Specialinsert 851 Mubux Brass Heat Set Inserts for Plastic, M5, M6 and 10-24

Specialinsert 851 Mubux heat set inserts are short brass threaded bushings that put a reusable metal thread into rigid thermoplastic parts. Made in Italy from natural-finish brass, the 851 series comes in M5, M6 and 10-24 internal threads, with body lengths of just 5 mm or 6 mm so they fit molded housings with limited wall depth. They are used in industrial, professional and Do-It-Yourself work wherever a plastic part needs a screw thread that survives repeated assembly and service.

Key Features

• Brass construction: corrosion resistant, machinable and strong enough for repeated screw insertion and removal.
• Short-series profile: 5 mm (M5) or 6 mm (M6 and 10-24) total length for thin walls and shallow bosses.
• Angled exterior ribs: the outside profile displaces and grips the surrounding plastic as the insert seats, giving high pull-out and torque resistance.
• Three thread options: M5, M6 and 10-24 UNC, so you can match existing metric or imperial hardware.
• No adhesive required: the insert locks in mechanically as the plastic cools around it.
• Designed to limit radial stress in the host part, which helps avoid cracking around the boss.

How Heat Set Inserts Install

The 851 series is intended for rigid, preferably molded thermoplastics and is installed with heat, pressure or ultrasonic equipment. Pick the method that matches the plastic, the part geometry and the volume you are running.

1. Drill or mold the receiving hole to the diameter listed in the Physical Properties below, and confirm the wall around the hole meets the minimum thickness.
2. Set the insert square on the hole with the thread opening facing out.
3. Apply heat with a soldering iron, a heat-set tip or a dedicated press such as the Chem-Set vertical heat press until the plastic around the insert softens.
4. Press the insert flush with the surface in one controlled stroke. Do not twist.
5. Let the part cool before loading the thread. The plastic reflows around the ribs and locks the insert in place.

Popular Uses

• Adding serviceable screw threads to 3D printed and injection molded enclosures
• Electronics housings, control panels and appliance covers that get opened for maintenance
• Automotive interior trim, sensor brackets and under-hood plastic components
• Jigs, fixtures and prototype assemblies that are taken apart repeatedly
• Replacing stripped plastic threads in equipment housings
• Sign, display and furniture hardware where fasteners mount into plastic panels

Physical Properties

M5 (SPE_851_M5_5MM)

• Internal thread: M5
• Outside diameter: 0.28 in (7.1 mm)
• Total length: 0.197 in (5 mm)
• Hole diameter: 0.252 in (6.4 mm)
• Minimum wall thickness: 0.106 in (2.7 mm)

M6 (SPE_851_M6_6MM)

• Internal thread: M6
• Outside diameter: 0.34 in (8.7 mm)
• Total length: 0.236 in (6 mm)
• Hole diameter: 0.315 in (8 mm)
• Minimum wall thickness: 0.118 in (3 mm)

10-24 (SPE_851_10-24_6MM)

• Internal thread: 10-24 UNC
• Outside diameter: 0.34 in (8.7 mm)
• Total length: 0.236 in (6 mm)
• Hole diameter: 0.315 in (8 mm)
• Minimum wall thickness: 0.118 in (3 mm)

• Material: brass, natural finish
• Installation: heat, pressure or ultrasonic
• Host material: rigid thermoplastics
• Country of manufacture: Italy
• Sold individually. Price is per insert.

Choosing Between the Three Heat Set Inserts

Use the M5 when the boss is shallow or the wall is thin, since it needs only a 6.4 mm hole and 2.7 mm of wall. The M6 and 10-24 share the same 8.7 mm body and 8 mm hole, so the choice between them comes down to whether your screws are metric or imperial. Prepare the hole to the current Specialinsert technical sheet and run a test insert in scrap material before committing a production part.

Related Products

Pair these inserts with the Chem-Set Vertical Heat Press for repeatable, square installation. For press-in anchors in stone, solid surface and composite panels, see the Keep-Nut line, also made by Specialinsert.

Questions about hole prep, thread choice or installation equipment? Call Perigee Direct at (817) 381-9398 or email sales@perigeedirect.com.

FOR INDUSTRIAL USE ONLY. Refer to the SDS prior to use.