Cutting down the grain with a bandsaw - problem.

[flintandsteel]

I'm having some issues when cutting down / along the grain.
A new loom I'm making has a couple of lap joints.
Table, fence and blade all squared up. Blade guides correctly set( from Bedford Saws for the Elektra Beckum).
End on cut and the cut isn't true. 50x25mm timber. Cutting 50mm
I feel the blade is too fine and the timber moving it off some as the cut isn't vertical.
Solution - less TPI blade?

 

[worn thumbs]

What tpi are you using?I would think you are correct in your diagnosis but more information would be helpful.

 

[Spectric]

Look at post 2 in this thread

https://www.ukworkshop.co.uk/threads/bandsaw-blade-handy-reference.137958/#post-1600088

It gives you the teeth required for the thickness of material.

 

[Sideways]

Ripping 50mm thick, you need a coarse blade capable of clearing stringy, fibrous chips. Softwood can be worse than hardwood for this.
Think 3 or 4 tpi.
For stability, a wider blade helps, probably as wide as your saw is capable of tensioning properly.
The chances are your blade isn't any of these and isn't under enough tension.

Be aware that you can overcompress a bandsaw tension spring. The limit is about 25% of it's length (?) I forget, any more and it won't fully recover it's length afterwards. If the coils are all touching you've certainly gone too far and started damaging it.
DIY bandsaws aren't super strong and can't apply the tension needed by a wide blade. 12 or 13mm wide x 3tpi could be the type of blade to start looking for.

 

[Orraloon]

Anything you need to know about bandsaws this is the guy to Google for answers.
Band Saw Clinic with Alex Snodgrass - YouTube
He has quite a few video clips on line. One of my regrets is I had made most of the mistakes before I was aware of him.
Regards
John

 

[Adam W.]

@flintandsteel

A 3tpi skip tooth blade will have it sorted out quite nicely.

 

[Jacob]

Band saw just isn't the machine for accurate jointing whether across or along the grain. Finish with a chisel?
Table saw better for cross cuts and can be very accurate.

 

[deema]

There are primarily just a few reasons for blade wander:

1. Blade isn’t sharp! Get yourself a high quality blade, just buy from Tuffsaws.
If the blade is blunt it will wander, it’s one of the primary indicators your blade is ready for a change. If it’s a new bandsaw, ditch the blade it came with; it will be rubbish.

2. A duff, but sharp blade. If the set, (bend of the teeth away from the centre line) isn’t consistent and even on either side it will wander. Again buying a blade from Tuffsaws usually eliminates this concern.

3. Blade tension, this is a big issue. Not enough tension and the blade will wander. Most bandsaws are incapable of tensioning up the width of blade the marketing idiots have stated. Typically they can actually tension a HSS blade that 3/4 the width the spec says and about 1/2 the spec for say a M42 blade. @Sideways and I wrote a thread about refinishing a SCM S45 where we detail the technicality of just about every aspect of a bandsaw. I’d recommend a read.

4. Forget all the marketing rubbish about blade guides. They have ABSOLUTELY no effect on cutting straight. I wrote a thread on bandsaw blade guide theory, again worth a read.
If the blade is too fine, ie teeth count too high the gullets of the teeth can’t accommodate the saw dust if you cut too thick stock. When the gullets become full the blade stops cutting effectively and the blade wanders and blunts.

5. Lastly, assuming tracking is correct, the last issue is forcing the stock through the blade. Again this doesn’t allow the teeth to cut properly and the blade wanders and dulls. Another good sign the blade is dull.

 

[flintandsteel]

Thank you all for the valuable input.
I have 2 of these bandsaws but only space for 1 in use. On checking spare blades found a 15mm x 4 TPI so that's this morning's job. Swapping blades on the Beckum is rather a pain.

 

[Jacob]

....
4. Forget all the marketing rubbish about blade guides. They have ABSOLUTELY no effect on cutting straight. I wrote a thread on bandsaw blade guide theory, again worth a read.
.....l.

Interesting. Link?
I see the logic - blade guides only do anything if the blade is going off line, but by then it's too late?

 

[deema]

Here you go, Blade guide theory
https://www.ukworkshop.co.uk/threads/bandsaw-blade-guide-theory.135481/

Tear down of the S45
https://www.ukworkshop.co.uk/threads/scm-minimax-s45-bandsaw-teardown-overhaul.135069/

 

[flintandsteel]

Half sorted with the blade I found but need to order a new one (it came used off the other machine).
OK for a quick test but no more.
Blades, used Bedford Saws in the past. Q?

 

[Sideways]

All the samples in the thread linked from the 3rd post here are from Tuffsaws. They have a good reputation here and Ian is very helpful.
If Bedford Saws are good, please let us know.

 

[Jacob]

Here you go, Blade guide theory
https://www.ukworkshop.co.uk/threads/bandsaw-blade-guide-theory.135481/

Tear down of the S45
https://www.ukworkshop.co.uk/threads/scm-minimax-s45-bandsaw-teardown-overhaul.135069/

Had a quick read ta.
I made new guides from beech for my 352. Made a boxful while I was at it as it is very easy and I thought they might not last. Saves a fortune and still on the first set. Soaked in linseed oil.
The back guides with TC tips are original and have lasted nearly 50 years so far. But I guess they'll need replacing some time this century.

 

[flintandsteel]

BTW This is an Elektra Beckum 315
Got the new 4tpi x 5/8" and setting it up. They didn't have a 3tpi on hand.
Only doing short cuts up to about 2" long in 50 or 90mm Beech.
Read the suggested links and learnt a fair bit as a result.
Is this about right?
Back guides maybe about 0.001 or so off. Side guides backed right off (see how that goes).
Now for tensioning. Don't have any sort of gauge to check that so screwed it up tight (no springs on the 315).
Can I determine tension to any degree with side to side movement? i.e finger pressure

Tested:- Lovely gentle, clean and accurate cut. Square all round and cut thickness to within 0.1mm right off the machine. There's times the 315 will sit unused for a week or 2 then get a days work. Looking forward to that now.

 

[deema]

Now, I’m assuming your of a certain vintage and 0.001 is a thou, not a micron anyway you just want all the guides close but not touching. The old method was so the guide was a cigarette paper away. But anything near us good enough.

Blade tension is IMO the most important. You can make a blade tension meter by just clamping a cheap vernier onto the blade and looking at the extension when you apply tension. There are a number of videos on how to do it.

 

[flintandsteel]

Yup 0.001"
Think I've sussed the tensioning. Will give that a go.
Even got the papers.
Got it, all set
Thank you to everyone

 

[deema]

Yup 0.001"
Think I've sussed the tensioning. Will give that a go.
Very nice the way it is but will bring the guides in - needs to be right as just occasionally I do need to shave the timber a hint.

The guides are just to help prevent blade breakage, they don’t make the cut straight.