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Post by Rob on May 2, 2014 20:48:59 GMT
My next question relates to ideal belt grits for maintenance. The 60 grit ceramic belts are superb for fast metal removal on the really tricky large surface area tools like the skew. A blessing to me after trying various less speedy methods. I've got my various skews all at a lovely 15 degree angle with a 20 degree pitch now just fine. My question relates to what belt grit would deliver the ideal maintenance regimen?
I ask this because when I got my PE I assumed that the low grit belts remove lots of metal and the high grit belts (I have 60, 180 and 320) move along a spectrum to the point where you're really polishing. For some reason I just assumed once the shaping was done, you could bring back the edge with the 320 on all the time because you're just tickling the edge. That in turn, being the finest grit I have, would deliver a well polished and razor sharp edge. In practice I'm finding that isn't necessarily the case and I'm still experimenting with whats best for me. I've found the 320 is a bit too fine for general maintenance and the 180 better. I've even been getting perfectly acceptable edges on the 60 and that's the fastest of course.
Whats the thinking in the Sorby camp on this please?
Cheers
R |
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Post by Jeff Farris on May 3, 2014 2:22:43 GMT
Sure that's not 120 and 240 grit? That's the standard packaging with the machine.
That said, the 240 (or higher) wouldn't be my choice for most tools for maintenance. I use the 120 for my bowl gouge when turning, until I'm down to the last couple of cuts. Then I go to a finer cut -- usually the 600 grit TriZact. The 120 is sufficiently coarse to give me a new edge quickly at the PE, and fine enough to produce an edge that lasts a reasonable time on the lathe. But, using the finer grit for the last cut saves me sanding time.
Now on skews, I'm a bit more finicky. I use the 600 TriZact and the cotton buffing wheel. If the edge requires a faster cut than the 600, I've spent far too much time at the lathe before touching up. I also use the 600 TriZact for my detail gouge (fingernail grind spindle gouge).
Another point here is abrasive type, as well as grit. The ceramic belts in 60 and 120 outlast the aluminum oxide belts by 3 or 4 to one, but are only a bit more expensive. When you replace the originally supplied belts, I strongly recommend you get the ceramics.
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Post by Rob on May 3, 2014 9:48:14 GMT
That's interesting advice Jeff. You know I'm really glad my knowledge holes prompted me to ask you to start this forum because this tool has such fabulous potential but sorely needs some information gaps filling. The documentation was a tad thin!
Let me explain my situation so we're not at cross purposes: I bought my machine 2nd hand so it didn't have any of the factory shipped abrasives (or manual which I downloaded). Those I acquired from a specialist abrasives firm and are indeed the exact grits I've documented. They are also ceramic until the higher grits which I don't think you can get in ceramic.
I've messed about and I think you're spot on with the 120 as the go to belt when in production. But your comments on the skew are interesting because though I've got the shape down now, my skew is definitely not razor sharp all the time. I got it perfect at the start but that was after shaping with the 60 and then running through the grits up to 320. Far too time consuming for production. Now I'm vacillating between 60 (fast but not that sharp) and higher belts which don't seem to remove enough metal. I hadn't thought that I'm letting it blunt too much before touching it up and I haven't looked into the Trizact stuff. That's the diamond pattern belts right?
Also, on the very tip of the long point. When you're doing a slicing cut through end grain to true up a spindle piece (or rolling beads) obviously its critical that the very tip is really sharp. I figured the flat that meets the two bevels ie on the side of the skew NOT the bevels themselves need also be perfectly flat as that forms part of the triangle wher the three faces meet. I've been truing that flat on the side of a well known grinding wheel. Does that make sense to you and do you think it helps or is it only the bevel geometry that matters?
This Trizact stuff though, whats the deal there? Its just amazingly tough diamond right, that lasts ages and can cut even carbide tips right?
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Post by Jeff Farris on May 3, 2014 10:11:22 GMT
Rob,
Be very wary of third party belts for the ProEdge. We use the same manufacturer for the ProEdge belts and for the belts we use in the factory. They are very carefully controlled in seam flatness, belt length and seam alignment. You'll not be bothered with bouncing or tracking issues if you use Robert Sorby belts.
I've never bothered coming across the top of the skew point. Not saying it is a bad thing, just have never found it necessary.
TriZact is a 3M product. The abrasive is aluminum oxide, not diamond. The secret of TriZact is not the abrasive material, but how it is applied to the belt. It is more "stacked" than "piled" like most belts. The careful alignment of the abrasive on the belt gives an incredibly consistent cut. The brick-weave pattern of the 600 grit gives the cuttings a place to drop away from the tool, thus also contributing to a clean cut. Unfortunately, it won't cut carbide. We offer a diamond belt that will.
Don't overlook the honing process on skews. I know you have "other" honing equipment, but the cotton buffing wheel on the ProEdge is really quick. Going from the 600 TriZact, it takes just a few seconds of buffing to bring up a mirror finish and a razor edge.
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Post by Rob on May 3, 2014 10:15:02 GMT
:-)
Great advice, many thank Jeff.
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paulm
New Member
Posts: 18 
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Post by paulm on May 3, 2014 19:04:47 GMT
Just a word of warning on the use of cotton buffing wheels on the PE. I used one briefly but found I had to dismount it after each use as if left in place while sharpening on the belt, hot metal swarf was landing on the buffing wheel causing it to smoulder and catch light !!! I stopped using the buffing wheel after that which is a shame as it did give a nice final polish. That may be because I leave the right hand cover permanently off the machine though in fairness ? Don't know if the cover provides the protection for the buffing wheel, but it's way to much of a fiddle for changing belts though so off it stays !  Cheers, Paul |
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Post by Jeff Farris on May 3, 2014 21:21:07 GMT
Paul,
It is necessary to take the buffing wheel off when not using it, side guard or no side guard. It takes less than a second to either put on or take off...just use it, take it off and proceed.
I'll not condone leaving the side guard off. Lots of open pinch points when it's off.
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