Topic: I'm intrigued! (Read 6430 times)

Corposant · « **on:** March 22, 2012, 08:19:58 pm »

The other day I was sawing through a small (12 x 30mm) block of ABS using a razor saw with a 0.3mm blade. I had made one cut without any problems but when trying to make another, the blade suddenly buckled - without any apparent reason. It wasn't hot but had developed nine splits, all about 2mm long, along the cutting edge.

I must point out that I inherited the saw from my dad, who popped off about twenty years ago - so, like me, it's getting on a bit! My assumption is that it is simply metal fatigue, but the suddenness took me by surprise. As the teeth have no set, I had been frequently wiping the swarf from the blade with my fingers, so I would have felt the splits if they had developed progressively.

Mike

Tug-Kenny RIP · « **Reply #1 on:** March 22, 2012, 08:50:19 pm »

Hi Mike

You have answered your own question.

All teeth must be off-set to allow for swarf removal otherwise the rest of saw above the cut will jam in the groove.

Hope this helps

Ken

Norseman · « **Reply #2 on:** March 22, 2012, 09:08:09 pm »

The first point of fracture allows greater lateral movement along the length of the blade
which results in fractures at other fatigued areas. There was a rail disaster very similar.

I still have my great great grandfathers saw (shipwright) - it was shortened about forty
years ago - every now and then I still use it. My lad will just bin it when I'm gone - lives
for today with no sense of connection to the past.

Dave

Shipmate60 · « **Reply #3 on:** March 22, 2012, 09:27:53 pm »

A razor saw doesn't have an offset to allow a thinner cut.
The teeth carry away the swarf.
It does look like the blade has bent under cutting and the work hardened blade has fractured on the bend.
Like most of us old age does make blades much "stiffer" and susceptible to fractures.

Bob

Corposant · « **Reply #4 on:** March 22, 2012, 09:38:32 pm »

Ken

Yes, I appreciated it was metal fatigue but it was the suddenness and series of splits which surprised me. I think Dave has hit the nail on the head by pointing out the cascade effect.

About setting the teeth - we are talking razor saw here, 0.3mm thick and 48 tpi.

My setting tool might struggle, so I'll send the next blade to you to set for me! - but thanks for your response.

Dave

Thanks for your response too. It always amazes me that bandsaw blades last as long as they do. Talking of old tools, I too have quite a few very old ones and often wonder why it is they stay sharper much longer than modern ones - built in obsolescence perhaps!

Mike

Tug-Kenny RIP · « **Reply #5 on:** March 22, 2012, 09:51:24 pm »

You could try these new Japanese saws which you Pull through for the cut. It lets the teeth do the work and as Bob says, collects the swarf.

ken

Corposant · « **Reply #6 on:** March 22, 2012, 10:13:43 pm »

Bob

Yes the blade has certainly had a hard life - and although not visibly bent, this was due to it's resilience! On the occasion of it's demise, however, I was not deviating from the straight and narrow. I think it just decided that then was the time to give up the ghost - it had certainly had a good innings!

Thanks for your comments.

Ken

An interesting thought - I'll see if I can find one of the razor variety.

Thanks again.

Mike

RAAArtyGunner · « **Reply #7 on:** March 22, 2012, 10:34:53 pm »

Quote from: Corposant on March 22, 2012, 09:38:32 pm

Ken

Dave

Thanks for your response too. It always amazes me that bandsaw blades last as long as they do. Talking of old tools, I too have quite a few very old ones and often wonder why it is they stay sharper much longer than modern ones - built in obsolescence perhaps!

Mike

Probably because, better quality materials, better production control, was used in those days resulting in a lasting durable 'tool'

tobyker · « **Reply #8 on:** March 22, 2012, 11:05:29 pm »

I've given up on razor saws now - I use the 6" blade japanese-type ones. The man I get them from also does a great mitre guide whch you hold against the work and dos 90 and 45 degree cuts - it even comes with a dummy blade so you can line it up precisely before you start cutting!

Corposant · « **Reply #9 on:** March 22, 2012, 11:23:45 pm »

Raaartygunner

I'm sure you're right. Another factor has to be labour costs - this country (and Australia!) in the past has produced top quality products but (as has been pointed out previously, in another thread) the buying public will always go for the cheaper imports, which means that local firms lose trade and go under.

Mike

Corposant · « **Reply #10 on:** March 22, 2012, 11:30:24 pm »

Tobyker

Thanks for that - I'll have a scout around!

