Reverse Celebration

[Chip Hacket]

I was making a sleeve for a motor shaft today. I’ve done this for the same shaft once before, but that one ended up a little loose—workable, but not quite the satisfying fit I was aiming for. This time, I wanted to get within 0.0005 inches. I measured the shaft several times and confirmed it was 0.5505 inches. Great, I thought, so I planned to bore the ID to 0.56 inches.

I dialed it into the 4-jaw chuck and drilled to 0.5 inches. Then I painstakingly bored it to size. I’m pretty slow, and I checked the dimensions often, so it took a while. I’m doing this on my little Taig lathe, so it was a big job for the machine, especially starting with a 1.0-inch OD stock. But —I actually got it “dead bang” on the money.

As I stood up, I glanced at the sketch again and got that sick feeling in my stomach. Does this kind of dumb stuff happen to you guys? It sent me upstairs pouting. So frustrating sometimes.

 

[400bird]

Yeah, this is why my garage projects take so long. Math mistakes are easier to see when I write everything down.

 

[Just for fun]

Darn it anyway.

 

[Firstram]

Does this kind of dumb stuff happen to you guys?

Perfectly wrong….I do it all the time!

 

[Jake M]

Nope, never happens to me.

I do have excuses though (if I ever do mess up). I've got a couple of micrometers where the barrel reveals the lines at different points. Not a lot, but it can mess you up a bit if you let it. I also have a propensity to "math" my projects on the scratch pad that's always handy, versus cleaning my hands to use a phone/calculator/slide rule/abacus/ or any other math thing that's smarter than me. And that scratch pad always gets mixed in with final dimensions, interim dimensions, divisions by two for the radius dial, 30 degree infeeds on the compound, all the crib notes about where I had the dial before I backed out to take measurements and such... And I'm a little bit special about transposing digits, or glancing at a similar number that was meant for something else, or just plain dialing in what I remember without going back to check the drawing/notes/scribbles...

I clearly don't have any experience but I strongly suspect this- This stuff gets into your head if you let it. It can take on a life of it's own and wreck your whole day, and generally just get to be way more than it is. If you can teach yourself to just have a chuckle about it, (it's not easy, but doable), you can toss that into the pile of "blanks" for the next project and just move on to another project, or the next iteration of the one at hand. Or even take on another chore for a bit. Take the trash out, cut the grass, wash the car, whatever. But the trick is to be able to do that (whatever you do, more shop projects or other "stuff"), the hard part that makes it all work is to have your sense of humor turned on, so you can do that with a clean mind. Just keeping a little thing in it's place, and keeping on with moving forward, even if it involves a little detour. If you let it bug you.... It's gonna bug you for as long as you let it, and probably lead to doing the same thing again next time.....

 

[Eddyde]

I estimate about 10% of my shop time is correcting errors...

 

[WobblyHand]

I'm on version 3 now of an high pressure air probe. I broke a drill on the first one, my second one I machined the body ok, but drilled too deep. On the third design after discovering the hole is supposed to be stepped in diameter. Bought extra drill bits, because of #1. It's a process... I'm not expecting try #3 will be spectacular, but I'm still plugging away at it.

Just have to resolve oneself that next time will be a little better. Eventually one will succeed. That's what I tell myself. Fix my mistakes and try again!

 

[Flyinfool]

That even happens to the big money pros.
Remember the big mirror for the Hubble space telescope that was ground perfectly wrong. The most accurate optical piece ever made that was perfectly on to the wrong set of numbers, due to a math error converting between metric and SAE units.

 

[MrWhoopee]

I can beat that. Bored a coupling to a perfect 1.250, then realized the drawing said 1.1250.
Once you get the wrong number stuck in your head, the only way to dislodge it is machine the part to it.

 

[Chip Hacket]

I can beat that. Bored a coupling to a perfect 1.250, then realized the drawing said 1.1250.
Once you get the wrong number stuck in your head, the only way to dislodge it is machine the part to it.

Oh yea! I was just thankful there were no children around to hear my response. But, today will be a better day! After I mow the yard, and help my wife plant her shrubs and ..........