1. Disc size: match the platen
Start from the platen. Buehler's machines are a good reference: the EcoMet 30 comes with 8, 10 or 12 in platens, the AutoMet 250 with 8 or 10 in, and the AutoMet 300 with 10 or 12 in. Check your own manual or measure.
| Platen | Approx. | Usual disc |
|---|---|---|
| 8 in | 203 mm | 200 mm |
| 10 in | 254 mm | 250 mm |
| 12 in | 305 mm | 300 mm |
Eagle AP806 discs come in 180 / 200 / 250 / 280 / 300 / 350 mm, and other diameters can be made to order. A disc may be slightly smaller than the platen, never larger: a lifted edge catches the specimen.
2. PSA or plain back
| PSA (adhesive) | Plain back | |
|---|---|---|
| Held by | Sticks directly to the platen | Retaining ring, magnetic/adhesive carrier, or a water film |
| Changing | Peel and replace, fast | Refit the ring or re-lay the paper |
| Best for | Automatic preparation, many specimens, frequent changes | Labs with a ring or carrier system, no adhesive on the platen |
| Watch out | Clean adhesive residue so the next disc lies flat | Keep it flat and tight, no lifted edges |
3. Sheets or discs
For hand grinding, sheets laid on a glass or flat plate with water are cheap and flexible. For grinder/polishers, use discs. AP806 is available in both.
4. Grit list: one set, the right system
A standard set for steels is P240 (or P320), P400, P600, P800, P1200, adding P1500–P2000 if you need a finer finish before polishing; softer metals such as aluminum and copper can start finer. AP806 runs from P60 to P10000, so one series covers the whole sequence. See our metallographic grinding sequence guide for the steps.
5. How much to stock: log one week
How many specimens one paper handles depends on hardness, specimen area and load, so "one paper per N samples" figures are unreliable. A better way:
- One rule: replace the paper when it stops cutting and starts to smear. Worn SiC deepens the deformed layer, so saving a paper often costs a re-prepared specimen.
- Run that rule for a week and log, per grit, how many specimens and how many papers.
- Stock in that ratio. The first, highest-removal steps usually use the most paper, but trust your own log.
6. Storage
Paper backings dislike humidity: store dry and flat, keep PSA discs away from heat and heavy stacking, and use opened packs promptly.
7. Want a matched list?
Send us your grinder model and platen diameter, specimen materials and the grits you use. We will match AP806 discs or sheets by diameter, backing and grit, and can send samples first.
Sources: Buehler equipment brochure (platen sizes); steeldata.info grinding guide (grit conversion, when to replace paper); Eagle AP806 product specifications.