Drilling errors and solutions

mikey said:
If you are using a hand-held drill, it isn't unusual to have drift when using jobber drills. If it was me and I had to make multiple pieces all fit, I would make a jig to fit a sharp prick punch so marking out is consistent. Then I would use a rotabroach to drill the holes. A rotabroach has a sharpened pin to orient the cutter and it will locate in the prick punch hole accurately. You can also visually see when a rotabroach is cutting evenly so you are less likely to cant the drill. A rotabroach also cuts burr-free holes so you have less clean up to do.
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Add that Rotobroach cutters are expensive and difficult to sharpen, takes three different setups on a tool & cutter grinder to do it.
 
benmychree said:
Add that Rotobroach cutters are expensive and difficult to sharpen, takes three different setups on a tool & cutter grinder to do it.
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True, but they last far longer than a drill before they dull, provided you use a wax stick lubricant each time.

Edit: I emailed Blair to see what they charge to resharpen one of the broaches. We'll see what they say.
 
I would look into drill bits with a 4 facet grind. They don t walk around like regular drills and also way less blow through on your exit hole. I grind drills for a Wood Cabinet Company with the four facet and they have been very impressed with it s accuracy of hole size and life of there drills in production. First thing I do when i buy a drill is put the four facet grind on it.image.jpeg
 
an optical centerpunch came with my used lathe, I thought is was stupid. Now it’s one of my favorite hole marking tools.
Grumpy One
 
MarkM said:
I would look into drill bits with a 4 facet grind. They don t walk around like regular drills and also way less blow through on your exit hole. I grind drills for a Wood Cabinet Company with the four facet and they have been very impressed with it s accuracy of hole size and life of there drills in production. First thing I do when i buy a drill is put the four facet grind on it.
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4 facet grind? Do you mean make it into a split point? LOL. Yes split point drills are less apt to walk and wander. Still have to do a good job of making the edges equal length too.
 
No a four facet grind is not a split point. Four facet are the most accurate of all drill grinds. Perfect drill geometry on both sides when done proper. Equal lip length and a true centre that doesn t need a pilot hole or centre punch. Split points are still a chisel with a thin web that don t centre them selves when they drill. They also,produce a very accurate hole. Almost reamed. I don t know why it is highlighted. My ipad is on it s way. Disregard that. Not shouting. I have seen one grind of a four facet produce over five thousand holes on a screw machine on more than one occasion. Yes a six spindle Davenport and brown and sharpes 2 b. Try one it might impress you. For the o.p. They don t walk it may solve your problem.
 
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First thing I would do is use a carbide scribe you can get one at any welding shop scribe a cross this will leave a slight spot in the center a prick punch will sit in then use a bigger punch to provide a deeper dimple start the hole with a centering bit https://m.harborfreight.com/center-drill-countersink-set-5-pc-60381.html then drill with a small drill bit then your final size it helps if your first bit is big enough to search the Web of your final bit if you wanna try a rotobroach bit you can get a Chinese one with a centering pin on ebay for under 20 bucks for a half inch bit but you will have to have an adapter or a drill chuck big enough to chuck a 3/4 inch bit
 
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