Drilling and Tapping Hard Metal

[ridgeway]

I've removed taps from many 6 figure $$ parts...common sense as Jackie states...there is ALWAYS a way to get er done. When a
tap does break, chances are good a tooth from tap gets embedded in threads and poses a problem when you send a new tap down to clean it up...or worse going deeper. Inconel and titanium suck...

 

[gunsandgunsmithing]

If you manage to drill a hole and when you break the tap, a competent EDM shop can remove the broken tap and tap the hole, regardless hardness.

Yes, but that's a lot like reading directions....last resort. Lol! Also, there are several other options that work "most" of the time. So, it's also a last resort for that reason..and cost, too. Granted, if I had a good edm, it wouldn't be the last resort as often. Lol! In my area, I only know of one shop that has an edm than he can thread with and he gets almost $160/hr. Damn good but expensive. He might use my price scale too!! Lol!

 

[gunsandgunsmithing]

I've removed taps from many 6 figure $$ parts...common sense as Jackie states...there is ALWAYS a way to get er done. When a
tap does break, chances are good a tooth from tap gets embedded in threads and poses a problem when you send a new tap down to clean it up...or worse going deeper. Inconel and titanium suck...

Yep, but hard base material is better about it than gummy ss, for example. But it happens a lot, still.

 

[ridgeway]

Without doubt, carbide will withstand heat better than HSS. Carbide is wonderful in many ways...making it in the other hand...that's fir the birds....

 

[ridgeway]

On other hand....technology ans geometry in these new high performance hss taps are phenomenal. If I have something difficult to tap like iconel 718, ti, copper/nickel or stellite, I will grab a spiral flute Walter tap.

 

[gunsandgunsmithing]

On other hand....technology ans geometry in these new high performance hss taps are phenomenal. If I have something difficult to tap like iconel 718, ti, copper/nickel or stellite, I will grab a spiral flute Walter tap.

Yes, it's pretty amazing how far cutting tools have come in what seems like no time at all. Especially for something that seems so simple, but is far from it. When are chamber reamers gonna catch up?

 

[ridgeway]

I hear ya...Usually when you go into something unknown and thinking its gonna be simple...you will get a rude awakening pretty quick, lol

 

[gunsandgunsmithing]

I hear ya...Usually when you go into something unknown and thinking its gonna be simple...you will get a rude awakening pretty quick, lol

Yep...every time.

 

[GLO123]

Slow you drill bit down. I think you are burning the bit with the high speed. Soak the bit in cutting oil while drilling and don‘t put so much pressure on the drill it. Think about the tiny area of the drill bit that actually is doing the cutting. When you force the bit to cut too much you will burn out the bit almost immediately. Go slow and lightly apply cutting force, bathe the bit in cutting oil not just normal oil but cutting oil.

 

[hoz53]

I hear ya...Usually when you go into something unknown and thinking its gonna be simple...you will get a rude awakening pretty quick, lol

thats for sure

 

[Steve Blair]

Yes, but that's a lot like reading directions....last resort. Lol! Also, there are several other options that work "most" of the time. So, it's also a last resort for that reason..and cost, too. Granted, if I had a good edm, it wouldn't be the last resort as often. Lol! In my area, I only know of one shop that has an edm than he can thread with and he gets almost $160/hr. Damn good but expensive. He might use my price scale too!! Lol!

I take your point, but I live in San Diego. While EDM is not cheaper here, we have quite a few shops from which to choose. Sometimes they can be accommodating if you let them do it on their schedule. Not fast, but a little cheaper.

 

[Dusty Stevens]

I think you can buy a tap burner edm for around $1500. I wish i had a friend with one

 

[338 Mollett]

I'm quite sure my guy's have a micro edm to burn that right out.

 

[Dusty Stevens]

I'm quite sure my guy's have a micro edm to burn that right out.

Im sure they do. Most machine shops have them

 

[gunsandgunsmithing]

I've got to look into these tap burner edm machines. I've seen times I'd give that much to get a broken bolt out. Lol!

 

[Rick H.]

I am resurrecting an old thread because of something I just encountered and would like to throw it out to the group. I am not a machinist although at times I wish I was. I do have a small Grizzly knee mill which while not terribly accurate is quite useful for work that I do which is limited in nature. I really bought the mill for drilling accurately located holes and threading them. So here's my story....

