Drill and Tap info for a idiot

[nekshot]

Would it be possible for you fellas with lots of wisdom in this area to share it and get a bank of info? This is the area I struggle with because I use alot of old military metal and some of the grain in that stuff is interesting along with the tap and drill paks I bought from ole grinning Larry at midway had the wrong drill bits in the paks! I found this out after I measured bits after some serious screwups (Larry's grin didn't help my feelings). I enjoy the stickies here on everything thats in them and would desire help in this area! Thanks and if this was done before please direct me to the info!

[joesig]

See if this is what you had in mind:

http://www.tradesmathcalculator.com/...ll-Charts.html

This may help too:

http://www.csgnetwork.com/tapdrillsizecalc.html

[country gent]

There are charts that give tap drill size for 75% threads available ( AT tool shops if you ask for one they are free. Having the proper size hole is very important. using a good cutting fluid is also important to succsefully tapping holes. Having as solid a set up is improtant also the piece locked in place with mill vise or drill press vise and tap held in chuck turning bt hand keeps flexing down. When possible start with a starting tap and only cut threads to bottom with bottoming tap as finishing. Make sure the metal isnt hardened when using scrap. a spark and or file tese can be done to determine this.

[CastingFool]

A three flute tap is easier to get started by hand, than a 2 flute tap.

[KCSO]

Either make or buy a good tap guide, (I made mine from an old V block), the straigher you tap the less breakage. A squeekig tap is going to break it's dull and is teling you don't use me. You will need taper and plug and bottom taps for a lot of jobs save your broken taper taps and grind them into bottom taps. Use a good grae of cutting oil like do drill or Magic Tap and clean the tap often as you go. Use carbide bits to cut through the surface hard on a lot of military rifles. Watch out for Mosin's as they can be soft and then go toa hard spot in a 1/4 inch. A good set of # drill will have the spec sheet for tap and drill right on the front, read it and use it.

[FLHTC]

Start with a center drill. It's extremely hard to break those. Drilling and tapping is an easy process once you know what tools to use. If you buy cheap, you'll get cheap. Rather than buy a whole set of number and letter drills, buy the ones you need for the correct tap. You'd be amazed what you can do with bench top tools and know how.

[cody9999]

This will get you real close, take the tap size and subtract one pitch.
1/4-20: 1 devided by 20 = .05, .250-.050=.200
Actual drill size =.203 or a #7.
Also works for metric only less math.

[nekshot]

This is good, I appreciate your input. I had enough sence to get tap magic, do-drill oil, a tap wrench that has a shaft to fit into drill chuck, the metal that is soft and then you hid something hard throws me out of sorts and for sure midways mis match of drill bits for taps completely thru me off, I guess I will buy only from Browenells from now on for taps and drill bits.

[cody9999]

Don't know how hard of mat'l you're trying to tap but the info I gave above is what I have used for 95% of my tapping needs. Aluminum - D-2 tool steel up to about 40 Rockwell (c scale). After that I'll increase the drill size to give about 50% thread engagement instead of 75%. This decreases the chance of tap breakage and lowers the amount of force required to turn the tap. Any increase over 75% is not worth the effort because there is no significant increase in strength but drastically increases your chance of breaking a tap. If you're looking for strength use fine threads in steel and course threads in aluminum.
Tap magic is fine for steel but for aluminum I prefer WD-40.

[Char-Gar]

In 1970, I bought the pictured tap wrench from B-Square. It mounts in either the lathe tailstock chuck (shown) or the drill press chuck. Using the correct size tap drill, drill the hole. Remove the drill bit and catch the sliding rod of the tap wrench in the chuck and the tap will go in to the drilled hole straight every time. It is big enough for any tap you will use in gun work. Use a good lubricant like Tap-Magic, go slow and back out the tap every once in a while to remove the chips. There will be no broken taps, no canted holes and no stress on the guy doing the job. I could not do without this gizmo.

[bangerjim]

Remember, when hand tapping.................you only do it about a quarter turn at a time.......back out the tap a 1/2 turn each time to clear the chips....and repeat. And use GOOD professional tapping fluid....not WD40 or 3-in-1 or motor oil!!!!!! Better to tap dry than use those! They create more metal to metal CUTTING friction than doing it dry. There is a special tapping fluid just for aluminum that works better than anything I have found.

Use your drill press (turned off......naturally!!!!!) to grip and start you taps. Straight, solid, and perfectly perpendicular. Use the chuck key straight end in the key socket hole to turn the chuck & tap until you get it good and started with gentle downward quill pressure from the handle.. Then loosen the chuck, raise the quill, and continue tapping with your standard handle. I have tapped many hundreds and hundreds of perfect holes that way and have NEVER broken a tap..........from 0-80 to 1".

bangerjim

[dragon813gt]

Can someone tell me where to find a good tap handle? None of these garbage adjustable collet handles. I need one for a throating reamer because all of my handles keep slipping They're prone to slip w/ the taps that they're designed for. A handle w/ a set screw would be right up my alley.

