التعاون

فنون

الجمال والعناية

حِرَف

الثقافة والتاريخ

ترفيه

البيئة

الطعام والمشروبات

الهندسة العكسية

العلوم

رياضة

التقنية

الأجهزة القابلة للارتداء

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)

أنشأه

Charlie

19. أكتوبر 2026

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).

متقدم

2-3 days

التعليمات

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.

المواد لهذه الخطوة:

الزجاج البصري1 as required

الأدوات المطلوبة:

منشار الألماس

الكيروسين

قدمة رقمية 6 بوصات

نظارات أمان

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.

الأدوات المطلوبة:

قرص الطحن الحديدي

طقم حبيبات كربيد السيليكون الكاشطة

مقياس الزوايا

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.

الأدوات المطلوبة:

قرص الطحن الحديدي

طقم حبيبات كربيد السيليكون الكاشطة

شمع البارافين

شمع النحل

صفيحة تسخين

قدمة رقمية 6 بوصات

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.

الأدوات المطلوبة:

صفيحة تسخين

شمع البارافين

شمع النحل

جبس باريس

الأسمنت البورتلاندي

حبيبات شمع العسل

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.

الأدوات المطلوبة:

قرص الطحن الحديدي

طقم حبيبات كربيد السيليكون الكاشطة

عدسة صائغ

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.

الأدوات المطلوبة:

زفت قطران الخشب

صمغ الصنوبر الراتنجي

أحمر الصائغ

آلة الصقل البصري

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.

الأدوات المطلوبة:

سطح بصري مستوٍ (مرجعي)

موقد بنزن

ملح

عدسة صائغ

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.

الأدوات المطلوبة: