Spex produces precision screw machine parts on Davenport multi-spindle automatic screw machines. Five spindles index through five tooling stations simultaneously, completing a finished part on every cycle — typically every 9 to 12 seconds. That parallel processing is what makes multi-spindle the fastest and most cost-effective turning process for production runs above 10,000 pieces.
We run Davenport machines on bar stock from 1/4" to 2-5/8" diameter, producing parts up to 4" in length. Materials include free-machining brass, carbon steel, stainless steel, aluminum, and copper alloys. Production volumes range from 10,000 to 500,000+ pieces per order, with blanket order and scheduled release programs available for ongoing production.This page covers how the process works, what parts are a good fit, and what to expect when quoting multi-spindle work.
A Davenport multi-spindle machine holds five bars of stock in five spindles arranged in a circle. All five spindles rotate simultaneously, and each one sits in front of a different tooling station. On every cycle, the spindle drum indexes — rotates one position — advancing each bar to the next station. When a bar reaches the fifth and final station, the part is complete and cuts off. This means five parts are in progress at all times, each at a different stage of completion. The cycle time for the entire machine is determined by the longest single operation across the five stations, not the total of all operations added together. A part that requires 45 seconds of total machining time across five stations might cycle in 10 seconds because no individual station takes longer than 10 seconds.
Each station holds dedicated tooling configured for one specific operation or set of operations:
Turning and facing remove material from the outside diameter and end face of the bar. Stepped diameters, tapers, chamfers, and shoulders are produced across one or more stations.
Threading — both internal and external — is performed by threading attachments mounted at the appropriate station. Threads are cut to specification on each cycle without operator intervention.
Cross-drilling and tapping use attachments that engage from the side of the bar, producing radial holes, cross-holes, and tapped holes perpendicular to the bar axis.
Forming and knurling shape material using dedicated form tools. Grooves, undercuts, and knurled surfaces are produced at the station where the geometry requires them.
Cutoff at the final station separates the finished part from the bar and drops it into a collection bin. The machine immediately indexes and begins the next cycle.
The entire sequence runs automatically. Once the machine is set up and the first article is approved, production continues with the operator monitoring dimensions, managing bar stock, and performing in-process checks at defined intervals.
Multi-spindle screw machines run most efficiently on alloys that produce short, broken chips at high cutting speeds. Free-machining grades were developed specifically for this type of automatic production.
C360 Brass — The standard screw machine material. Highest machinability of any common alloy. Fittings, connectors, valve components, and threaded hardware at volumes of 50,000+ are typically quoted in C360.
12L14 Steel — Free-machining carbon steel with lead for chip control. Pins, spacers, bushings, and general-purpose hardware. The lowest-cost ferrous option for high-volume turned parts.
1215 Steel — Free-machining re-sulfurized steel. Similar screw machine performance to 12L14 without the lead content, for applications where lead-free material is specified.
303 Stainless Steel — Free-machining austenitic stainless with sulfur additions. When the part needs stainless corrosion resistance at production volumes, 303 is the standard multi-spindle grade. Runs significantly faster than 304 or 316.
2011 Aluminum — Free-machining aluminum with bismuth and lead for chip breaking. Fastest-cutting aluminum grade on screw machines. Instrument components, electronic hardware, and precision fittings.
C14500 Tellurium Copper — Retains 93% of pure copper's conductivity while forming clean chips at screw machine speeds. Electrical terminals, connector bodies, and ground conductors.
Non-free-machining grades (304 stainless, 1018 and 1045 steel, 6061 aluminum, pure copper) can run on multi-spindle at reduced speeds with adjusted tooling.
Multi-spindle machining produces high-volume precision components where production efficiency drives cost reduction. The process completes complex features in single cycles, achieving tight tolerances on turned diameters, threads, cross-holes, and formed features. Parts combining multiple operations benefit from the parallel processing capabilities of 5-spindle production.
