Thread Insert Selection: HELICOIL vs Keensert vs TIMESERT vs SPIRALOCK

Drive a hardened steel fastener into cast aluminum or magnesium and the parent metal loses. Clamp load climbs, the soft internal threads shear, and the hole becomes scrap. WarrantyWeek’s 23rd Annual Product Warranty Report puts 2025 warranty claims paid by U.S.-based manufacturers at $30.37 billion. Stripped threads that reach the field feed that number.

Thread inserts solve the problem at the joint. They reinforce a soft tapped hole and spread shear load across more parent material. McKinsey reports that annual warranty costs in advanced industries average 2 to 3 percent of product revenues and run as high as 5 percent. Wire-coil, key-locking, solid-bushing, and thread-form-locking inserts each answer a different failure mode. Match the insert to the load before you cut the hole.

 

Component Solutions Group

Component Solutions Group is a Bufab company based in Dayton, Ohio. We supply engineered fasteners and C-parts to OEMs across North America at a 99.9 percent order accuracy rate.

Our teams pair distribution with design-assist engineering, vendor-managed inventory, kitting, sort and containment, and light assembly across 18 industries. We hold ISO 9001:2015, AS9120 Rev B and IATF 16949 registrations plus ITAR, so every lot arrives with the documentation your receiving team needs.

We supply genuine Böllhoff HELICOIL wire-coil inserts and key-locking bushings direct to OEM production floors. We do not distribute TIMESERT, SPIRALOCK, or E-Z LOK.

Pros:

• Vendor-managed inventory keeps insert stock on the line instead of on back order.
• Full material traceability and aerospace-grade documentation on every lot.
• Fragmented C-parts spend consolidates into one engineered supply chain.
• Engineering support on material, finish, and hole preparation before you tool up.

HELICOIL

HELICOIL inserts from Böllhoff created the wire-coil category. Each insert is a rhombic wire form coiled into a spring that reinforces a tapped hole without adding bulk.

The coil expands against the parent material during installation and settles into an interference fit. That contact spreads shear load over a wider area and keeps the parent threads from stripping under torque. Böllhoff builds free-running versions for a true-to-gauge internal thread and screw-locking versions whose polygonal turns clamp the flanks of the installed screw.

Best for: lightweighting programs and high-volume automotive aluminum housings.

Pricing: low unit cost, moderate tooling cost.

Standout features: compact footprint, free-running and screw-locking variants, tang-free options.

Pros:

• Adds almost no weight to the finished assembly.
• Holds the original nominal thread size in the parent material.
• Absorbs thermal expansion stress between dissimilar metals.

Cons:

• Needs a Screw Thread Insert (STI) tap for hole preparation, sized off STI tap drill charts rather than standard ones.
• Classic versions add a tang-removal step that complicates automated assembly.

Keensert

Keensert and Keysert key-locking inserts come from Howmet Aerospace. They are solid one-piece bushings carrying pre-assembled locking keys.

Installers thread the bushing into a standard tapped hole, then drive the external keys down. The keys broach into the parent metal and lock the insert against rotation for good. That construction gives you the highest pull-out resistance of the options here.

Buyers cross-shopping E-Z LOK against Keensert are comparing two different jobs. E-Z LOK solid-wall inserts install with standard taps and adhesive locking, which suits low-volume repair across metal, plastic, and wood. Keensert carries mechanical keys and belongs on structural joints where a broached anti-rotation lock is the requirement.

Best for: high-shear thread repair and heavy structural machinery.

Pricing: higher unit cost, standard tooling.

Standout features: solid one-piece body, mechanical anti-rotation keys.

Pros:

• Highest installed strength and pull-out resistance in the group.
• Uses standard taps rather than STI profiles.
• Positive key lock removes any doubt about back-out under rotation.

Cons:

• Needs more edge distance than a wire coil.
• Adds real weight next to a wire form.

TIMESERT

TIMESERT builds solid-bushing repair systems aimed at aftermarket automotive and fluid-sealing work. The insert carries a flange at the top for positive placement.

Installation runs a proprietary tool through the bushing that cold-rolls the bottom internal threads outward. Those expanded threads bite into the parent material and lock the insert in place with no adhesive. The result seals well, which is why engine shops reach for it on block work and on spark plug blowout repair in aluminum heads.

Best for: aftermarket engine block repair and spark plug thread restoration.

Pricing: moderate unit cost, high proprietary tooling cost.

Standout features: top positioning flange, self-expanding bottom threads.

Pros:

• Reliable fluid-tight repairs on automotive blocks.
• The top flange sets exact depth every time.
• Holds position through high-temperature engine cycling.

Cons:

• Operators must counterbore the parent material to seat the flange.
• Proprietary step-drill tooling raises the cost of entry.

SPIRALOCK

SPIRALOCK, a Stanley Engineered Fastening brand, is a thread form rather than an insert body. A proprietary tap cuts a 30-degree wedge ramp into the root of the female thread.

When the male fastener pulls up under tension, its crests wedge against that ramp and make continuous spiral contact. The radial clearance that lets conventional threads walk loose disappears, and the even load spread cuts the flank scoring that starts thread galling. SPIRALOCK also ships as a threaded insert when the parent material is too soft to tap directly.

Best for: extreme-vibration aerospace, defense, and spaceflight assemblies.

Pricing: low hardware unit cost, high tap and gauge cost.

Standout features: 30-degree wedge ramp profile, continuous spiral contact.

Pros:

• Strong resistance to vibration-induced transverse loosening.
• Distributes clamp load more evenly across engaged threads.
• Drops the need for secondary locking devices or chemical adhesives.

Cons:

• Demands tight control over the internal tapping process.
• Requires dedicated gauge kits to verify the thread form before assembly.

Six Problems That Scrap Castings and Stall Rollouts

Moving from plain tapped holes to engineered inserts changes your process, your tooling, and your purchase orders. Procurement and operations leaders hit the same six problems. Solve them up front and the rollout holds schedule.

Controlling Hole Preparation and STI Tap Drill Sizes

Wire-coil inserts need STI taps that cut a larger diameter at the original pitch, so the drill size comes off an STI chart, not the standard one. Solid bushings use standard taps but demand exact counterbore depth for proper seating. Tap wear shifts pitch diameter long before anyone notices. For HELICOIL specifically, our HELICOIL specification and selection guide lists the insert types, lengths and tooling in more detail.

Drive an insert into an out-of-tolerance hole and you scrap the casting, not just the insert. On a machined aluminum housing that is hundreds of dollars of accumulated value walking into the scrap bin at the last operation. Set tool-life limits and gauge every shift. Our drill hole size calculator for tapped threads gives your process engineers a starting point.

Scaling Installation Without Losing CNC Cycle Time

Manual insertion works for field repair and jams up a production line. Automated wire-coil installation calls for pneumatic tooling and a dedicated tang break-off station, and every one of those stations adds seconds to takt time. A tang that fails to snap clean blocks the male fastener from threading through and stops the cell.

Weigh the low unit cost of wire coils against the capital cost of the installation cell and the cycle time it consumes. On short runs, a key-locking bushing with standard tooling often wins on total cost.

Holding Torque-Out Strength in Magnesium and Lightweight EV Alloys

Torque-out is the insert spinning inside the parent metal. Pull-out is the whole joint lifting. Soft magnesium castings and the thin-wall aluminum alloys common on EV battery enclosures fail in torque-out first, and a bare tapped hole in those materials gives up long before the fastener reaches its rated clamp load.

Specify engaged length and insert type against the torque-out case, not just the tensile rating on the screw. Key-locking bushings and screw-locking coils both add mechanical resistance to rotation that plain threads in soft alloy cannot supply.

Managing Traceability and Certifications

Aerospace and defense contractors need material traceability on every fastener. Chasing certificates of conformance for thousands of stainless inserts drains procurement time and slows inbound receiving. One missing material test report stops the line.

An engineered supply-chain partner delivers each lot with verified documentation attached, which keeps your AS9100 audits short.

Preventing Galvanic Corrosion and Thread Galling at the Insert Interface

A stainless insert in an aluminum casting creates a galvanic couple. Add salt spray or wash-down chemistry and the parent material corrodes around the insert until the joint loosens on its own. Stainless against stainless brings the opposite problem: the mating threads cold-weld and gall on assembly.

Specify material, coating, and lubricant together, not separately. Our design assist engineering team reviews the pairing during the design phase, when a change still costs nothing.

Sourcing Specialty Inserts Without Breaking the Build Schedule

Specialty inserts carry longer lead times than commodity fasteners, and single-sourcing a proprietary system ties your line to one supplier. A tooling change mid-program means requalifying the joint.

Qualify a second source early and hold buffer stock on the high-runners. Vendor-managed inventory removes the guesswork from replenishment.

How to Choose the Right Thread Insert for Your OEM Line

Four inputs decide the specification: parent material hardness, the load case you are protecting against, the vibration spectrum at the joint, and whether installation happens on an automated cell or at a repair bench. Work them in that order. Reviewing threaded inserts against total cost of ownership beats picking on unit price.

Start with the parent material. Cast aluminum and magnesium give up thread strength quickly, so the insert has to add engaged thread area rather than simply fill the hole. Wire coils do that with the smallest footprint and almost no added mass, which is why lightweighting programs default to them.

Then separate torque-out from pull-out and specify against whichever one governs. Key-locking bushings answer both through broached mechanical keys, so they take the heavy equipment and defense structures where edge distance is available and weight is not the binding constraint.

Next, read the vibration spectrum. Thread-form locking prevents vibration-induced transverse loosening and thread galling better than conventional inserts, which is why aerospace and spaceflight programs accept the tapping discipline and gauge kits it demands.

Last, check the installation environment. Repair work on a finished casting favors a flanged solid bushing and its proprietary tooling. A cell running takt time puts the tang break-off station and its cycle-time cost into the business case before the coil gets specified at all.

Run those four inputs against your print before you standardize. Getting the decision right once removes a re-engineering cycle later.

Stop losing production time to thread failure and inconsistent fastener supply. Contact our OEM team to request a quote or request a sample kit, and consolidate your C-parts base into one engineered supply chain.

Frequently Asked Questions (FAQs)

What is the best thread insert for stripped aluminum threads?

For a stripped thread in a cast aluminum housing, a wire-coil insert restores the original nominal size and adds engaged thread area with almost no added bulk, as long as you can run an STI tap. Where the hole is already oversized or the joint carries high shear, a key-locking bushing or a flanged solid bushing delivers more torque-out resistance.

What is the main difference between wire-coil and solid-bushing inserts?

Wire-coil inserts use a rhombic wire formed into a spring that reinforces a tapped hole while adding almost no weight or bulk. Solid-bushing inserts are machined from bar stock. They deliver higher shear strength and install with standard taps, but they need a larger hole and more edge distance.

Which thread insert provides the highest installed strength?

Key-locking solid bushings provide the highest installed strength. Installers drive the mechanical keys down into the parent material, where they broach the surrounding metal and create a physical barrier against both torque-out rotation and pull-out stress.

Can wire-coil inserts handle high-vibration environments?

Yes, particularly in the screw-locking variant. Those inserts carry polygonal turns that clamp the flanks of the installed screw, which keeps the fastener from backing out under dynamic load without any secondary locking device.