Scraping a v-way without a relief groove

The only way to scrape all the way into that dovetail is to cut a relief groove into the corner. The thickness of a scraper blade will not allow it to cut all the way into the corner. We used to cut them in with an abrasive cut off wheel in an air grinder. That groove and putting a small flat on the end of the mating surface will allow you to not have to scrape the dovetails all the way in. You must be careful when printing the two parts together that they are not riding on any area in the corner of that dovetail. I can make some sketches for you if my explanation is not clear. This can be done, ive done it dozens of times and if done carefully it will not weaken the part and it will allow you to restore the accuracy of the saw.
 
The only way to scrape all the way into that dovetail is to cut a relief groove into the corner. The thickness of a scraper blade will not allow it to cut all the way into the corner. We used to cut them in with an abrasive cut off wheel in an air grinder. That groove and putting a small flat on the end of the mating surface will allow you to not have to scrape the dovetails all the way in. You must be careful when printing the two parts together that they are not riding on any area in the corner of that dovetail. I can make some sketches for you if my explanation is not clear. This can be done, ive done it dozens of times and if done carefully it will not weaken the part and it will allow you to restore the accuracy of the saw.
Exactly what I wanted to know. Is there a minimum thickness for a 1/4” wide scraper blade that you have used? Relates to the thickness of the relief grove. Thanks again for the concise reply
 
Flightmap, The narrowest scraper I have is 20mm and it takes a Sandvik blade that is about 3/32" thick. We used to use .080" cut off wheels and then widen the groove to meet the needs of the part. There are many more wheels available now with the increase in applications and tools that take them. You just need to make a slot that is wide and deep enough to allow your scraper blade to cut all the way to the edge the dovetail surfaces. I found that cutting the groove then taking 2-3 cuts, (90 degrees from each other) along that back edge to ensure it is lower than the rest of the surface; then scraping the surface to bring that back edge back into bearing gave me a confidence that I had no interference from the back corner.

If there is a gib on one side make sure it is only touching on the flat and not the corner. It will bind and not have good motion if there is bind. My teacher taught us to take all the gib corners out of play to ensure this and I think based off how your saw works I'd want to do it in this application.

Let me know if I can be of further help
 
Interesting. I thought that a spotting tool (hence the 1/4” wide stated above) would have been the choice. So 20mm +- wide, about 3/32” high would be your suggestion. I’ll try it (on a scrap dovetail) for practice before I work on the saw dovetail. Sounds like the relief grove would be about 1/8” wide and 1/8” deep. Will also check this against the saw dovetail for available material. The groove might compromise the dovetail. If I went with a 1/16” scraper blade would the edge be too fragil for carbide? Maybe use HSS for that thickness? Thinking of a smaller relief groove. I really appreciate the comments and suggestions. Don’t want to be too anal, but I wouldn’t want to damage the saw (or any other machined part) as I think it is probably pretty rare.
 
20mm is a spotting tool; I know Richard may disagree and thats fine. I was taught by a different group of people in the late 70's and early 80's in Milwaukee. A standard tool was a 30mm wide blade, 20's were spotting. Width of cut is really more a product of the radius on the blade rather than width. How hard you push down and how you put it down and pick it up when taking a cut effects width and shape of your scraping cut. Ive got a half dozen or so of blades that are profiled a little different from each other, they cut different materials and either a wide or narrow cut. in all my scraping the tool is pushed with the hip, not the hands/arms; So I also have (somewhere) a box of wooden handles of different lengths that allow for reaching the area that needs cutting. We had stacks of wood platforms to stand on to get the proper height. We were taught to cut a "comma" shape and strings of those together was how we did what some people call flaking. No power scrapers at all.

I have my 20 mm at the bench here and the blades measure 2.15mm or .085" thick. Im sure this is not the only way to scrape, I know all the guys that taught me and the other apprentices were all in the Navy and all, at one time or another worked at the same place. All I can speak to is how I was taught and what worked for me. If you do it the way I describe I know it will work. Again Im more than happy to give any guidance I can.
 
Sorry hit enter too soon, I think using a narrower thinner carbide would be fine. Id want to get a bit of practice with it and make sure you round the corners a bit, the narrower the blade the easier you can catch a corner and dig a groove. I dont think a relief grove will weaken the part appreciably so long as your careful and only go as wide and deep as needed. I can recall having to re- cut a few when I did not go large enough. Like all metal work its much easier to take small cuts than it is to try and put some back on.
 
How about a bow saw and use a bandsaw blade, drill it to fit the saw and cut away, wont take long.
 
Yes. Using a bow saw is discussed in Connlley’s book (noted above by Frank). My question is IF there is no relief cut at the back of the dovetail, how do you scrape it? Stephen Gottswinter showed a dove tail he scraped that was lik this. He didn’t show a close up of the the interior of the dovetail, or explain the scraping tool he used. I’m sure there is a way to scrape into a an oblique angle, I would like to know the design and shape of the tool, and the design and shape of the edge.
 
We were taught to cut a "comma" shape and strings of those together was how we did what some people call flaking. No power scrapers at all.
That sounds like the Moore scraping method,
Here is Robin Renzetti using that method for precision work:
Relevant part starts at 36:00, but the entire video is interesting...
The Moore Special Tool Company used that style of scraping on the machines and tooling they made.
Moore, Wayne R. (1970). Foundations of Mechanical Accuracy. Bridgeport, Connecticut, USA: Moore Tool Company. ISBN 0262130807. LCCN 73127307.
 
I tried to help you in the first few posts and you didn't seem to want to listen. So I stopped trying to help you. I am known around the world as an expert scraper and Tom Lipton and Stefan G are students of mine. They needed their techniques tweeked. I sell the Connelly book and the bottom relief groove is a simple part of scraping. No need to be a rocket scientist to put it in. Some companies cut them in with a shaper, planer, cut off saw, hack saw, air grinder with burr or thin disk, a Dremel, a sharp edged carbide or HSS scraper blade, a knife file, etc. Some factories don't relieve with a groove. It helps when you scraping the dovetail with a prism straight-edge. Many only file the edge off the riding part and never relieve it.

As you scrape a flat surface the dovetails move over and you either cut it deeper, file off the mating side or apply a wear-strip. I have a scraping class next month, come and learn how from a professional machine rebuilder who has been training people how to over my 50+ years of scraping. If you go back to You Tube and search "Richard King Scraping" You can see several shows about me and my classes. Other notable students on You Tube are Adam Booth, Keith Rucker, John Saunders, Jan Sverre Haugjord. I have taught classes at Timken, dozens of new machine builders, 7 divisions of GM, USA Naval shipyards and army depots, hundred of places and thousands of students. You can see more at my website.
http://handscraping.com/ and under testimonials You will see this.

"Ever since you instructed our first group of rebuilders, we have had numerous requests to have you back to instruct the remaining rebuilders. Your ability to adjust your class to fit our needs left a lasting impression.

Even though our rebuilders are experienced at scraping, they learned new techniques to improve accuracy and efficiency. The rebuilders had a lot of praise regarding the class and recognized your expertise as you worked along side them.

I strongly recommend King Way ... seminar for instruction in Basic 40/40 Hand and Advanced Machine scraping. It is excellent for anyone who is doing machine rebuilding or slide retrofitting."

Norm J.
Supervisor Machine Rebuild • TIMKEN • Canton, OH 44706

I am willing to help you here if you want to learn.
 
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