Fixing bandsaw blade drift?

[ondablade]

Thoughts appreciated!

Having fitted and set up a new US made Timberwolf (supposedly very good - and they do cut very nicely) thin back 1/2 in 3 tpi blade on my Scheppach Basato 5-4 it's drifting badly - by about 25mm in say 400mm relative to the rip fence.

I set the saw up accurately years ago (guided by the Duginske book - coplanar wheels and the like), and it's been very good using the locally available Starrett Blades and the like - no significant drift despite many blade changes. (maybe i've been lucky)

The blade tracks just fine on the wheels, although it has a small kick in it (probably a slight misalignment of the weld in the plane of the blade) - disappointing too.

So far i've tried the stock solution - making sure the tyres are clean and in good nick, offsetting the blade on the top wheel by tilting it, and adjusting the rip fence. Trouble is that while i've one more shot at this left (i'm not quite at the limit on the top wheel), it's starting to look like the two combined won't be enough.

I'm thinking it's send the blade back time (except i won't, as the postage to the US is too much), but is there anything else worth trying?

Thanks

 

[matthewwh]

Hi Ian,

Couple of thoughts, if it's a tapered blade it will need to run a little closer to the front of the tyres - if it's centred it will always want to pull to the right.

If it hasn't been welded properly I would at the very least contact the supplier and tell them. If it's not worth posting back they may just send you a replacement.

 

[eoinsgaff]

One of the best approachs I'm come across was from James Krenov. Its not scientific and probably not the most accurate but it makes up for this in simplicity

Take a piece of wood with a decent straight edge and draw a line parallel to this straight edge. Cut along this line free hand, with the straight edge towards the fence. When you get far enough with the piece of wood to be able to clamp it to the table you can stop cutting.

So, when you cut freehand the line of action compensates for the drift. Theoretically your fence should be now be set up in line with the straight edge to remove this drift.

Eoin

 

[Eric The Viking]

Hi Ian,

Couple of thoughts, if it's a tapered blade it will need to run a little closer to the front of the tyres - if it's centred it will always want to pull to the right.

If it hasn't been welded properly I would at the very least contact the supplier and tell them. If it's not worth posting back they may just send you a replacement.

Matthew's right.

I'd add that, IMHO, Steve Maskery's bandsaw DVDs are excellent, although it looks like you've already got the hang of the adjustment.

It strikes me though that your reported 'kick' at the weld may be a clue:

Tapered bandsaw blades must, by definition, be conical (viewed from one side), which is why they need to run to the front of the wheels. If the weld isn't square to the blade, by which I mean the two ends are not aligned to each other properly in any way front-to-back, the blade could be more conical than it should be, either on the inside or outside side.

A step in the weld makes a spiral, and having an angle in the weld makes it conical. The back guide will stop it coming off, but it will never run well.

I'd take the blade off and try the back of the weld section held against a shiny flat surface, like a glass plate It will double any alignment error, making it easier to see.

 

[ondablade]

Thank you Matthew, turns out you were right. It's now working fine, but it took all the available adjustment. I was starting to think that there wouldn't be enough.

It's cutting straight and parallel to the fence, but it took getting the blade as far forward on the wheel as is possible, and putting the rip fence at max adjustment too.

I'm not sure if that's normal, or if it means the saw might not have enough adjustment for another of the same blades. Guess i could enlarge the fence adjustment holes a bit if needed. Wonder if there's an option to increase the crown on the wheels a bit?

It means that the cross cut fence/mitre gauge isn't much use - lining up as it does off a slot in the table.

The blade is a success. Quiet and quick - the Scheppach saw (being a little lighter than some) certainly likes the thinner/low tension blade. It's just without a bother shaved a 0.35mm thick veneer like strip off the side of a 2in high x 15in long piece of red pine - and held the thickness to well within 0.1mm.

The kick is less than it looked last night - less than 0.5mm measured with a pointer.

I'm not sure what taper is, but the blade is made from thinner stock than i'd used before, and the teeth while not having a lot of set are at 3tpi and with a positive rake/hook are fairly coarse - which one way or the other is going to create a fairly heavy taper like you say.

