Home Made Turning Scraper Burnisher

[CHJ]

Following on from posting about Burnishing HSS Turner Scrapers in Jonzjob's Thread I dug out my home made version of of a burnisher.

I used a scrap solid Carbide Endmill as the burnishing post and because I have no means of machining a taper as per the commercial items I set it at an angle, approx. 5deg. which seems to work OK.

As I do not have alternate Burnishing post with differing angles, If I need to increase the attack angle to increase the edge pressure I place a large packing washer on the pivot stem to lift the scraper handle.

 

[Silverbirch]

Ingenious!


Ian

 

[duncanh]

Nice idea. It looks to be better than the Veritas one for thinner scraper tips as they can be placed flat on the base without any packing material - the veritas one has the taper starting part way up, which I always thought was inconvenient.

 

[Jonzjob]

That looks good Chas!! I don't suppose that you have one spare :mrgreen: :mrgreen:

No seriously, I htink that I will have to see if I can get hold of a small bit of hard steel and bodge one up? I know of an engineering company that may be able to help?

 

[CHJ]

If you can locate someone involved with machining some of the more exotic metals (I.E Aero engines parts, even titanium etc.) then they may well have some solid carbide bits in the scrap bin. Things like Drills and Endmill cutting edges shatter with remarkable ease with a moments inattention. I know we always had a waiting list from hand carvers amongst the staff for making their own burnishers for card scrapers etc.

 

[Jonzjob]

Ta for the info Chas. The eng works do aero work, so I think i will bone up on some new words and get in there? Better still, I may well take a mate wot speaks much better French than me!

 

[CHJ]

You will know if it's solid Carbide, it will feel twice as heavy as you were expecting for given size and it will be charcoal grey to black in colour. Someone drilling out spot welds may have some old Cobalt drills that they have broken and they may be hard enough.

 

[Paul.J]

Chas i'm confused,as usual
Is this used to put a burr on a normal scraper like you would on a cabinet scraper :?:
Confused because i thought the burr the grind stone creates was enough to use for turning,as seen in many DVDs etc :?:

 

[CHJ]

Chas i'm confused,as usual
Is this used to put a burr on a normal scraper like you would on a cabinet scraper :?:

Yes, needs a lot more mechanical pressure on HSS than on a cabinet scraper, hence the need for the leverage.

Confused because i thought the burr the grind stone creates was enough to use for turning,as seen in many DVDs etc :?:

The burr left by a grindstone that is not cutting as sharply as it might, (relates to most wheels used in a home workshop) only produces a burrs similar in nature to the splinters on the rear of a piece of unsupported wood. They will most likely break away rapidly as soon as they come into contact with hard wood, a mechanically deformed edge should be better supported and provide a longer lasting edge.

 

[robo hippy]

I use scrapers a lot for my bowl turning. I prefer a good heavy scraper with a good burr for finish cuts at a shear angle (45 degrees or more). Most of the time I use the burr straight from the grinder. If I just kiss the bevel, I get a very fine burr that is gone in seconds. It is slightly more durable than a honed burr. If I push it into the wheel a bit, I get a good sturdy burr that is excellent for heavy stock removal, and shear cuts. For difficult woods, I will burnish a burr on my scrapers. Hone off the grinder burr first, then I use a standard triangle card scraper burnisher tool for raising the burr. A few strokes, and I have a nice burr. It really doesn't take much pressure to turn a good burr. I have found it easier to get a good burr with the triangle burnisher than with the round one. Main thing is to keep the burnisher at 90 degrees to the top and/or bottom of the scraper, which the burnisher tool shown in the pics does easily. You do get a keener cutting edge with the burnished burr than you do with a grinder burr. I also use an 80 grit CBN (cubic boric nitride) wheel for grinding. It does leave a surface that is a bit more shiny than the standard 80 grit aluminum oxide wheel.

robo hippy

 

[graduate_owner]

Just found this. I am posting a reply so it will be in my posts and therefore easy to find when I am ready to make one.

K

 

[chipmunk]

I know it's an old thread but this is interesting because I never use a burr on any of my scrapers and in fact usually go so far as to hone the grinder burr off too.

Books by Chris Stott and Bert Marsh suggest that they hone(d) off the grinding burrs as well but can I ask Chas in particular, do you still think it's worthwhile?

Veritas I think is still the only firm making a woodturning scraper burnisher and seem to have a patent on it (http://www.google.com/patents/US5640888).

Many thanks
Jon

 

[CHJ]

...can I ask Chas in particular, do you still think it's worthwhile?

Jon

Just occasionally I will go to the effort of enforcing a burr, not easy on HSS and effect varies upon tool (not all HSS is the same even by brand)
I do work a lot with Grinder created Burr for that final 'paper dust/cotton wool' skim of some pieces where sanding would risk uneven removal of softer/harder areas.

Is it worthwhile? If not already in the arsenal of tools then personally would not consider such an accessory worth the expenditure, perhaps if you use older generation carbon steel scrapers it could become a regular user, I'll have to get hold of or make one to assess that possibility, Burr scraping is certainly very satisfying as a finish.

 

[chipmunk]

Thanks Chas - It's certainly an interesting topic whether to form a burr or not.

I wonder whether as you say it's a hang-over from the Carbon steel days and perhaps with the advent of HSS tools, replaceable tip scrapers and shear scraping whether using anything over and above a grinder burr is a dying art?

Jon

 

[CHJ]

There is no doubt the use of a properly burred cabinet scraper cuts wonderfully on many difficult subjects but I'm always nervous of using such with its potential to chop fingers if it catches or is presented wrongly on a spinning subject.
Hence why I stick to using conventional turning scrapers, I find it one step up or very similar to shear scraping with a sharp edge but does not have such a catch potential as getting a shear scraping winged bowl gouge presentation wrong.