What ppi for a compass saw?

**Berlin** · 2nd June 2013, 02:50 PM

I have a nice old compass saw of my wife's grandfather. Unknown make, unknown tpi. If I were generous I might say it has been 'sharpened' with purposeful randomness, with occasional large teeth, but I'm pretty sure it's just insanity. I'll try beat it back to something uniform but don't really know how I'm supposed to set it up.

It will come to 7ppi if I use the approx pitch of the small teeth, the rake ranges from slightly negative to 15 or more degrees so I was thinking somewhere in the middle at 7ish, does that sound about right?

I've never used or needed a big compass saw but it's a lovely old saw and looking at those crazy teeth is sending me cross-eyed so I just have to fix it.

ImageUploadedByTapatalk1370144978.004435.jpg ImageUploadedByTapatalk1370144992.844600.jpg

**chambezio** · 2nd June 2013, 04:55 PM

Hi "Berlin"
Did you survive the Brissy Wood Show OK?
I like your idea of preserving the old compass saw. If we don't do up these things along the way one day they will be gone for good and we will be the poorer for the experience.
Now,.....I am scratching my head trying to remember what is in my head regarding saw sharpening. If it was a hand saw (carpenters saw for general work) I would suggest cutting al the teeth off then reshape each tooth the set them. In your case you don't have a lot of height in the saw plate to afford to loose height. I would suggest running a flat file over the teeth to get them all to a finishing point. Then shape each tooth to 7ppi. When you come to a wrong shaped tooth as you file just press the file harder against the tooth that is shaped wrong. It will be slow going but if you persevere I am sure success will follow.
Let us know how you get on.

**Berlin** · 2nd June 2013, 06:09 PM

Hi Chambezio,

Yeah it was a nice arvo. Good to meet at few of you lot and spend some dough

A compass saw is always pretty skinny so losing a bit of depth is ok I guess. I've retoothed 2 or 3 saws but nothing as wild as this! I'll give it a joint and see what I see I guess.

This one is filed rip which makes sense I guess.

**IanW** · 2nd June 2013, 06:45 PM

Matt - if you don't want to remove the existing teeth & start over, you are pretty much stuck with the pitch it came with, or a multiple thereof. It's hard to get a sense of the exact size of the saw from a pic, but 7 tpi seems a bit coarse for the sorts of jobs I might use a saw like that for. Probably work well for cutting out circular table tops in 25mm thick wood (if you should suddenly find yourself doing a lot of those

). It was possibly used as a pruning saw, or for cutting wallboard or similar softish material, - do you know what he used it for? Fourteen tpi would be better than 7 if you wanted to use it on dry wood less than 25mm thick, and you could easily convert to that without losing any more metal than you are already going to lose jointing it....

Cheers,

**pmcgee** · 2nd June 2013, 07:27 PM

I have a few ... they haven't made it inside the house yet

ppi = 8 + 7 + 7 for 20-30cms ... 6 + 6 for 40cms

The teeth are all various rakes of rip.

Cheers,
Paul

**Berlin** · 2nd June 2013, 11:17 PM

Ian, the saw is a touch over 40cm and I have no idea what it was used for but curves in thicker timber is what I gather they were for... hmm, round table top you say?

It seems to correspond with Paul's example, but I don't know, maybe I'll split the difference and go for 10.

I'll keep you all posted

**pmcgee** · 3rd June 2013, 02:16 AM

Originally Posted by pmcgee

I have a few ... they haven't made it inside the house yet

ppi = 8 + 7 + 7 for 20-30cms ... 6 + 6 for 40cms
The teeth are all various rakes of rip.
Cheers,
Paul

Ooops ... my bad ... I was counting teeth, so actually ppi = 9,8,8,7,7.

**pmcgee** · 6th June 2013, 04:35 AM

Heh heh heh ...

From Mike Stemple ... "Keyhole saws, the red-headed step-child of saw collecting"

https://plus.google.com/u/0/photos/1...32904988541224

**Berlin** · 6th June 2013, 03:44 PM

I'll have to check that out later, I can't see it on the phone.

Never the less, here is my boy. I made it 10 point and gave it a heavy set. It might need more actually, I can see in using it that the saw needs some play to make a turn.

I don't know how often it will make the 'run on' team, but it's back in working order at least.

ImageUploadedByTapatalk1370493854.693265.jpg

**pmcgee** · 6th June 2013, 09:29 PM

Originally Posted by Berlin

I made it 10 point and gave it a heavy set. It might need more actually, I can see in using it that the saw needs some play to make a turn.

I thought that to make a tighter radius you cut with just the narrower tip end?
Paul

**IanW** · 7th June 2013, 09:57 AM

Originally Posted by pmcgee

I thought that to make a tighter radius you cut with just the narrower tip end?
Paul

True, Paul, but you still need plenty of 'wriggle room'. Roughly speaking, the more set, the easier to steer, but the harder to keep it on the road. Take a look at the amount of set on your average jigsaw blade - lots!

Cheers,

**pmcgee** · 17th June 2013, 04:42 AM

How to Saw Through Mortises | The Renaissance Woodworker

Table Saw : Solved? Not Quite Yet - Toolemera Blog

**pmcgee** · 11th July 2013, 01:19 AM

The Table Saw, part 2: Sharpening and Use – The Saw Blog

**Berlin** · 11th July 2013, 10:40 PM

Gotta say, having had a little play with the compass saw - as a saw it makes a good anything else.

**code4pay** · 12th July 2013, 08:32 AM

Originally Posted by Berlin

Gotta say, having had a little play with the compass saw - as a saw it makes a good anything else.

hmm I used mine on the weekend to cut a circle out of some MDF, same size as the top of a house hold bucket worked quite well for that. The MDF was only 6 mm so that might have helped.

Mike

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