Thread: bandsaw mill

Originally Posted by calboy

Hi all
New to milling timber we have 70hp 100mm horizontal cut band saw
just wondering what blade set up is best for hardwood
with thanks mark

Are you asking this because your'e planning to sharpen blades or just buy blades?
Also what sort of wood are you cutting?
I've sharpened about 50 bandsaw mill blades but I still consider myself a novice on blades but here are a few things.

Cooksaws on Youtube, or on their website, have some short basic videos on blade and mill setups that you might find useful

Low TPI is critical for a mill that big.

Then you should look at "hook angles".
Higher hook grabs more wood and so is more self feeding but they also =grabe too much wood and stall. Also they go blunt quicker and the smaller teeth tips are more liable to break.
Unless the mill is absolutely set up right higher hook angles can contribute to greater band drift.
Harder wood seems to work better at lower hook angles , also lower hook angles are more forgiving of mill setup problems.

Set is something that you need to experiment with for yourself. Stock blades usually have less set (reduces stress on the motor) but again if the mill is not setup right then this can lead to greater wandering. A bit more set may minimise a wandering problem but you won't cut as fast.

The key thing here is the mill needs to be set up right - again the Cooksaw videos can help with that.

We've had a lot of problems with the overall set up on our larger mill, it was home made largely from a kit so there was no manual. Late last year the boss bought a small Woodlander mill with an excellent manual and we have been able to utiize some of the mill set up methods from that manual onto the old mill.

After you post a couple more times you should be able to post some pics of the mill - I'd like to see it.

thanks for input BobL
so ill patch some pics in when i figure out how to do
So we have a old 'Dinosaw" mill that is probably 30 years old and has basically been cutting camphour larel which is soft
we got a fair few blades with mill and also dinosaw auto sharpener
blades have been set for 12 degree
we have had varying success with milling the soft camphor went ok but hardwood such as blue gum and red mahogany a bit mixed results wandering has been the biggest problem
we are playing with speed of cut and seem to have found slow is better
we sharpened one of the blades to 7 degree and swapped out a 12 degree blade that was wandering in the red mahogany .The 7 also wondered but we questioning whether the grain in the mahogany is not so willing for bandsawing ( we also split firewood and it doesn't split great)
We have introduced soap to water feed lubricate which does seem to help
We haven't got a setter but may have to look at set's influence on cut
Id have to check TPI but it looks around 1 per inch
We did have bearing collapse in the slave wheel of mill and it doesnt seem 100 % balanced so im not sure how big an effect that would have another bandsaw guy that came and had a look thinks it was acceptable?
I appreciate all feedback with thanks Howie

Originally Posted by calboy

thanks for input BobL
so ill patch some pics in when i figure out how to do

That will be handy.

So we have a old 'Dinosaw" mill that is probably 30 years old and has basically been cutting camphour larel which is soft
we got a fair few blades with mill and also dinosaw auto sharpener
blades have been set for 12 degree
we have had varying success with milling the soft camphor went ok but hardwood such as blue gum and red mahogany a bit mixed results wandering has been the biggest problem.
we are playing with speed of cut and seem to have found slow is better
we sharpened one of the blades to 7 degree and swapped out a 12 degree blade that was wandering in the red mahogany .The 7 also wondered but we questioning whether the grain in the mahogany is not so willing for bandsawing ( we also split firewood and it doesn't split great)

The problem of "wandering blades" is a bit of a black art as there are many factors that contribute to this problem.
I should preface the following by saying that I'm a very part time operator - usually 2-3 times a month although lately its been 2-3 mornings a week.
I've been wrestling on and off with blade wandering on our old mill over a period of about 7 years. It's really frustrating how wandering seems to come and go for no apparent reason and it seemed worse the longer I leave it between milling. The worst was mid last year when I hadn't been milling for more than about 12 months and went back to find the mill hadn't been used in that time and someone had run into it probably with a truck and pushed it off its rails. It took some time to sort the mill out and then the blade was wandering on and off for about 4months before I managed to get it back to cutting straight. We wasted a lot of logs sorting this out and I'm still not convinced I really understand what's going on.

In frustration the Tree lopper I work for bought a new small mill and while we were waiting for it to turn up I managed to get the old mill sort of working.

As far as Hook goes we use 8º for everything because we're mainly milling harder woods (spotted gum, lemon scented gum) but it works ok on softer woods. If we were cutting lots of camphor we'd probably set some bands up at 12º.

We found knots mattered more than grain, although the grain and extra hardness around branch unions also caused wandering. We found a bit more set got us around this problem.

We have introduced soap to water feed lubricate which does seem to help

The small mill has a 10L water tank and into this we add a squirt of dishwashing liquid which seems to be enough to break the surface tension of the water.
As far as the amount of water goes, we use only about a drop per second seems to keep the blade cool enough on the small mill. We can mill dozens of logs with the 10L tank.
The bigger mill uses hardwood blocks as band guides (no bearings) resulting in a lot more friction so we use a lot more water (a slow dribble from a hose) but no detergent.

