Jaytee Alloys and Components Pvt Ltd is the leading Lens blocking or CR alloys manufacturer and Supplier in India and used to blocking optical lens blanks to surfacing, grinding & machining to the required optical size into the lens blank. Our lens blocking/CR alloy can be used repeatedly, JAYTEE has been developed a cover flux to minimize the oxidation and dross formation of alloy. by adding that cover flux in Melting pot, the alloy can be reused 20% more and it’s another advantage is, that cover flux kept the constant temperature of melting pot.


Plastic lenses

The lens blocking/CR alloy used for plastic lenses is alloy SM 4747 and SM4752, with a melting temperature of 117°F(47°C) and 117-122°F(47-52°C). Due to the popularity of plastic lens, it is the most common alloy for lens blocking and can also be used for glass lenses. if a higher temperature alloy is used it can be damage the lenses.


  • • Shape: Bar / Stick / Ingot
  • • Melting point:47 and 47--52⁰C
  • • Weight: 1lb, 0.5 kg, 1.0 kg
  • • Brinell Hardness: Approx 14.5
  • • Growth after casting (Shrinkage): Approx 0.0002

In SM7070 with a melting temperature of 158°F(70°C), is another commonly used alloy. However, it has a better bond strength and is used only for glass lenses.

Jaytee Alloys and Components Pvt Ltd have a variety of lens blocking cadmium and lead-free alloys which is non-hazardous for environment and human body which can be used for glass as well as plastic lenses. These offer the advantage of reduced environmental and health concerns.

lens blocking alloys

plastic lens

low melting temperature alloy

Lens blocking

A protective plastic tape is placed over the lens blank prior to mounting the lens blank and surfacing block into the blocker. The blocker contains the molten alloy (approximately 5°F above the liquids temperature of the alloy) until it is forced, by air pressure, between the tape on the lens blank and surfacing block. The alloy is cooled until it solidifies and bonds the lens blank tape to the surfacing block at chilling plate. The surfacing block is then mounted in a chuck and is used to protect the lens during the machining operation. After the machining operation, plastic lenses are removed from the surfacing block by the inertia of knocking the surfacing block on a solid surface. Glass lenses are unblocked by dipping them into a hot water bath. When the alloy melts and the lens is separated from the surfacing block, the alloy settles to the bottom and is recovered by draining it through a valve.

Blocking/ cooling time 20 minutes

Other Shape and Size can be made on customer requirement. Lead free or Leaded alloys are available.

Advantage: We also develop cover flux of theses alloys to reduce dross formation, by using our alloys with our cover flux approx 20% life of alloys will be increase and dross formation will be minimize.

ALLOYS No M.P.(⁰C) M.P.(⁰F) Popular Name TYPE OF BLOCKING LENS Remarks Shape & Size
SM3843 38--43 100--109 -- Mineral +Plastic mercury containment 0.5,1.0Kg bar
SM4747 47 117 CERRO LOW117 Mineral +Plastic Cadmium base 0.5,1.0Kg bar
SM4752 47—52 117--126 CR ALLOY 117 Mineral +Plastic Cadmium base 0.5,1.0Kg bar
SM5456 54--56 129--133 -- Mineral +Plastic Cadmium base 0.5,1.0Kg bar
SM5858 58 136 -- Mineral +Plastic Cadmium & lead free 0.5,1.0Kg bar
SM6060 60 140 -- Mineral +Plastic Cadmium & lead free 0.5,1.0Kg bar
SM6262 62 144 -- Mineral +Plastic cadmium base 0.5,1.0Kg bar
SM5765 57--65 135--149 -- Mineral cadmium base 0.5,1.0Kg bar
SM6165 61--65 142--149 -- Mineral cadmium base 0.5,1.0Kg bar
SM7070 70 158 Cerro Bond Mineral cadmium base 0.5,1.0Kg bar

Customer can be choosing Alloy as per their requirement from the above Table.