So as the title says, I've been a welder for 15 years, and now I've been hired into a machinist position, but I'm running the machine shop in this business. I've done machining work related to the welding I've done, sometimes even working as a machinist when the welding work slows down. My last job was 90% machinist work with 10% welding repair.
Now I'm expected to be a full machinist and run a whole machine section (2 lathes, 2 mills, and an entire wall of disorganized tooling) by myself. To the point where I'm the only guy in the shop that can figure out how to set a power feed on a lathe or mill. It's a little overwhelming tbh. But I'm struggling through.
Today's challenge: drill and bore a hole through 10.5 inches of 1018.
What I've done:
chucked up the material in the 3 jaw on the lathe
beat around the stock until it was running mostly true (as far as can be read with a dial indicator on mill scale)
Center drilled with 3/8 center drill (only center drill available)
Proceeded to drill through with 9/16 because that's the only drill we had that was long enough
My problem now:
When the drill popped out the other side, I can see through my spindle it's maybe 1/8 off center. Definitely wobble as seen from the back of the spindle.
How can I correct the straightness of my hole? The plan was to step up to 1 inch then 2 inch drills to be able to fit in the big boring bar, but i don't want the bigger drills to follow the pilot off center. Does it matter? Can I just feed the bigger bits slower and the problem will self correct?
Edit: Success! Flipped it around and started a couple inches with a stubby 3/4, then I got an extremely stout 1 3/4 to redrill the hole nice and straight. Once the first couple inches were started it was rigid enough to follow its own hole all the way back through.
Not ultra critical at this stage. It's basically a bushing for a bushing. It gets turned down on the OD for an interference fit on an existing bored hole and the ID just needs to be blasted out to a little over 4 and a half, then it gets welded in place and final line bored later.
I've never even heard of a gun drill but hot damn if that doesn't sound like the perfect pilot hole tool. Honestly I'm trying my best to make due with what the shop already has while recommending tools I've used before in machining. Last place I was at we had this wicked set of spade drills from like half inch all the way up to 3 inches and change that would tear through metal like butter.
At this shop, their last machinist quit 7 or 8 years ago and mostly I get blank looks when I ask if they have x or y tool/insert/tool holder. The owner is willing to buy new tooling but I've never been in the position to even select tooling for operations before, let alone outfit a shop for every process they want to run.
Gotcha, it sounds like it is fine to have a little extra clearance on the ID, which helps us here. I do recommend flipping the piece and squaring it back up best you can. If you have enough meat to start a short, stiff, small diameter center drill from the offset end, you at least know they'll meet approximately in the middle.
Keep the dia small for as deep as you can go with wall thickness between the new hole and the old, offset hole. Then step back up to your smallest diameter drill that'll reach like 1/3 of the way through the part. Keep the speed per guidelines with the material, but turn those feeds down super slow. The drill WILL eventually jump back into the existing hole, probably breaking the drill in the process. The goal is to get as deep as possible.
This is a challenging task for the equipment you've been given. Don't beat yourself up about it. Next time they want something like this, make four of them at 1/4 the length and weld them together.
Success! Flipped it around and started a couple inches with a stubby 3/4, then I got an extremely stout 1 3/4 to redrill the hole nice and straight. Once the first couple inches were started it was rigid enough to follow its own hole all the way back through.
Congrats! You'll come out of this job with a lot of tricks under your belt.
Next trick: figure out how to mount a 2.5 inch boring bar on a turret with only a 1.25 ledge on it. Im trying to talk the owner into fabbing a holder in house.
Also we found out the morse taper in the tail stock is all chewed up so we're going to look for a morse reamer to correct the tailstock.
This job is certainly tightening up my machinist chops. Im already looking forward to tig work where my tolerance is like +/- .030 lmaoo
Even worse, It's actually two parts the owner insists on doing together and parting later. Could have done two 5 inch parts but noooo, that might have been easy. Lol
Further, the center of stock on the backside is floating in air. It's a 9/16 hole that's a bit off-center, but not enough to put the true center in the wall.
I'll try flipping around the part and see if I have a boring bar small enough to true most of the hole from that end. Im confident in my original center, it just seems to have wandered a bit through the material.
Im not entirely sure that tailstock is aligned just right but the owner is riding me to produce since my first two weeks have been mostly restoring the equipment they have and addressing what can be fixed. The Szim lathe really only needed some minor leveling and some oil, but I put a lockout on the other lathe after I opened up the head and found a bunch of chipped gears. The szim has also definitely been crashed at least once but everything seems to be rigid and true as far as I can tell.
Can't say I understand his logic there. This would have been a slam dunk doing it in two pieces.
You could have this perfectly square and the bit still would have wandered at least somewhat. No raw material is perfectly homogeneous when it comes to hardness, and over 10 inches at that diameter you're pushing a wet noodle that will follow the path of least resistance.
Unless the owner wants to spring for a 10 inch long 4 inch diameter bit. That'd work...
It's very hard to tell with this guy, probably because he's an engineer first and the owner second. I grew up around a bunch of gas and electrical engineers, so it's not too terrible for me. Some of the other guys in the shop very much struggle with communicating with him though, which is understandable if you don't speak engineer.
Sometimes I throw out a tooling suggestion and he shoots it down immediately. Today, I pitched getting a Darex auto tool sharpener and he's all aboard as soon as I told him the local coast guard base had one. I never really know how he's going to react to things lol
I don't know much about machining but I would keep my resume up to date because this company sounds like it's being horribly mismanaged.