scraping diagnosis

Luke Rickert

Hot Rolled

Joined

Oct 24, 2007

Location

OSLO

• Mar 6, 2017

• #1

Hi this is part of drill press vise project but also closely resembles a 2 by 3 inch rectangle of cast iron. I am finding that I end up with sparsely spaced high points. Any suggestions? Do I need a different radius on the scraper, better separation between each scrape or something else to try. The current radius is around 50mm maybe a bit tighter towards the edges.

thanks

luke

 

I

inwoodcutter

Cast Iron

Joined

Mar 10, 2005

Location

Tell City, Indiana

• Mar 6, 2017

• #2

You have it close to flat. Now you need to scrape for bearing. At this point you should only be scraping the high points. Just the blue. The other marks on the block indicate that your scraper is not taking too wide of a swath. You just need short strokes right at the blue. After a few cycles it should come in.

 

M

MCritchley

Stainless

Joined

Mar 22, 2007

Location

Brooklyn WI

• Mar 6, 2017

• #3

+1 on the above post. Try for a 5 mm stroke or so. Are you using a stone after your scraping cycle?

 

Luke Rickert

Hot Rolled

Joined

Oct 24, 2007

Location

OSLO

• Mar 6, 2017

• #4

I will try for a shorter stroke. I am using a stone but it might be getting a bit loaded up, I will give it a cleaning.

thanks for the tips.

L

 

P

Peter.

Titanium

Joined

Mar 28, 2007

Location

England UK

• Mar 6, 2017

• #5

Looks like you're over-scraping a bit each turn. Don't put two scrapes alongside each other, leave a gap between scrapes as wide as the scrape itself. Do this no matter what.

 

Luke Rickert

Hot Rolled

Joined

Oct 24, 2007

Location

OSLO

• Mar 7, 2017

• #6

I made made some progress thanks to your tips, also making sure the cuts are sufficiently deep.
I then decided to take on something that would provide more practice and more area away from edges and started on a big chunk of iron which will be a surface plate once it is done. It is a bit tricky to pick up and spot and rather difficult to get it off again as it kind of sticks to the granite and is smooth and heavy.





L

 

P

Paolo_MD

Stainless

Joined

Apr 6, 2013

Location

Damascus, MD

• Mar 7, 2017

• #7

whidbey said:

I will try for a shorter stroke. I am using a stone but it might be getting a bit loaded up, I will give it a cleaning.

thanks for the tips.

L

Click to expand...

I know that somebody would disagree, but I find very handy using a small whetstone, whine using Canode or other water-based products: the stone doesn't get loaded up and you stone the part by gliding the stone on a water film, removing only the burs.
Make sure you dry all the water before the next spotting cycle, especially if you have to turn the part upside-down.

Paolo

 

Luke Rickert

Hot Rolled

Joined

Oct 24, 2007

Location

OSLO

• Mar 7, 2017

• #8

I am using the old fashion (never-comes-off) variety of bluing which I think goes with white spirits better. With glass cleaner the stone (soft Arkansas) seems not to cut at all but with spirits it works nicely. I will probably move to the water based marking compounds at the class in April.
L

 

P

Paolo_MD

Stainless

Joined

Apr 6, 2013

Location

Damascus, MD

• Mar 7, 2017

• #9

Luke,
Just remember the stone is supposed to remove just the burs. Very light cutting is more desirable than heavy cutting.
With the risk of oversimplify things, for media and solvents, I'd stick with a "system of kins": water with water-based stuff, oil, hydrocarbons with oily stuff.
Mixing water with oil you end up with mayonnaise (=some sort of sluggish emulsion). Soaps can break-down oily stuff, but it's not optimal and you risk to accumulate deposits.

Paolo

 

C

capocoreyollo

Aluminum

Joined

Jul 22, 2015

• Mar 7, 2017

• #10

You can also use a surface ground, hardened steel block or a worn/ground file to cut the burrs off, though this cuts very minimal. I use a steel block, usually end up with a lot of points but with little contact area. After that, you can give it a good stoning to bring in more contact area at the sacrifice of the amount of points ( trick I learned from Richard, kinda "cheating" but it works lol) . Iv'e had pretty good results and you save your stone while roughing as you only need it when your getting close to done.

Corey

 

P

Peter.

Titanium

Joined

Mar 28, 2007

Location

England UK

• Mar 7, 2017

• #11

I tend to stone quite heavily when I'm roughing but only lightly when finishing.

 

JST

Diamond

Joined

Jun 16, 2001

Location

St Louis

• Mar 7, 2017

• #12

Are you changing over to "point splitting" when you get spotting fairly even all over? And moving from possibly 1/2" or 3/8" at the start to shorter as things progress?

In the first of your last two pics, you show somewhat uneven coverage, AND a number of "bull's-eyes" which are rings of dark around a high point that has squeezed out the blue. For those, splitting them with the scraper right across the light central area will bring them down and let the bearing come up more even.

In pic 2, you have a lot of small points well separated. Most of them seem to be bull;s eyes also. I would begin by splitting them all ( the bull's eyes only) with short strokes, and keep up with that until the points become much more numerous and probably somewhat larger.

probably some of the tiny spots will get larger and become bull's eyes as you do this.