Bandsaw accuracy?

[AdeV]

Does anyone have any thoughts on the accuracy of horizontal bandsaws, e.g.



versus a "traditional"(?) upright one such as this:



?

I ask because I have one of the latter type, and it's bloody awful if you're trying to cut, well, anything. E.g. "divided he ad" brought a lump of wood around last weekend that he wanted sawing into planks. We figure the bandsaw would be great at this, but it turned out to be terrible - the end cuts weren't so bad (apart from taking f-o-r-e-v-e-r), but the first horizontal slice and the blade ended up taking a massive belly cut (about 1" fatter in the middle).

So... I'm thinking of getting rid of it & buying a horizontal one instead..... if they're any good.

Also, if they are, would anyone recommend a particular brand? Olde English is my preference, and I've got 3-phase (440v) power, so a decent industrial size machine is the order of the day.

PS: I'd use the hacksaw for most things, but it's got a pool table blocking access at the moment; and I don't need much of an excuse to buy a new tool!

Thanks in advance!

(edit to use a smaller picture)

[Arbalist]

Vertical bandsaws are good for resawing timber into planks within the limit of the saw.

There are so many reasons why you had trouble it's hard to know where to start?!

Worn blade
Wrong size blade
Wrong type of blade
Not enough tension
Poor blade tracking
Guides incorrectly adjusted
Fence adjustment

What model bandsaw do you have and what size/number of teeth blade are you using?

[j1312v]

Hi Adev,

Each one has its own merits, the horizontal bandsaw is great for round/square/flat stock and the vertical is more suitable for cutting plate in irregular shapes and take slices from large stock.
What you need is to have the blade at the right tension, square the blade to the table, proper fencing, etc.

Check

he offers great practical advise/adverts and if you phone he always give good advise...I'm not connected to them other that a casual customer.

Also check Marvel saws on youtube...great bandsaw.

Best,

Joe

P.S.Reposted the link

[AdeV]

Hi Arbalist,

I think you're spot on (I've been doing some reading) with some of your points:
 - The blade is worn (blunt)
 - Not enough tension (I can't set it accurately, so I just set it until it "feels" right
 - Fence... what fence? Had a piece of timber g-clamped to the table...

The blade seems to track OK & the guides seem OK, although I'd not know how to be sure of this.

Can't give you a model just now, the machine is a Startrite similar to the one pictured, the blade is 1/2" and IIRC 10tpi - which is probably way too fine for the job at hand, I try to get blades suitable for cutting metal, which is its usual job.

Also... I think the fact we lubricated one side of the blade & not the other might have had an effect...



Thanks Joe, you wrote that while I was typing this reply, I'll watch that video now (it's got to be more interesting than work!)

[chipenter]

I would keep a blade just for timber a bit like a file for brass wont work very well after using it on steel .

[awemawson]

Blade speed needs to be way higher for wood by a factor of ten from metal.  Teeth per inch needs to be way coarser for wood than metal.

My Startrite - I think it's a 10V - has a knob to pull out to change between two speed ranges which gives the 10x ratio. It also has a gauge built in by the tension knob calibrated in blade width. It also has a spinny disk thing that gives  blade tpi and feet per min for different materials.

Here is a picture of the change pulley chart that I happen to have on the PC

[micktoon]

Hi Ade,
                I agree with the above comments and especially  the blade type and sharpness, for thicker wood I use 3tpi blade and would keep for just wood too, Also I have heard it said by a few wood turners that once you have cut round blanks so been cutting curves you never get a decent straight cut out of that blade again, they keep a separate  blade for straight cuts. These are fellas that have learnt by trial and error after paying good money for timber and spoiling it so there will be truth in it.
  As was mentioned too, you sort of need both horizontal and vertical saws in an ideal world too, or tell the missus that anyway.
 Cheers Mick

[awemawson]

Ade,

A couple of photos I've taken this morning for you - it turns out mine is an 18V10

First the tension gauge nestling between the wheels (I'd be very surprised if yours doesn't have this)

Secondly the TPI / Speed / Thickness calculator

[Arbalist]

Those Startrite saws are fantastic machines although I think they're more aimed at metal working. We had a couple like them where I used to work. You should be able to resaw timber on it with the right blade though and with the machine set to the right speed. Not really my field but at a guess something like a 3/4" blade with 4-6 teeth per inch? The best place I've found to get advice on blades is Tuffsaws.

http://www.tuffsaws.co.uk

Ian is a top bloke for bandsaw blades.

