Diamond Paste for Precision Lapping and Mould Polishing
Diamond paste carries micron-graded synthetic diamond in a thick carrier that stays where it is applied. That makes it the standard choice for manual lapping and polishing of materials too hard for conventional compounds, including hardened tool steel, carbide, ceramics and glass. It is widely used in mould and die polishing, precision engineering and metallography.
Each syringe is colour-coded by micron grade, from 90 micron for stock removal down to 1/10 micron for mirror finishing. It is available in Medium or High concentration and in 5g, 10g or 20g syringes. The paste is manufactured in the UK.
The carrier is both water- and oil-soluble. It can be used with either the oil-soluble or the water-soluble Lapping Fluid, and residue can be cleaned off with water.
For more on technique, read The Fundamentals of Mould Tool Polishing.
Choose the Right Micron Grade
Each micron grade is identified by a colour on the syringe. Higher numbers cut faster; lower numbers refine the finish.
| Grade | Colour | Choose It For |
|---|---|---|
| 90 micron | White | Heaviest stock removal |
| 60 micron | Orange | Stock removal and heavy stoning marks |
| 45 micron | Purple | Stock removal and initial lapping |
| 25 micron | Mahogany | Surface preparation |
| 16 micron | Brown | Removing the coarse scratch pattern |
| 10 micron | Red | Pre-polishing |
| 6 micron | Yellow | Pre-polishing and refinement |
| 3 micron | Green | Polishing |
| 2 micron | Pink | Polishing |
| 1 micron | Blue | Fine polishing |
| 1/4 micron | Grey | Mirror finishing |
| 1/10 micron | Grey | Final mirror finishing |
Start with the finest grade that removes the existing marks, then move through finer grades, cleaning thoroughly between each one. The table below shows how the grades group into stages.
| Stage | Micron Grades | Use |
|---|---|---|
| Stock removal | 90, 60, 45 | Removing stoning marks and heavier surface defects (60 and 90 micron in paste only) |
| Surface preparation | 25, 16 | Removing the coarse scratch pattern and refining geometry |
| Pre-polish | 10, 6 | Smoothing the surface ahead of polishing |
| Polishing | 3, 2, 1 | Bringing up a polished finish (2 micron in paste only) |
| Fine and mirror finishing | 1/2, 1/4, 1/10 | Final finishing for a high-gloss or mirror surface (1/2 micron in suspension only) |
1/4 and 1/10 micron are both Grey. Check the grade on the syringe label before use.
Medium or High Concentration?
Concentration describes how densely the diamond is loaded in the paste, which affects cutting speed, finish and cost.
| Feature | Medium Concentration | High Concentration |
|---|---|---|
| Typical diamond content | 30–50% | 60–90% |
| Cutting speed | Balanced | Faster |
| Control | Excellent for precision work | More aggressive |
| Best use | General-purpose polishing and mould work | Very hard materials and heavy-duty polishing |
| Cost | More economical | Higher, due to diamond content |
| Availability | Every grade, 5g, 10g and 20g | 1/4 to 90 micron (not 2 micron), 5g and 10g |
Medium concentration is the most widely used choice in mould polishing workshops. Choose High concentration where faster cutting matters more than economy, for example on very hard materials or larger areas.
How to Use Diamond Paste
Use small amounts.
Excess paste adds residue rather than cutting speed. Add Lapping Fluid to keep the paste working instead.
- Prepare the surface. Remove machining and EDM marks with stones or abrasive papers first. See Surface Preparation Before Diamond Polishing.
- Apply a small amount. Dot paste onto the felt, wooden tool or lap.
- Lubricate as needed. Add a little Lapping Fluid, oil- or water-soluble, to stop the paste drying and help carry away residue.
- Work progressively. Move to the next finer grade once the previous scratch pattern has gone.
- Clean between grades. Clean the component thoroughly and use a separate tool for each grade.
Wear safety glasses and suitable gloves, and work in a well-ventilated area.
Diamond Paste or Diamond Suspension?
| Product | Choose It When |
|---|---|
| Diamond Polishing Compound (Diamond Paste) | You are polishing detailed areas with felts, bobs or lapping sticks and want the abrasive to stay where it is applied. Water- and oil-soluble, in 5g, 10g or 20g syringes. |
| Diamond Suspension | You need even coverage on a lapping plate or larger flat surface. Water-soluble, in 100g bottles, using the same grades and colours. |
| Lapping Fluid | You need a lubricant for diamond paste. Oil- or water-soluble, in 250ml, 1 litre or 5 litres. |
| Algalox | You are working on aluminium or other soft non-ferrous metals and a smooth, duller finish is acceptable. |
Need a tool to apply the paste?
Use RODA Mounted Felt Bobs for curved and concave surfaces, Mounted Felt Lapping Sticks for polishing flats and edges, or Wooden Lapping Sticks for refining geometry.
Product Specifications
| Product type | Diamond polishing and lapping compound (paste) |
|---|---|
| Abrasive | Micron-graded synthetic diamond |
| Carrier | Water- and oil-soluble |
| Micron grades | 1/10, 1/4, 1, 2, 3, 6, 10, 16, 25, 45, 60, 90 micron |
| Colour coding | One colour per grade (1/10 and 1/4 micron both Grey) |
| Concentration | Medium or High |
| Syringe sizes | 5g, 10g, 20g (High concentration: 5g and 10g) |
| Compatible lubricant | Lapping Fluid, oil- or water-soluble |
| Applicator required | Yes – felt, wooden or lapping tool, sold separately |
| Manufacture | Manufactured in the UK |
| Unit of sale | Each (one syringe) |
| Typical applications | Mould and die polishing, carbide and ceramic finishing, precision components, metallography and edge finishing |
Need Help Choosing a Grade or Concentration?
Contact Moleroda with the workpiece material and hardness, the current surface condition, the tool or machine you are using and the finish you need.
![Mounted Wooden Lapping Sticks [600x600]](https://moleroda.com/wp-content/uploads/2021/11/woodenbobsL-2.jpg)
