- Joined
- Sep 24, 2012
- Messages
- 494
RandyM, thanks very much for that. I’m away from my computer just now, I’ll give it a look in a few hours.Here is one on accurately locating holes. It is a two part video. Maybe it is this one.
RandyM, thanks very much for that. I’m away from my computer just now, I’ll give it a look in a few hours.Here is one on accurately locating holes. It is a two part video. Maybe it is this one.
I've been tinkering with a very small machine shop for several years, but I'm a perpetual newbie. My question is about what point angle I should use for my everyday drills.
OK, I've been in the habit of buying 135-degree split point for all my drills, mainly because they seem to be sturdy and resist walking during the first moment of entry. Most of the time they perform beautifully. Actually, all the time, really.
My question is about those times when I need to drill a small hole in a very controlled, precise location. I have a set of combined drill/countersink to locate a tiny hole into the material, and then follow with the actual drill bit. I should have thought of this a LONG time ago, but I just realized that the cutting angle is LESS than my 135-degree drill bits... I'm not sure of the angle, but they look like about 60 degrees. So when I press the drill bit into the hole made by my combined drill/countersink, my drill bit is not going to immediately hit bottom, right?
If I'm going to use 135-degree split point drills, what should I use to make my initial hole? Whatever I use needs to make a larger degree-angle than 135 degrees, right? I know there is such a thing as spotting drills, but they look just like normal drills... if I'm going to use those, what's the difference between (1) making a pilot hole with a spotting drill and following up with a normal drill, and (2) just making the entire drill hole with the spotting drill? I mean, if the spotting drill is so superior with making the original hole, then why not just finish the hole with it?
What am I missing? You can tell I'm confused....
I’m still not clear on the difference between spotting drills and center drills, though. Can you explain please?
Dan-S, good question; my mistake for not being clear. Normally, my idea of a small hole is 0.125” or smaller. Sometimes as small as 0.060” or so. As far as placement accuracy, I guess I’ll say within 0.002” or 0.003”.To me the first question would be what do you consider a precise location +- 0.01",0.005",0.001"? The other factor is what sized drill are we talking about, as that also plays a part?
Dan-S, thank you! Nothing like pictures. The “combined” drills are the ones I’ve been using. They were the ones that gave me my original question since the included angle (60) is less than that of my drills (135).Center drills are most commonly used for making holes for dead or live center work in the lathe. However a lot of people use them to make starter holes for drills when they first start out so they don't have to buy 2 sets.
here you can see the difference. Combined = center drill when the angle is 60°
View attachment 247545
Dan-S, good question; my mistake for not being clear. Normally, my idea of a small hole is 0.125” or smaller. Sometimes as small as 0.060” or so. As far as placement accuracy, I guess I’ll say within 0.002” or 0.003”.
Mikey, thanks for the clear explanation of a spotting drill’s inability to clear chips. I’m not really willing to give up my 135-degree drills for 118’s, so it sounds like I’d better invest in some spotting drills.
I’m still not clear on the difference between spotting drills and center drills, though. Can you explain please?