We hold melamine tube ID tooling in stock so you can move from drawing to finished part quickly, without the lead time and cost of new tooling. This page lists the stock inner diameters, explains how to read a melamine tube drawing, and shows how custom tooling works when your size is not on the shelf.
Why Stock ID Tooling Matters
Melamine tube is rolled on a mandrel, so every inner diameter needs its own core mold. When that mold already exists, your part skips both the tooling charge and the weeks it takes to make and prove a new one. For development builds and aftermarket replacement, that difference decides whether a project stays on schedule. The practical rule is simple: if your drawing sits close to a stocked ID, we can usually run it as a stock size, and you keep the tooling money for the parts themselves.
Stock Melamine Tube Inner Diameters
Common inner diameters kept in stock include 4.5, 5.0, 6.2, 6.3, 6.5, 6.6, 8, 11, 14, 15, 16, 20, 21, 22, 25, 25.1, 26, 27, 28, 30, 32, 38, 42, 44, 67, 68, and 73 mm. If your G5 or G9 melamine tube drawing is close to one of these, we can often produce it without new tooling. The bands below show where each group normally lands.
| Size band | Stock inner diameters (mm) | Where this band is used |
|---|---|---|
| Small | 4.5, 5.0, 6.2, 6.3, 6.5, 6.6, 8 | Communications and compact DC fuse bodies, small instrument fuses |
| Medium | 11, 14, 15, 16, 20, 21, 22, 25, 25.1, 26, 27, 28, 30, 32 | EV battery, inverter, and charger fuses, PV string fuses |
| Large | 38, 42, 44, 67, 68, 73 | Industrial and high-current fuse bodies, busbar and connector housings |
Note the two odd values in the list, 25.1 and 6.2 mm. They exist because tooling follows real drawings rather than round numbers, and a customer needed that exact fit. It is worth sending your actual ID rather than rounding it to the nearest whole millimeter, because a 0.1 mm shift can change how the cap seats.
Reading a Melamine Tube Drawing
Most quotes that come back slow are slow because the drawing was incomplete, not because the part was hard. Six dimensions decide almost everything.
| Drawing item | Why it matters | What goes wrong if it is missing |
|---|---|---|
| Inner diameter and tolerance | Sets the mandrel and the fuse element clearance | Quote has to assume a nominal, then the part will not fit |
| Outer diameter or wall thickness | Drives wall build-up and dielectric strength | Tube comes in under-strength or oversize for the cap |
| Length and cut tolerance | Controls seating depth and contact travel | Assembly needs rework or shimming |
| End finish | Square, chamfered, or deburred | Burrs foul the contact and cause tracking marks |
| Machined features | Openings, threads, tapers, multi-hole work | Second operation cannot be planned or priced |
| Grade | G5 or G9, and the duty behind it | Grade is guessed and temperature margin is unverified |
Custom Tooling and How the Cost Is Returned
If your size is not stocked, we build the tooling from your drawing. To reduce the investment, the tooling cost is returned to you in goods of equal value once a certain order quantity is reached. That means you get the exact finished part without carrying the full tooling cost, and the effective part price falls as volume builds.
| Situation | Tooling position | Best route |
|---|---|---|
| Drawing matches a stock ID | No tooling charge | Order against the stock size, shortest lead time |
| Drawing is close but not exact | Often no tooling, subject to tolerance review | Send the drawing and ask us to check against the stock list |
| New size, recurring demand | Tooling charged, credited back at agreed quantity | Confirm the credit quantity before the first order |
| New size, one-off prototype | Tooling charged | Ask whether a nearby stock ID can be machined to the drawing instead |
Machining Features We Hold
- Various openings and cutouts
- Threads
- Chamfers and tapers
- Multi-hole machining
Precision machining on digital automatic lathes ensures the tube fits the rest of your assembly. Because the tube is machined after cure, features should be dimensioned from a stable datum rather than from a raw cut edge, or the position will drift from part to part.
What We Need to Quote a Stock or Custom Size
- Drawing or a dimensioned sketch with ID, OD or wall, and length.
- Grade, G5 or G9, plus the working voltage and fault level it must survive.
- Quantity for the first order and the expected annual volume.
- Any machined features, with the reference datum marked.
- Target date, so we can tell you whether stock or tooling is the faster route.
Why Source From a Direct Manufacturer
Tianze Electrical builds G5 and G9 melamine tubes from electronic-grade glass cloth and melamine resin, cured and demolded for EV fuses, PV fuses, and 5G communication fuses. Production is ISO 9001 certified, with SGS material testing available. Because rolling, curing, and machining sit in one plant, the bore tolerance and feature geometry we quote are the ones production can actually hold at volume. If you want the process behind the sizes, see the G5/G9 melamine tube production line article.
Frequently Asked Questions
Q: Do you charge for tooling up front?
A: There is an initial tooling cost, which is returned as goods of equal value once the agreed quantity is reached.
Q: How fast can I get a stocked size?
A: Stocked IDs ship quickly; custom sizes and machining follow tooling and production scheduling.
Q: My drawing is 6.4 mm ID. Is that stocked?
A: 6.4 mm is not on the list, but 6.2, 6.3, 6.5, and 6.6 mm are. Send the drawing and the fit requirement and we will confirm whether a stock core can hold your tolerance.
Q: Can you supply a size outside the list without new tooling?
A: Sometimes. A stock core can be machined down where the wall allows, so it is always worth asking before assuming a tooling charge.
Send your drawing to sale@fusestube.com, or see the G5/G9 melamine tube page to start from the finished product.
