Wednesday, October 3, 2012

Belt Sander Saga Continues





Sample, Un-Stropped Chisel Cuts

     Well, after fiddling around with the belt sander set up, experimenting on my carpenter work flat chisels, the picture above shows two sample cuts from a couple of gouges.  These cuts are right off of the belt sander and not too bad of quality.  Basswood is the wood and the cut is across the grain.
     I've seen some comments about this series of blogposts I'm doing and most of them are positive.  My goal in all of this is to change the cutting angle of my gouges so they suit my particular style of carving better -- everything is evolving!  Since reading through Leonard Lee's book on sharpening yet again it seemed to me that he really felt the belt sander is an underused tool for sharpening and rates it highly.  From Lee Valley I picked up their 120 grit Blue Zirconia sharpening belt and give that two thumbs up. I also got their 15 micro silicon carbide and have some mixed emotions about that but will get into that later in this blog.
     The first issue I addressed was the one about getting the rotation of the belt to go the other way.  Makes sense that you wouldn't want your edge slammed against the tool rest while you're trying to hone it.  Here's a LINK to that blog if you need it.  I came up with what I think is a pretty effective way to maintain the needed angles on the chisels.  For my carving work I'm using 20 degrees.  Just to clarify, for my bench chisels and planes I use hand held guides and stones only.  I'm not a fan of hollow grinding.  Saying that though, the first bunch of experiments I did with this set up was on the Stanley butt chisels I bought back in the early 70's and used during my carpenter years.
     Okay, let's get started.  The picture below shows how easy it is to swap out the belts on my set up.  There is plenty of clearance on the side to get your hands into, the only slight hassle is pulling up on the tension knob but really not bad of a chore.

Plenty of Clearance for Belt Changes

     I improved the tool rest, I think!  It's an aid which will allow you to sharpen a tool that's wider than the belt.  It's simply a fence that hooks over the tool rest.  To make things easier to move during cutting, the guide and the tool rest have been waxed.  By holding the tool against it you can now move it from side to side to grind the entire edge.  For tools less than an inch wide clamp the tool rest so it's stationary.
This View is looking from the back of the machine so it's easier to see. 

Detail of Rest --- Viewed from Back

     In practice there are a couple of things to consider.  First of all be prepared that the tool you're grinding will want to pull away from the rest so hold it securely.  The belt moves pretty quickly and things will heat up so just "kiss" the tool to it and then pull back.  The amount of sparks you get will be a good indication of how heavy or light your cut is -- you want to work slowly and make multiple, light passes cooling the tool in some water as needed.

Actual Cut in Progress

     Like I said, I'm using some carpentry chisels to get a feel for this process and they were in dire need of some reshaping.  Funny how nails and ceramic tile screw up their edges!  I'm one to use a sharpie on the edge to check the progress of my sharpening.  Here is one of them after a few passes:


1 1/2" Butt Chisel
     
     After carefully guiding each of these into the belt I checked them both for square and to see how the cutting angle was coming along.  For utility use bench chisels I use an angle of 25 degrees. 

25 Degrees and ........
......... Square

     Next up was using the 15 Micron belt to hone and remove the scratch pattern put in by the 120 grit.  The first use for this was on a small size chisel and boy, did it ever heat up fast!  I remembered seeing in Lee's book that he honed a knife blade near the top of the machine where the belt ran free.  I double checked the instructions that came with the machine and it said this piece of angle iron that's under the belt should always be touching unless you're polishing.  There's my aha moment, there are two allen screws that hold the angle iron in place.

Angle Iron NOT Touching Belt
 
     This made all of the difference, the heat didn't build up as before.  This is how the bench chisels looked after honing on the belt.  A bit of work with water stones and a guide and they'll cut like butter.

Carpentry Chisels Re-ground, Honed, & Ready for Final Hand Work
 
     So the practice work is now complete so it's time to experiment with some carving gouges.  I changed the tool rest supports to the 20 degree set.  The chisels I practiced with are some of the plastic, blue handled Marples that although they're good tools I just don't care for the feel of the plastic handle.  Matter of fact, now that they're sharp I've put them on ebay (See one here).  First up was to re-establish the 20 degree angle.  Same technique as with the bench chisel but rather than having to move the tool rest I clamped it down and used it as a guide while rotating the edge on the belt.  I re-adjusted the angle iron so it was close to the belt (1.5mm or so) and began with the 120 grit belt again.

Initial Re-grind with 120 Grit

     In the picture I've almost finished it, there's still some of the old edge on the corners.  Keep in mind that the goal of this operation is to grind to new metal, you can tell you've achieved it when there's a uniform burr on the inside.  The next phase was to switch over to the 15 micron belt, lower the piece of angle iron and hone them.  Here's how I guided them for this process.

Honing Stance
      The edge of the gouge is against the rest, my fingers are supporting it loosely, and my other hand is rotating the gouge against the belt.  If you go back to the picture at the top of this post, that's the cut after this.  The only thing I did was to remove the burr with a slipstone.
     Well, truthfully I'm pretty pleased with this  whole process.  My goal was to find a way to either re-configure the cutting angle of my carving tools and/or refresh the edge as needed.  I've discovered that honing will tend to round that edge which gradually changes the action of the cut.  I'm really a novice carver and have spent most of my years building furniture types of projects.  I'd be interested in getting feedback from any of you that may go ahead and give this a go.  If my blogging has helped you with your work so much the better --- John

6 comments:

  1. Are you grinding on the platen ?

    But not using it when you polish ?

    Any problems with fatigue from having to reach forward to contact the platen ?

    Any safety problems from necktie-like appurtenances ?

    ReplyDelete
    Replies
    1. Yes, grinding on the platen but not with polishing, seems as if it heated up really fast! Experimented with putting a piece of leather (2 sided tape) on platen for belt to ride on during polishing which was okay but free hand seems to work well too.
      No safety or fatigue issues, I'm directly in line with the machine and working over the top.

      Delete
  2. Consider these possible changes for workplace safety considerations:

    I refer you to the photo labelled "Honing Stance".

    1. make your box deeper so that the pulley attached to the arm of the sander isn't exposed.

    2. make the "V" cuts on each side board less acute (more shallow).

    ReplyDelete
    Replies
    1. Since the belt is covered (yes I always replace it) no problem but should I ever need to grind/sand a concave surface it is still accessible.

      Delete
    2. A slot in a deepened box would also work for concave sharpening and protect you AND your students. Remember what can go wrong will go wrong !

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  3. A belt sander is a tool that makes the job of sanding down pieces of wood a breeze. It has a sanding disc attached tightly to its rotary belt, where it rotates at a rapid pace in order to make quick work of rough surfaces and edges on wooden constructs.

    ReplyDelete