Tool Edge Micrographs

Discussion in 'Woodturning Discussion Forum' started by Jeff Gilfor, Jul 22, 2014.

  1. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
    Jan 27, 2005
    Messages:
    8,125
    Location:
    Dalworthington Gardens, TX
    Home Page:
    From an engineering perspective, my opinion is that while you are working hard to eliminate variables that would otherwise cloud the data, I am more concerned that the test methods that you envision appear to have diverged too far from real world conditions. Before proceeding into the test methods, I would suggest first clearly defining the fundamental objective. After that, variables can be more easily identified and, to the extent possible, determine if there are methods that can be used to mitigate their effects. Otherwise, I see a risk of making the test results not very meaningful.

    I understand the rationale behind the idea of normalizing the way that the cutter is used in the test, but don't believe that the power feed on the metal lathe is the right approach. There is a fundamental difference between metal machining and wood turning in the way that the cutter is used. In metal machining, the power feed is a position control system whereas woodturning is primarily a man-in-the-loop force feedback system (or to state it more simply, it is anything other than a position control system).

    Particle board and MDF are the next best thing to an aluminum oxide grinding wheel to my way of thinking. They both consist of a high percentage of very hard and abrasive bonding material (urea formaldehyde resin, in the case of MDF). The fact that they contain cellulose seems not especially relevant because, other than that, it doesn't have much else in common with cutting solid wood. It looks like the test would be mainly scraping an abrasive material rather than making a true cut that slices through real wood. If you're looking at gauging edge longevity, I think that scraping an edge against MDF isn't the right approach.

    For all of its ambiguities, it is hard to beat cutting real wood in the traditional manner as a measure of how well an edge holds up. There is no question of when the tool quits slicing wood and there is no need to look at a photomicrograph to verify that.

    I'm sure that you have turned MDF and particle board, so you are very familiar how nasty it is. Besides making a thorough mess of your shop with all of the dust that it creates, it is really bad for your lungs. If I must turn it, I will only do so outdoors with a breeze from my back and wearing my Airstream respirator. I would rather turn a banksia pod ... and I hate turning banksia pods. :D
     
  2. john lucas

    john lucas

    Joined:
    Apr 26, 2004
    Messages:
    5,823
    Location:
    Cookeville TN USA
    Bill I find it very difficult to accurately tell when a tool is getting dull. That's why it's so hard to tell if the V11 steel holds an edge longer than HSS. The other problem is I'm really looking for sharp edge holding not just when it gets dull. I have already proven that the V11 will outperform HSS when cutting aluminum. But in that case I'm pretty sure the really sharp edge was gone fairly quickly and the less than sharp edge holds up much longer on the V11. What I would like to see is how long each of these tools holds a really sharp clean cutting edge and that's a lot more difficult to quantify.
    Using the metal lathe feed may not be accurate but it has to be more consistent than feeding by hand. There are just too many variable when feeding by hand. especially on a test that might take a while since your likely to get tired and not "feel" the cut the same way on each piece. I don't know, I just figured if I'm going to the trouble to prove that each steel gets so sharp we can't tell the difference and I have these 3 exact tools why not try to see if I can tell how long they hold a really sharp edge.
    Ideally I would probably put a current meter on the metal lathe and keep cutting wood until it starts to make the motor struggle and change the current draw. That would be more accurate than me trying to feel it, but hey that's probably beyond me and the tools I have. I'm just having fun with this. I think I've already proven my point with the sharpening that I've done. Each of these tools so far is far beyond where any turner would normally sharpen to, and each of the steels feels the same in my simple tests.
     
  3. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
    4,306
    Location:
    Lakeland, Florida
    Home Page:
    John,

    You might try a strobe light. There was an article in the journal a while back and Ron Gerton did a nice demo at one of the AAW symposiums.
    The big advantage of the strobe light is that it stops the rotation of the work piece in your eye. So if you are working a piece with projections you can see them.

    The strobe Ron used picked up a timing mark so it adjusted to the drop in RPMS as the tools were cutting.
    A cut with less resistance should have a lower drop in RPMS.
    The strobe had an rpm readout.

