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Saw Talk #10: Hand Shaping and Sharpening the Teeth on a Backsaw

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Blog entry by Brit posted 859 days ago 10746 reads 13 times favorited 62 comments Add to Favorites Watch
« Part 9: Making a Saw Vise Part 10 of Saw Talk series Part 11: More Thoughts on Sharpening Backsaws »

You know I said at the end of my last post that I’d post a picture of each saw and tell you how I was going to sharpen them and why? Well I lied. :-) The temptation of my restored backsaws, a saw vise and a bundle of saw files was just too much. I had to sharpen a saw, but which one? I thought about it for a while and settled on the little Spear & Jackson 8” Dovetail saw. Remember this one?

I chose it for two reasons:

  1. For a dovetail saw, the depth of cut is quite big at 50mm. I could afford to mess up two or three times and still have enough depth of cut left to have a useable dovetail saw.
  2. It’s just so damn cute and I couldn’t wait to try it out.

Looking closely at the teeth under a magnifying glass, I could see that quite a few of them were misshapen. Of course they were also blunt and the set had been removed when I sanded the saw plate during the restoration. It had originally been sharpened at 15TPI rip with what looked like 8 degrees of rake, but it varied a lot from tooth to tooth. Before I did anything to it I thought I’d try it out, so I put an off-cut of Sapele in my Workmate and attempted a cut. I got about 4mm into the cut and it totally jammed.

I decided that the best course of action was to remove the existing teeth and file new teeth, rather than try to correct the existing teeth. They were just too bad.

Since I have a Gramercy dovetail saw that is filed 18TPI rip with 0 degrees of rake, I don’t have a problem starting 0 rake dovetail saws. So I decided to keep this one at 15TPI rip with 0 degrees of rake.
The first step was to grip the saw upside down in my Workmate and file the teeth completely off.

The file holder I made worked great and soon I had a flat, clean edge on the saw plate.

Some people argue that you can’t hand file new teeth into a saw plate as you’ll never get them all exactly the same size. Well the good news is that within reason, they don’t need to all be exactly the same size. Of course you strive for perfection, but if a few teeth are slightly off, the saw will still work and cut well. I believe it was Mike Wenzloff who said:

It’s not perfect teeth you’re after, it’s perfect sawing.

Still, 15TPI is pretty small and there’s precious little room for error, so to ensure I filed 15 teeth for each of the 8 inches on the saw plate, I drew a template in Google Sketchup. When I printed it out, I made sure that my printer settings would print it full scale. Then I cut it out, put double-sided tape on the back and carefully lined it up with the front edge of the saw plate and parallel to my jointed edge.

Now I’m 51 and I wear glasses for close-up work. Even with my glasses on, the teeth on the template were a blur. There was no way I would be able to do this accurately without the aid of a good magnifying glass. Luckily I had one on a flexible gooseneck with a heavy base. So I mounted the saw in my saw vise and positioned the magnifying glass. The teeth still looked small, but that was as good as it was going to get.

I’m using a 7” second cut needle file to shape and sharpen the teeth on this saw. I believe you could also use a 4” double extra slim taper file for 15TPI. Being new to saw sharpening, I must admit to being somewhat apprehensive at this point. I knew that if I was going to successfully shape these teeth, it would require every ounce of concentration and care that I could muster. I resolved to take it extremely slowly. So I picked up the file and working from the heel to the toe, I positioned the file very accurately just in front of the first tooth. Sighting down from above to ensure the face of my file was vertical (0 rake), I carefully pushed the file forward about an inch to establish a tiny groove. Now the file had a course to follow, I made four light, full length strokes. Watching the outline of the teeth on my template, I was able to see whether I needed to apply pressure against the front of the tooth, straight down, or both. I repeated this process for each tooth, constantly checking the tooth geometry from the template side and the back.

It took me about 10 minutes per inch with occasional rests. I was finding this very hard indeed, but so far I hadn’t screwed up once. On the third inch, I started speeding up a bit and had to force myself to slow down again. Teeth this small can very easily be ruined with a single misplaced file stroke. I was reminded of JJW5858's tag line.

Make something you’ll love tomorrow…and do it slowly.

When I got all the way to the toe, I knelt down and looked along my template tooth by tooth. If I could still see any of the black lines, I made a mental note that I needed to apply downward pressure or press against the front of the tooth, then placed my file in that groove, stood up and stroked the file accordingly.

Next I peeled off the template, put the saw back in my Workmate and lightly jointed the teeth again. I ran a permanent marker along the tips of the teeth which showed up the tiny flats a little better. Putting it back in the saw vise, I made one more pass along the teeth to remove the flats.

Shaping all 120 teeth took me about 90 minutes and boy did I feel drained. I honestly can’t remember the last time I concentrated that intensely.

I rubbed some paraffin wax on the plate and tried the saw in some Sapele. It cut pretty well, but with every stroke I could feel it grabbing at the same place. I put my finger on the tooth that seemed to grab and sighted along the toothline. There was one tooth that was slightly higher, which I must have missed on my last pass. I filed it down and tried the saw again. The saw no longer grabbed and I could get a better feel for how it cut. As the saw buried itself deeper in the cut, it felt a bit tight. Not much, but enough to require a bit of set. I have two Eclipse No.77 saw sets and the one with the red paint is for finer teeth and the pin that pushes the saws teeth against the anvil is smaller.

You can see the difference in the two sets in the following photo.

So I adjusted it to give the least amount of set possible. After marking every other tooth with a permanent marker, I went along one side of the plate setting all the black teeth. Then, working from the other side, I set all of the unmarked teeth.

After setting the teeth, I tried the saw again. It cut much easier, but the kerf was a little too wide for my liking. I laid the saw plate flat on my granite slab and ran a medium India oil stone along each side twice to remove a bit of the set.

