Ulma Doctor, Scraping Mentor

I have a beveled cast iron straight edge dad made out of a section of lathe bed on a machine his company scrapped out back in the 1960's. He never did stress relieve the piece of cast iron before scraping on it. Still have it, it still moves around when you try to scrape on it. One of these days, I'll get it stress relieved. But kid you not, cast iron does move on you if do not stabilized it first. Ken
Ken, hang the straightedge up by a rope or some wire. Then ring it like a bell, multiple times and in different places, loudly. It helps the cast iron to settle down. Heat treating is also a good way to get the stresses out. Doing both is best.
 
Ken, hang the straightedge up by a rope or some wire. Then ring it like a bell, multiple times and in different places, loudly. It helps the cast iron to settle down. Heat treating is also a good way to get the stresses out. Doing both is best.
Bob,
I may try that, it's only about 16" long. Still work though. I don't know how cheesy the material is , don't want it fall apart beating on it.

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Bob,
I may try that, it's only about 16" long. Still work though. I don't know how cheesy the material is , don't want it fall apart beating on it.

Sent from my SAMSUNG-SM-G920A using Tapatalk
Don't beat on it, but give it some good rings, not tiny taps. The more vibration the better.
 
Bob,
I may try that, it's only about 16" long. Still work though. I don't know how cheesy the material is , don't want it fall apart beating on it.

Sent from my SAMSUNG-SM-G920A using Tapatalk

Without the instruments to measure VSR you'll need to go by sound or tone. It would be interesting to get some feedback on the tone and how it changes over a period of three or four different tap..tap...tapping sessions.
 
The other thing that gets metal to settle down is time. Old time machine builders used to age their castings for months or years before machining them, with a heat treat in the middle, and sometimes age them again after rough machining to let them settle down. Manufacturing was different then...

One of the amazing things for me as a new machinist was removing one face of a 1/4 x 2" cold rolled steel bar and then noticing the banana shape it had afterwards. It ruined the part, but I sure learned something!
 
The other thing that gets metal to settle down is time. Old time machine builders used to age their castings for months or years before machining them, with a heat treat in the middle, and sometimes age them again after rough machining to let them settle down. Manufacturing was different then...

One of the amazing things for me as a new machinist was removing one face of a 1/4 x 2" cold rolled steel bar and then noticing the banana shape it had afterwards. It ruined the part, but I sure learned something!

Cold rolled bar is so misleading. What you see when you look at CR and HR bar would lead one to believe the CR would be the better choice to work. Dimensionally yes, but the induced stress due to cold working leads to many surprises especially the merchant quality we commonly use. The annealed and stress relieved product is much better to work with. The quality of the end product we use begins at the mill and how they treat, prep the ingot or billet before rolling or drawing.
 
Don't beat on it, but give it some good rings, not tiny taps. The more vibration the better.
I have a 42" straightedge I made from a piece of G-2 Dura Bar. I hung it from the ceiling and took a rubber mallet started hitting it not real hard but just enough to get the vibration needed to do the stress relieving. Surprisingly, it moved less than 0.002" in the entire length! I was glad. The piece of cast iron that I made that straight edge out of sat out in the South Texas heat for nearly 10 years before I machined on it. And I do believe in seasoning cast iron in the sun for a couple of years too.
 
This thread has taken an interesting twist (thanks Bob) from the original scraping topic to vibration stress relief VSR. Both are important because both are dealing with molecular realignment at different levels.

This begs the question; What part did VSR play in the crack that developed in what we now refer to as the Liberty Bell? It was rung many times before the crack developed. Was there a major defect in the casting where the crack occured or just too much overall stress.
 
ive heard that some time ago engine mfgs user to burry the castings in the ground to stress relieve the castings don't know if its true but it sounded good bill
 
Ulmadoc,

You need to take the show on the road, head East to CenTex. I believe I can round up a couple of guys to learn the art. KVT, would most likely drive up San Antonio to join the fun.

BBQ and Shiner is on me.


Nez
 
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