[sparky961]

I was recently tasked with cutting 9" round hard plastic on a medium sized horizontal bandsaw.  One might think this is a very easy task since plastic doesn't offer much resistance to cutting.  One would be wrong.

Initially I tried just making a cut with conservative settings.  Higher blade speed (only "1" and "2" on this saw), low feed rate, coarse pitch brand new blade.  The result was similar to what Ade describes (I think) with a "belly" to the cut instead of being dead straight.  It's hard to imagine how a blade can cut like that but if you think of taking a piece of metal banding/strapping and pushing down on edge, it will bow out to one side or the other.  Even when under extreme tension it has no choice but to do this.  Even with very low feed it will tend to bow a little bit then continue to follow the cut until nearing the end of the cut when the blade tries to get back in line. 

After some research and discussion with others I learned that with a 1" wide blade it's pretty unlikely to be able to cut a 9" diameter piece of soft material.  The cut width is limited to more like 3" or 4" for a straight cut.  With a much wider blade (say 2" or 3") the cut width is increased because of the reduced tendency to bow out to the side when pushed down.

The solution might not quite apply to the original problems described, but is still important and surprising for most to learn.  What worked for me was to make multiple cuts about 1/3 of the way into the material, rotating the material for each cut.  I made 6 in this case, ending up with a hexagon in the middle.  The last cut was completely through.  The partial cuts can be higher feed but the last one needs to be appropriately light.  This got me slices with faces that were very flat. 

Yes, there are some cuts that didn't quite line up but much better than the 1/4" or so dip into the material on  the first few attempts.

As many have already mentioned, lots of factors affect a bandsaw's ability to cut well.  I like to set up a saw so it cuts absolutely square, and can't stand a dull blade or missing sections of teeth.  That way I can make cuts that leave very little stock to be removed by machining.  This is efficient in terms of time and material wastage.  I can honestly say that with a well set-up machine I'm familiar with I can usually cut within 0.015" of my desired dimension on the first try.  A little more time spent getting things right at the saw can save a lot more time at another machine.

[Arbalist]

That's interesting about cutting plastic. I was thinking of chopping up one of my wife's old bowling balls for a few projects but it sounds like I'll have trouble cutting it!

[awemawson]

It's all about having enough room in the gullet of the saw tooth to accommodate the material that's been removed.

[sparky961]

It's all about having enough room in the gullet of the saw tooth to accommodate the material that's been removed.

It's an important element in the equation for sure, but in the scenario I described I was using a blade that would have looked more at home on a meat saw!  I think it was something like 3TPI.  There was plenty of room for chips in those gullets, especially at a very low feed rate.  In my application the coarser pitch actually seemed to make things worse, other settings being alike.

The point to take from this is that the width of the blade (not to be confused with the thickness) affects the rigidity.  Even if you can effectively fit all of the material removed into the gullet, you can't prevent a too-narrow blade from deflecting to the side in the middle of a long cut.  At least, the amount of tension you'd need to put on the blade to do it would be way past the working limit.

[nrml]

I would highly recommend Mark Duginske's 'New Complete Guide to Band Saws'. It is written in a very simple style aimed at students and amateurs, but there is quite a lot of very useful knowledge in it that can only be gained otherwise by years of working on vertical bandsaws. What that guy doesn't know about woodworking  bandsaws isn't worth knowing.

Edit:
If you are looking at buying new blades, I would recommend tuffsaws.co.uk . No connection. Just a satisfied customer. Excellent customer service, Starrett stock and a great choice of sizes & grades. Plus you are supporting a one man UK based business.

