Big-diameter metric adapters in coarse and fine pitch — M33, M36, M39, M42, M48, M52 — reducing, converting or changing pitch. Where the catalogue stops around M30, we machine each end to your two threads.
Stock metric thread adapters largely run out around M24–M30. Above that — the M33 to M52 range used on heavy hydraulics, machine-tool spindles, large glands and big sensors — an off-the-shelf adapter rarely exists, and almost never in a fine pitch. Because each end is turned independently on a lathe, we machine the exact two threads you need: reduce one large metric to another, convert a large metric to imperial, or change pitch on the same diameter.
For smaller reductions (M10–M30) see custom metric thread adapters and the M30→M24 size page; this page covers the large end of the range.
| Size | Coarse pitch | Common fine pitches |
|---|---|---|
| M33 | M33×3.5 | M33×2, M33×1.5 |
| M36 | M36×4 | M36×3, M36×2, M36×1.5 |
| M39 | M39×4 | M39×3, M39×2 |
| M42 | M42×4.5 | M42×3, M42×2, M42×1.5 |
| M45 | M45×4.5 | M45×3, M45×2, M45×1.5 |
| M48 | M48×5 | M48×3, M48×2, M48×1.5 |
| M52 | M52×5 | M52×3, M52×2, M52×1.5 |
Any size on the left to any other, or to a smaller metric, or to a UNF/BSP/NPT thread — cut to ISO 261 profiles and ISO 965 tolerance classes (DIN 13). Sizes above M52 are machined to your drawing.
A large double-ended adapter, M42×3 male one end, M48×2 female the other, in 4140 for the pressure, with a central hex across flats to torque it. Both threads gauged before it ships.
Fine-to-fine on large diameters is pure turning: M48×1.5 one end, M39×3 the other, concentric to a tight runout so the tool runs true. Alloy steel, hardened seat if the drawing calls for it.
A same-diameter pitch-change adapter — M36×4 female to M36×3 male — so a coarse-threaded body accepts a fine-threaded insert without re-cutting either part.
An M33×2 to M42×4.5 adapter in 316L, sealed on a bonded washer, so the fine-thread sensor seats cleanly into the coarse structural boss.
| Material | Density | Why choose it at M33–M52 |
|---|---|---|
| Alloy steel 4140 | 7.85 g/cm³ | The workhorse — high strength for large clamp loads, heat-treatable |
| Carbon steel (zinc) | 7.85 g/cm³ | General hydraulic and structural large threads, low cost |
| Stainless 316L | 8.0 g/cm³ | Marine, chemical, washdown at size |
| Titanium Gr5 | 4.43 g/cm³ | ~45% lighter than steel where a large thread must stay light |
| Brass | 8.5 g/cm³ | Large electrical or low-load fluid work only |
EN 10204 3.1 material certificate and a dimensional report on request.
No drawing, just the old adapter or the two parts? Send them — we gauge both large threads (size and pitch) and reproduce from the sample. Large fine pitches are easy to mis-read by eye, so we measure rather than guess.
M33 to M52 and beyond — M33, M36, M39, M42, M45, M48, M52 — in coarse and fine pitch. Catalogue adapters stop around M24–M30, so these are made to order.
Yes — each end is turned independently. Reduce M42×3 to M36×3, convert a large metric to UNC/UNF/BSP/NPT, or change pitch on the same diameter.
The diameter looks standard but the fine pitch (M42×3, M48×1.5) isn't stocked as an adapter. Spindles, glands and heavy sensors use fine pitches — only a turned adapter bridges them.
Alloy steel 4140 for high load, carbon steel for general, 316L for corrosion, titanium to save weight. We advise for your torque and environment.
The thread and pitch each end (e.g. M42×3 to M36×3), male or female, parallel or tapered, length, material — or the old adapter. Quote in 24 hours.
Tell us the two large threads and pitches, and the material. Engineers reply in 24h.
// Qty & price
1 pc
Sample price
Confirm fit before a run
3–50
Unit price drops
Setup cost shared
50+
Best price
All tiers quoted upfront
M33–M52, coarse or fine pitch, reduce, convert or change pitch — machined to your two threads. Quote in 24 hours.