Broken drill

Discussion in 'Clock Repair' started by Jeff Fawcett, May 15, 2020.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. Jeff Fawcett

    Jeff Fawcett Registered User
    NAWCC Member

    Apr 27, 2011
    46
    4
    8
    2 screws holding the crown piece to the front plate of a Kienzle 400 day clock had sheared off at the top of the plate and I tried to drill them out. Using a 0.94mm tungsten carbide drill the first one was successful but as I was extracting the drill from the second one, the drill broke off just below the top of the plate. I am looking for advice on how to extract the broken piece.It will not shake out. Can I try to drill it out with another, slightly smaller drill? There may be 3 or 4mm of the drill still in the hole.
    Any suggestions will be most welcome.
    Jeff Fawcett
     
  2. Vernon

    Vernon Registered User
    NAWCC Member Sponsor

    Dec 9, 2006
    706
    75
    28
    Male
    Soon to be retired
    Country Flag:
    Region Flag:
    I would try a pointed punch or some other steel and tap it with a hammer to break up the carbide. This has worked for me although mine maybe wasn't as deep.
     
    Al Dodson likes this.
  3. TEACLOCKS

    TEACLOCKS Registered User
    NAWCC Member

    Mar 22, 2005
    2,317
    77
    48
    Male
    Clock service & repair
    Santa Rosa Calif.
    Country Flag:
    Region Flag:
    Did you drill all the way through the plate ?
    If so use a punch from the backside.
     
  4. Kevin W.

    Kevin W. Registered User
    NAWCC Member

    Apr 11, 2002
    22,386
    345
    83
    I work at the Veritas Tools machine shop.
    Nepean, Ontario, Canada
    Country Flag:
    Region Flag:
    Are the plates brass?
     
  5. JimmyOz

    JimmyOz Registered User

    Feb 21, 2008
    496
    89
    28
    Male
    Country Flag:
    Region Flag:
    I have used pivot wire slightly less than the diameter as the broken drill, gently grind 4 flats to a point, cut it short enough to hold so less flex and tap with a hammer and turn and so on.
     
  6. Tbucket

    Tbucket Registered User

    May 7, 2016
    12
    2
    3
    Male
    Account Manager for a Machine Shop
    Easton, Pa
    Country Flag:
    Region Flag:
    If the carbide drill was a twist drill, you can try to stick 2 pcs. of pivot wire into 2 of the flutes of the broken drill. grab the wire with pliers and carefully try to twist the drill clockwise & counter clockwise until it comes loose. you won't be able to drill into the carbide with anything. The recommendations for breaking the carbide are also good ideas that can work. I found another good way to remove a broken screw is to drill it out with a smaller diameter left hand drill. This sometimes will grab the screw & begin turn it out.
     
    Al Dodson and Bruce Alexander like this.
  7. shutterbug

    shutterbug Moderator
    NAWCC Member

    Oct 19, 2005
    43,209
    1,189
    113
    Male
    Self employed interpreter/clock repairer
    North Carolina
    Country Flag:
    Region Flag:
    If it didn't go all the way through, try drilling from the other side until it hits the broken bit and then punch it out from that back side.
     
  8. Jeff Fawcett

    Jeff Fawcett Registered User
    NAWCC Member

    Apr 27, 2011
    46
    4
    8
    Thank you to all 6 for your suggestions. The plates are brass - about 2.7mm thick and the holes in question enter from the top edge of the plate so there is no means of "punching from the back". I tried the first suggestion from Vernon and attempted to break the carbide with a steel punch. This only resulted in the drill piece being pushed to the bottom of the hole. I've been able to get a few very small broken fragment out but am concerned that more punching will result in damage to the plate. I'll try "fishing" with wire but the flutes on a 0.94 mm drill are quite small and I don't think I have the wire to do this.. Where can I get a left hand drill not more than 1.00mm If all else fails I'll see if I can tap enough treads into the top 3 or so mm of the hole that are available to give sufficient purchase to a screw ( once I have made a screw). I can't get to this until I get the tap and die - hopefully next week.
    Thanks again and stay safe, Jeff.
     
