The new scraping thread

[Greg Q]

After getting distracted from something else on the spindle video thread I thought I'd start a new thread here. Some photos below of a triplet of scrapers. Top is a Sandvik Coromant carbide scraper sporting a replacement handle made from a pad saw. Below it a file-sized piece of CRS with a carbide tip brazed on-I bought it from Forrest Addy when I took the scraping class in Seattle a couple of years ago. The bottom one is made from an alloy handled screwdriver I bought at a flea market. a 12mm carbide tip is brazed on and rounded to a small radius for very fine work.

The Biax power scraper can be seen dangling from its tool balancer which I find a must for prolonged sessions.

The granite plate with a couple of drops of red dye spread with a printer's brayer. Its important to be able to see the pattern through the dye. This much will last a couple of hours of constant spotting.

I bought the red dye from Forrest too.

The tools are resting on the cast iron plate I'm scraping. You can see the pattern left after the last scraping cycle. I stoned off the surface with a diamond stone using a very heavy hand-much more than used when you approach a flat condition. This piece is still very hollow in the middle which you'd expect after years of use in a shop. (And moving with age)

Greg

[Greg Q]

The missing photo

[Stustoys]

Greg,
Is your granite pink or black? Do you cover it with something between spottings to keep dust off?

Stuart

[RayG]

Duplicating the post in the other thread, but gently moving the discussion towards the scraping thread..

Dyken layout fluid isn't suitable as it's not designed to transfer from one surface to another. I haven't done much scraping, but use bearing blue and found it easy to obtain from a local engineering supplier.

Pete

Hi Pete,

No, not the layout blue, it's the stuff in a tube.


I think Greg's stuff sounds cleaner.. .. is water soluble is good

Regards
Ray
PS I should have replied in the scraping thread... which I will now do..

[Pete F]

Yes that's what I use Ray, just another brand (Holts). But Greg's brew sounds much better. While I spread the blue with a little rubber roller, the name of which eludes me at present (brayer??), I clean my plate with the heal of my hand (I have no idea if this technique is "correct", just what I do). It's crap stuff to get off, so I typically then wander off to work looking like I'm turning into a smurf!! Suffering through washing a load of dishes would be worth the pain if that's all it took to remove it.

Pete

[Greg Q]

That Hi-Spot is the right stuff. Clean-up the only issue. Do you recall how much it cost Ray?

Stuart, my granite plate is neither-it's kind of a beige/white granite from the old Czechoslovakia. I bought it from a Gray's auction where all the machines looked showroom, including a beautiful Hardinge that fetched $35,000+. The plate surveys out ok, but it does have quite a few little pits. The nice thing about granite is that lost material doesn't come with a raised crater lip like iron does.

I have come to the reluctant conclusion that when it comes to granite plates of any size you are better off (but poorer) to buy new.

And before I forget, I don't cover the plate between scraping spotting cycles but I do check with my palm and roll it out again with the brayer. I found that as long as you keep the plate a few steps from the scraping area it doesn't get contaminated too much.

Plate contamination leads to confusing and false readings, but particles show up as little ink coloured orbits*. I'll post a picture of a deliberate one maybe tomorrow if I get time.

*because I put the work on the plate and move it in little circles to transfer the ink. Others go back and forth or figure eights. Whatever motion is comfy is best according to Richard King who is another scraping tutor.

GQ

[Greg Q]

Yes that's what I use Ray, just another brand (Holts). But Greg's brew sounds much better. While I spread the blue with a little rubber roller, the name of which eludes me at present (brayer??), I clean my plate with the heal of my hand (I have no idea if this technique is "correct", just what I do). It's crap stuff to get off, so I typically then wander off to work looking like I'm turning into a smurf!! Suffering through washing a load of dishes would be worth the pain if that's all it took to remove it.

Pete

I used to wonder if that's what bank robbers look like after the dye pack blows off in the bag of loot. Caught blue-handed.

Brayer is correct

[Pete F]

Brayer is correct

Oh yes. I thought it was something spelt remarkably similar to what I'm normally doing when I'm machining!

[RayG]

Hi GQ,

It's in the latest order I've got coming from victornet.com $5.95

Dykem layout fluids - Blue and red layout fluids for machine shop layout, and Dykem steel markers.