We haven't got a setter but may have to look at set's influence on cut
Id have to check TPI but it looks around 1 per inch
We did have bearing collapse in the slave wheel of mill and it doesnt seem 100 % balanced so im not sure how big an effect that would have another bandsaw guy that came and had a look thinks it was acceptable?
I appreciate all feedback with thanks Howie

Vibration from unbalanced wheels won't help.
Being able to set your own blades really does make a difference.
If a blade is wandering the first thing I do is check the mill setup, and then I reset the blade and if still no luck I increase the
It's not the best practice way to do things but it's got me out of a tight spot a few times

Our experience is the mills have to be set up as close as possible to perfect to minimise blade wandering.
How far are your teeth away from the wheels?

Our setups

Small mill (1 and 1.33 TPI, 38 mm wide blades)
- cutting section of blade is level with the bed in both directions
- teeth tips are 9-11 mm away from sides of wheels
- guides set with appropriate gaps
- set of 23 - 25 thou
- 25 ft lbs torque on blade tensioner.

Large mill (1 TPI, 50 mm wide blades)
- cutting section of blade is level with the bed in both directions
- teeth gullets are 3-5 mm away from sides of wheels
- Top of following/slave wheel closest to teeth tilted forward about 5mm
- ~5mm down pressure on blade by guide blocks.
- set usually 25-28 thou.
- 20000-25000 psi tension on blade.

I assume you have run a string line beside one of the rails to make sure the bed is straight and reasonably level (it hasn't been mentioned). It doesn't matter what sort of mill you have, the first place to look is the bed. Its also helps to have the mill bedded on some fairly substantial dunnage.

This photo is of the new bed for our mill. It is 75mm river she-oak cross members, which we dried for 5+ years. The top sections are 2.4m, 200*75 hardwood yellowbox & some forrest reds of some description) The end segments are full 2.4m. The center segment is 1.2m & designed to tie together the end segments, and provide greater support in the center of the bed, where the weight is likely to be concentrated. We put 600mm lengthwise supports under there.

Under each of the "under" supports we put 1/2" merbau decking off cuts, so we can blow the sawdust from under the mill, and we don't get a dust compacted IMG20220310143346.jpg& building up under the supports, which will throw our level off

The whole bed is locked down by 50mm angle, bolted to the concrete & the cross members.

When you supply some photos, please pay particular attention so we get a good look at both the guides (so we can see the type) , and the cut pattern that is problematic.

On the lubrication front..
We use a 10 liter water tank with 1 teaspoon of of chainsaw bar oil and 1 tablespoon of dish washing soap per tank which keeps the bar oil dissolved. We run quite a high flow volume & get about 3x logs per tank.
I quite often manually clean the blades. Dirty blades mean heat buildup. Hot blades blunt easily, and blunt blades wander.

The rest of our settings are the same as BobL's smaller mill.

The big mill is outside and connected by a hose.
This mill used have band rollers but currently uses hardwood band guide blocks that provide a constant down pressure on the band to keep it straight and level so there a lot of friction on the band and guide blocks - using no water lets out almost instant smoke - the band also expands and loses tension and one time came off at speed what a firkin mess that made.

Because of this we need to use more water than usual, typically we use water at the rate of ~5L per cut. At this rate the band and blocks stay almost at water temperature. Because the inside of the band constant rubs across the guide blocks no resin build up on that side and we also don't see much on the other side. We could use less water use without over heating the band and blocks but depending in what's been cut resin does start to build up on the other side.
Some logs like Tuart build up resin around the area of the teeth (also on chainsaw chains) which are of course not in contact with the guide blocks. For this I keep a spray bottle of diesel handy and when I've finished cutting that log I spray the band, top and bottom, with the diesel. This soaks through the resin and on the next cut the resin usually sloughs off the blade. If the band has to sit on the mill outside a while before next use this also protects the blade.

We are looking at going back to the rollers on this mill in part so we can use less water.

On the small mill the tyres are standard looking notched V-belts.
On the following wheel the tyre is a V-belt stretched over the wheel.
On the drive wheel the tyre is a much longer belt that as well as serving as the tyre also ingeniously drives the wheel.
The mill instructions say no oil or other lubricants other than water with a squirt of dishwashing liquid or it will damage the belt.
This mill used very little water. The 10L tank lasts for 6- 9 logs. Very little resin builds up on bands with this mill - maybe its because of what we mill?
We've measured the temperature of the band on the inboard and outboard side of the cut with an IR thermometer and it stays surprisingly cool. On a 30º Day the outboard side is 45-50º and the inboard side is 35-40º
The water lab system is connected to the throttle so when the throttle goes about last half way the water starts dribbling onto the blade.

One of the most useful gizmos for measuring levels on these mills is a digital angle finder (DAF).
I have one called a Tiltbox (its like a Wixey DAF) and another called an Empire.
I use the Empire to test the mill rails and bunks are all the same.
It has a dual display so it can be read from the side as well as the top so theres no bending over or laying on the ground to check string lines.
If you are adjusting something you dont have to keep watching the display, you set a reference and the as you adjust it warns you when you are getting close and when you've hit the mark.
The Tiltbox is excellent for checking levels across the blade.
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