From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Machining difficulties of using 25% nickel steel for components like levers and bobbins.
| Identifier | ExFiles\Box 75\5\ scan0001 | |
| Date | 25th September 1923 | |
| x4614 Wd.{Mr Wood/Mr Whitehead} c. Hs{Lord Ernest Hives - Chair}, c. Wor.{Arthur Wormald - General Works Manager} BY8-P25.9.23. A proposal has been put forward to try out the Change Speed and Brake Levers and Brake Steady Bobbins produced in rustless steel of the 25% nickel variety. My previous acquaintance with this type of steel has left me with the impression that it is an austinic steel which is extremely difficult to machine. On a separate sheet we give you a list of the piece numbers which are to be dealt with as above. It should be noted that in connection with the Brake & Gear Levers all the parts of the Trigger Mechanism should also be made in the same type steel, including the bolts for bolting the Gate to the Quadrant Bracket - the Quadrant Bracket itself would not be made in 25% nickel steel. In submitting this matter to Messrs. Firths we would like to have any information they have in regard to the question of machining 25% nickel steel, as on a further previous occasion when I recommended this steel for a certain purpose many years ago, the Experimental Department informed me that they could not machine it. This is quite logical if the steel is austinic, as deformation of an austinic steel would result in the turning it into a martensitic state which would turn the edge of the tool; possibly Messrs. Firths could give us some treatment which would enable us to machine the parts, whilst in addition we would require from them information in regard to the tensile strength of the pieces so treated, as obviously we would not expect to heat-treat the part finally after machining had been done. I am putting the above facts fully before you, because it appears to me that the proposal to use 25% nickel because of its quenching quality is wrong for the following reasons;- 1. It is the wrong type of steel from a machining point of view. 2. The cost will be increased. 3. It is only possible to machine it by a special heat-treatment which leaves it in a soft condition. contd. | ||