Re-filling saw profiles

[Jelly]

A while ago I bought a job lot of Tyzak Sons and Turner saws, the seller had however had them all machine sharpened as ripsaws, so I want to change some over to crosscut; specifically a 26" 7 tpi handsaw, and a 14" 10tpi mitre saw.

I'm ok sharpening saws, if I take my time and concentrate; but from what I know, changing the profile is a more involved process... I do rather like the saws in general, but I don't need 3 identical ripsaws and a rip-cut mitre saw is altogether a bit silly (though I suppose I'll regret changing it should I ever want to make increadibly large dovetails!) so I don't want to make a pigs ear of the job.

As a collolary, I'd like to change the tpi of one of the other handsaws from 7 to 4 whilst keeping the rip-cut, and change a 2 tpi two man crosscut to a 1.5 tpi double sided rip... It is my asumption that I'd be better off either sending it to a specialist, or should I really want to do it myself cutting brand new teeth with a punch (also jig, anvil and sledgehammer)... Does anyone have advice to the contrary.

As a collolary to the collolary, my long suffering dovetail saw (My first, and favourite saw bought for me by my grandfather as soon as I was old enough to use one) is looking a bit worse for wear (it's lost a few teeth, and one or two more have been thinned by excessive pressure when setting). It's currently a 20tpi cross cut, I'm considering the merits of changing it to rip, as obviously that would be more sensible for a dovetail saw and would likely have no noticable impact on the cross cut ablity of it; However if sharpening it it anything to go by, changing profiles would be The Most Fiddly Job In The World, Ever and given the sentimental value of it I would Have to get it right.

Anyone got any advice for me (other than sending them to experts such as Pedder and Lui)?

 

[Cheshirechappie]

Well, I'm no expert, since all I can lay claim to is reprofiling a couple of saws from crosscut to rip, but I'll make a couple of suggestions based on that experience.

If you can use a file (and if you've sharpened reasonably successfully in the past, you can), recutting a profile isn't too daunting provided you keep the same toothcount. It obviously takes longer than sharpening, so needs a modicum of patience, but no more than any craftsman is used to.

Taking the 7tpi rip to crosscut first (bigger teeth are easier to see, which takes a lot of the eyestrain out of the job), set up in a sawvice at comfortable height and - very important - in good, even light. Use a stick of 1" x 1/4" (or similar) with the edges jointed nice and straight to check that the toothline is straight (much lighter than a steel straightedge, and less damaging to teeth - tip copyright Bugbear), and joint the toothline, taking off about half the tooth depth. Then, holding sawfile in such a way that it gives the tooth profile wanted, work along the edge, putting in the new profile to about three-quarters depth. The reason for this is that the nature of hand-filing is such that the worked profiles will be slightly uneven, however hard you try to get them spot-on. So the next step is to make another pass, concentrating carefully, and examining each tooth and space to see exactly where metal needs to come off to even things up, and biasing the force applied to the file either straight down, or slightly fore or aft. Up to this point, I think I'd file straight across - don't worry about fleam or slope - to get tooth SHAPE sorted out. Then make a seperate pass, putting the fleam in. Then set, and do a final sharpening pass last of all.

For the dovetail saw, refiling from crosscut to rip I found quite straightforward, but that was on 10/11tpi saws. The tiny teeth make the job harder. I gather some people use a three-square needle file. If you've got some, magnifying spectacles or a headband magnifier would be a real boon. One thing I can pass on is that I found that a 5 to 10 degree rake gave a sweeter-cutting saw than one with zero rake, which tended to be too aggressive and 'catch' in the cut. Since a couple of teeth have broken off, I'd be tempted to joint off almost all the present teeth, leaving just a 'witness' line of notches in which to start the file, which would save to job of marking out tooth space positions. As they're so small, you'd probably cut a tooth in two passes of the needle file, so care not to overdo things would be needed. I think I might try the saw with no set, just to see how it went; if it was a bit tight in the cut, try absolutely minimal set.

On the larger saws, I can't offer much, I'm afraid. I gather from reading that punch methods of cutting teeth (using punch tooling in a flypress or power press) tend to put a bow in the blade, which subsequently needs hammering out; filing may a steady old job, but it won't bow the blade. One advantage of filing bigger teeth is that there are fewer of them, which will speed the job. I think I'd try cutting a three-quarters profile, then making the second pass to even things out as with the 7tpi saw.

In summary, I think this is a job that needs complete concentration, patience, and developing a bit of care in directing the file cuts fore, aft or straight down depending on observation of the space being worked on, and it's relationship to it's neighbours. Slow, but definitely achievable by anybody who can use a file.

 

[pedder]

A while ago I bought a job lot of Tyzak Sons and Turner saws, the seller had however had them all machine sharpened as ripsaws, so I want to change some over to crosscut; specifically a 26" 7 tpi handsaw, and a 14" 10tpi mitre saw.

When I change saws from rip to crosscut, I file half the tooth away flat. Then I file straight across, but with the correct rake (15°-20°). Then I set the teeth and file correct rake and fleam.

That is not a big deal on the small pitches, but a lot wof work on the big teeth.

AAs a collolary, I'd like to change the tpi of one of the other handsaws from 7 to 4 whilst keeping the rip-cut

Before I'd file a saw from 7tpi to 4tpi, I'd look for a saw with the needed pitch. If at all, I would go for half the pitch so only file eawy every other tooth. (Reset carefully, because you will habe to bow every second tooth in the other direction.)

