This is true wisdom and I am not really adding anything, but I would like to
clarify and amplify this.
For each and every material, whether it be a metal, wood, plastic, glass,
ceramics or something really exotic, there is a certain amount of knowledge
that applies from the world of machining. This knowledge often goes back 50
or 80 years, for certain materials that have not changed, and a little more
knowledge is being added whenever a new material needs machining. It¹s
written down in manuals, but almost no one reads the manuals any more, and
our machining jobs have largely gone overseas.
The experienced machinist doesn¹t just drill a hole. Elements of the
decision are the material, the drill bit hardness, the angles of the cutting
surfaces (there are several angles in each bit), the speed of rotation, and
the feed rate of the bit, to mention a few. In most cases, you feed machine
oil to the bit while drilling, but there are other things that you may
apply, depending.
Certain materials that don¹t look like they will be difficult, turn out to
be real trouble for an ordinary drill bit turning at a typical speed and
feed rate. It¹s just nasty. It¹s almost like magic how everything improves
when you get the right parameters.
Here is a pretty good article on drill bits:
http://en.wikipedia.org/wiki/Drill_bit. This says a lot about twist drills,
but not everything.
Once upon a time (oooo-eee-oooo), machinists even custom-made some of their
own tools.
--Dave S. (Demitri)
On 6/23/08 6:53 PM, "Philip J Agur" <[EMAIL PROTECTED]> wrote:
> Drilling lead takes a different chip breaker angle on the bit and lubrication.
> Otherwise is going the lead is going to gall up on the cutting edges seize. A
> hammer drill is a pretty hack way of breaking up the chip. It would be better
> to find an actual machinist. Since lead is not the most common thing to
> machine expect he¹ll need to research how the drill is sharpened in the
> machinist handbook. You should also ask for RPM and cutting fluid
> recommendations.
>
>
> Phil Agur s/v Wing Tip
> <http://www.catalina27.org/public_pages/profile270.htm>
> Secretary, Call Sign WCW3485
> IC27/270A MMSI 366901790
> www.catalina27.org <http://www.catalina27.org> Vessel Doc# 1039809
> -----Original Message-----
> From: [email protected]
> [mailto:[EMAIL PROTECTED] On Behalf Of Rudolph S. Behar
> Sent: Monday, June 23, 2008 3:04 PM
> To: [email protected]
> Subject: Re: catalina27-talk: Keel bolts
>
> I tried to do it myself and ended by breaking two new and strong steel bits.
> Local yardman did the work for me. Siad it took him 7 hours. I know him and
> believe him. HE used a 3/4th hammer drill. And it cost. No problems since.
>
> If I had to do it over again I'd not partner the old bolts, but set the new
> ones (six of them) in a fresh pattern at some remove from the originals. I've
> had no problems, but it seems good sense not to be too close to the originals.
> The old bolts seemed to be ferrous. I put in stainless for the new ones.
>
> Rudy B.
> Phoenix, #2237
> Pasadena
>
> James Calleran wrote:
>
>
> Listees,
> After a, ahem, hard grounding, my Catalina smile has reappeared (last
> seen 6-7 years ago) not badly, but a thin line at the keel joint is visible
> on one side. The boatyard service manager has recommended re-torque-ing the
> keel bolts. Naturally, the yard will do the job for a fee, though I don't
> have a quote. I'm concerned about these 30 yr-old bolts breaking off under
> 60+ ft-lbs of torque.
> Any of you who have done this yourselves:
> 1. How did you clean off the accumulated rust (They were rusty, right)?
> 2. Were you able to budge the nuts?
> 3. Did you remove them one at a time, of course and clean the threads?
> 4. Did you replace with stainless nuts?
> 5. What torque?
>
> For those who have installed SS Lag Bolts in your keel.
> 1. Did you buy the $279.95 kit from Catalina Direct? (5 bolts, 1 drill bit,
> washers)
> 2. What size is the drill bit?
> 3. Did drilling require a rotary hammer type drill, or just a powerful
> standard drill?
>
> I have source of SS 1/2" x 8" SS lag bolts @ 14.95 each. Specs say 18-8
> stainless; no mention of 316. Thoughts on using these?
>
> Thanks for comments on your experience.
>
> Fair Winds,
> Jim Calleran, C27 #2784, Trad, OB
> Mathews Yacht Club, VA
> 37°27.8'N/76°18.6'W
>
>
>
>
>