[akajun]

The best advice I can give you is to stop buying your taps from midway. Purchase taps from a tool house like enco, McMaster, etc. Alai purchase quality brands like ptd, Cleveland twist, or even Hertel. Finally purchase spiral point taps, they shoot the chips forward and cut way smoother than a hand tap. Be prepared to spend good money on good taps. If not, the first time you have to pay a edm to have a tap burned out if a Springfield reciever you will have blown all your saved money.
There are tap/ drill charts on the web for most of the standard sizes the formula listed above has already been done and it figured out.
Now buy good drill bits to drill those holes, again from the three brands listed above. Cheap drills often drill oversize or undersize holes .
Last , tapping has a " feel" to it. Always use two hands on the tap wrench, when the tap starts to flex and twist and feels tight. , back it out a half turn to break the chips . Also watch out for chip packing on blind holes, blow them out with a shot of air .
Most good tap fluids work well , unless you are tapping some exotic metal a quality tap fluid will work .

[skeettx]

On REAL hard receivers, I have taken a carbon center from a D-cell battery and sharpened it.
Then hooked stout negative jumper cables to the action and a 12 volt battery. The positive cable
went from the battery to the sharpened carbon center. This was touched to the spot that needed
tapping, sure did help the drilling and tapping.

[John 242]

I buy the cheap carbon steel taps from Brownells (or elsewhere) for tapping receivers. I tap a couple of holes, usually no more than three or four, and throw the tap away. These carbon steel taps are cheap, but dull quickly. At only a couple of dollars per, I order a bunch of them at a time. Since I only do a few holes and toss the tap, I'm not tempted to use the tap longer than I should. I know guys that use HSS taps on receivers. In my mind, if the tap snaps off, I'd rather deal with a plain carbon steel tap than one made of harder HSS. I could be wrong.

Around our shop, taps get used beyond the point where they should be tossed in the trash. Don't push it! Taps are cheap!

Not to high-jack the tread, but I've never used spiral flute taps, only spiral point taps. Any special considerations for using a spiral flute taps?

[John 242]

...and for sure midways mis match of drill bits for taps completely thru me off...

What were the sizes of the drill bits they supplied and what material are you tapping? What size tap are you using- 6-48, 8-40?

[bangerjim]

If you want GOOD tap handles, buy Starett!!!!!!! The best there is. No question about it. You will pay for them but they are accurate and will last several lifetimes. I have a full set of them for taps form 0-80 thru 1".

Quite buying Harbor Freight or cheeeeeep Chino garbage. You will NOT be sorry!!!!

A couple of mine are at least 90 years old and still as rock solid as the day they were made.

banger

[bangerjim]

I buy the cheap carbon steel taps from Brownells (or elsewhere) for tapping receivers. I tap a couple of holes, usually no more than three or four, and throw the tap away. These carbon steel taps are cheap, but dull quickly. At only a couple of dollars per, I order a bunch of them at a time. Since I only do a few holes and toss the tap, I'm not tempted to use the tap longer than I should. I know guys that use HSS taps on receivers. In my mind, if the tap snaps off, I'd rather deal with a plain carbon steel tap than one made of harder HSS. I could be wrong.

Around our shop, taps get used beyond the point where they should be tossed in the trash. Don't push it! Taps are cheap!

Not to high-jack the tread, but I've never used spiral flute taps, only spiral point taps. Any special considerations for using a spiral flute taps?

I recommend just the opposite........HSS or carbide taps! And they are NOT cheap!!!!!!! In over 40 years of tapping and threading all kinds of metals, I have never broke a tap. If you break one, you are doing something wrong! A dull cheap carbon steel tap will break much easier than a razor sharp HSS tap.

I have some taps that were made in the 1880's that are still razor sharp and used all the time! Try that with your cheap Brownell's or HF CS taps. You just cannot beat a precision ground thread HSS tap for clean crisp accurate threads in your work.

For intensive threading in hard metals, I use solid carbide taps. Again, if you break one, YOU are doing it wrong!

I use 2, 3, and 4 flute taps. And have them all in starting, running, and bottom formats and RH & LH forms. If you start the tap in your lathe or drill press, the number of flutes really makes no different. But use what you have.......but use it correctly and it will not break!

Same advise for drills.........buy American made! I spent over $250 on a FULL set of drills several yeras ago and the are still in the same condition as new after very hard BUT CAREFUL use. (no chucking in hand drills! I just hate to see drills with the shanks eaten up by spinning in poorly tightened drill chucks!) These drills will actually cut your fingers along the flutes if you are not careful!!!!!!!

TIN or nitriding does not really add life.....only "sales appeal". Once you sharpen the drill, all that "hardness" is gone on the cutting edges of the flutes on the end.


Keep on makin' chips!

bangerjim

[akajun]

Not to high-jack the tread, but I've never used spiral flute taps, only spiral point taps. Any special considerations for using a spiral flute taps?

Sorry brain fart , I meant spiral point. Spiral flute taps are for thread forming , I've never used them

[John 242]

Sorry brain fart , I meant spiral point. Spiral flute taps are for thread forming , I've never used them

As I understand it, there are thread forming taps, which don't cut, but instead displace metal. Then there are spiral flute taps, which do cut.
I have never used anything other than hand taps and spiral point taps, so I was curious about spiral flute taps.
I believe that spiral flute taps are used under power, as in power tapping. I've never had the opportunity to use one.

Hey Bangerjim, you make some good points. Although I haven't broken a tap off, others in our shop have. It's very possible that something was "done wrong" and that's why some HSS taps have been broke. I think especially hard receivers were blamed, but who knows, right?
I've had good success so far with my cheap Brownells taps, but I do appreciate the advice to get some carbide. I may do just that. Every once in a while we get some very hard receivers that need tapping for scope bases or whatever. We have plenty of HSS taps around the shop, but no carbide. Kind of pricey, so that might have to wait until a questionable receiver shows up.