Broken drill bits

[Pcparas]

Hello
I am trying to dill out some 37/64 holes so I can tap 5/8 threads. I broke a 20 dollar bit tonight and have had some trouble breaking large bits recently. I have been using plenty of cutting oil. Any other suggestions to preventing my drill bits from snapping off? Thanks.

 

[bentendo]

You stepping up to that size or going straight for it? I'm probably telling you something you've already heard, but I've always had good results from starting with a smaller bit and boring out the hole incrementally.

Breaking bits is a bummer, man!

 

[Pcparas]

yea I am drilling out old holes so I am going from 1/2 to 37/64. Still snapping bits. Thanks though,

 

[73azbronco]

Bigger drill motor going slower.

 

[Hovtherid]

Your 37/64 is only slightly larger so your drill bit is actually trying to thread itself thru like a bolt into a nut. Only thing to do is go slow and watch very carefully especially when your almost thru. Also only use USA made bits. Everything else is absolute junk.

 

[Gas Pig]

Bigger drill motor going slower.

X2 that... Also with a brand new bit light pressure because it will grab and then want to corkscrew on you instead of drilling.

 

[TN1776]

In addition to going slower, if you're using a drill press that has a table you can clamp to, clamp your piece down like you mean it. My drill press has T-slots in the table, and the best money I spent after buying the drill press was a good set of t-clamps.

 

[bronco t]

Assuming you are drilling thick metal it is always better to step drill in 1/8 inch increments. Use plenty of oil, and make sure that you are 90 degrees to the hole at all times. Just 2 cents...

 

[Pcparas]

Yea I am going to try to get the piece clamped to my drill press this time. Before I had it in a vise and was doing the drilling with a hand drill. Thanks everybody.

 

[Rustytruck]

Take your broken bit and resharpen it. Then take the bit and on the cutting edge flatten it to take the hook off the cutting edge. On the outside corners grind a 1/16th radius. This will make the bit cut more material at the same time lessening the tendency to grab and with the hook ground off the cutting edge it wont pull its-self in you will have to push it in. Since you already have the hole you could also use a 4 flute core drill or a reamer.

 

[70 Steed]

Find a Mac Tools Distributor and buy a cobalt bit. If you break it they replace it. It's got a lifetime warranty.

 

[Jerseydevil]

First things first, use a center punch to keep your bit from wandering. Then it's just a matter of going slow enough not to burn the bit, and applying just enough pressure to cut the steel, but not snag it or bend the bit. Oil is essential, as is backing out often to release/ remove the chips.
I don't know if it's appropriate to drop a dealer name here, but since I am so happy with their service, products and pricing, I will, and leave it up to the mod to remove it if necessary. Www.buydrillbits.com. Great website btw with lots of info on drilling stuff. I called (toll free) with a question and spoke directly to John of the "Ask John" section. All their bits are made in the USA. They have it all. I've bought colbalt, carbide( for broken easy outs), lefties and a few carbide rasps. All of which are worth their weight in gold at times. Well ok, maybe silver.
Almost forgot, as mentioned, start with a smaller hole and step a couple sizes until you reach the size you need.