I tacked it onto an order for 01 tool steel, so it will be interesting to see if it actually gets here. (their web site says not for export )

In any event, I like the sound of your stuff better, nice colour too.

Replying to Dave's comment in the other thread,

Hi Ray,
This is a quote from the link below
"The typical precision of a surface grinder depends on the type and usage, however +/- 0.002 mm (+/- 0.0001") should be achievable on most surface grinders."
Surface grinding - Wikipedia, the free encyclopedia
Scraping as Greg said can get down to 0.00005 inch
Scraped ways are also said to be superior over ground because they have less stiction, but I have found as long as one surface is scraped this hasn't been a problem.

I doubt I'm getting down to 0.002mm accuracy, I can't measure down past 0.005mm as it is, but you've answered the question, scraping is significantly more accurate. But you raise another question (stiction) , ways are often patterned (I believe to help retain oil) how does this affect the accuracy? Do you deliberately create some kind of pattern when scraping?

Regards
Ray

[Greg Q]

Ah yes, the power of prayer. I remember as a kid I prayed for a new bike but didn't get it. The parish priest told me God didn't work that way. So I stole the bike, then prayed for forgiveness.

[Stustoys]

Greg,
So the spotting fluid covers well then.
I'm not sure I want to know the answer to this but here goes. Have you seen the price of a large name brand plate?

Stuart

[Greg Q]

Hi GQ,

It's in the latest order I've got coming from victornet.com $5.95

Dykem layout fluids - Blue and red layout fluids for machine shop layout, and Dykem steel markers.

I tacked it onto an order for 01 tool steel, so it will be interesting to see if it actually gets here. (their web site says not for export )

In any event, I like the sound of your stuff better, nice colour too.

Replying to Dave's comment in the other thread,


I doubt I'm getting down to 0.002mm accuracy, I can't measure down past 0.005mm as it is, but you've answered the question, scraping is significantly more accurate. But you raise another question (stiction) , ways are often patterned (I believe to help retain oil) how does this affect the accuracy? Do you deliberately create some kind of pattern when scraping?

Regards
Ray

Yeah, you see a lot of that flaking for oil retention on ways, most of it wrong according to my tutors. The thinking goes that flaking or pocketing belongs on the hidden way, but the exposed part should be scraped only because of dirt sticking in the recesses. The idea is to scrape to as many spots per square inch so that after the flaking there is still sufficient bearing. The highest quality bearing is one that has a balance of high spots with deeper areas for oil retention anyway.

Flaking is done in half moon patterns that link so that the oil can be spread evenly over the sliding surfaces and take a serpentine path out.

I want to buy or borrow a Biax 10ELM half moon scraper for flaking because the only attempts at it that I have made have been crap. I guess its an acquired skill

[Greg Q]

Greg,
So the spotting fluid covers well then.
I'm not sure I want to know the answer to this but here goes. Have you seen the price of a large name brand plate?

Stuart

Yup. Gutting. I am waiting on a quote from a car importer on the price to ship in two or three plates from the states.

[Pete F]

Hey Greg, here's a question without notice. Do you think flaking is advantageous if the surfaces are already scraped (versus ground). Personally I think flaking is a bit of wank anyway, but a) would I know b) it looks cool ... well if it's done correctly. My attempts are pathetic. I mean TRULY pathetic

I wouldn't think it would really have any benefits on a scraped surface in terms of oil retention. Thought?

Pete

[Greg Q]

I don't know...a lot of what was done decades ago was based on a less than perfect understanding of the physical world at the microscopic scale. I think two scraped surfaces have plenty of scope for oil retention, but the flaking may aid in distribution. You know how one way will have a little furrow in it for to allow oil to wick from the oiler across a larger area? I reckon the flaking is supposed to pick up oil from that and spread it laterally across the way.

I'll have to draw it out later.

I don't think that I have ever seen flaking on a Deckel mill. I'd be interested to know what's under Bob's Schaublin ways. The Perrin has no evidence of flaking either.

Apart from that there is the other area that Bob asked about: the decorative effects. That's an area that interests me very much, but there's not much info on it. My early attempts at that have been crude but not disheartening.