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biax scraper repair/rebuild

Discussion in 'MACHINE RESTORATION & WAY SCRAPING' started by Sblack, Apr 28, 2017.

  1. Sblack

    Sblack Canada Active Member Active Member

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    I bought a very well used biax 7ELM power scraper. The part where the blades attach slides on 2 metal bars that are held to the body of the scraper with 4mm dowel pints. These bars, or sliding surfaces, are highly polished and are the main wear surfaces. I shudder to think what a replacement costs. I am missing one so I will make it - anybody know what material is used? It is very magnetic, so it isn't stainless, and a file will bite into it, so I don't think it is hardened, at least not too much. I will likely have to shim them up to eliminate play. Also, the round bearing in which the ram rides looks to be quite worn so I will try to replace this as well.

    In addition to the slide material, does anyone know what the sliding surfaces are supposed to be lubricated with?

    thanks

    Scott
     
  2. vtcnc

    vtcnc H-M Supporter - Premium Content H-M Supporter-Premium

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    Can't answer you questions...sorry. But I am very curious to see the construction of the inside of one of those. Will you be posting pictures of the rebuild?
     
  3. Sblack

    Sblack Canada Active Member Active Member

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    ok I got a prompt reply from Dapra including their exploded parts diagram. They quoted the price for that little metal strip (part 78) or perhaps for a pair. $86!

    upload_2017-4-28_15-26-29.png

    I am sure that everybody's first reaction is - are they crazy? But, this is made in Switzerland, Dapra has no control over what the parts charges are, and the parts looked to be highly polished and lapped. I am missing 1 of the part 78s and 2 of the pins. They look like 4mm dowel pins. The other part 78 is still there along with the pins. They show no sign of wanting to come out. So I will make new pins and a new plate, polish it and shim it up. There is a lot of wear on the "shoe" - this is the part that rides on those plates on one side and on the other has the surface where the blade attaches. I don't think I can do much about that without a surface grinder, so I will just shim up the plates to eliminate any play. Also, there is a lot of play in the spindle bearings (51). They look like some sort of plain bearing so I will fire up the lathe and turn some new ones.

    The motor doesn't seem to run at a very consistent speed - perhaps the brushes are badly worn or the armature needs to be turned. This thing has likely been used every day for decades, so I shouldn't be surprised. There are very few awesome deals in this world where you get a $4000 machine for $200 that is in new condition. But, with some sweat equity I hope to get this thing working and make some blades and get scraping without spending a fortune.
     

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    Last edited: Apr 28, 2017
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  4. Silverbullet

    Silverbullet Active Member Active Member

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    I would guess it's spring steel. Very tuff but workable, like bed frame angle iron it's made to flex but remain strong. I too would like pictures , seems to be like a reciprocating saw only shorter strokes and I think they orbit some too.
     
  5. Sblack

    Sblack Canada Active Member Active Member

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    I don't think there is any orbital motion.
     
  6. Silverbullet

    Silverbullet Active Member Active Member

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    Be careful turning the armature , the copper will gum over the mica slots , test it for shorts , look for cracked or melted brush housings , if there adjustable Ck the distance and for shaking . I'd put new brushes and fresh grease in the gear box. Even switches will short internAlly .
    Only trying to help , with an armature stick the armature can be cleaned easier then turning . Only the sticks are hard to find and costly last one I got from Grainger s was over thirty dollars in 1987. I'd swear it looks ALOT like the old Milwaukee sawzall .
     
  7. Sblack

    Sblack Canada Active Member Active Member

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    I an unencumbered by any experience turning an armature so I appreciate your advice. I have never heard of an armature stick. I will take a pic of the armature and post it to get some feedback before I do something regrettable!

    I am pretty sure this thing is way more robust than a sawsall. They cost 4 grand and the swiss aren't known for cutting corners. But I have not opened it up yet so we shall see. This thing came from Busch precision. It was probably scraping camel back straight edges 40 hrs a week for a decade or two. I suspect to find a lot of wear. I hope it is designed in such a way that the worn parts can be replaced easily.
     
