Aluminum threads strip. It's not a matter of if — it's when. A threaded insert for aluminum fixes that permanently, and the right type increases thread strength by 150–300% over bare aluminum. Machinists in aerospace, automotive, and general fabrication all rely on the same four or five insert families — the difference is knowing which one matches your load, your budget, and your alloy.
This guide covers every major aluminum threaded insert option, including when a helicoil in aluminum beats a Keensert, what each insert actually costs, and the one drill-size mistake that causes most failures.

Threaded Inserts for Aluminum: Quick Type Comparison

Your insert type determines everything — strength, cost, and whether you can ever remove it. Here's the full picture before we go deeper on each one.

Insert Type	Install Method	Strength Gain vs. Direct Thread	Removable	Price/Unit	Best For
Helicoil (wire coil)	Thread-in	+150–200%	Yes	$0.15–$0.50	Repair, lightweight assemblies
Keensert (key-lock)	Thread-in + keys	+250–300%	Limited	$2–$5	High-torque, structural
E-Z LOK (solid wall)	Thread-in	+180–230%	Yes	$0.50–$2	Production, clean installs
Press-fit / Riv-nut	Press or rivet	+100–150%	No	$0.10–$0.30	Sheet aluminum, thin walls
Timesert (solid bushing)	Thread-in + expand	+200–250%	No	$3–$7	Blind holes, cylinder heads

Helicoil and press-fit win on cost. Keensert and Timesert win on strength. Everything else lands somewhere in between.

Helicoil in Aluminum — When It Works, and When It Doesn't

The helicoil in aluminum is the most common insert in repair situations, and it earns that reputation. It's a coiled stainless steel wire that threads into an oversized, tapped hole — distributing load across more thread surface than bare aluminum ever could.

The part most people get wrong is the drill size. A 1/4-20 Helicoil needs a #7 drill (0.201"), not the standard 7/32" (0.219") — that 0.018" difference determines whether the insert grips or spins out under load.

Helicoil performs best in 6061-T6 aluminum. In softer 5xxx-series alloys, the host material gives before the insert does, which defeats the whole purpose.

The spin-out failure mode is almost always caused by under-tapping on the final pass — rounding the thread crests and reducing engagement. Tap fully, clear chips at every half turn, and use cutting fluid even if the hole looks clean.

Helicoil vs. Keensert — one clear rule: if you need to disassemble the joint more than 50 times, go Helicoil. If load is the primary concern, go Keensert. They're not interchangeable — they solve different problems.

Aluminum Threaded Inserts by Alloy — 6061, 7075, and 2024

Not all aluminum machines the same, and your insert behavior changes with the alloy. Picking the right insert without knowing your alloy is guessing.

6061-T6 is the most forgiving. It works with every insert type at standard manufacturer drill sizes, taps cleanly, and delivers consistent pullout numbers — expect 1,200–1,800 lbf at M6 with a solid-wall insert.

7075 is harder and machines differently than 6061. Tapping it requires sharper taps, slower RPM, and more cutting fluid — the insert OD can run 0.002–0.003" tighter than spec and still seat properly.

2024 and cast aluminum alloys are inconsistent. Cast aluminum has porosity that press-fit inserts can't grip reliably — wire coil inserts like Helicoil outperform solid-wall designs here because they tolerate irregular hole surfaces better.

Aluminum Threaded Inserts: Cost & Decision Logic

Spend based on what your application actually demands — not on what sounds safe. Three tiers cover virtually every aluminum threading job.

Under $0.50/insert → Helicoil or press-fit riv-nut. Right for consumer products, furniture hardware, and assemblies that disassemble fewer than 20 times. Pullout strength in 6061 at M6: 500–1,000 lbf.

$0.50–$2.00/insert → E-Z LOK solid wall or flanged riv-nut. Right for production runs and moderate mechanical loads — motor mounts, enclosure hardware, industrial panels. Pullout: 1,200–1,800 lbf.

$2–$7/insert → Keensert, Timesert, or Fredsert. Justified only for safety-critical joints, aerospace assemblies, or high-cycle applications where failure means liability. Pullout: 2,000–3,000+ lbf.

If you're unsure which tier fits, go one level up. Insert failure always costs more than the insert.

Aluminum Threaded Inserts Installation — The Steps That Actually Matter

Most insert failures trace back to three steps: drill size, tapping technique, and seating depth. Get those right and the insert handles the rest.

Step 1 — Drill the right hole. Every insert brand publishes its own drill size chart — use it, not the standard thread chart. E-Z LOK, Helicoil, and Keensert all require different oversize amounts for the same nominal thread.

Step 2 — Tap with a spiral flute or gun tap. Use cutting fluid on every pass, and turn forward 3/4 turn, then back 1/4 turn to break chips. Don't skip the back-off even when the tap feels smooth — aluminum chips weld to tap flutes and bind on the next pass.

Step 3 — Deburr before inserting. Sharp edges at the hole entrance tilt the insert on entry. A quick pass with a countersink bit or deburring tool keeps the insert perpendicular.

Step 4 — Drive at low speed. Use a drill or driver set below 200 RPM. High speed generates heat that expands the aluminum and causes the insert to seat at the wrong depth.

