Drills

[dlane]

Hi all , I have a bunch of long drill bits some with taper ends ,several large sizes 5/8 < ,( came from GE)
Can't think of a use except boaring on lathe , too long for mill work I would think.
My go to drills are letter,#,fraction jobber size and they are useualy longer than needed on mill .
Thinking of getting a set of screw machine drill bits , any recommendations on most versatile set
# , letter , fraction , material, coatings , make , can't afford one of each .
I'll keep a few of the long ones and sell the rest , but who would need long drills 10"- 16"
Tooling budget getting low , need to get rid of things I won't need for things I need.
Any recommendations
Thanks

 

[hman]

As to who would need long drill bits - I have 12" bits in 1/8", 3/16", 1/4" and 3/8" sizes myself. Don't use them very often, but when you need one, you need one. You're right about their not being suitable for a mill. But they can be used in a drill press or a hand held drill (straight shanks only) as well as in the lathe.

I've bought letter, number and fractional sets separately over the years. I like the Milwaukee fractional set in black, have both the 1/32" and 1/64" sets. My letter set (some kind of yellow coating) is from Grizzly, bought some years ago. Don't recall where I got the number set, but it's plain HSS. My paranoia keeps me from buying one of those all-in-one sets - don't know who's good, and if you make a mistake, it's a big one. As needed, I'll replace individual drill bits with CTD (http://ctddrill.com/) ones. Pricey, but very high quality and not too painful if I'm just buying one or two.

 

[Wreck™Wreck]

DO NOT BUY SETS, if you are a hobbiyst (most sizes you will never use), buy individual screw machine length twist drills as needed. You will like the screw machine length drills
I do not drill holes at the recomended tap drill size for threaded holes, I always choose a larger drill unless I know that someone down the line will be shoving plug gauges in the hole.

Very few Customers or hobbiyists have the ability to measure such a feature. One may spend a good deal of money buying H3 tolerance 1/4-20 taps that they can not measure, if you can not directly measure it you have no idea if it is within the allowed tolerance, simply buying a Tap from a trusted source means little, without gauges you can't measure it.
This is the way it is.

 

[extropic]

DO NOT BUY SETS, if you are a hobbiyst (most sizes you will never use), buy individual screw machine length twist drills as needed. You will like the screw machine length drills
I do not drill holes at the recomended tap drill size for threaded holes, I always choose a larger drill unless I know that someone down the line will be shoving plug gauges in the hole.

Very few Customers or hobbiyists have the ability to measure such a feature. One may spend a good deal of money buying H3 tolerance 1/4-20 taps that they can not measure, if you can not directly measure it you have no idea if it is within the allowed tolerance, simply buying a Tap from a trusted source means little, without gauges you can't measure it.
This is the way it is.

Amazing (the bad information one finds on the internet). Thank you for your honesty anyway.

To all other readers, please don't do as Wreck™Wreck confesses. Recommended tap drill sizes are the result of analysis and testing beyond the scope of the typical hobby machinist. You're much better off going with the recommendations of reputable sources, regardless of whether or not you may be found out. There are cases where a slightly larger tap drill might be appropriate (such as low load fastener into pre-hardened material) but they are relatively few and far between. A general practice of violating recommended tap drill sizes is irresponsible, dishonest (if you're doing it in commerce), and illegal (if you're doing it in violation of a customer requirement).

As for not buying sets of drills, I guess it depends on your circumstances. My desire is to maximize my capacity to achieve the desired result. Having the right tool, on hand, helps me. If I want to drill a certain size hole right now, the last thing I want is to travel to buy or order and wait for the desired size. What's your time worth? What is delaying the project worth? How much would it bother you to have some $$ tied up in twist drill sizes you seldom (or never) use? How much time/gas/shipping will be spent on buying twist drills piece meal? Piece meal isn't my preference. One may not be able to own every tool but common (fractional up to 1/2", Letter, #1-#60, jobber length) drill sets are pretty basic and of great utility.

