Hobson data sheet
BUMAX 88 and 109: Fasteners for Maximum Performance Data Sheet
A four-page BUMAX brochure, distributed by Hobson, presenting BUMAX 88 and BUMAX 109 stainless fasteners against standard A4. It covers mechanical properties, composition, high and low temperature behaviour, magnetic permeability, friction and tables of tightening torque, preload and loads.
What this covers
- Mechanical properties
- Chemical composition
- High and low temperatures
- Magnetic permeability
- Friction
- Tightening torque and preload
Applies to Threaded Rod (Allthread) and Hex Bolts & Set Screws.
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- Minimum properties: A4-70 700 MPa tensile, 450 MPa yield (to M24); A4-80 800 and 600 (to M24); BUMAX 88 800 and 640 (to M36); BUMAX 109 1,000 MPa tensile, with 900 MPa yield to M12 and 800 MPa from M14 to M20.
- Made from Swedish steel SS2343 with carbon held to 0.030% max (316L Hi Mo) and 2.5 to 3.0% molybdenum.
- At high temperature, as a guideline: BUMAX 88 keeps 80% of its room temperature yield strength at 400°C and 70% at 600°C. Highest recommended working temperature in air is 600°C for BUMAX 88 and 109, against 450 to 500°C for A4-70/80.
- Impact strength at -196°C: BUMAX 88 47.4 J, BUMAX 109 29.5 J, A4-70 73.4 J.
- Maximum relative magnetic permeability: BUMAX 88 1.006, BUMAX 109 1.007, A4-80 1.012, A2-70 1.400.
- Torque table, M3 to M36 (BUMAX 109 to M20), calculated for a preload of about 65% of yield with BUMAX's anti-friction treatment, within ±15% using a calibrated torque wrench in nuts. Example, M12: BUMAX 88 82Nm for 35kN preload; BUMAX 109 115Nm for 49kN. Without anti-friction treatment the preload can fall to 20% of these values.
- BUMAX 88 and 109 are treated to cut friction, so no extra lubrication is normally needed with a nut. Assembly into a threaded hole often needs extra treatment.
Who it helps: Engineers and fitters who need strength, torque and preload figures for premium A4 stainless bolts.
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This document is published by Hobson Engineering, who supply this range to us. We show it here in full so you can read it next to the product; the summary above is ours. Read it on this page or download the PDF. For the most current version, ask us.
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