Mr. Inquisitive would like to know . . . How to sharpen HS and carbide scraper blades

[Mr. Inquisitive]

I picked up a couple of Anderson solid shank scrapers (non-round-type) at a local flea market. One appears to have a HSS insert and the other is carbide. I also have a full complement of bench grinder, oil stones, and DMT plates for sharpening purposes, but what is the recommended procedure for sharpening these tools? I've heard that the green grinder stones tend to chip carbide. How much camber, or curve, do you give the edge, what angle should the edge come to, and what grit do you finish with? Thanks in advance,
Mr. Inquisitive

 

[DMS]

I can only speak to what I have done, and I'm not a professional..soo

I have an Anderson scraper (carbide) as well as a carbide scraper I made from HRS and a carbide blank. I roughed them out on a green SC wheel on the bench grinder. The arc you want depends on the purpose, for finer work, you want a smaller radious, for larger work, and roughing, you want a larger radius. Start with a 3-4 inch radius (I have heard people suggest using the lid of a coffee can as a template) for general work, and maybe something around 2" for finer stuff.

I finished my edges with a diamond hand lap (2000 grit IIRC). I ground my angles at 90 degrees, mostly because that was the only way I could get good flats. I have had people insist that the angle must be 93 degrees, but I have not tried it. 90 seems to work just fine.

Nick Mueller has a good video on how he sharpens, check it out (and his other scraping vids, they are very well done.

[video=youtube_share;uIvxXMDeCIc]http://youtu.be/uIvxXMDeCIc[/video]

 

[Metalmann]

I picked up a couple of Anderson solid shank scrapers (non-round-type) at a local flea market. One appears to have a HSS insert and the other is carbide. I also have a full complement of bench grinder, oil stones, and DMT plates for sharpening purposes, but what is the recommended procedure for sharpening these tools? I've heard that the green grinder stones tend to chip carbide. How much camber, or curve, do you give the edge, what angle should the edge come to, and what grit do you finish with? Thanks in advance,
Mr. Inquisitive

This guy demonstrates the method of scraping in a cheap Chinese lathe. As long as the green wheels are balanced and true, there's no reason not to use them. Some shops used only green wheels for carbide. :


http://www.youtube.com/watch?v=D1eOQa1gYiU&feature=player_embedded

 

[Mr. Inquisitive]

Thank you for that information. I think that video is the only one of his I must have missed! It's interesting to see that he's grinding and lapping in a direction that is considered a no-no for other tool steels because the grooves caused by the grinder and diamonds tend to be parallel to the cutting edge, rather than perpendicular, which is supposed to create a very delicate edge. But I'm the guy asking questions so don't take my word for it.

Are carbide tool steels good for creating grooves and other decorative patterns in regular grinding wheels, rather than using the green carbide-approved grinding wheels?

 

[Richard King]

Recently at the Minneapolis Scraping class I taught one of the students had been using his hand lap to sharpen his Anderson hand scrapers. I tested it against the blades I sharpened on my Glendo Accu-Finish I with a 600 grit wheel diamond grinder and there was no comparison. The student who had been hand lapping his blades was pushing 10 times as hard and not getting anything off. If the blades are sharpened correctly you can "hog" and "smoke" off the metal. If you checked the depth of the cut with a dial indicator you should be able to get .002" deep. I say when scraping normally to get a finish, you get .0002" to .0005" deep.

A week ago that student dropped by the shop I was working/scraping sharpened his Anderson blades. He saw the light on how to sharpen his blades. When I was a kid 45 years ago I hand lapped my high steel blades. I may sharpen my pocket blade that way now, but not a scraper blade.

If you own a double end grinder with a tilt table you use to sharpen your lathe tools. Buy a 250 or 300 grit 6" x 1" x 1/16" side facing diamond wheel and tilt the table up in back 5 degrees if your scraping cast iron and on average. (keep the wheel wet) you sharpen both sides of the blade and if you look at the blade from the side you can see 2 cutting edges with a line down the middle. To say it simply it will look like a roof, middle higher the edges. Scraping steel and plastics you sharpen it at different angles. More later if your interested.

When scraping iron you need a blade that is sharp and using a green wheel will leave little ridges on the blade. I say to run you fingernail edge down the edge of the blade and it should be smooth, the green wheel will leave the ridges and you can feel them with your fingernail. If you look at the DAPRA.com web site and click on Scrapers and tools, look for a radius gauge. You can make one of these or buy one. It is a guide you can use to sharpen the blade tip. For roughing I recommend the 90 MM Radius and for finish I recommend 60 r or smaller 40 r . Or 90 = proxy.. a 4" circle and 60 a 3" circle radius.

