trouble drilling deeper dimples into prop shaft

[hydrodane]

100+ on this: Do yourself a favour and get a carbide bit drill if you can. Will work much better than a cobalt drill for s/s.

additionally, it is almost certain you will need to have a press drill with carbide bits AND cutting oil.

three reasons:

carbide is very brittle..but will cut through just about anything...hardened or not...it is what is used in almost any commercial setting where hardended steel and SS is the target.

because it is brittle, you MUST maintaint a very straight and consistent alignment to your work...if you flex the bit, it will shear...easily even.

a press drill helps keep this alignment AND a consistent amount of force on your work. It also free up your other hand to liberally apply cutting oil and/or directing a strong light so you notice when the metal shaving start showing...or when the metal starts "cooking"..metal shavings tell you when you have the right pressure and temperatures....the "cooking" tells you when things are getting too hot...keep that cutting sauce liberal at all times...let the but do the work....

tips: go slow...max 500 rpms ...start slower than this...speed produces heat...lots of it..you want to cut your metal, not melt it. You start to cook ss and your expensive carbide bit is now useless, and virtually no way to sharpen. Slow and steady pressure on the press...increasing slowly until you start seeing the first slips of cut metal. That is the force you continue with...and no more. and keep the oil liberal...not on and off..if you can use a drip method..nice and steady...increase press pressure until you start to see those cuttings..that's how you do it.

for additional protection, it might be wise to install a depth collar press...as said before, things can happen very quickly once you start cutting.

note: You can cut ss with cobalt or even tungsten , titanium, and yes it is possible to use high speed standard steel bits...but all of them require an incredible amount of pressure to work properly..and you will lose cutting edges very fast when you do. you will tend to see a high number of them wear out pretty rapidly, esp with SS. You might think that the higher cost of carbide is prohibitive, until you consider the number of cuts you make and the number of other lessor bits that you will go through to complete the entire project. I consider it an investment well worth it..
last comment: there are a wide variety of bits marketed as "carbide"...some are 100% carbide, other are just "tipped"..same thing with cobalt...in my experience the tipped stuff is generally garbage when it comes to cutting hardened steel or ss. pay the little extra for the real stuff. They last a good long time as long as you keep them low temp and low speed...don't rush the work..I have a set of carbides that are over 7 years old...can pop ss like day 1...or very close.

[asahi]

Originally Posted by UNCIVILIZED

What alloy of stainless is the shaft?

No idea


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[HappyMdRSailor]

Originally Posted by skipmac

I've had luck using a tungsten carbide grinder bit to break a work hardened surface in SS. You can also get a diamond bit for a Dremel to do the same thing. Then start over.

Yes, very slow speed and high pressure is the way. Don't have a rpm counter on my drill but looks like 50-100 rpm max when I hand drill holes in SS.

Originally Posted by asahi

Thank you for all the responses.

Yes, the shaft is SS. I see now that I must have work hardened the spot and likely dulled my cobalt bits in the process.

I think I'll get some new bits and try in a new area.

asahi...

Doing the Dremel route like skipmac pointed out is going to make life a TON easier... If you feel the desire to go deeper with the "dimple" using a bit, follow the above advice afterwords...

[Celestialsailor]

Now from a Machinist....Who ever said use a left hand drill bit, I laughed my butt off on that one. It cannot harden directionally.
First...make sure you're spinning the drill the right direction. Secondly use any oil as suggested. Next, use moderate to heavy pressure.
Please...no offence...but you should not use a carbide drill in a hand drill. It will shatter really quick...then you are really screwed getting that out. When a person says work hardened. It really is not that hard... Maybe 45-48 Rockwell. A (new) cobalt drill should break right through it.

[Reefmagnet]

Originally Posted by Celestialsailor

Now from a Machinist....Who ever said use a left hand drill bit, I laughed my butt off on that one. It cannot harden directionally.
First...make sure you're spinning the drill the right direction. Secondly use any oil as suggested. Next, use moderate to heavy pressure.
Please...no offence...but you should not use a carbide drill in a hand drill. It will shatter really quick...then you are really screwed getting that out. When a person says work hardened. It really is not that hard... Maybe 45-48 Rockwell. A (new) cobalt drill should break right through it.

Carbide drill bits have carbide cutting teeth only, the same as a masonry bit. The rest of the drill is HSS. What makes you think they will shatter? That certainly hasn't been my experience and I use them predominantly in hand drills. I'd also remark that using "any oil", whilst better than nothing, is inferior to a purposely formulated cutting oil on difficult to drill materials.

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[Cadence]

I'm sure a knowledgeable machinist can probably do it with no effort. I had an old man build me a rudder of stainless as I recall 3' X 2.5'. Hole in the bottom of a SS shaft for the pintal top of the shaft squired for an auxiliary tiller. All I had was a rough drawing. Sometimes experience works.

[brianlara 3]

Asahi. Your cobalt bits MUST be sharp enought to easily cut the skin on the inside of your wrist.
Massive body weight pressure, leaning over the drill with as much weight as you have but be prepared for a crash if you break the bit. Ultra slow, massive pressure and super new Cobalt bits, you should have no trouble. And at first lube oil isnt/ shouldnt be necessary as the drillings will be cold metal and not require the heat transfer of oil, I think. Be careful, wear good leather gloves.
Brian

[Celestialsailor]

Originally Posted by Reefmagnet

Carbide drill bits have carbide cutting teeth only, the same as a masonry bit. The rest of the drill is HSS. What makes you think they will shatter? That certainly hasn't been my experience and I use them predominantly in hand drills. I'd also remark that using "any oil", whilst better than nothing, is inferior to a purposely formulated cutting oil on difficult to drill materials.

