camel back straight edge not as flat as I would like.

[bmikkalson]

I am going to try to level it with 3 points on the surface plate. Than map out the surface. I being a newb find it amazing the cast moves around so much...

 

[Pete F]

I am going to try to level it with 3 points on the surface plate. Than map out the surface. I being a newb find it amazing the cast moves around so much...

I don't follow at all why you're doing this, or even what this whole thread is about I'm afraid. You have machined a part, in this case a straight edge, to the limits of the accuracy of that process and that machine. You then measured it (using spotting blue) and shown the inherent inaccuracies of the machine using a far more sensitive measuring process. Nothing remarkable about all that and the print you're getting looks about typical to me. If you want to feel more warm and fuzzy about the milling then lay your ink on much thicker and desensitise the measuring process to make it less accurate. If you otherwise want a better print, use a more accurate machining process, and from the point you're at there it would normally be scraping.

FWIW, in the time taken to write up what may be happening, come up with all manner of BS theories regarding Airy Points, etc etc etc, you could have scraped that little straight edge in 5 times over!

 

[RC99]

Don't worry Pete, I read this last night and was wondering what the point was..

It is rough machined on a mill.... Now you get your hands dirty and scrape, scrape, scrape...

No point to a straight edge if it is not flat, only way to get it flat flat is scraping..

Plus it is only a baby straight edge..

 

[Demon69]

Get all your machining done first.
Hang it up an beat it with a dead blow. At the very least youll be 'stress relieved'
Slap it on a plate and see if you can get feeler gauges under it. Anything less than .006 youre golden.
Blue it up and scrap it like you hate it, centres out first n coming in from the edges.

If youre not roughed in 20 minutes, click here and rock that shop.

 

[bmikkalson]

I don't follow at all why you're doing this, or even what this whole thread is about I'm afraid. You have machined a part, in this case a straight edge, to the limits of the accuracy of that process and that machine. You then measured it (using spotting blue) and shown the inherent inaccuracies of the machine using a far more sensitive measuring process. Nothing remarkable about all that and the print you're getting looks about typical to me. If you want to feel more warm and fuzzy about the milling then lay your ink on much thicker and desensitise the measuring process to make it less accurate. If you otherwise want a better print, use a more accurate machining process, and from the point you're at there it would normally be scraping.

FWIW, in the time taken to write up what may be happening, come up with all manner of BS theories regarding Airy Points, etc etc etc, you could have scraped that little straight edge in 5 times over!

U are correct, but I was wondering if it was my ficturing or the machine. I am very lazy, and would rather recut than spend my night making little coffee ground chips. But this is why I come here to the pros, so I thank you all for the hand holding. Btw, I've been to Brisbane beautifully country.

 

[bmikkalson]

Get all your machining done first.
Hang it up an beat it with a dead blow. At the very least youll be 'stress relieved'
Slap it on a plate and see if you can get feeler gauges under it. Anything less than .006 youre golden.
Blue it up and scrap it like you hate it, centres out first n coming in from the edges.

If youre not roughed in 20 minutes, click here and rock that shop.

I was thinking of being clever and throwing it in my buddies shot blaster. Not sand but steel shot...

I probally over thinking this, I had the SE out side and rep blued ,changed quite a bit. It's 7 degrees here.

 

[PDW]

Don't worry Pete, I read this last night and was wondering what the point was..

It is rough machined on a mill.... Now you get your hands dirty and scrape, scrape, scrape...

No point to a straight edge if it is not flat, only way to get it flat flat is scraping..

Plus it is only a baby straight edge..

Yeah - I have 2 600mm long ones sitting on my big mill table. One is as-machined, the other has had 2 passes over it to break up and remove the milling marks. I haven't even bothered putting it on the plate yet, got to get rid of the milling marks first to get any sort of decent print.

Eventually, to get anywhere, you just have to do it, and I doubt there's anyone as lazy as I am.... which is why those straight edges are unfinished as I don't really need them yet.

PDW

 

[gbent]

...the reason people scrape at a given point is ... because at a certain point scraping is just way faster and more efficient that trying to machine any closer. ...

smt

What he said!