I wanted to drill two holes and thread them on a Randolph rest top plate. I thought this would be a relatively easy job until I got into it and was surprised at how hard the steel top plate was. Drilling the holes wasn't too bad, but threading them was a different story. I drilled the first hole and wanted to tap it before I moved the work piece to a different location. I started tapping using a HSS 10-32 tap on a Starrett B tap handle located with a tap handle "pin" in my mill with cutting fluid manually applied during the process. I got about 3/4's of the way thru the plate and going got pretty tough, but the tap was turning, but very slowly.

At this point I felt and heard two "snaps". The first snap was what I believe the tap slipping in the tap handle and the second snap was the tap breaking. My first thought was the same as everyone else when you hear a snap under these circumstances and then the "now what do I do" moment. The tap handle I used was old and no doubt should have been replaced a long time ago, but it never slipped like this before. I am not one to venture into doing things I haven't at least seen done before, so my first thought was to find a shop with a EDM tap burner and pay the price for their work. Problem is, who do I go to for this work and who does it? After some quick research I learned not many shops advertise being able to EDM a broken tap out in my area.

So I set the work piece aside and pondered my situation. I then had a brainstorm and called a tool and die guy I know and explained my situation to him and asked him if he knows anyone that could EDM this tap out. He asked me what the tap was made of and after I told him he asked me if I had any really good small mill bits for my machine. I said perhaps a couple that I got from an estate sale a few years ago. He said if I have a 1/16" sharp mill bit to put it in my mill and carefully center up the hole with the broken tap in it. Then he went on to tell me how he would try and remove the broken tap by pecking at it with firm pressure using the knee with a locked quill. He never mentioned drill speed and I never asked him about it. My cheapo Grizzly mill has a less than accurate knee adjustment on it, so I decided to try this operation with just getting very close to the work piece with the knee and using the quill lever to give me better control of movement and "feel".

I followed his advise and proceeded to start pecking at the broken tap gently at first to see what would happen. I was surprised that the mill bit started cutting the broken tap and I was at about 700 RPM for speed. Once the jagged end of the tap was cut away I needed slightly more force on the lever to get better cutting action and I continued pecking at the tap until I was almost all the way through it, then the unthinkable happened....the 1/8" mill bit broke!! I couldn't believe my rotten luck! Now I had a broken tap and an end mill in the hole!! D**N!!

In frustration I took the work piece out of my mill vise and looked at it and noticed from the bottom of the plate I was working on that end of the tap seemed loose! Then I thought I wonder if it will punch out of the hole from the back side and it DID! I cleaned out the hole and noticed that even for eye-balling proper placement of the work piece the threads I had cut before the tap broke were for the most part intact. After cleaning out the hole I placed it back in the mill vise and inserted a new tap and using a new tap handle proceeded to slowly and as gently as possible complete tapping the hole in the top plate. I did my Happy Dance at that point!

Was it luck I was able to do this or maybe a little bit of skill too? I don't know, but I was quite surprised that an estate sale end mill was able to cut thru this broken tap and get me back in the game with completing this little project. I didn't think about my spindle speed while doing this until I started actually cutting the broken tap and I just let the speed alone as the end mill WAS cutting the tap. I will add that I used quite a bit of cutting fluid while doing this and perhaps that helped too.

So even a blind squirrel can find a nut now and then, but I did read this thread before I called my tool and die maker friend. I was more confused about spindle speeds and drill/tap compositions after reading this. High drill speed? Low drill speeds? High speed steel taps?, Carbide taps? The information is endless, but what is really right or the best way to go?? Was my experience milling out a broken tap pure luck and just how DO you tell someone how much pressure should be put on a drill or end mill bit? I am still in the dark on this whole issue. As I see it I was fortunate in relocating my work piece to almost the exact same spot to mill out the broken tap. I was plain stupid for continuing to use a worn out old tap handle that should have been tossed a long time ago. I would not want to attempt this type of work without using a true milling machine, even a cheap(er) one. The risk is not worth the effort. Now if I could just get it straight in my head on what the best drill speeds are and what material composition is best for doing this type of work I will be all set.......maybe. Now if Santa would bring me a tap burner.....

Rick H.