A Scraping Newbie Has The First Of Many Questions

[M Kiser]

It's been a while since I posted anything regarding my long and arduous journey into the world of scraping, but I've not been totally idle. Some email communications with Richard King regarding the "Technique 40" from the Biax book have been very helpful. Using these techniques I have scraped my practice piece (victim?) as shown in the attached pics. Both show a decent PPI count, but I don't feel like the "Percentage Of Contact" is as high as it should be. How should I try to improve that? My first thought is to work on it with a whetstone until the size of the blue spots increases to the desired percentage of contact, but everything that I have read says that whetstones are to be used for deburring post scraping and nothing more. Any advice?

 

[Bakafish]

I'm still seeing distressing scratch marks. Some look like from the corner of the blade (increase the radius on the corners to help with this) but some are parallel 'claw' marks that feel like blade edge quality. I think until you get a handle on this, the quality is going to suffer.

I'm not sure 'percentage of contact' should be a goal unto itself, unless load bearing is critical. You aren't using a straight edge as a stamp, you slide it to ensure the points can transfer to the other surface with broad coverage. As newbies we should be focusing on the basics, getting the roughing correct so that coverage is uniform, and finish scraping so that we have sufficient points and pocket depth where that is required. If you get those things right, then increased percentage of contact is likely to come out of that naturally.

Stoning (other than to debur between sessions) is imprecise, you are more likely to do more harm than good, lapping would be a better option if you want to do abrasive removal, but that feels orthogonal to the goal of good scraping.

 

[Richard King]

Looks GREAT. Like I told you practice makes perfect. You could do some precision stoning if you had a Diamond ground stone like Spencer Webb or Lance Baltzley, or Professional Instruments (St.Louis Park, MN) sells. Or leave it alone as it will wear in. Most new machine builders run the machine for a few days so the ways or scraping settles in.

 

[Richard King]

I just received my ink from England via USPS and I have some paint pigments that I'm going to experiment with in the next few weeks during my next class. I just had one of my next class in 10 days students cancel 20 min ago, so if some ones to learn in person I have 2 open spots here in my shop in Minnesota.

 

[M Kiser]

I'm still seeing distressing scratch marks. Some look like from the corner of the blade (increase the radius on the corners to help with this) but some are parallel 'claw' marks that feel like blade edge quality. I think until you get a handle on this, the quality is going to suffer.

I'm not sure 'percentage of contact' should be a goal unto itself, unless load bearing is critical. You aren't using a straight edge as a stamp, you slide it to ensure the points can transfer to the other surface with broad coverage. As newbies we should be focusing on the basics, getting the roughing correct so that coverage is uniform, and finish scraping so that we have sufficient points and pocket depth where that is required. If you get those things right, then increased percentage of contact is likely to come out of that naturally.

Stoning (other than to debur between sessions) is imprecise, you are more likely to do more harm than good, lapping would be a better option if you want to do abrasive removal, but that feels orthogonal to the goal of good scraping.

The scratches are indeed from the corner of the blade. That happened some time ago and since this is only a practice part that won't be used for anything I just left them. It's a good reminder to have good lighting before you scrape!

Regarding the "claw" marks, I assume that you are referring to the parallel marks that are in the direction of the scraping strokes? I put it under a microscope at 10x and it seems like they are only on some of the scrape marks. All of the scrape marks have very fine chatter marks perpendicular the the stroke, but I believe those are normal and are the reason you alternate directions. I don't know what to think about the "claw" marks. The scraper edge is honed to 2000 grit already and looks really smooth at 25x. Could I be getting some edge buildup? Would the application of an oil film prior to scraping help?

On the issue of contact %, my ultimate goal will involve the ways on a lathe, so it actually will matter.

 

[Richard King]

Buy a demagnetizer and demag your blade. A lot of those small scratches are from small iron chips on the tip of the blade. Your going to get small scratches and a corner gouge from time to time. It happens and on a underside surface no one will ever know. Power scraping is not perfect compare to hand scraping as it will get small chatter in the scrape mark. If you want to not see those small chatter marks, hand scrape the last couple of times. That's what Sip use to do. Power scrape until the last couple of passes and then hand scrape it to get your "signature" look. Sip pull scraped it. Also in the last class I taught at a Japanese Okamoto and Mitsui distributor and rebuilder, that is there plan to increase their productivity.

 

[M Kiser]

Looks GREAT. Like I told you practice makes perfect. You could do some precision stoning if you had a Diamond ground stone like Spencer Webb or Lance Baltzley, or Professional Instruments (St.Louis Park, MN) sells. Or leave it alone as it will wear in. Most new machine builders run the machine for a few days so the ways or scraping settles in.

