Machining cam blanks from Dura-Bar cast iron bar stock ?

[californiamilleghia]

Hi ,
We need some blanks for an early VW bug motor from the 50s , the later 1960s and up model blanks are available , but we have not found the early blanks and its an interesting challenge !

We have a buddy with a CNC machine shop that can machine the round bar stock into a blank ,

and we have an in house cam grinder to put the finish grind on it ,

So first "Are we crazy" ,
Can it be done ?
Will Dura-Bar work
Hardness of the cam vs the stock lifters ?

And anything else we forgot to think about ?

Thanks for your ideas ,

[CamKing]

we have been wanting to do this for years, but have never done it.
Was looking at using their ductile iron # 80-55-06, and Q&T at 52-55hrc

When we looked at the cost difference between making them out of Dura-Bar, and tool steel, we decided to just go to the tool steel.

[pdq67]

we have been wanting to do this for years, but have never done it.
Was looking at using their ductile iron # 80-55-06, and Q&T at 52-55hrc

When we looked at the cost difference between making them out of Dura-Bar, and tool steel, we decided to just go to the tool steel.

I want to ask if the operative here for cast-iron material cams is, "cementite".

Is cast-iron derived, "cementite", hard enough to be used for camshafts?

pdq67

[SchmidtMotorWorks]

That Durabar is pricey stuff.

These tool steels will probably be less expensive and machine beautifully with good tooling.
S7 more durable to shock
A2 capable of higher hardness

If I just need a small amount I go to Hudson Tool Steel.

[californiamilleghia]

Yes the Durabar is pricy , but a VW cam is only about a foot long ,
and the stock cam was cast iron , so the lifters hopefully will be Ok ,

Thats what I worry about with tool steel , that it is too hard and will eat up the stock lifters,

we need to get the material of a stock cam tested so we know the hardness compared to Dura-bar.

[SchmidtMotorWorks]

Yes the Durabar is pricy , but a VW cam is only about a foot long ,
and the stock cam was cast iron , so the lifters hopefully will be Ok ,

Thats what I worry about with tool steel , that it is too hard and will eat up the stock lifters,

we need to get the material of a stock cam tested so we know the hardness compared to Dura-bar.

I doubt that hardness in and of itself will be a problem unless it is coupled with a rough surface finish.

[CamKing]

Yes the Durabar is pricy , but a VW cam is only about a foot long ,
and the stock cam was cast iron , so the lifters hopefully will be Ok ,

Thats what I worry about with tool steel , that it is too hard and will eat up the stock lifters,

we need to get the material of a stock cam tested so we know the hardness compared to Dura-bar.

You will have to heat treat the dura-bar, so you can match the stock cam hardness exactly.

If you go with tool steel, you can have the lifters coated.

[pdq67]

What is that Diamond coating?

pdq67

[modok]

Great idea, I'd love to see if it works.
Although I'm not sure if they have the best alloy for it.
Iron or steel cams.. seems to me that chromium carbides are really they key for longevity

[Dan Timberlake]

What diameter would the blank need to be ?

https://www.mcmaster.com/89105K283/

[californiamilleghia]

I don't have a cam in front of me right now but I would think about 2 1/2 inch where the gear bolts on ,

[pdq67]

Great idea, I'd love to see if it works.
Although I'm not sure if they have the best alloy for it.
Iron or steel cams.. seems to me that chromium carbides are really they key for longevity

I have posted this before.

Back when I worked for AP Green refractories, I got to help reline either an Ajax Magathermic or an Inductotherm channel inductuion furance with Green's famous Jade-Pak 88-P, 88 percent Tabular Alumina/10 percent Chromic oxide/Phos Acid bonded plastic.. Anyway, I got to meet up with the melt crew and Boss several years later at the AFS convention in St. Louis, MO and and I asked him how the lining worked?

He said great, but that due to leaching of the chrome out of the lining, their cast parts machining costs increased because the metal was harder was all.

YES, an addition of Chrome does make better metal!!

pdq67

[californiamilleghia]

Thanks for all your thoughts ,

So far it looks like it should work ,

one plus is we can make an oversize cam for the bearing surface , which on this motor just turn in the engine block without replaceable bearings .
then we can bore the cam bearing surface oversize to fit ,

thanks again

[CamKing]

With what coating?

DLC

[volodkovich]

If through-hardened to ~55-60Rc, would the core be too brittle on a cam machined from ductile cast iron?