Kerjasama
SENI
KECANTIKAN & KESEJAHTERAAN
KRAFTANGAN
BUDAYA & SEJARAH
HIBURAN
ALAM SEKITAR
MAKANAN & MINUMAN
KEJURUTERAAN TERBALIK
SAINS
SUKAN
TEKNOLOGI
BOLEH PAKAI
Equilateral Glass Prism: Sawn, Ground and Pitch-Polished
Frankford Arsenal, in F. E. Wright, The Manufacture of Optical Glass and of Optical Systems (1921), Fig. 77 · Public domain (US Government publication)
Charlie

Dicipta oleh

Charlie

19. Oktober 2026DE
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Equilateral Glass Prism: Sawn, Ground and Pitch-Polished

A prism splits white light into its colours, so its faces must be optically flat and its angles true. This is how the US arsenals ground prisms in 1918, as F. E. Wright recorded for the Ordnance Department in 1921: saw a blank from optical glass, rough-grind it on iron disks, set a batch of prisms in plaster, fine-grind, and polish on pitch with rouge. Wright's worked example is a right-angle prism; an equilateral prism has three 60° angles, made the same way. The picture: blocking prisms for rough grinding at Frankford Arsenal (Wright 1921, Fig. 77, public domain).
Lanjutan
2-3 days

Arahan

1

Saw out the blank

Saw a triangular blank from a block of optical glass with a diamond saw, using kerosene as lubricant. Leave several millimetres extra on each face for grinding.

Bahan untuk langkah ini:

Kaca OptikKaca Optik1 as required

Alatan diperlukan:

Gergaji BerlianGergaji Berlian
Minyak TanahMinyak Tanah
Angkup Digital 6 InciAngkup Digital 6 Inci
Cermin mata keselamatanCermin mata keselamatan
2

Rough-grind the faces

Grind one triangular end flat on a rotating iron disk with 90 or 150 mesh grit. Then rough out the three side faces at right angles to it, checking the 60° angles with an angle gauge.

Alatan diperlukan:

Cakera Pengisar BesiCakera Pengisar Besi
Set butir pelelas silikon karbidaSet butir pelelas silikon karbida
Tolok SudutTolok Sudut
3

Grind the ends in a batch

Wax 20 or more prisms by their ground ends onto a heated iron disk and grind the other ends together: 90, 150, then 220 mesh, then smoothing grit. Change grit only when the surface is free of scratches. Regrind to the set thickness.

Alatan diperlukan:

Cakera Pengisar BesiCakera Pengisar Besi
Set butir pelelas silikon karbidaSet butir pelelas silikon karbida
Lilin parafinLilin parafin
Lilin LebahLilin Lebah
Plat PemanasPlat Pemanas
Angkup Digital 6 InciAngkup Digital 6 Inci
4

Block the prisms in plaster

Set the prisms face down in melted paraffin on a flat iron disk and coat their backs with beeswax. Clamp a ring round them, fill with plaster of Paris and a little Portland cement (10 : 1), and let it harden about 16 hours. Cut the plaster back 1/8 in from the prisms and give it two coats of shellac.

Alatan diperlukan:

Plat PemanasPlat Pemanas
Lilin parafinLilin parafin
Lilin LebahLilin Lebah
Plaster ParisPlaster Paris
Simen portlandSimen portland
Pelet Lilin LebahPelet Lilin Lebah
5

Fine-grind

Grind the block on a slightly convex plate with wet flour emery (the part that settles out of water between 10 and 60 minutes). After five minutes check with a magnifier: the faces should have an even velvet finish, slightly hollow by less than 0.001 in.

Alatan diperlukan:

Cakera Pengisar BesiCakera Pengisar Besi
Set butir pelelas silikon karbidaSet butir pelelas silikon karbida
Kanta Pembesar Tukang EmasKanta Pembesar Tukang Emas
6

Polish on pitch

Pour strained pitch with a little rosin 1/4 in deep on an iron tool and cut crossed grooves 1/8 in wide, 1 in apart. Press it true with a rouge-wetted flat. Polish the block with creamy rouge and water on the machine, usually 4–8 hours, running nearly dry at the end.

Alatan diperlukan:

Pic tar kayuPic tar kayu
Damar painDamar pain
Merah penggilap tukang emasMerah penggilap tukang emas
Mesin Penggilap OptikMesin Penggilap Optik
7

Test for flatness

Lay an optical flat on each face and look at the Newton colours in sodium light (salt in a Bunsen flame). Straight bands to the edge, or one colour over the whole face, mean it is flat.

Alatan diperlukan:

Satah optik (rujukan)Satah optik (rujukan)
Penunu BunsenPenunu Bunsen
GaramGaram
Kanta Pembesar Tukang EmasKanta Pembesar Tukang Emas
8

Free, clean, check the angle, repeat

Break the plaster away, clean the prisms with benzene and check each angle with the angle gauge. Correct by hand on a flat tool with smoothing grit. Repeat blocking and polishing for every face, smallest face first.

Alatan diperlukan:

TukulTukul
BenzenaBenzena
Tolok SudutTolok Sudut
Cakera Pengisar BesiCakera Pengisar Besi
Set butir pelelas silikon karbidaSet butir pelelas silikon karbida

Bahan

1
  • 1
    Kaca Optik
    1 as required
    Pemegang Tempat

Alatan Diperlukan

23

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