Now it was cutting nicely and left a thinner kerf. I found that this saw responds best to a light grip and relaxed arm movements using all the teeth. I feel a connection with this saw now and I’m sure I’ll reach for it often.

So here she is my friends, my first completed saw sharpening job. Isn’t she a beauty? Now the teeth are in good shape, I aim to keep them that way.

And this is where it all started.

To be perfectly honest with you, it was extremely difficult to shape these teeth accurately by hand, but I’m still glad I chose to tackle this saw first. It gave me enough of a workout to develop a feel for using a saw file and controlling it precisely. What a satisfying feeling it was to see, hear and feel this saw cut wood again.

If anyone were to ask me what I did today, I’d tell them that I made something I’ll love tomorrow…and I did it slowly.

Thanks for watching!

P.S. – In case you missed it, do yourself a favor and check out JJW5858’s (Joe) blog post entitled Exercises in Artisanship.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.



62 comments so far

View bandit571's profile (online now)

bandit571

6686 posts in 1286 days


#1 posted 859 days ago

Good show, sir, GOOD SHOW! I tried my hand at this tonight. It will be awhile before I get this good though.

-- A Planer? I'M the planer, this is what I use

View jjw5858's profile

jjw5858

1110 posts in 1205 days


#2 posted 859 days ago

Wow… your work is looking really great Andy! I knew you were the man for the sharpening job! Great stuff! I will surely reference this as my journey in saws and sharpening continues!

Thanks for sharing and all the best,

Joe

-- "Make something you love tomorrow...and do it slowly" JLB

View Brandon's profile

Brandon

4137 posts in 1554 days


#3 posted 859 days ago

Wow. Just. Wow.

Oh, and when can I send you my saws for sharpening, Andy? :-)

-- "hold fast to that which is good"

View ShaneA's profile

ShaneA

5257 posts in 1201 days


#4 posted 859 days ago

Very interesting post Andy. This series has been great. All have been great reading. You should be proud of your skills and your saws. Very well done sir. Look forward to more.

View Philip's profile

Philip

1080 posts in 1142 days


#5 posted 859 days ago

Holy cow…what a labor of love. I’m very impressed. Well done!

-- If you can dream it, I can do it!

View Brit's profile

Brit

5107 posts in 1446 days


#6 posted 859 days ago

Bandit – Thank you. Keep at it and you’ll get there. I thoroughly recommend Joes’s advice to slow down. Don’t be concerned about how long it takes you. Concentrate on quality and the speed will come with practice.

Joe – What a rollercoaster ride of doubt and self-belief I went on with this saw. Thanks again for reminding me to take a chill pill and slow down.

Brandon – When I’ve done my own. :-)

Shane & Philip – Thank you. I’m glad you like what you see and read. It makes it all worthwhile.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View llwynog's profile

llwynog

282 posts in 1182 days


#7 posted 859 days ago

Andy, this is definitely on of my favourite post ! I admire the guts you exhibited in jointing off completely the old teeth and define your own. I have a large handsaw that I am planning to learn sharpening on but I think that I will keep the safety of existing teeth to guide me at first.

Thanks a lot for this most excellent post (also loved all the other ones in the series)

-- Fabrice - "On est bien bête mais on sent bien quand on se fait mal" - my grandfather

View racerglen's profile

racerglen

2256 posts in 1383 days


#8 posted 859 days ago

Done it again Andy !
I hate to repeat but WOW !

-- Glen, Vernon B.C. Canada

View Jim Rowe's profile

Jim Rowe

540 posts in 915 days


#9 posted 859 days ago

Andy
A Masterclass! What a beautiful end product you have created.
Jim

-- It always looks better when it's finished!

View Brit's profile

Brit

5107 posts in 1446 days


#10 posted 859 days ago

llwynog – It did take some big ones to file all the teeth off of the first saw I’ve sharpened, but once I’d drawn the template, I couldn’t see any reason why it wouldn’t work so I just went for it.

Glen – I had to remember to breathe. :-)

Jim – Thanks. I don’t know about a masterclass, but it cuts fine and that’s the important thing.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View RGtools's profile

RGtools

3302 posts in 1257 days


#11 posted 859 days ago

The shot with the kerfs really says it all Andy. Great post as usual. I will have to try it out at some point.

-- Make furniture that lasts as long as the tree - Ryan

View terryR's profile

terryR

2978 posts in 911 days


#12 posted 859 days ago

Andy, you continue to raise the bar for all of us! What a nicely written blog…and thanks for the close up photos of your sharpening process. That paper template is a great idea…oh my…15 ppi for your first attempt at sharpening?! Just goes to show what a master you are. :-)

That is a gem of a saw!

-- tr ...see one, do one, teach one...

View Brit's profile

Brit

5107 posts in 1446 days


#13 posted 859 days ago

Thanks Ryan. If you’re going to try it, make sure you get a good night’s sleep first. :-) Seriously though, once you’ve done it you know what to expect, but the first time it’s just one big unknown.

-- Andy -- Old Chinese proverb say: If you think something can't be done, don't interrupt man who is doing it.

View SASmith               's profile

SASmith

1550 posts in 1590 days


#14 posted 858 days ago

Great show and tell.
Thanks for sharing.

-- Scott Smith, Southern Illinois

View Dave's profile

Dave

11142 posts in 1443 days


#15 posted 858 days ago

Andy that was a fun and interesting journey you took me on. I did enjoy it a lot. The impressive part was your eyes are like mine and it did not stop you.
Now you are going to need to build a saw till to fit your wonderful set of saws.
Andy you sir are an artisan.

-- Superdav "No matter where you go - there you are." http://chiselandforge.com

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