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Best way to put a deep Blind hole in something.

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by kvt, May 19, 2017.

  1. kvt

    kvt Active User Active Member

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    Ok, another question from a self taught hobby person. It is probably simple but.
    I have a large piece of steel round that I need to put about a 10 inch deep blind hole in. But do not have a drill bit long enough, and large enough to get hole started to even bore it out. The hole I need will be approx. 10 inch deep, and just over 3/4 inch 0.750 in dia, with a steel ball in the end that another shaft just under the 0.750 size would ride against. (other though was a thrust bearing rather than the steel ball). Any ideas. I know I could go purchase a long drill bit, but have not found one that is about the right length that I can get/afford at present. Any ideas/suggestions would be greatly appreciated.
     
  2. markba633csi

    markba633csi United States Active Member Active Member

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    Probably would need to make an extended drill bit by welding a shaft onto a standard size bit. It's commonly done.
    Mark S.
     
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  3. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    Extended length drills past 9" cost about $100 from McMaster Carr. Maybe an extension holder can be used to reach the 12" depth with a long drill.
     
  4. kvt

    kvt Active User Active Member

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    Mark, I would have to be a better welder than I currently do. have not done much in years, thus not very good at it any more. But if it comes down to it I may give it a try.
    EmilioG, I though of an extender, but all the ones I have seen are for 1/4 inch stuff not something like a 1/2 inch shank on a large drill bit.
     
  5. Bob Korves

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

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    Here are pics of a couple that have been brazed together. They need to be jigged in a straight line before joining them, and it is a good idea for the added shank to be a little smaller diameter than the drill. SAM_1651.JPG SAM_1652.JPG
     
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  6. Bob Korves

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

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    For your job I would get a 3/4" Silver and Deming drill (1/2" shank) and use a 5/8" extension to drive it. The extension could be drilled to fit the 1/2" shank and then the drill brazed into it, or instead could be connected with a 5/8-1/2" sleeve brazed on to a 1/2" extension and the drill.
     
    Last edited: May 19, 2017
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  7. 4gsr

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

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    Ken,

    I have a selection of extra length drill bits here at my place. Some are straight shank, some have either a 2 or 3 Morse taper shank. If you're interested send me a PM and I'll make arrangements to get one to you.

    Ken
     
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  8. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    I have made numerous extension bits by turning down the shank of a drill bit and boring a socket into the end of an appropriately sized piece of round stock. For securing the assembly, I have used a number of techniques including brazing, and superglue. I have most recently resorted to the superglue because of convenience and have never had one let go. The largest extension that I have made was a three foot extension for a 1-1/16" S & D drill bit. I made the drill by making a coupling from 3/8" black pipe and used superglue to fasten a 3' length of 1/2" SS rod and the drill bit together. In spite of the fact that I had interrupted cuts ( I was drilling through 3" steel channel at an angle), the drill held together with no sign of failure.
    Extension Drill .JPG
     
  9. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    I would add, that given the task the OP is attempting, I wouldn't use super glue for fastening. Drilling a deep hole like that will generate a lot of heat which will soften a superglue bond. Pinning or brazing would be the options that I would consider.
     
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  10. Jimsehr

    Jimsehr United States Active User Active Member

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    You can buy a 8 piece set of S&D type drills from Harbor Freight tools for $34.99.
    They have half inch shanks. You can then take a piece of stock and drill the end about an inch or more deep a few thousands smaller then half inch shank and then heat stock cherry red and insert drill shank and let it shrink fit to S&D drill of size you need. If you don't get a good fit pin it. You then have a long drill and 7 more for 35 bucks.
    Jimsehr
     
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  11. jim18655

    jim18655 United States Active User H-M Supporter-Premium

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    Could you drill from both ends and then close one end?
     
  12. kvt

    kvt Active User Active Member

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    Thanks for the responses one and all, I would be afraid to use super glue as would be afraid that it would turn loose and get jammed in the hole some how. the old adage something about if I did not have bad luck I would have no luck at all. Well that is me. So bad my wife and I both entered a drawing. one other person entered, and we did not win.
    My brazing is prob just about as bad as my welding at this point. I would have to go lease a O2 tank just to fire up the torch, and use propane. I have been out of doing thing so long it is the pits. My welder even needs the carb and fuel pump rebuilt.
    Ken If I do not figure something out this week end will send you a PM.
     
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  13. rgray

    rgray Active User H-M Supporter-Premium

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  14. mikey

    mikey Active User H-M Supporter-Premium

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    You can always use soft silver solder and heat with a propane torch to join the drill to the extension. It would be more than strong enough for that job.
     
  15. tq60

    tq60 United States Active Member Active Member

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    Here you go...
    Having a shaft rotate in this hole means cut needs to be clean.

    First get the hf set as they are decent and cheap.

    Please note...Do NOT step up as it will cut off center and chip the drill.

    Pilot drill with a 1/4 bit and this can be as a single shot or rotating back and forth.

    1/4 X 12 are not too expensive and very handy to have.

    Get a chunk of round larger than 3/4 by 2 inches long and drill 1/2 hole through it.

    Drill and tap 2 or 4 set screws to secure the drill and 1/2 round extension.

    Grind a flat or drill a pilot hole in side of extension and secure the above part to extension and place in lathe holding by extension and turn to 0.745 OD.

    The bit should have 3 flats on tge shank or make a pilot hole as in extension.

    Make part.
    Start with stock an inch longer than needed and face off.

    Center drill then drill in pilot with 1/4 standard length.

    Now use the hf drills and drill in next smaller than 3/4 a depth of 2 inches.

    Place boring bar in and bore out hole until 3/4 but just fits.

    This insures it is in center and straight.

    If you can drill deeper in step above.

    Now the hole you bored will he a guide to keep drill on center and straight.

    You will need to be sure to keep the 1/4 inch hole ahead of the larger one and use it to determine depth as the big one will change when it bottoms.

    Look at the large bit and notice the flutes STOP.

    you will need to operate your lathe in slowest speed with heavy pressure and lots of oil and peck the cut.

    The coupler you made will also support the drill as it goes into the hole.

    Go slow and it should have a clean cut.

    You can polish it with a wheel cylinder hone if needed

    Sent from my SAMSUNG-SGH-I337Z using Tapatalk
     
  16. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    One of this mornings jobs, 7/16" hole through an 8" length. Spot drilled then went all the way through with a 12" long 7/16" drill, if I had stopped at 7 3/4 it would have been a blind hole.
    2" OD 4140 annealed with a 3/4-14 British Standard Pipe Parallel external thread on one end and an internal thread on the other just to make it more fun. They are a 55 Deg. Whitworth thread form for which we had exactly one insert.
    Some species of hydraulic adapter.

    You should have no problem drilling 8" deep with a suitable length drill. If you require a more accurate sized hole drill slightly small then ream.

    [​IMG]
     
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  17. Plum Creek

    Plum Creek United States Active User H-M Supporter-Premium

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    I have a torch and brazing tip at the shop near Kyle that your welcome to use if you decide to solder or braze.
     
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  18. Charles Spencer

    Charles Spencer Active User H-M Supporter-Premium

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    Good idea. Combined with grinding a flat and using set screws I think it would be pretty solid.
     

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