A housing, valve body, cylinder head or instrument boss with a stripped or cross-threaded M27×1.75 port, and no insert kit for it? None exists at this pitch. The repair is a solid threaded bushing with M27×1.75 inside and M36 or M39 outside, or a counterbore past the damage. Both are made to order, one piece up. No drawing needed: a photo with a rule, the measurements in a message, the old part or its part number is enough; we draw it, you approve, we machine. Get a quote →
Four ways to repair an M27×1.75 port, with the numbers
EKINSUN LTD is a custom parts manufacturer that turns special-pitch threads from two callouts, one piece up. The choice depends on how deep the damage goes and how much wall the housing has around the port. The table gives the outside dimension each repair needs and what it leaves.
| Repair | What is machined | Needs around the port | When it applies |
|---|---|---|---|
| Counterbore past the damage | Mouth bored out 2–3 threads deep; sound thread below is reused | Nothing extra | Damage confined to the first threads; mating part long enough to reach |
| Threaded bushing, M36×2 outside | Port bored and tapped M36×2; bushing with M27×1.75 inside, 3.27 mm wall | At least 44 mm of housing around the port | Stripped full depth; steel, iron or stainless housing |
| Threaded bushing, M39×2 outside | Port bored and tapped M39×2; bushing wall 4.77 mm | At least 47 mm of housing | Aluminium housings, where more wall in the bushing carries the torque |
| Press-fit plain bushing, 33–34 mm outside | Port bored to size; bushing pressed in with retaining compound, thread cut inside | At least 40 mm of housing | Thin walls or where a large tap cannot be run |
Why M30 and M33 cannot carry an M27×1.75 thread
A bushing needs wall between its outside thread root and the 27 mm female thread inside. The table applies the ISO basic profile (male minor d3 = d − 1.2269 P) to the outside threads a repairer reaches for first.
| Outside thread of the bushing | Minor diameter d3 | Wall around 27 mm | Verdict |
|---|---|---|---|
| M30×1.5 | 28.16 mm | 0.58 mm | Cannot be made |
| M30×2 | 27.55 mm | 0.27 mm | Cannot be made |
| M33×2 | 30.55 mm | 1.77 mm | Cannot be made |
| M36×2 | 33.55 mm | 3.27 mm | Workable |
| M36×3 | 32.32 mm | 2.66 mm | Workable |
| M39×2 | 36.55 mm | 4.77 mm | Workable |
| M39×3 | 35.32 mm | 4.16 mm | Workable |
Why there is no insert kit for this pitch
Wire thread inserts, solid key-locked inserts and their taps are made to the ISO 261 pitch list. M27 inserts are catalogued at ×3 coarse and, from some makers, at the listed fine pitches; 1.75 mm is not on the list at 27 mm, so no insert, no special tap and no installation tool exists. That leaves machined repairs, which is not a disadvantage: a solid bushing gives a full-depth, gauged thread in the material you choose.
Bushing specification
| Feature | As made |
|---|---|
| Inside thread | M27×1.75-6H, full depth, gauged go/no-go with our own plug gauge |
| Outside | M36×2, M39×2 or plain press-fit 33–34 mm, cut in the same setup as the inside thread |
| Length | The original full-thread depth plus 2–3 mm; flush or with a locating flange |
| Retention | Retaining compound, flange with two screws, or interference fit |
| Material | 316 stainless (1.4404) for wet and chemical ports, 304 (1.4301) for dry ones, 42CrMo4 or C45 for loaded steel housings, brass for water, aluminium bronze for 6061 or 7075 aluminium housings |
| Lead-in | Chamfer at the mouth to guide the mating part and clear any bruised thread on it |
| Documents | Drawing before machining, material certificate with the parts |
What we need from you
Housing material; depth available under the port; wall thickness around it; whether the port must seal and against what; a photo of the damage with a rule across it. From that the repair route is chosen and drawn, and the quote follows within 12 hours. If the mating part is available, send it or its callout so the bushing thread is gauged against what will actually screw in.
Price, lead time, delivery
There is no list price for a special-pitch part; a single piece starts from €65 and is quoted within 12 hours. One to a few dozen pieces ship in 5 working days, 50 to 500 in 15 working days, delivered DDP to your door with duties in the quote. The first piece is the sample; repeat orders run to the same drawing, with 500-piece and 1,000-piece runs priced lower per piece.
Where thread-repair catalogues stop at M27×1.75
| What you need | In the catalogue? | What to do |
|---|---|---|
| Wire insert kit for M27×3 | Yes | Buy it there, or ask us — we may have it in stock; it does not fit a ×1.75 port |
| Wire insert for M27×1.75 | No | Solid bushing made to order |
| Solid bushing M27×1.75 inside, M36×2 outside | No | Turned to order, MOQ 1 |
| Bushing for an aluminium housing | No | M39×2 outside or aluminium bronze, to your wall thickness |
| Tap for the M36×2 or M39×2 housing thread | Yes | Standard fine-pitch taps; or we cut the housing thread too |
| Re-cut of the port on your machine | — | Counterbore route; we supply the longer mating part if needed |
| M27×1.75 male stud to replace the port entirely | No | Made to order with the bushing |
Related M27×1.75 pages and repair services
Frequently asked
Is there a Helicoil or wire thread insert for M27×1.75?
No. Wire thread inserts are catalogued at the standard pitches, M27×3 coarse and the listed fine pitches; no insert, tap or installation tool exists for a 1.75 mm pitch at 27 mm. A damaged M27×1.75 port is repaired with a solid bushing or by re-machining, both of which are made to order.
How big must the outside of an M27×1.75 repair bushing be?
Large enough to leave wall around the 27 mm female thread. An M30×2 outside leaves 0.27 mm, M33×2 leaves 1.77 mm; neither survives machining or torque. M36×2 leaves 3.27 mm and M39×2 leaves 4.77 mm, so the port is bored and tapped to M36 or M39 and the bushing carries the original M27×1.75 inside.
Can the damaged port be re-cut deeper instead of bushed?
Often. If the damage is confined to the first two or three threads at the mouth, counterboring past them and using the sound thread below keeps the original size; the part that screws in must then have enough thread length to reach. If the whole depth is stripped, a bushing is the repair.
What holds the bushing in the housing?
A threaded bushing (M36×2 or M39×2 outside) is locked with a retaining compound or a flange and screws; a plain press-fit bushing of 33 to 34 mm outside diameter is held by interference plus retaining compound. Both are made with the M27×1.75 thread cut after the outside, so the two stay concentric.
Can you make the bushing from my housing dimensions without a drawing?
Yes. Send the housing material, the depth available under the port, the wall thickness around it and a photo of the damage. The drawing comes back with the quote in 12 hours, MOQ 1, and the bushing ships in 5 working days.
What is the alternative if the housing wall is too thin for a bushing?
Replace the female thread with a male one: a stud or nipple with an M27×1.75 male end is made to screw into whatever sound thread remains or into a new M36 thread, and the mating part connects to the stud. When nothing remains, the housing is sleeved and the sleeve carries the thread.
Send a photo of the port. Housing material, depth and wall around the port are enough to choose the repair. Drawing and quote in 12 hours, MOQ 1. Get a quote →