SemiOT: Any scrapers here (general machining)

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Fulmen
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SemiOT: Any scrapers here (general machining)

Post by Fulmen »

A machinist friend claims hand scraping isn't just a dying art around here, it's extinct. Well I looked at the general description and thought "How hard can it be?" Famous last words, I know...

Well, I'm not saying I've mastered the art after a few hours, but I do find it strangely fun and compelling. Seems like good'ol Withworth fathered the technique of scraping three surfaces together, so I figured I'd start by walking it the steps of a true giant. Are there anybody here that know their stuff when it comes to scraping? I need a few good online hints and pointers to get me started, books are easier to buy when you have a rudimentary understanding of the topic...
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Re: SemiOT: Any scrapers here (general machining)

Post by JohnK454 »

No, but I keep telling myself that one day I will dive into learning the art, so I have been reading a bit here and there.

This book is referenced often - Machine Tool Reconditioning and Applications of Hand Scraping by Connelly

Practical Machinist and Home Shop Machinist are excellent sites.

Any posts by a fellow named Forrest Addy are top notch.
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Enfield577
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Re: SemiOT: Any scrapers here (general machining)

Post by Enfield577 »

I did it many years ago during my apprenticeship.

I remember it being along process and important not to take too much material of, i.e. a few scrapes and recheck
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Re: SemiOT: Any scrapers here (general machining)

Post by Fulmen »

JohnK454 wrote:Machine Tool Reconditioning and Applications of Hand Scraping by Connelly
Thanks, seems this one is available as a free e-book. Perfect for my old Sony Reader.
Practical Machinist and Home Shop Machinist are excellent sites.
I know, it's all those bastards at PM that planted the seed in my head. :wink:
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Re: SemiOT: Any scrapers here (general machining)

Post by BeerWolf »

I scrape a bit. :D
The key is "take it nice and easy".
I gouged the work a few times before i figured it out.
You REALLY don't want to do that, trust me.
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Dr.K
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Re: SemiOT: Any scrapers here (general machining)

Post by Dr.K »

I found this. It's a skill I never even knew existed.

http://www.youtube.com/watch?v=nOJrhrne80s
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Re: SemiOT: Any scrapers here (general machining)

Post by Fulmen »

Dr.K wrote:It's a skill I never even knew existed
I know, I always thought of it as an obscure and redundant technique when it is in fact the very foundation of accurate machining.
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Re: SemiOT: Any scrapers here (general machining)

Post by jreinke »

For the past year or two, the Home Shop Machinist magazine has been running a series of articles about hand scraping and how to make the tools. That would be a good source of information. Here's the link to their web site: https://secure.villagepress.com/store/i ... /group/130
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Re: SemiOT: Any scrapers here (general machining)

Post by bakerjw »

There is nothing more beautiful than a properly scraped way. Looks like fish scales.
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Re: SemiOT: Any scrapers here (general machining)

Post by Fulmen »

I'm still figuring out how the h*ck they manage that nice even pattern. Removing metal by scraping isn't hard to do, making it look like something other than what a chimp with a rock could produce is slightly harder :lol:
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Re: SemiOT: Any scrapers here (general machining)

Post by Enfield577 »

Fulmen wrote:I'm still figuring out how the h*ck they manage that nice even pattern. Removing metal by scraping isn't hard to do, making it look like something other than what a chimp with a rock could produce is slightly harder :lol:
I think that just comes down to lots of practice, just making evenly spaced cuts by hand

With a lot of work maybe you could get it to look like a well trained chimp :lol:
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Re: SemiOT: Any scrapers here (general machining)

Post by HotGuns »

I've done a bit. I went to Robert King's scraping school up in Minneappolis. It was a week long and very worth it.

He's considered one of the best scrappers in the world and travels all over the place.
He has a shop where he scrapes machines. It was his dad that invented and pattented the Kingsberry Thrust bearing used by ships and electrical turbines around the world.

A very interesting guy to talk to.
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Re: SemiOT: Any scrapers here (general machining)

Post by daviscustom »

The shop I work in has one guy that does all the scraping on the gundrills and rifling machines we build. I have never done it, but I have always been curious. They are getting ready to shuffle his work station next to mine so I hope to be getting a better understanding of the process. I tend to gravitate towards handwork anyway so I have a natural weakness for a process that can be done by hand and achieve ultra-high accuracy.
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Re: SemiOT: Any scrapers here (general machining)

Post by Fulmen »

I scored a proper 8" scraper today for less than 10 bucks, my local dealer had one that had been lying around for at least 6 years so I got it cheap. They sell car restoration equipment and hobby machine tools, but this was the first request for a scraper they've ever had.

I now get the impression that this can't be too hard all things considering, so I'm just waiting for the big surprises to slam be from behind when I least expect it :mrgreen:
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Re: SemiOT: Any scrapers here (general machining)

Post by BeerWolf »

Trust me when I say that you don't want to try anything important until you've been doing it awhile.
Practice on junk parts or just pieces of steel.
Because this is one of those things that can only be learned by doing it.

I scrapped a few things I meant to scrape. :oops:
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Re: SemiOT: Any scrapers here (general machining)

Post by Fulmen »

Don't worry, I'm still working on a few pieces of scrap. I did take a looong look at my tailstock yesterday, but managed to tear myself away before doing any damage. I did do a few cuts on my bench vice, and the difference between cast iron and the mild steel I've been practicing on was like night and day. So next will be to find something cast I can practice on...


Here's my progress so far:
Image

It's hard to get a decent surface in mild steel, the cuts end up long, narrow and shallow. I also get a lot of chatter. My few cuts on my vice was a lot better, I was instantly able to cut patches with roughly equal width/length.
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Re: SemiOT: Any scrapers here (general machining)

Post by Baffled »

AFAIK mild steel is not a candidate to be scraped. Only fine-grained cast iron, like Meehanite, can be correctly scraped.

For some beautiful examples, look to U.K amateur-made small machines, like cutter-grinders, "Tom Sr." mills, etc. Those old boys in the U.K. pre and post WW2 did some nice work. Then, the hobby mostly died there, victim of mass media entertainment and the like, just like the USA.
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Re: SemiOT: Any scrapers here (general machining)

Post by Fulmen »

Not sure if I agree with you there. Scraping is just another form of metal cutting, so why not? It may not be the optimum material to work with, but I'm scraping it as we speak and it is slowly getting flatter.
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Re: SemiOT: Any scrapers here (general machining)

Post by tony1959 »

I work the same place DavisCustom works, it's amazzing to see what they can do they will surface grind a way base and then ink it up then Gerald goes to work on it.

The one that gets me is when he does a gun drill spindle he will scrape .0002 taper in the spindle housing base to account for drill bit drop before the bit goes into the drill guide.

I will try to get some pictures of his work and get them posted up for you all to see.
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