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Ulma Doctor, Scraping Mentor

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Bob Korves

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#1
Bob\'s First Scrape (2).jpg

A couple weeks ago I saw Mike Walton's (Ulma Doctor) request on HM for people interested in a scraping party and sent him an email saying hell yes, I am interested! Mike got back to me and said that there wasn't much interest in the scraping party, but perhaps I could come down to his shop and do some one on one, hands-on training. He didn't need to ask twice...

We were able to get together today and I thought others might be interested in what kinds of things we were doing there.

First, Mike showed me around his shop. I lost count of machines after about 4 mills and maybe 6 lathes, along with a lot of other cool stuff. In Mike's defense, in case his wife sees this, some of the lathes and mills were small ones. And I thought I had it bad. 8^)

Next, we got started on scraping. Mike showed me all the tools of the trade he had and described their usage. We put some spotting dye on a surface plate, and rolled it out. Then he marked up our first victim, the bottom of a old V-block that had seen better days.

After reading the spots together Mike showed me how to use the Biax power scraper to work the surface, then stoned it and cleaned it. And then we started on the next pass. This time it was MY turn to hold the weapon with MY finger on the trigger. It was, quite simply, no big deal. The Biax tool is well behaved, pretty easy to hold on to and to control scraping of the work, even for this raw beginner. It is also quite productive with experienced hands on it.

We rinsed, lathered, and repeated until the V-block was flat and had quite a few points, with only the corners needing more work.

Then we moved to hand scraping with several different tools. For a victim this time I was using the Harbor Freight plane that Mike had purchased new for about $8 and had worked the bottom of it to a very nice surface. I got to work on one of the sides of that plane and worked it through quite a few scraping cycles with Mike keeping an eye on me while working his own projects. Above is a pic of it after my last pass. There is a smudge on it from my thumb, and the extreme front has no spots because the plane has a very low area there that I was not able to get completely scraped level in the allotted time. It is in no way finished but is well on its way for Mike to complete.

Scraping is a mellow, zen like activity. Go through the cycles, read the spots, interpret them, and improve the work as much as you can while making very shallow cuts where indicated. Repeat, repeat, and keep on repeating. The progress is visible and rewarding. When the work is becoming quite flat it feels different, and slides on the surface plate like wet glass. It is not instant gratification, which can be a good thing.

Mike is a quite capable instructor, friendly, easy going, happy, and glad to be doing and helping. Helluva nice guy, too. I'm planning to go back for more real soon.
-Bob

Bob\'s First Scrape.jpg
 

Ulma Doctor

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#2
I'm glad you had a good time and that i was able to help you along.
you really did get the ideas fast and were doing things like you have done it for years.
thanks Bob it was a pleasure have you in my shop- you are welcome here anytime.

for everyone else...
the credit for this side's scraping of the plane is all Bob's.
i knocked the ridges off the long end an old 18" file i had in the shop and ground it to do the hand scraping.
even with the 5* rake sharpened file he did excellent work.
almost anyone can scrape using modest tools and a flat rock.
 

MARVIN GARDENS

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#3
I'd sure like to attend your next "party." I have never done any scraping or even seen it done.

I'd did pick up what look like an unused set of four Mound scrapers for $20 at a local flea market.

Regards.

Bob
 

Ulma Doctor

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#5
Hi expressline99,
on Feb 12, 2017 we had a meeting of some local members at my house.
i held an informal class for the group.
Bob Korves brought a piece of mild steel he had flattened on his newly acquired surface grinder and the piece was then scraped by the group.
everybody got a shot at it!
we had a great time!
 

expressline99

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#6
Hi expressline99,
on Feb 12, 2017 we had a meeting of some local members at my house.
i held an informal class for the group.
Bob Korves brought a piece of mild steel he had flattened on his newly acquired surface grinder and the piece was then scraped by the group.
everybody got a shot at it!
we had a great time!
Sounds awesome. I'm just over the hill in Reno. So with some advanced notice I'd love to show up for meeting sometime. I can be the super novice of the
group. :)
 

Kernbigo

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#8
don't scrap steel it is not stable, the heat from you hand can change how it reads, use cast iron.
 

Kernbigo

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#10
why do you think they make straight edges out of cast iron, it is stable after you leave it out in the weather for a couple years to stabilize, than machine it and scrape it in .I did this for 30 years and trust me mild steal is not stable
 

Ulma Doctor

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#11
For instructional purposes mild steel works just fine.
The piece being scraped was not for precision, merely a teaching aid.
The mild steel was used as a comparison of relative flatness achieved by a surface grinder vs. scraping
The surface grinder was flat to about .001"
 
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Kernbigo

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#12
you are wrong mild steel is not stable for scraping i tried it, one time and the heat from your hands would change it, why arent surface plates and straight edges made of mild steel, because they are not stable
 

Ulma Doctor

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#13
OK i'm wrong,


Hear Ye!!!!

Thou shalt never scrape mild steel, even if it is for instructional purposes that will never be used for a precision comparator or reference or facsimile thereof
cast iron will be the only material to ever be scraped from this moment forward!!!:oops:
 
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4gsr

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#14
You wouldn't want a straight edge made from steel flat bar. But I have scraped a many of gibs that were steel. Believe me it will move all over the place on you, not easy to keep a steel gib straight from scraping.

Ken
 

Ulma Doctor

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#15
my previous point , whether taken or not, was that most anything can be scraped to varying levels of precision
whether the material will hold the tolerance or not is inconsequential when you are explaining and showing scraping to someone who has never held a scraper before.
 

Rustrp

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#16
you are wrong mild steel is not stable for scraping i tried it, one time and the heat from your hands would change it, why arent surface plates and straight edges made of mild steel, because they are not stable
Perception changes as we educate ourselves. Things that may be dropped and bent tend to be made of cast iron or steel that can be tempered. This doesn't mean they can't be damaged, just more difficult to do. I'm just adding two bits here because I think it's unfortunate to get stuck in black and white thinking. It stops the educational process. Many items manufactured from cast iron years ago are now manufactured from steel plate.

The sheetmetal working equipment I own is predominately made of steel that requires scraping to true them up. Should I not scrape them. I have a 10' shear with a bed fabricated from heavy steel plate. I've used many shears where the beds were made from cast iron. It's easy to lose sight of of the lesson being taught if we get tunnel vision on dimensional tolerances or mechanical properties of material. I don't have to be wrong for you to be correct.

I encourage that education and experience be used in a positive manner. e.g. My youngest son came home from wood shop and said; Dad, most of the guys don't even know how to use a measuring tape. I said; Use what you know to help them learn. -Russ
 

bfd

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#19
even cast iron moves with the addition of heat maybe not as much as other materials. when I was an apprentice I had to scrape the turbine cases of boiler feed pumps they were made of steel and were scraped to allow for sealing steam without any sealant between the faces. never had a leak. the large cast iron straight edges used for restoring lathe ways have wooden handles built in so the heat from holding them do not change them. bill
 

4gsr

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#20
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
 

Bob Korves

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#21
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.
 

4gsr

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#22
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.

Sent from my SAMSUNG-SM-G920A using Tapatalk
 

Bob Korves

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#23
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.
 

Rustrp

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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
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.
 

Bob Korves

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#25
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!
 

Rustrp

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#26
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.
 

4gsr

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#27
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.
 

Rustrp

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#28
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.
 

bfd

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#29
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
 

Bamban

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#30
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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