Start with the materials and standards your lab must support. Metals commonly follow ASTM E8/E8M, plastics often follow ASTM D638 or ISO 527. Confirm specimen geometry first, such as flat dog-bone, subsize, or round bar, since that determines whether a CNC milling machine, a CNC lathe, or both are needed. For consistent strain distribution, many labs target width tolerance within ±0.002 in (±0.05 mm) and surface roughness near 32 µin Ra (0.8 µm) after machining and polishing. Match capacity and accuracy to throughput goals. A practical work envelope for flat workholding is around 12 in × 24 in (305 mm × 610 mm). Typical spindle power for flat machining ranges from 2 to 5 hp (1.5 to 3.7 kW). For round specimens, look for chucking up to about 1.0 in (25 mm) diameter and 12 in (305 mm) length, with machine repeatability near ±0.0005 in (±0.013 mm). If operators run mixed alloys, prioritize recipe control, fixture quick-change, and safe chip or dust extraction. Plan the finishing and testing steps. Longitudinal polishing equipment helps achieve uniform surface finish that supports valid tensile results, and it reduces the risk of edge artifacts. Verify that shoulder dimensions or threaded ends will seat correctly in your UTM grips, for example wedge or threaded grips rated for the expected load such as 11,200 lbf (50 kN). Aligning machining, polishing, and gripping from the start prevents specimen rework and improves first-pass yield. If you would like to discuss your testing requirements, you can connect with our team on the Contact Us page.

Start with incoming material form and the governing test method. Flat CNC systems best suit sheet, plate, and strip in the 0.02–1.00 in (0.5–25.4 mm) thickness range, delivering dog-bone profiles for methods such as ASTM D638 or ISO 527. Lathe-based round systems excel on bar and rod stock around 0.25–2.00 in (6–50 mm) diameter, supporting metallic coupons for ASTM E8 when a turned gauge section is specified. Match the specimen geometry to your grips and alignment practices. Wedge or serrated grips favor flat coupons, while collet or threaded-end setups favor round. Many metallic procedures call for a 2.00 in (50 mm) gauge length; plastics often use the same nominal length. Verify required tolerances in the standard, then size the machine to hold typical coupon width and thickness within about ±0.002 in (±0.05 mm) and to blend fillet radii smoothly, for example near 0.50 in (12.7 mm) where applicable. Consider throughput, surface quality, and operator workflow. For high volume, look for quick-change fixturing, repeatable locating, and tool libraries that maintain profiles across materials from 40–300 HB (≈ 430–3,000 MPa UTS). Aim for a final surface near 63 µin Ra (1.6 µm Ra) or better on metals, remove burrs to roughly a 0.005 in (0.13 mm) edge radius, and use stable coolant delivery so heat does not distort the gauge section. If specimens require longitudinal polishing, plan capacity for repeatable passes and consistent media tracking. If you would like to discuss your testing requirements, you can reach our team on the Contact Us page for friendly guidance on next steps.

Integration starts with producing specimens that meet geometry and finish targets the UTM expects. For metals to ASTM E8, typical dog-bone flats hold gauge width within ±0.001 in (±0.025 mm), gauge length of 2.0 in (50 mm), edge radii of 0.125 to 0.250 in (3.2 to 6.4 mm), and surface finish of 16 to 32 µin Ra (0.4 to 0.8 µm). For plastics to ISO 527 or ASTM D638, consistent gauge thickness and a 2.0 in (50 mm) gauge length improve strain uniformity. Round E8 specimens benefit from concentricity within 0.002 in TIR (0.05 mm) and blends free of toolmarks. For additional guidance, you can connect with our team on the Contact Us page to review options that fit your testing workflow on the page.

Start with your material form and the target geometry required by your test method. Flat preparation is ideal for sheet, plate, or molded panels, commonly used for ASTM E8 metals or ISO 527 plastics. Typical flat dog-bone sizes include 0.25 to 1.00 in (6 to 25 mm) gauge width with 1.00 to 2.00 in (25 to 50 mm) gauge length and 0.125 in (3.2 mm) fillet radii. Round preparation suits bar, rod, wire, or cast buttons, with frequent sizes of 0.250 to 0.500 in (6 to 13 mm) diameter and 2.00 to 4.00 in (50 to 100 mm) gauge length. Target tolerances often hold ±0.001 in (±0.025 mm) in the gauge section and 0.001 in TIR (0.025 mm) concentricity for round specimens. Consider throughput and handling. For high coupon volumes across multiple alloys, a fixtured flat CNC system supports repeatable nesting and quick changeovers. For rounds, a programmable lathe-style machine with tailstock support and center drilling maintains straightness on longer pieces, for example 6 to 12 in (152 to 305 mm) overall length, while flood or mist coolant protects both metals and polymers. Confirm UTM and grip compatibility early. Flats pair well with wedge or pneumatic grips using 1 to 2 in (25 to 50 mm) jaw widths. Rounds may require collets, shoulders, or threaded ends such as 0.500-20 UNF, with shoulder perpendicularity within 0.002 in (0.05 mm). Surface finish affects results, so polish the gauge section longitudinally to Ra ≤ 32 µin (0.8 µm), or to 16 µin (0.4 µm) for notch-sensitive materials, and verify dimensions against the selected standard during first-article inspection. If you are comparing flat and round preparation solutions, you can explore the TensileMill CNC Homepage to review product families on the page.