How Long Diamond Blades Last: Cost Per Cut Across Stone Types
A $40 blade cutting jasper gives you 200 slabs. That same blade on jade? Maybe 30.
Two points on the Mohs scale shouldn't matter this much. But jasper sits at 6.5, jade at 8.5, and those two points translate to roughly 85% more blade wear per cut. The diamonds embedded in your lapidary saw blade don't negotiate. They just wear down faster against harder material, following laws of physics that don't care about your project budget.
This isn't about which blade to buy—that's already covered in our guide to the best lapidary saw. This is about what happens after you buy it. The slow, expensive truth of blade degradation that most lapidary supply catalogs conveniently omit from their product descriptions.
Diamond blades wear in patterns. Predictable, measurable patterns that change based on what you're cutting. A 10-inch sintered blade slicing through agate behaves completely differently than the same blade working its way through quartzite. The blade doesn't know it's supposed to last "up to 50 hours of cutting time." It just knows whether it's encountering Mohs 7 or Mohs 6.5, and it wears accordingly.
The numbers tell you exactly what to expect—cuts per blade, cost per cut, wear patterns by stone type. Not recommendations. Just the data from workshop setups where people track this stuff because they have to. Because when you're halfway through making cabochons and your blade suddenly starts chattering instead of cutting cleanly, that's not a mystery. That's math catching up with geology.
The Mohs Scale and Diamond Blade Wear
The Mohs scale measures scratch resistance, not cutting resistance, but the correlation between the two is close enough that lapidaries use it as a rough predictor of blade life. A stone that ranks higher on the Mohs scale will generally wear down diamond blades faster. Not proportionally—that's the weird part—but exponentially in some cases.
Diamonds themselves rate 10 on the Mohs scale. You'd think that means they can cut anything below them with equal efficiency. But the blade isn't pure diamond. It's a steel core with diamond particles either bonded to the surface (sintered) or pressed into notches (segmented). The way those diamonds interact with different stone hardnesses creates wear patterns that don't follow a simple linear progression.
Jade at Mohs 8.5 doesn't wear a blade exactly twice as fast as jasper at 6.5. It wears it about six times faster in real-world cutting conditions. The difference compounds because harder stones require more pressure, which creates more friction, which generates more heat, which accelerates diamond bond breakdown. It's a cascade effect that shows up in your blade life whether you're accounting for it or not.
Blade Type Matters More Than Blade Price
A $35 notched rim blade and a $55 sintered blade will have completely different lifespans cutting the same material. The construction method—how the diamonds are attached to the steel core—determines how those diamonds release and refresh during cutting.
Notched rim blades have diamonds pressed into serrated segments around the edge. As the blade wears, entire segments can chip or break off, especially when cutting harder materials. These blades excel at cutting softer stones like turquoise, serpentine, and calcite, where the aggressive cutting action doesn't cause premature segment loss.
Sintered blades have diamonds distributed throughout a metal matrix that's fused to the rim. As the outer layer wears away, new diamonds are exposed. These blades maintain cutting efficiency longer on harder materials because the diamond distribution is more consistent. They're the standard choice for agate, jasper, and quartz—the workhorses of cabochon making.
The price difference isn't about quality. It's about application. A $35 notched blade that gives you 300 cuts through serpentine is performing better than a $55 sintered blade that gives you 200 cuts through the same material. The math only makes sense when you match the blade type to the stone type.
Actual Cut Counts by Stone Type
These numbers come from workshop logs where people track blade performance because they're cutting enough material that blade cost matters. The variation is significant—sometimes up to 40% depending on blade quality, coolant flow, and cutting technique—but the patterns hold across different setups.
