Thread: Sharpening Rasps. Is it possible?

A little drum roll from the drummer please, but before that I must grovel metaphorically of course, before the all-knowing Simplicty and humbly beseech forgiveness. Matt, the flat Wiltshire rasp is indeed a 4-in-1. The coarse side is different now I view it cleaned up and under the tender light of day as opposed to the deep and dreary darkness of night. More in a moment.

I cleaned the faces I was going to use with a brass wire brush and then conducted the tests: This pic is after the test so there is some timber in the teeth. From right to

An original 200mm blunt rasp with no treatment. I might well have called it a bastad if it was a file.
An original 200mm file soaked in white vinegar
An original 200mm blunt file soaked in Citric acid
An old Nicholson 300mm file (probably described as 12" back in the day)
A flat Wiltshire file now known as a 4-in-1

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I dispensed with the Spotty as it was clearly too hard to achieve any worthwhile result. Instead I used an offcut of Oak flooring that I have put throughout the house. It was dry when I bought it around ten years ago so I think it is still pretty much the same. It is much easier to work and far more forgiving. My secret nailer flooring gun makes short work of it. Instead of measuring how far a certain number of strokes took me as Neil did in post #37 I chose to count how many strokes it took to reach the far edge of the timber with the rasp held at a low angle (I appreciate "low" is not hugely scientific). These first two pix are the same test just slightly different angles of the camera to show what was happening.

I should comment that the Nichcolson is 50% longer than the "blunt from new" rasps so has an advantage there and the flat file being only half as long is at a disadvantage compared to all the others. The "blunt" rasps have a larger curvature so that should have given them an advantage. On the flat rasp the No.1 is fine (relative to the other end) and No.2 is coarse (very)

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Then I took them to the bench grinder charged the wheel with grey/black compound and buffed the back of the teeth with a stitched cloth and conducted the same test. The timber is 18mm thick incidentally. I hope I don't need that piece as I have barely enough timber to do the remaining floor area. Sorry, I conducted the citric and vinegar tests the wrong way around. The + sign represents the buffing aspect.

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This last bit is particularly for Matt. Coarse on the left side and fine on the right.

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The first pic below was the flat rasp (far left cut) on Spotty. The second pic was the same rasp (fine cut) after citric and buffing.


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I have run out of time for the moment, but the results are finally interesting. I will comment later, but in the meantime see what you think.

Regards
Paul

Originally Posted by Bushmiller

A little drum roll from the drummer please, but before that I must grovel metaphorically of course, before the all-knowing Simplicty and humbly beseech forgiveness. Matt, the flat Wiltshire rasp is indeed a 4-in-1. The coarse side is different now I view it cleaned up and under the tender light of day as opposed to the deep and dreary darkness of night. More in a moment.

I cleaned the faces I was going to use with a brass wire brush and then conducted the tests: This pic is after the test so there is some timber in the teeth. From right to

An original 200mm blunt rasp with no treatment. I might well have called it a bastad if it was a file.
An original 200mm file soaked in white vinegar
An original 200mm blunt file soaked in Citric acid
An old Nicholson 300mm file (probably described as 12" back in the day)
A flat Wiltshire file now known as a 4-in-1

P1080864.jpg

I dispensed with the Spotty as it was clearly too hard to achieve any worthwhile result. Instead I used an offcut of Oak flooring that I have put throughout the house. It was dry when I bought it around ten years ago so I think it is still pretty much the same. It is much easier to work and far more forgiving. My secret nailer flooring gun makes short work of it. Instead of measuring how far a certain number of strokes took me as Neil did in post #37 I chose to count how many strokes it took to reach the far edge of the timber with the rasp held at a low angle (I appreciate "low" is not hugely scientific). These first two pix are the same test just slightly different angles of the camera to show what was happening.

I should comment that the Nichcolson is 50% longer than the "blunt from new" rasps so has an advantage there and the flat file being only half as long is at a disadvantage compared to all the others. The "blunt" rasps have a larger curvature so that should have given them an advantage. On the flat rasp the No.1 is fine (relative to the other end) and No.2 is coarse (very)

P1080866.jpgP1080865.jpg

Then I took them to the bench grinder charged the wheel with grey/black compound and buffed the back of the teeth with a stitched cloth and conducted the same test. The timber is 18mm thick incidentally. I hope I don't need that piece as I have barely enough timber to do the remaining floor area. Sorry, I conducted the citric and vinegar tests the wrong way around. The + sign represents the buffing aspect.

P1080868.jpgP1080867.jpg

This last bit is particularly for Matt. Coarse on the left side and fine on the right.

P1080869.jpgP1080874.jpgP1080875.jpg




The first pic below was the flat rasp (far left cut) on Spotty. The second pic was the same rasp (fine cut) after citric and buffing.


P1080878.jpgP1080879.jpg

I have run out of time for the moment, but the results are finally interesting. I will comment later, but in the meantime see what you think.

Regards
Paul

Paul,
Your sucking up an grovling as been noted [emoji849][emoji849].
Can someone please pass Paul a Napkin please.

Was it Ian who mentioned that liquid sharpening will of course remove material(Metal) from the whole tooth.
I keep just thinking if a tooth is blunt rounded over , the acid is just going too remove an equal amount of metal from the tooth, so just making it smaller but not sharper,??

Cheers Matt.

Paul, I "read" the pics the wrong way at first - I looked at the size of the divots & thought "nothing to see here, boss". Then I realised the real information is in the numbers below the notches! ...

