# Hard spot in cast iron



## AndySomogyi (May 17, 2021)

Seem to have encountered some sort of a hard spot whilst scraping the dovetails, it’s about 5/16 diameter or so.

A sharpened carbide scraper just glides over it, and requires huge amount of pressure to get it to catch.

You guys ever seen this before?

Not really sure what to do, maybe hit it with a die grinder?

This dovetail is almost there, maybe needs 4-5 more passes and it’s done, but this hard spot is really messing with me.


----------



## benmychree (May 17, 2021)

One might wonder how it was machined originally, but yes, some careful grinding would do the job.


----------



## extropic (May 17, 2021)

I've heard of a spark plug ceramic being found in cast iron. Never seen it though.
I think the story was related to WW II production (time was of the essence).

Is that old American iron or ???


----------



## AndySomogyi (May 17, 2021)

extropic said:


> I've heard of a spark plug ceramic being found in cast iron. Never seen it though.
> I think the story was related to WW II production (time was of the essence).
> 
> Is that old American iron or ???


It’s a Grizzly 8x30 knee mill.


----------



## Ulma Doctor (May 17, 2021)

i had a couple hard spots on my VHM728 saddle
the cast iron was less than stellar in my machine, many voids can bee seen
on one spot there was a void about 4x6x2 mm that i filled with JB Weld, and scraped it down


----------



## Braeden P (May 18, 2021)

on my 1890s Frankenstein lathe I got the bed re-machined on a planer giant hard spot covered 50% of the bed the tool glided over it and would not cut so we had to do three more passes then three more passes not changing the depth if it could be machined with high carbon steel then hss should work I will ad a photo


----------



## NC Rick (May 18, 2021)

I haven’t seen it first hand but have heard of bearing balls, nuts and things found in castings from Asia. I do also think the casting process can cause hard spots if the final product.


----------



## Braeden P (May 18, 2021)

Ive heard of drywall screws in straight edges dont know how.


----------



## addertooth (May 18, 2021)

Yes, carbon content can be quite variable in cast iron, and it can create localized hard spots.  We are spoiled by working with crucible steels today for a lot of our projects, which have better control and distribution of carbon and other elements.  This tends to make us surprised when we learn the uneven distribution which can be found with Cast Iron.  I run across this in antique Tamahagane steel Japanese swords quite frequently.


----------



## Braeden P (May 18, 2021)

this shows only half of the bed the other side was worse (the dark spot is the hard spot)


----------



## AndySomogyi (May 18, 2021)

addertooth said:


> Yes, carbon content can be quite variable in cast iron, and it can create localized hard spots.  We are spoiled by working with crucible steels today for a lot of our projects, which have better control and distribution of carbon and other elements.  This tends to make us surprised when we learn the uneven distribution which can be found with Cast Iron.  I run across this in antique Tamahagane steel Japanese swords quite frequently.


Yes, I think carbon and alloy content could be super variable.

I’ve only found one small void on this mill, and it’s on the side, not a bearing surface. Overall, the quality of this casting seems surprisingly decent, definitely WAY less porosity and irregularities than my 1950s Clausing lathe.


----------



## rwm (May 18, 2021)

This is a well known casting issue. It is called "chill." Areas of cast iron that cool too rapidly can become as hard as tool steel and appear white. There is a lot of research into this if you google it.
White cast iron​White cast iron is formed when, on solidification, carbon in solution is not able to form graphite. White cast irons are hard and brittle; they cannot easily be machined. White cast iron is unique in that it is the only member of the cast iron family in which carbon is present only as carbide. Due to the absence of graphite, it has a light appearance. White cast iron has high compressive strength and retains good hardness and strength at a higher temperature. The presence of different carbides, depending on the alloy content, makes white cast irons extremely hard and abrasion resistant but very brittle. An improved form of white cast iron is the chilled cast iron, discussed further in this chapter.

Robert


----------



## Larry$ (May 18, 2021)

My first new car was a Corvette with a 327-240hp engine. It consumed oil at the rate of 1 qt. for every fill of gas from the day it was new. It fouled the plugs in less than a week. Many trips to two different dealers got all sorts of superficial things done, to no avail. Finally after being told I couldn't see inside the engine while they had the heads off, I went around back. Talked to the mechanic and he showed me what the problem was. Shinny hard somethings imbedded in the cast iron cylinders. Each one formed a bump that caused the rings to gap and leak oil. I finally got a face to face meeting with a factory rep. He told me that GM would never replace a block, no matter what. POS!


