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Could some kind person give me an opinion on drilling stainless please?

simonh

Plastic
Joined
May 18, 2023
Location
Australia
Hi All,
I am a bit of a newbie and still learning, for sure. I wand to drill into round stock on the lathe and I am after an accurate hole that I will insert a shaft into. The shaft is half inch or 12.7 mils. I have a reamer of that size so just wanting to know what size drill bit to use please?
Thanks very much to all.
Simon.
 
Hi All,
I am a bit of a newbie and still learning, for sure. I wand to drill into round stock on the lathe and I am after an accurate hole that I will insert a shaft into. The shaft is half inch or 12.7 mils. I have a reamer of that size so just wanting to know what size drill bit to use please?
Thanks very much to all.
Simon.

I like to leave 0.007" - 0.015" in the hole for reaming. When you are working with stainless, do not let it get too hot or it will work harden.
 
If 'accurate' refers to position, straight, or concentric with the stock, a twist drill is just a place to start. Depending on the depth of the hole, the grind on the drill and your technique, the hole will most likely wander as you go deeper. If accuracy in the mentioned areas is required you need to start with the drill then bore the hole.

You didn't say which stainless you have, but make sure you don't spin too fast, use lots of cutting oil or high lubricity coolant and keep the cut going! You can peck, but don't dwell even for a second in the transition from infeed to outfeed.
 
If it is 303 SS, leave about .005-.010 or so. If it is 304/316 SS you will want to leave a little more material so it doesnt "rub" and work harden. I would leave more like .010-.015 or so with 304/316.

I dont know how deep you hole is, but getting chips out of the way will be a problem.
 
I'm assuming you are on a manual lathe, so in an out sliding the tail stock to clear the chips quickly. When advancing the quill, you are either winding into the material or reversing back out.
Don't stop or let the drill slide without cutting or the piece can work harden.
Use a new or sharp cobalt hss drill, that's going to cost you A$50 down here.
Look up a milling chart for RPM in SS for a 12mm cutter and the chip load for a 2 tooth cutter. That will tell you how fast to advance the tailstock quill.
Practice by timing the feed rate without cutting so you learn how fast to turn.
Be confident and firm with the feed, following the feed rates, rpm and chip clearing.
Use cutting oil or a specialist fluid like tapmatic. If you can't lube and feed at the same time, get a helper or drill dry. No dwell is more important than coolant, at the expense of drill life.
 
The shaft is half inch or 12.7 mils. I have a reamer of that size so just wanting to know what size drill bit to use please?
The thing I would do is not use a reamer.
Drill hole under size to 7/17/ Then bore to whatever custom fit you want.
 
An aside: The term "mil" has historically been used as a shortened variant of "millinch" (0.001 inch), especially in the sheet-stock and electronics industries.

I strongly discourage using "mil" or "mill" as a shortened form of "millimeter", and equally strongly encourage questioning any use of "mil" to verify the user's intent.

For similar reasons I discourage use of ' and " in written communications, as the same ' is commonly used to specify 1) feet, 2) minutes of time, 3) and minutes of arc. Similarly, " is commonly used to specify 1) inches, 2) seconds of time, and 3) seconds of arc.
 
Thanks John. Beat me to it on the "mil". I don't think anyone would think "millimeter" when that term is used.

The use of single and double quotation marks for feet and inches is fairly common and that meaning can usually can be understood from the context. For instance, drawings commonly use those symbols to show inches and feet AND minutes and seconds of arc. The type of dimension usually makes it obvious which meaning is intended. But it would be better to avoid them if there is any chance of confusion.

In an area of knowledge like machining where there is a real need for precision in not just things like physical measurement, but also in other, more cerebral concepts, there is a real need for using precise language.

On making that 1/2 inch hole in SS, I think I would use the reamer unless there is a real need for great precision. To my way of thinking, using a boring bar in a boring head for such a small size is going to be challenging. Sure, it can be done, but you may need to grind extra clearance on a stock boring bar and that extra clearance will need to extend for the full depth of the hole.

