CNC knowledge

Deburring Machining of Hull Parts: 5 Essential Methods

Hull parts trap burrs where a chamfer tool cannot reach: bore exits, groove floors, and long pocket edges. This guide shows how to pick and run deburring machining of hull parts, from in-process control to final edge break, with the parameters and inspection checks that keep edges repeatable.

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Deburring machining of hull parts on a CNC edge break setup

On this page

1
Key takeaways
2
Burr formation in hull part machining
3
Choosing a method for holes, faces, and grooves
4
In-process deburring inside the CNC cycle
5
Manual and mechanical methods that still make sense
6
Step by step: deburring a hull part in the cycle
7
Which deburring method fits which hull feature

Quick answer

Key takeaways

Prevent first, remove secondSharper inserts, climb milling, and a 0.10–0.20 mm edge break in the same setup cut most hull burrs before they form.

Match the method to the featureHoles, faces, and grooves each need a different tool and approach angle. One method will not cover all three.

Deburr before the part movesHandling, stacking, and coolant drying harden burrs and push them into corners. Deburr at the machine whenever the geometry allows.

Inspect the edge, not the partA 10× loupe or a quick 0.05 mm radius check catches the burrs that calipers and CMM probes miss.

Cost sits in the touch laborTool life and cycle time matter, but most deburring cost on hull parts is manual edge work after machining.

Where burrs come from

Burr formation in hull part machining

A hull part is mostly thin walls, long pockets, and intersecting bores. Every time the cutter exits the material, the workpiece edge plastically deforms before it fractures. That folded metal is the burr. On aluminium hull sections it is soft and smears; on 316L or 17-4PH it work-hardens and snaps off as a sharp sliver.

Three variables drive size. The first is edge angle: a 90° exit leaves a heavier burr than a 120° exit because more material is unsupported. The second is feed per tooth. Push too hard and the exit chip thickens; push too light and the tool rubs, which is worse. The third is tool wear. A dull insert raises cutting force by 20–40% and the burr grows with it.

Coolant matters more than most shops admit. Dry cutting aluminium leaves a gummy edge that tears during the next pass. Flood coolant at 4–6 bar keeps the exit zone cool and flushes chips that would otherwise be re-cut into the wall.

So the first method is not a deburring tool at all. It is controlling the cut so the burr stays small enough to remove with a short, repeatable pass.

1
Exit angleAim for 120° or more at bore exits to reduce unsupported material.
2
Feed per tooth0.05–0.12 mm/tooth in aluminium; 0.03–0.08 mm/tooth in stainless.
3
Tool wear limitChange inserts at 0.15 mm flank wear, before burr size climbs.

Feature by feature

Choosing a method for holes, faces, and grooves

Cross-drilled holes are the hardest case. The burr sits on the exit side, inside a bore you cannot see. A back-chamfer tool or a spring-loaded deburring blade reaches it from the far side and cuts a 0.10–0.20 mm edge break in one pass. If the hole is blind, use a bottom-cut chamfer tool and accept a small radius at the floor.

Open faces and pocket rims are simpler. A 90° chamfer mill run at 8,000–12,000 rpm with a 0.15 mm depth of cut removes the exit burr and leaves a consistent edge. Keep the approach tangential, not radial. A radial entry digs a flat spot that shows under anodizing.

Grooves and slots trap burrs on both walls. A small-diameter ball or bull-nose tool following the slot path at 0.05 mm stepover works well on aluminium. On stainless, run the same path twice: once to break the edge, once to blend. A single pass tends to smear rather than cut.

For long hull sections over 1,000 mm, edge break is a finishing operation, not a spot fix. Plan it into the cycle. Trying to deburr a 2,000 mm pocket rim by hand after the part leaves the machine adds hours and inconsistency.

1
Bore exitsBack-chamfer or spring-loaded blade, 0.10–0.20 mm edge break.
2
Pocket rims90° chamfer mill, tangential approach, 0.15 mm depth of cut.
3
Slot wallsBall or bull-nose, 0.05 mm stepover, two passes on stainless.

Process control

In-process deburring inside the CNC cycle

The most reliable method for deburring machining of hull parts is to do it before the part is unclamped. The zero point is already set, the tool is in the magazine, and the geometry is still referenced to the same datums. Once the part comes off, every edge you touch is a new setup.

Program the edge break as a separate finishing pass after the main cut. Use the same toolpath offset by 0.10–0.15 mm and lift the tool 0.05 mm above the floor. On a 5-axis machine, you can tilt the tool 30–45° to reach bore exits that a 3-axis setup cannot. That single tilt often removes a manual operation.

Speed the pass up. Deburring cuts are light, so you can run 20–30% faster than the roughing feed without chatter. On aluminium hull sections, 12,000 rpm and 1,500 mm/min is a reasonable starting point. Watch the chip: it should be a fine, continuous thread, not dust.

Add an M-code pause after the pass so the operator can check one edge with a loupe before the part moves. Two seconds of inspection here saves a rejected part later.

1
Separate finishing passOffset 0.10–0.15 mm, tool lifted 0.05 mm above the floor.
2
5-axis tilt30–45° tilt reaches bore exits a 3-axis setup cannot.
3
Speed up the pass20–30% faster than roughing feed; chips should be fine threads.

When to go manual

Manual and mechanical methods that still make sense

Not every edge suits a CNC pass. Deep cross-holes, internal threads, and cast hull surfaces with draft often need hand work. A curved scraper and a rotary deburring tool with a carbide burr are the standard kit. Work the burr toward the open side, never into the corner, or you fold it deeper.

