07-23-2012, 02:34 PM
(This post was last modified: 07-23-2012, 02:38 PM by Rickabilly.)
Hello All,
Recently in another thread here at MWF the question was raised, How to make a Flat Scraper out of an Old File, Having had quite a bit of experience in the field I posted the following and was subsequently asked if I would mind setting up a "How to thread" so here goes.
Best Regards
Rick
Hello All,
Please see attached sketches showing the process of converting an old file into a flat scraper.
The dimension "X" is the file/scraper length and while a bought scraper will have no teeth on the faces when I make one from a file I usually just dull the teeth off on a belt sander as the pattern actually makes it easier to control when oily.
The edges are necked in as can be seen in the second image on the scraper sketch as this allows scraping close to a stepped edge,
The front is radius-ed so that the corners never dig into the work piece,
The front 1/3rd of the tool is tapered to half of the original file thickness as this helps control-ability, if the front edge is too thick it is difficult to see the scraping in progress,
Grinding the cutting edge is critical there is no "bevel" but the edge is hollow ground on a 4"-6" ally oxide wheel, I do it by eye nowadays but was taught to use a jig as drawn, the scraper should point directly at the axis of the wheel which will give an edge that is just less than 90 degrees on both sides of the scraper, and it is best to leave the grinding marks as these aid in starting a "Scrape",
To finish sharpening the tool, lap the top and bottom faces either on a stone or diamond lap, do not use wet and dry paper as this blunts the edge, some people hold the scraper at 90 degrees to the stone and polish the hollow ground edge, but I find that this reduces tool life and grooves the stone badly which ends up rounding the edges badly which means a blunt scraper.
Recently in another thread here at MWF the question was raised, How to make a Flat Scraper out of an Old File, Having had quite a bit of experience in the field I posted the following and was subsequently asked if I would mind setting up a "How to thread" so here goes.
Best Regards
Rick
Hello All,
Please see attached sketches showing the process of converting an old file into a flat scraper.
The dimension "X" is the file/scraper length and while a bought scraper will have no teeth on the faces when I make one from a file I usually just dull the teeth off on a belt sander as the pattern actually makes it easier to control when oily.
The edges are necked in as can be seen in the second image on the scraper sketch as this allows scraping close to a stepped edge,
The front is radius-ed so that the corners never dig into the work piece,
The front 1/3rd of the tool is tapered to half of the original file thickness as this helps control-ability, if the front edge is too thick it is difficult to see the scraping in progress,
Grinding the cutting edge is critical there is no "bevel" but the edge is hollow ground on a 4"-6" ally oxide wheel, I do it by eye nowadays but was taught to use a jig as drawn, the scraper should point directly at the axis of the wheel which will give an edge that is just less than 90 degrees on both sides of the scraper, and it is best to leave the grinding marks as these aid in starting a "Scrape",
To finish sharpening the tool, lap the top and bottom faces either on a stone or diamond lap, do not use wet and dry paper as this blunts the edge, some people hold the scraper at 90 degrees to the stone and polish the hollow ground edge, but I find that this reduces tool life and grooves the stone badly which ends up rounding the edges badly which means a blunt scraper.
Whatever it is, do it today, Tomorrow may not be an option and regret outlasts fatigue.