Step 5 — Torque the fastener to spec. Aluminum is soft enough that over-torquing damages the insert threads on the first assembly cycle. Use the table below.

Torque Reference by Thread Size

Thread Size	Torque (in-lbs)
M3 / #4	4–6
M4 / #8	8–10
M5 / #10	18–20
M6 / 1/4"	30–35
M8 / 5/16"	65–75
M10 / 3/8"	110–120

For heat-set inserts, set your soldering station to 620–640°F. Too hot melts the surrounding aluminum; too cool and the insert won't seat flush.

Threaded Inserts for Aluminium — Metric vs. Imperial

If you're sourcing threaded inserts for aluminium in the UK, Australia, or anywhere outside North America, metric M3–M12 is your default sizing standard. In North America, imperial sizes (#4 through 3/8") remain common, though metric is gaining ground in manufacturing.

There's no performance difference between the two systems — M6 and 1/4-20 deliver equivalent pullout strength in the same alloy and insert type. The only consideration is compatibility with your existing fasteners.

Dual-compatible inserts do exist and simplify inventory when supplying products across both markets. Check the manufacturer's thread compatibility chart before ordering — metric pitch and imperial pitch aren't interchangeable even when the outer diameter looks identical.

Aluminum Threaded Insert Failure — Three Causes and How to Fix Each

Most failures aren't random. They follow one of three patterns, and each one has a clear fix.

Spin-out happens when outer thread engagement is too shallow — the insert rotates with the fastener instead of staying fixed in the aluminum. Fix: extract the insert, re-tap one size up, and install a larger OD insert, or apply medium-strength thread locker to the outer threads before reinstalling.

Pull-out happens when the insert is too short for the applied load — the fastener pulls the insert axially out of the hole. Fix: replace with a longer insert of the same OD, or step up to a key-lock type like Keensert that mechanically anchors against both rotation and pullout.

Corrosion at the interface is galvanic corrosion — the stainless steel insert and aluminum host are dissimilar metals, and moisture acts as the electrolyte. Fix: apply dielectric grease at installation, anodize the aluminum bore before inserting, or switch to a coated insert designed for aluminum compatibility.

Stainless Steel vs. Brass vs. Titanium Insert Material

Insert material matters more in aggressive environments than in controlled ones. Here's where each one wins.

Stainless steel (303/304) is the standard for most aluminum applications. Thread strength runs 80,000–150,000 PSI, temperature stability holds to 800°F, and corrosion resistance handles most indoor and light-outdoor environments. For saltwater or chemical exposure, step up to 316 stainless.

Nickel-plated brass costs less, installs faster, and reduces galvanic corrosion risk compared to stainless. It's the right call for electronics housings, consumer products, and anything with a conductivity requirement. The nickel plating adds 0.0002–0.0005" to the outer dimension — account for that in precision bores.

Titanium is 40–45% lighter than steel and handles temperature swings from -330°F to 800°F without distortion. The 3–5x cost premium over stainless is justifiable in aerospace components where weight savings compound across hundreds of inserts.

Threaded Inserts for Aluminum in Aerospace and Automotive Applications

Aerospace and automotive shops don't over-engineer their insert specs — they've done the failure analysis already. Following their lead saves you from rediscovering the same failure modes.

Aerospace specifies inserts to AS8879 (helical wire) and NAS1130 (solid bushing). Those standards exist because vibration, thermal cycling, and repeated disassembly cause insert failures that standard torque specs alone don't prevent. If your application shares any of those conditions, those insert families are worth specifying regardless of industry.

Automotive defaults to press-fit inserts on high-volume production lines because they install without secondary tooling. European manufacturers favor M6 and M8 in dashboard and engine bay aluminum — phosphor bronze inserts are common wherever electrical conductivity and corrosion resistance both matter.

Frequently Asked Questions

What size drill bit do I need for a threaded insert in aluminum?
Every insert brand specifies its own drill size — always check the manufacturer's chart. Helicoil inserts require a hole about 0.015" larger than the standard thread drill; solid-wall inserts need a hole sized to the insert's OD minus 0.005".

Can I use a threaded insert to repair stripped aluminum threads?
Yes — this is one of the most common uses. Drill out the stripped hole to the insert's specified OD, tap it to the insert's outer thread spec, and install. The repaired joint is typically stronger than the original aluminum thread.

How long do threaded inserts last in aluminum?
A properly installed insert in 6061-T6 handles 500–1,000 assembly/disassembly cycles before measurable thread wear appears, depending on fastener torque. Key-lock inserts like Keensert handle higher cycle counts in high-torque applications.

Do I need thread locker with aluminum threaded inserts?
Not always. In vibration-heavy applications, medium-strength thread locker on the insert's outer threads prevents spin-out without making removal impossible. Skip it if you need to remove or replace the insert later.
 
Pick your insert based on load first, cost second. A $0.25 Helicoil handles 90% of aluminum threading jobs — if you drill and tap it correctly. When load or cycle count climbs, move up a tier rather than hoping the cheaper option holds. Get the drill size right, use cutting fluid, and deburr every hole before insertion. That's where most failed installs actually start — not at the insert, but at the hole it goes into.if you have any needs,feel free to contact us!