1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

I have an old (70's) Mama Bear. The bolts to the draft knobs are bent. How can I replace these bolts

Post in 'Fisher Stove Information, Parts, History and More' started by archibald, Mar 6, 2014.

  1. archibald

    archibald New Member

    Joined:
    Mar 6, 2014
    Messages:
    3
    Loc:
    asheville, NC
    I have an old Mama Bear stove. The bolts to the draft knobs are bent and the caps will not close tightly. How do I replace these bolts? They seem to be welded to the two caps.

    Helpful Sponsor Ads!





  2. pen

    pen There are some who call me...mod. Staff Member

    Joined:
    Aug 2, 2007
    Messages:
    7,088
    Loc:
    N.E. Penna
  3. coaly

    coaly Fisher Moderator Staff Member

    Joined:
    Dec 22, 2007
    Messages:
    1,545
    Loc:
    NE PA
    If the bolts are welded to the caps, (the caps unscrew from the door and come off in your hand) they are malleable iron pipe caps with a 1/2" bolt "plug" welded to the pipe cap. The bolt rotates in the door and will not have a nut inside.

    Fisher Original Draft cap.JPG Original Fisher Draft Cap.JPG

    If it's a newer stove, the draft cap will have fins and is not welded to the bolt. The bolt is threaded into the door and double nutted to the door. The bolt doesn't move, and the cap threads back and forth on the bolt. The outer nut should be a half nut, so reuse it. Some bolts with the later caps that are double nutted to the door were tack welded inside to prevent from turning.

    Draft Caps 18 resized.JPG

    Which type do you have?
  4. archibald

    archibald New Member

    Joined:
    Mar 6, 2014
    Messages:
    3
    Loc:
    asheville, NC
  5. archibald

    archibald New Member

    Joined:
    Mar 6, 2014
    Messages:
    3
    Loc:
    asheville, NC
    I must have a newer stove. My caps (2) have four fins, of cast aluminum. The bolt appears to be spot welded into the cap. I cannot budge it. It was easy to remove the caps from the stove, from the inside, but I cannot see a way to separate the bolt from the cap in order to replace it. Can these caps be replaced?
  6. coaly

    coaly Fisher Moderator Staff Member

    Joined:
    Dec 22, 2007
    Messages:
    1,545
    Loc:
    NE PA
    Sounds like you removed the bolt with cap from the door, and the cap will not move on the bolt ? Perhaps the cap has been opened tightly against the bolt head?? Hard deposits can form on the bolt threads, or the aluminum draft cap can corrode to the steel bolt. (dissimilar metals) Some caps have a steel insert to prevent wear in the threads and this also prevents dissimilar metal contact. (galvanic corrosion or electrolysis) I would soak it with PB Blaster and wire wheel or wire brush the threads as close to the cap as you can. Put two nuts on the end of bolt and tighten together with two wrenches. This gives you something to hold the bolt with in a vice or with wrench on outer nut. CAREFULLY turn draft cap down bolt, after soaking for hours, and work it back and forth until it spins freely down threads.

    The 4 fin cap was the first draft cap invented by Bob Fisher's father Baxter. The original mold is owned by Barr Castings and is still available at a price. You should be able to remove it carefully. The bolt is not welded to the cap, since the bolt is tightened on the door, and the threaded cap spins up and down the threads.

    The bolt threads should be greased with high temp grease or silver anti-seize.

    Here's the patent for the draft cap. It also describes how it works;

    http://www.freepatentsonline.com/4037584.pdf

Share This Page