Carbide scraper tooling.

[TorontoBuilder]

I have about 85 squarish carbide cutters that came off a helical jointer.

They're ~15mm x 15mm x 2.5mm with each cutting edge being a 150mm radius with 30 degree relief angle on the back. They have holes for a 6M torx bolt (of which I have about 100). The inserts look like this:

I thought about milling bar stock to make handles. The tip would have a 2.5mm recess with a radius rear wall at 30 degrees to mate with the cutter. I'd cut that with a ground HSS insert in a simple fly cutter.

I can make short handles, long handles, tool insert handles... bend, straight...

suggestions, thoughts etc welcomed

 

[Arbutus]

What a serendipidous post! I had tossed this out last week. Its a new spiral cutter head from a General 6" jointer

With nice springy handles these will make a very nice set of scrapers!

 

[TorontoBuilder]

What a serendipidous post! I had tossed this out last week. Its a new spiral cutter head from a General 6" jointer

With nice springy handles these will make a very nice set of scrapers!

View attachment 53416

Plus it feels a lot better than tossing close to 100 carbides in the trash

 

[Arbutus]

I'll save you the trouble of measuring the inserts. Making an 80.9mm fly cutter will be a challenge though!

 

[TorontoBuilder]

I'll save you the trouble of measuring the inserts. Making an 80.9mm fly cutter will be a challenge though!
View attachment 53422

Yes, or course you are correct. That's a pretty wide fly cutter. On second thought I'll grind that feature after custom profiling a grinding wheel. I have about 50 of them I can spare one.

 

[TorontoBuilder]

Or I can make a massive fly cutter... since I seem to recall a video of just that by inheritance machining.

Then just cut the pocket for the insert to ensure a 30 degree angle at the lead end. Like this:

 

[PeterT]

You probably know this already but the typical edge geometry angles looks like this. I'm hopeful it could work because your carbide inserts appear to be planar (as opposed to lathe/mill cutters with chip breaker geometry) + dimensionally about right + uncoated + suitable carbide grade + enough meat before the screw hole might present weakness issues... You would need some kind of motorized diamond dressing wheel but I think that goes along with the scraping tool arsenal anyways. The end of the holder might have to be modified from your pic if you want to do the insert flip to expose a fresh edge. Maybe @Mcgyver will weigh in. I'm sure re-purposed carbide isn't an original idea. The fact that you have a pail full is worth trying. Also this edge geometry is for CI. Steel has a slightly different angle geometry.

 

[PeterT]

carbon steel scraping

 

[TorontoBuilder]

You probably know this already but the typical edge geometry angles looks like this. I'm hopeful it could work because your carbide inserts appear to be planar (as opposed to lathe/mill cutters with chip breaker geometry) + dimensionally about right + uncoated + suitable carbide grade + enough meat before the screw hole might present weakness issues... You would need some kind of motorized diamond dressing wheel but I think that goes along with the scraping tool arsenal anyways. The end of the holder might have to be modified from your pic if you want to do the insert flip to expose a fresh edge. Maybe @Mcgyver will weigh in. I'm sure re-purposed carbide isn't an original idea. The fact that you have a pail full is worth trying. Also this edge geometry is for CI. Steel has a slightly different angle geometry.

View attachment 53441

In my design the insert can rotate to use all four sides.

Grinders are the one thing I have plenty of, even in my own shop in my basement I have 3 grinders. One with dual CBN wheels for wood lathe tool grinding, one with a diamond cup wheel and a flat diamond wheel, and one for normal grinding wheels.

I was hoping that I could use the inserts as is, but since I plan on making a grinding jig for the radius I could easily flip the insert and put an opposing grind on them.

As far as strength of the inserts, I have so many I can afford if some break. But they held up well enough jointing hardwoods at 4400 rpm so I can't see myself putting breaking forces into the insert while hand scraping, particularly with that 5 degree bevel to make the edge blunter

 

[Mcgyver]

Like Pete says, you need an obtuse angle. I think i've got my lapping machine set at 92 or 93. Less and the tool will bite in enough that you won't produce enough force to move it.

