Ways to measure holes center to center?

Emilio I'm no expert, but the calibration or practice gage that came with the 8" Mike is 4.9967". After some practice I could replicate to well within .001". The Mike is not calibrated for tenths so by looking at where I was between the .001's I could see I was within a couple of tenths. Like reading a micrometer it's all about feel and alignment. For me this is way easier than using a caliper mostly because of the rounded features on the ends of the Mike.

I'm not sure what you mean Brockwood about directly transferring, but the Mike is made to give you the measurement, not to mark with.
 
C-Bag said:
Emilio I'm no expert, but the calibration or practice gage that came with the 8" Mike is 4.9967". After some practice I could replicate to well within .001". The Mike is not calibrated for tenths so by looking at where I was between the .001's I could see I was within a couple of tenths. Like reading a micrometer it's all about feel and alignment. For me this is way easier than using a caliper mostly because of the rounded features on the ends of the Mike.

I'm not sure what you mean Brockwood about directly transferring, but the Mike is made to give you the measurement, not to mark with.
Click to expand...
Then you did answer my question, C-Bag! Seems to me that transferring a measured number to any other means of marking & thus replicating a given distance is as we can expect with the as built Sorensen. Now if the Sorensen could somehow directly transfer it's measure: it would be most accurate!
 
BROCKWOOD said:
Then you did answer my question, C-Bag! Seems to me that transferring a measured number to any other means of marking & thus replicating a given distance is as we can expect with the as built Sorensen. Now if the Sorensen could somehow directly transfer it's measure: it would be most accurate!
Click to expand...

It seems to me that the mike's sole purpose is give a quick, direct and accurate way to measure centers without doing math, transferring numbers etc. Because of the way it works, the probes are not at the center distance when the gage gives you the center distance. So it can't be used for transferring the measurements. Which is all right with me. Just like I don't use my mic's as clamps, I wouldn't want to use the Mike as a scribe or punch :)

The whole process of determining hole centers has always been like a golf shot for me. A little error at the beginning and you're out in the rough by the end. Armed with the true center measurement and going straight to DRO I've finally been able to make some pieces that fit the first time. Unlike measuring with a caliper, figuring centers, marking, punching, then trying figure in the windage of my worn out mill before DRO.
 
My Center Mike came in. Put a thumbscrew on order & glued a split in 2 accessory mount back together. Yep, 1 of the black stands for the Accessory split in 2 during shipping. Fortunately, this does not affect accuracy at all. It is the end to end lengths of the 2 rods that matter. The relationship of the 2 rods is also of no consequence. Really, The instructions for the Accessory are all that matters as any known (proven) rod length can be substituted once the math is understood.



IMG_20171128_025358418.jpg

IMG_20171128_025605408.jpg
 
I noticed that some of the Center Mikes come with a smaller pin attached to the ends of the main pins,? maybe to measure smaller holes?
Or is this a modification?

s-l1600 (2).jpg
 
Interesting, I looked at my 8" Mike and it has the holes. I didn't get any pins, but this is good to know. It must be for measuring smaller holes than the regular probes will fit into.
 
So, these Mikes are great for checking existing holes, but with no way to lay out or mark., or for determining the center to center distance of an existing part that you want to copy? It looks like a nice tool but I don't know If I can get much use from it. I thought about getting one but what would I use it for? I own a set of Mitutuyo caliper center distance attachments, not the best way to check but may be good enough in some cases.
I also use transfer punches and Heimann trans screws. How is everyone using these Center Mikes?
 
EmilioG wrote: "....or for determining the center to center distance of an existing part that you want to copy?"

It's sole purpose is to provide center to center distance of existing parts that need copying.

Although I am waiting on a thumbscrew, I tried the Mike on the included standard & came close - the fine tuning doesn't work without all 3 thumbscrews present. Would have been nice to make my own, but my import lathe isn't good enough to make no3 screws just yet.
 
Well, I bought one of those hole center mics from an Ebay seller. It arrived a couple days ago, and looked pretty good. Obviously used, but it "looked" good. Well, untiI I tried to move the sliders. They were frozen in place, and no I didn't forget to loosen the knobs. That's when I looked it over more carefully. It showed signs of cleaning and polishing, and there were still some small spots of gunk and rust exposed on the outboard end.

I contacted the seller, but have heard nothing back so far. I soaked it in penetrating oil over night, and the next morning I gently tapped the first slider with a brass hammer until it started to move. The space that it had occupied was completely covered with rust and gunk. 100%. I left it in penetrating oil again overnight, and this morning I was able to move all of the sliders, but judicious use of the brass hammer was still required. All three sliders were rusted in place. Its obvious that the entire unit was rusted up, and the seller cleaned off all the visible rust and put it up for sale. Its a seller with 100% positive feedback.

Center Mic.jpg
 
Mine was frozen stuck too, but it wasn't rust. It was some kind of gunk/old oil/galloping crud. Luckily it cleaned up nice, and didn't corrode the markings. I hope you hear back from the seller, sounds like you might need to send it back.
 
You must log in or register to reply here.
Back
Top