Thanks

 

[ondablade]

PS to Eoin and Eric. I've been using the freehand cut followed by lining the fence up to the cut method for some time - it works very well.

I'll try a straight surface on the back of the blade weld later Eric.

 

[9fingers]

Ian,

Next time you need a blade try Ian John at Tuffsaws. I've never had a bad one form him and his thin tuffsaw blades are excellent.

Here is one in use - not my video but another forum member Olly also uses them.
http://go2.wordpress.com/?id=725X1342&s ... ess.com%2F

hth

Bob

 

[woodbloke]

Ian,

Next time you need a blade try Ian John at Tuffsaws. I've never had a bad one form him and his thin tuffsaw blades are excellent.

Here is one in use - not my video but another forum member Olly also uses them.
http://go2.wordpress.com/?id=725X1342&s ... ess.com%2F

hth

Bob

Thanks for that Bob...Olly's 'U' tube clip now bookmarked :wink: :wink: - Rob

 

[ondablade]

That's an impressive video all right Bob. I've e-mailed that guy at Tuff as it's the only contact information on the clip. I'll certainly get one to try, especially one of those M42 variety if suitable.

It's kind of good timing actually, in that i'm close to starting to install the ductwork for my dust system (mostly 160mm dia spiral wound galvanised steel round ducting, with a few bits of 100, 125 and 200mm as well) and have been eyeing up the bandsaw with the right blade on as a candidate for cutting it.

The Scheppach Basato 5-4 is strictly speaking not meant for metal cutting, but on the other had i'm thinking i might get away with it with a very fine toothed blade on the lowest speed. It'd be a problem if it was inclined to catch in the thin sheet metal too - but the prospect of fiddling about making 30 or so with snips doesn't appeal and makes a reasonable shot worth a try...

Has anybody done anything like this?

 

[dickm]

I'd be VERY chary of trying to cut ducting with a bandsaw, even with the right blade. Think of the ease with which a round log can catch and turn even if it's in a V-block style of cradle (DAMHIKT). With thin walled tube, I reckon a catch would be almost inevitable.
Not as neat, but an angle grinder, or even a hand-held jigsaw on slow speed with metal-cutting blade would be a lot safer.

 

[9fingers]

I'm with DickM on this one Ian. The old rule of 3 teeth minimum in contact with the work will be impossible to meet with any saw blade on thin ducting.

An angle grinder with one of those new (ish) thin kerf discs like this

http://tinyurl.com/24h4ppv

0.8mm thick will make an easy job.

To mark the pipe, take a piece of newspaper, fold in half such that the crease is longer than the pipe circumference. Wrap round the pipe once and pull tight. The crease will automatically describe a straight line round the pipe. Mark with a felt pen.

Bob

 

[big soft moose]

yeah i'm with **** and bob too - not a good idea

last time I did ducting i cut it with a sabre saw

 

[Eric The Viking]

Apart from a hacksaw blade, there are those nifty-looking wheel-and-chain things for doing exhaust pipes (might be too great a diameter though).

I'd be interested to know what the pro-installers use...

 

[ondablade]

OK. I was thinking it could catch and kick, but then thought that a good heavy pair of gloves and some care would minimise the risk. A bit adventurous i suppose... (better keep my 'responsible' hat on)

The guys who made my ducting told me they normally use a hand held power nibbler. Lindab have a fancy nibbler based cutter and duct rotator here that guarantees a square duct end - scroll down to video 'upgraded SR cutter demonstration' here: http://www.lindab.com/click/videos.htm

The thin disc is the easy option for me to try as i have a small angle grinder, failing that the sabre saw sounds an option.

The weld on the Timberwolf blade Eric is very nicely finished, but it has a definite hollow of maybe 0.3mm or so to the back edge at the joint. Couldn't be sure that it's not just the result of cleaning up the weld (but probably not, as there's no sign of any polishing extending that far as in the case of the sides of the weld) - it seems to extend for about 150mm total but i couldn't get on the edge for far enough beyond that to see what was happening.

Probably explains the minor kick though......

 

[ondablade]

PS I've just ordered a few blades to try out from John at Tuffsaws. He comes across as very knowledgeable, and a really nice lad.

