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loply
01-13-2013, 02:30 PM
Hi folks,

Been scraping away for some months now on various things and I finally got around to making a 'proper' scraper sharpening setup with a diamond cup wheel and a cast iron lap w/ diamond paste impregnated.

I had read that lapping with diamond paste was highly adviseable and the results are not disappointing. Compared to before where I had to really push the scraper in to the work to raise dust, now I can literally lay the scraper down under it's own weight and slide it forward and a small patch of dust will appear. It really is a lot more effortless and somehow results in a more predictable cut too.

I planned some fancy adjustable metal tables which could be rotated this way or that, but decided to mock up using some lumps of timber just to get a feel for things, but it works so well I don't think it's worth the effort of making anything better.

If anybody else is in a similar situation I recommend you take the time to make something like this, my scraping will go a lot faster from now on.

You might be able to see in the images I've got two of the Sandvik carbide blade things with radii of 50mm, 85mm, 110mm and 150mm, the blocks of wood are at 5 degrees. The diamond wheel runs such that it hits the 'cutting side' of the blade first so it doesn't splinter the edge (like how you'd sharpen a knife), whereas the lap is the opposite so the blade doesn't dig in.

http://www.vanmildert.net/vm/rich/scraper1.JPG


http://www.vanmildert.net/vm/rich/scraper2.JPG

Cheers,
Rich

duckman
01-13-2013, 04:29 PM
Where did you get the Sandvik gold the last ones that I bought were $70.00 each for the 1 1/4" , but I have enough to last me 2 life times. What is with the lapping of a diamond ground edge I've only been scraping for 40+ years and have never lapped an edge or seen it done.

loply
01-13-2013, 06:07 PM
The Sandvik blades I just found on Google and ordered somewhere, they were 30 each I think, I guess about $40-$50, they are 1".

To be fair the lapping probably isn't necessary if I had a finer grade of diamond wheel, the diamond wheel is 600 grit and leaves quite visible marks, the lapping brings it to a much smoother edge.

Forrest Addy
01-13-2013, 08:59 PM
Yup. Works good. I made many similar over the years. Your photos show haw simple and basic a scraper sharpening station can be and your remarks are spot on. A carbide scraper's cutting edge lasts for about an hour in vigorous use then it has to be touched up. If your support blocks are set at the correct angle it takes about a minute to re-lap the cutting edge then you're back in business. I use the bonded diamond whbeel onl;y for correcting the end radius or for re-shaping a scraper tip a different radius.

A scraper whose faces are mirror lapped and intersect at a 95 degree angle is a scraping dream. The same cutting edge an hour later forces you to work for evey chip. I can't imagine the effort required to scrape with an edge with days or wrrks since its last touch up.

Here's a version we used for a 2007 scraping class

http://prowave.blogspot.com/2007/05/scraping-class.html Goes to show that expensive precision made equipment is not always necessary.

Odd isn't it. Crude seeming tools skillfully applied and working methodically can produce sub-micron/micro-inch size-holding, geometry, and alignments. The people in this class were scraping their work pieces parallel to 0.000050" within hours of first picking up a scraper.

For the record I use cast iron for the lap but most any metal and many rigid platics will do. I've experimented and determined my onw uses are best errved with 9-12 micron diamond lapping compound in an oil base. Usually this grade is green. It doesn't really matter the concenbtration. The carat weight consumption cost averages over time .

PS Fixed the link

lakeside53
01-13-2013, 09:43 PM
Hey Forrest - check your link!


I was at the Newport scraping class.. We sharpend, scraped, then lapped the scrapers, and.. heck, it was like night and day!

Forrest Addy
01-13-2013, 11:20 PM
Hey Forrest - check your link!


I was at the Newport scraping class.. We sharpend, scraped, then lapped the scrapers, and.. heck, it was like night and day!

Fixed it