Just saying that you have a reamer that size does not address the fit of the shaft. And you do not say what type of fit is needed. Reamers are generally available in 0.001" increments. In addition, you can get "over" and "under" sizes for, at least, the round number values like 1/2". Without looking I would guess that there are stock reamers in 0.0001" increments from 0.4990" to 0.5010". And perhaps even sizes between those small increments. Shafts also can vary in size and then there are tolerances.

You need to consider what that shaft is going to do in that hole before you can choose the proper diameter shaft, tolerance, and reamer size or the size that a boring head would be set to.



An aside: The term "mil" has historically been used as a shortened variant of "millinch" (0.001 inch), especially in the sheet-stock and electronics industries.

I strongly discourage using "mil" or "mill" as a shortened form of "millimeter", and equally strongly encourage questioning any use of "mil" to verify the user's intent.

For similar reasons I discourage use of ' and " in written communications, as the same ' is commonly used to specify 1) feet, 2) minutes of time, 3) and minutes of arc. Similarly, " is commonly used to specify 1) inches, 2) seconds of time, and 3) seconds of arc.
 
If you look at the posters location you will see Australia, its common to refer to millimeters as "mils" here. Unless you are on a shooting range where they will be referring to milliradians at which point I will raise my eyebrows as they will probably be some wannabe wanker with a tactical setup.
 

"simonh" PM me with your number if you need me to talk you through the process, I am based in Sydney.​

 
If you look at the posters location you will see Australia, its common to refer to millimeters as "mils" here. Unless you are on a shooting range where they will be referring to milliradians at which point I will raise my eyebrows as they will probably be some wannabe wanker with a tactical setup.
In metric countries mills, or millis as they say where I am, are well understood, they also use centimeters a lot here and it gets shortened to cent(s).

Flood coolant when dealing stainless has been a godsend btw.
 
If you look at the posters location you will see Australia, its common to refer to millimeters as "mils" here. Unless you are on a shooting range where they will be referring to milliradians at which point I will raise my eyebrows as they will probably be some wannabe wanker with a tactical setup.
You aussies. Different location different meaning. I heard Lucy Lawless tell about an american telling her she had a nice fanny. She was a bit flustered.
 
If 'accurate' refers to position, straight, or concentric with the stock, a twist drill is just a place to start. Depending on the depth of the hole, the grind on the drill and your technique, the hole will most likely wander as you go deeper. If accuracy in the mentioned areas is required you need to start with the drill then bore the hole.

You didn't say which stainless you have, but make sure you don't spin too fast, use lots of cutting oil or high lubricity coolant and keep the cut going! You can peck, but don't dwell even for a second in the transition from infeed to outfeed.
To which I'd add that the rule I learned was spin slow, press hard, and don't stop. The intent being to always cut under the work-hardened surface left in the prior rotation. And use lost of coolant, which must be or contain a heavy oil.
 
they also use centimeters a lot here and it gets shortened to cent(s).

i worked in several English Machine shops and Engineering companies, never heard or read the term cent(s), not say it doesn't get used I've just never seen or heard it (I'm from the UK)

Of course not having worked in the UK for 35 years, what do I know?
 
An aside: The term "mil" has historically been used as a shortened variant of "millinch" (0.001 inch), especially in the sheet-stock and electronics industries.

I strongly discourage using "mil" or "mill" as a shortened form of "millimeter", and equally strongly encourage questioning any use of "mil" to verify the user's intent.

For similar reasons I discourage use of ' and " in written communications, as the same ' is commonly used to specify 1) feet, 2) minutes of time, 3) and minutes of arc. Similarly, " is commonly used to specify 1) inches, 2) seconds of time, and 3) seconds of arc.

While it was obvious what the OP meant in his first post I would otherwise agree with you.

------------------------------

I trained somebody who would call a Bridgeport and Endmill, and an Endmill a Bit.

Tried to impress on him you have to be precise with your terminology otherwise depending on the context somebody may not understand what your talking about.
 