One very positive factor to me is that as a small business he buys his blades in coil form and welds them himself - when the owner is hands on that's got to be a good thing...

 

[Steve Maskery]

Just one thing Ian, have you tracked the BOTTOM wheel properly? If the blade is running off that it may be why you need so much compensation on the top wheel.

You really should be able to get the blade tracked so that it runs true without having to skew the fence to match, although of course, with that blade you are not going to be doing any cross-cutting, are you?

If you do mess with the bottom wheel, just remember to adjust only the top and bottom bolts, the left and right should need no adjustment.

Cheers
Steve

 

[ondablade]

Hi Steve. Not recently, but i did set it up carefully quite a few years ago working from the Mark Duginske band saw book. i.e. using a long straight edge so that the two wheels are coplanar with a tensioned blade on.

Maybe i should go back and do it again just in case something has shifted. That said it was behaving fine on the blade i took off a few days ago.

It's always been a very well behaved saw. I've typically bough stock quality Starrett blades because they were easily available locally, and by and large they didn't drift.

When i saw a clip from your DVD somewhere a few weeks ago showing you demoing on a Basato 5-4 i had to have a copy of that too. At least you didn't disagree with Duginske. (?) Nice material by the way, i'm looking forward to getting into the jigs.

To ask a question. How do you you get on with the Scheppach on deep ripping type cuts with coarse e.g. 3tpi blades? I ask because mine seems to chatter/squeal/vibrate at times. It's as though the load produced by maybe 20 teeth biting at once is too much for the steel chassis, or at least that the load is enough to trigger vibration.

It's a funny saw. Mine has generally been very well behaved and is well made, but it's a bit light in places and falls a bit short of what a fully professional quality machine should be when challenged i think. The experiment with the Timberwolf blades was in an attempt to get over it's limited ability to tension a heavy blade. (they do a high strength thin blade)

I may have mentioned it before, but i'm trying to figure if it might be worth filling the frame with sandbags or even concrete to steady it up! I might even get into fab mode and add some reinforcing.

The alternative is to move it on to somebody not doing heavy work, and take the plunge for an SCM or something like that...

 

[Steve Maskery]

To ask a question. How do you you get on with the Scheppach on deep ripping type cuts with coarse e.g. 3tpi blades? I ask because mine seems to chatter/squeal/vibrate at times. It's as though the load produced by maybe 20 teeth biting at once is too much for the steel chassis, or at least that the load is enough to trigger vibration.

In my DVD the deep ripping is rather slow. I've never had squealing, though. Since then I've got one of Ian's TuffCuts, It's 3tpi but one is a raker, so really only 2tpi, and it cuts like a hot knife through butter. I'm very pleased. Good finish, too.

Cheers
Steve

 

[ondablade]

Thanks for that. I'm serious about the concrete by the way.

He has one of those on the way to me Steve, plus something that'll give a slightly better finish - so maybe that'll get past the issues i'm seeing...

 

[ondablade]

OK, update time. The Tuff blades arrived this morning. V nice looking.

I mounted up the 1/2 x 3tpi M42 for a try out in place of the very similar looking and highly recommended US made 1/2 x 3tpi thin back/low tension item already described.

The Tuff M42 seems significantly better. It tracked square off the centre of the wheels (i.e. cut parallel to the mitre slot). A more aggressive cut with a sharper sound - faster, but actually cleaner. Rock solid, no visible kick or movement whatsoever when running.

I tried re-sawing the same piece of 11 in high red pine that caused so many problems yesterday, this is near to the vertical capacity of the Scheppach.

A flat and straight cut, notably faster than the US item with little or none of the vertical bowing/drift/humping and resonance patterns i got with the latter. It didn't solve the issue high of pitched vibration from the saw chassis however.

Definitely not in the space of full on 16 - 18in industrial weight bandsaws, but probably an option if you don't rush it and overfeed. I guess the remaining question is whether or not this set up would stay in adjustment over a batch of work - heavy workpieces would probably need good support. e.g. a re-saw jig.

Definitely as you say Steve the best option so far on this machine....