saw sharpening critique/input

[Phil Mueller]

Pete gave me some good technique pointers in the saw file thread, so I went after a garage sale 10 pt rip saw to see what I could do. The teeth were in fairly bad shape with quite a few "low" and mishapend teeth. I ended up jointing it pretty agressively, then shaping as best I could. I aimed for 5 degree rake/zero fleam.

Used a Bahco 6 Xslim. It was a new file. I used one edge to shape, and a fresh edge for final sharpening.

Bottom line, I guess, is it cuts nice and straight.

But "tooth beauty" as I call it, is a far cry from the saws I have from Pete and Mike Allen.

My self critique is I need to work on shaping. I'm still trying to get better at knowing how much pressure to use to "push" or "pull" a tooth forward or back. Rake angle is also a bit inconsistent which has to be bacause I'm not holding the file angle (rake) consistent enough. Agree?

My other question most related to the saw file thread, is that the Bahco file left good size "flats" at the bottom of the gullet. My benchmark saws (from Pete and Mike Allen) have pretty sharp angled gullets. Is this a result of the file, my technique, too large a file...? I was really careful not to go beyond removing the jointed flats...but?

So, here it is...let the critiques begin. And thanks!

image.jpg

[Luke Dupont]

Looks very consistent. Excellent work. My bow saw blade that I cut the teeth for myself are not that consistent, and yet it still performs excellently. As long as all of the teeth are jointed and on the same plane so that they're all cutting at once, you're fine.

The difference in geometry of the gullet is just due to the characteristic of the file (rounded corners vs sharp corners). I have never used a sharp cornered file so I can't comment, but it seems that it would make being accurate (especially in cutting teeth yourself) much easier. I wouldn't worry about which one to use that much if you don't mind widening the gullets. That said, if you think you'd like to try out a sharp-cornered file, why not acquire one and compare for yourself?

[Patrick Chase]

My other question most related to the saw file thread, is that the Bahco file left good size "flats" at the bottom of the gullet. My benchmark saws (from Pete and Mike Allen) have pretty sharp angled gullets. Is this a result of the file, my technique, too large a file...? I was really careful not to go beyond removing the jointed flats...but?

In my experience Bahcos run "blunt", meaning that the corners tend to be less sharp at any given size than some other brands. Assuming "10 pt" means 10 ppi (9 tpi) the file size is about right based on the traditional rule of thumb that the file's face should be twice as tall as the length of the back of a tooth. Some people like Isaac at Blackburn Tools for example recommend smaller files than that, though.

The practical downside of a rounded gullet bottom is that you lose some ability to clear sawdust, and therefore some speed. IMO the amount of rounding you show is perfectly fine, though, because it looks to me as though you've only lost a few percent of the potential gullet volume. Most of the gullet's volume (and therefore dust-clearance ability) is up close to the tip, and you really have to round the bottom pretty badly to put a significant dent in it.

[Kees Heiden]

I have the idea that a more rounded gullets makes the plate less sensitive for stress cracking between the teeth. A good quality steel is not very suspect in this regard, but some old saws can be very brittle. And a very sharp corner might lead to s stress concentration spot.

That said, I don't really beliefe in the neccesity of using a file that has flats > twice as wide as the tooth height. Sawfiles dull on the corners, especially the modern ones. Using large files so you always have a completely fresh face when you turn the file to a new corner, are usually prety huge!

The teeth you show there looks pretty perfect to me.

[lowell holmes]

Get Lee Valleys saw filing kit and watch Ron Herman's video about saw sharpening.

You will be able to sharpen saws that are incredibly sharp and track properly.

[Pat Barry]

Overall not bad. Some rounding / faceting on the trailing edges of the tooth (yellow) points but the leading edge angles (red) look pretty consistent.

sawfiling.jpg

[Phil Mueller]

Thanks folks! I have watched the Ron Herman video a number of times...just working through the learning curve. I am also using the LV file holder/guide. I appreciate the highlights, Pat. Does help to see what is going on. I don't expect after a hand full of saws to be perfect. Sometimes it feels like learning to swing a golf club...posture, muscle memory, file angle, stroke pressure, right light angle. Come to think of it, I am a lousy golfer, so I at least feel I'm making better progress at this.

[Patrick Chase]

I have the idea that a more rounded gullets makes the plate less sensitive for stress cracking between the teeth. A good quality steel is not very suspect in this regard, but some old saws can be very brittle. And a very sharp corner might lead to s stress concentration spot.

It's certainly true that sharper corners concentrate stress, though as you say the plate should be strong and/or ductile enough to render that a nonissue.

My engineering intuition is that if a saw were brittle enough for sharp gullets to be a problem, then you wouldn't be able to set it (which requires plastic deformation of the teeth).

[Chris Fournier]

It's certainly true that sharper corners concentrate stress, though as you say the plate should be strong and/or ductile enough to render that a nonissue.

My engineering intuition is that if a saw were brittle enough for sharp gullets to be a problem, then you wouldn't be able to set it (which requires plastic deformation of the teeth).

I think that it would have to be a very messed up saw plate to see any cracks propagating at stress risers and yes the teeth would likely break when set not while in a cut.

[Luke Dupont]

I learned to sharpen saws by watching Ron Herman's video. I still have the video.

There are no rounded teeth in his video. If a saw is in bad shape, I file it smooth and then file new teeth. Rounding of the teeth is unacceptable. The sharpened tooth line should "grab" your palm if you just put your hand on the toothline.

Ron Herman really addresses all of this.

You need a filing system. I explained in another post how I do it and I have been successful. My saws are sharp, cut smoothly, and cut fast. If you need a tooth pattern, down load it, there are sites that will provide them. Or if you will send a private message to me, I will send you a pdf showing whatever spacing you want. You print the pdf and cut 1/2" strips, tape the strips together end to end so they will have the length . I attach the strips to the saw plate on the upper side, not on top. A single file cut at each line will locate the teeth. These marks become the gullet and the teeth develop when adjacent gullets meet each other.

We're talking about rounded gullets, not teeth. The teeth are still sharp.

[Stewie Simpson]

More critical as you work your way through 10 tpi/ppi spacing's and above, the rounded gullet formed between 2 teeth will have an effect on those tooths end height. The provided example is not of my work.

[lowell holmes]

I didn't understand that rounded gullets were desirable. They might work on larger teeth, but never on a dovetail saw.

[Stewie Simpson]

Lowell; it saddens me to tell you those teeth were filed by Paul Sellers.

[lowell holmes]

I attended classes at Homestead Heritage in Waco Classes while Paul was there.
I know Paul has reasons for what he does. I may have to try one to see why he would do that.
Maybe I should have said that would never work on one of my saws.

I never saw him leave space between gullets twenty years ago.
He filed his saws all rip cut at that time. Like Tage Frid, he cut crosscut with fine rip filing.
I do file crosscut on crosscut saws.

It is 8:45 on Sunday Morning here in Texas. What time is there in Australia. I understand time zones, but I do get confused with the time differential in New Zealand and Austrailia. You not only are in a different time zone, but also different hemispheres. I know hemispheres have no bearing on time.

[Stewie Simpson]

Lowell; I am on Australian Eastern Standard Time. https://www.timeanddate.com/time/zones/aest

Stewie;