Thread: I thought I was done on rasps- seems not - sharpening

Q picture of what some sharpened rasps can do piece of sheoak in 10 strokes

IMG_5901.jpg


The Wilkinson on the the left was quite a bit faster. After this photo tried to to see what a light touch would do. Found that I could use the Wilkinson like a saw. The Rasp was happy cutting way with its own wait and somewhat smoother lwith lest load.

The middle rasp is a Nicholson (subject of some other posts cause the stitching is curved which had not seen prior. It remained producing relatively Smooth finish.

The rasp on the right is another Nicholson with 380mm of stitching. As It turns it stitching patten is of interest as well . Machine made but slight sloped- so the when rasping at 90 degrees there is always at leat 2 stitches operating instead of the dreaded gap of machine stitched rasps. Somewhat smoother and easier start cause of it...

As sharp has qualiity all of own, as the machined versions are easier to sharpen, have developed an appreciation of machine cut rasps. Particularly for the rasps that are machine cut with small teeth / or are cut on slope. Both these version of machine cut rasps are less "notchy" to use.


In use after sharpening they are taking material with quite light pressure applied. The difference between the feel and finish of the very sharp machined rasps and the handcuts diminishes considerably.

After reading Mic-d post- was wondering how are rasps sharp in the first place
- = =a plane blade would be anything but sharp after heat treatment,mso what gives with rasps. Googled around and it was all voodoo to me- make surface smooth - keep the strike tool smooth and then heat treat and post sandblast - resharpening by soaking in acid

this does not sound like two straight lines that meet at apex.. Not snocked Paul purchased some rasps that were "blunt from new". A bit surprised rasps are ever sharp.

Tried Mic-d's cut at the back idea. Could bring not myself to do that on the flat - rotated the diamond block 30 degrees and gave the rows backs a polish. First impressions, seemed beneficial.

Still set up with a thin 1200 grit diamond disk. Might give the backsides of some rasps lick if I find a chance in the busy lead up to Christmas period..

Inspired by MicD post, gave the backside of the stitches a small grind- (with a thin diamond disk that can fit into that space). The rasp ground is reversing version with same stitching reversed on either side. good for a comparison

Initial impression was that it wasn't the day/night difference that the face grind was. ( ie completely blunt jump to quite sharp and taking alot of material). Tried to to a comparison- taking 20 strokes on a timber corner at around 30 degrees with a two hand action, then flipping and repeating with the other side.
Test is still pretty easy to bias, unfortunately and I was expecting a difference. That warning stated, seemed me the both faces ground side was cutting in around 15% deeper measured from the edge. Volumetrically a substantial improvement - nearly double.

Given it didn't take long to faces the edges - compared to the time spent rasping it suggest that both faces is the way to go.

Next time sharpening will try with small timber disk with a stitch sized notch. Rub in some diamond dust with oil and see if thIS WILL hone both faces of stitch at once. A small disk would make it easier to hone the hand stitched rasps as it more targeted.

So guess rasps are a tool that are used with varying degrees of bluntness but sharper one are a pleasure. The machined stitched ones in particular should be viewed as blunt in the same way a new plane blade is anticipated to need some sharpening when purchased.

Filed the back of the tips of my user set of rasps, having given credence to the test that suggested both face filed stitches was a significant improvement
After doing one file with the powered diamond disk, decided that was a touch crude and with small fine diamond file worked over the rest by hand aiming at rough 30 degree angleIMG_5913.jpg

The little shiny Barts are the touched up ends
The flat area adjacent is the finish that the pictured asp gave after sharping.

Don't think I can extract more out of these rasps- they seem pretty effective.

Thought I would add
- these rasps are pretty sharp - one thing I have noticed is the "notch" feel of machine cut rasps is not really present or if it is in a minuscule form. The rasps don't really stop for wood. Maybe if alot of pressure applied notchiness would return. Not tending to do that at beginning of stroke and once few teeth are running, well... it has missed its chance.

I have to wonder if there isn't some kind of aluminum oxide filament type product (think wire brush wheel) that could be directed top down on the teeth, but leaned toward the back.

Access to this page has been denied

well, that didn't take long. have an idea, someone has done it already.

Bristles are too fat for rasps, though. One of these in 220 grit with filaments a tenth the size would probably be about ideal.

Access to this page has been denied

well, that didn't take long. have an idea, someone has done it already.

Bristles are too fat for rasps, though. One of these in 220 grit with filaments a tenth the size would probably be about ideal.

Various types are all over the place, but one with finer filaments and smaller radius brings up a dead link.

A nylon brush running at lower speed in an abrasive slurry might do the same thing.