Tip For Finish Scraping

[loply]

Hi folks,

I was scraping in an 18x12 iron surface plate tonight, and I thought I'd post a 'tip' which I've learned. Never read this anywhere else, but, I've certainly found it helps me obtain a consistent and even distribution of blue when in the finishing stages. I'm no expert but I have done a lot of scraping in the last 3 years or so.

This tip applies once I've got full bearing and I'm trying to get consistent distribution of the blue. I'll take a normal scraping pass and remove the blue as per usual, I then stone the part really quite heavily so that I'm actually flattening the part locally, then I'll rotate 90 degrees and mark out parallel lines with a pencil approx 1.5 inches apart, then I'll run a full scraping pass over the entire part. Obviously at this point no blue is present so I'm just scraping 'blind' per se, but I slow the Biax down and concentrate entirely on delivering a completely consistent pattern of marks over the whole part, making sure each scrape mark is evenly spaced from the preceding one.

I then stone it very lightly and blue up again.

I always find this results in a very nice and even pattern of bearing points, whereas without this 'blind pass' I find I'm sometimes just moving the blue around randomly and not getting it any more even.

Not only does it help with the blueing, it also helps achieve a pleasing aesthetic due to the entire part being covered in consistent marks.

Just thought I'd share.

Rich

 

[chevydyl]

How can you make this claim and not show a comparative slide of pictures.....

 

[TakeDeadAim]

Here is a tip for getting there another way without the risk of removing material blind and "digging a hole" with your stone. Unplug the biax and go to a hand scraper. They have much more feel and give a much nicer finish. You can literally pick the higher spots down a bit and distribute your bearing points out. When you get down close the thickness of your bluing layer on your marking plate can even effect your marking. I spread my bluing with a wood block, about 1.5" x 2.5" with a piece of suede glued to it. I was taught these techniques over 30 years ago by guys that had been doing it for 30 years.

 

[loply]

Always preferred the look of the Biax scraped surfaces myself, and it doesn't half make things quicker if you've got a big workpiece!

If you slow it right down, and use a very flexible blade, it gives plenty of feel

 

[4GSR]

I use the Biax for finish scraping. I don't see a problem with doing so as long as it is adjusted for the cut needed. As TDA said about using a block of wood with a piece of suede, I use a piece of leather, glued on. Works good for getting an even film of bluing or contrast yellow spread. Still have to take your palm of your hand and rung across to pick up any fuzz or fine grains of debris before taking impressions.