    If you had an assistant they could record the RPMS and cut with a camera.

    Al
     
  4. Mark Hepburn

    Mark Hepburn

    Joined:
    Mar 26, 2014
    Messages:
    1,170
    Location:
    Houma, Louisiana
    Add in a DJ and a big flat screen and you may not get any results, but it'll be a fun experiment!

    And if you wait until August 9, the Titans first game is on.

    :)

    kidding
     
  5. Mark Hepburn

    Mark Hepburn

    Joined:
    Mar 26, 2014
    Messages:
    1,170
    Location:
    Houma, Louisiana
    Enough with the levity, sorry.

    Bill, it seems that your point regarding the difference between cutting wood and scraping something like MDF assumes that one cannot use a gouge in its "intended" manner against MDF? Not having turned any (except to make a couple of round sacrificial pieces) I just don' know; is that correct though?

    It seems that if John were to remove the variable of feed rate and angle of attack, then if the media is consistent, would would he not have isolated the data that he is looking for?

    If so, perhaps something like ash would be a good candidate for turning since it is pretty consistent?

    Or even as you mentioned, a quality plywood product with no voids? I know Jim Driskell over in the SWT forum turns out some amazing stuff in plywood.
     
  6. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
    4,306
    Location:
    Lakeland, Florida
    Home Page:
    Finding two blocks of wood that are equally consistent in density and hardness is impossible.
    At a given tolerance level finding two equal pieces of MDF, ALUMINUM, OR PVC is not possible as well.
    All of these materials can be cut and scraped.

    Finding a couple of pieces of wood within our ability to measure is easy.
    I have a KD poplar board 3" thick. It is pretty consistent throughout.
    Certainly more consistent than our ability to measure in the shop.

    Accuracy is fine but accuracy beyond what we can measure is of little value.

    When we have elections and the margin of error of the tabulation method is +/- .5%
    An the difference between winner and loser is les than .5% you have a tie and some more accurate method of counting must be employed to count the results or you still have a tie.

    Al
     
  7. Mark Hepburn

    Mark Hepburn

    Joined:
    Mar 26, 2014
    Messages:
    1,170
    Location:
    Houma, Louisiana
    Al,

    That's indeed true. Having precision to the nth degree is great but may not be necessary. Dry Poplar is really consistent stuff. Should work great I would think.


    Mark
     
  8. Mark Mandell

    Mark Mandell

    Joined:
    Apr 25, 2004
    Messages:
    2,542
    Location:
    New Jersey
    Consistency

    I may be wrong, however it seems to me that if the same sample is used for each test the results should be valid "enough" for woodturners. In that situation gluing up a layered cylinder blank of MDF, say 24" by 12" in diameter, could work. Then, rather than trying to determine "dullness" by some subjective criteria, mount the sample tools and run them each across the 24" length a set amount of times. Then take your new pix and do the comparison of the wear on each tool's edge. This should remove the issue of variability in the material because the exact same material would be used for each run on each tool. If the MDF went from hard to soft to hard it would make no difference since each tool would be subjected to the same changes in the same order. If the goal is to show woodturners how long their tool will stay sharp, you'd have to confront the staggering variables of the whole spectrum of woods being turned multiplied by the even wider spectrum of turning styles and methods. That would seem to me to be an insurmountable amount of uncontrolled conditions. Conversely, after 2, 3, or 4 runs across the 24" of MDF, microscopic examination of the remaining edges should give you the ability to predict, with a reasonably high degree of probability, how long a given cutting edge would last in use. I suppose you could hone down the predictability further by photographing the edges after each run so as to get a progression of wear. In the final analysis, it doesn't take micrographs to tell a turner that his edges, regardless of their alloy, will stay sharper longer when cutting Pine than when cutting Lignum Vitae or Mesquite.

    Of course, as stated, I could be wrong
     
    Last edited: Jul 29, 2014
  9. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
    4,306
    Location:
    Lakeland, Florida
    Home Page:
    I would want to see the results of the cut on the wood.
    1st pass, 5th pass, 10th pass.