| Stone Type | Mohs Hardness | Notched Rim (10" blade) | Sintered Rim (10" blade) | Cost Per Cut (Sintered @ $45) |
|---|---|---|---|---|
| Serpentine | 2.5-5.5 | 400-500 cuts | 300-400 cuts | $0.11-$0.15 |
| Turquoise | 5-6 | 350-450 cuts | 280-350 cuts | $0.13-$0.16 |
| Calcite | 3 | 450-550 cuts | 350-450 cuts | $0.10-$0.13 |
| Jasper | 6.5-7 | 180-220 cuts | 200-280 cuts | $0.16-$0.23 |
| Agate | 6.5-7 | 180-240 cuts | 220-300 cuts | $0.15-$0.20 |
| Quartz | 7 | 150-200 cuts | 180-250 cuts | $0.18-$0.25 |
| Jade | 6.5-7 (Nephrite) / 8.5 (Jadeite) | 80-120 cuts | 120-180 cuts | $0.25-$0.38 |
| Garnet | 6.5-7.5 | 120-160 cuts | 150-220 cuts | $0.20-$0.30 |
| Tourmaline | 7-7.5 | 100-150 cuts | 140-200 cuts | $0.23-$0.32 |
The "cuts" here assume slabs between 1/4" and 3/8" thick—the standard range for cabochon preforms. Thicker slabs reduce the total count proportionally. A 1/2" slab effectively counts as 1.5 cuts in terms of blade wear.
Why Water Flow Changes Everything
Blade wear isn't just about hardness. It's about heat. Diamond bonds break down faster at higher temperatures, and inadequate coolant flow is the fastest way to destroy an otherwise decent blade.
A blade cutting jasper with proper water flow might last 250 cuts. The same blade cutting the same material with insufficient coolant might last 120 cuts. The difference is dramatic enough that lapidaries running production shops obsess over their water systems the way racing teams obsess over engine cooling.
The water does three things: it cools the blade, it lubricates the cut, and it flushes debris away from the cutting surface. When any of these functions fail, blade wear accelerates. A blade that's running hot will glaze—the diamonds get coated with melted stone and metal particles, reducing cutting efficiency. A glazed blade feels like it's suddenly gone dull, but the diamonds are still there. They're just buried.
Some workshop setups report blade life improvements of 30-50% simply from upgrading their coolant delivery system. Not a different blade. Not a different technique. Just more water, delivered more consistently to the cutting surface.
The Hidden Cost of Blade Speed
Faster isn't always better. A 10-inch blade on a trim saw typically runs at 1,725 RPM. That's fast enough to cut efficiently but slow enough that the diamonds don't burn through their bonds prematurely. Some hobbyist setups try to speed things up by running smaller blades at higher speeds—4-inch blades at 3,400 RPM, for instance.
The problem: surface speed matters more than RPM. A 10-inch blade at 1,725 RPM has a surface speed of about 4,500 feet per minute at the rim. A 4-inch blade needs to spin at 4,300 RPM to achieve the same surface speed. When you run a 4-inch blade at 3,400 RPM, you're cutting at about 3,500 feet per minute—noticeably slower, which means more pressure, more heat, and faster blade wear.
The data from workshop tracking logs shows the pattern clearly: blades run at optimal surface speeds last 20-30% longer than blades run too fast or too slow. The sweet spot is around 4,000-5,000 feet per minute for most stone types. Above 6,000 feet per minute, you're generating excess heat. Below 3,000, you're forcing the cut.
When Blades Don't Die—They Just Get Reassigned
A blade that's too worn for precision cabochon work isn't necessarily dead. It's just demoted. Workshops running multiple projects will often keep worn blades in service for roughing cuts where precision doesn't matter as much.
A sintered blade that's down to its last 50-75 cuts for agate might still have 150-200 cuts left in softer materials like calcite or serpentine. The blade isn't cutting cleanly anymore—it's leaving rougher surfaces, requiring more grinding and polishing afterward—but it's still removing material.
This cascading system of blade reuse shows up in commercial shops more than hobby setups. A blade starts life doing precision trim work on expensive materials, moves to roughing cuts on cheaper stones, and finishes its career cutting practice pieces or doing initial shaping on large rocks. By the time a blade is truly dead—unable to cut even soft material efficiently—it's often completed three to four times the number of cuts listed in its "official" lifespan.
The Economics of Blade Choice
Material cost matters. If you're cutting $3-per-pound jasper, blade cost per cut might be your biggest expense after electricity. If you're cutting $40-per-pound jade, blade cost is negligible compared to material waste from poor cuts.