  9. Jerry Kieffer

    Jerry Kieffer Registered User
    NAWCC Member

    May 31, 2005
    2,625
    340
    83
    Male
    wisconsin
    Country Flag:
    #9 Jerry Kieffer, May 17, 2020
    Last edited: May 17, 2020
    Jeff
    Let me make a wild guess in that you were drilling with a cheap carbide circuit board drill.

    Unfortunately, you cannot drill Carbide period with the exception of expensive diamond drills.. However, you can reach down in the hole and grind the drill out with a micro diamond bur, utilized in a 300,000 RPM mini die grinder if so equipped. Attached Photo.

    If indeed it is a circuit board drill, the thin flutes will grind quite easily with diamond. Since it is brass, you could make a core drill and drill a enlarged hole that is then plugged, redrilled and threaded. This would require a milling machine for accurate work.

    Jerry Kieffer

    fullsizeoutput_5c8.jpeg
     
  10. etmb61

    etmb61 Registered User
    NAWCC Member

    Oct 25, 2010
    2,470
    166
    63
    Retired Avionics Technician
    Mascoutah, IL
    Country Flag:
    Region Flag:
    If you were trying to drill out the steel screw with a bit that was a smaller diameter, you could try to dissolve the remainder of the screw in an alum bath. The rest of the broken bit might just fall out then. In the future just use the alum bath. This is a common problem on older 400 day clocks. Put the drills down!

    Eric
     
    DeweyC likes this.
  11. Kevin W.

    Kevin W. Registered User
    NAWCC Member

    Apr 11, 2002
    22,386
    345
    83
    I work at the Veritas Tools machine shop.
    Nepean, Ontario, Canada
    Country Flag:
    Region Flag:
    What about using alum to disolve the steel drill bit, thats why i asked if it was brass, the drill was broken off in.
     
  12. etmb61

    etmb61 Registered User
    NAWCC Member

    Oct 25, 2010
    2,470
    166
    63
    Retired Avionics Technician
    Mascoutah, IL
    Country Flag:
    Region Flag:
    I don't know if the weak acid created in the alum bath would even touch tungsten carbide. I doubt it.

    Eric
     
  13. Elliott Wolin

    Elliott Wolin Registered User
    NAWCC Member

    Nov 18, 2019
    232
    19
    18
    Male
    Retired
    Williamsburg, Virginia
    Country Flag:
    Region Flag:
    I've seen mini-sandblasters in machine shops that are used to break up or ablate broken end mills. Any machine shops handy?
     
  14. Jeff Fawcett

    Jeff Fawcett Registered User
    NAWCC Member

    Apr 27, 2011
    46
    4
    8
    Thanks again everyone. In the absence of a milling machine, micro diamond mini die grinder and access to a mini sand blaster, I’ll give the alum bath a try and also get pivot wire to fish down the hole. (the broken fragment is about 3mm below the top of the hole and I can’t see it very well). Yes, Jerry they are Japanese made cheap circuit board drills with colour coded plastic collars. A local surplus store (now closed unfortunately) had a bushel basket full of them in a wide range of sizes – 50 cents each. I don’t know if they are solid carbide, in which case solution is not likely to work, or if they are carbide tipped or vapour deposited which may give the solution a chance to work.
    Make a core drill:???:? The existing hole is about 1mm and the plate only 2.7mm thick. I work with a Unimat mini lath and this is above my skill level.

    Off to the grocery store for alum, tomorrow.

    Jeff.
     
  15. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
    10,241
    838
    113
    Male
    Trappe, Md.
    Country Flag:
    Region Flag:
    I'm trying to visualize this clock and the hole with the broken bit. Would it be possible to post some pictures?

