burning groove inside a bowl

[tandemsforus]

Neophyte wood turner here
I have been trying to burn a groove on the inside of a bowl with less than impressive results.
8-12" bowls of hard maple
I have tried .020 micarta, .020 Formica, ugly smell but little burn, small hardened steel rod ground to .020 then bent over , and nails ground to .020 then bent over. The burn in is slight and not consistent. I have been turning the bowls at between 700 to 1000rpm.
Any ideas that might help?

 

[Mike Davis]

I think the problem is the small area of contact, when wire bring on a spindle the metal is in contact with a couple inches of wood so it builds up heat from the friction. When you have a small area of metal contacting the larger diameter of a bowl the wood has so much more time to cool and dissipate the heat.

Also, I think it may be harder to apply as much pressure on the inside of the cylinder.

Maybe heating a thin sheet of metal red hot after it has been cut to the same shape as the inside of the bowl?

 

[Raymond]

I am of the same line of thought as Mike - you may need to create a branding iron (so to speak) and apply that to the bowl while it is stationary.

 

[Mike Davis]

Or turning very slowly...

 

[Dee2]

Use a round nose (cabinet) scrape with the burr removed. Maybe risk sacrificing the temper by heating it up. More area for you to grab.

Klingspor has a pack of 3-5 scrapers of different geometries. They're not all that expensive.

If you have an old (non-carbide tipped) cut-off saw blade and grind down the cutting edge to a round profile you could do the same and get a heavier line.

Just thinking outloud. Never tried any of this so YMMV.

 

[Steve Martin]

Recommend taking a piece of scrap hard maple from your original piece of wood about the width you want the burn to be, and long enough to keep your fingers away from the tip. Then set your speed at about 350 rpm's., hold the piece firmly in place where you want the burn to be, then increase speed about 100 rpm's until you get the heat and color you want. A piece of black walnut may also work at a lower speed. Sharper piece of wood, maybe dry pear, dogwood, or some exotics might also work. Just fiddle with what you've got until it works.

 

[Sam Knight]

My thoughts are similar to Steve. Try using a piece of scrap wood. I have used walnut with success. Turn a groove with whatever tool you have then hold the piece of scrap wood in place until the desired burn is achieved. Good luck!

 

[tandemsforus]

I tried a few ideas from here.
Heating and burning using metal would burn in some, but just was a lot of dangerous and for me potentially blister causing work as I reheated then tried getting it back into the grooves was not getting me where I wanted to be. I also tried to take a hacksaw saw blade ( the ends are rounded and thin) heated it and pushed it into the groove. Again it works some but not getting the results I am looking for. I will try a sharpened piece of wood and try that approach, See where that gets me. Good idea, thanks.

Thus far the formica/Micata seems to be working best. It smells pretty bad as it burns in, slow and I need to really push hard to make it work, thus I use a rag to support the back of the bowl. As a neyophte turner it just seems a bit dangerous using one hand to push formica in on one side and using a cloth to keep the bowl from deforming on the other.
Maybe make a roller from a roller blade wheel attached to a rod to support the back of the bowl?

 

[Raymond]

Yes, using a steadyrest would be a good idea. Check some of the existing ones:

https://www.google.com/search?q=lat...OuvLVAhWp1IMKHRWTDBoQsAQIiQE&biw=1760&bih=924

 

[Jim Wallace]

I think Mike has identified the problem. I think the solution I would suggest would be to make the groove you want burned with whatever tool you like, Then use a wood burning tool to burn the groove while spinning the lathe by hand. Just move the lathe as you get the amount of color you want. Remember that the line will look blacker after you put finish on it.

 

[Joe Bradshaw]

I use formica to burn grooves. The speed needs to be kept at a higher rpm. You want to generate a lot of friction and heat.

 

[TENdriver]

An alternate is to apply your finish to the bowl and cut a shallow groove. Then apply a dark stain/paint to the groove. Sand away the extra dark finish (leaving the darkened groove) and reapply your final finish to the area.

Not burning but it is a more controlled method and you can even incorporate a rainbow of colors.

 

[Pop Golden]

​I think your metal is too hard. I have had good success using copper. Try a dowell with a piece of #10 solid copper wire attached around the end. You might want to round over the burning end slightly.

Pop

 

[Rick M]

Neophyte wood turner here
.020 Formica, ugly smell but little burn,

Crank the speed up. Those Formica samples from the home center are the best thing for burning lines but no matter what you use, it works through friction. If the speed is too slow, it won't burn a line. If you hold it too long, it will remove the line you burned. Bailing wire will work, copper wire will not because it conducts heat too well. Never tried a nail. These lines were burned with nothing but a Formica sample. You can score a line with a skew so the Formica doesn't wander.