Metal to metal glue

Practical, honest guidance for specifying and sourcing metal to metal glue — written for the buyer, not the brochure.

What Is Metal To Metal Glue (and Why It Matters for Machined Metal Parts)

Material is the first cost and capability decision on metal to metal glue, and the one buyers most often under-spec. The table below is the short version of what a shop weighs before quoting:

Material	Density	Yield (typ.)	Machinability	Buyer note
Aluminum	2.7 g/cm³	~276 MPa	85/100	6061-T6: the default light structural alloy; 7075-T6 nearly doubles yield for aerospace/robotics at a corrosion & cost premium.
Stainless	8.0 g/cm³	~215 MPa	35/100	304 machines with sharp, rigid setups; 316L adds moly for marine/salt; 17-4 PH reaches ~1000 MPa but moves in heat treat.
Titanium	4.43 g/cm³	~880 MPa	20/100	Ti-6Al-4V: ~60% steel density at comparable strength; low conductivity traps heat — rigidity + coolant + coated tools win.
Brass	8.5 g/cm³	~205 MPa	100/100	C360 free-machining benchmark; superb finish for fittings/connectors. Watch EU lead-content (RoHS/REACH).
Copper	8.96 g/cm³	~70 MPa	45/100	C110 conducts but is gummy/BUE-prone; sharp positive-rake tools, lower speed. Use only when conductivity matters.
Inconel	8.19 g/cm³	~1035 MPa	8/100	718: strength-at-temperature + severe work-hardening; budget slower cycles & premium tooling — a capability signal.
Peek	1.32 g/cm³	~100 MPa	50/100	Continuous ~143 °C, inert; machines like a hard plastic — sharp tools, controlled heat, no coolant cross-contamination.
Delrin	1.41 g/cm³	~69 MPa	90/100	POM: stable, low-friction, holds tight tol; can warp from internal stress — gentle clamp, let stabilize before final pass.

A few consequences that show up in your quote:

• Aluminum 6061-T6 is the default for a reason: cheap, stable, fast to cut, and ample at ±0.01 mm. Reach for 7075-T6 only when strength drives the design.
• Stainless costs more to machine (it work-hardens) and demands rigid fixturing, but 316L is non-negotiable near salt or bodily fluids.
• Titanium and Inconel are where quotes diverge most. The number is not the machine; it is tool life, coolant strategy and cycle time. A shop that quotes them cheap is probably not holding your tolerance.
• PEEK / Delrin are polymers with real engineering value (chemical, thermal, friction), not cost-cutting substitutes for metal.

How Metal To Metal Glue Works in Practice

Design for manufacturability is where part cost is won or lost. The principles are boring and non-negotiable:

• Internal corners cannot be sharp — an end mill leaves a radius. Call out a fillet (≥ 0.5 mm) instead of a square corner.
• Hole depth should stay near or below 4× the diameter for twist drilling; deeper holes need gun drills and longer lead times.
• Walls thinner than ~0.5–1.0 mm chatter and distort. Thicker is cheaper and more stable.
• Standard threads under ~M2 / #2 are fragile in soft metals — avoid unless the assembly demands them.
• Tight tolerances cost money on every feature. Tighten only the surfaces that mate or seal; leave the rest at ISO 2768.
• Heat-treated parts move. If flatness matters post-hardening, plan a finish-grind operation and say so in the RFQ.

Materials & Process Options

Before you send the RFQ, run this five-point check:

• Is every tight tolerance tied to a function, or habit?
• Did you name the exact material grade and any cert?
• Are internal corners filleted (no square corners from end mills)?
• Is hole depth within ~4× diameter, or do you need a specialty drill?
• Do you need FAI/PPAP, and did you say so?

Specifying Metal To Metal Glue: Tolerances, Finishes, RFQ Checklist

Metal to metal glue shows up wherever a part must be both precise and produced in quantity: robotics and automation frames, semiconductor and medical fixtures, e-bike and drivetrain components, aerospace brackets, and consumer-electronics housings. The common thread is a tolerance or a material that punishes a sloppy process.

For each of these, the buyer's job is the same: define the function (what must align, seal or bear load), then let the shop propose the cheapest process that meets it. Over-specifying is the quiet budget killer.

Common Mistakes Machined Metal Parts Buyers Make

Material is the first cost and capability decision on metal to metal glue, and the one buyers most often under-spec. The table below is the short version of what a shop weighs before quoting:

Material	Density	Yield (typ.)	Machinability	Buyer note
Aluminum	2.7 g/cm³	~276 MPa	85/100	6061-T6: the default light structural alloy; 7075-T6 nearly doubles yield for aerospace/robotics at a corrosion & cost premium.
Stainless	8.0 g/cm³	~215 MPa	35/100	304 machines with sharp, rigid setups; 316L adds moly for marine/salt; 17-4 PH reaches ~1000 MPa but moves in heat treat.
Titanium	4.43 g/cm³	~880 MPa	20/100	Ti-6Al-4V: ~60% steel density at comparable strength; low conductivity traps heat — rigidity + coolant + coated tools win.
Brass	8.5 g/cm³	~205 MPa	100/100	C360 free-machining benchmark; superb finish for fittings/connectors. Watch EU lead-content (RoHS/REACH).
Copper	8.96 g/cm³	~70 MPa	45/100	C110 conducts but is gummy/BUE-prone; sharp positive-rake tools, lower speed. Use only when conductivity matters.
Inconel	8.19 g/cm³	~1035 MPa	8/100	718: strength-at-temperature + severe work-hardening; budget slower cycles & premium tooling — a capability signal.
Peek	1.32 g/cm³	~100 MPa	50/100	Continuous ~143 °C, inert; machines like a hard plastic — sharp tools, controlled heat, no coolant cross-contamination.
Delrin	1.41 g/cm³	~69 MPa	90/100	POM: stable, low-friction, holds tight tol; can warp from internal stress — gentle clamp, let stabilize before final pass.

