Drill Bits
Senior User
Joined: Apr 2015
Posts: 173
Likes: 0
Definitely go with a cobalt bit. The cobalt is added to the HSS at the mill and greatly improves the hot hardness of the bit. The crap "cobalt" bits sold by Harbor Freight and a number of other online retailers are just that - crap. You can't buy some 135 piece set of cobalt bits for $49.95 and actually expect them to be good for much except drilling wood.
And I agree, stay away from the big box store cobalt/titanium drill bits as they're just a thin layer of coating on them. Once that wears off, you're left with an inferior Chinese pot metal drill bit.
FYI, the Drill Hog bits are high moly (M7) HSS and come with a lifetime warranty. For the average home user, a high quality USA made HSS drill bit can do 99% of the drilling tasks.
Cargo Master
Joined: May 2007
Posts: 2,071
Likes: 35
From: British Columbia
Drills
Cleveland Twist Drill, Dormer, P&A, etc. are good names.
I work in maintenance and our tool cribs started buying cobalt drills, but the problem with them is that they have a very thick web so after one or two light sharpenings they are pretty well useless, unless you have a web thinning drill grinding machine.
I find that regular HSS (not Chinese or other fake HSS) drills will drill almost any steel, including grade 8 bolts. We used these in a machine shop I worked at for about five years, sharpening them on our Brierley drill grinder (aka pointer) as needed. Running two milling machines 16 hours a day, it was an unusual occurrence to even have to replace a drill. Of course we were using the optimum feeds and speeds and lots of coolant, but it is enlightening just how long a twist drill will last with proper use and sharpening.
By the way, the correct term for them is twist drills.
I work in maintenance and our tool cribs started buying cobalt drills, but the problem with them is that they have a very thick web so after one or two light sharpenings they are pretty well useless, unless you have a web thinning drill grinding machine.
I find that regular HSS (not Chinese or other fake HSS) drills will drill almost any steel, including grade 8 bolts. We used these in a machine shop I worked at for about five years, sharpening them on our Brierley drill grinder (aka pointer) as needed. Running two milling machines 16 hours a day, it was an unusual occurrence to even have to replace a drill. Of course we were using the optimum feeds and speeds and lots of coolant, but it is enlightening just how long a twist drill will last with proper use and sharpening.
By the way, the correct term for them is twist drills.
Fleet Mechanic
Joined: Jul 2005
Posts: 1,463
Likes: 103
From: Staten Island, NY
Cleveland Twist Drill, Dormer, P&A, etc. are good names.
I work in maintenance and our tool cribs started buying cobalt drills, but the problem with them is that they have a very thick web so after one or two light sharpenings they are pretty well useless, unless you have a web thinning drill grinding machine.
I find that regular HSS (not Chinese or other fake HSS) drills will drill almost any steel, including grade 8 bolts. We used these in a machine shop I worked at for about five years, sharpening them on our Brierley drill grinder (aka pointer) as needed. Running two milling machines 16 hours a day, it was an unusual occurrence to even have to replace a drill. Of course we were using the optimum feeds and speeds and lots of coolant, but it is enlightening just how long a twist drill will last with proper use and sharpening.
By the way, the correct term for them is twist drills.
I work in maintenance and our tool cribs started buying cobalt drills, but the problem with them is that they have a very thick web so after one or two light sharpenings they are pretty well useless, unless you have a web thinning drill grinding machine.
I find that regular HSS (not Chinese or other fake HSS) drills will drill almost any steel, including grade 8 bolts. We used these in a machine shop I worked at for about five years, sharpening them on our Brierley drill grinder (aka pointer) as needed. Running two milling machines 16 hours a day, it was an unusual occurrence to even have to replace a drill. Of course we were using the optimum feeds and speeds and lots of coolant, but it is enlightening just how long a twist drill will last with proper use and sharpening.
By the way, the correct term for them is twist drills.
Logistics Pro
Joined: Aug 2005
Posts: 3,884
Likes: 180
From: Morgan Hill, CA
When I was at the shop we'd buy all our bits from MSC Direct. I agree, high speed steel is the way to go.
As far as speeds, the smaller diameter bits need to be turned faster. The radius is much smaller so the cutting speed is much lower. It's easy to define and maintain your speeds and feeds on a mill, not so much by hand!
As far as speeds, the smaller diameter bits need to be turned faster. The radius is much smaller so the cutting speed is much lower. It's easy to define and maintain your speeds and feeds on a mill, not so much by hand!
Cargo Master
Joined: May 2007
Posts: 2,071
Likes: 35
From: British Columbia
It's very difficult to maintain a steady, straight pressure on a drill by hand, if the item is possible to put in a drill press (even a cheap and nasty one) it is amazing how much easier it is to drill a nice straight hole with good chip formation.
Modern cordless drills are really good nowadays however, some have a built in spirit level which makes drilling a lot easier.
Modern cordless drills are really good nowadays however, some have a built in spirit level which makes drilling a lot easier.