The math shifts your buying decisions. For high-volume work in softer materials, cheap notched blades that you replace frequently make sense. For occasional work in harder materials, expensive sintered blades that last longer justify their cost through reduced blade changes and more consistent cuts.
Some lapidaries cutting exclusively jade or garnet report spending $400-600 annually on blades while cutting material worth $2,000-3,000. The blade cost is roughly 20-25% of material cost. For those cutting softer agates and jaspers, blade cost might be 5-10% of material cost. The percentage determines how much attention you pay to blade maintenance and how quickly you replace worn blades.
Blade Diameter and Cost Efficiency
Larger blades cost more but often deliver better cost-per-cut economics for the same material. A 10-inch sintered blade might cost $45 and deliver 250 cuts through agate. A 6-inch sintered blade might cost $28 and deliver 180 cuts through the same material.
The 10-inch blade: $0.18 per cut. The 6-inch blade: $0.16 per cut. Surprisingly close, but the 10-inch blade can handle larger material and typically runs cooler due to its larger thermal mass. The real advantage appears in cutting depth: a 10-inch blade can cut material up to 3-3/4" high. A 6-inch blade maxes out at 1-3/4".
For cabochon work using pre-cut slabs that are already 1/4" to 3/8" thick, the smaller blade works fine. For initial slabbing of larger rocks, the larger blade becomes necessary. The cost difference isn't about efficiency—it's about capability.
What Blade Manufacturers Don't Advertise
Blade specifications list "up to 50 hours of cutting time" or "suitable for all lapidary applications." These claims are technically true and practically useless. Fifty hours cutting what? Suitable for which applications with which materials?
A blade that lasts 50 hours cutting serpentine might last 8 hours cutting jadeite. Both numbers could accurately represent the same blade's performance, but you'd never know it from the product description. The manufacturer isn't lying—they're just listing the best-case scenario, which happens to be cutting the softest material the blade can handle.
The "suitable for all lapidary applications" claim is even better. Yes, you can cut jade with a notched rim blade designed for softer stones. You'll just replace it six times as often as if you'd used a sintered blade. Both blades are technically suitable. One just happens to be economically rational.
This is why workshop logs matter more than marketing materials. The logs show what actually happens when specific blades meet specific stones over hundreds of cuts. The patterns don't care about advertising claims.
Tracking Your Own Blade Life
The simplest tracking system: mark the blade with a paint pen when you install it, and keep a notepad nearby. Every time you complete a cut, make a mark. When the blade starts chattering or leaving rough surfaces, count the marks.
Do this for three or four blades cutting the same material type, and you'll have a better prediction of blade life for your specific setup than any manufacturer specification can provide. Your water flow, your cutting speed, your stone selection—all of these variables affect blade life in ways that generic specs can't account for.
Some digital-minded lapidaries track blade life in spreadsheets, logging stone type, blade type, blade cost, number of cuts, and cost per cut. After a few months, the patterns become obvious. Jasper costs X per cut. Jade costs Y. Agate falls somewhere in between. The numbers remove the guesswork from blade purchasing decisions.
For workshop setups cutting multiple stone types, this data becomes critical for project costing. You can't bid on a commissioned piece without knowing your actual blade cost for the material involved. "Somewhere between $0.15 and $0.40 per cut" is too wide a range when you're cutting 50 slabs for a single project.
The Reality of Blade Wear
Blades wear predictably. The economics are straightforward once you have your own numbers. A $45 blade that gives you 250 cuts costs $0.18 per cut. Whether that's expensive or cheap depends entirely on what you're cutting and what you're making from it.
The Mohs scale predicts wear patterns with reasonable accuracy. Harder stones wear blades faster. Insufficient water flow accelerates wear. Improper blade speed creates heat that breaks down diamond bonds prematurely. None of this is mysterious—it's just materials science playing out in your workshop.
Track your cuts. Calculate your costs. The numbers will tell you which blades make sense for which materials in your specific setup. Everything else is just marketing.