 

[Billh50]

Using a larger than recommended drill for tapping only weakens the thread. The percentage of thread drops to a point that can cause threads to be stripped in softer materials simply by tightening the screw. It is however recommended in some harder materials mainly for ease of tapping and less chance of breaking a tap. For parts that are going to be case hardened it is recommended to use both the next size drill but also an oversize tap.

Tip: When you don't have an oversize tap. Lay a rag over the hole and tap through the rag. The results will be the same as using an oversize tap.

 

[extropic]

Using a larger than recommended drill for tapping only weakens the thread. The percentage of thread drops to a point that can cause threads to be stripped in softer materials simply by tightening the screw. It is however recommended in some harder materials mainly for ease of tapping and less chance of breaking a tap. For parts that are going to be case hardened it is recommended to use both the next size drill but also an oversize tap.

Tip: When you don't have an oversize tap. Lay a rag over the hole and tap through the rag. The results will be the same as using an oversize tap.

Is that a joke? I'm going to need some additional information before I can consider that tip as anything except superstition. Why does tapping through a rag change the size of the threaded hole? How much larger will a 1/4-20 UNC GH3 tap cut through your magic rag (+.0005?,+.001?, +.0015?)? Will the finished thread size be affected by the fabric type of the rag? Is there a fabric that will allow me to get a 1/2-20 UNF-2B hole using a 1/4-20 GH3 tap?

Back to earth; I agree that post-tapping processes such as heat treating may affect the threaded hole size in the completed part and must be considered when choosing the tap/drill combination. You have to know the properties of the material and the post-tapping processes.

 

[stupoty]

I've had a mid - low price set of drill bits for a while i purchased a 2-10mm set in 1/2mm increments, very handy as a base.

Then i purchased replacements for ones that get used a lot and aditional sizes for tapping or reaming holes.

The few dormer brand drills I have are amazing, very tempted to get a set of them.

For me I dont think a whole set of letter, number, imperial and metric drills is a nessesaty but would definetly be handy (and maybe a bit expensive).

I have got a low end tap and die set, thats been very handy, again I replaced sizes I use a lot with sets of 3 (starter , through tap and bottoming tap). This has worked out well I think and the cost wasn't rediculous.

Stuart

 

[Tony Wells]

Let's not have any ridicule here.

The rag trick is one of many old timers' ways to get things done a certain way. Just because you haven't heard of it, don't knock it.

Same with the oversize drill. There is a tolerance for the minor diameter of a threaded hole, and despite all the charts, the hole size can vary and still be within tolerance. Obviously, going too large weakens the thread, but to each his own. And it's not illegal. Unethical maybe, but not illegal. And a good way to lose a customer.

Anyway.....ToS do not allow personal attacks or mockery. Consider this a warning.

 

[Wreck™Wreck]

Amazing (the bad information one finds on the internet). Thank you for your honesty anyway.

To all other readers, please don't do as Wreck™Wreck confesses. Recommended tap drill sizes are the result of analysis and testing beyond the scope of the typical hobby machinist.

I failed to make myself clear it appears, sorry about that. I drill holes for tapping at or near the ANSI Unified Screw Thread internal minor diameter standards for the thread class required.

Using a hardware store tap hole chart does not provide this information and gives but one choice. 1/4-20 for instance, the drill size will be #7 (.201), the ANSI 2B and 3B standard, Minimum Minor Dia. is .196 the Maximum Minor Diameter is .207, I would therefor choose a #6 drill (.204) which is well within this range. the added .003 can make a big difference when machine tapping difficult materials.
Here are the ANSI 2B-3B standards. They may also be found in Machinery's Handbook.
https://www.engineersedge.com/thread_strength/internal_screw_threads_chart.htm

 

[cvairwerks]

I typically use # 50, 40, 30, 20, 21, 11 and 10's the most. Generally I buy packages of 10 each in jobber, 6" and 12" lengths, as well as A,B and C length threaded. I rarely buy anything but Clevelands, as I can get them locally and priced very close to what mail order runs. I keep mostly HSS on hand but on occasion have need for cobalt bits too. Cobalt, I buy as needed. Careful use and I can make the bits last a long time.