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More misinformation...

#1-#60 Solid Carbide Drill Bit Set | DrillsandCutters.com

What make me think it will shatter?....36 years as a Toolmaker, Machinist and Field Engineer...and you?

[Celestialsailor]

Originally Posted by UNCIVILIZED

What alloy of stainless is the shaft?

For the last 30+ years Aquamet 22 has been used. It is a higher strength with a higher alloy than say 316, 17-4 0r 18-8. It tends to pit and crevice less also. In fact the tensile strength is greater than regular SS allowing you to use a smaller diameter.

[Reefmagnet]

Originally Posted by Celestialsailor

More misinformation...

#1-#60 Solid Carbide Drill Bit Set | DrillsandCutters.com

What make me think it will shatter?....36 years as a Toolmaker, Machinist and Field Engineer...and you?

...Hundreds if not thousands of drilled and tapped holes on site. But not that that's important



ARTU USA

[brianlara 3]

Celestial. Im 69 years old, started motor body building apprenticship age 16..building tourist coaches, family business hundreds of employees, 9 toolmakers alone, 200 ton presses etc.
At age 19 wanted out, wanted to be a mechanic. Lost 18 months seniority..became a mechanic but left work aged 42 as a Mercedes Benz service manager in Sydney. (stopped work due to war neurosis..vietnam)
As you can guess, ive done and seem heaps BUT IMHO, if ANYONE ever doesnt take your advice as 'the quintessential' expert then they are fools. Dont know you, need to know you, dont give a damn what people think of my rant....YOU are one of the few real professionals Ive come across in CF...giving worlds best engineering practice ....to help others and you do it for free.
Dont know if youre a good guy or a bastard. But i DO know, people should listen to ya.

[leftbrainstuff]

Originally Posted by asahi

I'd like to drill the prop shaft dimples deeper, but I don't seem to be making much progress. I'm drilling at 1/2 speed with cobalt bits, dipping them in water to keep them cool, but even with a 1/8" bit I'm not getting much metal shavings coming off. Maybe my bits are burnt out? Any ideas?

You need to drill at the proper speed otherwise you'll just work harden the material and blunt the drill bit.

30 metres /minute is the ideal cutting speed for steel. Assuming 316 or 4xx this will be about right.

If you're drilling by hand then you wont usually be able to achieve the right level of pressure at this cutting speed. You need to use a drill press or mill with a nice rigid clamp or vice.

Also dont bother with coated drill bits. They are useless for metal. Use good quality high speed steel. Sharpen them appropriately. 135 deg included angle and 7 - 9 deg relief will work well for most iron based metals.

If you keep blunting them then reduce the cutting speed slightly, reduce the feed rate, use a good cutting lubricant and sharpen often. If you've work hardened the material you'll need to grind it back or anneal it. Much easier to drill it right first time.

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[Celestialsailor]

Originally Posted by brianlara 3

Celestial. Im 69 years old, started motor body building apprenticship age 16..building tourist coaches, family business hundreds of employees, 9 toolmakers alone, 200 ton presses etc.
At age 19 wanted out, wanted to be a mechanic. Lost 18 months seniority..became a mechanic but left work aged 42 as a Mercedes Benz service manager in Sydney. (stopped work due to war neurosis..vietnam)
As you can guess, ive done and seem heaps BUT IMHO, if ANYONE ever doesnt take your advice as 'the quintessential' expert then they are fools. Dont know you, need to know you, dont give a damn what people think of my rant....YOU are one of the few real professionals Ive come across in CF...giving worlds best engineering practice ....to help others and you do it for free.
Dont know if youre a good guy or a bastard. But i DO know, people should listen to ya.

Oh Brian, please...let me remove any doubt in your mind, the mind of others and all the stainless drilling world. I am unequivocally a bastard!

[brianlara 3]

Sit down Mate this going to hurt. Id already contacted many of your friends before my post.
I was full of crap....have known you were a bastard for ages. But a clever bastard .

[Reefmagnet]

Originally Posted by Celestialsailor

More misinformation...

#1-#60 Solid Carbide Drill Bit Set | DrillsandCutters.com

What make me think it will shatter?....36 years as a Toolmaker, Machinist and Field Engineer...and you?

Ok just to clarify, this is what I was referring to:



http://www.suttontools.com/products/...d-length-d610/

I was wwwwwrrrrrrr....wrrrrrrrrrrrrrrrrrr....wrong in calling it a carbide drill bit. It seems the correct name is "multi-purpose" drill bit.

99.9% of the time I just use good old' fashioned HSS drills when drilling 304 / 316 grades of stainless always with cutting lube. However, one time not that long ago I was disassembling a 30 year old Yamaha outboard and a 6 mm stainless steel stud snapped on the side of the block due to dissimilar metal corrosion. Needed to drill it out. Tried a new HSS drill bit and it bounced off. Tried a new cobalt drill bit and it bounced off too. Tried a carbide tipped "multi purpose" drill and not only did it cut through the stud like butter it gave so much control that I was able to drill the stud out with no damage to the alloy threads whatsoever. You know how difficult that is to do, especially by hand with a cordless drill. To say I was impressed is an understatement.