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gr8life
05-09-2008, 12:43 AM
Guess I opened a can of worms with the bent file question. Just to put my question straight, I am not having trouble with the finish, just curious about the bend. As a side note I use a file card every few strokes and have a large caliber rifle shell hammered flat in a handle to really clean the files. Works great really gets to the bottom of the grooves.
Now on to my next question. Scraping. When I did a lot of woodwork I used a cabinet scraper on fine work. Is a metal scraper used in the same way?
ed
If this is going to open another can of worms I am sorry.

Bob G
05-09-2008, 01:22 AM
Hi gr8life, You donít open a can of worms by asking a question on this BB. The can of worms is opened when information is posted that has no basis in fact. I don't know anything about "Scraping" and I will not post any BS about it. But there are a few that will post like we are idiots and they are here to enlighten us.
Have Fun
Bob G

Patch
05-09-2008, 01:44 AM
gr8life,

no can of worms here, it's all a good read.
Forest Addy is the guy you may want to speak to on scraping. He has put forth a few classes in that area.

all the best,

Patch

Mcgyver
05-09-2008, 08:13 AM
gr8,

first off you must be going crazy cleaning those files out every few strokes. Get yourself some kids sidewalk chalk, comes in like 1" dia sizes and 'chalk' the file. This really really helps in preventing the lits bits of metal getting jammed, and wrecking the finish. It might be that your using too fine a file to take off too much, but i bet the chalk will improve things.

metal scraping is nothing like cabinet scraping. Metal scraping involves is a very localized removal of metal, basically 'blue' (kind of like oil paint that doesn't dry) is placed on a known 'master', say a surface plate and the work is brought into contact. the high spots become blue and these 'scraped' away....repeat and after enough iterations, the work becomes as flat as the surface plate. So its a precision (tedious) process unlike wood scraping which is mostly for aesthetic purposes (and which imo is the correct way to finish a piece of wood) although the scraped finish has its aesthetic admirers! Newcomers are often surprised at how baby bottom smooth the feel is yet the look is so rough, each scrape is at slightly different angle so the reflected light makes the surface look anything but smooth

this is by no means best of class, but gives an idea.

http://i20.photobucket.com/albums/b201/michael0100/scraping/scrapedadjustableangleplate.jpg

Search here, lots on it.

I posted a lot more pics of basic scraping tackle here:

http://www.cnczone.com/forums/showthread.php?t=11874&highlight=scraping&page=3

actually, there's a fair bit in that thread if you're looking for an intro to it

JCHannum
05-09-2008, 08:35 AM
Scraping is a different operation with a different purpose. If a smooth surface is the desire, burnishing would be a suggestion. It involves dressing the surface with a highly polished, hard steel tool under pressure to create a smooth finish.

Carld
05-09-2008, 10:44 AM
I just made a post in the other thread that I tested my files and found them to be flat for all practical purposes. I have never had an issue with a file having a bow. I would suspect you just got a bad file. Throw it away or mark it for filing on round work only.

I have used many files over the years to dress a flat surface. It's just to get high spots off and not make it a perfect flat surface. If all your doing is taking off high spots and it don't have to be perfect a lathe file works real good for doing that.

I have found that some lathe files have one side concave and the other side is convex from side to side. This works to my advantage because the side that is concave cuts on the edges and removes metal faster and the side that is convex gives a smoother finish. If I am filing a bearing fit to a shoulder I have to carefully use the concave side so the edge of the file cuts all the way to the shoulder. The concave/convex of the file is not real great and sometimes only visible after some wear shows on the file surface.

Filing is a learned skill and not something that just happens. You have to learn to use a file to your advantage. Sometimes I wish I could go back to the early 1900's and learn some of the bench work methods of the old masters, it's mostly a lost art now.

Frank Ford
05-09-2008, 10:58 AM
In my field of guitar repair, there are some who insist on leveling frets with files. Those folks are know to turn up at hardware stores with straightedges to check files before buying them, and they often do a lot of checking.

It's not a new issue as far as I know.

Carld
05-09-2008, 11:15 AM
None of my files were perfectly flat Frank but some did have low and high spots but none of them were bowed from end to end. I don't doubt it happens but I think it's not a common thing and may be an oversight of the inspection dept if there is one.