Drill Function Difficulties

I had an occasion to drill numerous holes. I needed three different sizes of holes. The holes drilled are uniform in size but are larger than designed. They are round so I believe the X and Y axis movements are performing as designed. I went back to designer and double checked the size I wanted and they are correct in designer. They are as follows:

Designed - .250" Actual Size - .312"
Designed - .400" Actual Size - .470"
Designed - .500" Actual Size - .560"

I am talking about 100 of each size holes called for all being perfectly the same oversize measurement. I would think if was mechanical the hole size would vary or they would be oblong.

I am using Version 3.106, Build 38.

Any Suggestions?

What bit are you using as the drill tool? The all seem to be about the same size difference than your design size.

That looks to me like run out. The bit must be out by around 0.03". It is simply wobbling and making a larger hole.

I am using the 1/8" cutting bit. It is in the carvetight chuck. What would be the best way to check for run out?

Not really sure if it's the best way but could you just drill a 1/8 hole and see if the hole is larger than the bit?
Rick H

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Originally Posted by want2b

Not really sure if it's the best way but could you just drill a 1/8 hole and see if the hole is larger than the bit?
Rick H

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I did drill some 1/8" holes and the other holes - with the 3/16" bit. What a dummy! LOL Sometimes it just takes someone else's eyes to see what's really going on. I had forgotten I had the 3/16" bit. Thanks for all of the help everyone. I won't make this mistake again.

Although it sounds like you found your problem, I will add that I have not been able to drill very precise diameter holes with the Carvewright. One problem is that the 1/8" cutting bit is a bit larger than 1/8" - at least mine is. I tested this by drilling a hole with the cutting bit using my drill press and another with my 1/8" drill bit. The drill bit slips easily into and out of the hole cut by the 1/8" cutting bit, but the cutting bit won't go into the hole made with the drill bit. I do use the Carvewright to drill undersize pilot holes, then finish with drill bits in the drill press.

Here is a little something I picked up on in the machine building world talking to machinists about processes that needed to be done. A drill does not drill a round hole, it may look round but will be slightly out of round. A carbide mill will give a rounder hole than a drill bit. I am thinking that because of design there is less defection in the milling bit.