Angle for Burr on NRS - Using a Burnisher

[Randy Heinemann]

When using a burnisher to put a burr on a negative rake scraper, is there an ideal approximate angle for the burr?

Also, is this angle created by tilting the burnisher toward the top of the scraper or tilting it toward the bottom?

Or, is the best angle just straight across or 90 degrees to the cutting edge?

I've looked at YouTube videos but there seem to be conflicting views and the videos don't always show how the burnisher is being held in relation to the cutting edge.

[John K Jordan]

Randy,

I have never measured the angle but I could if that would help. I just use "some" angle, probably just what I felt worked better with experience. This is what I do:

First use an extra fine diamond hone and remove any burr left by the grinder. (Can leave this on and use it for a few seconds until it wears away, then ticket the burr.)

Then I hold the scraper in my left hand and the burnisher in the right. I line up the burnishing rod flat against the the bottom bevel then lift it just a few degrees, apply "some" pressure and pull the burnisher towards me along the edge. The burr has to be turned up towards the top. You can feel it with your fingers/fingernail.

Some people put a tiny smear of oil on the edge before burnishing, especially on hand scrapers, but I rarely do.

I recommend grinding the NRS (bottom bevel last to leave a burr on the top), then test the grinder burr on a piece. Then hone off the grinder burr and burnish a burr and see how it cuts. Then burnish with a little more pressure, and/or a bit more angle, and test that. You will soon see what works best. The scrapers held flat on the rest should remove whisper shavings with a light touch, so thin they might even float around the room. More force against the wood should remove larger shavings. You shouldn't get just fine dust.

The burnished burr should last much longer than the grinder burr.

Sometimes I use a more aggressive burr when my usual burr isn't cutting as well as I want. Also, when the burr starts to wear away, I usually refresh it several times by honing/burnishing before I go back to the grinder.

You might be able to see some fine shavings coming off the wings of this piece. It might not look like it in the photo but the tool is held perfectly horizontally. I ground a flat on the end of this scraper and a curve down the side.

NRS_IMG_7515.jpg

JKJ

When using a burnisher to put a burr on a negative rake scraper, is there an ideal approximate angle for the burr?

Also, is this angle created by tilting the burnisher toward the top of the scraper or tilting it toward the bottom?

Or, is the best angle just straight across or 90 degrees to the cutting edge?

I've looked at YouTube videos but there seem to be conflicting views and the videos don't always show how the burnisher is being held in relation to the cutting edge.

[Randy Heinemann]

Can you burnish the edge more than once before going back to the grinder to grind the bottom bevel again?

[John K Jordan]

Can you burnish the edge more than once before going back to the grinder to grind the bottom bevel again?

As I mentioned earlier, "...when the burr starts to wear away, I usually refresh it several times by honing/burnishing before I go back to the grinder."

When I finally grind again I always grind both top and bottom, even if the two bevels are unequal. I have a variety of negative rake scrapers ground different ways, for example I ground to use with end grain such as box lids/bottoms, but those I use the most for larger pieces and for face turning are ground with equal bevels on both sides.

scrapers_neg_rake.jpg _scrapers_IMG_7778.jpg

On these I mark which side is the Top so I don't have to feel for the burr when I pick them up.

JKJ

[Reed Gray]

If your bevel on your NRS is 70 degrees, then you want the burnisher at about 72 to 75 degrees. You need a carbide burnishing rod, and a few light passes. If your burnisher is at too steep of an angle, you can actually roll the burr over so it won't cut, or will cut very poorly.

robo hippy

[Thomas Wilson80]

I was kindly given a carbide burnishing rod a few months ago but haven't had a chance to use it - what is the best way to make a burnisher? Is there a type of wood that is best for the handle and how have you set the rod into the handle securely (i.e. what type of glue/epoxy and how far into the wood, etc.)?

Thanks,
Tom

[John K Jordan]

I was kindly given a carbide burnishing rod a few months ago but haven't had a chance to use it - what is the best way to make a burnisher? Is there a type of wood that is best for the handle and how have you set the rod into the handle securely (i.e. what type of glue/epoxy and how far into the wood, etc.)?