  8. Silverbullet

    Silverbullet Active Member Active Member

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    The armature stick is really a soft stone about 1/4" x 1/2" x 6" if i remember you can run the motor and use the cleaning stick stone , it depends who sells what it's called. But I use to hold a corner to the armature thin side to comutator after a few motors a small arc is formed making cleaning quicker and easier. Spin the armature while applying light pressure to comutator it should clean up move if back and forth ,. Some motors with the brush out the stone will fit right I that way to polish it up. Be very carefull with the windings don't scratch the varnish or they can short out. Bearings should be replaced if not ever been changed. If it's that old they will or should have been several times. Motor shops may have the cleaner stone
     
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  9. Silverbullet

    Silverbullet Active Member Active Member

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    Lincoln WELDER , brush setter stone on eBay , bigger in width then mine but should work and about $12.50, mine was for electric tools . But I don't see them on there.

    Just found one ideal comutator resurfacing tool , $18.00 + $300 shipping listed in motor tools
     
    Last edited: Apr 28, 2017
  10. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    First thing I would do is clean the armature with electrical cleaner, not brake cleaner! Next, look for any damage to the commutator segments. If none, take a piece of 240 grit flint paper and polish the commutator. DO NOT USE EMERY CLOTH!!! Just good old flint paper that you use in woodworking. Emery cloth will leave contaminates in the commutator and cause it to short out no matter how good you clean it. Brush setter stone works good too if you can find one small enough to use on it.

    The rails are some kind of harden bearing steel like 52100 but under a DIN/German number. Should be able to get by using flat ground stock and if you want to harden and grind it, will last a life time for you. An A-1 or O-1 tool steel is plenty good to use for this part. At least you can buy parts for yours, I have one of the old blue ones with parts made of unobtainium!
     
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  11. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Others, including me, are also interested in some repairs to the old Biax scrapers. The way to repair #78 is to remove it, surface grind it flat, and then shim it back to original thickness, preferably in pairs, together. The shoe that rubs on them can also be surface ground, though it is a bit more fussy to set up to grind. I see no need for new parts there unless there is severe damage aside from wear. After getting them correct, keep them oiled regularly!
     
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  12. Ulma Doctor

    Ulma Doctor Infinitely Curious Active Member

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    they are called Commutator Stones,
    i used my share and someone else's- i repaired electric forklift motors of all sizes and ratings, by the score.

    the comm stones come in a variety of sizes and grit
     
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  13. Sblack

    Sblack Canada Active Member Active Member

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    Hi Ken thanks for the info on the steel. Is the shoe cast iron so it is cast on steel? Or is there supposed to be some sort of lubricant between them?
     
  14. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    I'll have to pull mine out and take a look at it. I doubt the shoe would be cast iron, more than likely harden steel of some grade. As for lubrication, somewhere in the 10 page book to the scraper, it says something on the order to apply a few drops of oil to the slide every once in a while. Have to remember, mine is one of the old blue one's that's over 25 years old. Maybe closer to 40 years old.
     
  15. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The shoe is hardened steel.
     
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  16. Sblack

    Sblack Canada Active Member Active Member

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    So hardened steel on hardened steel? And no onvious means of lubrication like a oil port or oil grooves etc? I would never have expected that.
     
  17. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    The harden steel has some kind of hard coating that resists galling. More than likely, it's been nitrided. Nitriding has some anti galling properties.

    Ken
     
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  18. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The wear on my Biax slides is much less than the wear on the exterior of the machine. It must have been used to death, and it still works fine, just loose in the flat slides. Looseness in the slides can contribute to digging the corners of the scraper blade in to the work, which can be discouraging. I would like to fix mine, but am not yet sure of what I am doing. As far as lube goes, I think I will be using way oil, often but sparingly, and cleaning the slides regularly.
     
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  19. chips&more

    chips&more United States Active User Active Member

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    That’s a cute little grinder in the video! Could it be a Stent kit?
     

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