----------



## AndySomogyi (May 19, 2021)

Larry$ said:


> My first new car was a Corvette with a 327-240hp engine. It consumed oil at the rate of 1 qt. for every fill of gas from the day it was new. It fouled the plugs in less than a week. Many trips to two different dealers got all sorts of superficial things done, to no avail. Finally after being told I couldn't see inside the engine while they had the heads off, I went around back. Talked to the mechanic and he showed me what the problem was. Shinny hard somethings imbedded in the cast iron cylinders. Each one formed a bump that caused the rings to gap and leak oil. I finally got a face to face meeting with a factory rep. He told me that GM would never replace a block, no matter what. POS!


Wow, seriously GM wouldn’t replace the block ?!?!? That’s crazy.

We had a similar issue with our Honda, at 75,000 mi, started burning oil, turns out some had a bad batch of piston rings. At 75,000 mi, out of warranty, Honda replaced the engine no problem.


----------



## Larry$ (May 19, 2021)

Andy, My family has been driving Hondas for quite some time. Way better than the GM cars. Wife recently got a Subaru, nice car, will see how it holds up.


----------



## AndySomogyi (May 19, 2021)

Larry$ said:


> Andy, My family has been driving Hondas for quite some time. Way better than the GM cars. Wife recently got a Subaru, nice car, will see how it holds up.


GM does make some good engines like the LS. I’m actually swapping a built Subaru N/A 2.5 into my 76 Porsche 912 (originally came with a VW bus engine.) 


Larry$ said:


> Andy, My family has been driving Hondas for quite some time. Way better than the GM cars. Wife recently got a Subaru, nice car, will see how it holds up.


GM does make some good engines like the LS.

I’m actually swapping a built N/A Subaru 2.5 into my 76 Porsche 912 (originally came with a VW bus engine  )

That’s why I need to finish rebuilding my stupid mill: so I can get back to making car parts.


----------



## ericc (May 19, 2021)

Is there any way to soften the hard spot using friction?


----------



## AndySomogyi (May 19, 2021)

ericc said:


> Is there any way to soften the hard spot using friction?



I’m pretty sure it’s a slag inclusion.

As I was scraping, every time I’d touch this spot, I hit it with a diamond bit in the Dremel, so it’s all good now. 

As it’s a slag inclusion, impossible to soften it, only way to deal with it is a diamond bit, or chipping it out. Was smaller than I thought, only about 1/8 so no big deal 


Sent from my iPhone using Tapatalk Pro


----------



## Richard King 2 (May 19, 2021)

One of my students last week in the class had a Keith Rucker SE and it had a hard spot.  I pulled out my small Dremel hand grinder and he ground it down below the surface.   I suspect it was due to heat treating as it was on a narrow edge.  I have seen first hand where a foundry mixes steel Allen Caps screws in his recipe or a filler.   My OLD foundry did that and a customer dam near broke his clapper box on his planner when he hit it.
I called the owner of the foundry and he acted like it was normal and refused to pay or male a anew one..  I went and got my patterns and now have another foundry.   I have also seen lousy castings in those cheap machines .  Bad design and bad everything.   You get what you pay for.


----------



## rwm (May 19, 2021)

AndySomogyi said:


> I’m pretty sure it’s a slag inclusion.
> 
> As I was scraping, every time I’d touch this spot, I hit it with a diamond bit in the Dremel, so it’s all good now.
> 
> ...


It could be a slag inclusion also. But a chilled area in the iron is way more technically interesting...
Robert


----------



## 9t8z28 (Jul 5, 2021)

Larry$ said:


> My first new car was a Corvette with a 327-240hp engine. It consumed oil at the rate of 1 qt. for every fill of gas from the day it was new. It fouled the plugs in less than a week. Many trips to two different dealers got all sorts of superficial things done, to no avail. Finally after being told I couldn't see inside the engine while they had the heads off, I went around back. Talked to the mechanic and he showed me what the problem was. Shinny hard somethings imbedded in the cast iron cylinders. Each one formed a bump that caused the rings to gap and leak oil. I finally got a face to face meeting with a factory rep. He told me that GM would never replace a block, no matter what. POS!


This story is interesting but we need to take into account that this issue happened 50+ years ago when automotive manufacturer's warranties were not handled and recorded by our government and others like they are today.  GM had produced over 100 MILLION of their legendary and reliable small block V8's and it has been used in millions of passenger cars and trucks from 1955 to 2004.  The production range speaks for itself.  Those very same engines are still sought-after today for hot rods and race cars.   Your issue was a rare one and certainly wasn't common.  GM has replaced their fair share of engines under warranty as has every other manufacturer.  You, unfortunately, were dealing with 1 or 2 shady lazy dealerships who obviously didn't know what they were doing to start and secondly you bought a sports car that GM new was going to be thrashed on and raced before the engine was broken in so already you had a challenge ahead of you.  All that said, your one issue doesn't make all Chevrolet's engines or vehicles a POS.  We can get into Honda's issues if you like.  I got one sitting in my driveway (not mine) that has had many issues (some still linger) since it was new.  The dealership and Honda USA have been a nightmare to deal with.  Does that make all Honda's a POS?
Lastly, not sure how much knowledge you have with engines but it sounds like the engine could have been repaired without replacement but without more info its hard to say but I am certainly not saying it was right for whoever you spoke to to deny you a warranty.  I think if you got with the right dealership to represent you, you could have got it replaced.  My father was working for GM as a tech when you bought yours new and he has many stories about Vette owners and what they did with their cars to give them the bad reputation that still haunts them today.