It's one of those things that's just different between regions of the world. I hear mils and the first thing I think of is the guys that do film thickness measurements, like paint or coatings. Here in the U.S. that is pretty much always used as John mentioned - to refer to thousandths of an inch. I can easily understand how it would be used as a shortened term for millimeters in the fully metric countries though. Oh, and it also brings to mind the "tactical" wanks like the mystery man mentioned.
 
The manufacturing world is rife with ambiguities and strange names, mostly location specific. I threw in a few other local isms.

New Zealand "the land of no vowels"
  • Support pillar in an injection mould called a dump.
  • Slide called a wedge.
  • Cutting torch called a gas axe.
  • A cooler box called a chilly bin, pronounced chully bun.
  • Thongs on the feet not your ass crack called jandal's, abbreviated from Japanese sandals.
  • Shifting spanner called a crescent.
  • A hot dog is a sausage deep fried in batter. You should have seen the look on the face of the customer who was from the US when he received his order.
  • People are called cuz for cousin.

Australia
  • The above chully bun is called a esky.
  • Roughing cutter called a HMR cutter (High Metal Removal), in other countries its called a ripper.
  • A lot of tool rooms talk in microns, usually when they can't actually work to them. Instead of saying "point O one or one hundredth " which normally means 0.01mm they will say 10 microns.
  • O gets added to everything. Service station is a serv'o. Bottle store is a bottle'o John is John'o and the list goes on.
  • 750ml beer is called a long neck.
  • People in New South Wales drink beer in schooner's and Victoria has pot's.
  • Everyone is called mate.
South Africa "the other land of no vowels"
  • HMR is called a Strassman cutter from the brand name.
  • Facemill's are often called Rose cutters.
  • All turret milling machines are referred to as "Bridgeport's".
  • Felt tip markers are called Koki pens, must have been a brand name.
  • And if you speak Afrikaans it gets really confusing.
  • A lot of people on the east coast add "ek se" to the end of sentences which is Afrikaans for "I say".
  • Traffic lights are called robots.
  • Indicators are flickers.
  • Thongs on your feet are called slops.
  • Traffic roundabouts are called traffic circles.
  • If you come from the east coast a beer is "Tshwala" Zulu, should actually be uTshwala.
  • On the east coast everyone is called "bru" pronounce brew.
China
  • When the supplier says that they are going to open a new mould it means pull out the Vaseline and grab your ankles because the modification you requested is not possible and you are about to be raped for the price of a new mould.
  • When you tell a factory you will be visiting on a particular day they often agree, when you arrive in China you find it's a public holiday. You need to be very specific and take nothing for granted as far as them understanding the hidden meanings in questions.
  • When you say I would like a plating thickness of 0.25mm plus or minus 0.05mm you can stake your life on it that the thickness will be exactly 0.2mm and the suppliers wife will be wearing the the silver that they saved in the form of jewellery.
  • The Chinese script on your take away coffee cup at Starbucks doesn't say tall, dark handsome man. It says 外国人 (Wàiguó rén) which means foreigner because you stand out like a pair of dogs balls.
  • EG could probably add to the list for China.
 
It's one of those things that's just different between regions of the world. I hear mils and the first thing I think of is the guys that do film thickness measurements, like paint or coatings. Here in the U.S. that is pretty much always used as John mentioned - to refer to thousandths of an inch. I can easily understand how it would be used as a shortened term for millimeters in the fully metric countries though. Oh, and it also brings to mind the "tactical" wanks like the mystery man mentioned.
I like to be mysterious, actually I don't want some of my customers and suppliers knowing what I post.

For instance if I post my opinion and experiences with a particular brand of machine tool and the local supplier I don't want to be burnt when I try to order spares.

I'll fill you in just so I'm not that mysterious.
First apprenticeship was as a military armourer.
Spent 5 years in the military full time and another 8 years part time which in my case meant anything from 1 to 3 months every year most of it in the operational area hence my dislike of wannabe tacticool wankers.
Second apprenticeship was as a tool, jig and die maker.
I have worked in most industries from automotive to medical working in tolerances from centimeters to microns.
Worked in multiple countries.

To sum it up I am a standard toolmaker, opinionated and grumpy.
 








 
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