Ok, so as I read it now, the buffing seems to have been the one treatment that made a consistent difference. It's not huge (or so it seems from the numbers presented) but may be significant. To be at all "scientific" you would really need to repeat the test a few times without knowing what treatment the rasps had had to eliminate 'expectation bias'. Maybe you can find someone who doesn't know what/if you've treated them to repeat the sequence (which might result in gaps in your new floor... )

So buffing would appear to do some good, at least, & as I can't see it doing any harm, I'm strongly tempted to give it a try on a couple of my older Liogiers that are getting well past their prime. It sure would be nice to bring them back to some semblance of their original state...

Cheers,

I have to stipulate that this was not a highly scientific test and really it was down to my impression. To start with, i cannot guarantee I was holding the rasps at exactly the same angle each time and neither can I guarantee the same amount of pressure.

With the "blunt from new" rasps there was insignificant change after the soaking in acid to say that it had any effect. Such difference as there were could be down to the individual rasps and inexactitude by me. However, the improvement after using the buffing trick (Unicorn method) spanned all three rasps and I think it is fair to say that it was worthwhile. Giving the rasps the acid treatment did not seem worthwhile.

The story with the Nicholson half round and the Wiltshire flat rasps was a little different. After soaking in citric acid both tools seemed more aggressive. As the files were so different to the first three, a comparison was not fair. However, the Nicholson felt as though it meant business and my feeling was that it was a definite improvement. The flat rasp was definitely more aggressive. The groves made were like car tracks in soft mud. The finer rasp performed much better than the coarser end.

When the Nicholson and the Wiltshire received the unicorn treatment ( I don't really know if I did it correctly) they improved yet again. I have never seen anything like the ruts created by the Wiltshire so that was clearly some improvement and the Nicholson felt like a rasp should.

My impression and I was going to say verdict, but I think that is a little too presumptuous, is that a combination of these techniques can produce a worthwhile improvement on a once good rasp in so far as it resurrects the tool to something approaching its former status. However, you may only be able to slightly elevate a tool that was stillborn and there the time and effort spent is contentious at the very least.

Regards
Paul

Originally Posted by Bushmiller

My impression and I was going to say verdict, but I think that is a little too presumptuous, is that a combination of these techniques can produce a worthwhile improvement on a once good rasp in so far as it resurrects the tool to something approaching its former status. However, you may only be able to slightly elevate a tool that was stillborn and there the time and effort spent is contentious at the very least.

Paul

If you got some improvement from the acid etching dip I expect that the reshaped teeth edges from that will be more durable than the very fine edged teeth you get from buffing. The finer edge from buffing will cut quicker to begin with but is unlikely to last very long and will need to be refreshed. As you suggest, a combination of the two methods might give the optimum result. It may also depend on how much you are in a hurry to get the rasp cutting again. One thing going in favour of buffing it is very quick.

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On calling the buffing the unicorn method, to be fair to DW he never used that term in relation to rasps. As I understand it he used the term in relation to making the edge on softer chisels more durable. I'm not sure it is working exactly the same way on the rasps.

Neil

I have probably not used the term "unicorn method" correctly so my apologies to everyone for that and David (D.W.) in particular. If we go back to basics, a sharp edge is the perfect meeting of two surfaces. The "Unicorn" takes an extra acute meeting of the two surfaces and very slightly rounds the edge to give greater strength. My take on this is that there is a minute trade-off in sharpness for longevity. It is a beneficial trade-off.

The "buffing" of the back of the rasp tooth may have removed a little bit of metal rather than round over an edge or it refined (I use the term refined extremely loosely here) what was a ragged edge following the acid treatment. It may even have done both.

The acid treatment may have eaten away metal at the tooth edge and it is unlikely that it would be anything other than ragged, although arguably more aggressive than before. Fortunatelya coarse rasp is not expected to provide a fine finish. At best this is a very crude technique and if it was the edge of a chisel, we would all be horrified at the "mountain range."

I have some cheap jeweler's loupe's and I will see what the edges look like under that. It could be that the "blunt from new" rasps could stand a lot longer with the buffing process. There is no problem subjecting one of them to an extreme treatment, because there is nothing lost.

Regards
Paul

Originally Posted by Bushmiller

It could be that the "blunt from new" rasps ....

I think that the correct term is safety rasp, Paul, especially designed do that they will not accidentally cut your delicate fingers.

Originally Posted by GraemeCook

I think that the correct term is safety rasp, Paul, especially designed do that they will not accidentally cut your delicate fingers.

OR can be given to small children as birthday and Xmas presents knowing they can do no harm to themselves or others!

Regards
Paul

Hi Paul.

Have a hand stitched rasp that was no longer cutting well. Couldn't abandon the a hand stitched rasp, it seems, so I did this.

Aligned a thin 1mm 1000 grit diamond coated plate at 90 degrees to the rasp. Then working down the faces gave the teeth rub with the plate. I moved down the face of the rasp rubbing each time I felt it "click" against a tooth - This was a somewhat random . I repeated this process a few time assuming I had missed quite a lot of teeth each pass.

Flipped the rasp around, angled the plate at 30 degrees approximately and worked the other way, on the back of the teeth.

The process did not take long as each tooth is tiny so I assumed "sharpening" would not take much..

Subjectively speaking as I did not take before and after measurements - That would be too much thinking the rasp seems to work now like I would expect for its grit....

Encouraged, I also "sharpened" some very old machine made Nicolson file. That was quicker again as the teeth are aligned. They work as well as one could expect for a machine aliged teeth rasp- cut well enough, but rough and harder to start... no miracles.