----------



## 9t8z28 (Jul 5, 2021)

9t8z28 said:


> This story is interesting but we need to take into account that this issue happened 50+ years ago when automotive manufacturer's warranties were not handled and recorded by our government and others like they are today.  GM had produced over 100 MILLION of their legendary and reliable small block V8's and it has been used in millions of passenger cars and trucks from 1955 to 2004.  The production range speaks for itself.  Those very same engines are still sought-after today for hot rods and race cars.   Your issue was a rare one and certainly wasn't common.  GM has replaced their fair share of engines under warranty as has every other manufacturer.  You, unfortunately, were dealing with 1 or 2 shady lazy dealerships who obviously didn't know what they were doing to start and secondly you bought a sports car that GM new was going to be thrashed on and raced before the engine was broken in so already you had a challenge ahead of you.  All that said, your one issue doesn't make all Chevrolet's engines or vehicles a POS.  We can get into Honda's issues if you like.  I got one sitting in my driveway (not mine) that has had many issues (some still linger) since it was new.  The dealership and Honda USA have been a nightmare to deal with.  Does that make all Honda's a POS?
> Lastly, not sure how much knowledge you have with engines but it sounds like the engine could have been repaired without replacement but without more info its hard to say but I am certainly not saying it was right for whoever you spoke to to deny you a warranty.  I think if you got with the right dealership to represent you, you could have got it replaced.  My father was working for GM as a tech when you bought yours new and he has many stories about Vette owners and what they did with their cars to give them the bad reputation that still haunts them today.


I forgot to add that the Generation 1 and 2 small blocks were such a great platform that when GM in 1997 decided to reintroduce their latest small block V8 known as the LS, they carried a lot of the features over.  I have had a few of these LS engines and had well over 150,000 miles on 2 of them with power adders that ran them to their full potential and they never once needed an overhaul or replacement parts.  They leaked and burned oil but so do the majority of cars on the road today.   My current vehicle has a LS2 Chevy V8 with 192,000 miles on it.


----------



## Larry$ (Jul 7, 2021)

9t8z28 said:


> not sure how much knowledge you have with engines


A fair amount. I worked on heavy equipment and truck engines for several years. Went through one of Caterpillar's training programs. I was never into racing or engine modification. 


9t8z28 said:


> it sounds like the engine could have been repaired without replacement


Like I said, the block had inclusions (in the casting) of something very hard, the shinny bumps. Something in the scrap that was melted for this engine. What is your fix for that? 
There are always going to be problems with some manufactured products. The dealers are your first solution. Next are the manufacturer's area representatives, the man that told me GM would never replace a block. 
The government finally introduced the "Lemon law" to make it easier for people to get things fixed. 
My Dad was a GM guy. He bought a new car every two years to avoid most of the problems. The last 20 years of his life he drove *F*ix-*O*r-*R*epair-*D*aily cars. He bought my Mom a Mercedes that she drove for 20 years. I did buy another GM, A Malibu for my wife to haul the kids around. It had just  gotten a new transmission @ 30K miles. Engine was fine for another 25K. Many other things failed and I sold it to a GM fan. The tranny failed him @ 60K. I've been driving Japanese ever since. Will Never own another *G*overnment *M*otors car. YMMV!

The Obama administration forgave $30+ billion of the GM bailout. Ford got nothing. Talk about distorting the market! IMHO GM should have been allowed to go into bankruptcy and the pieces sold to the highest bidders.


----------



## Richard King 2 (Jul 7, 2021)

Obama bailed out the UAW more then the GM investors.   I'm a fan of the UAW too.  But it was very unfair for the investors, many like me who had less then 10 shares.


----------



## Larry$ (Jul 7, 2021)

Richard King 2 said:


> But it was very unfair for the investors,


Did the stock holders get anything?


----------



## 9t8z28 (Jul 8, 2021)

Larry$ said:


> A fair amount. I worked on heavy equipment and truck engines for several years. Went through one of Caterpillar's training programs. I was never into racing or engine modification.
> 
> Like I said, the block had inclusions (in the casting) of something very hard, the shinny bumps. Something in the scrap that was melted for this engine. What is your fix for that?
> There are always going to be problems with some manufactured products. The dealers are your first solution. Next are the manufacturer's area representatives, the man that told me GM would never replace a block.
> ...


