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Screwdriver: a Flat Blade Forged, Packed at a Low Heat and Tempered Grey (Holford, 1907)
A flat screwdriver is a steel shank flattened to a blade that fits the slot of a screw. H. Holford's 20th Century Toolsmith and Steelworker (1907) says most smiths make them so they twist or break on a hard screw, and gives his cure: forge it from 75-point carbon steel, strike the blade a few good blows on each flat at a low heat, harden it and let the temper run to grey.
His Fig. 60 shows the shape without its handle. He gives no sizes and no handle, which are unknown here; the brine bath is from his chapter on the hardening bath.
Source: H. Holford (1907), pp. 21, 118. Picture: his Fig. 60.
Intermedio
Half a day
Istruzioni
1
1
Read Holford
Read Holford
"Strike it a few good blows on each flat side of the screw driving edge while at a low heat. Then harden and allow the temper to draw to a grey, cool off and you will have a screw driver that will give unlimited satisfaction."
2
2
Forge the shape
Forge the shape
Take good steel of 75 points carbon. Forge it to the shape of Fig. 60: a round shank, flattened at one end to the driving blade and drawn to a pointed tang at the other for the handle. Holford gives no sizes (unknown).
Materiali per questo passaggio:
Barra quadra di acciaio per utensili1 barStrumenti necessari:
Forgia
Incudine
Martello da fabbro
Tenaglie da fabbro
Dimensioni sconosciute
Occhiali di sicurezza
Guanti resistenti al calore3
3
Pack the blade
Pack the blade
At a low heat, strike a few good blows on each flat side of the driving edge.
Strumenti necessari:
Martello da fabbroIncudineForgiaTenaglie da fabbro4
4
Harden and temper grey
Harden and temper grey
Heat the blade end evenly and quench it in the hardening bath. Holford's bath is clean water free from grease, best made into a brine with as much salt as the water will dissolve, kept as large and as cold as possible. Brighten the blade with a file so the colours show, draw the temper to a grey, then cool it off.
Strumenti necessari:
Forgia
Salamoia saturaTenaglie da fabbro
Lima fineGuanti resistenti al calore5
5
Fit a handle
Fit a handle
Fit a handle on the tang. Holford shows the screwdriver without one and does not say what it is made of (unknown).
Materiali per questo passaggio:
Materiale sconosciuto1 handle6
6
History and honest limits
History and honest limits
Holford, a toolsmith writing for blacksmiths and tool dressers, says a good screwdriver is prized by every mechanic, woodworkers most of all, yet few smiths could make one that would not break or twist. His temper table lists the screwdriver at grey, in 0.75 carbon steel.
He gives no sizes, no handle and no heat for hardening; those are unknown here, and the tools are ours.
Materiali
2- Segnaposto
- 1 handleSegnaposto
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