Seven rows, and only one of them is a number about the tool
The parameter block has seven rows. One is the string item = value, left in from a template. Four are commercial: OEM support, country of origin, a model number that is really a piece count, and a coating row that says other. One is an application claim. That leaves a single row that describes the cutting tool itself.
This article reads that one number, and then reads the shank size, which the block never mentions but the description does.
The seven rows as published
| Row as published | Value | What kind of row it is |
|---|---|---|
| item | value | A template header left in place |
| Customized support | OEM | Commercial |
| Place of Origin | China | Commercial |
| Model Number | 11PCS | The piece count, not a model |
| Usage | External Turning Tool | An application claim |
| Hardness | HRA89.5 | The only number about the tool |
| Coating | other | An admission |
Model Number 11PCS is worth a sentence. A model number is how you reorder, how you look up a grade, and how you compare one supplier with another. 11PCS is a quantity. There is no model to quote, so every enquiry about this set starts from a photograph.
Coating: other is at least honest. These are brazed tools with a blue finish on the shank. That finish is an oxide colour, not a cutting coating; the carbide tip itself is uncoated. The word coating in a cutting tool context normally means a PVD layer of a few micrometres on the insert, and none is claimed here.
HRA 89.5 is one end of a see-saw
HRA is hardness on the Rockwell A scale, which is the scale used for cemented carbide because the C scale cannot resolve it. Published grade tables put cemented carbide between roughly HRA 83 and HRA 93. Within that band, hardness and toughness trade against each other through the cobalt content: more cobalt gives a softer, tougher grade that survives interrupted cuts and impact; less cobalt gives a harder, more wear-resistant grade that chips if you shock it.
| What HRA 89.5 sits among | Value | Note |
|---|---|---|
| Soft end of the cemented carbide range | HRA 83.3 | High cobalt, tough, wears fast |
| This listing | HRA 89.5 | Upper middle of the range |
| Hard end of the range | HRA 93.0 | Low cobalt, wear resistant, brittle |
| For scale: HV 1600 corresponds to | HRA 92.0 | Published conversion tables |
HRA 89.5 sits in the upper middle. That is a sensible general-purpose position for a set sold to people who do not know what they will cut. It is not a hard grade, and it is not a tough grade. It is the compromise grade, which is exactly what a mixed eleven-piece set should be.
What HRA 89.5 does not tell you: the grade
A hardness figure is half a specification. The other half is transverse rupture strength, and the third component is the cobalt content, and all three together are what a supplier calls a grade: K10, K20, P20, and the rest of the ISO application classes.
Two carbides can both read HRA 89.5 and behave completely differently, because one is a fine-grain structure and the other coarse. Hardness alone cannot separate them, and hardness alone cannot tell you whether the tool will survive a interrupted cut on a cast iron casting with a hard skin.
There is a second gap worth naming: one hardness value is published for the whole set. Eleven tools that include a parting blade and a pointed tool would normally not all be the same grade. A parting blade wants wear resistance because it rubs in a narrow slot; a roughing tool wants toughness. Whether all eleven tips are the same carbide is not stated, and it is worth asking.
Eight millimetres square, and what that decides
The description gives the tool sizes as 8 cm by 0.8 cm and 12.5 cm by 0.8 cm. Those are 80 mm and 125 mm long on an 8 mm square shank. Eight millimetres is the smallest shank in common use, and it belongs to bench lathes and small hobby machines. On an industrial lathe the toolpost will not even clamp it properly without a spacer.
That is not a defect. It is the machine class, stated in millimetres. What matters is that the shank size decides far more about what this set can do than the carbide grade does.
Deflection: why overhang matters more than power
A square shank behaves as a cantilever. Its resistance to bending is the second moment of area, which for a square section is the side to the fourth power divided by twelve. Fourth power is the reason shank size dominates everything else.
| Square shank | Second moment of area | Rigidity against the 8 mm |
|---|---|---|
| 8 x 8 mm | 341 mm4 | 1.00x |
| 10 x 10 mm | 833 mm4 | 2.44x |
| 12 x 12 mm | 1,728 mm4 | 5.06x |
| 16 x 16 mm | 5,461 mm4 | 16.00x |
| 20 x 20 mm | 13,333 mm4 | 39.06x |
Doubling the side of a square shank multiplies rigidity by sixteen. Going from 8 mm to 12 mm, which is one step up in any catalogue, multiplies it by five.
Now the part that actually bites. Tip deflection is force times overhang cubed, divided by three times the elastic modulus times the second moment of area. Overhang enters cubed, so it is the dominant variable in practice, and it is the one the operator controls.
| Overhang | 200 N | 500 N | 1,000 N |
|---|---|---|---|
| 20 mm | 0.007 mm | 0.019 mm | 0.037 mm |
| 30 mm | 0.025 mm | 0.063 mm | 0.126 mm |
| 40 mm | 0.060 mm | 0.149 mm | 0.298 mm |
| 50 mm | 0.116 mm | 0.291 mm | 0.581 mm |
| 60 mm | 0.201 mm | 0.502 mm | 1.004 mm |
| 80 mm | 0.476 mm | 1.190 mm | 2.381 mm |
Read the table as an order of magnitude with a stated assumption: steel at 210 GPa, a static point load, no toolpost compliance, no workpiece deflection. Real numbers will be worse, because the toolpost and the compound slide both give.
