My first shot at scraping

[TroyO]

I started with nothing but the very best of raw materials. : It's about the ugliest hunk of old window weight cast iron ever... LOL. But, it was of a decent size for what I wanted and it was exactly the right price. (Free) ;-)

So, I did my best at milling a hunk of something usable from it and it actually went OK. Then I cleaned it up on my $65 "Surface grinder"
:big: :big: :big: :big: :big:
http://www.harborfreight.com/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.html
:big: :big: :big: :big: :big:
Whatchya laughing at? If you puts a surface on it, it grinds it = surface grinder right?

Lessons learned so far....
1) You can "shovel" cast iron off fairly quick with longer strokes, but only do so until it starts to fill in.
2) I need a better surface grinder. :'(
3) Scraping makes your arms hurt
4) It gets hard to see the ink at the end.... when it's thin my old eyes have trouble picking up the inked spots. Suggestions? I did just get some canode red and blue spotting stuff from Ebay, maybe that will help. (I can't vouch for the product as I have not tried it yet... but they definitley shipped fast. http://www.ebay.com/itm/Canode-Die-...218?pt=LH_DefaultDomain_0&hash=item1c245be022 )

Now I get to flatten 2 more sides... and endeavor to make them actually 90^ and 45^ angles respectively.

Wish me luck!

 

[steamer]

Lessons learned so far....
1) You can "shovel" cast iron off fairly quick with longer strokes, but only do so until it starts to fill in.
2) I need a better surface grinder. :'(
3) Scraping makes your arms hurt
4) It gets hard to see the ink at the end.... when it's thin my old eyes have trouble picking up the inked spots. Suggestions? I did just get some canode red and blue spotting stuff from Ebay, maybe that will help. (I can't vouch for the product as I have not tried it yet... but they definitley shipped fast. http://www.ebay.com/itm/Canode-Die-...218?pt=LH_DefaultDomain_0&hash=item1c245be022 )


1 YES! That's called rough scraping and once it's basically touching in all area's it's refered to as "carried"
You should shorten your strokes then and only go after the actual points
See my recent aquisition in my SB9 thread for an example of how the bearing progresses and finially carries.

2. Not necessarily,,,,get stronger! ;D
3. See 2 above
4. Use low angle light that will help. Sometimes its better to use a shadow plate to cast a bit of shadow to reduce the glare

I only use the red, but you could try co-marking with red and blue....haven't tried that yet.

The Canode I use are from "E S Dyjak" and the bottles are bigger.

http://www.manta.com/c/mm7hwmg/e-s-dyjak-co-inc

Keep at it bud! you'll get there...it's all in the doing!

After each cycle, cross your cycle. That means approuch from 90 degrees from the last cycle. It will keep it from chattering. If it seems the pattern keeps moving a lot between cycles...it's probably flatter than you think it is...and your scraping far too aggressively. Shorten up on the stroke and refine it. The pattern should start to stabilize.

Your lucky! its is bearing on the ends and not he middle. It gets tricky the other way around.

Dave

 

[TroyO]

I have some scratches still left from over-exuberent use of technique 1) but it's actually pretty darn close. That last pic was several rounds ago but it's the last one where the camera picked up the ink at all.

I do think I want a few more passes at it. I switched up from my big scraper to one of the smaller file sized ones which seems to have helped for that last few bits.

Big smiley moment:
"Huh? It's sticking to the surface plate.... did I use too much ink? Ohhhhhhh.... it's actually suctioned to the surface plate...... because it's so damn flat. Booyah!

Quote:
2. Not necessarily,,,,get stronger!

You remind me of Miyagi from Karate kid... "Advice? Move faster, get hit less often."

I looked up ES Dyjak but couldn't find them on the interwebs. Being a child of the information age and an IT guy I have a rule... if they can't be bothered to open a website I can't be bothered to buy from them. ;-) (OK, not entirely true but they would have to save me a buttload.)

