Camshaft comp cams bend or not

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Darthemi75

Darthemi75

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i bought a comp cams 268-280 cam for my 440, and the person who is building is using a clock to measure the part in the cam where the the bearings go. He told me that in the center it has 9-10 thousandth of variation and the ones on the sides have 7 of variation.
Is the cam bend or not?
 
I think you mean dial indicator,it looks similar to a watch but has a probe off one end and a fixture to hold it
 
waggin said:
I think you mean dial indicator,it looks similar to a watch but has a probe off one end and a fixture to hold it
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I've heard them refered to as clocks by guys from europe, but they also call a flashlight a torch. lol Jayson
 
Darthemi75 said:
i bought a comp cams 268-280 cam for my 440, and the person who is building is using a clock to measure the part in the cam where the the bearings go. He told me that in the center it has 9-10 thousandth of variation and the ones on the sides have 7 of variation.
Is the cam bend or not?
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I'm sure they installed new cam bearings right, they may need to be allign honed, i had a 440 do this once, the cam wouldn't fit, so they had to trim down (allign) the cam bearings so the cam wouldn't bind. But you can call comp cams to varify what the problem could be.
 
Darthemi75 said:
i bought a comp cams 268-280 cam for my 440, and the person who is building is using a clock to measure the part in the cam where the the bearings go. He told me that in the center it has 9-10 thousandth of variation and the ones on the sides have 7 of variation.
Is the cam bend or not?
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0.0009 and 0.0007, 9 and 7 tenths respectively, is not too bad. My cousin is an engineering tech at a major manufacturing firm and have hundreds of CNC machine centers. He says that most of their customers tolerances are generally never spec'd out tighter than 0.0005 or 5 tenths. Anyone?
 
skybolt said:
0.0009 and 0.0007, 9 and 7 tenths respectively, is not too bad. My cousin is an engineering tech at a major manufacturing firm and have hundreds of CNC machine centers. He says that most of their customers tolerances are generally never spec'd out tighter than 0.0005 or 5 tenths. Anyone?
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I'm not sure, but I think he's saying .000, not .0000. By the way the original post is worded, it is hard to tell.
 
Darthemi75 said:
i bought a comp cams 268-280 cam for my 440, and the person who is building is using a clock to measure the part in the cam where the the bearings go. He told me that in the center it has 9-10 thousandth of variation and the ones on the sides have 7 of variation.
Is the cam bend or not?
Click to expand...

So your saying he's using a cam fixture tool to measure this? If so that's a badly machined cam. Now if he's measuring the block that's a whole different story and is the problem Joedust451 described.
 
a cam shaft is gound between centers. The material will stress relieve when lobes are ground so a final clean up cut on the bearing surfeaces would be required. There shouldn't be even .0001 difference beween one bearing surface and the next once completed. I would send it back and have their quality control people have a look at it.
 
RedFish said:
a cam shaft is gound between centers. The material will stress relieve when lobes are ground so a final clean up cut on the bearing surfeaces would be required. There shouldn't be even .0001 difference beween one bearing surface and the next once completed. I would send it back and have their quality control people have a look at it.
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I think you will find that 0.0001 is impossible to achieve except for EDM.
 
.0001 is common practice where I work. Making ammunition and can tooling is high tolerance stuff. They had to buy a couple 2 million dollar machines just to check the stuff.
Chrysler, and most American engines were not that tightly done years ago. The Japanese have shown that it makes a huge difference in quality and relability, if done correctly and things have changed.
Back to the real issue: If you suspect that Comps cam isn't up to spec, send it back. I've heard a lot of people complaining of loosing engines to Comp Cams parts and I won't be one of them.
 
sst3193 said:
.0001 is common practice where I work. Making ammunition and can tooling is high tolerance stuff. They had to buy a couple 2 million dollar machines just to check the stuff.
Chrysler, and most American engines were not that tightly done years ago. The Japanese have shown that it makes a huge difference in quality and relability, if done correctly and things have changed.
Back to the real issue: If you suspect that Comps cam isn't up to spec, send it back. I've heard a lot of people complaining of loosing engines to Comp Cams parts and I won't be one of them.
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CNC will hold 0.0002 at best, especially on a long part such as a camshaft. 0.0002 to 0.0005 would be extremely rare! This does not even come into play as far as a camshaft is concerned. You are talking about a bullet that is 1/2" long through a swaging die (not turned or ground). Factory tolerance for a turned or ground part is not even close to that. You must have some pretty good machines!!!
 
In my 19 years of writing machine code for cnc equiptment we never
used this equiptment for finish diameters on bearing journals on our
shafts.

We used a cylindrical grinder for this. Our drawing specs. were
+ or - .0005 on the journals. We either used ball bearings or tapered
bearings depending on the horsepower required. The cnc turning
equiptment in our plant could not hold the tolerance or finish on
the journals. A very new machine might but over time it would
probably start to drift.

I'm sure there are some "million" dollar machines out there that
probably will hold these tolerances without grinding, but we never
had any.

With our tolerance we could have .001 runout and still be in tolerance.

This was for 2 bearing journals with a worm thread cut in the middle
to mesh with a worm gear. If the cam has runout greater than the total tolerance I don't think I would use it. Send it back and ask for the
inspection report on it.

Sorry to ramble on......
 
skybolt said:
Sorry UncleTed. Not enough zeros. 0.0002 to 0.0005. Thanks for pointing that out. My mistake!
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skybolt said:
What, you just like to stop by and start some **** and don't come back? I've made some mistakes and am man enough to admit it, unlike some people.
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You're still talking about 2-5 tenths.
You're not a machinist are you?
 
skybolt said:
What, you just like to stop by and start some **** and don't come back? I've made some mistakes and am man enough to admit it, unlike some people.
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You ready to admit that .0001 tolerances can be held on other machines besides edm?
 
UncleTed said:
You ready to admit that .0001 tolerances can be held on other machines besides edm?
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I give, but just move the part to a cooler or hotter location and you will loose or gain 0.0001-0.0002. I give up.

This comes from my cousin who has been in the business for 35 years. His whole working career.

As Tony says, journals are usually ground, not turned. I knew that, just didn't mention it.
 
Darthemi - I read your post as 9 ten-thousanths or .0009" and 7 ten-thousanths or .0007" . If this is correct, you have nothing to worry about. There isn't much in cma bearing clearances. They get a ton of oil, they simply rotate in the bores, and the surface area vs the forces going through it is very high. You're fine. If you meant 9 to 10 thousanths, or .009-.010" then you have may have an issue, but each cam bearing has a unique dimension. So there will be some variation anyway. I dont have a new Comp cam to measure here or I would...
 
After reading all of the replies, I went back aand read the original "Question", and being a machinist myself (aerospace for over 25 years), I don't think he is talking about a dia. reading comparison from journal to journal, but more so run-out between journals.

Having said this, it still doesn't make it a good cam.

Giles
 
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