A Scraping Newbie Has The First Of Many Questions

[Richard King]

Setting it on 3 points in my opinion is a mistake. I am a big believer in 3 points, but not in this situation.
Bluing it up part to plate is the best way. Your part looks thin and you may never be able to get 40 ppi on a flimsy part. set it on the plate and hinge it and hold your hands on it for 1 or 2 minutes and the heat of your hand will change the hinge. Also your stroke is to short and looks not deep enough. It's like trying to scrape a tapered gib to 40 ppi. Was the part high temp stress relieved. I have taught hundreds of people to scrape on here and in person. No offense, your not listening to me, your making something so simple difficult because you over thinking this.

 

[Richard King]

I have a class in October and if your still having issues, Come to it and I will teach you how in 2 days no charge.

 

[M Kiser]

I have a class in October and if your still having issues, Come to it and I will teach you how in 2 days no charge.

That is certainly generous! I may have to take you up on that.

 

[Bakafish]

My suggestion of measuring the surface while on 3 points was (as I think I explained) so you could have a secondary understanding (sanity check) of what may be happening with that surface other than trying to interpret a potentially bad print, something it seemed to be effective in doing.

Step scraping isn't called for, it wasn't what I was suggesting this measurement was for. I think the issue is (as I hear from more experienced scrapers is often the case) prematurely moving to point scraping when the base hasn't yet been fully established. Overall it looks quite good, but it doesn't look flat enough to start point scraping either. The hinging issue is telling you that as well, it may be helpful to put actual marks on the top at the expected points of rotation (claimed by some to be at the Airy points, but I suspect to be the point of minimum sag 0.5536 x L or something related to that. Would love to have a good mechanical engineering discussion on this.)

Mr. King's advice about the stroke length and depth seems prudent to follow, us newbies tend to worry about going too deep and hard fearing to damage the workpiece but the very shallow scrapes actually work against us. The shallow divot prints are harder to interpret, more sensitive to ink film layer fluctuations on the master surface and the contact points are in constant flux with no consistency between prints making you chase your tail. Deeper (and longer) scrapes minimize the actual surface area you are working on across each round of scraping as they will take an area out of play for several passes, allowing you to really isolate the high points and get them consistently distributed.

 

[M Kiser]

After considering the advice given by Richard and Bakafish as well as having a desire to get rid of some ugly corner scratches I decided to rough the whole thing down and start over. Attached are pics showing the result. The print is a bit heavy but it was done after the fact just for the pics so it had no effect on my decision to call it done. The last several passes were strictly done by dive bombing. No criss-cross.
Comments and/or suggestions are welcome and appreciated!

 

[M Kiser]

Here is the finish I got by dive bombing the last several passes. While I am confident in the accuracy I'm not crazy about the appearance. Would a uniform pass of criss-cross scraping improve things? I'm reluctant to do anything more for fear of screwing it up. Is my fear unfounded?

 

[Richard King]

After considering the advice given by Richard and Bakafish as well as having a desire to get rid of some ugly corner scratches I decided to rough the whole thing down and start over. Attached are pics showing the result. The print is a bit heavy but it was done after the fact just for the pics so it had no effect on my decision to call it done. The last several passes were strictly done by dive bombing. No criss-cross.
Comments and/or suggestions are welcome and appreciated!

Looks super !! 50 to 60 PPI accept the lefts side. Remember PPI -s so the SE lasts longer and accuracy. you could have the same accuracy with 20 PPI but it would wear out faster.

 

[Richard King]

Here is the finish I got by dive bombing the last several passes. While I am confident in the accuracy I'm not crazy about the appearance. Would a uniform pass of criss-cross scraping improve things? I'm reluctant to do anything more for fear of screwing it up. Is my fear unfounded?

I believe I told you about my 5 Richard King Scraping Rules and you've mastered it.
1. after you have the PPI to 20 and its accuracy is with-in .001", start to scrape individual high low spots in diagonal lines. X-X-X- if they touch side to side you have made a long hole
2. the next line of individual line on the same diagonal direction have it separated from the prior line 1/8", if they touch top and bottom you've made a long hole.
3. Check you depth of the scrape pocket, Minimum of .0002" max of .001"
4. While bluing hinge or pivot the part and that should hinge at 30% from each end, That shows flatness
5. Be sure after you've scraped and before you stone off the burr, clean off the bluing with mineral spirits, brake cleaner or a fast dry solvent then stone only the burrs and then wipe the part with you hand so if there is any crud or un-stoned burrs, you can feel it with bare skin.

As you discovered having a sharp blade and ground to smaller radiuses the more points you get is also a "trick to the trade" Excellent work A+++

 

[Bakafish]

Here is the finish I got by dive bombing the last several passes. While I am confident in the accuracy I'm not crazy about the appearance. Would a uniform pass of criss-cross scraping improve things? I'm reluctant to do anything more for fear of screwing it up. Is my fear unfounded?