Bailouts.  I knew you were gonna go there, as if that directly correlates into quality.   I guess you forget what major crisis was going on from 2003 to 2008 which lead to all automotive manufactures going through a rough time.  I'll give you a hint.  We all depend on it for our day-to-day needs, roads, plastics, rubbers, transportation of food and necessities, and theres some people who think we need to phase it out and ban it altogether even though thats impossible.  
You shouldn't depend on Motor Trend for your automotive history lessons.  The (big-three) all received government money in 2008.  Ford, GM and Chrysler.  Even Mercedes was about to go under at one time because they overbuilt their cars.  but I digress.  I wouldn't say that your background would give you much experience in determining how to fix the cylinder but thats not what this forum is about so no pun intended.  Everybody has things they do better and know more about than the next guy, some more than others.  
How would I have fixed it?  My reply was based solely on the fact that you're bashing an auto manuf. off of one experience you had over 50 years ago with a time tested dependable platform and somehow that comprehends with their quality and customer service of today.  It doesn't in any way!  

Oh and what i think is missing from your story is if this intrusion existed on all 8 cylinders from day one of the initial startup, there had to have been a ton of smoke exiting the tailpipe (you would have seen this), the engine never would have ran right (barely idled) due to lack of vacuum (complete opposite of vacuum) and the engine had to be making a ton a racket.  I am sure the engine was barely making any power at all and most would have guessed the timing was off if they ignored all of the other signs.  If there was a defect on all 8 cylinders it would have never have passed inspection and even if it did the man who's job it was to put the 8 pistons in the 8 cylinders would have caught it, after all. he had 8 chances!.  I wasn't going to say this but I call  BS.  There's way more to this story than you lead us to believe.  

Other than that, you repeated what I said.


----------



## Larry$ (Jul 8, 2021)

9t8z28 said:


> in the 8 cylinders would have caught it, after all. he had 8 chances!.


I don't know how you got to 8 cylinders?? As for the guy sticking the pistons in the holes, why should he care. He gets paid the same either way.
I'm not knocking the small block engines. Out of millions made some were bound to be a POS. My problem is with the way it was handled by GM. A lot of poor quality cars were made in the US that gave the Japanese an easy entry into the market.


----------



## 9t8z28 (Jul 24, 2021)

Larry$ said:


> I don't know how you got to 8 cylinders?? As for the guy sticking the pistons in the holes, why should he care. He gets paid the same either way.
> I'm not knocking the small block engines. Out of millions made some were bound to be a POS. My problem is with the way it was handled by GM. A lot of poor quality cars were made in the US that gave the Japanese an easy entry into the market.


You used the plural of the word cylinders which describes all of them.  If it was one you would have said cylinder.  Its little things like this that add to my disbelief.  You still haven't said how many cylinders it was but even if you did that ship has sailed.  
What would the guy assembling the engine care?  He would care because of those engines he put together, each one would be started to drive from the factory doors to the lot and then onto the transport.  They recorded the batches each team put together during their shift.  If engines built during that time had issues that were traced back to their team, they would have been reprimanded and most likely taken off of the job.  And then there is that thing that existed more back then then it does today, its called pride.  

In the last 50 years, a lot of things have changed and one that comes to mind is junk yards have disappeared and the ones that still exist only do so for the demand of repair shops and recycling.  They no longer cater to the individual person whos desire is to repair their own vehicle and that is because many people today cant even change a flat tire or replace a blown fuse.  That along with computer controlled emissions adds to that.  The average person decades ago kept their vehicles for many years and many had more mechanical aptitude then they do today.  Its part of the reason our country has a shortage of these people today.  Your dad was obviously not one of those guys and thats ok because every businesses goal is to keep you coming back.  They don't want you to buy a car every 10 years, they want you to get a new one before the warranty is out.  This is also why models change every few years instead of every 8-10.  Everyone wants the latest gadgets and you cant simply add them to an older car in 2021.  
Mercedes use to produce cars that were not constrained by the budget department.  They were overbuilt but that also changed a long time ago.  They are built to a price point and they also don't want you driving it for more than 2 years and if you do, you damn sure bought an extended warranty.  Have you ever looked up the price of just the brake pads for a late model Mercedes?  
Another thing that makes me question your knowledge is your mentioning of your Malibu.  You said you sold it to a GM fan which would lead me to believe you are referring to an 80's Malibu.  If it wasn't an 80's car, then no person in their right mind would treasure a later Malibu.  Automatic transmissions of all makes and models are notorious for breaking down and its mostly due to abuse or neglect.  Automatic transmissions today are far better than they were just 5 years ago.  They have made leaps in technology.  Today a lot of factory autos can withstand daily abuse behind engines producing gobs of torque.


----------

