Drilling holes

JimDRIl

Member
I'm putting a saddle valve on a half inch galvanized pipe and I need to drill a quarter inch hole. Would I start off with a smaller bit, say an eighth inch, and then go with the 1/4? Or drill straight-away with the 1/4"
 
I always drill a pilot hole after making a punch mark with a center punch. I use cutting oil and try to make sure the speed is correct so that its cutting the way it should. It sure seems easier to move up in sizes than to try and take it all at once. I'm no machinist either, but sometimes need to drill holes in steel on things I am building.
 
You're probably better off with no pilot hole. The trouble is the drill breaks into the ID lengthwise to the pipe first. Then you have an interrupted cut and the drill will pull itself in. You have to be steady and hold it back some.
 
It really doesn't matter. If you have a good, sharp 1/4" drill, it should go through fairly easy. Getting it started on the round surface is the problem. I would start with a good deep punch mark.
 
There is a slick and easy way to do this job. Spot the hole with a good center punch. Go to your friendly neighbourhood industrial or auto parts supplier and ask for a 1/4" drill with a split point, sharpened to 135°. The split point looks like two little flats where the cutting edges meet in the center. They were invented specifically for drilling pipe. The 135° angle is common on better quality bits. It won't want to grab as badly as a regular 118° bit. I'd be surprised if it cost more than 3 or 4 dollars, and will do the best job. Unc
 
For something like that, I usually center punch, then drill a pilot with a combined drill and countersink, then drill to size.
 

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