Made a boo boo - restoring old saw.

[CroppyBoy1798]

Howdy!

Ok, so today I finally decided to tackle an old saw that was given to me a few years back by a neighbour, the saw was originally her fathers who died many many years back, so the saw is at least 80 year old or so, possibly more. Its a cross cut saw marked 'Warranted Superior' has a 26" tapered blade and 7tpi. Unfortunately during its life it was badly re sharpened (different size teeth, some missing) and the handle was ate alive by woodworm!

Its been hanging in the shop for a few years and today I got it down to 'bring her back to life'! Stripped it down, sanded the blade and came up with a rather dandy improved jig to grind down all the teeth and give me a fresh (and level) surface to work off and cut my own teeth!

So, made the jig (an angle grinder with a grinding disc thats fitted to a block of timber that passes up and down by a fence removing very slight amounts from the blade which is held secure). The thing is on perhaps one of the final passes I may have taken off too much in one go and 'hardened' the metal? The edge turned a mild shade of blue and the file wont cut into the metal, it just glides on it, in fact, I think trying to cut teeth with the file is blunting it!!

Is there anything I can do to get the metal somewhat soft again? I know its no great loss but I was really hoping to cut and set the saw as well as making a new handle and get her back to some sort of working condition and am feeling pretty dissapointed now that I bunched it up!

[Pete Maddex]

Hi,

If you have hardened the blade then grinding will get through the hardened layer, but you will run the chance of re-hardening the steel. You should have filed the teeth off or just topped them and sharpened the saw.

Check out saw sharpening on the web.


Pete
_________________
Pete, Mad Bad and Dangerous to Know
It doesn't have to scream to cut wood

[EdK]

Might be worth getting a longish flat file, take the handle off. Then get a scrap bit of wood and cut a slot in it so that the side of the file fits in - this should give you a file with a reference fence at 90 degrees. You should be able to take the metal down without heating it up then.
Then back tot he saw file for sharpening it.... I found that a bubble level (just the bubble - size of a coin type thing - axminster sell them etc) helps with keeping the saw file correct....
Ed
(edit - yer what Pete said ! Ooops double post of something - prob my slow typing...)

[studders]

edit

[Richard T]

From your description of how this area got hardened, I can't think what could have happened. As good, old saws are made of tool steel that is tough but not hardened; tool steel that may be hardened by getting it red hot then quenching it, and usually may be normalised again by getting it red hot and allowing it to cool slowly.
A general rule of thumb is to heat the steel (slowly) until it becomes non magnetic. Usually this happens when it appears cherry red. The molecules are wizzing around in all directions and the longer it takes for them to slow down, the more time they will have to settle down in a more relaxed manner and the softer the steel will be.
Also they will settle down more evenly if the blade is held pointing north/south while it is cooling.

[CroppyBoy1798]

Hi all, thanks for the replies and help!

It would have taken me agesss to file the teeth down to a level surface as they were everyway, plus there was a few missing so I had to at least take it down to the level of these, plus, what I forgot to mention initially was that there was also a small crack, I was humming and hawing and decided to take it down to the base of this crack thus eliminating it.

[img][/img]
The saw (you can see where the crack is, a slightly light patch a few inches from the tip of the saw.

[img][/img]
The offending saw ruining maching of mine.........wish I hadnt bothered now. But, I'll persist!

[mr grimsdale]

Thin metal (plane blades too) and power grindstones (of the sparky sort) are problematic. Too easy to overheat. The only thing you can do is another machine pass - but slowly, with cooling water sprayed on.

Not a valuable saw. Spear & Jackson? Quality would be OK, so worth sharpening, for use if not collecting, if not too rusty.
But I wouldn't lose any sleep over it - just see it as a learning curve. If you can't get it sorted just bin it and have another go on another cheapy. In fact it's a good idea to get your practice in on a bit of junk, rather than spoiling something costing more than a fiver!
Potentially very satisfying if you get a bit of junk nice n sharp and working well.
You can get saws like that for a fiver or less, on ebay or car boot.
_________________
http://owdman.co.uk
http://woodchat.co.uk

[Pete Maddex]

Hi,

Don't bin it make lots of card scraper from it, then it will still have a life.