A few consequences that show up in your quote:

• Aluminum 6061-T6 is the default for a reason: cheap, stable, fast to cut, and ample at ±0.01 mm. Reach for 7075-T6 only when strength drives the design.
• Stainless costs more to machine (it work-hardens) and demands rigid fixturing, but 316L is non-negotiable near salt or bodily fluids.
• Titanium and Inconel are where quotes diverge most. The number is not the machine; it is tool life, coolant strategy and cycle time. A shop that quotes them cheap is probably not holding your tolerance.
• PEEK / Delrin are polymers with real engineering value (chemical, thermal, friction), not cost-cutting substitutes for metal.

How Zhuohang Precision Machining Factory Approaches Metal To Metal Glue

Here is the straight version on metal to metal glue. Zhuohang Precision Machining Factory runs 100+ CNC machines across 6,800 m² plant in Hengli, Dongguan, backed by ISO 9001:2015 · IATF 16949:2016 (product design excluded) · ISO 14001:2015. For a part like yours, the first move is not a quote — it is a five-minute engineering read of the drawing to flag anything that will cost you later: a tolerance tighter than the function needs, a thin wall that will chatter, a corner an end mill cannot cut. You hear about it before metal moves, not at rejection.

How to decide: a practical framework for metal to metal glue

When the spec sheet is ambiguous, fall back to this four-step loop. It is how a disciplined shop quotes, and how you should evaluate the quote:

1. Function first. List what the part must do — align, seal, bear load, dissipate heat. Every tolerance ties to one of these or it is optional.
2. Pick the simplest process that holds true tolerance. 3-axis before 4-axis before 5-axis; turn before mill-turn; machining before EDM. Each step up is a cost you must justify on the drawing.
3. Name the material by grade, not family. '6061-T6' not 'aluminum'; '316L' not 'stainless'. The grade sets machinability, certs and price.
4. Demand evidence of control. Cpk targets, FAI reports, mill certs. If the shop cannot produce them, the low price is borrowing against your shipment.

An illustrative scenario

To make the trade-offs concrete, consider a representative part — a 200 × 150 × 20 mm aluminum bracket with six M5 bosses on one face and two precision slots on an adjacent face, called out at ±0.05 mm. The thinking is generic and mechanism-based; it is not a specific customer job:

• A 3-axis center machines the top face and bosses in one setup. The two slots on the side need a second setup — acceptable at ±0.05 mm, because the re-clamp error stays well inside the tolerance budget.
• If those slots were called out at ±0.005 mm, the re-clamp alone would risk the number. That is the moment a 4- or 5-axis single-setup cut earns its premium, not because the machine is 'better', but because it removes the error source.
• Material is 6061-T6, so no special tooling or coolant strategy is needed; cycle time is dominated by the pocket milling, not the drilling.

A ready-to-send RFQ snippet for metal to metal glue

Copy this into your inquiry and fill the brackets. A complete RFQ is the difference between a real quote in 24 hours and a guess in a week:

Subject: RFQ — metal to metal glue

1. Part: [name]  |  Qty: [prototype / N pcs]
2. Model: [STEP/IGES attached]  +  2D drawing with dims & tolerances
3. Material: [grade+temper, e.g. 6061-T6]  |  Certs: [EN 10204 3.1 / RoHS / none]
4. Critical tol: [3 tightest, e.g. ±0.005 mm slots]  |  GD&T: [list]
5. Finish: [Ra, anodize/plating, faces]
6. Target date: [ ]  |  FAI/PPAP: [required / not]

Send to Felipe Iglesias — [email protected]

Frequently Asked Questions

What should I send to get an accurate quote for metal to metal glue?

Send the STEP model and a 2D drawing with dimensions and tolerances, the exact material grade and any cert requirement, your three tightest tolerances, surface finish, quantity and target date. Clean inputs are the fastest path to a real number — Zhuohang Precision Machining Factory quotes from the drawing, not a guess.

How do I know a supplier can hold my tolerances?

Ask for a Cpk target (Cpk ≥ 1.33 general characteristics · ≥ 1.33 key characteristics in production; Ppk ≥ 1.67 at launch) and sample first-article inspection reports. A shop that states capability numbers is running a controlled process; one that will not is a risk on every critical dimension.

When is metal to metal glue the wrong choice?

When a simpler process holds your true tolerances in fewer setups. Specifying beyond the requirement is the most common way to overpay — a good shop tells you before cutting, not after.