Industrial Pump & Hydraulic Systems
Pump systems require high-volume precision components machined from carbon and stainless steels. Multi-spindle machines produce shaft components, housings, and hydraulic fittings with tolerances to ±0.0005" for proper system operation.
Power & Electrical
Power distribution systems use brass and aluminum components produced at high volumes. Multi-spindle machining creates terminal connectors, bushings, and fasteners combining turned features with cross-holes and threads. Production rates of 400 parts per hour reduce component costs.
Agricultural & Heavy Equipment
Agricultural equipment relies on robust steel and stainless steel components produced in large quantities. Multi-spindle operations manufacture pins, bushings, and hydraulic fittings with formed features and precise thread specifications for reliable field performance.
Multi-spindle production runs are monitored throughout, not just at the start and end. Operators perform dimensional checks at defined intervals — the frequency depends on the tolerance band, material, and run length. On runs exceeding 50,000 pieces, SPC charting tracks critical dimensions (turned diameters, thread pitch diameter, cross-hole position) in real time across the production run.
First article inspection (FAI) and documentation follow our ISO 9001:2015 quality system. Every production order ships with material certifications (with heat and lot traceability), dimensional inspection reports on critical features, and First Article Inspection Reports (FAIRs) when specified. The documentation is the same whether the order is 10,000 pieces or 500,000.
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A Davenport Model B is a 5-spindle automatic screw machine originally developed for high-volume production of small turned parts. Five bars of stock rotate simultaneously, each in front of a different tooling station. The spindle drum indexes on every cycle, advancing each bar to the next operation. A finished part drops off at the fifth station every 9–12 seconds on typical jobs. Davenports have been in continuous production use since the early 1900s and remain one of the most cost-effective platforms for high-volume turned parts under 2-5/8" diameter.
Turning, facing, drilling, boring, reaming, tapping, threading (internal and external), cross-drilling, cross-tapping, grooving, knurling, forming, chamfering, and cutoff. Attachments expand the base capability — threading attachments, 5th position tools, and cross-work units add operations that would otherwise require secondary handling.
Standard production tolerances are ±0.005" on turned diameters and lengths. Tighter tolerances to ±0.001"–0.002" are achievable on specific features with appropriate tooling and in-process monitoring, particularly on free-machining materials. Thread tolerances follow standard class specifications (typically Class 2A/2B). Tolerances tighter than ±0.001" across all features generally push the job toward Swiss or CNC turning.
At low volumes (under 5,000 pieces), CNC turning is typically less expensive because setup is faster and simpler. As volume increases past 10,000–25,000 pieces, multi-spindle's per-part cost drops below CNC because the cycle time is 3–5x faster. At 100,000+ pieces, the cost advantage is substantial — often 40–60% lower per part than single-spindle CNC on equivalent geometries.
New jobs with dedicated tooling: 5–8 weeks including first article approval. Repeat orders with existing tooling: 2–4 weeks. Blanket order releases from scheduled production: 1–2 weeks. Setup time is the primary variable on new jobs — once the machine is running, production rates of 300–400 parts per hour mean even large orders complete quickly.
Typical throughput is 300–400 parts per hour, depending on part complexity and the longest individual station cycle time. Simple parts with short cycle times can exceed 400 per hour. Complex parts with threading, cross-drilling, and forming at multiple stations run closer to 200–300 per hour. Over an 8-hour shift, a single machine produces 1,600–3,200 parts.
We quote multi-spindle work starting at 10,000 pieces. Below that, the setup investment doesn't amortize well and CNC turning or bar-fed CNC is typically more cost-effective. The sweet spot for multi-spindle economics is 25,000 pieces and above, where the per-part cost advantage over single-spindle processes is most significant.
Part drawings or CAD models with material grade specified, required tolerances, order quantity, and estimated annual usage (EAU). Include any secondary operations needed — heat treating, plating, anodizing, etc. If the annual volume is high enough to warrant a blanket order with scheduled releases, note that on the RFQ so we can price accordingly.