Mike

essex2visuvesi · « **Reply #11 on:** March 23, 2012, 07:24:55 am »

Quote from: tobyker on March 22, 2012, 11:05:29 pm

I've given up on razor saws now - I use the 6" blade japanese-type ones. The man I get them from also does a great mitre guide whch you hold against the work and dos 90 and 45 degree cuts - it even comes with a dummy blade so you can line it up precisely before you start cutting!

Can you post up a link or soemthing... Im curious as to what these saws are

RAAArtyGunner · « **Reply #12 on:** March 23, 2012, 10:27:35 am »

Some japanese saws here may be the same

http://www.leevalley.com/us/wood/page.aspx?p=58686&cat=1,42884

essex2visuvesi · « **Reply #13 on:** March 23, 2012, 11:33:52 am »

very nice... with a price to match, but they do look rather nice

derekwarner · « **Reply #14 on:** March 23, 2012, 09:45:59 pm »

& Mike says.... "I too have quite a few very old ones and often wonder why it is they stay sharper much longer than modern ones"...& raaartygunner notes ....."better quality materials"
Well today we have computer controlled

vacuum degassing heat treatment ovens & should be able to produce optimal steels & alloys ........they certainly do for military applications.......

One of our members mentioned some time back of inheriting their grandfathers chisle set that had be ground so many times thay were 1/2 the original length....but when sharpened were superior to any new chisel

It is all to do with the alloying in the melt & the superior heat treatment that follows.....

........Derek

If anyone has a few spare days.......a visit to Perth in OZ would be well spent........
_________________________________________________________________________________________________________________
Hi Derek,

ThyssenKrupp VDM Australia and The Nickel Institute cordially invite you to attend our High Performance Alloys - Corrosion and Welding Workshop.

When Tuesday 17 April 2012
Time 9.00am - 3.30pm
Where Auditorium, Engineers Australia, 712 Murray Street, West Perth WA 6005

About the Workshop
High performance alloys are required for corrosive and high temperature environments and, while iron and chromium based stainless steels can provide satisfactory service in many environments, very high temperature or reducing conditions require the use of nickel-based alloys. Other corrosive environments may require the use of titanium or zirconium alloys. This seminar provides an introduction to the selection and use of these high performance materials.

tobyker · « **Reply #15 on:** March 24, 2012, 07:48:39 pm »

I get mine from this chap - www.woodworkprojects.co.uk - he is really helpful and when he delivered short on one order he put an extra freebie blade in when making it up. Check out the magic handle with a weight in that slides to and fro and blows the sawdust away! The saws are really good - I have some small ones for model work and also the double-edged rip and cross cut for larger carpentry.

Corposant · « **Reply #16 on:** March 24, 2012, 10:33:57 pm »

Tobyker

Thanks again - looks most interesting.

Mike

dodgy geezer · « **Reply #17 on:** July 12, 2012, 11:33:26 pm »

Quote from: Corposant on March 22, 2012, 09:38:32 pm

Thanks for your response too. It always amazes me that bandsaw blades last as long as they do. Talking of old tools, I too have quite a few very old ones and often wonder why it is they stay sharper much longer than modern ones - built in obsolescence perhaps!

Probably because the tool quality varied, and the best ones are the only ones that people kept.

A bit like old bridges, really. You look at the existing ones and think "How strong they made them in those days". What you don't see are the ones that fell down.....

Corposant · « **Reply #18 on:** July 13, 2012, 10:55:22 am »

I take your point - a very good one! You must be thinking of the Tay bridge!

Mike

Norseman · « **Reply #19 on:** July 13, 2012, 08:42:20 pm »

It would be interesting to see how many modern concrete structures stand the test of time.

Dave

Colin Bishop · « **Reply #20 on:** July 13, 2012, 08:54:18 pm »

Quote

It would be interesting to see how many modern concrete structures stand the test of time.

Well, the Roman concrete structures have done pretty well.

Norseman · « **Reply #21 on:** July 13, 2012, 09:01:15 pm »

Yes Colin they absolutely have, but I did say 'modern'.

Dave

Colin Bishop · « **Reply #22 on:** July 13, 2012, 09:33:06 pm »

Well, they are quite modern by some standards. The stuff I'm interested in goes back to 3,500 BC!

More recent concrete structures should be OK unless the water gets into the metal reinforcement causing spalling - or of cource ist athe dreaded calcium chloride issue which affected buildings back in the 1970s.

Colin

News:

Author Topic: I'm intrigued! (Read 6430 times)