Back saw for cutting steel and brass?

[Nigel WattsParticipant @nigelwatts49512]

I have recently taken up repairing antique clocks and like to use hand tools wherever I can as this often reproduces better the style and finish of the original. One task is the cutting of slots in screw heads. Of course this can be done using a circular saw in the the lathe or mill, but I don't doubt that it would have done by hand originally.

My much thumbed copy of Ian Bradley's "Beginners Workshop" illustrates a back saw identical to a woodworker's gents saw and specifically mentions its use for slotting the heads of screws. This feels right to me as hack saws and jewellers saws just don't have the straighteness and rigidity.

The question is where to get such a saw, or how to make one. How many tpi? what should it be made be made of? Hardened or unhardened, and if the former how would one sharpen it?

[Nigel WattsParticipant @nigelwatts49512]

[Michael GilliganParticipant @michaelgilligan61133]

Interesting question, Nigel

Are you sure that there isn’t some confusion with the traditional file ?

**LINK**

https://www.cousinsuk.com/product/slotting-screw-head-1850-vallorbe-swiss

MichaelG.

[John HaineParticipant @johnhaine32865]

How about trying a (junior) hacksaw with the blade reversed, so it cuts on the pull rather than push? Same fashion as a Japanese saw.

[Ian PParticipant @ianp]

Posted by Michael Gilligan on 27/11/2019 11:52:18:

Interesting question, Nigel

Are you sure that there isn’t some confusion with the traditional file ?

**LINK**

https://www.cousinsuk.com/product/slotting-screw-head-1850-vallorbe-swiss

MichaelG.

That looks an odd section for cutting slots in screwheads although that's what Cousins describe it as.

Ian P

[pgk pgkParticipant @pgkpgk17461]

Could he have been using an 'ordinary' backsaw for that purpose?

[BazyleParticipant @bazyle]

Check model railway suppliers. I got a replacement blade for a small jewellers saw about 1in x5in when I was a schoolboy and bolted it to some Meccano to save using precious pocket money for the frame. Then I also got a similar mini gents saw from Proops at a show some time ago.
For brass a good woodwork saw is adequate if you can find probably 25tpi plus.

here's one although you already need a saw of some sort to cut off the arm and leg needed in exchange.

Edited By Bazyle on 27/11/2019 12:38:30

[Martin ConnellyParticipant @martinconnelly55370]

Jigsaw blades cut on the pull stroke. It should be an easy task to make a handle for them. If you cant find zero set then rub them on a stone to make them flat and the thickness you want. A cheap option to try if you can't find exactly what you want.

Martin C

[Clive FosterParticipant @clivefoster55965]

Probably a real unicorn hunt these days but maybe look out for a set of Starrett 249 Screw Slotting Blades. Like these **LINK**

As I recall it 4 different widths in the set. They are 8" long and fit a standard adjustable hacksaw frame. Fine tooth blades with no set on the teeth.

Basically a really skinny file with deep safe edges.

Discontinued in the 190's I think. Probably a very slow seller as few folk had need of such and even fewer would know about them.

Clive

[Ian PParticipant @ianp]

Posted by Nigel Watts on 27/11/2019 11:40:32:

The question is where to get such a saw, or how to make one. How many tpi? what should it be made be made of? Hardened or unhardened, and if the former how would one sharpen it?

I think you would have to be very dedicated to make a saw from scratch!

It does not matter what its made from as long as its harder than the material its going to cut, 99.9% of saw's are made of steel and hardened in some way. Number of teeth, or the specifically the pitch, depends on the diameter of the screwhead as there should always be several teeth in engagement in the length of the cut.

Whilst the earliest makers of timepieces would have cut the slots with a saw or narrow file I bet its wasnt such a long time before they started to use slitting saws.

Do you want to cut the slots by hand to maintain the hand-made look?

Ian P

[Nigel WattsParticipant @nigelwatts49512]

Posted by Michael Gilligan on 27/11/2019 11:52:18:

Interesting question, Nigel

Are you sure that there isn’t some confusion with the traditional file ?

**LINK**

https://www.cousinsuk.com/product/slotting-screw-head-1850-vallorbe-swiss

MichaelG.

Ian Bradley writes in an admirably clear way.  This is the extract from the book:

Edited By Nigel Watts on 27/11/2019 13:13:36

[BazyleParticipant @bazyle]

A hand shaper would be quite good for making such slots, say and Adept No 1. And a shaper would be able to make fine saw blades before hardening too.

[Nigel WattsParticipant @nigelwatts49512]

Posted by Ian P on 27/11/2019 12:43:12

Do you want to cut the slots by hand to maintain the hand-made look?

Ian P

Broadly speaking, yes. Having spent far more time working in wood than metal I also feel more comfortable with hand tools, especially for small one-off jobs. It cuts out all that setting up.

Earlier in the week I was filing the end of some 1/4 inch silver steel rod down to a 7mm square at my clock club to fit into a fly cutter arbor on one of their milling machines. I found it a very satisfying process, particularly when I discovered in a drawer a magnificent vintage 16 inch plus flat bastard file made in Sheffield of best cast steel. It could have been a bit sharper, but it felt just like planing wood. My tutor, who rarely dishes out praise, even complemented me on the flatness of my strokes.

[Nigel WattsParticipant @nigelwatts49512]

Posted by Bazyle on 27/11/2019 13:13:55:

A hand shaper would be quite good for making such slots, say and Adept No 1. And a shaper would be able to make fine saw blades before hardening too.