The useful line is the 50 mm one. At half a kilonewton of cutting force the tip moves 0.291 mm, which is ten times a normal turning tolerance. At 60 mm with a kilonewton it passes a millimetre, and the tool is no longer cutting so much as being pushed away. An 8 mm shank wants to live under 30 mm of overhang. If your work needs more reach than that, the answer is a bigger shank, not a better carbide.
The 12 mm comparison
The same cut with a 12 mm shank, at any overhang, deflects one fifth as much. That ratio is constant because it depends only on the section, not on the load or the length.
For a buyer this is the honest framing of the set. Eleven tools at 8 mm for a bench lathe is a good purchase. Eleven tools at 8 mm intended to be pushed hard on a larger machine is the wrong purchase, and no carbide grade rescues it.
The set does more than external turning
The Usage row says External Turning Tool. The radial photograph shows eleven distinct nose shapes, and at least two of them are not external turning tools.
| Tool in the set | What it is for | Covered by the Usage row |
|---|---|---|
| Straight tool | Facing and straight turning | Yes |
| Left-hand offset, two sizes | Turning toward the chuck, shoulders | Yes |
| Right-hand offset, two sizes | Turning away from the chuck, facing | Yes |
| Round nose | Finishing and radii | Yes |
| Thin parting blade | Parting off | No |
| Pointed tool | Threading or chamfering | No |
The thin blade with the narrow flat edge is a parting tool. The pointed one is a threading or chamfering tool. Both are useful, and both are outside the single word the parameter block uses. The set is more capable than its own specification says, which is rarer than the reverse and worth noting.
Brazed, not indexable: the grinding you are signing up for
Every tip in the photographs is a small carbide blank brazed onto a steel shank. That is a different ownership model from an indexable tool, where a screw releases a carbide insert and a new edge is rotated into place in seconds.
With brazed tools there is no rotation. When the edge dulls you grind it, and grinding HRA 89.5 carbide requires a diamond wheel; a conventional abrasive will not touch it. The angles you grind become the angles you cut with, so the tool's geometry after a year is your geometry, not the supplier's.
That is the real cost of this set, and it is not in the price. A workshop without a diamond wheel and someone who can hold an angle should think of these as disposable, not reconditionable. A workshop with both will find eleven brazed tools cheaper to run than the equivalent indexable set.
Two lengths, nine short and two long
The set is nine tools at 80 mm and two at 125 mm. The two long ones are both right-hand offset tools, which makes sense: reach is what you need on a face or a shoulder that the carriage cannot get close to.
Note what the length does to the deflection table. A 125 mm tool clamped at 25 mm has a hundred millimetres hanging out, and at that overhang the numbers stop being useful. The long tools are for light finishing passes, whatever the carbide is capable of.
What is actually in the box, by mass
The description gives the box as roughly 18 by 16 by 3.5 cm. From that and the eleven tool sizes, the contents can be estimated without weighing anything.
| Component | Volume | Mass |
|---|---|---|
| 9 short shanks at 80 mm | 46.1 cm3 | - |
| 2 long shanks at 125 mm | 16.0 cm3 | - |
| All shank steel | 62.1 cm3 | 487 g at 7.85 g/cm3 |
| 11 brazed carbide tips | 2.1 cm3 | 31.7 g at 15 g/cm3 |
| Box interior | 1,008 cm3 | steel fills 6.2% |
Thirty-two grams of carbide and half a kilogram of steel in a box that is mostly air. That is what the product is: a steel set with small carbide tips, not a carbide set. It explains the price and it explains the durability question, because the wear part is a small fraction of the mass.
Three packagings and two sentences
The description says Wooden box packing OR Aluminum box packing. The photographs show a wooden box with brass hinges, an aluminium box with a diamond-pattern lid, and a plain paper box with a foam insert.
Three packagings exist and the text names two. For a buyer shipping these onward, or giving them as a trade item, which box arrives is not a detail. It is a line to confirm rather than assume.
Machine compatibility: mini lathe, and what that means
The description says the set fits ordinary lathes and CNC lathes. With an 8 mm shank, the honest reading is bench and small lathes; a CNC lathe with a standard toolpost will need a reducing holder, and a CNC lathe with a turret will not take a square shank at all without a block.
Fit is a measurement, not an adjective. The toolpost slot on the machine decides it, and the listing gives no tolerance on the shank, so a shank that is slightly oversize will not enter a slightly worn slot.
