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03-06-2020, 04:08 PM
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#1
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Senior Member
City: Russell NZ
Vessel Name: MV Unique
Vessel Model: Salthouse Coastal 35
Join Date: Jul 2013
Posts: 207
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Drilling Stainless Steel
I need to drill a 30mm hole through a 4mm plate without the result looking like a beaver had a go at it. Tungsten Carbide or Titanium tipped/coated saws, wil either do it or is one better than the other. Cheers
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03-06-2020, 04:41 PM
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#2
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
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Join Date: Jul 2015
Posts: 21,185
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That is a big hole. When I drill S/S i usually use cobalt bits and go slow with a lot of pressure and lots of cutting oil so it doesn’t get hot.
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03-06-2020, 05:31 PM
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#3
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Guru
City: Los Angeles
Join Date: Feb 2020
Posts: 1,487
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Try to find a TiNi step drill - a la Unibit - and the biggest pilot you can in cobalt or carbide.
A cobalt bit that size will be spendy but work.
If you have access to a quality drill press with a vise you could use an adjustable bit
with a carbide insert.
A machine shop would probably just use a punch press.
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03-06-2020, 05:33 PM
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#4
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Moderator Emeritus
City: Au Gres, MI
Vessel Name: Black Dog
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Posts: 21,185
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Or maybe take it to a machine shop. It might be about as cheap as buying a special bit for a one time deal.
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03-06-2020, 06:05 PM
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#5
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Guru
City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
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I’m with Comodave.
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Eric
North Western Washington State USA
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03-06-2020, 06:20 PM
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#6
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TF Site Team
City: California Delta
Vessel Name: FlyWright
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I wouldn't attempt it without a drill press. I had the good fortune of having access to our machine shop at the airport so the mechanics were a great help in building my windlass/pulpit components.
Like Comodave suggests, find a local machine shop. Easy job for them. Same goes for polishing SS plate.
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03-06-2020, 09:51 PM
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#7
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Guru
City: Los Angeles
Join Date: Feb 2020
Posts: 1,487
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4 mm = less than 3/16"
30mm = about 1 3/16"
Nothing I wouldn't tackle on my Chinese drill/mill with a Unibit.
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03-06-2020, 10:56 PM
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#8
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TF Site Team
City: Saltspring Island
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The key is slow turning bits and lots of cutting oil. Then a cut that without the proper care would get hot and never be accomplished, will be like cutting through butter.
I know this after mounting my davits, 1/2" holes in 1/4" material.
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Keith
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03-06-2020, 11:07 PM
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#9
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Guru
City: Sidney BC Canada
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03-06-2020, 11:56 PM
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#10
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Guru
City: San Francisco
Join Date: Apr 2018
Posts: 3,093
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You can do that with a hole saw, even a high speed steel one. Getting enough pressure on it to cut is the key, your own weight on a drill motor will not be enough. A HSS annular cutter like is used in mag drills would be ideal. Or a machine shop. A hole like that can be interpolated on a CNC mill in about 30 seconds, and it will be round and on dimension.
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03-07-2020, 02:21 AM
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#11
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Guru
City: Kenai, Alaska
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Quote:
Originally Posted by DDW
You can do that with a hole saw, even a high speed steel one. Getting enough pressure on it to cut is the key, your own weight on a drill motor will not be enough. A HSS annular cutter like is used in mag drills would be ideal. Or a machine shop. A hole like that can be interpolated on a CNC mill in about 30 seconds, and it will be round and on dimension.
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I have seven holes through my 1/2" 316 SS stern plate that size, done with a hole saw and an oil can with cutting oil to keep it lubricated. Slow drilling, keep your drill speed low as well, but it will leave a nice clean hole.
One thing I did do, was after drilling the pilot hole, turned the bit around in the can so it didn't wallow out the pilot hole while drilling for such a long time. Milwaukee cans, nothing special about them, got multiple holes per can before they went dull.
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03-07-2020, 04:06 AM
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#12
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Guru
City: Oconto, WI
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That's a little over an inch, the Milwaukee hole saws with hardened teeth , slow speed and lots of oil will cut right through. A press will be best because if the hole saw "bites" with a half inch drill it will rip your arm off.
pete
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03-08-2020, 07:37 AM
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#13
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Guru
Join Date: Oct 2007
Posts: 22,553
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"Getting enough pressure on it to cut is the key,"
YES
Ask around , somewhere there is a drill press you can use for 5 min.
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03-08-2020, 08:20 AM
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#14
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Technical Guru
City: Wilmington, NC
Vessel Name: Louisa
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Join Date: Jan 2014
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Machine shop. Might charge you 40 bucks and won't make a hash out your plate.
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03-08-2020, 12:19 PM
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#15
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Guru
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
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Drill a small hole first, then use a knock out punch, 30mm shown. $15 on Amazon. It leaves a professional looking hole. Drill a series of holes until the bolt will go thru.
As others said, when drilling ss, lube, light pressure and don't force the bit.
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03-08-2020, 12:34 PM
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#16
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Guru
City: Gulf Islands, BC Canada
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Quote:
Originally Posted by Phil23
I need to drill a 30mm hole through a 4mm plate without the result looking like a beaver had a go at it. Tungsten Carbide or Titanium tipped/coated saws, wil either do it or is one better than the other. Cheers
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A lot orf good advice for a piece of stainless not already attached to the boat.
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SteveK
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03-08-2020, 12:43 PM
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#17
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Guru
City: Alexandria, VA
Vessel Model: 2000 Wellcraft
Join Date: Sep 2013
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Personally, I have found using oil on the bit, to make a lot of difference, when trying to drill stainless.
But, I agree, that sometimes, it can easier to just take it to a professional, and say "drill this, please".
I grew up on a farm, and we were constantly taking broken bits of equipment to the welders for repair. I asked my dad once, why we didn't just buy some welding gear.
His response was, you can buy yourself a welder, but you can't buy yourself twenty years experience in knowing how to use it.
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03-08-2020, 12:52 PM
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#18
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Guru
City: Long island
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For some reason people think SS is hard. It is actually very soft. That’s why SS screws strip so easily. It only gets hard with heat. Keep everything cool and you are ok to use a good hole saw. If you want it perfect you must undersize it then rotary file it. Most hole saws wobble a bit
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03-08-2020, 12:53 PM
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#19
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Guru
City: .
Vessel Name: GOTCHA
Vessel Model: Hatteras 58 LRC
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Posts: 1,103
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Try a 35 deg drill at 12-14 RPM.
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03-08-2020, 01:09 PM
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#20
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Guru
City: Miami Florida
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Quote:
Originally Posted by Arc
For some reason people think SS is hard. It is actually very soft. That’s why SS screws strip so easily. It only gets hard with heat. Keep everything cool and you are ok to use a good hole saw. If you want it perfect you must undersize it then rotary file it. Most hole saws wobble a bit
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Stainless is strange to drill. You can be drilling with no problem and suddenly the stainless will harden and become undrillable.
I don’t know if it work hardens or heat hardens but it happens fast with no warning. I’ve drilled a lot of stainless and had it happen rarely but it has ruined a few pieces for me. Might be my fault, I tend to grab what ever oil is handy. Maybe a better cutting oil would have prevented the problem.
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Retired from Hopkins-Carter Marine Supply
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