sharpening a machinist scraper, help needed

[ali27]

Guys a while ago I bought a carbide tipped machinest scraper. I tried sharpening it, but never got it right.
I dont't understand how to sharpen it. I read some posts about it.

The posts say to sharpen at 95 degrees and apply a small negative rake. I just don't understand what
they mean. I think I just don't understand how a scraper works. Could somebody help explain it to me?

I have two steel honing plates on which I can apply diamond paste.

Thanks in advance.

 

[Wildman]

I find a light touch of the broad bottom face on a linisher works for me and did so all of my years engineering.

 

[heimlaga]

If you look closely at the "square" end of the scraper there is actually a tiny ridge along the middle. The end is also a little bit cambered.

When sharpening thgis style you use a fine diamond hone and sharpen with strokes going away from the outer corners (cutting edges) towards the tiny ridge in the middle. Do this from all four sides. The angle between the tiny bevels thus created and the side of the scraper is the actual bevel angle and should be somewhere around 95 degrees.

If you search for "scraping cast iron" on youtube you will find several instructive videos of the process.

Hope this helps.

 

[woodfarmer]

The straight sc rapers I made when I used them for straightening things such as lathe beds were shaped like this.

Start with straight file and gring off the serrations each side for teh last 2-3 inches before the business end.
do this so both surfaces have a -VERY- slight taper towards the business end.
now grind the end edge straight across at 90 degrees to the main body of the file.
because of the slight taper the actual angle will be slightly more than 90 degrees.

This is used with a circular poshing action.

hope that helps

after shaping, the scraper would be hardened.

 

[GLFaria]

http://www.antiquetools.com/scrape/

G.

Edit: in the following thread is a discussion on carbide tipped scraper sharpening

http://www.practicalmachinist.com/vb/ge ... ndex4.html

 

[ali27]

Thanks for the answers guys, but still don't understand it precisely.

Is this correct?

thanks