Buy a demagnetizer and demag your blade. A lot of those small scratches are from small iron chips on the tip of the blade. Your going to get small scratches and a corner gouge from time to time. It happens and on a underside surface no one will ever know. Power scraping is not perfect compare to hand scraping as it will get small chatter in the scrape mark. If you want to not see those small chatter marks, hand scrape the last couple of times. That's what Sip use to do. Power scrape until the last couple of passes and then hand scrape it to get your "signature" look. Sip pull scraped it. Also in the last class I taught at a Japanese Okamoto and Mitsui distributor and rebuilder, that is there plan to increase their productivity.

I will make it a point to demag the blade periodically. So am I right to assume that you think that that scraping would be suitable for the HLV-H cross slide and compound? First I have to scrape my straight edge, but the lathe is the final goal.

 

[Richard King]

Sure, I used to rebuild Hardinges, no problem. You will need a 45 deg, to fit in the dovetails.

 

[M Kiser]

Sure, I used to rebuild Hardinges, no problem. You will need a 45 deg, to fit in the dovetails.

My 1978 era HLV-H actually measures 60 degrees. And I'm glad because I would have had to re-machine my straightedge casting!

 

[Richard King]

Rookies think you have the exact angle but you don't and scrape the flat and dovetail angle at the same time. You scrape the flats first getting them co-planer to each other and the bed, leaving the front flat .0002" higher. Then individual dovetails independent to the flats. The front dovetail needs to be scraped square to the bed. Minus or out of square .0002" so when you face a part the shaft gets concave. I used to rebuild the Hardinges for Milton Gramquist the Minnesota distributor and taught the scraper techs for Terry Iverson Company in Chicago.

I know how to do it as I worked with the Hardinge factory using their spec's and tools they sent me from the factory. When you scrape dovetails you tip the SE up so the 45 deg. angle to the 55 or 50 or 60 degree angles. Have to get the feel by rocking the SE until up and down to get it flat and then lift it up off the bottom vertex and hinge or pivot points. Are you going to have the bed plate ground? You need to be a detective and measure the top flats so they are parallel or co-planer to the bed and under the saddle if the Nylon wear strip is OK or worn.

Some of the very old machines didn't have the .010" under saddle and rear dovetail wearstrip, so you need to take it apart too. Hopefully you have a manual as Hardinge has great books tell how to dismantle the machines.

This should be a good learning thread for all the members and readers n the future. Start a new thread when your ready. One super thing Hardinge did is they have the bed sitting on 3 points.

 

[Bakafish]

Thanks for clarifying on the marks I was seeing. As far as chatter, you might want to experiment with the rake angle of the blade, positive 5 degrees is the standard, but different materials may need a more or less aggressive cut.

For geometry checks of the dovetails, I've seen some experienced fitters using a pair of the same sized, closely matched precision pins to great effect. I think it's really hard to check the parallelism otherwise, as the angles don't give a great reference point to measure from.

 

[Tyrone Shoelaces]

You can still get the “ Stuart’s “ micrometer blue over here. It varies between £4 and £5 a tin, and a tin goes a long way if you’re not scraping planer tables. In fact they’ve really branched out and started making it in a red colour as well as blue !

I used it most of my working life and I can recommend it. We used to have another make of bedding blue over here but I can’t recall the name now. That wasn’t very good.

Regards Tyrone

 

[Richard King]

I just received 4 tins of Stuarts Marking Blue Micrometer Engineers Bluing. I ordered from RDG Tools in West Yorkshire, UK With Postage it was UK 29.42 pounds or $36.56. I'm going to test it during my next class in 9 days and I'll report back.

 

[Tyrone Shoelaces]

I just received 4 tins of Stuarts Marking Blue Micrometer Engineers Bluing. I ordered from RDG Tools in West Yorkshire, UK With Postage it was UK 29.42 pounds or $36.56. I'm going to test it during my next class in 9 days and I'll report back.

Previously it was made in Clevedon, Somerset I think. The old tins used to state - “ High Class Work Demands The One And Only - Stuart’s Micrometer Blue “. I trust the new makers have stayed with the old formula. Incidentally Mytholmroyd where RDG Tools are based is about 10 or 12 miles from me in the heart of what used to be big machine tool country.

