How to reduce head diameter of countersunk wood screw?

[File HandleParticipant @filehandle]

Mick
Last night I checked my own supply of 4 by 1/2″slotted screws – at that price mine are worth over £100. my whole stock of slotted screws would be worth thousands. However, I was in a hardware shop this morning, their price was 2p each for this size, by the feel of it the box they had was virtually full, although if I recall correctly I paid 50p for mine – a nearly full box of new very old stock.
But I can understand why new one are that expensive, demand will be low, so prices are high.
I got to wondering how much useful old new stock is around in the country? I bet a lot is simply discarded.
last night I did a very quick Internet search and found 25 for £5 – probably plus postage.

[Mick BaileyParticipant @mickbailey28509]

I see boxes of British made screws at car boots and they don’t sell. My joiner friend offered a few dozen boxes of unopened Nettlefold screws and I declined as I already have more than I could use in my remaining days. They got dumped, as he was in the same position.

[egaParticipant @ega]

In case anyone is interested here are Clive’s slitting saws:

I suppose it would be possible to grind the set off a standard blade.

PS Still not possible to upload a PDF!

[JasonBModerator @jasonb]

Try putting it in a “document” gallery, works for me.

Those blades are a bit thick for the size of screws I make, 0.8mm or around 30thou is the most common I use.

[ega]

On ega Said:

[…] I suppose it would be possible to grind the set off a standard blade.

Yes … I demonstrated the practicality of that a little while ago

… will post a link to the topic later, if I can find it

MichaelG.

[Clive FosterParticipant @clivefoster55965]

ega

Thats very interesting. I knew of the Starrett 249 saws but had never seen any. Thought they were finer teeth actually.

My sample inspected today and considered good so now time to find some screws. Lets see if my Google Fu is as good as File Handle.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Found it at last … The currently-final post, here:

https://www.model-engineer.co.uk/forums/topic/conventional-hacksaw-blades-in-junior-size/page/2/

MichaelG.

[egaParticipant @ega]

JasonB:

Thanks for the tip.

I agree that the Starrett blades seem quite thick and a finer pitch would be easier to start on the cut, no doubt what Clive had in mind.

MichaelG:

Your photo is a rather nice demonstration of the wave set of these blades.

[ega]

On ega Said:

MichaelG:

Your photo is a rather nice demonstration of the wave set of these blades.

Thanks, ega … that’s as I hoped

The flattening is a little slow and ‘iterative’ when using a hand-held Eze-Lap, but it works nicely …

It would be a doodle for someone with a surface-grinder and a magnetic chuck.

MichaelG.

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Edit: __ This was my ‘weapon of choice’

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[david bennett 8Participant @davidbennett8]

The now vintage Eclipse 4S tool included various thicknes’s

 

of slotting saws. Still available occasionally at auction.

dave8

[bernard towersParticipant @bernardtowers37738]

Id be interested to know how you would do that Michael, I sat at my S/G for a while and thought it difficult.

[bernard towers]

On bernard towers Said:

Id be interested to know how you would do that Michael, I sat at my S/G for a while and thought it difficult.

I would take an appropriate thickness of shim-stock and lay the flat portion of a hacksaw blade upon it, on a long magnetic chuck then just gently grind. Flip over and do the same on t’other face.

The wavy pattern that I produced manually should appear as-if-by-magic

… am I missing some hidden trap ?

MichaelG.

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Note: __ The majority of the blade is flat, the wavy set is confined to quite a narrow band:

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[bernard towersParticipant @bernardtowers37738]

In the original post it stated that the screws were down a hole so why do you need to be slotting when the screw just needs a 10 thou cut off the dia?

[Clive FosterParticipant @clivefoster55965]

Bernard

The holes are very shallow. Perhaps 10 or 15 thou showing above the sharp edged countersunk screws originally used. Depending on the detail proportions of the heads on the screws I’ve ordered I may just be able to trim a bit off the top so things fit in the hole without loosing too much of the slot. Or I may have to deepen the slot a little so the screw driver has something to bite on.

Fortunately only about 8 of the screws are that critical as holding moving parts of the action together. For the rest we may be able to get away with running the countersink deeper. For those holding parts of the action together I’m also going to have to take the tips off the screws so they don’t stick out the other side. Just as the original builder did!

Given that the piano was made in the 1780’s I’m impressed by both the tight tolerances it is made to and the consistency of the screws.

Clive

[Graham MeekParticipant @grahammeek88282]

If you are worried about about the raw edge of the screw showing above the plate. Then why not Dome the screws?

This will remove the offending edge yet still retain the depth of slot for much of its width. This used to be a common practice years ago, with screws being produced this way as standard.

Regards

Gray,

[Graham Meek]

On Graham Meek Said:

[…] This used to be a common practice years ago, with screws being produced this way as standard.

Known by Nettlefolds as ‘Raised’

MichaelG.

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profile illustrated here: https://www.rodnaylor.com/shop/restoration-materials/restoration-materials-veneer-other/nettlefolds-screws-number-3-x-38-raised-x-50/

[Graham Meek]

On Graham Meek Said:

If you are worried about about the raw edge of the screw showing above the plate. Then why not Dome the screws?

This will remove the offending edge yet still retain the depth of slot for much of its width. This used to be a common practice years ago, with screws being produced this way as standard.

Regards

Gray,

Unfortunately Nigel says the critical ones in the action can’t be proud out the wood because it would interfere with something. Not enough material to alter the holes either. Frankly I’m surprised that its survived given how skinny the parts are. Moving parts of the action so absolute minimum of wood used to keep them as light as possible. Three sets are broken. Nigel says reproducing them is going to be interesting.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Regarding the ‘flattening’  of Red-Stripe blades …

For what it’s worth:

Starrett’s nominal dimensions for the 1232 are given here:

https://www.starrett.co.uk/product-category/pta-hand-saw-blades/hand-hacksaw-blades-frames/redstripe-hand-hacksaw-blades/

and I measure the original kerf at about 1.02mm +/- 0.02

[ using the reasonably-trusty digital caliper at several locations on one randomly selected new blade ]

MichaelG.

 

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