Hole-drilling EDM
- Buried starts in quenched mold steel
- Small diameter deep holes on the wire axis
- Minimal lateral force on thin insert walls
Glossary
Wire EDM Start Hole for Injection Molds: Drilling Scope & Quotes
Buried wire paths need a start hole before the through cut. Confirm drilling scope on the tooling quote.
Definition
What Is a Wire EDM Start Hole?
A wire EDM start hole is a small opening drilled in solid mold steel so the wire can thread through before the through cut begins.
When the wire path starts inside the block, there is no open edge to feed the wire. A start hole on the programmed axis solves that.
Hole-drilling EDM is the common way to create start holes in hardened plates. Conventional drill may suffice in soft steel with open access.
Start hole diameter, depth, and location affect wire threading, corner quality, and whether the mark can hide on shutoff steel.
Seehole-drilling EDMfor how the hole is drilled andwire EDMfor the through profile after threading.
Toolmaking
Start hole before the wire threads
Buried wire paths need a drilled axis first.
- Hole-drilling EDM is the usual process when the path starts inside solid steel.
- Start hole diameter and depth must clear wire diameter and threading clearance.
- Quotes should say whether start drilling is included with wire EDM.
Scope
Procurement questions on mold quotes
Start holes are a common split between wire EDM scope and hole-drilling scope.
Ask whether wire EDM quotes include drilling the start hole or list it separately
State how many buried wire paths need starts and whether they are on inserts or plates
Confirm who owns start hole diameter and depth when wire vendor differs from mold shop
Mark non cosmetic shutoffs where a start mark must not break into the cavity land
Methods
How the start hole gets drilled
Pick the process that matches steel hardness and access.
Conventional drill or milling
- Soft steel before heat treat with open access
- Larger holes where standard drills are stocked
- Through pockets that already expose a wire entry face
RFQ
Drawing notes for start holes
Link wire and hole-drilling pages when both appear on one tool.
Show wire path axis and whether the path is buried inside solid steel
Call out start hole diameter and depth tolerance when fit is tight
Note insert stack: start may be drilled before wire cut on detached inserts
After the start hole, wire EDM finishes the through slot, pocket, or profile
Go deeper
Related EDM links
Start holes connect hole drilling to wire cutting on the same mold.
EDM overview
Family context and CNC notes.
EDM overviewHole-drilling EDM
Tubular electrode drilling.
Hole-drilling EDMWire EDM
Through cut after threading.
Wire EDMEDM spark gap and overcut
Corner radius after wire cut.
EDM spark gap and overcutMold base
Plates and inserts that receive wire paths.
Mold baseVisual reference
Photos from molding and tooling programs
Images are selected from the NetProto Forge media library for this topic.
Wire EDM start hole drilled in hardened mold insert
Wire EDM start hole drilled in hardened mold insert
Small hole EDM tubular electrode at wire start location
Small hole EDM tubular electrode at wire start location
Wire EDM machine threading wire through start hole in mold p
Wire EDM machine threading wire through start hole in mold plate
FAQ
Frequently Asked Questions About Wire EDM Start Holes
Do I need a start hole for wire EDM?
Yes when the wire must begin inside solid steel. Open edge paths may not need a separate start hole.
Who drills the wire EDM start hole?
Depends on the quote. Some mold shops drill in house; others expect the wire vendor to include starts. State it on the RFQ.
What diameter should a wire EDM start hole be?
Large enough for the wire diameter and threading clearance. Confirm with the wire EDM shop when paths are tight.
Is hole-drilling EDM always required for start holes?
Not always. Soft steel and open access may use conventional drill. Hardened buried starts usually use hole-drilling EDM.
Will the start hole show on my plastic part?
The hole is in steel. When planned correctly, start marks stay on shutoff or non cosmetic steel, not on the molded surface.
Does wire EDM start hole cost extra?
Often yes when listed separately from wire cutting time. Bundled quotes may roll starts into wire EDM line items.
Next step
Quote wire paths with start holes
Upload CAD showing buried wire paths, start hole axes, and cosmetic faces so hole drilling and wire EDM scope quote clearly.