Before you commit to a tonne of chrome-plated bar, verify on a small sample the items that decide whether the whole order fits your application: grade and heat-treatment condition, final diameter and tolerance, chrome thickness per side, chrome hardness, straightness, surface finish, cut length and end condition, and packing. A sample order confirms the production route at your size, not only the appearance of a bar.
What does a chrome bar sample order actually prove?
A sample order proves that the supplier can hold your specification on the same route, at the same diameter and in the same condition that the production tonne will be made in. It proves nothing about a different size, a different grade or a different heat-treatment condition.
A sample that arrives ground and hard chrome plated, but comes from a soft 45 steel bar, tells you nothing about an induction-hardened shaft, where the case is at least HRC55 and about 2 mm deep before plating. Match the sample to the product you intend to buy: a soft chrome shaft, an induction-hardened chrome shaft, a linear shaft, a ground bar, or a quenched and tempered bar in 45 steel, 40Cr or 42CrMo.
At Yixin Precision Machinery (Changzhou), sample orders of 20–50 kg are charged; the sample fee is refunded on a formal order and freight is paid by the buyer. The minimum order is 1 t. Bars are supplied in full lengths of 4 m, 6 m, 7.5 m or 8.1 m and are cut to length by CNC from 200 mm, so ask for the cut length and end condition you will actually run. Ends are left as sawn.
Which items should the sample confirm before you commit to a tonne?
The sample should confirm every item that appears on your drawing and every item that will be checked at goods-in: grade and condition, final diameter and tolerance, chrome thickness, chrome hardness, straightness, surface roughness, cut length, end condition and packing.
The figures below are standard capabilities for Yixin products; final values for each size are fixed on the confirmed drawing, specification and order.
| Item to verify | What to state on the drawing or enquiry | Typical Yixin capability |
|---|---|---|
| Grade and condition | 45 steel soft; 45 steel induction hardened; 45 steel Q&T; 40Cr Q&T; 42CrMo Q&T | Nine catalogue products in 45 steel, 40Cr and 42CrMo; 42CrMo in Q&T condition only, made to order |
| Final diameter and tolerance | Nominal OD, tolerance class, and whether the chrome layer is included in the final size | Standard range Ø4–140 mm, up to Ø200 mm made to order; 0.02 mm tolerance band to drawing |
| Chrome | Thickness per side | Hard chrome 10–50 μm per side, chosen per order |
| Chrome hardness | HV for the plated layer | HV800+ capability |
| Straightness | mm per metre | ≈ 0.1 mm/m from Ø25; ≈ 0.2 mm/m below |
| Surface finish | Ra for the plated or ground surface | Ra ≤ 0.4 μm chrome; Ra ≤ 0.8 μm ground |
| Cut length and ends | mm, quantity, end condition | CNC cut to length from 200 mm; ends left as sawn |
| Packing | Film, ties, cases | Export: bubble film and wooden cases; no steel straps on finished bars |
How thick should the chrome be, and how hard?
State chrome thickness per side and chrome hardness in HV on the drawing, and confirm both on the sample. Yixin hard chrome runs 10–50 μm per side, chosen per order, with HV800+ chrome hardness capability.
Thickness per side matters because the coating builds the diameter in two directions. If the drawing gives the final size after plating, the plater needs the target layer to reach it. If the drawing gives the size before plating, the final size depends on the layer applied. Confirm which convention your drawing uses before the sample is cut, because the bar is made to that reading and the tolerance class is fixed against it.
Hardness of the plated layer is reported in HV, while the condition of the steel is reported in HRC for hardened and quenched and tempered products. Keep the two separate in the specification, and check that the sample report names the scale, the force and the location of the measurement rather than a single number without context.
Substrate condition has to match as well. The 45 Steel Chrome-Plated Soft Shaft and the 45 Steel Ground Round Bar are not induction hardened. The 45 Steel Induction-Hardened Chrome Shaft carries an induction-hardened case of at least HRC55 and about 2 mm deep. Quenched and tempered products have no induction-hardened case: for 45 steel Q&T the hardness is stated as surface hardness HRC25–28 or HRC28–32, chosen per order, while 40Cr Q&T is HRC28–35 and 42CrMo Q&T is HRC30–38.
What should the sample report show?
Ask for measured values for every specified item, not only a statement of compliance: diameter, chrome thickness, chrome hardness, straightness, surface roughness, and the grade and condition of the bar the sample was made from.
A report that lists nominal values tells you nothing about the capability of the route. Measured numbers, with the measuring position and the instrument identified, let you compare the sample against your drawing before you release the tonne. That comparison is the point of the exercise.
Yixin issues a mill certificate with the order, together with the commercial invoice and packing list; a certificate of origin is issued per order. Per-order third-party inspection is arranged on request. Where a third-party laboratory tests a sample, the result applies to the sample tested and to that test only.
It also helps to know which steps produced the part you are checking. Cold drawing, peeling, roll straightening, induction Q&T, induction hardening, centerless grinding, polishing and CNC cutting are carried out in house at Yixin, while hard chrome plating and machining are done by long-term partner plants to Yixin specifications. A sample report that identifies the route makes it easier to repeat the result on the production order.
How do lead time, trade terms and packing work for a sample order?
Cut-to-length from stock takes 3–5 days; non-standard diameters 7–10 days; custom heat treatment 10–20 days; 42CrMo Q&T chrome-plated bar 7–10 days. Sea-freight booking is additional.
Samples of 20–50 kg are charged, the sample fee is refunded on a formal order and freight is paid by the buyer. Trade terms are FOB Shanghai or Ningbo and T/T with a 50% deposit and the balance before shipment. The minimum order is 1 t.
Agree packing before the sample ships, because packing is part of what you are evaluating. For export, Yixin wraps the bars in bubble film and packs them in wooden cases, with no steel straps on finished bars, since straps mark the chrome surface. If the sample is packed differently from the tonne, the sample does not tell you how the delivered bars will arrive. Your brand can be printed on the packing, not on the bars.
What to put in your RFQ
- Grade and condition: 45 steel soft, 45 steel induction hardened, 45 steel Q&T, 40Cr Q&T or 42CrMo Q&T, with the hardness class where applicable.
- Final diameter with tolerance class, and whether the stated size includes the chrome layer.
- Chrome thickness per side in μm and chrome hardness in HV.
- Straightness in mm/m and surface roughness in Ra.
- Cut length in mm, quantity, and end condition, with ends left as sawn unless you specify otherwise.
- Sample size, and whether the sample must come from the same route and the same size as the production order.
- Inspection items to be measured, records required, and whether per-order third-party inspection is requested.
- Packing and documents: bubble film and wooden cases, mill certificate, packing list, certificate of origin, and brand artwork for the packing.
Summary
Sample orders for chrome bar are a specification exercise, not a formality. Before you commit to a tonne, confirm grade and condition, final diameter and tolerance, chrome thickness per side, chrome hardness, straightness, surface roughness, cut length, end condition and packing on a sample made by the same route and at the same size. Treat the sample report as the first goods-in inspection, and write the same items into the RFQ so that the drawing, the sample and the delivered bars are checked against one list.