Finger follower hardness + chart to look at
Discussion
Hello folks, I was asked about finger followers today, and thought this chart was very useful
If you need to replace all the soft followers in your speed six. There is a method of measuring hardness (Brinell), the same as a pencil IE: (HB) A Vickers hardness test using a diamond to indent the surface, is a better measuring method. I spoke to Paul at Austec about this recently
The finger followers should measure 600 to 660 on the Brinell scale, but too hard they break as they become brittle.
Mild steel is 120. A typical file measures 800 and how many of those break or snap?
ABOVE FAILED SOFT FINGER FOLLOWER
Another method is Shore hardness is measured with an apparatus known as a Durometer and consequently is also known as 'Durometer hardness'.
I would appreciate comments on the appopriate hardness of a follower, has anyone measured components of this nature from other engines?
Also what does the camshaft face measure in a speed six? I would guess something close to 750
>> Edited by justinbaker on Saturday 26th November 11:46
If you need to replace all the soft followers in your speed six. There is a method of measuring hardness (Brinell), the same as a pencil IE: (HB) A Vickers hardness test using a diamond to indent the surface, is a better measuring method. I spoke to Paul at Austec about this recently
The finger followers should measure 600 to 660 on the Brinell scale, but too hard they break as they become brittle.
Mild steel is 120. A typical file measures 800 and how many of those break or snap?
ABOVE FAILED SOFT FINGER FOLLOWER
Another method is Shore hardness is measured with an apparatus known as a Durometer and consequently is also known as 'Durometer hardness'.
I would appreciate comments on the appopriate hardness of a follower, has anyone measured components of this nature from other engines?
Also what does the camshaft face measure in a speed six? I would guess something close to 750
>> Edited by justinbaker on Saturday 26th November 11:46
I remember doing the vickers test at college .. I also remember something about rockwell hardness but can't remember quite what that was/did and it's relationship to vickers ..?
that follower in your pic is well goosed .. that must have rattled like a marble in a tin can.
>> Edited by trackcar on Saturday 26th November 12:05
that follower in your pic is well goosed .. that must have rattled like a marble in a tin can.
>> Edited by trackcar on Saturday 26th November 12:05
As far as I can remember (hey I've never used this in the 20+ years since I was told it) the Rockwell test measures depth of indentation and the Vickers test measures area of indentation? Or something like that. Anyway, I think they are just different ways of measuring the same thing ie how far a material deflects when you try to deform it.
Of those hardness tests that use the indentation method, each uses a different shaped point. Some use a ball some a diamond point. Some measure the depth for a given force, and some measure the force exerted to achieve a particular depth.
It's rare that an object will achieve a specific 'level' of hardness all the way through.
In many instances, the 'hardness' of a given group of grains (or crystals) within the material, can only either be hard or soft within a set range of hardness. Overall the "average" measured hardness of a material must be treated with caution, especially if it's carbon steel.
With case hardening (baking in carbon rich powder) and nitriding (implanting nitrogen) only a small layer on the surface of the material is hardened.
With heat treatment (heating to a given temperature, cooling quickly, and then tempering off) the depth of the material that is hard is often greater. This hardness also is affected by the thermal latency of the material, and in large workpieces the core can remain soft, with a relatively thick hard layer.
With hardening and tempering the level of hardness is limited by the chemistry of the steel, and it only works with particular kinds of steel (silver or carbon steel). Because the depth of hardening is greater hardened objects can be more brittle.
With implant hardening (case hardening and nitriding), the hardness can be raised to a greater level than that of carbon steel, but only a limited depth can be made hard. In the extreme, implant hardeneing can cause a thin shell of material to divorce the main object, because the implants that make it hard, literally drive the material apart. Implant hardening can be applied to steels that would not normally be suitable for conventional heat treatment (hardening and tempering).
Overall, making hardness comparisons, between scales, is very very difficult because there are too many factors. The appropriate hardness for a job can only be found by experiment. Once the procedure is known, it must be carefully noted and followed in future. For this reason hardess testers are more a measure of consistency during production, than an absolute measure of hardness.
This idea is true right down to the detail of exactly where and how the measurement is made. Often the hardness test is considered destructive, and sample testing only will take place.
If the the followers are too soft, then unless the problem has been solved at source, a hardness test is nearly useless. Unless the problem has been solved, nobody can know how to harden these components, and where to test them with which test.
HTH
>> Edited by dilbert on Sunday 27th November 19:20
>> Edited by dilbert on Sunday 27th November 19:26
It's rare that an object will achieve a specific 'level' of hardness all the way through.
