[Metrology] First scraping project: scrap iron straight edge

[AndySomogyi]

Hey all,

Let me introduce myself. I’m a research scientist at my day job (physics), and I’ve got a home shop with mill that I need to repair the knee gibs. So, I’m learning to scrape so I can repair it myself. I firmly believe you learn best by experimenting and figuring out things on your own, as reflected from the many classes I teach. Obviously I need a straight edge, and what better way to learn than building your own tools.

I started here with an old sewer grate. This good, well seasoned gray iron that’s very stable and easy to machine. First thing is I needed to see how stable this would be, so I created a finite element model and ran a few simulations to figure out how much it would bend. I calculated a max deflection of 25 millionths over 16” with a 20 lb-force load, I called that good. I figure, 20 lb-force is the most I’d ever push on it.

First challenge was cutting it, freeing the bars from the grate. First try was my carbide metal blade, which works awesome for steel. Didn’t work well on cast. My guess was the heat was hardening the surface of the iron, causing carbide precipitates to form. Next try was an abrasive disk for my Skill saw. That worked great.

Squaring the stock proved a bit of a challenge, in clamping it, as I don’t have an very big mill. But machined one surface flat, flipped it over and machined the other side in sections. With two sides now parallel, I could finally clamp it in the vise. Cast machined very nicely, got the faces flat and parallel at about 0.001 over 16”.

To machine the 45 angle, I used my 45 degree face mill, and moved both the Z and Y in 0.040 steps to make a nice continuous face. Left a 0.050 flat on the angle edge.

Now for the real test, how does experiment compare with mathematical model. Rigged it up on my surface plate, with a tenths indicator, and added a 20 lb-force load to the center. Sure enough, the needle moves just barely perceptibly. I’d say right about 25 millionths. So mathematical model verified.

Next steps: learning to scrape.

Sent from my iPhone using Tapatalk Pro

 

[AndySomogyi]

Here’s my first attempt at a scraper. This didn’t work so well, and I’m still trying to understand the physics of a stiff scraper beam, cutting angle and chatter.

This was an experiment, a learning experience, and we learn from failure. Because this didn’t work so well, I’m going to build a 1/8 cold-rolled beam scraper with a lot more flex. I’ll make a few videos comparing a stiff vs bendy scraper to try to understand differences and analyze why this one didn’t work so well.

Sent from my iPhone using Tapatalk Pro

 

[benmychree]

You might consider taking one of Rich King's scraping classes, and yes, a flexible scraper is desirable, but 1/8" may be too flexible; consider buying one of Sandvik's carbide insert hand scrapers. My first scrapers were 12" mill files with the teeth ground off on all sides, on the width, I ground the teeth off to the narrow width on the end, then forged the end down to about 1/16" thick, rough ground it and re hardened it, and then finish ground and stoned it; these scrapers are ground straight on the cutting edge unlike what you did with the double facet on the end, that only need be done with carbide scrapers to avoid spalling the cutting edge on the running off side while grinding.

 

[AndySomogyi]

You might consider taking one of Rich King's scraping classes, and yes, a flexible scraper is desirable, but 1/8" may be too flexible; consider buying one of Sandvik's carbide insert hand scrapers. My first scrapers were 12" mill files with the teeth ground off on all sides, on the width, I ground the teeth off to the narrow width on the end, then forged the end down to about 1/16" thick, rough ground it and re hardened it, and then finish ground and stoned it; these scrapers are ground straight on the cutting edge unlike what you did with the double facet on the end, that only need be done with carbide scrapers to avoid spalling the cutting edge on the running off side while grinding.

I just ordered a Sandvic insert off eBay and I’m making one of Claugh42’s scrapers. Using 4mm cold rolled, as it’s supposed to have the right amount of flex.

If the commercial scrapers were a bit more reasonably priced, I’d buy one, but LOL, I’m poor. Need to learn make my own tools and learn all the skills to fix my other tools because I can’t afford good tools ha ha. But it’s also a great learning experience and all these mis-steps, what works and what doesn’t, and most importantly why they do and don’t work are getting written up in the book I’m writing.

That’s great about your file scraper, my grandpa had a number like that that he ground down from old files.

Sent from my iPhone using Tapatalk Pro

 

[eeler1]

Learning from mistakes is good, I learn stuff all the time that way. But research can be beneficial too. Maybe go to you tube and search richard king scraping. Theres quite a few videos up and you pick up something here or there from each. Also Stefan Gottswinter and Keith Rucker have some good scraping videos. Lots of scraping info here on this site too. Just a thought.

 

[AndySomogyi]

Learning from mistakes is good, I learn stuff all the time that way. But research can be beneficial too. Maybe go to you tube and search richard king scraping. Theres quite a few videos up and you pick up something here or there from each. Also Stefan Gottswinter and Keith Rucker have some good scraping videos. Lots of scraping info here on this site too. Just a thought.

Thanks, I’ve got a playlist of great You Tube scraping videos that I’ve watched, I really like Stephan G’s videos.

Here’s with another hour or so of practice. I part of the problem is the scraper geometry, or possibly bad quality sharpening on it, as I seem to be getting some scratches.

One important lesson I learned today is do everything in short strokes. Scrapes and also use the de burring stone in short strokes, don’t drag the stone over your work because it’s likely to pick up a piece of grit and drag that across leaving a nasty scratch.

I’m also playing around with push angle. Seems to cut a bit smoother if instead of exactly perpendicular to the blade, you angle the blade about 10 degrees or so, this gives a smoother, more shearing cut.

