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Check Your Angles! - How To Kill An Afternoon

Discussion in 'Working the Steel' started by ToddR, Dec 2, 2016.

  1. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    Sorry for the long post, I need to rant a bit to people who get it. I have learned a really valuable lesson today. I had a rare day off and decided I'd finally spend a whole day in the shop doing nothing but cutting and grinding something. I have this sweet new grinder I made and have ground out two blanks so far. This was going to be awesome. I cut out a little blank, something like a little camp knife I suppose. I calculated my angle and cut a jig from a 2x4 (that's how i do it, i use an app to calculate my bevel and a digital angle finder to set the table saw) and I was thrilled to be out there. Only, i couldn't get my plunge lines on my bevel to line up. They were both straight as an arrow only they were off by at least 1/4. I tried to free hand it to staighten them up and that was.. a mistake. A few slips later and i had a nice piece of tool steel scrap. So, being me, i tried the same thing again on another blank. (after cutting and grinding it out ).

    I know what you're thinking... why would he think it would behave differently this time? Well, I have no excuse other than I was so excited to have a day to myself in the shop that i really wasn't thinking that far ahead. Just as you suspected, same thing happened. By know i've killed the afternoon and I have a big problem on my hands. In the few weeks since i've been out in the shop, I forgot how to grind! I was no expert but the other knives i ground looked decent. I made a promise to make a knife for our family gift steal and I had an operator or a grinder issue, and i didn't know which.

    Then my wife comes in on her way out to go shopping and says "hey, that flat rest thingy looks crooked". So i look and sure enough, it's not square to the platen. It's much higher on the right side. I built the grinder so the tool rest slides into a bigger piece of square stock and then locks with a thumbscrew. Theres a little bump in one side of the square stock that won't allow it to nest perfectly flat in the bigger piece. I guess that if i tighten it just enough to snug it up, it's square. If i tighten it up until it won't turn anymore i twists the tool rest arm and the right side is a lot higher. So my plunges stay straight only they angle in opposite directions when you flip it to the other side.

    Sigh... figure it out and i can work around it but, another fix on my growing list of grinder bugs. Though I prefer to call them "undocumented features". Moral of the story, like I do with my most of my other tools, i guess never trust that the machine is set up as you think. ALways throw a square or a ruler or whatever on it and check. That cost me a good piece of tool steel, most of a new ceramic belt and my whole afternoon off. Expensive way to find an undocumented feature.

    Thanks for listening guys...
     
  2. dancom

    dancom Dust Maker Best Shop Tool

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    Yes, I hear you. I cut a whole bunch of expensive oak veneered 3/4" plywood and after making a bunch of cuts I realized something didn't look right. The blade was off square by about 5°. The crank dial on the table saw said 90. All the joints were impossible bad. After that lesson I check the blade for square with a machinist's square before cutting anything. Never assume it's where it was the last time you used it.

    Live and learn,

    Dan
     
  3. SDMay

    SDMay Active Member

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    Been there done that !! I got lucky though as I am trying to teach myself to grind freehand but one of my blanks became a little smaller and a little different shaped then when I started. I noticed something looked off and when I checked my flats with a square the spine was out. Ran the square all around and noticed the same thing. The set screw that you can use to set your table angle on my 1 x 30 was wonky so I had to square it up and run the blank through again. Now the first thing I do when I put the sander on the table is to check the square and I check it every once in a while just to make sure.

    Sorry your afternoon didn't go as planned. That's no fun!!
     
  4. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    The only thing that really bugs me is the loss of the time. I hate having zilch after an afternoon of work.
     
  5. John Noon

    John Noon Well-Known Member

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    For the grinders I would go with the mechanical tubing used on trailer hitches the fit is better and the big nasty seem is not a issue. Of course I pulled a similar bone head move that took a few months to finally figure out.

    For starters I made a blade holder out of two pieces of angle iron which makes swapping sides fast and easy when grinding. Now for the most part the blade was shaped to 320 grit then heat treated an the odd time the angle seemed off when back in the holder. Figured it was the large tool rest which I removed then thought a spacer would prevent the angles from sitting crooked which worked for the most part.

    Still ran into issues with aligning the platen and bevel so started doing it manually and avoid the whole angle finder routine. Still ran into problems if taken out of holder and put back in and last week was about to throw grinder and all into the dump out of frustration. This day and age repeatability should not be such a difficult thing.

    So Sunday I am grinding on the flats after using a square to set the platen and the grinder was hitting on a angle, said a few choice words and took the holder apart. Well more kind words and look at that both angles are off 90 degrees so get grinder all nice and square and go to town on the angles and if you have ever tried that with structural steel you know how much crap moves as you remove material and change the residual stress inherent in rolled shapes.

    It took a while but I managed to sneak up on 90 degrees and have something that is for the most part a reusable tool. Oh I was pretty sure I did this last year when I first put it together so it is a bit of a head scratcher but I will be keeping an eye on it for some time just to be sure no more problems sneak up on me.
     

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