 

[steamer]

Hey Troy

Dyjak has a nice product....but it's a niche market....I just go with what works for me.
They came highly recommended by a couple of scrapershands I know that's all.

If what your using is working.....use it.

Mess around with the low angle bright light and the shadow plate...it does work.

Dave

 

[steamer]

And stone the edge of the scraper to as close to a mirror finish if you can.
It will cut easier and leave a nicer finish on the part

When looking at the mark up now. Look for the actual bearing point. It will look like a bullseyes of silver with a ring of canode around it. Now just cut the bullseye.

Also try a bit large radius on the blade to soften up the bearing a bit. It appears your using either a narrow blade or a small radius tip at the moment.
Either has it's place.
Experiment and you will see what I mean.

You know if it sucks down to the plate with a very thin mark up your real close!

You will get so you can "feel" the difference during the rub of how the bearing has improved from the last cycle.

Now once it's "flat" lay the part down on a clean plate. push the part from 1 end. The part should rotate and it should have a center of rotation about 1/3 the way in from the other side.

Now push the other side. The center of rotation should again be 1/3 the way in from the other side.

That would be the "spin" test.....that would indicative of flat surface

NOW Stone a piece of .001 feeler gage to a angled feather edge. Poke the part easily all around the sides and see if you can get the gage under the part......The result here is obvious.

NOW take three pieces of smoking paper.......I use "ZIG ZAG" ;D.....No really! ;D

put 1 piece at each end and 1 in the middle. Gently tug on the paper so that they move and pay attention to the level of tension to move them....they should be all the same. If it passes this test and the feeler gage test and the spin test.....it's as flat as your plate. Each test confirms the other 2.

Dave

 

[TroyO]

I am anxious to try that canode stuff... if nothing else the water clean up will be nice. (Not to mention being less likely to cause my wife to kill me if I get it on my clothes....)

I too noticed it seemed like the width of the cut was narrower than expected. The radius is pretty big, but there's plenty of meat on the carbide to shallow it out. I'll give it a regrind/lap and see what happens.

Also, I have actually been sharpening at 90 instead of the more common referenced 93 degrees... could that maybe be it? I figured that angle was more about getting good cutting action... but in hindsight it seems like it would make you hold the scraper "flatter" to the part and bring a wider swath to bear? Hmmmm....

I guess this where the learning begins, LOL..... I have about an inch thickness of cast iron there, hopefully I can figure it out before I come out through the backside. ;-P
(Although.... I have more window weights so even that won't stop me. ;-)

I have seen the bullyeye effect.... that was my next step was to try and pick those islands off.

BTW, spin test/rolling paper trick both are gold! Wouldn't have thought of it!

 

[steamer]

"...BTW, spin test/rolling paper trick both are gold! Wouldn't have thought of ...."


Oh not my concepts! Some REAL scraper figured that one out long before I was born! :big:


But they work!

 

[steamer]

Troy

5-7 degree negative rake is about right for a scraper blade. From the flat side of the blade it would be 82-85 degrees. And yes you end up with a crown down the center of the blade .....that's the right way

Positive rake may explain the scratches ....

Negative rake lets you grind both sides so you always have a sharp edge.

Dave

 

[TroyO]

Angles always confuse me... I never seem to get what the angle is in relation to. Just to make sure I'm not being dense, I attached a CoC... I want the top one, right?

 

[steamer]

The top one is correct sir!

Dave

 

[steamer]

Troy

I would rough machine the angles in before I went much farther with the scraping.

The part will probably distort from all the metal removal which will defeat your scraping effort.

Ask me how I know this! :wall:

;D
Dave

 

[TroyO]

It already is... within .010 anyway. I also cycled it through several passes in my oven up to 600F and back to room temp too. (Not sure that helped a darn thing.... except maybe that the veg oil I wiped on got baked on to an awesome no-rust coating, LOL.)

 

[steamer]

How ya making out Troy?

Dave

 

[TroyO]

Nothing much of late. I am in Portland with my in-laws for a while. I will post back when I get another go at it.