What are your favorite drill bits?

[seabreez]

Originally Posted by hd002e

I have been using dewalt titanium for tye last 6-7 years and have been using it on wood and fiberglass with great results. The coating on them has held up pretty well over the years despite the salty humid air inside the boat. I would be curious to hear about favorite drill bits you guys have on the boat.

I once had to drill out exhaust manifold studs that were broken flush to the manifold. After wearing down many bits, someone suggested I use concrete drilling bits as the end of the bit is carbide. I drilled all 5 studs (trough the manifold) with the same bit. Keeping them cooled and well lubricated and lots of pressure and... voila!! I removed the manifold, then welded nuts on the studs and removed the studs.

[US1Fountain]

Tool and Die Maker for 35 yrs, and last 19 as a machinist in a University Aero dept. In other words, I work with SS all day. I use nothing but regular HSS drills, brand names such as Cleveland Twist. My best advice is keep a small bench grinder in your tool collection and learn how to sharpen a drill bit by hand. You should be able to resharpen one in a matter of 10-20 seconds. Or as stated earlier, a smaller drill bit grinder, ie Drill Doctor. You will get years out of a drill bit just by touching it up when needed. Otherwise, you will have a nice collection of the same size bits, all dull.
I usually dont recommend carbide, either solid or tipped. To easy to chip when drilling by hand. plus you'd need to also have a diamond wheel to regrind one

[jharding]

I love my left handed drill bits for drilling out busted bolts, start off small and increase size, when bit catches it backs broken bolt out. Like a lot have said you got to know how to sharpen, not hard, you tube and practice.

[coopec43]

NOTE
I missed Seabreez's post above where he also use tungsten tipped drills to drill steel. I will leave my post anyway.

When I really had my back to the wall trying to drill my SS chain plates I used a sharpened masonry bit. With a piece of timber across the back of the old aluminum cased hand drill (to get extra pressure) and my mate using the trigger we had each hole drilled in about two minutes.

I just looked on eBay and 12mm Masonry drills are around $A10 whereas Tungsten tipped 12mm drills are close to double the price.

The Caterpillar Diesel Fitters where I am use sharpened masonry drills to drill out broken engine studs

https://www.youtube.com/watch?v=0QaIOkn6D54

[cabo_sailor]

I have a cobalt and titanium set. Somewhere I saw a YouTube video of drilling stainless. He was not too concerned with the bits. Rather he was adamant that bit speed be slow, a small cup of water available and low to moderate pressure. He would drill a few moments then cool the bit in the water then drill some more. Skeptical but I tried it and son of gun there was a significant improvement in penetration time.

[TheOffice]

I use Milwaukee bits from Home Depot. When drilling SS I use a light oil (3n1) and a fair amount of pressure. The Milwaukee bits are better than the Bosch and Ryobi IMHO.

[coopec43]

Originally Posted by cabo_sailor

I have a cobalt and titanium set. Somewhere I saw a YouTube video of drilling stainless. He was not too concerned with the bits. Rather he was adamant that bit speed be slow, a small cup of water available and low to moderate pressure. He would drill a few moments then cool the bit in the water then drill some more. Skeptical but I tried it and son of gun there was a significant improvement in penetration time.

I agree, the RPM has to be quite low for SS. I was battling to get my Bench drill down to an acceptable RPM.

[sailah]

Originally Posted by US1Fountain

Tool and Die Maker for 35 yrs, and last 19 as a machinist in a University Aero dept. In other words, I work with SS all day. I use nothing but regular HSS drills, brand names such as Cleveland Twist. My best advice is keep a small bench grinder in your tool collection and learn how to sharpen a drill bit by hand. You should be able to resharpen one in a matter of 10-20 seconds. Or as stated earlier, a smaller drill bit grinder, ie Drill Doctor. You will get years out of a drill bit just by touching it up when needed. Otherwise, you will have a nice collection of the same size bits, all dull.
I usually dont recommend carbide, either solid or tipped. To easy to chip when drilling by hand. plus you'd need to also have a diamond wheel to regrind one

Pretty much this. I have a machine shop at home and my drill indexes are almost entirely HSS from quality manufacturers like Dormer, Morse, Norseman, Chicago Latrobe, Cleveland Twist, most of them are considerably older than I am. I have a full set of Morse taper bits by 64ths up to 2" and quite a few up to 3".

I buy bulk at industrial auctions to establish all the indexes: Letters, Numbers, Fractionals, Metric. Often you are paying pennies for the best quality.

I sharpen bits as needed, either with a Drill Doctor up to 1/2" and after that on a pedestal grinder by hand using some excellent tutorials on YouTube.