Pete
_________________
Pete, Mad Bad and Dangerous to Know
It doesn't have to scream to cut wood

[bugbear]

Unless you're very attached to it, I'd buy another saw or two at a car boot to work on.

The vast majority of people see no value in handsaws, and good ones (in some cases VERY good ones) can be had for 2-5 pounds.

It's easy (and cheap!) to buy the best, or something damn close to it.

BugBear
_________________
Grinding, sharpening and polishing are really very interesting operations.
...William Henry Bragg

[mr grimsdale]

CroppyBoy1798. I just noticed your name.
Reminded me of one of the most interesting jobs I did, in Castlebar, Co. Mayo.
It was replacement windows in an old house which had been occupied by the french in 98 after the famous Castlebar races. The sash windows had been paid for by the French as war reparations some time later, as they had messed the house up a bit and it belonged to planted English.
So nearly 200 years later I was copying and replacing these same sash windows. They were very high quality, they'd obviously cranked up the spec to get the most from the french!

Part of the reparations involved the return of french prisoners of war. No reparations or returning for the Irish who were slaughtered by Cornwallis at Ballinalee and other places.
_________________
http://owdman.co.uk
http://woodchat.co.uk

[CroppyBoy1798]

Success!!

Was setting up the apparatus of saw death this evening to see if I could grind beyond the 'hardened' section when my neighbour (a jack of all trades) turned up. He immediately suggested trying a stainless steel cutting disc in the grinder, which, lucky he had to hand! Instead of grinding, he suggested cutting the blade.

So, set up the jig, ran the angle grinder across it and it cut it like a hot knife through butter!! and didnt harden the new edge!

I've decided to go with an 8TPI cross cut......have a dozen or so teeth cut already! Gonna take a while on a 26" blade!!

Cheers for the help and suggestions again!


mr grimsdale, sounded like a nice job you did, its great to work on something that you have a personal connection to, or, you know the history of! Bloody French anyway, we were probably better off having been rid of them anyway!

[mr grimsdale]

[LocalOak]

A bit off topic but I saw this quote and thought what?????

"Also they will settle down more evenly if the blade is held pointing north/south while it is cooling."

Surely on the molecular scale the thickness of the blade is going to be just as enormous as the length of the blade. I can't see how aligning the blade north south is going to do anything at all, the grain structure is going to be far smaller than the thickness of the blade and any grain structure that is the entire thickness of the blade is surely going to weaken it?

Furthermore, the Earth's magnetic field is really weak, think how small and light the needle of a compass blade is to be influenced by it. I can't see how such a weak field can have anything but an almost negligible effect on the orientation of atoms or grains in annealing steel.

The atoms themselves do have a polarity and act like little magnets, and can be aligned in a magnetic field. However, the strength of magnetic field required to align them is many many fold greater than the strength of the Earth's magnetic field.

Unless I'm really missing something surely this is some sort of old wives tale?

Am I wrong?

[Vann]

[CroppyBoy1798]

A wind up?! pineapple sake, I've been onto Ordnance Survey Ireland to find out the true N/S line, didnt want to mess up my blade again!!




[img][/img]

Well I've spent the last 5 hours or so stooped over the blade cutting new teeth! (Wish it was as easy to make new teeth for myself!! ). 8 teeth per inch on a 26" long blade........you do the maths! . Leveled the teeth, then trimmed then before setting the teeth. Hopefully I'll get the final sharpening done tomorrow, the tough bit, with the angles and all and get the handle made. I have an old drawer front, 1" thick that came from an old unit thats about 60-80 year old, so, I think it'd be fitting to use that, not sure if its teak or man-hogg-any, would either of these timbers be suitable as a saw handle?


Mr grimsdale, as far as I could see the French had no interest in Ireland rather than militarily, ie a back door to England. The French werent all that well regarded in countrys they helped liberate and theres little to suggest they would have been any different here. We'd only have gotten rid of one regime to replace it with another [/img]