Drill Function Difficulties

[Deolman]

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?

[fwharris]

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

[bergerud]

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.

[Deolman]

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?

[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

[Deolman]

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

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.

[DickB]

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.

[Mugsowner]

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.