    RC
     
  16. Jeff Fawcett

    Jeff Fawcett Registered User
    NAWCC Member

    Apr 27, 2011
    46
    4
    8
    IMG_20200518_111059.jpg IMG_20200518_111601.jpg IMG_20200518_111821_BURST001_COVER.jpg
    Hello RC here are 3 photos ; 1 shows the front plate with the crown piece above and one finial in place, next is a top view of the crown piece showing 2 holes for attaching to the plate and 2 empty holes for the finials . The third photo show the top edge of the plate with 2 screw holes. The one of the left is drilled down to about 5mm. The right side hole contains the broken drill piece - the top of which is about 3mm below the plate edge. As noted previously, the holes were drilled with a 0.94mm drill and the plate is about 2.7mm thick. I hope this is clear.

    Sorry everyone -I should have posted the photos with my first message.
    Jeff

    IMG_20200518_111059.jpg IMG_20200518_111059.jpg IMG_20200518_111601.jpg IMG_20200518_111821_BURST001_COVER.jpg
     
    etmb61 likes this.
  17. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
    10,241
    838
    113
    Male
    Trappe, Md.
    Country Flag:
    Region Flag:
    Thanks for the pictures. I've never tried alum so will be interesting to see how that goes. If all else fails there are two possibilities that come to my mind. If the finial will unscrew from the threaded stud, then you may be able to secure the threaded stud in the 3mm hole with some JB-Weld - slip the crown over the stud and screw the finial back on. There isn't much load so all you need to do is keep it in place. another option might be to cut into the side of the hole on the non-visible side of the plate, remove the broken drill, fill the cutout and retap. More drastic, just cut out the hole section from the plate and carefully fit a new piece of brass then drill and tap a new hole. Good luck.

    RC
     
  18. gmorse

    gmorse Registered User
    NAWCC Member

    Jan 7, 2011
    11,276
    1,580
    113
    Male
    Retired from Xerox
    Breamore, Hampshire, UK
    Country Flag:
    Region Flag:
    Hi RC,

    I very much doubt if it's even worth trying; I've used this many times on steel screws, but I believe the chemical reaction relies on the presence of iron, which probably isn't present in a carbide drill, at least the business end of it.

    Regards,

    Graham
     
  19. DeweyC

    DeweyC Registered User
    NAWCC Member

    Feb 5, 2007
    2,122
    767
    113
    Watchmaker
    Baltimore
    Country Flag:
    Like Eric said.

    Graham we cross posted. He states earlier it is in a steel screw thread.

    If the drill bit is stuck in the screw remnants you are home free. The alum will dissolve the steel around the carbide and the drill will fall out. Maybe heat the bath on a hot plate.

    I know all of this is offered after the horse got out of the barn. I think you will get out of this ok.

    For the next time?

    First, you obviously did something right because you got one drilled ok and the second one partially. To help you understand what happened:

    The high twist rate and length of ckt board drills make them very fragile. Way too much overhang for the stiffness. I use them as small as 20/100mm for repivoting, but I will not describe that here unless asked.

    So, you were running against the odds if you used ckt board drills. Regular carbide twist drills of this size are available from MSC.

    Secondly, unlike standard machine drills, carbide drills are very precise. There is very little clearance between the ID and the drill itself. As the friction heats the drill, it can expand enough to seize in the work. Snap.

    I use saliva as a lubricant and others prefer Oil of Wintergreen. And you have to very frequently back the drill out of the work to clean out the swarf. The second it stops sending up swarf, back out as well. Lubricate and slowly reintroduce.

    But (and this is the horse that got away) an AWG screw machine length cobalt drill (no 60 is 1.03 mm, no 61 is smaller) should have done the job no sweat. And the work "should have" been solidly clamped and a drill press used. And the clamping should be at the same level as the work area to minimize vibration. Drill overhang should still be at the absolute minimum (hence the use of screw machine length drills). Center punch and prick punch the surface since the sheared surface is unlikely to be flat.