Tom,

I've made several. The wood doesn't matter. I roughed up a little of the carbide rod with a diamond burr in a Dremel and epoxied it into a hole in the handle. I'm not sure the roughing was necessary but it certainly didn't hurt anything and I have a habit of doing that. I don't remember how far I put it into the handle - I don't think it matters much since there is not a lot of force on the rod but I could measure if you need it. I used 30 minute epoxy.

I've made several. This one is made from Osage Orange.

burnisher_IMG_6767.jpg

I made another handle from Rosewood, another from, hmm, can't remember. I gave it away. This one has a much bigger carbide rod but I like the smaller diameter rod better.

carbide_burnisher.jpg

JKJ

[Jenny Trice]

Great description of burnishing John. Thanks. What is the diameter of your small carbide rod in the osage orange handle? Are you buying longer rod and 'splitting' it? If so, how? What is a good source for the rod?

[John K Jordan]

Great description of burnishing John. Thanks. What is the diameter of your small carbide rod in the osage orange handle? Are you buying longer rod and 'splitting' it? If so, how? What is a good source for the rod?

The small one is 3/16" diameter. (Large is 5/16)

I don't know about the source. I got a number from a gentleman who had to buy in quantity to get a reasonable price. I don't know if he has any more. I've used several, sold some, and gave some away and I'm not sure if I have any left.

Another option is the Arno burnisher, made in France. It has both 3/16" round and triangular carbide burnishers mounted in a comfortable angle, both angled supposedly to make burnishing easier. I've had it for a couple of months and so far I like it. If I need a more aggressive burr on a NRS or hand scraper, the triangular rod can do it with less force. It's not cheap, though.

https://www.amazon.com/gp/product/B076GW8N5K/

JKJ

[Randy Heinemann]

Just curious, why must the burnisher be made of carbide? Wouldn't steel work? I understand that the steel would need to be harder than the scraper to work, but it still seems as if steel should work also.

[John K Jordan]

Just curious, why must the burnisher be made of carbide? Wouldn't steel work? I understand that the steel would need to be harder than the scraper to work, but it still seems as if steel should work also.

You can use steel, the harder the better. You can use a rod from hardened tool steel rod or HSS. The round shaft of a small HSS turning gouge works. You can even use the shaft of a screwdriver to burnish a hand (cabinet) scraper - I've tried all of those. But the harder the rod, the less wear. When I tried a screwdriver it appeared to work but the tool scratched the screwdriver shaft. A HSS rod on a HSS tool can mark the rod, probably scar it in the long run depending on the relative hardnesses- I haven't tried long term use. A carbide rod is much harder and seems like new even after years of use. A polished carbide rod is better since it slides on the steel - some say it makes a smoother burr but I don't have an unpolished one to compare with the microscope. As mentioned, some recommend to lubricate the steel lightly for a smoother burr. If the burr is not smooth it may not be as strong and according to some may degrade faster in use. Lots of room for experimentation for someone who has the time!

One source of a round carbide rod is a solid carbide end mill used for machining. Epoxy the cutting end into a handle and burnish with the shaft. I think my carbide end mills have polished shafts.

Polished carbide rods are widely available and are cheap, maybe $2 or less in quantity. You can even get one through Amazon. It's the shipping on small quantities that kills you.
https://www.amazon.com/Castlebar-Pol.../dp/B07GR9BKW3

Or maybe take a chance with this vendor, free shipping but "just launched":
https://www.amazon.com/ZCC-America-P...dp/B07P14VN79/

JKJ

[Randy Hogan]

Here's a link to a helpful video on the NRS from Boxmaster Tools. Around the 22 minute mark they show some techniques using a burnishing rod.

https://youtu.be/YsatMuK1Ei8

[Reed Gray]

I was chatting with Eric Loffstrom last weekend at the Oregon Woodturning Symposium. He prefers a 1/8 inch diameter rod. Not sure if it really makes a lot of difference though. I was able to burnish a burr on M2 HSS with the card scraper burnishers. The round one didn't work very well, but the triangle one did work fine. I still have some of the 3/16 by 1 1/2 inch ones left. You can PM me.

robo hippy

[Richard Dooling]

If you happen to know of a shop that makes Formica laminate tops, they may have old solid carbide flush trim bits. I don't think they were designed to be sharpened - we never did anyway. They aren't but about 1.5 in. long but that's enough to mount in a handle. They are .25 in. diameter.

[Thomas Wilson80]

Thanks for the specifics John.