    The views of the tool edge and the views of the wood surface are both important.

    MDF does not have endgrain.
    The back side of the end grain on a face grain turning is the spot to compare this where tear out will be the most.

    Al
     
  10. john lucas

    john lucas

    Joined:
    Apr 26, 2004
    Messages:
    5,823
    Location:
    Cookeville TN USA
    Mark That was my thought except that I think I need 3 pieces because I would like the surface feet to be the same. If I make 10 passes each on one cylinder the cylinder of course will get smaller so the last tool won't cut as much wood. I'm thinking 3 -12" pieces cut from the same piece of wood or MDF so the grain or structure would be as close to the same as possible. I would remove the same amount of wood from each piece so each tool should get as close as I can the same wear. Then I will look at them through the microscope to try and judge wear if possible realizing that this experiment doesn't follow real scientific guidelines. Hey I'm just a redneck having fun and what redneck doesn't like to sharpen steel.
    Here is a photo of the 3 tools I've made. The top one is Thompson V11 steel. The middle is Henry Taylor High speed steel and the bottom one is High Carbon steel heat treated to 60Rockwell which is approximately what the other 2 tools are. All 3 are ground to 28 degrees ( missed 25 degrees by That Much but wasn't going to grind anymore). Sharpened to 1500 grit and then stropped. They are about as sharp an any tool in my arsenal including my handplanes and carving tools. All 3 seem to be the same sharpeness and definitely sharpen than turning tools, even my skews aren't usually this sharp. So for all practical purposes I've accomplished my goal which was to prove that Particle metal and HSS could be sharpened to the same degree as High Carbon steel. Hopefully the microscopic views will tell me something.
     

    Attached Files:

  11. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
    Jan 27, 2005
    Messages:
    8,125
    Location:
    Dalworthington Gardens, TX
    Home Page:
    John, the way that you have your test constructed, you might as well poke it against a grinding wheel and measure how fast the tool and wheel mutually abraded away. The problem with the power feeder is that it is an absolute positioning device without regard to force. This means that there will be uncertainty about validity regarding the meaning of wear measurements because the data can't be correlated to the way that tools are used by woodturners. Now, OTOH if you constructed a constant force feeder (as opposed to a position feeder) using a long spring, then I think that you would have a better chance of measuring wear resistance by measuring the amount of wear over a fixed length of time.

    I would recommend that you talk to Jerry (steelguy) who retired from Crucible Industries as well as Doug Thompson. I think that Doug can tell you how to contact Jerry or perhaps an engineer at Crucible. Jerry hasn't posted on this forum in about three years.
     
  12. Mark Mandell

    Mark Mandell

    Joined:
    Apr 25, 2004
    Messages:
    2,542
    Location:
    New Jersey
    Agreed Al, but I thought John's test is for durability of the equalized edges rather that how well and how long a 1500 grit edge will cut without torn grain. Once you put the tool in a turner's hands the control factors go in all directions. An advanced turner like you can turn without torn grain far better than someone on my level, not to mention a novice student, because of your superior technique. Consequently, you'll get more performance for a longer time out of the same tool than I or others will. That's close to impracticable a test.
     
  13. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
    4,306
    Location:
    Lakeland, Florida
    Home Page:
    Holding the tool in something like a Jamieson handle will keep the tool presentation consistent.
    The metal lathe would do much the same. This will work for scraping tests.
    I suspect using the tool as a scraper will have different wear than using the tool for cutting.
    Without a bur the scraping will be inefficient.

    These tools will do peeling cuts on spindles
    The Endgrain exposed by the peeling cut will show how the corner of the tool dulls.

    I think john could do the peeling cuts with a lot of consistency.

    Use 3" diameter blanks. Say 10" long. Part in every 1" for tailstock to headstock to 1" diameter
    Use the peeling cut to 1" on the right side of each section.

