Precision Shaft Quality (PSQ) Bars

Precision shaft quality stainless steel bar, 8 mm to 81 mm, straight to 0.015 inch TIR per 10 feet

8 mm - 81 mm Up to 6.4 metres h7, h8, h9, j6, f7, f8

OVERVIEW

Product Description

Precision shaft quality (PSQ) bar is a supply condition, not a grade: a ground and polished round bar held to a shaft fit and a straightness limit so that it runs in bearings and seals without further machining. Laxcon Steels supplies PSQ bar from 8 mm to 81 mm in lengths up to 6.4 metres, to h7, h8, h9, j6, f7 or f8, with straightness of 0.015 inch total indicator reading per 10 feet. Every bar is checked for ultrasonic flaws, and eddy current testing is carried out where the order calls for it.

The bar is used for pump shafts, cylinder shafts, boat shafts, piston shafts, valve shafts and bearing bars. The standard supply is rated at 75 ksi tensile strength, and 304 stainless steel shafting at 100 ksi tensile strength is available. Heat treatment is supplied as soft annealing, solution annealing, and quench and temper. Bars are packed with distance rings in plywood boxes so that the straightness survives transit. Bar without the fit and straightness requirement is bright bar, which the same lines finish from 5 mm to 115 mm.

Weight per metre by diameter is in the round bar weight chart. How shaft material is classified and selected is covered in the stainless steel shafts manual.

Stainless steel precision shaft quality bars produced by Laxcon Steels

SPECIFICATION

Supply Conditions

Size range: 8 mm - 81 mm (5/16" - 3-3/16")
Length: Up to 6.4 metres
Tolerances: h7, h8, h9, j6, f7, f8
Straightness: 0.015” TIR per 10 ft.
Heat treatments: Soft Annealing, Solution Annealing, Quench & Tempered

Eddy current tested as per customer’s requirement
Free from Radioactive elements, Mercury & Lead contamination
Grade confirmation through PMI testing with Handheld Spectrometers
Weight per metre for every listed size: metal weight calculator

Governing standards

EN 10088-3: Stainless steels: technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products for general purposes. Composition, heat treatment condition and mechanical properties per grade.
EN 10278: Dimensions and tolerances of bright steel products: the h and k tolerance classes for drawn, turned, peeled and ground bars.
ASTM A276/A276M: Stainless steel bars and shapes: composition, condition, mechanical properties and finish designations for hot-finished and cold-finished bar.
ASTM A484/A484M: General requirements for stainless steel bars, billets and forgings: permissible variations in dimensions, straightness, weight and length, and the test and marking requirements every bar order inherits.
ISO 286-1 and 286-2: The ISO code system for tolerances on linear sizes: the IT grades and the fundamental deviations behind h7, h9, h11, k12, k13, j6, f7 and f8.
EN 10204: Metallic products, types of inspection documents: the 2.2 test report and the 3.1 and 3.2 inspection certificates a purchase order can call for.

Tolerance by size, ISO 286

Nominal diameter (mm)	h7	h8	h9
over 6 to 10	0 / -0.015	0 / -0.022	0 / -0.036
over 10 to 18	0 / -0.018	0 / -0.027	0 / -0.043
over 18 to 30	0 / -0.021	0 / -0.033	0 / -0.052
over 30 to 50	0 / -0.025	0 / -0.039	0 / -0.062
over 50 to 80	0 / -0.030	0 / -0.046	0 / -0.074
over 80 to 120	0 / -0.035	0 / -0.054	0 / -0.087

Deviations in millimetres from the nominal size, ISO 286-1 and ISO 286-2. An h class permits no plus material and the full grade below nominal; the k12 and k13 classes of EN 10278, used for peeled and turned bars, permit the full grade above nominal and none below.

The j6, f7 and f8 fits

A pump shaft runs inside a bearing, a sleeve or a seal, and the drawing therefore calls for a fit rather than a plain tolerance. Under ISO 286 the j6 class straddles nominal size by a few micrometres either way, and the f7 and f8 classes sit wholly below nominal with a clearance that grows with diameter. Laxcon grinds precision shaft quality bar to those classes to order; the h7 to h9 columns above are the plain classes supplied when the customer finishes the journals.

Straightness is held to 0.015 inch total indicator reading per 10 feet (0.38 mm over 3.05 m), which is the figure the pump industry specifies for shafting, and the bar is supplied in the annealed condition at a minimum yield of 75 ksi (517 MPa) for the 300 series shaft grades, with quench and tempered martensitic and precipitation hardening grades available where a higher strength is required.

Weight per metre

Diameter (mm)	kg per metre	Metres per tonne
8	0.40	2,518.1
10	0.62	1,611.6
12	0.89	1,119.2
16	1.59	629.5
20	2.48	402.9
25	3.88	257.9
30	5.58	179.1
35	7.60	131.6
40	9.93	100.7
45	12.57	79.6
50	15.51	64.5
60	22.34	44.8
70	30.40	32.9
81	40.71	24.6

Density 7.90 g/cm³ (d² x 0.006205). A 304 bar at 7.93 g/cm³ runs 0.4 percent heavier, a 316 bar at 7.98 g/cm³ 1 percent heavier. Sizes are the published range at the nominal diameters shown.

Precision shaft quality bar against bright bar

A bright bar is finished to a diameter class and a surface roughness. A precision shaft quality bar is finished to a fit, a straightness and a stated minimum yield, because it will rotate in service and the runout that a general-purpose bright bar tolerates would show as vibration in a pump or a marine drive. The two share the finishing routes and the size overlap from 8 to 81 mm; the difference is what is measured before the bar leaves the works.

The stainless steel shaft manual sets out which grade suits which service and the PSQ bar article explains the pump shaft quality designation itself.

Frequently Asked Questions

What PSQ bar sizes does Laxcon publish?

Laxcon publishes precision shaft quality bars from 8 mm to 81 mm diameter, in lengths up to 6.4 metres.

Which PSQ tolerances and straightness are available?

Precision shaft quality bars can be supplied to h7, h8, h9, j6, f7 or f8 tolerances. Published straightness is 0.015 inch TIR per 10 feet.

How are pump shaft quality bars inspected?

The published supply information for pump shaft quality bars includes eddy-current testing, heat-treatment options and grade confirmation through handheld PMI.

How can precision shaft quality bars be packed and traced?

Laxcon packs precision shaft quality bars in standard bundles of 500 to 1,000 kg with HDPE or LDPE wrapping and two lifting slings. ISPM 15 wooden boxes and fibre-tube packing are available, and every bundle is marked with heat number, grade, size, and net and gross weight.

What should an RFQ for precision shaft quality bars include?

An enquiry for precision shaft quality bars is quotable when it states the grade, governing standard, metric size or profile, tolerance, finish or heat-treatment condition, length, quantity, test or inspection requirement, and delivery destination.

CATALOGUE