If you can't scrape that straightedge twice all over and an extra 4 or 6 times on the blue spots in a half hour and enjoy your time you will never finish that straightedge.

Don't machine the surface to smooth, it makes it a bitch to scrape. It will rough in easier if there are some tooth marks. A sparked out Blanchard ground surface is about the worst, and I doubt if CBN finished is far behind.

 

[CBlair]

What he said!

Don't machine the surface to smooth, it makes it a bitch to scrape. It will rough in easier if there are some tooth marks. A sparked out Blanchard ground surface is about the worst, and I doubt if CBN finished is far behind.

Is that because the tool wants to skate across the smooth surface instead of digging in?

Charles

 

[TGTool]

Is that because the tool wants to skate across the smooth surface instead of digging in?

Charles

Cue up Skaters Waltz. A one and-a two-uh https://video.search.yahoo.com/vide...:s,v:v,m:sa&hsimp=yhs-001&hspart=mozilla&tt=b

Stroke-stroke and-uh stroke-stroke.

You'll be done in no time.

 

[CBlair]

Cue up Skaters Waltz. A one and-a two-uh https://video.search.yahoo.com/vide...:s,v:v,m:sa&hsimp=yhs-001&hspart=mozilla&tt=b

Stroke-stroke and-uh stroke-stroke.

You'll be done in no time.

Are you sure you were trying to answer me?

Charles

 

[bmikkalson]

Ok, I have it hinging at 30 percent, has a small hole in the center still. Probably have 20 cycles and 2 hockey periods of time in it.
The RA finish was measured at 21. I was getting some chatter.
Here is a pic of how efficient of stock removal I had per pass.
http:// [URL=http://s28.photobucket.com/user/bmikkalson/media/Mobile%20Uploads/IMAG0516.jpg.html][/URL]

 

[ironsmith89]

Honestly on a part that size if I could machine it to let's say .003 flatness I would be happy with that and start scraping. You could piss around for weeks and maybe cut that in half, maybe, but you could have been done scraping by then too. An error of .003 might seem excessive but I'd much rather scrape .003 off of a small SE like that than say a four footer, there's less surface area. Perfect your rough scraping skills, it's just as important as finish scraping. As far as finish, that fuzzy flycut finish is ideal for a scraper to bite into, like using a lathe file on a lathe, if you turn your part and put a high shine with high surface footage and low feed, the file only skates over the surface. However if you bump up the feed rate and give the surface some scruff, the file almost seems to stick to the part it bites so well. A scraper behaves the same. Just my two cents.
Chris German

 

[gbent]

Is that because the tool wants to skate across the smooth surface instead of digging in?

Charles

Yes. Dull cutters are also bad.

 

[Richard King]

After the St. Paul Scraping Class started a few months ago, I said one of the students said after 5 minutes " I can't do this scraping" ....showed he was super impatient and complained and complained wanted an instant solution and short cuts. Every time he blued up his test part he either asked Denny Danish or I what to do next. Guess who he was??? Ben... He was the host and had a lot to do to help organize the shop and find things for the other students who needed a tool or fasteners, so in the beginning he probably did not get as much attention as some of the others.

As I stated he would ask "what do I do next" every time he blued up his plate and never thought about it as the others did. I now feel I let Ben down early on by letting Dennis show or tell him each time. I need to go do a 1 & 1 with Ben so he doesn't have to ask the forum or anyone "what should I do next" questions.

I sold 3 SE's to another student who took the class and he has not called me once on what to do next. But he is a professional Machinist. Ben isn't and learning how to be a hobby machinist, but works in an auto body shop, so he knows how to be patient. Just need to know scraping is not easy and takes lots of practice.

I hope I don't come across as picking on Ben, but I also think he needs to learn from making a few errors on his own and not get a answer for every little thing that comes up. I live less then 20 minutes from Ben's shop and could help him. I had let him use a BIAX and scrapers after the class to finish his angle plate. I hope I'm not going to embarrass you Ben here. Ben was calling me a lot asking questions and I told him i had never received so many questions from any student after the class. He received a DVD and work booklet, sat through the class had the same instruction I have given to thousands of students and never had so many questions after a class. During the class he asked Dennis and was following his suggestions...They seemed to become friends and I know Dennis has helped him with his lathe saddle machining and scraping. So Ben has lots of help locally.
As you can see, I am frustrated with Ben's questions and photo's here as it seems as if he did not take the class.

