When you know its not your day!

[Metal Mickey]

Well I wasn't feeling at my best so I better say that at the outset....BUT.....have you ever tried to do something you have done before only to have one problem after another? Well I have in the past but today's was a woozy!

All I wanted to do is to drill and tap a hole for a 3mm grub screw in a flywheel I have made for a couple of Christmas gifts. I started by squaring up my rotary table in the upright position and secured the flywheel in the chuck. No problems here. So all I had to do is centre the quill (and therefore centre drill/drill) over the flywheel as in the picture below:-

I thought I was being clever by covering the brass outer flywheel cover with insulation tape. I had tried using masking tape but there was a slight marking so over to the black tape. Next I wanted to find the centre of the boss in which I wanted to drill the tapping hole. My edgefinder of choice is the electronic one as seeing the red light coming on when the circuit is made. But yes, you may have guessed but I couldn't see why it wasn't working. I even replaced the batteries.........insulation tape certainly worked!

Okay then over to my other edgefinder which is a laser, but I couldn't get the laser to stay bright enough to register when it was on either edge. By now I was getting cheesed off so I thought sod it I would put the tapping drill in and do it by eye when the drill was fully lowered and alongside the boss. When I thought it was about right I zeroed the digital readouts and was about to drill when I saw the insulation tape!

So off came the tape and I used thick card to protect the flywheel from the jaws. Then the electronic edgefinder was put back and the process started again, only to find that now I couldn't lower the edge finder low enough as it was fouling the chuck!

I then had to get the parallels out to move the flywheel away from the chuck. By now an hour had passed and I stopped for a cup of tea! When I returned the edge's were found, allowing the centre position registered and would you believe it I was only 0.0012" out from the position I found with my eye!!!!!

I was now really cheesed off (I am being really polite). I lost count of the amount of times I tightened and undid the draw bar on the mill.

The rest of the session went like clockwork when it came to milling the 6 holes.

Grrrrrrrrr......... :'( :'( :'(

happy days............................

 

[tel]

I shouldn't larf, but ;D ;D ;D

 

[mklotz]

Why not put a close-fitting pin in the flywheel bore and center on that? Not quite as accurate as locating off the (hopefully concentric) rim but it's a setscrew hole so perfection is not required.

Grounding the flywheel to the table with a short jumper wire would have solved the tape insulation problem. Personally, I don't like using tape for protection - too easy to slip. Brass or copper shim stock is preferable although in this application it probably doesn't matter.

I wouldn't have bothered with the RT (unless it was going to be used for a succeeding operation). Just grip the flywheel rim in the vise and use a conventional edge finder on the circumference or on a pin in the bore.

Don't feel that you wasted your time, however. They call it experience and this is how you acquire it.

 

[wareagle]

Yeah, we've all had them at one point or another. I have a term that I use for those days, but it isn't appropriate for publication here. ;D Hang in there, tomorrow is a new day!

And speaking of the electronic edge finders... I have one and the principal is really cool. There is one problem, though. Mine has .011" TIR. Doesn't lend itself for precision work! Unfortunately, I found this out the hard way when building some brackets. The holes weren't quite lining up and I had a time trying to figure out what was happening. I was able to salvage every piece, but I also felt like things should have been lining up better than they were.

After I was done with the project, I went through the steps trying to find the error. It came down to either the table not travelling the required distance, or the work piece locating. A dial indicator quickly rulled out the mill, so I took a close look at the edge finder. Once I chucked it up in a collet, the TIR made itself knnown. To rule out the collet, I inserted a piece of drill rod and had a reading of .0005" TIR. The egde finder went back in, and I was showning the same TIR as before.

As a result of this finding, a couple of things happened in my shop. One, the electronic edge finder had a date with the scrap bin. And two, I went on to check my other measuring instruments for accuracy. The other instrument I found not giving proper readins was my Starrett Last Word Indicator, and that was because it was sticking. I have since had it rebuilt and it works great.

So the moral of the story, you may want to check your instruments and measuring/locationg tools if you are having goofy results that don't make sense. Before I checked my stuff, I just thought it was becasue I couldn't do simple math and that I was a horrible machinist. That one exercise boosted my confidence in both myself and my tools.


Those flywheels look very nice! :bow:

 

[Tin Falcon]

I think we have all had days like that. As far as the drilling of a grub screw I usually drill with my cordless by eye.

Tin

 

[CrewCab]

I usually drill with my cordless by eye.

I've only ever drilled one ......... but given the constraints ........... I used a cordless as well ............ and drilled at an angle rather than perpendicular to the shaft just so I missed the flywheel with the drill chuck.

Mickey, try and take it in your stride mate 8) that sort of day happens to most of us at least a couple of times a month :

CC