Drill bit sharpener

Discussion in 'Maintenance Bay' started by Let'sgoflying!, May 28, 2022.

  1. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    Does anyone sharpen their drill bits? Working on a project today I was reminded how messed up my large bits are.
    Hand sharpened on a grinder with mixed success.
    Pal said his shop swears by this Drill Doctor Replacing all my large bits is going to be $150+ so I’m thinking about this.
    Metal cutting bits, 1/4”-3/4”
    Do bits have a hardened edge which would be lost with sharpening?

    https://www.drilldoctor.com/shop/product-category/sharpeners/
     
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  2. Jim K

    Jim K En-Route

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    Drill bits are usually made of "high speed steel" which is very hard. There are various coatings used, but they don't make enough difference to worry about.

    I have a drill doctor and generally like it. It's not perfect... about 75% of the time it produces a satisfactory cutting edge, but they usually wander more than a factory ground bit. If you have good eyes and patience, you could probably learn to do a better job by hand, but I have neither of those

    My DD is around 8 years old. I haven't looked at their offerings since then, but at the time it was the most expensive one they sold. Previously I had one of their cheaper models, but it could only do up to 3/8. The one I have now can do 1/2, or maybe even 5/8, I'd have to look. It still feels like a cheap plastic toy, but it does the job. Nothing I hate worse than a dull bit, except maybe when an index is missing one or two bits.
     
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  3. Tarheelpilot

    Tarheelpilot Final Approach PoA Supporter

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    The DD is worth buying.
     
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  4. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    Yes. It takes some practice, but eventually you get it.
     
  5. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    One confounding factor is…. I’m a huge sucker for new tools.
     
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  6. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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  7. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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  8. Mxfarm

    Mxfarm Line Up and Wait

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    Drill bits are a compound angle on a cylinder on 2 sides of that that cylinder that need to match. I’m meh on the drill doctor, but better than by hand w/no experience. If you have a local sharpening business, they should have a high end drill bit sharpener that will take the bit back to new sharpness. Yes, w/practice you can sharpen by hand, they’re just rarely 100%.
     
  9. Bell206

    Bell206 Final Approach

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    In my experience, it depends on the drill bit quality, precision needed, or the job at hand whether its worth to sharpen. I consider any bit smaller than 5/16" as consumable and replace as needed. Quality wise I buy at whatever level dictated by the job at hand. Larger than 5/16" I have a high quality index set that can be sharpened a number of times, if needed. But have only sharpened the 3/8" bit twice. FWIW: the life of any drill bit depends on how you use it and selecting the right bit material for the job.
    Usually the quality of the drill bit will determine that. While hardening varies, on most cheap bits that hardening can be worn through during its use and definitely via sharpening.
     
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  10. sarangan

    sarangan Pattern Altitude

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    I have one of these, and they do work. But I have found that the sharpened drill bits don't last nearly as long as the new ones, probably because of the lack of coatings. Eventully, I ditched all my drill bits and bought new ones.
     
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  11. Dan Thomas

    Dan Thomas Final Approach

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    Buying drill bits can be hazardous. There are so many levels of quality out there, and good stuff is expensive.

    There are at least five bit materials: Carbon steel, the cheapest stuff. High-speed steel, which has more carbon and other alloying metals in it. Cobalt steel, which is HSS with cobalt added for hot hardness. There are the TiN-coated bits, the yellow ones, plated with titanium carbonitride. That's a hard coating that makes the cutting easier and acts as a friction-reducer. Sharpening that bit removes the TiN from the cutting edge. And then there are the solid carbide bits, much more money, but can cut under high heat. They also chip easily, and if you use coolant you have to flood them or leave them dry. Anything in between causes thermal shocks that crack and fail the bit.

    I sharpen my bits by hand, even some tiny ones, but if you don't get both flutes right at the same angle, and the chisel edge right exactly in the center, it will drill an oversize hole. Too much rake leaves the cutting edge too thin and it overheats. Too little and the heel drags.

    Never used a Drill Doctor. Had a chance to buy one real cheap many years ago, and should have. I have sharpened, by hand, bits from #40 (not much success most of the time) up to 1-1/2" or so. Big ones are easy.

    Lots of stuff on the internet as to how to do it. Stuff like this:

    upload_2022-5-28_11-48-12.jpeg

    Thinning the web, if done right, will make a bit drill like mad and will generate a lot less heat. he idea is to shorten the length of the chisel edge.

    upload_2022-5-28_11-50-2.jpeg

    Or:

    upload_2022-5-28_11-51-20.jpeg

    I have also re-heat-treated bits that have been overtemped. Sharpen them first, then heat the end to a dull red and quench it in water or oil. Clean off all the oxide, then heat very gently until a straw-colored oxide appears, and let it cool. Then give it a final sharpening. Big expensive bits are worth this. Not the average smaller cheap hardware-store stuff.

    New bits that chip easily haven't been tempered enough. They're too hard. Do the gentle heating to get the yellow oxide, and they'll work better.
     
    Last edited: May 28, 2022
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  12. JAWS

    JAWS Cleared for Takeoff

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    My dad could sharpen drill bits fast and accurately by hand well into his 80's. That is a skill I definitely do not have. I have used the drill doctor with varying degrees of success.
     
  13. Albany Tom

    Albany Tom Pattern Altitude

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    There is a Youtube channel called "project farm" where he reviews tools along these lines, and did a report on drill bit sharpeners. I really don't remember the outcome. It's a good channel, though.
     
  14. Joe_B1

    Joe_B1 Line Up and Wait

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    DD works great for me. I learned to sharpen drills on a grinder years ago but laziness got me and I bought one. It takes some practice to get the DD to work well, but once you get it, it's fast and easy.
     
  15. Snowmass

    Snowmass Line Up and Wait

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    I hand sharpen my bits all the time. It's not that difficult except for the tiny sizes. BTW if you want a precision sized hole taper the drill so it only cuts with the side after drilling a pilot hole slightly smaller. This way it acts like a hone.
     
  16. pfarber

    pfarber Pre-takeoff checklist

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    I don't think you understand what a hone is if you think a hand held sharpened drill bit is a precision hole sizing tool.
     
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  17. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    DrDr enroute; check back for review
     
  18. Dan Thomas

    Dan Thomas Final Approach

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    He means reamer, not hone.
     
  19. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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  20. Snowmass

    Snowmass Line Up and Wait

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    Yes, you are right I meant a reamer. The hole will be much more precise that a drilled hole which tends be slightly oversize due drill point being slightly of dead center.
     
  21. Dan Thomas

    Dan Thomas Final Approach

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    Most drills, if the point is right on center, will drill slightly undersize. Just take a micrometer to a bunch of them and see what you get.
     
  22. Snowmass

    Snowmass Line Up and Wait

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    The only way this seems possible is that the drill friction expands the metal slightly while drilling and when the metal cools it shrinks a bit.

    I have never had a need for a precision hole but the reamer from drill idea came from Alec Clarkson who invented the Britain Autopilot (sp?) with the idea of using a single tilted rate gyro to stabilise both roll and pitch. He also invented the Super Venturi to both power the gyro and the rolling diaphragm actuators connected to the ailerons for airplanes without vacuum pumps. He held many patents and was an expert machinist.
     
  23. Mxfarm

    Mxfarm Line Up and Wait

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    turn drill bit to slow and you’ll get a oversized hole also.