    Regards,

    Dewey
     
  20. etmb61

    etmb61 Registered User
    NAWCC Member

    Oct 25, 2010
    2,470
    166
    63
    Retired Avionics Technician
    Mascoutah, IL
    Country Flag:
    Region Flag:
    Jeff,

    Be sure to take the click off before putting the plate into the alum bath. For better results keep it hot and use distilled water. When it's doing it's job you should see little bubbles forming on and rising from the steel.

    Eric
     
    DeweyC and Kevin W. like this.
  21. gmorse

    gmorse Registered User
    NAWCC Member

    Jan 7, 2011
    11,276
    1,580
    113
    Male
    Retired from Xerox
    Breamore, Hampshire, UK
    Country Flag:
    Region Flag:
    Hi Dewey,

    Ah, so he did.

    Regards,

    Graham
     
  22. Jerry Kieffer

    Jerry Kieffer Registered User
    NAWCC Member

    May 31, 2005
    2,625
    340
    83
    Male
    wisconsin
    Country Flag:
    #22 Jerry Kieffer, May 18, 2020
    Last edited: May 18, 2020
    While circuit board drills work great for what they are designed for, they are certainly not designed for steel or even other metals. With the availability of special use tooling in todays world, there is no reason to risk anything of value with their use regardless of how they are utilized. While easily removed if equipped as mentioned, sometimes you have to deal with what ends up in your path. If all else fails in the removal attempts, not all is lost if indeed you still have 3mm of depth in your hole. In general, threaded fasteners often reach peak strength at about 3-4 full depth threads. If you could utilize a slightly larger thread such as a 0/80 or 1/72 or 1.5mm thread as an example, you would have space for about 8 threads using a bottoming tap. For this, I would suggest a H1 tap.

    Good Luck
    Jerry kieffer
     
  23. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    19,706
    408
    83
    utah
    Country Flag:
    Region Flag:
    Use a left-hand drill bit.
     
  24. Jeff Fawcett

    Jeff Fawcett Registered User
    NAWCC Member

    Apr 27, 2011
    46
    4
    8
    Thanks again gentlemen; it will be a few days before I can get back to this job. I'll let you know when I have more to report.
    Jeff

    ;
     
  25. shutterbug

    shutterbug Moderator
    NAWCC Member

    Oct 19, 2005
    43,209
    1,189
    113
    Male
    Self employed interpreter/clock repairer
    North Carolina
    Country Flag:
    Region Flag:
    One other possible option is to drill another hole directly against the broken bit, on the thicker side of it. That would make it try to spin in the other direction. If that didn't turn it out, it might be able to be forced into the new hole and removed. Then you'd have to machine a part to fill both holes and allow re-tapping. That part could be secured with something like Tix solder. As mentioned, no bearing weight there. You might have to reshape the area to receive the machined part.
     
  26. R. Croswell

    R. Croswell Registered User

    Apr 4, 2006
    10,241
    838
    113
    Male
    Trappe, Md.
    Country Flag:
    Region Flag:
    Possibility, or you could end up with a second busted drill stuck in there.

    RC
     
  27. shutterbug

    shutterbug Moderator
    NAWCC Member

    Oct 19, 2005
    43,209
    1,189
    113
    Male
    Self employed interpreter/clock repairer
    North Carolina
    Country Flag:
    Region Flag:
    I recall a childhood tale about sending one cheese wheel down the hill to get the other one that was lost. :D
     
  28. Kim Miller

    Kim Miller Registered User
    NAWCC Member

    Nov 21, 2012
    59
    1
    8
    Male
    Iowa
    Country Flag:
    Region Flag:
    Jeff, I may be able to help you with this. Check you PM.
    Kim
     
  29. TEACLOCKS

    TEACLOCKS Registered User
    NAWCC Member

    Mar 22, 2005
    2,317
    77
    48
    Male
    Clock service & repair
    Santa Rosa Calif.
    Country Flag:
    Region Flag:
    Drill a hole in the front or back of the plate with a diamond hole drill then knock out the broken drill then plug the hole then maybe plug where the broken drill was and drill & tap a new hole.
     

Share This Page