In many instances, the 'hardness' of a given group of grains (or crystals) within the material, can only either be hard or soft within a set range of hardness. Overall the "average" measured hardness of a material must be treated with caution, especially if it's carbon steel.
With case hardening (baking in carbon rich powder) and nitriding (implanting nitrogen) only a small layer on the surface of the material is hardened.
With heat treatment (heating to a given temperature, cooling quickly, and then tempering off) the depth of the material that is hard is often greater. This hardness also is affected by the thermal latency of the material, and in large workpieces the core can remain soft, with a relatively thick hard layer.
With hardening and tempering the level of hardness is limited by the chemistry of the steel, and it only works with particular kinds of steel (silver or carbon steel). Because the depth of hardening is greater hardened objects can be more brittle.
With implant hardening (case hardening and nitriding), the hardness can be raised to a greater level than that of carbon steel, but only a limited depth can be made hard. In the extreme, implant hardeneing can cause a thin shell of material to divorce the main object, because the implants that make it hard, literally drive the material apart. Implant hardening can be applied to steels that would not normally be suitable for conventional heat treatment (hardening and tempering).
Overall, making hardness comparisons, between scales, is very very difficult because there are too many factors. The appropriate hardness for a job can only be found by experiment. Once the procedure is known, it must be carefully noted and followed in future. For this reason hardess testers are more a measure of consistency during production, than an absolute measure of hardness.
This idea is true right down to the detail of exactly where and how the measurement is made. Often the hardness test is considered destructive, and sample testing only will take place.
If the the followers are too soft, then unless the problem has been solved at source, a hardness test is nearly useless. Unless the problem has been solved, nobody can know how to harden these components, and where to test them with which test.
HTH
>> Edited by dilbert on Sunday 27th November 19:20
>> Edited by dilbert on Sunday 27th November 19:26
Alan - Thanks for the sectional drawing. I shall try and import the scan. I have a Raster to Vector conversion program here. The Rockwell Chart C, is used a fair bit nowdays, and it may be industry standard now, possibly "metric" if you pardon the expression.
I the topic of drawings for the documentation, I did try and email, both TVR engineering, and Melling Consultancy. I am pretty sure I know the answer already, but "if you dont ask, you dont get".
TG is onin 45 mins too. Just set the DVD recording thing - Took 15 mins to fathom out how to set it!
P.S. Andy - Brilliant post of surface hardening.
>> Edited by justinbaker on Sunday 27th November 19:23
I the topic of drawings for the documentation, I did try and email, both TVR engineering, and Melling Consultancy. I am pretty sure I know the answer already, but "if you dont ask, you dont get".
TG is onin 45 mins too. Just set the DVD recording thing - Took 15 mins to fathom out how to set it!
P.S. Andy - Brilliant post of surface hardening.
>> Edited by justinbaker on Sunday 27th November 19:23
Vickers tends to be the one used most in automotive engineering, with gears needing to be 550- 600Hv at 0.6mm below the suface (750Hv at the surface) which is equivalent to about 525 Brinell being as similar levels of stress is imparted into the cam follower then it should be similar I'd say.
Matt
Matt
excellent article on hardening Dilbert! In my experience, hardness testing is very often carried out on production components (I'm most familiar with Rockwell C in my work) on a place that doesn't affect the function of the part. The company that we sub-contract our hardening to always measures the hardness they acheive, I occasionally have to make decisions on whether to accept parts that have not quite achieved specification. It is a very relevant point about the depth of hardening (known as "through hardening"
because a component may be ground after hardening, thus removing the outer surface of the hardened component, and it wouldn't be a good idea to damage the ground surface of a cam follower by indenting it with a hardness test - it's only a tiny mark, but it would be enough to cause premature wear. So I guess that a cam follower could actually be hardness tested on a non contacting surface, and as long as the through hardening properties of the steel are known, then the hardness of the contacting surfaces can be implied.
I remember an experiment at college years ago measuring hardness using an instrument called a Shore Schleroscope which did not damage the surface, but I've never seen this since, in 25 years in engineering.
because a component may be ground after hardening, thus removing the outer surface of the hardened component, and it wouldn't be a good idea to damage the ground surface of a cam follower by indenting it with a hardness test - it's only a tiny mark, but it would be enough to cause premature wear. So I guess that a cam follower could actually be hardness tested on a non contacting surface, and as long as the through hardening properties of the steel are known, then the hardness of the contacting surfaces can be implied. I remember an experiment at college years ago measuring hardness using an instrument called a Shore Schleroscope which did not damage the surface, but I've never seen this since, in 25 years in engineering.
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