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  1. #1
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    Default Bench Sander Blade Grinder MK II

    Part 1 (of 3)

    I have replaced my Belt Sander Grinder with Mark II. This not only involves a new jig, but also a new machine.

    The original machine developed electrical problems (in the on-off switch) and, after one unsuccessful repair, I accepted Carba-tecs offer to return it (at full refund) and upgrade the machine (my cost). Its replacement is the Carba-tec SB-609, a 6”x9” machine. Compared to its predecessor, it is bigger and more powerful. Note that this is not necessary for the purposes of grinding/sharpening blades, as the original machine was satisfactorally specified in spite of being 1/3 hp and 4” wide.

    Carba-tec describe the SB-609 as follows: New model features graphite slip pad and dust extraction outlet. Powerful 3/4 hp motor will not stall under pressure. Disc table tilts to 45 degrees. Belt platen swivels for horizontal or vertical sanding. Quick-release lever makes for fast belt changing. Stand and mitre guide included.

    I needed to fit a jig to the new machine and, although I could modify the old one to fit, I thought that I'd make a new one – one that included all the features I had previously described in the earlier article.

    For original jig see picture below, or go to http://www.woodworkforums.ubeaut.com...8&page=1&pp=15

    The other area I was interested in sharing was my efforts in machining metal, in this case aluminium, with the few related metal working tools I own. If I can do it, then others can too!

    Below is a picture of my Poor Man’s Metal Machining setup: drill press, 2-dimension vise, drill bits, cheap set of taps and dyes, squares, scribe, digital caliper.

    It begins here …

    The first step was to cut up a few pieces of aluminium. I did this on a Mitre Saw (cheap GMC) (picture #4), then ground them square on the belt sander (picture #5).

    (continued in Part 2) ...
    Last edited by derekcohen; 4th Apr 2005 at 02:42 AM.

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  3. #2
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    Default

    Part 2 (of 3)

    The plan for the jig was to modify the design by adding height adjustability to the toolrest, a feature which many contributors have believed important. I agree – height adjustability is not so much a factor for setting the blade as it is for setting the tool rest perfectly parallel to the table top. My earlier suggestion had been to drill completely through the tool rest sideblocks, and to add a height adjustment screw from underneath the block.

    Drilling the blocks accurately is made possible with a drill press and vise. Make sure than you lubricate the drill bit otherwise it will overheat and snap (don’t ask me how I know!). Below is a picture of the underside of the drilled block, revealing that I got it right!

    Height adjustment screw: Drill a pilot hole all the way through the block. Mine was 28 mm thick. Then drill from the underside 8 mm deep for a thread you will later tap for an allen head bolt. From the other (top) side drill a 20 mm deep hole for the toolrest legs (mine are 9.64 mm in diameter, so I used a 10 mm drill bit).

    Tap the height adjustment holes for the allen head bolt.

    In the next picture (below) you can see these holes more clearly.

    Finally, drill the two holes that will fix the new toolrest block to the side of the belt sander, and then drill to recess the bolts (also allen head bolts). This completes the toolrest blocks. See picture below.

    (part 3 follows) ....
    Last edited by derekcohen; 4th Apr 2005 at 02:45 AM.

  4. #3
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    The Finale - Part 3 (of 3)

    Here is the pic of the final set up.

    Note that the belt sander table top was stripped of the graphite slip that comes as standard equipment. This tends to be easily depressed when pressure is placed in one spot. The underlying cast iron top was flat and smooth. Nevertheless, to avoid any later problems with wear, I contact glued a steel plate to the table. This was cut from an old hand saw blade (cut with angle grinder, smoothed with files).

    The blocks were screwed onto the sides of the sander by drilling and tapping holes. The set up process is the same as previously described (in the first article). Care was taken to make sure that the toolrest was square to the table top.

    Steel washers were used as spacers to center the jig.

    The height of the tool rest was set using a piece of 6mm MDF (reliable flat measurement) under it. The height adjustment screws were locked in place with additional nuts. All done.