If you had been listening Ben, I told you if it is more then .005" out get it machined or don't have a machine to machine it on. If it is .005" or lower, scrape it. You could lay the SE on the plate and try to slide in a feeler gage and discover what you have. JUST like the plate you learned to scrape in the class.

We could never get together, when you called me to help you but talked to you on the phone several times. most of the time I was out of town or busy. I found a shop near us plus the fellow is Larrs a member here to mill the saddle and SE. He is a welder/fabricator/machinist who could have machined the saddle and SE, but I was out of town or could not see real good.

The last 25 days and I still have another 10 to recover from my surgery. I do not have any safety or prescription glasses now, I am nearsighted now so I can't see good enough to scrape now. I go to the eye DR tomorrow and hopefully by next week I will have the glasses to do a 1 on 1 with you again.

Ben, you need to be patient and take some notes, so when you ask questions in here you will get some good answers. Rich

PS: I always tell my students to ask me for help, but when I answered the same question 3 times and then seeing these questions here I get a bit crabby. .

 

[Richard King]

To me I prefer a ground surface because it means less scraping. If you can get it ground to less then a .001 and using a Biax or even a handscraper one 2 or 3 passes checkerboard scrapes and your down to scraping for points. I would scrap all the surface to break thru the surface and as I said in other threads hang it from a rope and wring it with a 2 x 4 or a dead blow hammer. You will have to scrape one side to 20 PPI and then wring it and scrape the other side to 20 PPI Wring it and go back to side 1 and scrape as good as you can get it and then go to the 2nd side and finish it. You never said what the vendor did for stress relieving. This is super important to follow up on. If you guys are having a hard time to get thru the work or machined hard surface at first, grind a smaller tip angle. A 60 to 90R and a 0 to 2 deg neg tip or roughing and a 60 to 90R neg 5 deg for softer CI and finishing (All this info in in your work booklet Ben)

Ben you also need to get a demagnetizer like this one. Put a shop rag on it and slide the SE over it a couple of times.

Demagnetizer Tools Such as Dies Cutters and Punches New | eBay

That SE must be made out of ductile as it has lots of fine slivers as shown in the one picture. You should keep an eye open on Ebay or ask on here under a wanted for a BIAX Scraper. Rich

 

[Forrest Addy]

De-magnetise? Got a welder? Your welder is also a demagnetizer. Shift it to AC max current. Gotta b AC. No DC: that makes it worse.

Pull out all the cable and make coils of the stinger and the ground leads large enough to pass the article through. Tie them with string or light rope. Bring the coils together so the eyes align and short the stinger to the ground so the current passes from coil to coil in a straight line and not a U turn. You want the magnetic fields to reinforce not cancel.

Slip the straight edge casting whatever in the eye of the coil and have a helper snap on the welder. Pass the straight edge all the way through, from one end to the other. You should feel a vibration in your fingers. When you get bored or five minutes passes or the welder smells hot pull the article out of the coil and snap the welder off.

Grab a pinch of dust from under the grinder and toss it at the corner of the article. Most should fall off and the few whiskers that stick should wipe off. If not do another pass through the demag - or find a bigger welder with more lead.

This work 95% of the time takes a half hour if you have the string handy, and cost nothing but a Kilowatt hour.

Oh yeah, big buzzy magnetic fields. Remove all credit cards, mag based ID, your phone etc from your person and stash them in the house. Fail to do so and you may become bereft of entry into the economy. Probably not, but why take chances. I sat on my stinger lead to weld for an hour and erased my debit card so it happens.