Abrasive flow machining (AFM) is worth it when a hull part has many small intersecting holes and you need every edge broken to the same radius. The abrasive media passes through the bore and polishes the exit. It is slower per part but consistent, and it reaches places a tool cannot.

Thermal deburring works on steel and stainless hull parts with complex internal passages. The part goes into a chamber, the gas ignites, and the burr burns away in milliseconds. It will not work on aluminium, which melts before the burr does.

Electrochemical deburring is the precise option. It removes metal at the edge without touching the surface, so it suits thin-wall hull parts where a mechanical tool would distort the wall. The trade-off is fixturing cost and the need for a dedicated electrolyte.

1
Hand toolsCurved scraper and carbide rotary burr; work toward the open side.
2
Abrasive flowBest for many small intersecting holes needing a uniform radius.
3
ElectrochemicalFor thin-wall parts where mechanical force would distort the wall.

How to run it

Step by step: deburring a hull part in the cycle

Follow this sequence on the machine before the part is unclamped.

1
Check the tool and the edge angleInspect the insert for flank wear over 0.15 mm and replace it. Confirm the exit angle at each bore is 120° or more. If it is 90°, expect a heavier burr and plan a second pass.
2
Set the edge break depthProgram 0.10–0.20 mm on aluminium and 0.05–0.10 mm on stainless or titanium. Deeper cuts remove more material than the drawing allows and can break through a thin wall.
3
Choose the tool for the featureBack-chamfer tool for bore exits, 90° chamfer mill for rims, ball or bull-nose for slots. Do not use one tool for all three unless the geometry is simple.
4
Run the finishing pass at speedOffset the toolpath 0.10–0.15 mm and lift 0.05 mm above the floor. Run 20–30% faster than roughing feed. On aluminium, 12,000 rpm and 1,500 mm/min is a workable start.
5
Tilt on 5-axis where neededUse a 30–45° tool tilt to reach bore exits and undercuts. This often removes a manual operation entirely. Check clearance before the first run.
6
Inspect one edge at the machinePause after the pass and check one edge with a 10× loupe or a 0.05 mm radius gauge. Look for a folded lip, not just a sharp feel. Adjust depth before running the rest of the batch.
7
Clean and protect before unclampingBlow chips out of the bores and wipe the edges. A chip left in a bore will press into the wall during handling and create a new burr.
8
Record the settingLog tool, depth, speed, and feed for the next hull part of the same family. Repeatability comes from the record, not from memory.

Method selection

Which deburring method fits which hull feature

Use this when the drawing calls out an edge break but does not name a process.

Feature	Recommended method	Typical edge break	Watch out for
Cross-drilled bore exit	Back-chamfer or spring-loaded blade	0.10–0.20 mm	Tool clearance inside the bore
Blind hole floor	Bottom-cut chamfer tool	0.05–0.10 mm	Floor radius left by the tool
Pocket rim	90° chamfer mill, tangential	0.15 mm	Flat spot from radial entry
Slot walls	Ball or bull-nose, two passes	0.05–0.10 mm	Smearing on stainless
Long hull section edge	In-cycle finishing pass	0.10–0.15 mm	Wall distortion on thin sections
Many small intersecting holes	Abrasive flow machining	Uniform radius	Cycle time per part
Thin-wall stainless part	Electrochemical deburring	0.05–0.10 mm	Fixturing and electrolyte cost
Complex steel internal passage	Thermal deburring	Burr burned away	Not suitable for aluminium

The method that works is the one you plan for

Prevent the burr with a sharper insert and a controlled exit, then remove what is left in the same setup. Hand work is a fallback, not a plan.

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FAQs

Common questions

What edge break size should a hull part drawing specify?

Most hull parts work with a 0.10–0.20 mm edge break on aluminium and 0.05–0.10 mm on stainless, titanium, or thin-wall sections. Anything larger starts to remove functional material near a seal face or a bearing seat.

If the drawing does not specify, agree on a number before cutting. A 0.05 mm difference is enough to fail a fit check on a bore that takes a pressed pin.

Can deburring be done after anodizing?

No. Anodizing builds a hard oxide layer over the edge, and any mechanical deburring afterward cuts through that layer and leaves a visible bright line.

Break the edge before finishing. If a burr is found after anodizing, the part usually has to be stripped and re-anodized, which adds cost and risk of dimensional change.

How do we check a burr that calipers cannot reach?

Use a 10× loupe or a borescope for internal bore exits. A 0.05 mm radius gauge gives a quick pass or fail on the edge itself. A white-light scan works when you need a record for the inspection report.

Calipers measure size, not edge condition. They will read a folded burr as part of the wall and pass a part that should be rejected.

Does coolant choice affect burr size on hull parts?

Yes. Flood coolant at 4–6 bar keeps the exit zone cool and flushes chips. Dry cutting aluminium leaves a gummy edge that tears during the next pass and creates a larger burr.

On stainless, a high-pressure through-tool coolant helps most at deep bore exits, where chips would otherwise be re-cut into the wall.

When is manual deburring the wrong choice?

When the part has more than about 20 edges, when the edge is inside a bore you cannot see, or when the drawing calls out a uniform radius. Hand work varies from operator to operator and is hard to inspect.

Move those parts to an in-cycle pass, abrasive flow, or electrochemical deburring. The setup cost pays back on the first batch.

What tolerance can we hold on a deburred hull part?

At GreatLight, hull parts are machined to ±0.005 mm and finished to Ra 0.8–1.6 μm where the drawing requires it. Deburring is a finishing step and does not change the functional dimensions unless the edge break is oversized.

Keep the edge break inside the drawing allowance and inspect 100% before shipment. Reports are available on request.