Stainless steel reducing bush (reducer), male/female 316, BSP threaded

$4.00

Tax included Shipping calculated at checkout.

Product variants

Shipping and Delivery

Product Type	Delivery Method	Preparation Time	Transport Time	Delivery Time
All Parts	Pickup Point	0 to 3 days	3 to 6 days	3 to 9 days
All Parts	Home Delivery	0 to 3 days	3 to 5 days	3 to 8 days
Tubes > 90cm	Home Delivery	0 to 3 days	3 to 5 days	3 to 8 days
Tubes < 200cm	Home Delivery	0 to 3 days	3 to 5 days	3 to 8 days
Tubes > 200cm	Home Delivery	0 to 6 days	6 to 10 days	6 to 16 days
Assembled Products	Home Delivery & Pickup Point	0 to 5 days	(see methods)	3 to 11 days

* Tubes longer than 90cm cannot be delivered to a pickup point

For orders of more than 50 units of the same item or more than 100 kg, restocking may exceptionally extend the delivery time by up to 10 working days.

For confirmation of delivery times on specific items, please send us a message

Stainless steel reducing bush, male/female 316, threaded BSP to ISO 7-1: R taper male at the large end, Rp female at the small end. This reducer screws into a tapped port to bring it down to a smaller size, in 27 size pairs from 1/4" × 1/8" to 3" × 2"1/2 (DN8 × DN6 to DN80 × DN65). It is rated PN 20 up to 40 °C and drinking water compliant, for all fluids compatible with stainless steel.

Description of the stainless steel BSP reducing bush

In plumbing, this threaded stainless steel pipe fitting changes diameter with no welding or soldering. The part is investment cast (lost wax) in CF8M (AISI 316) stainless steel. It is designed, manufactured and inspected to ISO 4144.

The size pair is read male end first: a 1" × 1/2" (French size 26x34 × 15x21, i.e. DN25 × DN15) screws into a 1" Rp tapped port and takes a 1/2" R male thread. The head with flats, opposite the male end, takes the spanner.

Stainless steel reducing bush: technical specifications

Material	CF8M (AISI 316) stainless steel
Manufacture	Investment casting (lost wax)
Standard	Designed, manufactured and inspected to ISO 4144
Thread	R male (taper), large size; Rp female (parallel), small size, to ISO 7-1 (BSP, R series). Not compatible with NPT
Connection	Male/female
Nominal pressure	PN 20: 20 bar from −20 to 40 °C, lower above that
Temperature	−20/+220 °C, permissible pressure reduced above 40 °C
Fluids	All fluids compatible with stainless steel
Sizes	27 size pairs, from 1/4" × 1/8" to 3" × 2"1/2
Compliance	4MS; drinking water: French order of 25 June 2020

Pressure and temperature

PN 20 applies from −20 to 40 °C. Above that, the permissible pressure falls. Values marked ≈ are read from the pressure/temperature curve in the technical data sheet.

Temperature (°C)	Max. pressure (bar)
−20 → 40	20
100	≈ 16.5
150	≈ 15
220	≈ 13.5

Certification and compliance

According to the technical data sheet for the series:

4MS: compliant with the 4MS requirements, the harmonized European rules for materials and products in contact with drinking water.
Drinking water: compliant with the French order (arrêté) of 25 June 2020 on metallic materials and products in contact with water intended for human consumption.

Uses and installation advice

This reducing bush is used on drinking water systems and on circuits carrying fluids compatible with 316 stainless steel. To join two male threads, choose a stainless steel female/female reducing coupling; to join two tapped ports, a stainless steel male/male reducing nipple. Check fluid compatibility and the permissible pressure at the working temperature.

Thread sealing: each Rp/R joint seals on the threads, using PTFE or jointing compound suited to the fluid and the working temperature.
Galling: with stainless steel on stainless steel, the thread can gall. Screw in gradually, without forcing.
Tightening: tighten the reducing bush with an open-ended or adjustable spanner on the flats of its head, not with pipe grips or pliers, which mark stainless steel.
Dissimilar metals: on a water system, stainless steel forms a galvanic couple with galvanized steel or cast iron. On the brass side, with few exceptions, our flat-seal and conical-seat fittings are threaded to ISO 228-1 (BSPP, parallel), neither R nor Rp.