 

[bmikkalson]

Rich, the point of this thread was, figure out why the inconsistent results. As it turns out the problem could be a number of things. Internal stress, cutting bit,fixture,etc. Most trades take 2 Years to get your feet wet, 3 days is a good start to sharpening a scraper etc. But if you want professional results it is only going to scratch the surface. I want results.
Did you set your help free on a monarch lathe after 3 days and head up to the cabin?
rich, take it easy, if I'm asking a question it's cause I wanna know. Not so I can humor you with simple minded crap to make u feel better.
If you wanna come to my domain I will teach you how to section a car in 3 days. Than we see who is not paying attention when your doors don't shut and water leaking in. ( joking rich)

I have spent a couple nights with Dennis, and really feel like I learned a skill when he leaves. Dennis is a great sensai much better than your average instructor. I enjoy this type of work, and I know Dennis knows he is not wasting his time. I want to learn...

Rich you have been doing this all your life u have forgotten more than I know. If you keep getting excited I'm going to be getting a biax from your estate sale. (I kid)

If you desire you can swing by with a biax and check out my millrite. I got all sorts of questions for you. Lunch is on me.

 

[JST]

Most trades take 2 Years to get your feet wet, 3 days is a good start to sharpening a scraper etc. But if you want professional results it is only going to scratch the surface. I want results.

I have no idea where you are in the learning process, so I could be way off base here. I'm just going by what I read here.

If you need results now, it may be time to do some "checkbook scraping".

It's going to take a while, regardless.... That's a really GOOD reason to start off with something simpler than either a straightedge or a complete machine.

The straightedge is basically simple geometrically, but getting the finish quality is not. The machine obviously has both the mechanics of getting a good surface plus the alignments.

Myself, not being able to get to any of the teaching sessions, I've basically taught myself, and it's a good thing I have no pretensions to doing this as a career, since there is a ton of stuff to learn. I have been doing it off and on for 7 years or more (don't remember for sure), and I learn something new every time I pick up a scraper. Often something important...

Frankly, if you want to learn it, classes and instruction only do so much... They speed up learning the lessons. They do NOT speed up learning the 'doing".

The only real way to get to be any good at it is to DO it, spend time at it. THEN if you can, get someone to correct your mistakes. You will "get it" much better then than now, and instantly be able to see what happens.

Just getting the surface is actually quite involved....doing it in a reasonable time is more involved, getting a GOOD surface for a straightedge is even more so, there are a lot of ways to NOT get what you want, both in the detail mechanics of working with the scraping tools, AND in the "strategy". Much of it will be in the "strategy", which has levels, local strategy, and overall strategy.... etc, etc..

You do not want to hear this, probably.... but go get some CI pieces, and scrape them flat to a 10 ppi finish. Then go for a 20 ppi finish, then a 30+ ppi finish.... Then do the next one. After you do about 4 of them, go back to the SE and it should be a lot easier to see what you are doing, and what to do next. if you can get someone to look at them as you go along, you will be even better off.

But it's gonna come down to YOU pushing the tool, and knowing what to do next. And that comes from doing. Nobody can hear about it and then start doing reference quality scraping... Nobody I know, anyhow.

I have no idea how to get quick results starting from near zero, unless you pull out the checkbook.

 

[vettebob]

Hi I'm Bob, The Guy with the monarch you referred to. I asked some questions about scraping and watched Richards dvd before the class. Then started scraping on my straight edge I would beat the heck out of it with a dead blow after every 4 passes. Then when we had the class I had lots of questions about the things I didn't understand. After about another 4 hours I had the 18" camel back scraped in. Point is it takes practice to get results I probably made 80 passes ( I have a shattered wrist and can't exert much force I struggle to get 2 tenths deep scrapes) 2/3 of them done incorrectly prior to the class But I learned. The second day of the class I scraped in my compound by hand. On the third day Richard suggested I use his Biax I did not practice with it on the second day like the other students because I didn't plan on buying one. After 15 min instructions from Richard I was using the Biax on my saddle. After the 4th day of class Richard loaned me his biax while he went to his cabin and I finished scraping everything. I even went back and touched up my straight edge. While I an not an expert in scraping I am getting ready to start scraping my tailstock in by hand and expect good results. Here are some pics of what I scraped. While being far from an expert I would be happy to help out. Bob


PS your shot blaster idea my not be a bad one before you scrape too much. As you know shot basting is used for stress relieving after welding. Bob