Internal Spline Broaching
Broaching of internal spline forms in forged hub, gear, and coupling bores, producing the complete spline profile in a single linear pass of the broach tool through the pre-machined bore.
Single Linear Pass Machining
Roughing Through Finishing Completed in One Stroke
Internal Spline & Keyway Specialist
Standard Process for Bore-Based Form Generation
Excellent Repeatability at Volume
Fixed Tool Geometry Produces Consistent Part-to-Part Form
Dedicated Tooling Investment
Broach Tool Specific to Each Form and Size
One Pass, Every Tooth Cutting a Little Deeper Than the Last
Broaching is mechanically distinct from milling, hobbing, or shaping in a way that matters for both accuracy and production economics: a broach tool carries a long series of teeth along its length, each successive tooth machined slightly larger (or, for internal broaching, progressively deeper) than the one before it, so that a single linear pass of the tool through or across the workpiece completes the entire cut — roughing, semi-finishing, and finishing all happen within that one stroke, in a single fixed toolpath rather than a programmed multi-pass sequence a milling cutter would need to build up the same form. This makes broaching the standard production process specifically for internal splines, keyways, and internal gear forms cut into a bore, since a broach pulled or pushed through a pre-existing bore produces the complete internal form in one operation with excellent repeatability from part to part, once the broach tool itself is made. Our spline shaft forging page describes hobbing, broaching, and rolling as the family of processes that can generate spline geometry on a forged blank; broaching is specifically the process best suited to internal spline and keyway forms, and it's also the standard process for external keyway slotting where high-volume repeatability matters. The tradeoff broaching accepts for this single-pass efficiency is tooling cost and lead time: a broach tool is dedicated to one specific form and size, representing real upfront tooling investment that, like closed-die forging tooling, needs sufficient production volume to justify economically.
Broaching Services for Forged Components
Keyway Broaching
Broaching of internal and external keyway slots in forged shafts, hubs, and gears, a standard high-volume process for producing consistent, accurately sized keyway geometry.
Internal Gear Tooth Form Broaching
Broaching of internal gear tooth forms where the geometry and production volume favor broaching's single-pass approach over hobbing or shaping for internal gear generation.
Non-Round Bore Form Broaching
Broaching of non-round internal bore forms — square, hexagonal, or other specialized profiles — cut into forged components requiring these internal drive or locating shapes.
Process Planning and Quality for Broached Forgings
Pre-Broach Bore Preparation
Precision boring of the starting bore to the correct pre-broach diameter, since broach tool design assumes a specific starting bore size to achieve the correct final form dimension and tooth engagement.
Broach Tool Design for Component-Specific Forms
Broach tool geometry designed and manufactured for each specific spline, keyway, or form requirement, representing dedicated tooling that delivers consistent, repeatable results once production begins.
Form Accuracy and Dimensional Verification
Dimensional and form verification confirming broached spline, keyway, or gear tooth geometry meets specified tolerance, including tooth form, spacing, and depth as applicable to the specific broached feature.
Production Volume and Tooling Economics Guidance
Guidance on the production volume threshold that justifies dedicated broach tooling investment versus alternative form-generation processes for lower-volume or prototype requirements.
One Pass, Every Tooth Cutting a Little Deeper Than the Last
Broaching solves the internal form-generation problem — cutting a spline, keyway, or gear tooth profile into an existing bore — through a mechanism genuinely different from milling, hobbing, or shaping: a single broach tool carries an entire progression of cutting teeth along its length, with each tooth removing a small, precisely defined increment of material beyond what the tooth before it removed, so that pulling or pushing the tool through the bore in one continuous linear stroke completes the full form — roughing, semi-finishing, and finishing — in that single pass. There's no multi-pass programming to build up the final geometry the way a milling operation would require; the entire cutting sequence is built directly into the broach tool's fixed geometry.
This single-pass mechanism is precisely why broaching became the standard production process for internal splines and keyways specifically: an internal form, cut into an existing bore, is exactly the geometry a broach tool is built to produce efficiently, and because the tool's geometry is fixed and doesn't depend on programmed toolpath repeatability the way milling does, broached parts show excellent dimensional consistency from the first production piece through the last, once the tool itself has been correctly manufactured and the starting bore has been prepared to the diameter the tool design assumes.
The genuine tradeoff broaching accepts for this single-pass efficiency and repeatability is dedicated tooling investment: because each broach tool is built for one specific form and size, there's no flexibility to adjust the cut geometry the way a CNC milling program can be edited — a different spline profile or keyway dimension requires a different broach tool entirely. This makes broaching tooling economics genuinely comparable to forging die tooling economics in structure, if not in absolute cost: the upfront investment is justified by production volume sufficient to amortize it, and broaching becomes progressively more attractive relative to alternative form-generation processes as that volume increases.
For manufacturers requiring precision internal splines, keyways, or internal gear forms in forged hubs, shafts, or gears, Shivam Forge provides broaching services with pre-broach bore preparation and dimensional verification. Contact our engineering team at +91-9265772827 or sales@shivamforge.com with your component drawing and production volume to discuss tooling requirements and quotation.
Frequently Asked Questions
What is the difference between broaching and hobbing for spline generation?
Broaching pulls or pushes a multi-tooth tool through a bore in a single linear pass to cut the complete internal spline form at once, making it the standard choice for internal splines. Hobbing uses a rotating, gradually advancing cutter and is typically used for external spline and gear tooth generation. Both appear as options in spline shaft manufacturing; which one applies depends on whether the spline is internal or external and on production volume.
Why is broaching used for keyways and internal splines specifically?
Broaching's single-pass mechanism — a fixed sequence of progressively larger or deeper teeth completing roughing through finishing in one stroke — is particularly well suited to internal forms like keyways and splines cut into an existing bore, where the broach is simply pulled or pushed through the bore once. This produces excellent repeatability from part to part once the broach tool is made, which is exactly what high-volume keyway and spline production needs.
Does broaching require dedicated tooling for each component?
Yes. A broach tool is manufactured specifically for one form and size — the specific spline profile, keyway dimension, or gear tooth form required. This dedicated tooling represents real upfront cost and lead time, generally justified by production volume sufficient to amortize that investment, similar in principle to closed-die forging tooling economics.
What bore preparation is needed before broaching?
The starting bore must be precision-bored to the specific pre-broach diameter the broach tool design assumes, since the broach's tooth progression is designed around removing a specific, known amount of material to reach the correct final form dimension — an incorrect starting bore size will produce an incorrect final form or damage the tool.
Is broaching suitable for low-volume or prototype quantities?
Broaching's dedicated tooling cost makes it less economical at very low volumes compared to processes without dedicated form tooling. For prototype or low-volume internal spline or keyway requirements, we can advise on alternative approaches or discuss the volume threshold where broaching tooling investment becomes worthwhile for your specific component.
Why Choose Shivam Forge
Trusted forging manufacturer — Rajkot, Gujarat
Shivam Forge delivers precision hot-forged components from our integrated Shapar, Rajkot facility — covering forging, CNC machining, heat treatment, and quality inspection under one roof.
- Hot forging from quality alloy steel billets (42CrMo4, C45, EN8, SS316L)
- In-house CNC/VMC machining to drawing — ±0.05mm tolerances
- Heat treatment — normalizing, hardening, tempering, annealing
- CMM inspection and full EN 10204 3.1 material certification
- Custom OEM forging from customer drawings — PPAP/ISIR available
- Fast export from Mundra Port — CIF worldwide, FOB India
- Export expertise — Europe, Middle East, Americas, Asia-Pacific