what's the difference between cobalt, titanium coated, HSS
etc.Whick one is better for your harder metals Does it make a difference with one or the other for slower speed or higher speed drill settings??????

thanks as always,
thefonz

 

I like titanium bits for using a drill press when drilling in mild steel because they last forever without sharpening. If your drilling in to harder steel like bolts, stainless, axleshafts or anything hardend the cobalt works better. Most cobalt bits have a quad point, which drills very good, but they don't center very well. So if you need precision positioning when drilling with cobalt, drill a pilot first, don't just start with a 1/2" bit. If it can be 1/16" off either way, just get the big bit and go for it. That is if your drill and your arms can do it. Most titanium bits center and start well, so sometimes thats a better way to go if you need accuracy. And with the titanium bits the titanium is just a coating. So after you sharpen it you usually wear through the titanium and they will last just like a standard HSS bit.

 

Can't add much here. Turn 'em slow and keep 'em oiled/cooled. Speed and therefore heat, will do them in quickly.

 

i use cobalt bits. using some sort of drillin oil is a MUST or you'll burn up any bit. if the hole doesn't need to be too awful neat i use an oxyacetylene drill bit

 

I just buy em as i need em, I dont pay attention to the type of bit, but then again, i do not do alot of drilling in metal

 

Cobalt Bits Cut Well But They Are More Brittle. They Will Snap Easier Than A High Speed Bit.

 

Some observations:

You can get different drill point configurations in many different drill bit materials: standard grind, split point, not too familiar with the quad point. For general purpose the standard grind is probably best. If you drill a lot of holes and don't want to fool around with center drilling then use a split point. The disadvantage of a split point is that you can't sharpen them correctly (back to a split point) without a special drill sharpener.

It's a common misperception that common stainless steel is a lot harder than mild steel. SS is really not that much harder than mild steel, it is basically just stringier to drill or machine. When drilling SS be sure that you keep the bit in the material and making a chip and use plenty of coolant. If you get the SS hot while drilling it will work harder and most likely you'll smoke your drill bit.

The most important thing to consider regardless of type of drill you buy is to use the correct cutting speed for the material you are drilling. There are formulae available to determine this. There is a good description of this at this link (cutting speed). In general though, spin small drill bits fast and large ones slow.

Best to always drill a pilot hole for larger holes (1/2 +). It's easier on you, on your equipment, and on your drill bits. And as you said, it's more accurate!

 

I like the Dewalt cobalt one with the starter tip. They cut well and start with out needing a punch most of the time.

 

Thanks for all the input!!!!!!!!!!!

 

Takes me back to my machining class last year. Had to make our own lathe tools out of HSS.

 

Yep, I can remember doing that too. Is what's funny is that there is practically NO HSS tooling used in any sort of a business setting. It is all carbide insert tooling, except for the occasional special grind tool. I hope that they taught you about carbide tooling as well!

 

About seven years ago I was the lab instructor for the machining class at a small private college. We almost exclusively used HSS tooling because of the low budget and pretty much everyone only took the intro class anyway. The normal students didn't do anything with carbide other than written tests. The other advantage of using HSS is that it teaches the students how angles affect the way a tool cuts etc.

Calvin

 

It sure does, releif angles and all that good stuff. Plus carbides can get broke with intermittent cuts and such. Nothin wrong with HSS for starters. I'm not a big fan of itm for drill bits though. That's where a drill doctor comes in handy.

 

What do you guys think works better 118 degree or 135 split point. I personally do not like the 135's they seems like you have to sharpen them all the time. But I never drill anything but grade 8 bolts so I use pilot holes and the 118's seem to hold up better for that kind of work but you can not buy a good set of them anymore. And we have a drill doctor at work and I must be an idiot it does not work for me but my current drill bits have large flutes or on the twist part can never seem to line them up correctly in the drill doctors jig. Any help would be great because I hate drilling bolts then that brings up another whole subject those (insert your own curse word) bolt extractors.

 

I have to agree with there. I was referring to carbide mainly from the perspective of being familiar with it, especially if that student is considering a machining career.