Preparing and Managing Cutting (Coolant) Fluid

1. Quick Summary

• Do not put plain water in the tank — use "cutting fluid concentrate". Buy a ready-made soluble oil (emulsion) or semi-synthetic concentrate and mix it with tap water at the recommended ratio.
• Golden rule: Add the concentrate to the water, never water into the concentrate. Done the wrong way, the emulsion breaks and forms sludge.
• General ratio: roughly 5–7% concentrate for milling (1:15 – 1:20). Go up to 8–10% for heavy jobs such as steel.
• Rust prevention and pH matter: cutting fluid at the right ratio protects both the bit and your machine's table/ways from corrosion.

2. What Is Cutting Fluid Made Of?

Water by itself is an excellent coolant but cannot be used alone in metalworking: it rusts the machine and the part and does not lubricate. That is why additives are added to water for specific tasks. All of these additives are already included in the concentrate you buy — you do not mix chemicals one by one; you pick the right product and mix it with water.

3. Four Main Fluid Types

Water-miscible (mixed with water) cutting fluids fall into three main groups; there is also a "straight oil" group containing no water. The Raptorex module is designed to work with water-based fluids.

4. Which Type to Choose?

If you do mixed jobs on your machine (aluminum + steel), the most practical starting point is semi-synthetic: it balances lubrication and cooling, keeps the tank clean and lasts longer than emulsion. If you mostly machine steel, a well-lubricating soluble oil (emulsion) or an EP-additized semi-synthetic works well; if you mostly machine aluminum, a low-oil/clear synthetic or a semi-synthetic labeled "for aluminum" gives good results.

Which products are available on the Turkish market?

The examples below introduce commonly available product families on the market (not brand endorsements). They are all industrial oil brands selling "water-miscible cutting fluid"; the series name in the product often tells the type: "MB / emulsion / bor yağı (soluble oil)" generally indicates soluble oil, "semi-synthetic / yarı sentetik" the balanced type, and "synthetic / Syntilo" the synthetic type.

Note: Product series and names are updated over time. Ask for the technical data sheet (TDS) when buying; check that the label says "semi-synthetic / water-miscible cutting fluid, for CNC milling, nitrite-free".

Where to find them?

• Industrial oil dealers / distributors: Castrol, Petrol Ofisi, Fuchs, Belgin, Shell, Mobil dealers (they provide the TDS and technical support).
• Online petrochemical stores: sites such as turkoilmarket.com, madeniyagfiltre.com.tr; they have "soluble oil / cutting fluid / metalworking fluid" categories.
• Local manufacturers / chemical companies: manufacturers such as Xenol, Bostancı Kimya and Çözüm Petrokimya offer direct sales plus mixing ratio / refractometer factor support.
• Industrial zones: mold-making and lubricant shops in industrial areas such as İkitelli/İstanbul, Ostim/Ankara, İmes and Dudullu keep it in stock; the one closest to you offers the fastest route.
• Marketplaces: search Trendyol/n11 etc. for "cutting fluid / soluble oil / CNC coolant"; however, always verify that the seller sells industrial products and that the product is for metalworking (do not confuse it with car antifreeze/radiator coolant).

5. Water Quality

Water is the main component of the emulsion; therefore water quality directly affects the fluid's life and performance.

• Do not use hard water: high calcium/magnesium breaks the emulsion and causes saponification and foam. Practical upper limit ≈ 20 French degrees of hardness (°F).
• Best results with reverse osmosis (RO) or demineralized water: bacteria growth, foam and corrosion risk drop to a minimum; fluid life extends.
• If you will use tap water: first let the water sit / have it tested in a container; if it is very hard, prefer reduced-mineral water (dispenser/RO).
• Never use seawater, chlorinated or acidic water.

6. Mixing and Ratios

Example calculation for a 50 Lt tank

How should you verify the ratio?

Eyeballing is not enough. An optical refractometer measures the mixture's concentration: a few drops of fluid are placed on the prism and read on the scale. The reading is multiplied by the "refractometer factor" in the product's TDS to convert it to the real concentration (e.g., if the scale shows 4 and the factor is 1.5, the real ratio is 6%). A refractometer is the essential measuring tool of any workshop working with cutting fluid.

7. Selection by Material

The material you machine determines the fluid type and ratio. A wrong match means staining, corrosion or insufficient lubrication.

8. Maintenance and Life

Cutting fluid is not "set and forget"; a small routine extends its life by months and prevents odor/rust/foam problems.

Basic maintenance routine

• Weekly: Measure and note the concentration with a refractometer and the pH (ideal 8.5–9.5).
• Topping-up rule: Top up evaporated water with a weak ready mix (1–2%), not with pure water. This keeps the concentration balanced (adding pure water dilutes the additives and raises rust risk).
• Chip cleaning: The module's chip separator system removes the chips; still, periodically clean the chips that accumulate at the bottom of the tank.
• Long breaks: If the machine will not be used for 1–2 weeks, aerate the fluid in the tank (run the pump briefly) or drain and protect it; bacteria multiply quickly in stagnant fluid.
• Waste: Do not pour spent fluid down the drain; hand it over to municipal/waste oil collection points or your supplier.

9. FAQ

• Can't I just put plain water in the tank? It cools for a short time but rusts your machine and parts and does not lubricate; bit life drops. Always use cutting fluid concentrate.
• Are soluble oil and semi-synthetic the same thing? No. Soluble oil (emulsion) is high-oil and milky white; semi-synthetic is lower-oil, cleaner and longer-lasting.
• Can I make my own cutting fluid at home? Not recommended. Professional fluids are formulated products containing emulsifiers, rust inhibitors, biocides and pH buffers. Mixing "oil + water" at home invites rust and bacteria problems. Ready-made concentrate is both safer and cheaper.
• Why should the fluid be clear for aluminum? Oily/cloudy fluids are more prone to sticking and marking aluminum; low-oil/clear fluids formulated for aluminum cut clean.
• How do I measure concentration? With an optical refractometer. Multiply the scale reading by the factor in the product's TDS.
• How often should I change it? Semi-synthetic lasts 6–12 months with good maintenance; emulsion is shorter (3–6 months). Renew it if there is odor, a pH drop or excessive tramp oil.

10. Safety

• Skin and eyes: Concentrate and used fluid can irritate the skin; wear gloves + protective goggles when handling.
• Mist/fogging: Fluid mist can form at high spindle speeds; ventilate your workshop and do not inhale it for long periods.
• Old-type formulas: Rust inhibitors containing sodium nitrite, used in the past, are banned as carcinogenic. Prefer modern products labeled "nitrite-free".
• Children/home environment: Store the concentrate in its original, labeled container out of children's reach; do not transfer it into food containers.

References

Note: The mixing ratios are general starting values. The ratio and refractometer factor in the technical data sheet (TDS) of the product you use must be taken as the reference.