Don't mess with it once it is printing accurately. The dive bombing can lead to an inconsistent pattern, but I think rescraping over the top is likely to ruin some of the accuracy you worked so hard for.

Flaking or 'frosting' for appearance may be a way to get a more consistent finish, but I suspect there is a tradeoff, especially if it isn't a ways or other loaded bearing surface. I've just left mine looking random, the crystalline growth look has grown on me.

 

[M Kiser]

I believe I told you about my 5 Richard King Scraping Rules and you've mastered it.
1. after you have the PPI to 20 and its accuracy is with-in .001", start to scrape individual high low spots in diagonal lines. X-X-X- if they touch side to side you have made a long hole
2. the next line of individual line on the same diagonal direction have it separated from the prior line 1/8", if they touch top and bottom you've made a long hole.
3. Check you depth of the scrape pocket, Minimum of .0002" max of .001"
4. While bluing hinge or pivot the part and that should hinge at 30% from each end, That shows flatness
5. Be sure after you've scraped and before you stone off the burr, clean off the bluing with mineral spirits, brake cleaner or a fast dry solvent then stone only the burrs and then wipe the part with you hand so if there is any crud or un-stoned burrs, you can feel it with bare skin.

As you discovered having a sharp blade and ground to smaller radiuses the more points you get is also a "trick to the trade" Excellent work A+++

Took me long enough, right? Thank you so much for all of the help you have given!!!
You mention the use of solvent to clean up after scraping. I’ve been using Windex like the folks in most of the scraping videos I’ve watched. Is that a problem? High latent heat of water and all?

 

[Yan Wo]

Here is the finish I got by dive bombing the last several passes. While I am confident in the accuracy I'm not crazy about the appearance. Would a uniform pass of criss-cross scraping improve things? I'm reluctant to do anything more for fear of screwing it up. Is my fear unfounded?

Since you got a "Like" from Richard King, I'd call it done!

 

[Richard King]

I used Windex for years and taught my students to use it too. As you know many on You Tube have taken my class. Since I started to teach in my home shop, I find the fast dry solvents work better. They cost more though. Both work.

 

[Richard King]

I have been calling the last technique "dive bombing" the last 20 years, but I didn't always call it that Originally I called it "Point Spotting" or BIAX called it "Technique 40". I was teaching a class at a Detroit Diesel Allison plant (GM) in Indianapolis and I had a real jokester in the class. As he was Point Spotting I heard him sayng "a whistle sound you hear on TV when a bomb drops from a plane and booms...I walked over to him and he said "I'm dive bombing", so it stuck. When I was teaching inside the BIAX Scraper factory 1/2 the students speak English, So when I demoed Dive Bombing, I said "Stuka" then made the siren sound those WW2 planes made, they understood.

 

[Richard King]

Since you got a "Like" from Richard King, I'd call it done!

Yan Wo, learned to scrape from Alex King, my son. Yan hosted the Salt Lake class. I was going to teach it, but had an Emergency surgery. Alex taught my June and July class because of my broken arm. Hopefully I will be able to teach the Oct & Nov classes and the 2024 classes.

 

[Yan Wo]

Yan Wo, learned to scrape from Alex King, my son. Yan hosted the Salt Lake class. I was going to teach it, but had an Emergency surgery. Alex taught my June and July class because of my broken arm. Hopefully I will be able to teach the Oct & Nov classes and the 2024 classes.

Hi, Richard. You're correct that I learned scraping from Alex, but it was Doug at Lean Machine Works who hosted the class. I don't know if he's on PM. I suspect not. Are you here Doug?

 

[M Kiser]

I used Windex for years and taught my students to use it too. As you know many on You Tube have taken my class. Since I started to teach in my home shop, I find the fast dry solvents work better. They cost more though. Both work.

Better in what way? Less temperature change to the part or better removal of the ink? I was astonished at the effect of unequal temperature in the part. It would hinge perfectly after a long session of scraping and after sitting overnight the hinging was totally different.

 

[Richard King]

Better in what way? Less temperature change to the part or better removal of the ink? I was astonished at the effect of unequal temperature in the part. It would hinge perfectly after a long session of scraping and after sitting overnight the hinging was totally different.

Your asking an anal question. Just find a way that works for you. If you don't remove the ink before stoning, the stone gets plugged up. hand temp just holding a part to long is enough to change the swivel or hinge point. wear some cotton or deer skin gloves.. One issue I see a lot, once you learn to scrape 40 PPI - you want to scrape every thing that good. Remember most machines will work with 20 PPI. Only Jig Bores and inspection tools need 40 PPI

 

[M Kiser]

I think I will paint this and call it done. I sure hope painting won’t cause distortion!

 

[Richard King]

Remember to hang it from an eye bolt on the end. I have found this is the best way to store them. You can set it on a round shaft to find the balance point and drill and tap a hole there on the end.