Custom Machined Inserts
Resolute Precision Manufacturing produces custom CNC machined inserts: threaded inserts, press-fit inserts, key inserts, and specialty retention hardware, made on Swiss CNC machines and bar-fed lathes. We manufacture custom inserts to your drawing in brass, stainless, steel, and aluminum, from prototype quantities through high-volume production. Direct from the shop, with 24-hour quote response. Request a QuoteWhat a Custom Machined Insert Does
An insert is a machined component installed into a parent part, typically pressed, threaded, or bonded into a drilled or bored hole, to provide a feature that the parent material cannot supply directly. The most common application is a threaded metal insert in a softer parent material such as aluminum, plastic, or wood. The insert provides a durable metallic thread, enabling repeated assembly and disassembly without thread wear in the parent material.
Other insert types include press-fit pins, retention clips, bushing inserts for bearing housings, key inserts for spline and keyway applications, and specialty inserts for electrical conductivity or thermal management.
How Machined Inserts Are Installed
The installation method drives the features we machine on the insert:
- Press-in: knurled OD held to a tight tolerance for a retained interference fit
- Heat or ultrasonic installation: knurled or serrated OD that locks into softened thermoplastic
- Bond-in: grooved OD that gives epoxy a mechanical key
- Threaded-in: external thread, often with a slotted or hex drive, for installation into tapped holes
Your drawing sets the knurl style, groove geometry, and fit. We machine to it.
Swiss CNC for Small-Diameter Custom Inserts
Many threaded and functional inserts are small-diameter components. M3 through M12 threaded inserts, for example, range from 4mm to 15mm in outer diameter. These are ideal parts for Swiss CNC machining: small diameter, with complex features including external knurling, internal threads, external threads, and slotted drive features, all completed in one cycle.
Resolute Precision’s Swiss CNC machines (20mm, 32mm, and 38mm) efficiently produce inserts in this size range, delivering consistent dimensional quality across high-volume production runs.
Specifications
| Machines | Swiss CNC (20mm, 32mm, and 38mm) for small inserts; bar-fed lathes for medium-sized parts |
| Diameter Range | 3/8″ to 3.2″ standard bar-fed; smaller diameters on Swiss CNC machines |
| Internal Threads | Any thread form—metric, unified, pipe, or custom—machined on the ID |
| External Features | Knurled OD for press fit; slotted, hex, or Torx drive; grooved OD for bond-in inserts |
| Retention Features | Diamond knurl, straight knurl, serrated knurl, and grooves for epoxy or press-fit retention |
| Metals | Brass (360) — most common; stainless steel (303/304/316); steel (1018/4140); aluminum (6061) |
| Tolerance | External diameter: ±0.0005″ for press-fit inserts; internal threads: Class 2B or tighter |
| Volume | 1,000 to 5,000,000+ inserts per year |
| Certifications | ISO 9001:2015 |
Common Insert Types and Applications
Resolute Precision produces a complete range of custom inserts for diverse assembly and fastening applications:
- Threaded inserts for plastic and aluminum: brass or stainless with knurled OD for press or heat installation
- Solid-body thread inserts: custom sizes and lengths not available in catalog form
- Key inserts and Woodruff keys: precision steel inserts for torque transmission
- Press-fit dowel inserts: precision diameter stainless or steel inserts for hole reinforcement
- Electrical contact inserts: brass or copper inserts for EMI shielding and grounding applications
- Thermal insert slugs: copper or brass inserts for heat dissipation in plastic housings
Frequently Asked Questions
What is the most common material for threaded inserts?
Brass 360 is the most common material for threaded inserts installed in plastic, aluminum, and soft metal parent parts. It provides excellent machinability, good corrosion resistance, and adequate thread strength for most assembly requirements. Stainless steel is used where corrosion or higher thread strength is required.
What OD tolerance is required for a press-fit insert?
Press-fit inserts require the insert OD to be slightly larger than the parent hole — typically 0.001″ to 0.003″ interference depending on material combination and insert size. Resolute Precision machines press-fit insert ODs to ±0.0005″ to ensure reliable and consistent installation force across the production lot.
Can RPM produce inserts with knurled ODs for installation in plastics?
Yes. Diamond knurl, straight knurl, and custom knurl patterns are standard on our turning centers. Knurling increases the retention force of a pressed or molded-in insert by engaging the parent material across a larger surface area.
What is the minimum insert size RPM can produce?
Our Swiss CNC machines handle inserts from approximately 3mm to 38mm outside diameter. In practical terms, we regularly produce M2×0.4 threaded inserts with a 4mm OD on our 20mm Swiss machines.