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Question on keel bolt/frustration

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Jan Briede
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USA
162 Posts

Initially Posted - 08/22/2010 : 12:55:27

So I spent the day trying to drill a holes to install new keel bolts. As recommended I pre-drilled the wood stub first, filled it with penetrating epoxy and this morning I started drilling with the set up that is recommended by some of you. I had bought the CD kit and started drilling. I can not get deeper then an 1/4 inch into the metal (I think). I get approximately 3 7/8 inches deep and can not get any deeper. I am using rapid tap, and yes the drill stays nice and cool. I run the drill at high RPM low RPM, I put a lot of pressure on the drill (almost my whole body weight), and no pressure. The drill does not want to go any deeper. Granted I did not drill pilot holes. It was a very frustrating day.
What am I doing wrong.
Help!

Jan Briede
Beagle
1979 TR #1242 FK
L-Dinette
Yorktown, VA
Blog -- http://vanomad.blogspot.com/

Edited by - on

mlg3733
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Response Posted - 08/22/2010 : 14:01:39

I would start with smaller bits and work my way up to whatever the diameter is. Do it in three or four steps, it should be easier.

Edited by - on

cks
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Response Posted - 08/22/2010 : 14:02:03

http://forum.woodenboat.com/archive/index.php/t-8637.html

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Stinkpotter
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Djibouti
9081 Posts

Response Posted - 08/22/2010 : 14:25:49

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by cks
 http://forum.woodenboat.com/archive/index.php/t-8637.html
<hr height="1" noshade id="quote"></blockquote id="quote">Caveat: Jan's '79 keel is cast iron, not lead.

Edited by - Stinkpotter on 08/22/2010 14:36:17

Happy D
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921 Posts

Response Posted - 08/22/2010 : 19:08:23

Once the flutes of the drill fill with chips it won't cut any longer. You need to back out the drill to enpty the flutes constantly.
Make sure the drill stays sharp. If you do not know how to sharpen drills, buy a few spares. Dull drills are miserable. Only use high speed drills or tiN coated drills. (They're a gold color drill)
Coolant is not recommended on cast iron because the carbon content is so high, it is self lubricating.

Here's how to calculate how fast the drill should be turning.

12*N/Pi*D

N=cutting speed
Pi=3.14
D=Diameter of the drill

Cutting speed of cast iron is 60 - 80 fpm.
So....
12 * 70 = 840 (we'll use 70 here, it's middle of the road)
3.14 * .375 = 1.1775 (guessing a 3/8" drill)
840 / 1.1775 = 713 rpm

So a 3/8" high speed steel drill should be turning 713 rpm to cut cast iron properly. If your drill is going faster than that it will dull the drill quickly.

Drilling a 3/8" hole, I wouldn't use a pilot drill.
I push on the drills as hard as I can. Cast iron can be work hardened and if that happens it can be hard to get through the hard spot without using a sharp drill. Use a fresh drill, run it at the right speed and push hard. Hopefully it'll break through the hard spot and begin drilling out material again.

Edited by - on

Leon Sisson
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1893 Posts

Response Posted - 08/23/2010 : 05:27:17

<center>Drillling In Cast Iron</center>
I would use pilot drills, and go up in significant steps. Consult a machinist or manual. There is a formula for optimum drill size increase. Too large a step, and you don't get the pilot drill benefit. But too small a step, and the bit tries to spiral into the hole like a tap, jams, and breaks off. You'll want to avoid that.

I agree with what others have said about using top quality drill bits. Ask a local machinist to recommend a source. Keep your bits sharp, control cutting speed (using Happy D's formula), and if possible feed rate. Too low a feed rate can sometimes work harden the metal being cut, and damage bits. I prefer cutting oil in iron because it makes such scary noises, but I'm no expert, so if a professional machinist says otherwise, I suggest you listen to them.

To estimate cutting speed (RPM), read the no load speed for the drill motor (taking into account 2-speed transmission if it has one), spin it up to full speed no load, listen to the note or frequency, mentally estimate the sound it should make when turning at your desired cutting speed, try to maintain that note with the speed control.

For drilling large holes in ferrous metals (iron and steel alloys), it's important to use a big, slow, powerful drill motor, even it you have to buy or rent one for the occasion. Watch out for wrist injuries. Use two hands on two handles, and be ready to release the trigger quickly. (Don't succumb to the temptation to lock the trigger on if holding it is awkward or tiring.) The portable drill press idea is nice, but difficult and expensive for a non-professional to acquire and set up.

-- Leon Sisson

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GaryB
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4304 Posts

Response Posted - 08/23/2010 : 10:30:27

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Leon Sisson
 <center>Drillling In Cast Iron</center>
The portable drill press idea is nice, but difficult and expensive for a non-professional to acquire and set up.