    Regards from Perth

    Derek

  5. #4
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    Great to see you continue to develop this Jig Derek

    <!--StartFragment -->

    Keep us posted on how she goes whilst you break her in

    REgards Lou
    Just Do The Best You Can With What You HAve At The Time

  6. #5
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    Heaven forbid if you get a book on metal casting for Christmas!!

    I reckon that's the next step of course, a cast pair of brackets!!

    I too look forward to the evolution, but will stick with the unfinished wooded variety for a while, the unfinished metal one can wait!

    Cheers,

    P

  7. #6
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    Hi Derek

    The improved design of the tool rest and a shift to cast iron should help considerably with accuracy and repeatability. I'm not sure you needed to glue the saw blade on the platten as I don't think there will be much wear unless abrasive gets under the belt. This limits the use of the belt sander by reducing the table surface but if it is a dedicated sharpener it is a worthwhile addition.

    Are you able to get the finer grades for the 6 inch belt?

    No doubt about it you have developed a top sharpening system.
    Cheers,
    Rod

  8. #7
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    Rod

    I think you're right, there is probably no need for the steel plate as the cast iron is flat enough. I have removed it and so far so good (and, as you pointed out, it increases my tool options).

    I managed to get a few belts from Carba-tec: 80, 120, 240 grit. Then from Abraflex (232 Collier Rd, Bayswater. Telephone 9370 3455, ask for Alan), I have on order: 240, 400, 600, and 1300 (!!). This is going to be interesting since, with 600 and then honing on Veritas green rouge, I would get a near scratch free mirror surface on chisels (not quite good enough for plane blades), that was sharp enough to cut anything. I wonder what the 1300 will do (that is equivalent to about a 4000 waterstone. Add to that the Veritas rouge ...)??!!!

    Regards

    Derek

  9. #8
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    Derek
    Even at 600 all of the hard work is done so 1300 will be a bonus. Given the lenght of the belts you should get plenty of use before they dull.
    From memory I pay about $14 for the belts from Carbatec so how do the Abraflex belts in the fine grits price out?
    Cheers,
    Rod

  10. #9
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    Rod

    The belts do last a long time. In fact, the first set of belts outlasted the original machine! (i.e. 2 months old and still going strong after sharpening everything in sight).

    The belts from Abraflex work out to about 2/3 the cost of those from Carba-tec. You do have to buy a minimum of two (in the same grit), however.

    I have just had to lay out for the belts for the larger, new machine and this was not cheap! Still, they should last at least double as long as that of the smaller machine. The 240 and 400 were about $8 each, the 600 about $11 each, and the 1300 about $27 each.

    There is no doubt that using waterstones is still the cheapest option in the long term. Sandpaper sharpening is expensive by comparison. Using poor sandpaper is even more expensive, as good sandpaper will last significantly longer. The belt sander is all about convenience, not ultimate cost savings. Compared to wet-and-dry, belts are relatively inexpensive when their durability (not to mention their speed) is taken into account.

    Regards from Perth

    Derek

  11. #10
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    Derek,
    The belts are well priced and as you say the convenience and speed is a factor. Who knows I might even join the dark side one day yet.
    Cheers,
    Rod

  12. #11
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    Derek,

    Your improved version on the upgraded sander looks excellent; I am still stuck with my el cheapo sander on which the pressed steel bed has warped badly, so I had to adopt Major's solution of glueing on a glass plate. I cut a piece of 3 mm glass, bevelled the edges and glued it down with contact cement, which seems to work satisfactorily. To compensate for the thickness of the glass, I had to raise the crossbar, which I did by adding washers, and countersinking the undersides of the wooden support blocks, so that the bolts could accommodate the washers.

    I am happy just to grind the main bevel in the sander, and leave the honing of the micro-bevel to be done by hand on a diamond plate. It doesn't seem to me to be worthwhile to mechanize the whole process, since the honing of the micro-bevel takes only a few minutes anyway.