What to put in the request for quotation
Ten questions. The first three exist because hardness is half a specification, and the rest because the listing has no model number to look anything up against.
| Item to confirm in writing | Why it decides the purchase |
|---|---|
| The carbide grade, not just the hardness | HRA 89.5 is one number; a grade is hardness plus strength plus cobalt |
| Transverse rupture strength | The other half of the see-saw; without it HRA 89.5 is unreadable |
| Whether all eleven tips are the same grade | A parting blade and a finishing tool normally want different grades |
| Tip thickness at the cutting edge | Decides how many regrinds the tool survives |
| Which shape each of the eleven is, by number | The page gives no shape designation at all |
| Shank tolerance and straightness | An 8 mm shank in a worn toolpost rocks before it cuts |
| Whether the shank is hardened or soft | Soft shanks bend and stay bent |
| Which of the three packagings ships | Text names two, photographs show three |
| Angle the tools are ground to as delivered | Brazed tools arrive ground; the angles decide what you can cut |
| Recommended wheel for regrinding | HRA 89.5 will not respond to a conventional abrasive wheel |
Frequently asked questions
What does HRA 89.5 mean?
Hardness on the Rockwell A scale, the scale used for cemented carbide. Published grade tables span about HRA 83 to HRA 93, so 89.5 is upper middle: a general-purpose compromise between wear resistance and toughness. It is not a complete grade, because hardness alone does not define one.
Is HRA 89.5 hard enough for steel?
Hardness is only half the answer; the other half is transverse rupture strength, which the listing does not give. At HRA 89.5 the grade is on the tougher side of the middle, which suits interrupted cuts and general turning. Whether it suits your steel depends on whether the cut is continuous or interrupted, and that is what to put in the enquiry.
What size shank is it?
8 mm square, in two lengths: 80 mm for nine of the tools and 125 mm for two. That is the smallest common shank and it belongs to bench and small lathes. Rigidity scales with the fourth power of the side, so a 12 mm shank is 5.06 times stiffer.
How far can I hang an 8 mm tool out?
Under 30 mm for real work. At 50 mm overhang and 500 N the tip deflects 0.291 mm, which is ten times a normal turning tolerance; at 60 mm and 1,000 N it passes a millimetre. The figures assume steel at 210 GPa and a rigid toolpost, so real deflection will be worse.
Are these indexable inserts?
No. Every tip is brazed onto the shank, so there is no insert to rotate. When the edge dulls it has to be ground, and HRA 89.5 carbide needs a diamond wheel. Budget for that, or treat the set as consumable.
Can I use them on a CNC lathe?
The description says ordinary and CNC lathes, but an 8 mm square shank needs a reducing holder on a standard toolpost and a block holder on a turret. Fit is decided by the toolpost slot, which the listing does not measure.
Why does the parameter block say External Turning Tool?
Because that is one word for eleven different shapes. The photographs show parting and threading tools as well as turning tools, so the set does more than the Usage row claims. The row understates the product, which is unusual and worth knowing.
Key specifications
Frequently asked questions
- What does HRA 89.5 mean?
- Hardness on the Rockwell A scale, the scale used for cemented carbide. Published grade tables span about HRA 83 to HRA 93, so 89.5 is upper middle: a general-purpose compromise between wear resistance and toughness. It is not a complete grade, because hardness alone does not define one.
- Is HRA 89.5 hard enough for steel?
- Hardness is only half the answer; the other half is transverse rupture strength, which the listing does not give. At HRA 89.5 the grade is on the tougher side of the middle, which suits interrupted cuts and general turning. Whether it suits your steel depends on whether the cut is continuous or interrupted, and that is what to put in the enquiry.
- What size shank is it?
- 8 mm square, in two lengths: 80 mm for nine of the tools and 125 mm for two. That is the smallest common shank and it belongs to bench and small lathes. Rigidity scales with the fourth power of the side, so a 12 mm shank is 5.06 times stiffer.
- How far can I hang an 8 mm tool out?
- Under 30 mm for real work. At 50 mm overhang and 500 N the tip deflects 0.291 mm, which is ten times a normal turning tolerance; at 60 mm and 1,000 N it passes a millimetre. The figures assume steel at 210 GPa and a rigid toolpost, so real deflection will be worse.
- Are these indexable inserts?
- No. Every tip is brazed onto the shank, so there is no insert to rotate. When the edge dulls it has to be ground, and HRA 89.5 carbide needs a diamond wheel. Budget for that, or treat the set as consumable.
- Can I use them on a CNC lathe?
- The description says ordinary and CNC lathes, but an 8 mm square shank needs a reducing holder on a standard toolpost and a block holder on a turret. Fit is decided by the toolpost slot, which the listing does not measure.
- Why does the parameter block say External Turning Tool?
- Because that is one word for eleven different shapes. The photographs show parting and threading tools as well as turning tools, so the set does more than the Usage row claims. The row understates the product, which is unusual and worth knowing.