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Hi Robin,

Rockwell-C hardness testing is done with a cone which is pressed in the matetial, it will leave a pit. An alternative, which still leaves a mark but smaller is using an equityp, which uses a much lower force (from a small spring in a “pencil”. Whatever you decide: Make sure you understand how the testing is done and what marking is left.  Better not to measure at the tip which sees the highest load.

https://www.proceq.com/compare/equotip/

 

Regards,

Waldi

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Hi Robin,

they looks as if they know what they are doing.

Hardness testing, although not complicated to perform, needs to be done with certain factors in mind.

If the whole lump (1/2" or more thick) is of the same hardness then the standard Rockwell C can be done - 150Kg force on the tip.

If it is case hardened then you need to careful not to force your way into the none hardened parent material other wise you get a lower reading

For this you can use a superficial tester using 1, 2 or 5Kg - this can be bit iffy 

Also flat surfaces give different values to curved surfaces.

For your cam I would assume they will test the rounded area opposite the cam lobe

 

Good luck

Roger

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Hi Waldi,

our posts passed in the ether somewhere.

At BA it was the metalurgist that did the hardness testing. He used the standard bench tester (150kG).

I never liked the Equitip- it gave a fair amount of variation.

I got involved in site testing a hand held electronic bit of kit - marketed by GE. Initially it had a 1kG force. It worked but not convincingly. They then produced 2 and 5kG - these were more stable, but!!

 

Roger

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Hi Roger,

I have used the equotip often, mainly for field - or shop inspections. You can quickly have hardness results, also in otherwise impossible to reach locations or orientations.

It does not work on thin materials, there needs to be sufficient “mass”, otherwise scatter it the result.

It requires preparation of the surface to remove corrosion, paint etc which otherwise will give false readings normally done with sank paper or the flexible disc on the angle grinder. The surface needs to be smooth finish. Then take a series of I think 5 or 6 measurements, ignore the extremes, and the avg is the hardness, which can be converted to different scales (like Brinell, Rockwell) with a table. I have never tested aluminium though, because in our industry this is rarely used.

Best Regards,

Waldi

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Robin, Undue cam wear might not be due to low hardness if the  oil lacks corrrect and sufficient anti-scuff additives eg ZDDP. Modern cat-friendly oils bear little resemblance to those we used in 1970s

Peter

Edited by Peter Cobbold
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Due to the reason that the cam is casted into a cooled form

where the lobes are quickly cooled down often the base circle is not hard.

 

Best way to proceed is to risk a mark on the downrunning side of the lobe

5mm after the top. It will hurt but all other things are tricky. Normally my

grinder does a hardness test a short time before the finish grind that the mark

is away when finished.

 

But that is more the case when a stock cam is for regrind and they have to decide

whether they have to give it a final nitriding process to make it reliable again because

the grind might have hurt the hardened area.

As the base circle is grind down anyway I know that there often is no hard area.

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  • 1 month later...
On 9/1/2019 at 5:44 PM, Peter Cobbold said:

Robin, Undue cam wear might not be due to low hardness if the  oil lacks corrrect and sufficient anti-scuff additives eg ZDDP. Modern cat-friendly oils bear little resemblance to those we used in 1970s

Peter

Agree about the oil.

They are general better than the stuff from the 70's.

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peter ~   running in oil used  bought from Classic  & Modern workshop ~ unused cam  other than 14 miles  actual road use:   cam damage  not down to oil type used.

I reckon that this ends the  discussion loop  .Thanks everyone  robin

 

 

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Hi Waldi

At present its not worth paying for  a £75 hardness test  [other than to satisfy my curiosity ]  when I  can use that money toward a new Cam + Followers

Like most Tr engine problems ,  the actual cause may be different to the strongly suspected cause but in  reality my time is now is set on rechecking the whole engine

and to put a new cam  in that I can trust .

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I understand Robin,

for every part I ordered, I searched this forum for experiences.

For example, I fitted the (softer) double TR5/early 6 valve springs, instead of “uprated” springs. Uprated does not mean better, but stronger, which leads to higher force between tappet and cam. The devil is in the detail.

Good luck with the rebuild, work slowly but precise.

Regards,

Waldi

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