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Thread: Problem removing knife bolts on old Delta 6" Jointer Model 37-190

  1. #1
    Join Date
    Nov 2012
    Location
    Lombard, IL
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    102

    Problem removing knife bolts on old Delta 6" Jointer Model 37-190

    Hi all,

    I have an older Delta 6" jointer model 37-190 which I've been trying to change the knife blades on (first time doing so). I penetrating oil on the knife bolts but 4 of the screw heads are starting to strip with the 5/16" open end wrench I've been using. I first tried using an 8mm wrench but that wrench did stripped as well. I have loosened 8 of the 12 bolts but these last 4 have heads which are rounding over.

    Besides the penetrating oil, I've also heated the bolts with a commercial heating gun, to no avail. i also filed a small grove in one of my 5/16" wrenches to help it to fit the hex head bolts easier, but that did not help.

    Looking for any suggestions here to help. Pictures below of specifics

    thank you,

    'mark

    IMG_8112.jpgIMG_8113.jpgIMG_8111.jpg

  2. #2
    Join Date
    Feb 2014
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    Lake Gaston, Henrico, NC
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    9,354
    My first try would be a better quality wrench.

  3. #3
    PB Blaster penetrating oil works better than others I have tried. An electric heat gun isn't as effective as a torch. If you use a torch don't over heat. I have carefully whacked a sloppy wrench with a big cross peen hammer to tighten it up a bit. If and when you get them out replace the hex bolts with square head bolts. I have an old Delta 4 inch, it has square head bolts as does my Powermatic and all of the other jointers I have ever worked on.
    Last edited by Maurice Mcmurry; 06-21-2024 at 6:56 PM.

  4. #4
    I buy undersize wrench and grind them out till they fit snug. Too often the supplied stuff has play in it.

  5. #5
    Join Date
    Nov 2012
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    Lombard, IL
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    Thanks Maurice, thatís exactly what I am using. Unfortunately the smell of it in the basement makes my wife sick.

  6. #6
    Join Date
    Feb 2003
    Location
    McKinney, TX
    Posts
    2,088
    Another excellent penetrating oil is Kroil. Best I’ve found. Amazon has it.
    Steve Jenkins, McKinney, TX. 469 742-9694
    Always use the word "impossible" with extreme caution

  7. #7
    Quote Originally Posted by mark ahlenius View Post
    Thanks Maurice, that’s exactly what I am using. Unfortunately the smell of it in the basement makes my wife sick.
    It is very stinky! I see some you tubers set it on fire. I wonder if that does anything more than increase the stink? I think the hex bolts are the problem.

  8. #8
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
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    10,310
    Buy a better wrench. If you can not find a service wrench a tappet wrench should work. Or grind down a too thick wrench.
    I do not know what that wrench looked like before but it is now damaging the bolt heads. Stop before you make it worse and impossible to remove the bolt heads except by grinding.
    Bill D

  9. #9
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
    Posts
    10,310
    Unless it was made in Brazil an old delta jointer will use USA size bolts.

  10. #10
    It's been several years since I had to do this and I might be wrong but try loosening in the opposite direction. Something makes me think it was backwards from tightening and loosening a regular bolt.

  11. #11
    Quote Originally Posted by Joe Delfino View Post
    It's been several years since I had to do this and I might be wrong but try loosening in the opposite direction. Something makes me think it was backwards from tightening and loosening a regular bolt.
    Good point. It is tighten to loosen with jointer knives. OP has gotten a few out so I assume he has stood on his head while looking at a clock like I always have to do to figure out which way to turn. My dyslexia is getting worse. I am starting to mix up W and M.

  12. #12
    Join Date
    Nov 2012
    Location
    Lombard, IL
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    102
    Quote Originally Posted by Joe Delfino View Post
    It's been several years since I had to do this and I might be wrong but try loosening in the opposite direction. Something makes me think it was backwards from tightening and loosening a regular bolt.
    Hi, thanks for the reply Joe. I know I am turning the correct direction because the other 2 bolts loosened up that way on the blade. At first I was not sure because the instructions say to turn it clockwise, but they did not mention which direction you are looking at the bolt from. So i found a video and copied that direction and it was correct.

    thanks

    'mark

  13. #13
    Join Date
    Feb 2003
    Location
    Granby, Connecticut - on the Mass border
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    I used to have that jointer and had the same problem. If you can take the pressure off the screws, you might be able to turn them then. Find a flat piece of metal that fits very tightly into the slot where the screws are, tap it in, (so that it, not the screws, are pushing against the knife) and it'll take the pressure off the screws and let you turn them. Yes, I'd stripped a couple heads while I figured this out. I used a piece of metal that I had laying around the shop that just happened to be the right size, but ideally you'd like something just a bit tapered, I suppose. Good luck.

    Ken in North Granby, CT

  14. #14
    Start with a decent wrench and grind it thinner to fit.

  15. #15
    Join Date
    Nov 2009
    Location
    Peoria, IL
    Posts
    4,733
    Start tapping near a corner of the bolt with a pin punch in the direction of loosening. The impact cab often loosen them up.

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