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Ideal length of bow saw cheeks (arms)?

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Forum topic by Dave Polaschek posted 09-16-2018 05:08 PM 628 views 0 times favorited 19 replies Add to Favorites Watch
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Dave Polaschek

2838 posts in 782 days


09-16-2018 05:08 PM

Topic tags/keywords: bow saw design

I’ve recently build a Gramercy Tools Turning Saw from their kit. I think it turned out pretty well.

I’ve read their design thoughts and they discuss a lot of the design issues, but there doesn’t seem to be any discussion of the length of the cheeks (or arms) of the saw. If you’re going to hold it by the cheek, clearly the cheek needs to be big enough to hold on to. But if you’re going to use the handle as the Gramercy design does (which makes sense for a turning saw), the cheek doesn’t need to be that big. Is there any reason NOT to make a bow saw with shorter cheeks?

I think I’m going to head out to the shop to do a little experimenting….

-- Dave - Minneapolis


19 replies so far

View TravisH's profile

TravisH

627 posts in 2135 days


#1 posted 09-17-2018 02:26 AM

Probably can shorten it but likely need to make some other changes. I would believe it would start to behave different in regards to blade tension as you started to change the length of the arms and fulcrum point. Might have to twist it a few more times or less times to get to same tension. Might need to change thickness or width of the arms to compensate. As you start to do this sort of stuff the saw may become less balanced in use.

As they mention you will also have a decrease in cut depth but may not be an issue depending on how you are using the saw. Easy enough to whip out a few different arms to test and might find out a set up that you find more comfortable using.

I built mine several years ago and liked it but really haven’t used it too much after the initial honeymoon period.

View Oldtool's profile

Oldtool

2736 posts in 2391 days


#2 posted 09-17-2018 12:20 PM

Good morning Dave,

I am not a user of a bow saw, but I agree with TravisH regarding depth of reach and the tension issue.Balance is also an issue, the feel in the hand, especially if using the handle because the weight will work against you & might cause difficulty following a line.

What ever you determine via your shop experimentations, post the results, I’m curious to see what you find out.

Tom

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

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Dave Polaschek

2838 posts in 782 days


#3 posted 09-17-2018 08:59 PM

I’m keeping the arms symmetric (same length above and below the stretcher), so tensioning should be the same. I expect I could lighten up the wood more due to the shorter level-arms, but I left it pretty close to the one with the 12” cheeks (5” from stretcher to blade or tensioning line, compared to 2.5” on this one with 7” cheeks).

Yeah, a decrease in cut depth will happen, but it’s a turning saw. Don’t think I’ll find myself in the middle of a large board all too often…

Got the epoxy curing on the handles now. I’ll hopefully get a chance to test-drive it tomorrow evening.

-- Dave - Minneapolis

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Oldtool

2736 posts in 2391 days


#4 posted 09-17-2018 11:27 PM

I’ll hopefully get a chance to test-drive it tomorrow evening.

Sounds good, post a picture.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

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MikeB_UK

151 posts in 1235 days


#5 posted 09-18-2018 10:13 AM

Should be easy enough to do 2 arms with a set of holes for the blade holders and matching notches for the cord on the tensioning side.
It might not look terribly pretty, but should give you a chance to check several different positions (Both symmetric and offset) from just the one build.

If nothing else, it’ll save me trying it :)

-- If I say I'll fix something around the house I will, there is no use nagging about it every 6 months.

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Dave Polaschek

2838 posts in 782 days


#6 posted 09-18-2018 12:18 PM

I might do that after I finish the test of the short arms this evening, Mike. Part of the reason for wanting shorter arms is to have a lighter saw.

But if you want to run some tests too, I’d appreciate the help! ;-)

-- Dave - Minneapolis

View MikeB_UK's profile

MikeB_UK

151 posts in 1235 days


#7 posted 09-18-2018 12:42 PM


I might do that after I finish the test of the short arms this evening, Mike. Part of the reason for wanting shorter arms is to have a lighter saw.

But if you want to run some tests too, I’d appreciate the help! ;-)

- Dave Polaschek

A lighter saw? One of the reasons I made that junior frame/hack saw so bulky was to add heft to it.

I’ll have a look around and see where I can get a blade in the UK.

-- If I say I'll fix something around the house I will, there is no use nagging about it every 6 months.

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Dave Polaschek

2838 posts in 782 days


#8 posted 09-18-2018 01:05 PM

Well, it seems to me, for cutting curves, a lighter saw is better. Less weight to start and stop every stroke.

Or maybe I’m barking up the wrong tree. Guess I’ll find out.

-- Dave - Minneapolis

View theoldfart's profile

theoldfart

10169 posts in 2651 days


#9 posted 09-18-2018 03:28 PM

Dave, I’m with you on lightweight turning saws, less of momentum ruining the cut. On the other hand for resewing I want mass, the more the better.

As far as arm length goes I haven’t given it much thought. I’ll have to look at my saws.

-- "With every tool obtained, there is another that is needed" DonW ( Kevin )

View MikeB_UK's profile

MikeB_UK

151 posts in 1235 days


#10 posted 09-18-2018 03:32 PM


Well, it seems to me, for cutting curves, a lighter saw is better. Less weight to start and stop every stroke.

Or maybe I’m barking up the wrong tree. Guess I’ll find out.

- Dave Polaschek


You might be right, Knew Concepts probably had a reason behind their fret saw.

Well, unless they made the prototype out of Meccano and forgot to tell the manufacturer.

-- If I say I'll fix something around the house I will, there is no use nagging about it every 6 months.

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Dave Polaschek

2838 posts in 782 days


#11 posted 09-18-2018 11:58 PM

No results tonight. Not feeling well and didn’t dally in the shop. It’ll probably be the weekend before I get time to test things out.

-- Dave - Minneapolis

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theoldfart

10169 posts in 2651 days


#12 posted 09-19-2018 07:23 PM

Dave, my three saws each have a different ratio of upper to lower arm length

-- "With every tool obtained, there is another that is needed" DonW ( Kevin )

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Dave Polaschek

2838 posts in 782 days


#13 posted 09-19-2018 08:07 PM

Thanks, Kevin. I also got a note from Joel at Tools For Working Wood saying that he’s seen bow saws with all different lengths of cheeks. Shorter ones can mean more tension, and longer ones less tension, but I think I’m far enough away from breaking the wood that it’s up to how many cranks I give the toggle.

There won’t be any shop time the next few evenings, so it’ll probably be the weekend before I get to play, but I’ll definitely report back when I do get time.

-- Dave - Minneapolis

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Dave Polaschek

2838 posts in 782 days


#14 posted 09-22-2018 03:14 PM

After a morning of fixing errors and tweaking the fit, I got the shorty bow-saw together. It cuts fine, but as you would expect, the depth of cut can be an issue. But it’s noticeably lighter, and less “floppy” (by which I mean, wanting to take a small wobble on my part and turn it into a big swing of the saw – rotational inertia matters, it turns out), and I suspect I’ll reach for this one first, and go to the more traditionally proportioned saw when I need more depth of cut. Note that this is a 12” long blade.

Time to take it apart and clean things up a bit before getting a coat of oil on it.

-- Dave - Minneapolis

View Oldtool's profile

Oldtool

2736 posts in 2391 days


#15 posted 09-22-2018 04:10 PM

This looks like a 18th century coping saw, neat.
Question: do you hold the handle or the arm when using? I can see advantages to both grips, curious what an expert thinks.
Enjoy the new tool Dave, well made.

-- "I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The point is to bring them the real facts." - Abraham Lincoln

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