Another scraping teacher, Forest Addy has written about a home made lap mahine he makes and recommends using a 6" plate he impregnates with diamond powder. I have seen it and it works well. I bet if you Google that you can find it.

The bottom line is as a Professional Scraper I carry in my tools a Glendo lapping machine with a 600 grit diamond wheel as I need a sharp polished edge to cut a smooth scrape mark. The green wheel will leave little scratch marks inside the cut. Unless your a super steady hand a hand lap makes it better then a green wheel, but a regulated angle device using a 300, 600 and even 1200 grit diamond wheel is the clear and best method for sharpening scraper blade.

Sorry for not writing more and sooner, but I have been super busy rebuilding machines.
Richard

 

[DMS]

Recently at the Minneapolis Scraping class I taught one of the students had been using his hand lap to sharpen his Anderson hand scrapers. I tested it against the blades I sharpened on my Glendo Accu-Finish I with a 600 grit wheel diamond grinder and there was no comparison. The student who had been hand lapping his blades was pushing 10 times as hard and not getting anything off. If the blades are sharpened correctly you can "hog" and "smoke" off the metal. If you checked the depth of the cut with a dial indicator you should be able to get .002" deep. I say when scraping normally to get a finish, you get .0002" to .0005" deep.

A week ago that student dropped by the shop I was working/scraping sharpened his Anderson blades. He saw the light on how to sharpen his blades. When I was a kid 45 years ago I hand lapped my high steel blades. I may sharpen my pocket blade that way now, but not a scraper blade.

If you own a double end grinder with a tilt table you use to sharpen your lathe tools. Buy a 250 or 300 grit 6" x 1" x 1/16" side facing diamond wheel and tilt the table up in back 5 degrees if your scraping cast iron and on average. (keep the wheel wet) you sharpen both sides of the blade and if you look at the blade from the side you can see 2 cutting edges with a line down the middle. To say it simply it will look like a roof, middle higher the edges. Scraping steel and plastics you sharpen it at different angles. More later if your interested.

When scraping iron you need a blade that is sharp and using a green wheel will leave little ridges on the blade. I say to run you fingernail edge down the edge of the blade and it should be smooth, the green wheel will leave the ridges and you can feel them with your fingernail. If you look at the DAPRA.com web site and click on Scrapers and tools, look for a radius gauge. You can make one of these or buy one. It is a guide you can use to sharpen the blade tip. For roughing I recommend the 90 MM Radius and for finish I recommend 60 r or smaller 40 r . Or 90 = proxy.. a 4" circle and 60 a 3" circle radius.

Another scraping teacher, Forest Addy has written about a home made lap mahine he makes and recommends using a 6" plate he impregnates with diamond powder. I have seen it and it works well. I bet if you Google that you can find it.

The bottom line is as a Professional Scraper I carry in my tools a Glendo lapping machine with a 600 grit diamond wheel as I need a sharp polished edge to cut a smooth scrape mark. The green wheel will leave little scratch marks inside the cut. Unless your a super steady hand a hand lap makes it better then a green wheel, but a regulated angle device using a 300, 600 and even 1200 grit diamond wheel is the clear and best method for sharpening scraper blade.

Sorry for not writing more and sooner, but I have been super busy rebuilding machines.
Richard

There is a series running in Home Shop Machinist on scraping. I think it is the 3rd or 4th volume where the author gives plans and instructions for building a rotary lap out of a CI disk, and a cheap bench grinder. To keep things straight with the hand lap, I clamped the scraper to a block on my work table, and clamped the hand lap to a 90 degree angle plate. I agree, a power lap has got to be better, but in a pinch, I got a lot of miles out of this method.

Here is the unit I mentioned. http://www.accu-finish.com/seriesone.html

Anyone who uses a green wheel to sharpen a scraper blade is clueless to scraping. Sharpening lathe bits free hand is what they are used for. A professional machinist or Tool and Cutter Sharpener has green wheels mounted on a double end tilt table grinder to keep the angle the same. I have a Glendo I purchased 20 years ago and have replaced the 600 grit diamond wheel 3 times and this little machine has been used in hundreds of scraping classes and when I am scraping and rebuilding machine tools.