Under 1/4" or 6mm I find that it's easier to just buy another bit since grinding them gets fussy.

Super common sizes like 1/8", 1/4", 5mm, 6mm I buy packs of 10 on eBay, looking for high quality bits. When I need a specific size I buy from McMaster Carr and add to an existing order.

99.9% of the time, what I am drilling is worth far more than a $2 drill bit or my time to sharpen.

I think the biggest change in my experience with drilling was when I learned about how fast to spin the bit and how much pressure to put on the quill. I always use cutting fluid, except for cast iron.

Drilling stainless, as already noted, you need to keep the bit feeding and cutting. If you let it dwell, it will work harden and ruin your bit very fast. But in order to keep it feeding you need a sharp bit and some type of cutting fluid to keep temps down. If you just go at 316SS with a crap bit dry, fully expect to have a miserable experience. If you use a sharp bit, cutting fluid, and keep the pressure on, it cuts predictably. I always drill SS on my Bridgeport or big Powermatic drill press if possible as I find it far easier to keep the downward pressure on the bit and apply cutting fluid with my other hand.

In short, buy quality bits, keep them sharp, use cutting fluid and know how you should be attacking various materials. Makes it far more enjoyable.

[coopec43]

Sailah and US1Fountain

I was really interested to read your comments as you have used drills to make a living(unlike us backyarders)

I was not surprised when you said you use HSS drills to drill SS because I do it all the time. For larger holes ¾+ in. I would now use a tungsten tipped drill bit.

But I'm surprised neither of you have mentioned "pilot holes" (Maybe I'm going blind?)

[sailah]

To be clear, I don't make a living as a machinist (I own an IoT company making industrial ultrasonic sensors for steam systems) but I have a fair amount of professional experience working in a manufacturing space that used a lot of drills with CNC, screw machines etc. And I found it useful for making custom offroad enduro motorcycles.

But you are correct in the pilot holes, I guess I assumed that was common knowledge.

Almost always I will locate the hole accurately either on the Bridgeport with DRO or manually with layout lines. If accuracy does not need absolute precision I'll start by using a prick punch to get my location. Then use a starter drill (Stubby, spot drill, center drill usually) to get the hole started. Then use a pilot drill (maybe 1/4" depending, which is why I buy a lot of 1/4" drills). The stepup from there.

My favorite starter drills for pilots are usually screw machine length drills. These are very short and stiff so they don't wander. I bought about 500 as a lot at auction and use them all the time for just this purpose. Often jobber length drills aren't ideal, esp for SS.

[sailah]

There are excellent YouTube posters like Ox Tools, Abom79 that show this drilling procedure much better than I can explain it

[US1Fountain]

I always center drill 1st, then step drill up.
I was just staying with the original topic of favorite drill bits. My preference is a high quality HSS as I can drill away, and if it starts getting dull, a simple touchup on the pedistal grinder and I'm back to work. Speeds and Feeds are your friend. Too many people believe the higher the rpm, the faster it will drill. Those people usually have a nice collection of 1/4" drill bits.

[NicBeeee]

I swear by Alpen cobalt drills, they are an Austrian manufacturer.
Someone mentioned keeping the drill bit slow on steel, depends on the size of the bit, small fast, large slow.

[MicHughV]

This is an interesting thread to me...

I have boxes and boxes of drill bits....every make and kind.
A trip to my local hardware store is confusing, as I think there is marketing at play here.
One can purchase a cobalt drill set for around $30....but one can also purchase a single cobalt drill bit for $30. I'm told the cobalt drill sets are cobalt " tipped", what this means exactly I'm not sure...whereas the individual sold cobalt drills are supposedly all cobalt.
My research into the matter further confuses the matter, as apparently there are several manufacturer of cobalt drill bits and not all the same.
Specifically, I've been told to avoid any Chinese brand of cobalt drills.

I think using cobalt drills for just drilling wood might be a bit overkill and regular titanium probably do the trick quite well.

When it comes to stainless, my experience has been that the only drill bit to go through stainless is cobalt.

While I'm sure, in reading through this thread, that there are many of expert machinist on this thread using the best their is, my question is...what would be the best cobalt drill for a hobbyist...beside sharpness and durability...price point would also be a factor.

[Dave9111]

I do installations as part of my business besides doing hobby work on just about everything. The answer really depends on what your drilling. However, about once a year Home Depot has been selling Ryobi English drill sets up to 1/2" for $20 usually around Christmas. I bought two sets one year and they are very good bits for the cost.
For drilling hundreds of holes through tougher steel and stainless, high quality Cobalt drills are great, for most other things the Ryobi sets are hard to beat. I think I have 6+ sets in various places now. Look for the bright yellow/green index boxes. Also easy to spot.