-- Leon Sisson
<hr height="1" noshade id="quote"></blockquote id="quote">
You can rent these and they will make your life much easier.

http://www.milwaukeetool.com/ProductCategory.aspx?CategoryName=SC%3a++Drill+Presses

Edited by - on

Happy D
Admiral

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921 Posts

Response Posted - 08/23/2010 : 18:33:41

How deep are you required to drill?
What size is the drill your using?
I can look up in my machinist handbook and tell you what size drills you'll need.
I am a professional machiist but I really make my drills get after it. Split point drills usually don't need a pilot.
Plus the fact I can sharpen them in a few seconds on a grinder takes all the frustration out of it for me.
I'll help all I can.
Dan
[url="http://www.newmantools.com/machines/drillpoint.html"]More than you ever wanted to know about drills[/url]

Edited by - Happy D on 08/23/2010 18:41:52

Leon Sisson
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USA
1893 Posts

Response Posted - 08/23/2010 : 18:47:43

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GaryB
 You can rent these and they will make your life much easier.
 [[url="http://www.milwaukeetool.com/ProductCategory.aspx?CategoryName=SC%3a++Drill+Presses"]Milwaukee magnetic drills[/url]]<hr height="1" noshade id="quote"></blockquote id="quote">
Yep, that's what I was thinking of when I mentioned 'portable drill press idea'. At a machine shop where I worked, I used one to drill and tap 1/2" steel plates too big and heavy to position in a regular drill press. Mag-drills require a thick flat steel surface to grab perpendicular to the drill hole, and their chuck doesn't reach much past that clamping surface without additional spindle extensions. To use one in the cabin of a fin keel C-25 would likely require some sort of adjustable 1/2" thick steel bridge clamped over the keel sump, and a spindle extension long enough to reach from the steel plate to the bottom of the sump. I doubt there's room down in the sump to position one of these. And the iron keel is buried too deep for the magnet to reach it. Not sure what Jan's arms are up for, but the mag-drill I used weighed over 60#, and was a bear to wrestle in tight quarters.

Aboard a small boat or in a boat yard, power requirements would be worth noting. Although Milwaukee clearly states the drill motor current, they're not as forthcoming about magnet power. As I recall, that base hummed and heated up like a stalled motor when it was on. For the clamping force they're claiming (3/4 ton on 1/2" steel? I'm skeptical), the magnet current would be significant.

On the plus side, Milwaukee mag-drills are slow and powerful enough to install keel bolts!

There may be (probably are) other types of specialized portable drill presses out there. Maybe consulting a local machinist would be time well spent.

-- Leon Sisson

Edited by - on

Jan Briede
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162 Posts

Response Posted - 08/24/2010 : 06:50:52

Thanks guys, cool toys, and great suggestions. I need to go my local tool rental shop and see if the have them for rent. The issue is that you need 18" bits to get sufficient access. The hole has to be 27/64" and approximately 3" deep. I have ordered three new bits in order to get a pilot hole started etc. (3/16, 5/16 and then the 27/64). I am really wondering if the bit that CD sold me was dull. I would not think that drilling through wood and epoxy would dull the drill. Alternatively I could have had too many RPMs on the drill, but even there with the rapid tap cutting fluid, the bit never really heated up. After a few minutes drilling the bit was still cool to the touch. I was wondering if there is such a thing as using too much cutting fluid. I'll check out the references and go from there and try again this weekend. Any additional thoughts are welcome.
Again thanks so much!

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Happy D
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921 Posts

Response Posted - 08/24/2010 : 07:05:13

I will make an assumption and suggest CD may not sell the best drill.
Aircraft length drills are expensive. The color of the drill should be shiny silver or gold color, not black in color. Black colored drills are cobalt and not very robust. You want High Speed steel drills.
No such thing as too much coolant. Rapid tap is pretty good stuff but will not guarantee that drill will not get dull.

IF you feel the metal has work hardened, rotate the newly sharpened drill slowly and push like mad. It should be able to break through the work hardened surface and begin cutting again.
I've seen people try to drill and accidently have the drill motor rotating in the wrong direction. Some of these drill motors are easy to get turning in reverse without knowing it.

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OJ
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USA
4382 Posts

Response Posted - 08/24/2010 : 07:28:19

Jan, you will soon be a guru on this subject and offering expert advice on same!

Once the fatigue and frustration subsides - you'll feel a sense of great satisfaction.

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skrenz
Captain

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USA
351 Posts

Response Posted - 08/24/2010 : 08:01:07

I don't know if this trick will work for you or not but I've used it in the past when drilling both masonry and metals that can have hardened spots.
Take a center punch that will fit all the way down into the hole your have already and whack it a good one several times. Sometimes it seems that this impact will almost crack the material a little bit and allow the bit to bite again.

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HeelinPatrick
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102 Posts

Response Posted - 08/24/2010 : 08:15:05

In college, we had to take a class, and it covered drilling in metal. Its funny how indepth they got, but the thing I definitely remember is not to drill too fast, too slow is ok, but too fast is defeating, and probably wears the bit a good bit. Drilling in wood, speed doesn't matter, go as fast as you like and have fun doing it! Even in highschool shop class, the drill presses and band saws seems to go painfully slow cutting metal.

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Happy D
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921 Posts

Response Posted - 08/24/2010 : 17:33:59

When I was a wee kid in machine shop class, the instructor drove a 1" drill into the grinding wheel and handed it to you and said, "Sharpen it". I remember spending at least a week sharpening that drill. When you thought it was sharp, he drilled a hole with it through 1/2" steel plate and measured the thickness and width of the curly chips. If they didn't measure the same, back to the grinder. That was one of the best things I ever learned. I hated sharpening that drill.

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Jan Briede
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USA
162 Posts

Response Posted - 09/05/2010 : 07:05:38

Well, with some new drill bits (smaller) and patients I was finally able to drill two holes yesterday to approximately 2" deep and one half way to 1". Going back today and drill to finish the half done one and drill one more. Then it is tapping the thread and I'll be close to done. I know I saw it somewhere, nut not sure if I can find it again, but 2" should be enough, I assume?

Edited by - Jan Briede on 09/05/2010 07:06:30

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