Cross feed rate of travel

On the Compound slide, replace the middle one. It will have the least effect if you loosen it to move the slide and forget to adjust it. On the cross slide, the 2nd or 3rd, probably the 3rd. Note that if you use the milling attachment lock screw, if it is turned so that the cross bar is vertical, the bar will hit the saddle wings. So watch that and when loose, be sure that the bar is horizontal
 
On the end mill issue, bolt and screw diameters are supposed to be slightly under nominal so that they are guaranteed to be a slip fit in a hole that is dead on nominal. That doesn't guarantee that two screws will be a slip fit in two holes whose centers are merely within tolerance of where they are supposed to be, but that's another issue not germain here. However, if the tailstock is not centered and/or is high or low, it will in fact cut a hole larger than its diameter. That isn't usually an issue but if it's critical that the hole not be over 0.6250", then you are safer using the boring bar.
 
I am more than a little embarrassed here.

Today I enlarged the hole in the base from 1/2" to fit the 5/8 bolt. I was really careful doing this. First my cheap 1/2" HF drill measured about .495 and since I am horrible at measuring the diameter of a hole I didn't even attempt that. Next I put a dial indicator on the boring bar. The DI was a little over an inch from the tip of the cutter. I couldn't get it any closer. The deflection was .002. I am sure that a boring bar when it deflects is a parabolic curve and my best guesstimate is that the boring bar was deflecting over .010 at the tip of the cutter.

Here is what is truly embarrassing. My technique sucked big time. I realized today that when I was backing off the boring bar I wasn't going back past my zero. I was only going back enough so the cutter would clear when I backed it out of the hole. Every time I did this the amount of the backlash increased the movement of the dial and I believe this is the main reason why my total dial movement was .1115 when it should have been around .0625 when I was boring the post.

Today my total dial movement after allowing for deflection was .070. Live and learn.
 
Again, it's the simplest things that cause the most frustration. Glad you got it all figured out.
Unless you can afford a really expensive bore gauge you should practice with a snap gauge and micrometer.
 
Rooster
I have starrett snap gauges and have practiced how to use a snap gauge based on the suggestions that I received in another thread on the forum. I consistently measure a hole smaller than it actually is. If my measurements were consistently smaller by the same amount then I could allow for my error. But so far there is no consistency to my measurements. I'll keep practicing.
 
mickri, i use a inside spring caliper and micrometer, seems to work well. I find it easier to get the right feel. I have been thinking of making some go/nogo gages, say 2" long with one half a thou over and other half a thou under. It's the smaller holes that are the hardest to measure.
 
Here is an excellent guide which will save me a lot of typing:
Pay VERY close attention to the recap of the most important issues at the end of the video, and remember them.
Do everything you possibly can to help the gage self center in the work accurately and repeatably.
Do not tighten the gage down more than is necessary to sweep the bore and read it with the mic. Over tightening a snap gage will ruin it, and give poor results.
Measure so the gage just bumps the mic spindle in only one location as it swings through.
Practice until you have confidence in your technique and attain consistent results. Having an accurate ring gage or better yet several several sizes when learning grades you as you practice.
Do not look at the mic numbers when measuring the gage. When the technique is correct, the final achieved numbers on the mic are golden. You should not need to pick the best average or guess over several tries.

Measuring bores consistently to within a tenth or two is not difficult after learning correctly.
 
You must log in or register to reply here.
Back
Top