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Fireball Tool - Backstroke File Test

CalgaryPT

Ultra Member
Vendor
Premium Member
The reason I like Fireball Tool is not because of his big machines. OK, that's a lie. BUT I love how he questions knowledge and then tests his hypothesis. I don't think he is a disruptor for the sake of just stirring the pot; instead he really appears to be looking for answers. People like that appeal to me. This is his latest, "I wonder if..." video about the (fallacy) of lifting your file on the backstroke. I can't wait for part 2.

I think I have a bit of a man crush on this guy.

 

Dabbler

ersatz engineer
I'm looking forward to following this to its end. I think I know what the result will be... (as well as almost every follower of his test - either side)
 

CalgaryPT

Ultra Member
Vendor
Premium Member
Part II is out. No spoiler in my post though....

Great entertainment for geeks. However, it just occurred to me that he never defined the term "wrong" before doing the test. For example (and based on the original title of Part I), does "wrong" mean less effective in terms of generating chips? I think so, as he is basing his conclusions largely on the length of the coupon, which implies this.

However, "wrong" could also mean that back dragging dulls the file prematurely. While the microscope examination provides some information, it is not empirical data. To make it so he'd have to pick a similar square inch of the file and make a count of dulled vs broken teeth. He also introduces another definition of wrong in Part II—effectiveness of clearing chips. So lots of info here to contemplate.

 
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I saw the video a while back and all I can say is something failed the logic test (let alone what my grandfathers and grand uncles taught me about tooling in passing, all where master tool and die makers in the old country.wish I had them actually teach me but I was way to young).

A cutting edge needs to cut in one direction as it designed as such to handle the load and cause the best sheer of the material. Any tool that I check for sharpness or edge failure I look for shine on the edge (if there is one it is definitely past its prime) as the edge is gone. Files are the same, and reverse draw creates that.

Back to grandfather, his first year +/- was cleaning the shop while making a cchuck of metal perfectly cubic with a hand file (not new), taught a few things, material feel, measuring (in more ways than one), sharpening the file and most importantly filing. Lesson learned real quick never a pull stroke as you have to sharpen the file. BTW, second year was make the same piece perfectly round.

Back to the test, while it simulates filing it does not replicate what happens when you do a pull stroke, as you do damage the cutting edges and ulitmately break them. I can tell just in use where someone has used my files and pull stroked as the file cuts and responds differently (ie sucks), for that reason I have everyone files and don't touch my files in my shop, use mine you buy a new one on the spot.

Good video, faulty test and conclusion.

Finally, want to preserve your files life, file chaulk (failing getting some dedicated file chaulk, cheap dollar store kids sidewalk chaulk works fine), keeps scarf from clogging your files.
 

Dabbler

ersatz engineer
I respectfully disagree. And does my mentor who did tool and die for nearly 70 years.

I think the difference is that you should drag LIGHTLY on the back stroke, and cut on the fore stroke. 90 years of die filing also support his conclusions. If you've never used a die filer, you cut on both strokes with the teeth pointing downwards (of course less on the upstroke). A remarkable and highly acurate tool - and the files last a very long time.
 
I respectfully disagree. And does my mentor who did tool and die for nearly 70 years.

I think the difference is that you should drag LIGHTLY on the back stroke, and cut on the fore stroke. 90 years of die filing also support his conclusions. If you've never used a die filer, you cut on both strokes with the teeth pointing downwards (of course less on the upstroke). A remarkable and highly acurate tool - and the files last a very long time.
Might I suggest you run your other cutters backwards with light feed rates on every pass. Should have the same result ;) because this is what is being done. Think about it.

I think everyone on this site has read or seen one or two presentations on how cutting edges work so lets skip that, while extremely important, I'm going to assume its common knowledge for this conversation.

What most still have difficulty with is understanding how/why burrs form on edges. It is a form of molecular drag/rolling of material in the direction of cut, which is why cutting into to edges produces little to none. This applies to both material being being cut and the cutter (file).

If you look at the file closely enough you actual see a burr curling inwards on the edge on a pull stroke. On the push stroke the burr may be broke off (can actually be a good thing, if you truely understand sharpening) or not in which case the burr get thicker and stronger (bad thing). You now have a round edge shape similar to a ski tip that you are building during the reverse stroke.

Best analogy, think how a shaper works, it is essentially one tooth file, it does not cut on the back stroke.

As to your mentor, can't say how he did things, but can speculate....bear down on the push stroke, glide (no pressure) on the reverse stroke (btw this actually clears the teeth, done correctly). This clearing speed up the forward cut if its done correctly. This is also why file chalk is beneficial.

Most people actually apply pressure which causes the issues, see burr comments.

When teaching and learning truly lift on the reverse stroke to set the pattern, as you master the skill you will just skim (glide) on the reverse stroke (it is more efficient action) with no pressure.

Again the video test is faulty in design, leading to false conclusions without understanding the mechanism of what actually occurs to test correctly.

BTW my mentor(s) that taught me, close to about 300 years combined.
 
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Dabbler

ersatz engineer
I know this issue is a closely held thing and I have no interest in trying to convert you to a new way to thinking. I was taught by someone initially that held extremely your view and would kick anyone out of the shop for what he called 'backfiling'.

I then experienced the light back stroke filing with Bert. I have files that are 40 years old that are still quite sharp. I get good finishes. it works for me.

As for the video, it tests what it tests. He isn't as smart as 'tech ingredients' channel, but like an IQ test it doesn't test intelligence, just your IQ.

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What I hate to see is guys that slap the file onto their vise to dislodge the chips. There is no way that it doesn't break the cutting edges off the file.... Perhaps we can agree on this little point!
 
I know this issue is a closely held thing and I have no interest in trying to convert you to a new way to thinking. I was taught by someone initially that held extremely your view and would kick anyone out of the shop for what he called 'backfiling'.

I then experienced the light back stroke filing with Bert. I have files that are 40 years old that are still quite sharp. I get good finishes. it works for me.

As for the video, it tests what it tests. He isn't as smart as 'tech ingredients' channel, but like an IQ test it doesn't test intelligence, just your IQ.

------


What I hate to see is guys that slap the file onto their vise to dislodge the chips. There is no way that it doesn't break the cutting edges off the file.... Perhaps we can agree on this little point! :oops: YIKES, yes.
I think we are talking about the same technique (glide on the backstroke). For most (less experienced) this is beyond their grasp. Develop good solid basic technique first (hence no backstroke, remember most would also bear down on the backstroke) then learn the mastery of it (what you are doing).
 
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