drill bits

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seattleboatguy

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I need to drill out a frozen bolt on my Westerbeke 4.4kw generator. It's the bolt that a bracket pivots around to tension the belt. I expect to go through several drill bits in the process, and I was wondering if you guys sharpen your old bits or just buy new ones at the hardware store? Thanks.
 
I buy new but also keep the old for wood.
 
I'd start the project by buying cobalt drill bits. Good luck.
 
Try to find left hand twist drills. You may find the bolt turning out as you drill it.
Watch this video. It has some great ideas for keeping the drill centered.
 
Drill bit sharpener is one of most valuable tools on the bench. Keep em sharp, tempered, with a good cutting oil - much easier.
 
Impressive video Parks. No BS, just "this is how it`s done". The OP won`t have the luxury of the job on a bench, but he`s off to a flying start. I had a friend who was a toolmaker on top of fitter and turner, watching someone with real expertise with metal is a treat.
 
If there is enough thread in the hole to use another bolt then that bolt could be drilled to centre the bit long enough to start the pilot hole in the broken bolt.
I have made guide plates of 1/4 steel to align the bit properly so it drills on centre if there is/are another couple holes nearby to hold the guide plate.

I agree about the reverse twist bits and have had success with those on a number of occasions. Sometime even though broken the remained is loose or loose enough for the reverse bit to back it out.

There is a tool called a combined pilot and countersink tool used usually on a lathe but also in drill press operations. The pilot part is quite a bit smaller than the body . These a quite short tools, HARD, and if used carelessly can break.
High speed and coolant for the pilot part just to get the hole started in the broken bolt. Once done then the other bit can be used.

Try using a dremel with a small stone that can reach in to grind a flat spot so the drill bits, which ever you use has a flat area to start on. Otherwise the bit is going to wander.

I use new bits in cases like this. I am reasonably good at resharpening bits but no where near good enough for this. And yes a cobalt bit is just a little bit better than the usuall HSS.

And try to find a GOOD penetrating oil to hopefully help with the broken bolt part.
Kroil , is good.
 
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I broke a lot of drill bits like many.

Then I bought a small set of left twist, Irwin brand cobalt drill bits and they even drilled broken taps nicely.

Best I have used by far!
 
psneeld said:
I broke a lot of drill bits like many.

Then I bought a small set of left twist, Irwin brand cobalt drill bits and they even drilled broken taps nicely.

Best I have used by far!
Click to expand...

I have 2 sets of Irwin’s. :thumb:
 
HopCar's video and FF's bit sharpener were both pretty cool. Thanks very much. Fortunately, I don't have to worry about ruining threads deep inside a shaft. Both ends of my nut and bolt are visible, though not easy to attack. It is the shaft in the center that has welded itself with corrosion to the belt tightening bracket. I may have to move the generator to get at it, which will not be easy, but I think I can eventually get it off of there. Thanks for the feedback.
 
While taking apart stuff will work with any drill that survives , some holes need to be structural.

A new bit will drill a round hole the size of the drill bit , but a hand sharpened bit will drill a larger hole as eyeballing the drill center is near impossible.

The drill bit sharpener system centers the drill, so it drill the size hole you planned on.
 
ancora said:
As an apprentice, I was told by my mentor to never refer to a drill as a "bit." It is a drill.
Click to expand...
I've heard that opinion before but have never seen anything to substantiate it other than " I knew someone".
Completely contrary to what my mentors told me and I find in "print" anywhere.
Got any confirming evidence?
 
I have a Drill Doctor. Yes it sharpens bits but takes practice. Probably takes much less time to sharpen a bit than driving back and forth to the hardware store.
 
Porgy said:
That explains it! I know a very experienced guy who always called it a “drill motor.”
Click to expand...


I learned the correct terms are drill motor and drill bit. Shortened for convenience to drill and bit.
 
Bacchus said:
I've heard that opinion before but have never seen anything to substantiate it other than " I knew someone".
Completely contrary to what my mentors told me and I find in "print" anywhere.
Got any confirming evidence?
Click to expand...
Stephen A Morse (the Morse taper guy, not the Morse code guy) invented the twist drill bit as we know it.

He patented it as the "Twist Drill Bit"

US patent 38,119. April 7, 1863

So I'm thinking "drill bit" is just fine. I will check with my son, who is currently an apprentice machinist/millwright.

I would opine that if it a drill with a Morse taper and used in a lathe, it is a drill. If it is held in a chuck, it is a drill bit.
 
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Northern Spy said:
So I'm thinking "drill bit" is just fine. I will check with my son, who is currently an apprentice machinist/millwright.
Click to expand...

Every toolmaker/machinist I know will call it a "drill". I got corrected so many times I usually call them drills as well. (toolmakers love to tell engineers that they know more LOL)

But to me I know what one s referring to so it's not worth the discussion.
 
Two things happen when you use a drill bit on a broken bolt. The first thing is that the bit gradually becomes less sharp. Notice I did not say it becomes dull, this happens later. As the bit becomes less sharp it begins to generate more and more heat. This heat, rather quickly, hardens the bolt. From that point on things deteriorate very quickly.

To avoid all these problems just do two simple things. #1) Drill at low speed, #2) add a cooling agent, generally oil but water will work.

If you have already dulled several bits, it is too late. The bolt is well tempered and will be nearly impossible to drill.

pete
 
Wonder what a machinist thinks of a "brace and bit"?
 
A standard drill bit (or whatever you want to call it) should drill several holes. Most people are in a hurry and use too much pressure and no lubricant. And the bit burns out. It's better to drill a smaller hole first. And in drilling a large diameter bolt, it's better to drill a series of holes. It's easier on the bits because they're using a smaller area on the tip and creating less heat. Bits are heat treated to make the point harder, too much heat causes the temper to go away. Then the bit becomes dull faster.

I use Kearney Rust Cutter on stuck steel and iron nuts and bolts. It's made for power transmission linemen. Working 200 feet in the air, they don't have time or the tools to deal will drilling out a rusted bolt. This spray lubricates, but also dissolves the rust in the threads by including a weak acid in the mix. Spray it on stuck, rusted nut and bold threads and in less than a minute the threads are free. It also works on any kind of rusted parts. I also use it for rings rusted to the cylinder. About $10/can on ebay.
https://www.ebay.com/itm/Kearney-Ru...411613&hash=item3d85caf00f:g:bD0AAOSwEdteC4sk
 

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