How do I drill small holes straight? (I made a suppressor adapter)

Thank you, yes, but a man has to do what man has to do... Off topic, but with similar envy, get the 1440GT with 650lbs more mass. But turning with the new one is still really cool, especially for a hobby guy used to a Craftsman 12x36 I've had for 30+ years. The 1340GT is orders of magnitude better
 
I have another lathe. I need to get it running. It's an old 18"x80" lathe, big (ish) boy. It's next in line after I finish my mill refurb. Hopefully it will drill straight holes. If it doesn't, I'm going to look for another hobby.
 
At 18x80, I'd say you have arrived at the "I own a chunk of the gravity of the earth" class of lathe. That's where if you don't own a forklift or a bridge crane or several football players you can't change chucks level. And 1/2" deep is a good start at a roughing cut. If you are that far in, and it won't drill straight, sell both, get something new, and smile before bailing. But I understand the sentiment - you join the club, pay your dues, damn thing ought to do what I told it to do...all I wanted was 2" of straight, not asking for that much out of the deal.
 
GL said:
At 18x80, I'd say you have arrived at the "I own a chunk of the gravity of the earth" class of lathe. That's where if you don't own a forklift or a bridge crane or several football players you can't change chucks level. And 1/2" deep is a good start at a roughing cut. If you are that far in, and it won't drill straight, sell both, get something new, and smile before bailing. But I understand the sentiment - you join the club, pay your dues, damn thing ought to do what I told it to do...all I wanted was 2" of straight, not asking for that much out of the deal.
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Oops - I fumbled. This reply should have been for @strantor. Sorry about that!
@strantor :
They can, and do, drill straight, but they have to be treated right. The bigger they are, the more prone they are to gravity. Just think gearbox you need a crane for, and the huge permanent force. The "settling" of the floor. The steady compression creep on whatever wedge you used under it. A big lathe is a great uncompromising thing that will lay it's will into what you cut with a satisfying unyielding firmness, but if allowed to fall into slight misalignment, it will assert that misalignment with the same firmness as when it was straight.

Given the kind of kit you cut metal for, I know much of this about measuring may be second nature to you. It is not so for me. I get upset that I can't make a tenths micrometer read the same measure twice. If not for you, then I put this stuff here for others going up the same learning curve as me.

Beyond leveling, there is the stuff we mentioned in post #22. Do not take fright. Take care with the checkouts, so you don't inadvertently walk yourself into giving up. Measuring this stuff such that errors in the act of measuring do not exceed the alignment error itself is the skill you acquire, mostly by making enough mistakes until you see a consistency that gives confidence.

Please forgive if this is stuff you already know. There are lots of videos on YT. (I almost use YT in place of normal search engine). Keith Rucker's LeBlond lathe example is useful.


Then - there is how to sort out a big lathe in extreme fashion.


If you don't have a 5 arc-seconds level, or a 0.0005" per foot machinist's level (about 9 arc-seconds), you can get there with a plumb bob method. (I was surprised too)!


That last one. He is a Brit from someplace well North of London and Watford. Expect some idiom expressions of a parochial nature - like "gnat's cock"!

P.S. My Dad, in his day, had a building constructions type plumb bob setup all in a 4" plastic drain pipe with a side view port cut-out - to stop air currents.
 
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GL said:
Thank you, yes, but a man has to do what man has to do... Off topic, but with similar envy, get the 1440GT with 650lbs more mass. But turning with the new one is still really cool, especially for a hobby guy used to a Craftsman 12x36 I've had for 30+ years. The 1340GT is orders of magnitude better
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Enough already.. Darn it - For PM-1440GT I get to envy what the other guy envies! Is that like envy*envy = envy_squared?
Seriously though, for new kit from Taiwan, and even though the price is out of my ball-park, it looks good value compared to similar quality high precision kit from USA or Europe.
 
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Your hole drilling problem could be as simple as a worn misaligned tail stock. Chuck a piece of bar stock in the lathe without using the tail stock and turn it to the exact dimension of the tailstock ram. Then extend the tailstock ram and use a straight edge to compare alignment.
 
The alignment could be as easy as a bad drill chuck in the TS. A bad jaw in the drill chuck will cock the drill bit. I have one that you can see daylight at the tip of one of the chuck jaws. Needs new jaws. Using a mt testbar In tailstock is your best alignment.
 
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