Need an M20 to M16 adapter that carries real mechanical load — not a thin gland reducer — in a specific pitch or material? We machine the M20→M16 reducer to order in steel or stainless, with the exact coarse or fine pitch on each end, male-female or double-male. From a sketch, no CAD, one piece up. Get a quote →
Stock gland reducer vs. a custom machined adapter
Search "M20 to M16" and you'll mostly find cable gland reducers — thin brass or nylon parts that step a cable entry down from M20 to M16 and hold a seal. They're cheap and perfect for electrical glands. They are not made to carry mechanical load, and they only come in the one standard pitch (M20×1.5 to M16×1.5, the gland thread).
What we make is the other thing: a solid, load-bearing M20 to M16 adapter turned from steel or stainless, for fixturing, structural joints, sensor and probe mounts, hydraulic blanks, and any mechanical conversion where a gland reducer would shear or strip. And because it's machined to order, the pitch, length, hex and form are whatever your job needs.
Quick test: if your M20 and M16 threads are sealing a cable and never see load, buy a catalog gland reducer. If they hold a fixture, a sensor, a fitting, or anything under torque or tension — or the pitch isn't the standard ×1.5 — you want a machined adapter.
Pitch & material options
Each end is single-point turned to its own pitch and gauged with a thread ring or plug, so both sides thread on cleanly. Standard combinations plus non-standard pitches on request:
| Option | Choices | Notes |
|---|---|---|
| M20 end | M20×2.5 (coarse) · M20×1.5 (fine) · M20×1.0 | Male or female |
| M16 end | M16×2.0 (coarse) · M16×1.5 (fine) | Male or female |
| Form | Male-female · double-male · female-female | To suit your two parts |
| Material | Steel · alloy steel (42CrMo4) · stainless 304 / 316 | Plated or passivated |
| Drive | Hex (across-flats to suit) · or two spanner flats | For wrench tightening |
| Bore | Solid · or through-bore for shaft / fluid / cable | Your call |
Other size adapters we machine
Three forms we machine
Male-Female
M20 male to M16 female (or reverse) — convert or extend a single threaded line.
Double-Male Stud
M20 male and M16 male — join two female parts through one stud.
Female-Female
M20 female and M16 female — a coupling that joins two male parts.
How it's made — and what we need
- Turned from bar — steel or stainless, hex bar where a wrench grip is wanted so the flats come from stock.
- Each end cut to its pitch — M20 end and M16 end single-point threaded, chamfered, then gauged.
- Finished & checked — deburred, edges broken, both threads verified with ring/plug gauges before packing.
- To order it — send a sketch, a photo of the two parts, or just the callouts (e.g. "M20×1.5 male → M16×1.5 male, stainless"). We draw it, confirm, and quote. How ordering with no CAD works →
Will it fit? M20 to M16 checks before you order
A catalogue cable-gland reducer is M20×1.5 female × M16×1.5 male. It will not thread into an M20×2.5 coarse tapped hole, and an M16×2.0 coarse bolt will not go into its M16×1.5 end — the pitches differ, so the thread starts and binds. Check both pitches with a gauge or a known bolt before ordering: if either end is coarse (M20×2.5 or M16×2.0), the adapter is machined, not stocked.
What do I need to connect an M16 fitting to an M20 port?
An adapter with an M20 male end for the port and an M16 female end for the fitting. To fit an M20 gland or fitting into an M16 hole, the reverse — M16 male × M20 female — with enough wall on the M16 end to carry the load, which is why it is turned from one piece rather than built from a thin reducer.
Same M20 to M16 adapter, but coarse pitch, longer, or in 42CrMo4
M20×2.5 instead of ×1.5, 10 mm more length, alloy steel for a loaded joint, or a through-bore for a shaft — quoted as a variant of the same drawing, one piece and up, in 12 hours.
Where the M20 to M16 Catalogue Stops
M20×1.5 to M16×1.5 is a standard gland reduction and you should buy the stock reducer. The list below is what stock reducers cannot do.
| What you need | In the catalogue? | How we machine it |
|---|---|---|
| M20×1.5 female × M16×1.5 male, plain | Stocked | Both are gland standards. Buy it off the shelf unless you need 316, a shorter body or a seal. |
| M20×2.5 × M16×2.0 — coarse ISO on both ends | Rare | Stock reducers follow gland pitches, not coarse ISO. Turned to order. |
| M20×1.0 × M16×1.5 — extra-fine to fine | No | Extra-fine M20 is a machine-tool and instrument thread, not a catalogue gland size. |
| Alloy steel 42CrMo4 for a loaded joint | No | Stock reducers are mild steel or brass. At M20 this pair often carries load rather than just cable. |
| Through-bore for a shaft, fluid or cable | No | Bore diameter and finish to your drawing, cut in the same operation as the threads. |
| Double-male M20 × M16 stud | Thin | Male on both ends; stock lists carry far fewer than female-male bushes. |
| Female M20 × female M16 coupling | Thin | Same reason. Any pitch pair on either end. |
| Across-flats sized to a wrench you already have | No | Catalogue hex is fixed. Tell us the spanner and we cut the flats to it. |
| O-ring groove or bonded-washer face | No | Stock reducers seal on thread alone. |
| Left-hand thread on either end | No | Not a catalogue item. Single-point cut. |
Pitches listed above are the ones this page already covers. State anything else and we cut it.
Frequently asked
Is this the same as an M20 to M16 cable gland reducer?
No. Catalog reducers are thin brass or nylon parts for stepping down a cable entry and holding a seal — fine for electrical glands, not for load. We machine a solid steel or stainless M20→M16 adapter for structural and mechanical jobs, in the exact pitch and form you need. Only need a gland reducer? A catalog part is cheaper.
Which pitches can you cut on an M20 to M16 adapter?
Any standard combination — M20×2.5 or M20×1.5 on the M20 end, M16×2.0 or M16×1.5 on the M16 end — plus non-standard pitches on request. Each end is gauged so both sides thread cleanly. Mismatched pitch is exactly what a custom adapter is for. More on coarse vs fine pitch →
Can I get it male-female, double-male, or female-female?
Yes, all three — male-female to convert or extend a line, double-male stud to join two female parts, female-female coupling to join two male parts. Tell us the gender of each side.
What's the minimum order, and do you need CAD?
MOQ is one piece, no tooling cost, and no CAD needed — a sketch or the two callouts is enough. We draw and confirm before machining and keep the drawing for fast re-orders.
Tell us your two threads. Send a sketch, a photo, or just the callouts (e.g. "M20×1.5 male → M16×1.5 female, 304 stainless"). Free drawing, quote in 12 hours. Get a quote → or browse all custom metric thread adapters.