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Disston Handsaw Restoration #6: Sharpening the Blade

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Blog entry by Skip Mathews posted 07-25-2014 05:18 AM 935 reads 1 time favorited 4 comments Add to Favorites Watch
« Part 5: I think I am finished Part 6 of Disston Handsaw Restoration series no next part

Here are a few pictures and notes on my sharpening process.

Many of you know a great deal more than I about sharpening sawblades but I thought I would document my process and see if anyone has any pointers for improvement.

Here is my set up.
I made my vise out of a couple of 2×8 yellow pine and beveled the top edge to make it narrow and allow me to get closer to the blade for filing. I checked for a slight bow in the wood so when the two boards are placed together the ends touch and there is a slight gap between the board in the middle. That allows me to clamp in a vise at the center and know that the outer ends will also grip the blade tight. I add the extra clamps at the ends when working on long blades because it isn’t tight enough at the ends and will vibrate.

What I like best about this set up is that I can clamp the entire blade and not have to move it along through a short vise. I have a bright light clamped above and shining on the work space. The light is very important to me and I also use a magnifying glass.

All the methods I use are found in the Saw Sharpening Treatise here

Rather than just using my normal angles for rake and fleam I checked the saw to see how it had been sharpened. I found it to be 11-degree rake and 20-degree fleam angles. The little block of hardwood attached to the end of the file helps to guide the rake angle and the adjustable square laying on the bench gives me a visual of the fleam angle.

This was one of my easier sharpening projects. The teeth were very even and mostly I just touched them up and filed the rust off. Just two strokes per tooth.
This saw also has a very slight arc (3/32”) in the cutting side of the plate. I think this is the way it was made originally.

I really enjoy this part of restoring a saw.

One thing I am still not sure about is fine tuning. I have one little back-saw I sharpened that wants to wonder off square as you cut. I don’t think it is user error because I can cut very straight and square with a different saw.
The other thing I am curious about is custom sharpening based on how a saw is used. What angles are best and why. Some saws even have teeth that change from toe to heal.

-- Being focused on a project is the best meditation, it allows you to live in the moment"



4 comments so far

View kenn's profile

kenn

788 posts in 2471 days


#1 posted 07-25-2014 06:33 PM

Your wandering saw May have too much set on one side vs. the other. If it is wandering a little, running a sharpening stone down the heavy side might fix it. Saw flat on bench, light pressure on the stone, try two passes from heel to toe. Test cut and check for improvement. Good luck.

BTW, the definitive Lumberjocks post on saw read and sharpening is by Brit, aka Andy. He’ll give you more info than I can. Good luck.

-- Every cloud has a silver lining

View chrisstef's profile

chrisstef

11472 posts in 1757 days


#2 posted 07-25-2014 06:46 PM

Ill agree on everything kenn said about the wandering saw. Andy’s blog series and video taught me how to sharpen and now I really enjoy it.

As to what works in what situations is a pretty open ended subject in my opinion. I haven’t moved too far away the standard filings (5-10 degrees rake on rips saws, 15 rake – 25 fleam on xcut) but one could go on and on over progressive filing, sloped gullets, breasted tooth lines and different rake and fleam combinations.

I like the move using the bevel gauge!

-- "there aren’t many hand tools as awe-inspiring as the #8 jointer. I mean, it just reeks of cast iron heft and hubris" - Smitty

View summerfi's profile

summerfi

1501 posts in 438 days


#3 posted 07-25-2014 06:49 PM

Skip – It looks like you’re doing great. One thing I didn’t see you mention is jointing the saw. Perhaps that’s because your teeth were in good shape and just needed a touchup. For most sharpenings, jointing is the foundation upon which everything else is built, and is thus very important.

The arc in the toothline is called a crown, or breasted toothline. It was common on many old quality saws.

Here is a link to Andy’s sharpening video. It is a must see, if you haven’t found it already.

-- Bob, Missoula, MT -- "Of all the tools I own, my favorite is a good sharp pocket knife." - My Dad

View Skip Mathews's profile

Skip Mathews

82 posts in 601 days


#4 posted 07-25-2014 08:09 PM

Thanks Ken! I will look at the set and see if that’s the problem. I haven’t done much with setting teeth yet.

Chris – Thanks for the comment! I will check out Andy’s blog.

Bob – Thanks for the encouragement and thanks for the info on the breasted toothline.
Actually, I forgot to mention the jointing. I just hold the file flat with my hand and draw it heel to toe. On this saw I made one very light pass with the file and hit the top of all but two or three teeth. No flats at all. I wonder if it had just been sharpened before being put away to rust.
I am pretty impressed with how much design and engineering went into the saws from that period. They are definitely worthwhile to restore.

-- Being focused on a project is the best meditation, it allows you to live in the moment"

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