    Rocker

  13. #12
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    Rocker wrote:

    the pressed steel bed has warped badly
    Yes, as you recall mine did as well. I did not have a piece of glass handy and so used an old diamond stone steel backing plate. This worked very well.

    I am thinking about others who may be concerned that their belt sander also need to be modified (probably if it is made out of thinnish steel - which is one reason I upgraded the machine to thick cast iron) and that this will require a rebuilding of the tool rest jig. There is actually no need to modify the height of the tool rest. Adding a plate to the belt sander table will alter its height, but this can be corrected by changing the blade setting jig. That is, alter the amount of blade projection required for a specific bevel angle.

    I am in the process of designing a new setting jig, and will post it here when it is done.

    In summary, the original (inexpensive) belt sander is absolutely fine as a machine to base the grinding jig. I would add a piece of glass or steel at the beginning as part of the construction, rather than wait to do so at a later date.

    Regards from Perth

    Derek

  14. #13
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    Quote Originally Posted by rodm
    Derek
    Even at 600 all of the hard work is done so 1300 will be a bonus. Given the lenght of the belts you should get plenty of use before they dull.
    From memory I pay about $14 for the belts from Carbatec so how do the Abraflex belts in the fine grits price out?

    Rod -

    If you have repeatable geometry - you ultimately spend less time on any abrasive medium - making it last longer... an often overlooked component of sharpening.

    I use a belt sander as well (i have a 1 x 42, and a 1 x 30 (on a Veritas Mk I power sharpener)) - and belt wear has not been an issue yet...

    Any shaping work I do on a wheel though.

    Cheers -

    Rob

  15. #14
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    Default Setting up and using the Belt Sander Grinder

    Here is a manual (of sorts) for setting up and using the Belt Sander Grinder. It was developed using Mk II but is equally applicable to Mk I.

    Figure 1: Belt Sander Grinder Mk II

    Figure 2: Toolrest Setting Jig – loosen height adjusters and slide in the toolrest. Tighten. Use feeler gauge to check that it is set equally on both sides.

    Figure 3: Bevel Angle Setting Blocks – these were cut to the three common angles I use, 20°, 25° and 30°.

    Figure 4: The bevel angle setting blocks are placed behind the blade with the blade holder pushed up against the toolrest. Note that this must be done on the belt that is used last in the grinding sequence. In this case it is the 1300 grit belt. Once determines, tighten the hold downs on the blade holder.

    Figure 5: Bevel Angle Setting Jig (BASJ)

    Figure 6: Transfer the blade holder to the bevel angle setting jig. Make sure the blade is square against the side fence. Redo the previous step until both the bevel angle and a square blade is achieved. If the bevel end of the blade is out-of-square, judge where the bevel would end if it were square, and use this mark as the repeated setting.

    For the first grind, set the blade against the front fence of the BASJ, grind the blade square, then set it again. Grind only enough that you can feel the wire edge beginning. Then move to the next belt. If you do choose to regrind the full bevel, you will need to reset the blade against the BASJ. Do this again for the last belt as well. In most cases, running through 5 or 6 belts and grinding full bevels will remove about 1mm of the blade length. For plane blades it is expected that you will move at this point to waterstones (or another low-micron grade medium) and grind a microbevel with the use of a sharpening guide, such as the Veritas or Eclipse. The Veritas has the advantage of an in-built adjustment for a 2° microbevel. The Eclipse needs to be adjusted by reducing the length of the blade’s extension (the BASJ is useful here). Chisel blades may just be stropped on the Honing Plate, and this may be sufficient for most tasks.

    Regards from Perth

    Derek

  16. #15
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    thats a pretty complete system you have there derek... Sure beats my initial approach, that is trying to sharpen a blade on a belt sander held upside down by a workmate!

    Well done.
    You can never have enough planes, that is why Mr Stanley invented the 1/2s

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