There’s another company over here called “Walters And Walters” that sell the tubes of “ Dykem “ Hi-Spot bedding blue. That’s £8.95 for a .55oz tube. They also sell the “ Stuart’s “ blue. Funnily enough the blue tins cost £4.08 and the red tins cost £6.18. The tins are the same size.
Regards Tyrone

 

[M Kiser]

Rookies think you have the exact angle but you don't and scrape the flat and dovetail angle at the same time. You scrape the flats first getting them co-planer to each other and the bed, leaving the front flat .0002" higher. Then individual dovetails independent to the flats. The front dovetail needs to be scraped square to the bed. Minus or out of square .0002" so when you face a part the shaft gets concave. I used to rebuild the Hardinges for Milton Gramquist the Minnesota distributor and taught the scraper techs for Terry Iverson Company in Chicago.

I know how to do it as I worked with the Hardinge factory using their spec's and tools they sent me from the factory. When you scrape dovetails you tip the SE up so the 45 deg. angle to the 55 or 50 or 60 degree angles. Have to get the feel by rocking the SE until up and down to get it flat and then lift it up off the bottom vertex and hinge or pivot points. Are you going to have the bed plate ground? You need to be a detective and measure the top flats so they are parallel or co-planer to the bed and under the saddle if the Nylon wear strip is OK or worn.

Some of the very old machines didn't have the .010" under saddle and rear dovetail wearstrip, so you need to take it apart too. Hopefully you have a manual as Hardinge has great books tell how to dismantle the machines.

This should be a good learning thread for all the members and readers n the future. Start a new thread when your ready. One super thing Hardinge did is they have the bed sitting on 3 points.

I will definitely start a new thread when I get there. First I have to scrape my straight edge. My HLV-H has what appears to be .010" Teflon under the saddle. And it is in tatters so replacement is certainly necessary. Did Hardinge scrape the Teflon? I can't tell because of the condition, but .010" seems pretty thin to scrape. Could I scrape the saddle for geometry and rely on the consistency of the Teflon for an accurate fit or should I mill away enough cast iron to allow a thicker piece of Turcite or similar that would be scraped to fit after gluing? Also, you mentioned getting the front flat .0002" higher. I assume that is the one closest to the headstock?

 

[Richard King]

I can't remember what they call it...but Hardinge bonds the Nylon strip on the bottom of the saddle- It's heated somehow. Iverson Rebuilding send the saddle back to Hardinge and they bond it on. I always machined off aprox. .045" and glued on .047" Rulon 142 plus the glue is .003 to .005" thick. I set it on the bed plate to dry. I also used Moglice a few times and it work slick as heck. Yes the Chuck side because that's where the dirt gets under the wipers first. I am assuming your wipers are steel with a spring above them that pushes them down. Or the newer machines used a molded rubber wiper. I always scraped the Turcite B /Rulon 142. I don't know for sure if Hardinge scraped the Nylon, I suspect they did? As if it's like Rulon or Tucite they don't guarantee it to be (+ -) .002" thickness. Thats what makes using Moglice so cool as all you do is 1/2 moon flake it. You super glue on 1 x1" Moglice pads on the saddle in 4 place and 2 on the dovetail and scrape it to get the geometry right and then block the edges and squirt in liquid Moglice where it drys. If you haven't heard of Moglice google Moglice.com. You could call Hardinge and ask them and ask them what they charge to do the heat bonding. Be sure you take off the sheet medal plate on the back of the saddle to access the Bujur metering units that are under the alum. plate. Sometimes the copper pipes nee to be pulled out. I used a vise grip clamped to the steel bushing behind the O-ring and slide in a screw driver to pry out the Vise grip. That will pull out the copper tubes.

 

[M Kiser]

I haven't posted in a while, but I have been scraping my Martin 18" straight edge that will be used for the HLV-H restoration. Images are attached.

Here are some rookie questions that I'm hoping for answers to:

The PPI count seems to me to be around 20. But I'm not even sure what counts as a "point". Is it only the mirror shiny spots? Or does it include the various shades of blue from pale to dark? I would like to increase it to around 30 or even more, but I am frankly clueless about which markings count as a point. And what about the large areas that consist of various shades of blue with no gaps between them ? Are they one point or are they multiple points? I have read of the need for cutting large points into smaller points but am not sure how to interpret these "points" that consist of multiple shades. Are they one collective point, or are they a separate point for each shade of blue?

 

[Richard King]

I wish you had laid the gage on the first one. On the lower left corner I guessed at 1 sq. inch and I counted 36 PPI and on the right one 16 PPI. One thing you have to remember before counting the surface you need 100% of the surface have high spots on it. If one area has no high spots it's not ready or finished. You only count when 100% has points in it. Look at the thread I did on Pictures the April scraping class as Will scraped his Foster 36" camel back to 40 to 50 PPI and 40 to 60% POP. https://www.practicalmachinist.com/...ping-martin-se-foster-se-angle-blocks.412456/ If you have a long narrow high spot and another one touches it, that is one point. If an ink spot is less then * that isn't a high spot. The high spots all need to have the same color. Your scraping look good, real good for doing it on your own. Will had to learn a few things during the class he didn't learn on his own. He did a thread like this one and I am sure he could have figured it out on his own, but I was happy I helped him learn how in the 5 day class. He was scraping on his own on the 4th day. Hopefully he will help you too.

