Serious drill bit purchase help!

[brino]

Help me out here guys...any ideas what I did that cause the fatal failure?

What's the combined run-out on the machine and chuck?
If it was sweeping a circle, I could see that......
-brino

 

[GunsOfNavarone]

What's the combined run-out on the machine and chuck?
If it was sweeping a circle, I could see that......
-brino

I was using an collet directly in quill, it’s very little (at least, not enough to ‘splode a brand new, cobalt drill bit. It was cutting really smooth/easy up to that point. I think it’s like @mikey said...just a bad bit/fluke.

 

[Janderso]

I use drill hog for hand drilling, Chicago Latrobe, and Norseman for the machines. That's my setup.

+ 1 on Norseman

 

[Janderso]

I've been in this hobby for a very long time and have drilled, reamed and bored in most materials a hobby guy is likely to encounter. In all this time, HSS drills in 118 degree points have served me well. I have, but rarely use, my cobalt drills and since I tend to center punch or spot drill my holes, I don't have a strong need for 135 degree drills (although I own them). I drill stainless often and a sharp HSS drill handles it fine; it is more about speeds/feeds, lubricant and technique than the drill material.

Do not think that a cobalt drill will drill all holes successfully without a brain in YOUR head. Cobalt merely handles higher temps better than M2, that's all. You still have to use the right speeds and feeds. Also, there are times when screw machine drills are the ticket and times when jobber drills are needed; I have both and need and use both. If I had to pick only one length, I would get jobber drills because there are times when you need to go deep and screw machine drills just won't get it. Screw machine drills are more rigid, true, but they are not a panacea.

My advice is to buy drills in fractional, wire, letter and metric, in that order. I would buy them from reputable makers only and I would buy them in the point geometry you prefer; both 118 and 135 works. I would also buy some cobalt spot drills to suit the geometry of your drills. You can opt for cobalt if you choose but for probably 90% of the work you are likely to do, HSS will be fine.

Learn to sharpen your drills. Doesn't matter what you use to sharpen them as long as they are sharp.

Don't spend big money on reamers unless you are doing work that requires them frequently. They are expensive and for occasional use, buy the ones you need or learn to bore accurately. The wabbit hole is deep indeed, but this is one place where you can avoid some cost.

All good advise Mikey. You have been down this road before.
At work, we drill out a lot of broken bolts. You learn what works and what doesn’t.
What did John say, cheap is crap, crap is cheap.

 

[jwmelvin]

Still, that should not have happened.

Just to close the loop on my thread fork, ISC Supplies contacted Norseman for me and Norseman will be sending me a new 5/16" drill bit.

 

[Janderso]

Don't forget to get a few quality left handed bits. They save the bacon on broken bolts/studs.

 

[macardoso]

I want to add my experience. I bought a cheap ENCO branded 115 pc set some years back. maybe 5-10% were bad grinds or were bent. I've replaced the bad or heavily used bits over the years with quality 135 degree split point drills. Bet my set is still 60% the original cheap ones and they work fine. My total expense to do it this way is low and spread out.

 

[GunsOfNavarone]

I want to add my experience. I bought a cheap ENCO branded 115 pc set some years back. maybe 5-10% were bad grinds or were bent. I've replaced the bad or heavily used bits over the years with quality 135 degree split point drills. Bet my set is still 60% the original cheap ones and they work fine. My total expense to do it this way is low and spread out.

I can appreciate that for sure, but I have MANY small sets of Craftsman and Dewalt, nothing at a level I would choose for true machining. I work so hard and so many hours, I wanted to "splurge" on a decent set. How I used it when it broke...well both my Craftsman and Dewalt would have been fine. I'm just accepting it as a fluke. I've used one or two on thick stainless with no issues. As I break these or more hopefully, dull them, I will go to that fancy french sounding company for the one offs. I do have a jig for sharpening bits, but just don't think they will be as good...but I'll practice, but practice runs probably won't be good enough to rely on.

 

[PaulH]

While the subject of drills is on hand...I see a lot of what I assume is surplus from aviation, piloted core drills on Ebay. Some of these with a little grinding on the pilot would probably have a tendency to run a little truer in drilling out a .22 rimfire barrel to 5/16" for a liner installation than a twist drill, right? I've only got a one-off job and don't want to spend the money for a gun drill, and I'm intimidated by making a homemade "D" drill although I have a bunch of OH-1 to experiment with. On this job, a rough interior finish is not a detriment, but drilling from both ends to the middle (24" oal) it would behoove me to try to meet in the middle within, say .040" concentric. Opinions?

 

[GunsOfNavarone]

@PaulH I can't help with your question unfortunately, but I'm just curious, why even try to re-line the barrel? How much could it be for a new .22 barrel? Seems like a fair amount of work AND you need to come up with a bit to do it...no guarantees first attempt will even fly? If your just going into this for the experience whether it works or not...make that D drill...maybe you'll surprise yourself.
Good Luck Brother!