Also, the very small cut involved in scraping (0.0001") means the edge must be very fine, else it just bounces along. A perfect edge of course is the intersection of two perfect planes ..... so before I silver solder on the bit of carbide, I lap the top and bottom of it to a mirror with 10 micro paste. Then for sharpening (you sharpen A LOT), it is just a matter of lapping the end

 

[CWret]

Thanks for starting this thread @TorontoBuilder - I also have a box of carbide inserts.

They came with the 80mm dia cutter in the pic above - it’s from a kijiji find. The box full of inserts are used but many are in very good condition. The deal also included 20 new inserts still in original plastic box.
So yes, an alternate use for these inserts would be of interest. (my inserts measure 12.7 x 12.7 x 4.9 mm & are Sandvik)

@PeterT thanks for the link to Stefan’s Scraping basics vid - I watched part 1&2 - as many others have said, Stefan’s youtube channel is one of the better ones.

PS - about the kijiji find - I went to see a guy nearly 2 years ago to get the dividing head he was selling. It was $225 (if i recall correctly). He was downsizing and giving up on his hobby metal working. In his small garage there was an empty corner where his lathe had been. He still had his mill but said a guy was coming from Quebec to get it. I ended up with the dividing head plus another $500 spent on all kinds of bargain priced tooling.

 

[TorontoBuilder]

Like Pete says, you need an obtuse angle. I think i've got my lapping machine set at 92 or 93. Less and the tool will bite in enough that you won't produce enough force to move it.

Also, the very small cut involved in scraping (0.0001") means the edge must be very fine, else it just bounces along. A perfect edge of course is the intersection of two perfect planes ..... so before I silver solder on the bit of carbide, I lap the top and bottom of it to a mirror with 10 micro paste. Then for sharpening (you sharpen A LOT), it is just a matter of lapping the end

When I start working on my grinding jig I'll post some images and angles for everyone's feedback.

Now that I plan to go to town on a bunch of hand planes I'm quite eager to jump on this project

 

[TorontoBuilder]

Thanks for starting this thread @TorontoBuilder - I also have a box of carbide inserts.
View attachment 53459
They came with the 80mm dia cutter in the pic above - it’s from a kijiji find. The box full of inserts are used but many are in very good condition. The deal also included 20 new inserts still in original plastic box.
So yes, an alternate use for these inserts would be of interest. (my inserts measure 12.7 x 12.7 x 4.9 mm & are Sandvik)

@PeterT thanks for the link to Stefan’s Scraping basics vid - I watched part 1&2 - as many others have said, Stefan’s youtube channel is one of the better ones.

PS - about the kijiji find - I went to see a guy nearly 2 years ago to get the dividing head he was selling. It was $225 (if i recall correctly). He was downsizing and giving up on his hobby metal working. In his small garage there was an empty corner where his lathe had been. He still had his mill but said a guy was coming from Quebec to get it. I ended up with the dividing head plus another $500 spent on all kinds of bargain priced tooling.

you suck

 

[TorontoBuilder]

You probably know this already but the typical edge geometry angles looks like this. I'm hopeful it could work because your carbide inserts appear to be planar (as opposed to lathe/mill cutters with chip breaker geometry) + dimensionally about right + uncoated + suitable carbide grade + enough meat before the screw hole might present weakness issues... You would need some kind of motorized diamond dressing wheel but I think that goes along with the scraping tool arsenal anyways. The end of the holder might have to be modified from your pic if you want to do the insert flip to expose a fresh edge. Maybe @Mcgyver will weigh in. I'm sure re-purposed carbide isn't an original idea. The fact that you have a pail full is worth trying. Also this edge geometry is for CI. Steel has a slightly different angle geometry.

View attachment 53441

So thanks to @PeterT I revised my scraper geometry for scraping cast iron. I'll grind off the sharp edge of the carbide to leave a negative rake angle of 5 degrees. I'll just spin the insert to grind all 4 sides. I can use a single grinding 150mm radius jig as for the other grind I have in mind, since I just need to vary the grind angle.

I will try a 5 degree positive rake angle for scraping mild steel, it will have a flat bearing surface to provide more control. Again I only need a single grind to remove the sharp edge. I have targeted a 25 degree grind, but a more acute angle can give a greater positive rake if needed. I got this idea from alex whose youtube channel is an engineer's findings

I will again round off the sharp corners.