    Al
     
  14. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
    Jan 27, 2005
    Messages:
    8,125
    Location:
    Dalworthington Gardens, TX
    Home Page:
    No, that's not it at all. The power feeder holds constant position regardless of how much or how little force is needed. That introduces an uncontrolled variable into the test that corrupts the results. The constant force device that I mentioned previously would give much more meaningful results. I probably need to figure out a way to better explain this to people who aren't engineers because it is obvious that my message isn't getting through.
     
  15. john lucas

    john lucas

    Joined:
    Apr 26, 2004
    Messages:
    5,823
    Location:
    Cookeville TN USA
    Al I was going to tilt the tool in the cross feed vice so that it matches the angle I would use if I used the skew. Not going to do a scraping test. I want it to cut just like I would.
     
  16. john lucas

    john lucas

    Joined:
    Apr 26, 2004
    Messages:
    5,823
    Location:
    Cookeville TN USA
    Bill I'd like to rig up a device that pulls the tool with a weight instead of power feed but that's just getting way to complicated. Still I have plenty of time to think about it and may come up with something. If you did it with a weight on a slop you could measure the time it takes for each pass and plot it. When the tool gets dull I assume it would take longer to traverse the same length.
     
  17. hockenbery

    hockenbery AAW Advisor Staff Member

    Joined:
    Apr 27, 2004
    Messages:
    4,306
    Location:
    Lakeland, Florida
    Home Page:
    I am intrigued. A fundamentals article in the making?

    Matching the skew angle should work if you can match the bevel. I'm not sure how hard this is to do.
    I know you will figure out a safe way to do it.

    If you can have bevel on the wood not cutting and adjust the angle it may not be that hard Be sure to err on the cutting edge coming out of the wood.
    If the tool can bury itself you will stall the lathe or get one awful catch that break something.

    One thought is doing cutting run with straight grain might take a couple of spindles to get all the tools dull.

    If you have some time left maybe do another set with the wood cut on the bias maybe 20 degrees off straight.
    This should yield tearout on the side where you are lifting the grain as the tools get dull.
     
    Last edited: Jul 29, 2014
  18. Bill Boehme

    Bill Boehme Administrator Staff Member

    Joined:
    Jan 27, 2005
    Messages:
    8,125
    Location:
    Dalworthington Gardens, TX
    Home Page:
    If you could find a long spring like an old screen door spring instead of using a weight, I think that would work better and you could control the amount of force by how far you stretch it. Use a very long handle for the tool that is hinged at the back to a solid surface to keep the contact angle fairly constant. If you use a large diameter piece of wood or MDF, that would also help to keep the angle close to constant. If you could find a large dry hard maple log, you could cut all of your test pieces from the same log and have better assurance of uniform characteristics.

    I think that you might try running each test for a certain number of seconds ... determined by experiment and then check edge wear and/or photograph it. I also think that checking with some industry experts like Doug Thompson for their thoughts would be a good idea.
     
  19. Jeff Gilfor

    Jeff Gilfor

    Joined:
    Nov 1, 2012
    Messages:
    115
    Location:
    Tampa, FL
    This is an interesting concept you guys have. But...

    There is no objective measurement of dullness. That is a very subjective thing. Perhaps we could measure the actual force required to get an acceptable tool finish; but then again, that in and of itself is subjective.

    Alternatively, we could see how long it takes to fatten the cutting edge by some measure, let's say 10%, for instance, under the assumption that it is the broadening of the sharp edge that results in dullness. That would allow comparisons between metal type and sharpening methods, as long as the presentation, wood, and force applied is the same for all tests. Only problem here is that I do not have a ruler that shows micrometers, therefore have no way to do the measuring.

    This would be an awesome study if we could figure it out. Don't think anyone has ever done anything like this.
     
    Last edited: Jul 30, 2014
  20. Mark Hepburn

    Mark Hepburn

    Joined:
    Mar 26, 2014
    Messages:
    1,170
    Location:
    Houma, Louisiana
    Jeff,

    I'm not the technical guy here at all, but this sounds like it might be a a good idea. If you know how long you have had the tool against the material and the RPM, then you could you not calculate the distance the tool edge travels until it had broadened by your predetermined rate?
     

Share This Page