[Lew_Merrick_PE]

Ade,

I "resaw" logs all the time for guitar ribs, backs, and soundboards.  (1) A sharp blade that is well set with sufficient gullet is the first key feature to be maintained.  (2) Use the widest blade your saw will handle!  (3) Setting your guide blocks or guide rollers properly (I use a 0.0005 inch thick cigarette paper for this task) is extremely important.  And, (4) use of a fence that "follows the kerf" accurately is also key.

One of the things I do is to set a (pulley system) "drop bag" to pull the piece through the cut.  Once the "line" is set straight, gravity does the rest -- and gravity never gets tired...

[sparky961]

One of the things I do is to set a (pulley system) "drop bag" to pull the piece through the cut.  Once the "line" is set straight, gravity does the rest -- and gravity never gets tired...

I like it!  You reminded me of standing, hunched over the saw, feeding a large log into a very exposed coarse blade.... Safety precautions were observed but your system seems like it would be safer and much less tiring.  I don't suppose you have any pictures of the setup?

[Lew_Merrick_PE]

One of the things I do is to set a (pulley system) "drop bag" to pull the piece through the cut.  Once the "line" is set straight, gravity does the rest -- and gravity never gets tired...

I like it!  You reminded me of standing, hunched over the saw, feeding a large log into a very exposed coarse blade.... Safety precautions were observed but your system seems like it would be safer and much less tiring.  I don't suppose you have any pictures of the setup?

It has been several years since I had it set-up and I am not really "into" the photography thing.  In essence, I have an approximately 6 ft. long fence that fits across the saw table (and provides "input support" and some "output support")  that has a "catch" on it to stop the "driving bridle" that the pulley system attaches to the piece to be cut.  When the "driving bridle" engages the "catch," it moves about 1.5 inches "aft" to clear the blade.  [I have been threatening for something in the 40 year range to put a "motor stop switch" on the "catch" as well, but have never gotten around to making that mod.]  The saw, which started out life as a Delta 14 inch bandsaw, has been modified to a 16 inch depth of cut.

The fence "system" replaces replaces the table and mounts directly on the trunions.  It allows me to install 1 IPS sections to guide the "driving bridle" to assure a good "mate" to the fence.  The "table" that supports the the "fence" was a piece of 1.5 inch thing cast aluminum tooling plate purchased from a "surplus store" (Freightliner, I believe) in the 1960's.  The "cable control" is a pair of 8 foot tall tripods that give me enough "drop" for everything I have needed to rip.

Does that help?

[sparky961]

Does that help?

Indeed it does.  Thanks for clarifying.

[AdeV]

Once again, thanks everyone for the many replies

I bought the bandsaw to do metal - the minimum blade speed is actually a trifle fast for that, although I may try a TCT blade, as I've had great results with TCT chop saw blades in the mill.

I think the main problem is blade tension - Andrew, yes, I have a blade tension guide & it's tensioned to the appropriate blade width, however, I've seen videos now which suggest that these are not necessarily particularly accurate, especially if your blade length isn't the exact manufacturer specified length, and you're supposed to tension it until just before the weld snaps.... quite how one does that without destroying the blade, I'm not entirely sure!

Also, the guides aren't set to within a gnat's of the blade width, so that must be allowing some movement. The backstop's OK.

Next time I'm going to cut anything big, I'll spend some time getting it configured. In the meantime, for slicing thin sheet ali or wood, or cutting 2by2's up, it's just fine.

[Fergus OMore]

Apologies for asking questions which may or may not be pertinent to other people.
I've got a 6 x4" but whilst it is fine for rough cutting, I'd like to know what teeth per inch are recommended for lumps of cast steel. OK, I realise that for tin bashing fine blades are necessary but I'm getting pretty poor results on say 1" or thicker Meehanite.

Digressing further, I've just bought and  a set up an Aldi wood saw at £90 as I have a lot of storm damage after the winter (or the first bit). With two TCT blades, it can't be bad.

So I'd appreciate a few pointers.

My thanks- and apologies

Norman

 

[Divided he ad]

   Just found this.... Sorry for causing so much trouble 


Well at least we all learned sometihng 




Ralph.