I Never Thought There Would Be A Day...

[Bob La Londe]

I never thought there would be a day when I was disappointed with myself my missing a target by 3 ten thousandths. Ok, I'm not a tool maker. I admit it, but it was a simple tool. Just a carbide half round to go in a collet for positioning work near the edge of the work envelope on the Speedmaster mills. The first tool like this I made from 1144 for the Tormach mill was off by almost a full thousandth, but I made it on the mill. I ground this one with the diamond wheel on the T&C grinder. Makes me want to hang my head in shame as I turn in my high precision Harbor Freight caliper and my ultra precision better than thou Speedway micrometers.

To be fair I didn't check the mic against a gage block, and its been a couple years since I calibrated it so who knows for sure.



WAIT! Before you jump to the keyboard and start pounding madly away scroll down and read the rest of the post.


This post was made for self amusement and is not seeking critique or assistance. It is merely for those fellow members sophisticated enough to remember when they (like myself) could only dream of missing by only 3 tenths. Heck, the spacer I made on the lathe so I could mount the diamond cut off wheel that sheared the broken carbide mill before switching back to the regular diamond wheel to grind the half round had a bore that was off by a full thousandths. (I made it a hair over on purpose because it was easier than bringing it back to the lathe if it didn't fit.)

[darryl]

I dunno know- I get a little peeved with myself when I can't park the car in the driveway to within a thou of where I wanted it.

But seriously, I do get a little annoyed with myself when I'm trying to hit the sub-thou diameter, and I'm getting close, then suddenly I'm a full thou small.

[redlee]

Dont you love that feeling as you grab your Mic, start turning to check and you just know its gone past where its scrap.

[danlb]

When I first got into machining, I had no tutor, no mentor, no-one that could evaluate my efforts. As a result, I got in the habit drawing my parts before machining them and then trying to make parts that exactly matched the drawings. There was no going back and changing the drawings to match, even when the part could easily have worked at +- .005 tolerances.

It was a good way to hone the skills. Quite rewarding too.
Dan

[legendboy]

Sneak up on tenths with emery paper

[nickel-city-fab]

Don't feel too bad. I'm happy when I hit all my numbers within a thou. It actually happened the other week, then I threaded it wrong. Scrap.

[LKeithR]

The thing about really tight tolerances is that a lot of the time they just don't matter. In the repair and
maintenance field where I do a lot of my work two or three thou is often more than close enough. It
may be fun to play with stuff like that when you can but in a working environment tighter than necessary
tolerances just cost extra time and money. Being able to hit them is one thing, needing to is another...

[Cenedd]

I'll tell you what hurts your pride more. I turned down the end of a shaft to fit a bearing. Got it dead nuts on despite finding out later (when I scrapped the part) that the chuck bolts weren't tightened Hence the scrapped part when it made it look like I'd hammered the middle of the shaft to dimension.
With everything set up properly and even using a dial gauge on the cross slide, I missed. Wind it in 10, perfect. Wind it in the final 5 and I've overshot

[Bented]

Sneak up on tenths with emery paper

Sneak up on tenths with a grinder, rough turn to .010 big then grind to finish.

[Bob La Londe]

The thing about really tight tolerances is that a lot of the time they just don't matter. In the repair and
maintenance field where I do a lot of my work two or three thou is often more than close enough. It
may be fun to play with stuff like that when you can but in a working environment tighter than necessary
tolerances just cost extra time and money. Being able to hit them is one thing, needing to is another...

That was one of the hardest things for me to learn in machining. What is good enough. Initially on many things as good as I was capable of was barely good enough. Now generally for a part I try to get something that "works" and doesn't cause excess wear from slop. For a tool I tend to chase perfection. Well, maybe not for a wrench, but for anything that goes in a collet or a tool holder.

I was a contractor for a long time and it used to drive me bonkers when my guys would ask me, "Is that good enough." I would tell them if they have to ask it isn't.

In this instance 0.0004" was plenty good enough. It was just for a spindle mounted work stop. I used a piece of carbide mostly to play with my tool grinder.

G53 X0
Bump stock against stop.
Close vise.

[Cenedd]

That was one of the hardest things for me to learn in machining. What is good enough

I'm with you there Bob. The only excuse though is that I still need the practice (clearly!) on parts that don't matter so that I'm able to get tight dimensions when necessary.

[old mart]

I very rarely need tight tolerances, the last time was when making the Tom Senior mill R8 spindle out of two parts. I spent 90% of the time just getting the parts running as well as I could and it paid off. The spindle runs better than expected and I didn't make any scrap except for the swarf.