (got to love the foot brake). The blade was not square in the slot. After a bit of fiddling the fence was adjusted so the gap either side of the blade was even. Getting this drift adjustment right is mission critical. Now my mitre slots are not quite parallel to the fence, but the blade cuts nice uniform 1.5 mm veneers 200 mm wide with no trouble at all.
4. Fixing the drift was buggery at first. I'd adjust left and then right and so on. Finally I did a dummy spit and ran the saw for about 15 minutes, just in case it needed a little time to bed down wheels etc. After that, the drift adjusted quickly.

The only other thing I can think of from your post is that you may have a crook blade ... perhaps a poor weld. It should not be rubbing anything intermittently. Do you have enough tension?

Hope this helps.

Hmmm... you haven't mentioned it (I think) but have you tried with a different blade?

Just 'cos a blade is sharp does not necessarily mean that it is "right." All it takes is slightly different sharpness or set on one side to t'other, or a "bellied" blade, or... Even brand spanking new blades can be "bad" when it comes to this.

The best bet is to try two or three different blades. Every blade has it's own degree of drift, but if all run out to the same degree when running in the correct spot on the wheels (usually central) then it's obvious the BS needs a few tweaks.

If, on the other hand, they vary widely... well... I'd look at changing your blade supplier/sharpener instead!

Thanks John S and Skew for your valuable and helpful comments. The blade I was using was a fairly new 1/2" 3tpi bimetal blade that I was using on another saw, so got the local blade technician to cut and weld to the new shorter length to suit the Laguna, rather than buying another one. I suspect that there might have been something wrong with it after the re-welding process.

I had a new 3/4" blade 1.3 tpi from Henry Bros, so slipped that on to see if it made a difference. And it did, a big difference, but not without problems. Firstly, the rear of the blade sat on the upper wheel with just about 2 mm of tyre showing at the rear, except for a quarter turn of the flywheel, when there was no tyre showing. The position of the blade on the lower wheel was such that the teeth were way forward, with the points off the tyre and level with the outer surface of the rim. Any suggestions on how to get around this problem, assuming it is a problem? Of course, the blade is still scraping on the plastic inset block under the table, and I don't know how to fix this.

I did the peg test to see if there was any twisting of the blade. Compared to the previous blade of 2.7mm movement over 50mm, there was less than 1mm on each revolution of the flywheel, and this movement coincided with the above problem of the blade being positioned at the very back of the tyre. Any suggestions?

I put the dial gauge on the blade at the bottom of the gullet to measure any horizontal deflection at a point 100mm above the table while the blade was turning. The previous blade gave a variation of zero to 0.35mm. This blade gave a variation of zero to 0.20mm. When I fitted the upper and lower guides, the variation was zero to 0.04mm.

When measuring the parallelism of the blade with the mitre slot, the previous blade gave a maximum variation when measured at the ends of the table of 8mm over 400mm table width. The new blade gave a variation of 2 mm over the same distance, equivalent to 0.30 degrees drift. I think I could live with this. Imagine trying to set the fence to match this angle

So in conclusion, the old blade was the major problem, and the new one a vast improvement, but not without its problems that still remain to be solved.

I know nothing about band saws but I understand the mechanics of everything discussed so far.

Have you checked that there is no deviation in the metal part of both wheels ie: are the wheels perfectly circular and the running edge is parallel to the axle / shaft and has no deviation in one location. Is the rubber part of the wheel perfectly uniform and no deviations as per the wheels. If my logic is valid, this would have an impact on drift.

Dengue,

Based on your posts you know a lot more about band saws than I ever will. Sorry, I don't think I can help.

What bothers me about your notes is the intermittent scraping on the plastic block (my Laguna 14" SUV does not have such a block.) Tough to believe this is the saw. Hard as this is to believe, it sounds like a crook blade ... again.

My saw has a Laguna one inch re-saw blade fitted. It is centred on the top wheel, but the tips of the teeth are just forward of the rubber on the lower wheel, and I am told (on a Laguna video) this is normal.

If you still are not happy with the saw, have a chat with your supplier. My new Laguna 14" SUV is running very well, and will get better when I make up something to maintain constant pressure of the wood on the fence.

Good hunting!

This is my first bandsaw, John S, but i have used my son's Electra Beckum saw and learnt lots off it. But he did all the setting up, and didn't have any of the problems I am having.

Thanks for all your comments and suggestions, they have been invaluable. Can you give us a link to that Laguna video please?

Have a look at the double featherboard from Rockler here. Looks good, but the surface of the workpiece will have to be pretty much dead level with the mitre slot for its whole length to maintain constant pressure against the fence.

I have passed on my problems to Chuck Bender who is in contact with the Laguna designer. Will let you know of any comments I receive. Hopefully there is a solution forthcoming.

Some bandsaw users have a single pressure point just behind the blade to keep things aligned
and, I guess, to prevent drift.

This could be achieved with a a triangular piece of timber with the contact corner rounded.

Have you checked the back of the blade for irregularities?
Some gurus talk about, and demonstrate, taking the back corners off by rounding with a stone
as the saw is running.

Hi Dengy,
When I first got my BS I had all the ususal probs that one could have with a BS, I couldn't cut a straight line at all, first thing I did was get a blade fit for purpose, as I do mostly ripping on wide stuff this was a 1 1/4" 1 tpi from Henry Bros. huge difference, I also did some tune up on the saw and some other big mods, as a start point I checked both wheels were coplanar, I'm not overly fussed on this being perfect but just as long as it's close as I find I do adjust the top wheel at times to get the blade to behave, this is something that seems to vary a bit and it may be things like the pressed metal frames aren't as rigid as the old cast iron, a little bit of variation in the blade tension I wind on, sometimes I think the blade heats up differently and the blade will tend to move either forward or backward as I use the saw, I adjust the top wheel to bring the blade back to where I want it or I may adjust the thrust bearings as I go, I do like to see the blade in the center of the wheels but I dont fuss too much if it's a couple of mm either way, my main objective is to have the blade track so it's just off the thrust bearings top and btm and be able to withdraw a piece of wood without pulling the blade off the wheels, I'm yet to be convinced the btm of the gullet needs to in the center of the wheel to get good performance.

I can't recall what I did with my mitre slot but I set the fence paralell to the blade like you did with the rule against the blade (with guides adjusted upto blade) and have never moved it since, as I use the saw and the blade becomes blunter either of three things will happen, 1. the teeth wear evenly.... as evidenced by things like noise increase, coarser finish (but not always) more likely to follow the grain, harder to push through the work but I am still getting an even width workpiece, 2. uneven wear on teeth.... a) workpiece is coming out thinner which means the right side teeth are blunt, ....b) workpiece is thicker which means the left side teeth are blunt, with a) as much as I try and push the workpiece back onto the fence the blade works against me and with b) the blade will push away from the fence, both a) and b) is where we would adjust for drift, like I say I don't, at this point the blade needs to be sharpened. A sharp blade IMO is top of the list for good BS performance, a lot of the other stuff can be fudged a certain amount.

Pete

Originally Posted by pjt

I'm yet to be convinced the btm of the gullet needs to in the center of the wheel to get good performance. Pete

In fact the Laguna people say (in the assembly instructions) to centre the blade on the top wheel. I did that. It worked.

This is the Laguna video. Rockler Presents Laguna Tools 3000 Series Bandsaws - YouTube

This is the Snodgrass video. Band Saw Clinic with Alex Snodgrass - YouTube

What concerns me about Dengy's machine is the rubbing against the plastic insert. That does not sound right at all.