 

[M Kiser]

I wish you had laid the gage on the first one. On the lower left corner I guessed at 1 sq. inch and I counted 36 PPI and on the right one 16 PPI. One thing you have to remember before counting the surface you need 100% of the surface have high spots on it. If one area has no high spots it's not ready or finished. You only count when 100% has points in it. Look at the thread I did on Pictures the April scraping class as Will scraped his Foster 36" camel back to 40 to 50 PPI and 40 to 60% POP. If you have a long narrow high spot and another one touches it, that is one point. If an ink spot is less then * that isn't a high spot. The high spots all need to have the same color. Your scraping look good, real good for doing it on your own. Will had to learn a few things during the class he didn't learn on his own. He did a thread like this one and I am sure he could have figured it out on his own, but I was happy I helped him learn how in the 5 day class. He was scraping on his own on the 4th day. Hopefully he will help you too.

It sounds like Will's story is similar to mine, but with much more complicated logistics! I wish him well.

I have attached two images showing the range of PPIs currently on my straight edge. At this point, what should I do to bring up the PPI count? Technique 40, or..... ? Also, regarding the percentage of contact, the use of a precision ground stone has been mentioned as a way to increase it. Would it have to be precision ground? I had thought about using a regular stone and checking my progress frequently to make sure I was on track. Wouldn't that work?

 

[Richard King]

Left one 12 with 10% - R one 8 with approx. 50%
You need to practice laying down lines at diagonal 45 degree lines of scrape marks from the side of the SE or part. You need to practice the checkerboard technique.
Will said he had issues until he bought my DVD /USB stick that he bought before the class. He uses a BIAX scraper and not a hand scraper. What I showed him on the first few days of the class that he didn't do right was to sharpen his blade to a 60mmR - 30 or 20 mm wide blade first to get 20 PPI, then a 40R- 3/4 or 20 mm wide blade to get 30 PPI and then a 20 R-5/8 or 15mm wide to get 40 PPI.

He also wasn't using a 1200 grit diamond lapping wheel, I think he used a 600 grit back home and I believe ( I am going to email him, so he reads your thread to tell you as I don't remember exactly) he only used a 60 R and he was getting corner scratches. Also start with a wide or 1 1/4, 25mm blade and as you get more points you use a narrower blade.


One thing that he did that I had a hard time getting him to stop was to dab or drop the blade straight down to scrape each high spot. I showed him how to move in a U in and out sideways which I call dive bombing and Biax calls Technique 40. The dive bomb is done on the diagonal line. Also I showed him how to measure the depth of the scrape mark. After I showed him to do the 8 pounds pressure down on the DR office scale. I believe his depth was .0004" deep. I also showed him to draw the square boxes on the SE to scrape them individually or scrape the first squares highest blue spots in each box before moving to the next box. One of his photo's shows this.

Another thing I showed him was to rub the SE for a count of 10 or approx. 20 times so the high spots change from the same color of the bluing when one only rubs back and forth 1 or 2 times. When you rub a number of time the highest spots get shiny like small mirrors, the next lower high spot shows up as black and lowest is the same color as the bluing.

The key is to scrape diagonal line from the start after you get 10 to 12 PPI after roughing. To improve on yours, you need to scrape the diagonal lines and the next diagonal line doesn't touch the first line and so on down the SE.

Garth one of the other student hand scraped most of the time and he also got a beautiful pattern. He had never scraped before the class and as they say it's easier to teach a new dog new tricks. Will, had some bad habits I had to correct I took several pictures and need to upload a few more here. On the other thread with pictures, 2nd group of pictures you can see Garth hand scraping his angle block the checkerboard technique.

I only use a ground on a surface grinder diamond wheel when I am scraping 30 to 40 PPI. I have 2 brands. One that Spencer Webb that will used and a Lance Beltzley makes

Will said when he goes home he was going to lap his stones on his lapping plates and diamond compound. A normal bench stone is not flat. I buy brand new MS-24 Norton tapered stones and they are not flat. Most are high in the middle .030". Take yur stone and lay it on a granite plate and hinge (pivot) it.

Once you master scraping diagonal lines and then stand at 90 degrees from the fist total 100% coverage, to get the checkerboard look, your scraping will improve.