Never come across anything like this before. What an interesting piece of kit!

[Nigel WattsParticipant @nigelwatts49512]

Posted by Bazyle on 27/11/2019 12:32:37:

Check model railway suppliers. I got a replacement blade for a small jewellers saw about 1in x5in when I was a schoolboy and bolted it to some Meccano to save using precious pocket money for the frame. Then I also got a similar mini gents saw from Proops at a show some time ago.
For brass a good woodwork saw is adequate if you can find probably 25tpi plus.

here's one although you already need a saw of some sort to cut off the arm and leg needed in exchange.

Edited By Bazyle on 27/11/2019 12:38:30

I wonder if a cheapish modellers' saw like this would work on mild steel. It would be too fiddly to sharpen no doubt but if it had a reasonable life one could just throw it away and get a new one.

Edited By Nigel Watts on 27/11/2019 13:39:44

[MichaelRParticipant @michaelr]

Fine saws for wood and non ferrous metals Here may be something that may serve your purpose scroll down the page..

Mike.

Edited By MichaelR on 27/11/2019 13:44:38

[Neil WyattModerator @neilwyatt]

The illustration just looks like a razor saw too me. Better ones work on mild steel as well as brass.

Neil

[JasonBModerator @jasonb]

Dictum sell a couple of japanese saws for metal like this and less likely this

[Adam MaraParticipant @adammara]

In the good old days a Eclipse no. 45 Back Saw would be ideal, with 3 interchangeable blades for metal, 32, 44 and 60 tpi, cost in in 1964 5/- (25p). One recently sold on the internet for £22!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nigel Watts on 27/11/2019 13:11:35:

Posted by Michael Gilligan on 27/11/2019 11:52:18:

Interesting question, Nigel

Are you sure that there isn’t some confusion with the traditional file ?

**LINK**

https://www.cousinsuk.com/product/slotting-screw-head-1850-vallorbe-swiss

MichaelG.

Ian Bradley writes in an admirably clear way. This is the extract from the book:

Edited By Nigel Watts on 27/11/2019 13:13:36

.

Thanks for the illustration, Nigel

I have a saw that looks exactly like that in Fig.16 … but it is only really suitable for balsa, and some plastics.

Perhaps there are [were] better versions available.

MichaelG.

[Brian GParticipant @briang]

For a VERY narrow slot, perhaps the fine-toothed Zona razor saws might be suitable. Chronos list several . For a wider slot, how about a joint square edge file like these from Arc ?

Brian G

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian P on 27/11/2019 12:14:22:

Posted by Michael Gilligan on 27/11/2019 11:52:18:

Interesting question, Nigel

Are you sure that there isn’t some confusion with the traditional file ?

**LINK**

https://www.cousinsuk.com/product/slotting-screw-head-1850-vallorbe-swiss

MichaelG.

That looks an odd section for cutting slots in screwheads although that's what Cousins describe it as.

Ian P

 

.

If you want a flat bottomed slot, change files to finish off.

MichaelG.

.

As per Brian’s link … These are the ARC ones [which have ‘half round’ edges]

Edited By Michael Gilligan on 27/11/2019 14:23:23

[Ian PParticipant @ianp]

Ah, that makes sense now, thanks

Ian P

[speelwerkParticipant @speelwerk]

When multiple heads come next to each other in a row I use a slitting saw to make the slots, it is a much neater sight when they are identical. With only one screw head a piercing saw with the correct blade thickness will do fine. If the head becomes very small when the thread is below M 1.0 a piercing saw with the smallest thickness of blade is best to use. A screw-head file is much too wide that work. Niko.

[Simon Williams 3Participant @simonwilliams3]

Hello all, interesting question.

First observation is that you'll never get a pretty slot using a saw with set on it. So using hacksaw blades whether they're wavy set or a normal wood saw with side set ain't going to cut it, if you'll excuse the pun.

The slotting file is the right tool, and I seem to remember correspondence from Ketan a few months ago saying he'd bought some – inadvertently – and were they of interest. Might be worth a call. A slotting file is a thin file with no teeth on the faces, but teeth on the edges so it cuts sideways – or downwards if you hold it on edge.

A razor saw has also been mentioned – that's what the top saw in this pic' is:

xxx

 

That's an Exacto razor saw, and it will cut brass but the blades aren't very hard and you'll lose the teeth pretty quickly. It's really intended for cutting wood, particularly balsa or similar.

The bottom one is a jeweller's backsaw – if you can find a source of good quality blades it'll cut anything a hacksaw would, as it's designed for cutting 9 ct gold which is pretty hard. The blades are removable from the brass back, and usually double sided, but beware of cheap and nasty blades they won't last as well as the razor saw. My Dad was a silversmith, we used to have periodic expeditions shopping for this sort of stuff round the Hockley Hill area of Birmingham, but I've lost touch with this over the last thirty years and I don't know where to buy these blades. I remember the good blades were expensive, but the cheap ones were absolutely useless!

The backsaw willl give you a good groove to guide the slotting file and remove the majority of the metal, but the blade on this one is only 0.35 mm thick so you need parallel cuts or follow with a narrow file to get a slot which looks in proportion. You used to be able to buy blades of different thicknesses.

HTH Simon

Edit – MichaelG has – as oft before – pipped me to the post about ARC's slotting files.

Edited By Simon Williams 3 on 27/11/2019 14:36:30

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