A fuller scraping tool...almost! Troubleshooting?

[Adam Betts]

Hello, fellowsmiths! 

Short version: My fuller scraping tool stopped cutting part way through the work and I'm not certain why, and I figured somebody here might know! 

Long version (with pictures and an idea):

I rigged up this fuller scraper out of scraps, as sort of a proof of concept. The cutter is a scrap of blade steel, which I burned into a piece of poplar and epoxied. The arc has the diameter of a penny at the bottom, and widens toward the top-- it is not a circular curve. 

It worked really well and made lots of little shavings, until it didn't. I have reached a point where the fuller is almost but not quite done, but the cutter just seems to have stopped having any effect. I tried sharpening it, but that didn't help. The sound even changed from a screechy horrible sound to a less offensive grinding noise, and it's barely making dust now. 

Does anybody have any insight into why this might be happening? I'm thinking that I'm trying to cut too much surface area at once, and I lack the mass to get the cutter to bite. 

If this is the case, has anyone tried making a serrated cutter? I'm thinking like a toothing iron, for those of you familiar with olde-timey woodworking. If I file notches in the cutter, it would reduce the contact area of the cut, and then I could clean up the resulting surface with another cutter, or with sandpaper, depending on the resultant surface. 

Thank you for reading my quite possibly incoherent thoughts on this! 

Edited April 2, 2018 by Adam Betts
Spelling, and brevity.

[GEzell]

Is the steel you're cutting a fuller in annealed?  There is a possibility that you've work hardened it with the work you've done.  Honestly though, Imy first guess as to why it's stopped working would be that it's gotten dull, you could try using it on a piece of mild steel to test your resharpening.  The scrapers I've made have an edge angle just shy of 90°, and care must be taken when resharpening not to round the edge... The angle of attack that they cut best at is also a bit tricky due to the design I came up with.

I hope that was helpful and that you can get it to cutting properly again.  If all else fails you can make a new cutter....

 

[Alan Longmire]

I suspect it may be the angle of attack has changed.  As you go deeper your angle will necessarily open up with the setup you are using.  And what George said about sharpening is very good advise too.  I have made a couple of these over the years.  Some work great, but the big one has never worked at all.  I finally realized it's because the way the cutter is ground and mounted makes it impossible to get a bite on the steel because the handle is in the way.  I wonder if that's happening here?

[MatthewBerry]

I’d give careful attention to the areas at the edge of the fuller. As the tool cuts deeper more blade is engaged.  If you don’t have a good edge on the scraper on the areas newly engaged right at the edge of the fuller, it may be riding on those.  Try putting sharpie on the scraper and then take a pass - it will show you where the tool is contacting the fuller

[Brian Dougherty]

What everybody else has said.  Because of the curve of the fuller, and the angle that the scraper blade is coming into contact with the steel, the angle of attack is probably not the same all the way around the cutters edge.  At least that would be my guess.

Any easy test is to do what George suggested.  Try cutting a new fuller in a piece of scrap steel.  If it starts cutting well again, then it is probably a problem with the cutting edge geometry.  If it doesn't cut well, your scraper is probably dull.

[Adam Betts]

Thanks for all of your advice, guys! Responses, one at a time: 

15 hours ago, GEzell said:

Is the steel you're cutting a fuller in annealed?  There is a possibility that you've work hardened it with the work you've done.  Honestly though, Imy first guess as to why it's stopped working would be that it's gotten dull, you could try using it on a piece of mild steel to test your resharpening.  The scrapers I've made have an edge angle just shy of 90°, and care must be taken when resharpening not to round the edge... The angle of attack that they cut best at is also a bit tricky due to the design I came up with.

I hope that was helpful and that you can get it to cutting properly again.  If all else fails you can make a new cutter....

 

My steel is annealed, yes. It had occured to me that maybe I had work-hardened it, so as you can see in the picture below, I took a torch to it and heated it through all the tempering colors to see if that would help. No dice. 

I tried resharpening a couple of times, but did not notice an improvement. I also haven't done that much work with it, as I did forge in the fuller beforehand. I'm probably going to make a new cutter, though, out of 100% known steel, just to be sure I'm not screwing something up there. The edge angle on my scraper is much more acute than what you've used, so maybe I'm just ruining my edge really quickly. Thanks for that tip! 

8 hours ago, Alan Longmire said:

I suspect it may be the angle of attack has changed.  As you go deeper your angle will necessarily open up with the setup you are using.  And what George said about sharpening is very good advise too.  I have made a couple of these over the years.  Some work great, but the big one has never worked at all.  I finally realized it's because the way the cutter is ground and mounted makes it impossible to get a bite on the steel because the handle is in the way.  I wonder if that's happening here?