Sent from my iPhone using Tapatalk Pro

 

[Richard King 2]

Hey everyone. I told Andy to come here as he as he started to write on my Facebook page "King-Way Scraping Consultants". I only want professional write ups and not rookies experimenting on there. Andy, several of these guys have taken my classes. Benmy has assisted me in 2 of the 4 or 5 he attended. He also owns a lot of nice scraping tools and has owned and operated Manufacturing plants and is Journeyman machinist. Eeler is a famous You Tuber, has taken 2 of my classes, helped organize those classes and is the coordinator of the next one we are doing in CA in 2020. They are not rookies and you would be smart to ask questions as they are years ahead of your techniques and experiments. I believe you have a genuine interested and excited as heck to show off your work. Hobby Machinist is a better place to show your experiments and LEARN.

You have to realize there are experienced people here who "know" what they are talking about. I have taught MIT Professors and PHD's in several of my classes and one wrote he had read the Connelly book, read and watched internet articles and never got it until he attended one of my classes and had me standing behind him showing him how. No offence Andy you need to practice a lot more before showing your scraping. Those photos are bad, and before posting them you need to open your mind and learn from experienced mentors. You said your a teacher? Didn't it take 4 to 6 years of study and if your a DR it took you another what 2 years of learning? Scraping is a skilled trade and rebuilding is a 4 year apprenticeship to become a Journeyman before we can teach rookies. Using a Sharpie is what we do when we are close to finish scraping and not when we are roughing. The rule of thumb is you rough scrape until you get 5 PSI - 100% of the area.

That home made scraper you made from HSS is what used 50+ years ago. It's obsolete and you need to heat threat the end and sharpen it better. He said he got the info from the Connelly book which is 50 + years old too. The basics of scraping in there is a good learning chapter, but times have changed since the fellow who wrote it (Not Connelly). Enjoy...

 

[AndySomogyi]

Hey everyone. I told Andy to come here as he as he started to write on my Facebook page "King-Way Scraping Consultants". I only want professional write ups and not rookies experimenting on there. Andy, several of these guys have taken my classes. Benmy has assisted me in 2 of the 4 or 5 he attended. He also owns a lot of nice scraping tools and has owned and operated Manufacturing plants and is Journeyman machinist. Eeler is a famous You Tuber, has taken 2 of my classes, helped organize those classes and is the coordinator of the next one we are doing in CA in 2020. They are not rookies and you would be smart to ask questions as they are years ahead of your techniques and experiments. I believe you have a genuine interested and excited as heck to show off your work. Hobby Machinist is a better place to show your experiments and LEARN.

You have to realize there are experienced people here who "know" what they are talking about. I have taught MIT Professors and PHD's in several of my classes and one wrote he had read the Connelly book, read and watched internet articles and never got it until he attended one of my classes and had me standing behind him showing him how. No offence Andy you need to practice a lot more before showing your scraping. Those photos are bad, and before posting them you need to open your mind and learn from experienced mentors. You said your a teacher? Didn't it take 4 to 6 years of study and if your a DR it took you another what 2 years of learning? Scraping is a skilled trade and rebuilding is a 4 year apprenticeship to become a Journeyman before we can teach rookies. Your can't teach these guys anything, you can just show your work and in my opinion your scraping is an embarrassment . Using a Sharpie is what we do when we are close to finish scraping and not when we are roughing. The rule of thumb is you rough scrape until you get 5 PSI - 100% of the area.

That home made scraper you made from HSS is what used 50+ years ago. It's obsolete and you need to heat threat the end and sharpen it better. He said he got the info from the Connelly book which is 50 + years old too. The basics of scraping in there is a good learning chapter, but times have changed since the fellow who wrote it (Not Connelly). Enjoy...

This is literally the first time I used a scraper this way, after about an hours worth of practice, never done this before, and my scraper geometry is wrong. Here, I was working on getting it first flat, so hinges right before going further, used to sharpie so show the high corners, so that could focus on those areas.

Basically I’m doing this because I need to fix my mill, the ways are pretty badly gouged up. So in order to fix my mill, I need to refinish the knee ways. But I’ve got a junky mill because that’s all I can afford, and I need to figure out how to fix is because I can’t afford to pay anyone else to do so. And I need my mill so I can get back to making car parts

What really excites me is designing and fabricating all the cooling system, chassis, engine management, brake components for my project car, and I need my tools to do it.

My undergrad degree (electrical engineering) took a while because I did it at nights and worked full time (VW/Porsche technician). My grad degree (physics) took 6 years, but it’s a research degree, no classes, just research where you figure out new stuff no one’s done before.

Anyways, fixing my mill is not something that I wanted to do, but it’s got to get done, no one else is gonna do it, so I need to figure out how.

Sent from my iPad using Tapatalk Pro

 

[AndySomogyi]

One thing I'm finding super interesting is the physics of scraping -- how the chip forms, how it breaks off, how the flex of the scraper effects chatter. For my day job, I develop physics simulation code that models highly deformable materials, the method I use was originally use to study fluid flow in foams. Anyways, what's cool is that when a chip forms, the work material starts off in an elastic deformation, finite element method is great for this. But when it gets beyond the elastic and into the plastic and finally fracture stage, software like what I write could probably be use to study the physics of it. So what would be an interesting experiment is to compare the results of the first sh!tty scraper I made to when I get the new one made based on Claugh42's design, and see if I can use my software to understand the physics of whats going on. Ha ha, I see it as possibly leading into a paper that can write.

 

[Richard King 2]

Here is a GREAT You Tube show from 2 of my students.

If you want to meet Lance or Adam I will be again teaching a class that will be attending in January down in Florida on the gulf coast. Lance is a PHD too and teaches at the University of Florida. He has been scraping for several years before he started to teach. Someone who tries to teach when they are a rookie is ridiculous in my opinion.