As a collolary to the collolary, my long suffering dovetail saw (My first, and favourite saw bought for me by my grandfather as soon as I was old enough to use one) is looking a bit worse for wear (it's lost a few teeth, and one or two more have been thinned by excessive pressure when setting). It's currently a 20tpi cross cut, I'm considering the merits of changing it to rip, as obviously that would be more sensible for a dovetail saw and would likely have no noticable impact on the cross cut ablity of it; However if sharpening it it anything to go by, changing profiles would be The Most Fiddly Job In The World, Ever and given the sentimental value of it I would Have to get it right.

Triangluar needfile,
good light, magnification if needed.

File straight acros, only one hit per gullet, then the next ...

Cheers
Pedder

 

[Jelly]

Thankyou! based on the input you've both given me I think that the re-filing of the two tyzak saws is within my reach.

I shall leave the dovetail saw for now, as I discovered a rosewood handled gents' saw with the same pitch and rip-cut teeth hidden in a bag of miscilanious items; the plate is a little loose in the back, I considered peening the back tight round it with an engineers hammer, but remembered what Pedder said about letterpunching saw backs so for now I'll just have to live with the plate coming out of the back if it stalls in a cut.

As for the changing pitch, I'll contact Lui from Springwood Saws; He may well be able to sort out the handsaw for me and IIRC from last talking to him has a friend who specialises in framesaws who may be able to help me sort out the massive saw-plate Roger gave me; If that fails I can always try asking Ernest Bennet's who definately have the equipment to profile teeth of that size, just perhaps not the willing to engage in an unusual one-off job.

Edit: I shall try to get before and after shots of the tyzak saws at the very least, and update this on my more esoteric toolmaking endevours should they come to fruition.

 

[pedder]

Thankyou! based on the input you've both given me I think that the re-filing of the two tyzak saws is within my reach.

I shall leave the dovetail saw for now, as I discovered a rosewood handled gents' saw with the same pitch and rip-cut teeth hidden in a bag of miscilanious items; the plate is a little loose in the back, I considered peening the back tight round it with an engineers hammer, but remembered what Pedder said about letterpunching saw backs so for now I'll just have to live with the plate coming out of the back if it stalls in a cut.

Certainly you can!

I little loctite 270 will be your friend, if you don't want to hammer the spine.

As for the changing pitch, I'll contact Lui from Springwood Saws;

Very good idea, Lui uses a punch at a flypress, wich gives him very good results.

Cheers
Pedder

 

[Jelly]

It's been a while, but I finally got round to re-cutting one of the handsaws to 3tpi. I took the teeth off, used the sellers method to make a jig for the pitch, used a needle file to create little nicks to guide the file proper and set to it with a big three square file to remove the material to form these big teeth.

I'm glad I did, as cutting the teeth to half depth along about half way along the blade has eaten up the three-square entirely, being about twice the length of the large sawfiles i have, it follows I'd have used 8 of them to do the whole saw... as it is i'll end up spending a tenner on cheap files to rough out the tooth shape before finally taking them to a sharp edge with the sawfile.

Given it's purpose, I've decided to have no rake whatsoever and am considering giving it a negative rake (i.e. the tooth forward of the gullet), but I want to get it sharp and use it before making it even more agressive than normal.

Getting there slowly

 

[arnoldmason8]

Hi All-----I do not do anything more than 'touch up' saws and I use a 3 square diamond file (large needle file size of medium cut) and this has seen good service filing semi-hard steel and still performs well unlike ordinary steel files which seem to loose their efficiency very quickly. The diamond file may give a too small a radius for the larger teeth but seem to me to be ideal for cutting in the initial vee.
Hats off to anybody that can re-cut saw teeth by hand --I've tried - and failed miserably!!!

Good luck -----Arnold

 

[bugbear]

As a collolary to the collolary, my long suffering dovetail saw (My first, and favourite saw bought for me by my grandfather as soon as I was old enough to use one) is looking a bit worse for wear (it's lost a few teeth, and one or two more have been thinned by excessive pressure when setting). It's currently a 20tpi cross cut, I'm considering the merits of changing it to rip, as obviously that would be more sensible for a dovetail saw and would likely have no noticable impact on the cross cut ablity of it; However if sharpening it it anything to go by, changing profiles would be The Most Fiddly Job In The World, Ever and given the sentimental value of it I would Have to get it right.

Anyone got any advice for me (other than sending them to experts such as Pedder and Lui)?

I'm amazed at the existence of a 20 TPI cross cut! Sharpening a 20 TPI rip is hard (fiddly) enough, let alone managing fleam.

On teeth this fine it's amazingly easy to remove an entire tooth in a single file stroke, (i.e. the gullet you're filing merges into the adjacent one).

There's very little labour involved in filing such a saw, but a LOT of squinting and concentration. Good light and magnification are essential.

I just did a 16 TPI (8 degree for both rake and fleam) and that was fine enough work for me.

BugBear

 

[Harbo]

I bought a Crown D/t with 22TPI - it's so slow and my least favourite saw, even with a new handle!

Rod

 

[AndyT]

On the subject of filing very fine-toothed saws, I came across a description which might help. It's in Volume 2 of Charles Holtzapffel's huge work "Turning and Mechanical Manipulation." That's not the most obvious place to look, but he was being so thorough that he wanted to describe all cutting tools, how they work and how they are made, before embarking on using them on the lathe. You can read the whole thing on-line or download in the format of your choice. It's full of interesting stuff from the 1850s when engineering inventiveness was really taking off.

He describes three methods:

1 - mark the teeth with a double-edged cold chisel, then file.
2 - use a hooked filing guide which sits in one completed gullet to define the edge of the next one.
3 - cut directly with the file, swing the file over a few degrees, straighten up and cut again.

I really must get round to trying these out. Meanwhile, here's the full section:

Full text here on Open Library: http://openlibrary.org/books/OL7053478M/Turning_and_mechanical_manipulation

(Click 'read on-line' to go to the Internet Archive reader.)