Alan, in your experience, does this type of cutter bite better with the handle angled up away from the steel, or down towards it? I did actually end up cutting a handle into the wood block, so I can keep the handle at a negative or positive angle. 

4 hours ago, MatthewBerry said:

I’d give careful attention to the areas at the edge of the fuller. As the tool cuts deeper more blade is engaged.  If you don’t have a good edge on the scraper on the areas newly engaged right at the edge of the fuller, it may be riding on those.  Try putting sharpie on the scraper and then take a pass - it will show you where the tool is contacting the fuller

I didn't think of this potential problem, Matt, but the tempering colors are functioning like sharpie here, so I was able to check your hypothesis. The tool seems it be cutting just fine at the edges of the fuller-- if I put sideways pressure on the tool, I can still take nice little shavings off of the edges. When I try to cut right down the center, I get a little bit of dust and make no progress. 

3 hours ago, Brian Dougherty said:

What everybody else has said.  Because of the curve of the fuller, and the angle that the scraper blade is coming into contact with the steel, the angle of attack is probably not the same all the way around the cutters edge.  At least that would be my guess.

Any easy test is to do what George suggested.  Try cutting a new fuller in a piece of scrap steel.  If it starts cutting well again, then it is probably a problem with the cutting edge geometry.  If it doesn't cut well, your scraper is probably dull.

I'll definitely try that, Brian. And I am absolutely going to make a new cutter anyway, out of 1/4" W2 this time. 

Should I temper the cutter at all, or leave it fully hardened? I didn't actually temper this one at all, since I am pretty sure it's 80CrV2, which isn't quite the ideal material for such a thing. 

Thanks again for taking the time to respond, gents. I'll experiment a bit with all of this in mind. I have tried making fuller scrapers before with no luck, but I need this one to work. I don't need to tell you that there's a lot of time into that blade already! 

Edited April 2, 2018 by Adam Betts

[Alan Longmire]

For the ones that work for me, the bit needs about 5 degrees of relief, i.e. just less than a 90 degree angle.  Raise or lower the handle until it bites.  The one that wouldn't work was because I couldn't lower the handle enough to make it bite.

[MatthewBerry]

I’d definitely temper the cutter. I don’t know w2, but something like 400 degrees maybe(?).  Full hard will chip, even if you can’t see it.  

[AJ Chalifoux]

Grind-your-own lathe tool blanks are also available and come pre-hardened. They're made for nearly this exact purpose.

[Alan Longmire]

Exactly!  At least look up how to sharpen a lathe or shaper cutter.  You will be using the same edge geometry as a shaper tool.  And a lathe cutter, but those are sideways so it's hard to picture sometimes.  

[Adam Betts]

8 hours ago, MatthewBerry said:

I’d definitely temper the cutter. I don’t know w2, but something like 400 degrees maybe(?).  Full hard will chip, even if you can’t see it.  

I will definitely do that with version 2. I didn't temper this one because I seriously doubt my ability to get full hardness from 80Crv2 with my setup, but micro-chipping might explain some things.

7 hours ago, AJ Chalifoux said:

Grind-your-own lathe tool blanks are also available and come pre-hardened. They're made for nearly this exact purpose.

I  had exactly the same thought the first time I tried to make a fuller scraper. Made a fancy metal handle/bit holder for them and everything (I'd be using that now, but it's buried somewhere in the chaos that is the boxed-up remains of my old shop an hour or so away from me). This fuller is considerably larger than the standard 1/4" blanks you find everywhere, though, and for the price some of the larger cutter blanks you can buy most of a bar of tool steel. Good tip for anybody reading this who wants to do tiny fullers, though!

5 hours ago, Alan Longmire said:

Exactly!  At least look up how to sharpen a lathe or shaper cutter.  You will be using the same edge geometry as a shaper tool.  And a lathe cutter, but those are sideways so it's hard to picture sometimes.  

Done and done! My grandpa taught me a bit about sharpening lathe bits once, and I refreshed my memory before I started on this project. The edge geometry on this tool started out like a lathe cutter, but I had absolutely no luck with it that way, so I decreased the angle of the edge, which seemed to help. I have a feeling that I got overzealous and went too far in the other direction, though, since the edge wore much faster than it should have (this might also tie in with Mr. Berry's point about edge chipping).

I'm hoping to experiment further with this tomorrow. I'll let y'all know if I get it right.

Thanks!