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
Purchased a set of Dewalt Cobalt bits and seem to hold up well; although, couple days ago broke a hardened intake manifold bolt off and went thru a couple of the Dewalt bits to drill it out, probly to be expected? Shopping for replacement, but do not have a clue what to look for, 118 vs 135 degree; split point vs straight, etc., etc.. Currently have a few paks of the following in shop cart; thought I would check with more knowledgeable members for suggestions before pulling the trigger?
Champion Cutting Tool 705C-5/32 Cobalt 5/32-Inch 135 Degree Split Point HSS HD Jobber Twist Drill Bits, 12-Pack
Comments, suggestions appreciated!
Champion Cutting Tool 705C-5/32 Cobalt 5/32-Inch 135 Degree Split Point HSS HD Jobber Twist Drill Bits, 12-Pack
Comments, suggestions appreciated!
Fleet Mechanic
Joined: Jul 2005
Posts: 1,463
Likes: 103
From: Staten Island, NY
Purchased a set of Dewalt Cobalt bits and seem to hold up well; although, couple days ago broke a hardened intake manifold bolt off and went thru a couple of the Dewalt bits to drill it out, probly to be expected? Shopping for replacement, but do not have a clue what to look for, 118 vs 135 degree; split point vs straight, etc., etc.. Currently have a few paks of the following in shop cart; thought I would check with more knowledgeable members for suggestions before pulling the trigger?
Champion Cutting Tool 705C-5/32 Cobalt 5/32-Inch 135 Degree Split Point HSS HD Jobber Twist Drill Bits, 12-Pack
Comments, suggestions appreciated!
Champion Cutting Tool 705C-5/32 Cobalt 5/32-Inch 135 Degree Split Point HSS HD Jobber Twist Drill Bits, 12-Pack
Comments, suggestions appreciated!
Personally, since I drill almost everything from wood to stainless I use 135 degree bits for almost everything. They're a little bit more expensive and a little bit harder to sharpen by hand but I find them worth it.
Again, I think cobalt bits for the average home shop are a waste of money. They don't let you drill "harder" metals - that's what carbide is for. They only stay hard when run extremely hot like when drilling stainless without coolant.
Cargo Master
Joined: May 2007
Posts: 2,071
Likes: 35
From: British Columbia
Intake manifold bolts should be grade 5, or at most grade 8. I wouldn't call them "hardened".
Even a grade 8 bolt should drill very easily with a good quality HSS drill.
Even a grade 8 bolt should drill very easily with a good quality HSS drill.
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
Looking to restock and replace drill bits, just a matter of deciding on the type and flavor. Considering I only use drill bits on limited basis, not sure a drill sharpener would be worth the investment; consequently, looking for quality bits, with best features for this novice user.
Cross-Country
Joined: Jan 2005
Posts: 83
Likes: 3
Your answer is the best. I've been in the business forever and had a 9 month stint sharpening tools exclusively once. I almost always use the 135* bits with split points. Two things that cause problems is that a lot of people run them too fast. If you run a 1/2" bit @ 2000 rpm, You'll have a meltdown. What coolant/lubricant you use can make a great deal of difference too. Tap-magic is great but spendy and volatile. Something I've found that works fairly well is MIG nozzle anti-spatter wax. It's a high temp wax ('cause it's for welding) stays put and it has good chip removal and leaves a decent finish.
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
Greatly appreciate comments!! Appears the bits mentioned in the post # 21 cover majority of my concerns, likely pull the trigger on the purchase and restock for future use.
Again, I thank U's all for suggestions and comments!!
Again, I thank U's all for suggestions and comments!!
Fleet Mechanic
Joined: Jul 2005
Posts: 1,463
Likes: 103
From: Staten Island, NY
Just grab a handful of old beat up dull bits and a bench grinder and practice. Anyone can learn pretty quickly to hand sharpen drill bits. No one actually admits to using a Drill Doctor but they sure sell lots of them!
Cargo Master
Joined: May 2007
Posts: 2,071
Likes: 35
From: British Columbia
"Just grab a handful of old beat up dull bits and a bench grinder and practice. Anyone can learn pretty quickly to hand sharpen drill bits. No one actually admits to using a Drill Doctor but they sure sell lots of them!"
...and I bet there's Youtube videos showing how to sharpen by hand.
I have used the Drill Doctor tools before but had poor success with them. The expensive machines work very well for me though.
When I was younger and occasionally switched to a new job the other guys would generally be quite happy to give me a big bin of dull drills after I told them I could sharpen them by hand.
After a few hours though, one gets a rather nasty crick in the neck.
...and I bet there's Youtube videos showing how to sharpen by hand.
I have used the Drill Doctor tools before but had poor success with them. The expensive machines work very well for me though.
When I was younger and occasionally switched to a new job the other guys would generally be quite happy to give me a big bin of dull drills after I told them I could sharpen them by hand.
After a few hours though, one gets a rather nasty crick in the neck.
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