Technical drawing

Dimensions (mm)

Dimensions in millimetres, PN in bar, weight in kilograms. R: male thread (large end). Rp: tapped thread (small end). ØA: bore at the male end. B: dimension across the flats of the head. L1: depth of bore ØA. L2: length of the male end, excluding the head. L3: overall length. Dimension L2 for the 1"1/4 × 1/2" and the 2"1/2 × 1"1/2 is not currently available: contact us if you need it.

R × Rp size	French size	ØA	B	L1	L2	L3	PN (bar)	Weight (kg)
1/4" × 1/8"	8x13 × 5x10	8.5	15	10	12	19	20	0.011
3/8" × 1/8"	12x17 × 5x10	11	19	14	14.5	21	20	0.023
3/8" × 1/4"	12x17 × 8x13	11	19	10	14.5	21	20	0.019
1/2" × 1/8"	15x21 × 5x10	15	22.5	17.5	17	24	20	0.038
1/2" × 1/4"	15x21 × 8x13	15	22.5	14.5	17	24	20	0.034
1/2" × 3/8"	15x21 × 12x17	15	22.5	14	17	23.5	20	0.029
3/4" × 1/4"	20x27 × 8x13	20	29	17	18	26	20	0.064
3/4" × 3/8"	20x27 × 12x17	20	29	17	18	26	20	0.058
3/4" × 1/2"	20x27 × 15x21	20	29	16.5	18	26	20	0.047
1" × 1/4"	26x34 × 8x13	26	34.5	17.5	18	27	20	0.098
1" × 3/8"	26x34 × 12x17	26	34.5	17.5	19	27	20	0.091
1" × 1/2"	26x34 × 15x21	25.5	34.5	17	19	27	20	0.083
1" × 3/4"	26x34 × 20x27	26	34.5	13.5	19	27	20	0.067
1"1/4 × 1/2"	33x42 × 15x21	35	44	18	–	30	20	0.148
1"1/4 × 3/4"	33x42 × 20x27	34.5	43.5	18	20.5	30	20	0.139
1"1/4 × 1"	33x42 × 26x34	34.5	44	13.5	21	30	20	0.116
1"1/2 × 3/4"	40x49 × 20x27	40	49.5	19	21.5	31	20	0.193
1"1/2 × 1"	40x49 × 26x34	40	50	16.5	22	31	20	0.175
1"1/2 × 1"1/4	40x49 × 33x42	40	50	14.5	22	31	20	0.119
2" × 3/4"	50x60 × 20x27	52	62	22.5	25	35	20	0.330
2" × 1"	50x60 × 26x34	51	61	18	24.5	34	20	0.329
2" × 1"1/4	50x60 × 33x42	51.5	61.5	19.5	26	35	20	0.275
2" × 1"1/2	50x60 × 40x49	51.5	61.5	17.5	26	35	20	0.231
2"1/2 × 1"1/2	66x76 × 40x49	64.5	77.5	24	–	41	20	0.584
2"1/2 × 2"	66x76 × 50x60	64.5	77	22.5	30	39.5	20	0.417
3" × 2"	80x90 × 50x60	77	91	25	33	44	20	0.784
3" × 2"1/2	80x90 × 66x76	77	91	20	33	44	20	0.562

Size conversion

Conversion between the French size designation, inches, DN and the outside diameter stated in the designation (a rounded value, not a pipe dimension).

French size	5x10	8x13	12x17	15x21	20x27	26x34	33x42	40x49	50x60	66x76	80x90
Inches	1/8"	1/4"	3/8"	1/2"	3/4"	1"	1"1/4	1"1/2	2"	2"1/2	3"
DN	DN6	DN8	DN10	DN15	DN20	DN25	DN32	DN40	DN50	DN65	DN80
OD (French size)	10 mm	13 mm	17 mm	21 mm	27 mm	34 mm	42 mm	49 mm	60 mm	76 mm	90 mm

Stainless steel reducing bush: frequently asked questions

Reducing bush, reducing coupling or reducing nipple?

The reducing bush screws into a tapped port and takes a male thread. The reducing coupling takes two male threads. The reducing nipple screws into two tapped ports. At 1" × 3/4", they are 27, 42 and 48 mm long respectively.

Which spanner should be used to tighten the reducing bush?

An open-ended or adjustable spanner, on the flats of the head. Dimension B gives the size across flats: 34.5 mm at 1" × 1/2".

What is the pressure rating at 220 °C?

≈ 13.5 bar, against 20 bar from −20 to 40 °C.

The appearance of the part may vary depending on the batch in stock. Contact us for confirmation.

Payment & Security

Payment Method

Your payment information is managed securely. We do not store or have access to your credit card information.