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Need a way to accurately gauge a .008 x .242 id groove

Maybe something like a Starrett 701-series Internal Groove Mic?
Starrett_701.jpg
I'm sure you'd need to modify it due to the small size of the part.

- Leigh
 
Thanks Leigh,
I was thinking the same thing a couple of weeks ago so I ordered in an el-cheapo id mic such as the one you attached, to see if it was feasible before I tried modyifing a quality tool. Once I ground down the probes to fit the groove , the micrometers feel was horrible and it was almost impossible to get consistent readings.
 
simpleminded said:
Once I ground down the probes to fit the groove , the micrometers feel was horrible and it was almost impossible to get consistent readings.
Click to expand...
I thought that would be the case, but since I've not tried it I thought I would wait for input from someone who had.

Thanks.

- Leigh
 
Gordon B. Clarke said:
Bill,

I think we're back to someone drawing something and not thinking about whether it is sensible or feasable. A 0.008" width and a diameter of 0.242 ±0.001"? Personally I haven't a clue as how to do it without taking out a bank loan. I'll bow in awe to whoever can come up with a solution that doesn't bankrupt you.

Gordon
Click to expand...


The groove is essential to the product. What the operator running these parts is doing now is,,, running 20 pieces, and then taking the last one of them to production to make sure the mating piece fits , a huge waste of eveybodys time.
 
One of these should work with the offset pointshttp://www.penntoolco.com/catalog/products/products.cfm?categoryID=4276
 
Make a disk, that theoretically fits into the slot. You might make it a bit smaller in diameter. Drill two holes into the disk. They are near the OD and do have the diameter of an inside mike's pins. Cut the disk in half with a wide cut. Means, cut out as much, so you can insert the two halves into the slot. Put the mike's pin into the bores and measure.
You'll have to calibrate that once.


Nick
 
but the diameter and width of the disk make it very iffy.
Click to expand...

Nowhere did I write, that the whole disk has to be as thick as the slot. It just has to fit inside.
Even the holes could be moved outside of the bore with a bit of thinking.

{derogatory comment deleted - trl}


Nick
 
The thickness of the probe (disk) directly affects its rigidity, and the rigidity directly affects the accuracy.

That's why micrometers don't have rubber anvils, even though they would be less likely to damage the workpiece surface.

- Leigh
 
It would help to know what volume (annualized) we're dealing with.

Custom gauge options that might be perfectly reasonable for an ongoing project
at 10k pcs/yr could be prohibitively expensive for a one-shot 100-piece run.

- Leigh
 
cut a peice of .006 or .007 shim stock to a point on one end. make two peices longer than your jaws on your groove mike glue them onto your groove mic let it set up. measure the groove write the numbers down remove your mic reset to the numbers you wrote down measure across the points with another mic. when the jobs done remove shim with a little heat oil your mic. heck use the cheepo set you bought leave it glued.
 
{Moderator warning... further misconduct will result in total deletion. - Leigh}

I just described a principle. I think most of the readers are intelligent enough to finalize it. If not, I'll draw a sketch, but leave out dimensions. That "instrument" can be made by a practical machinist in half a day.

Edit:
Maybe using an internal circlip and measuring the inside diameter when in place?
Click to expand...
Did you notice, that they don't have equal thickness (diameter-wise)? That won't work. Where would you measure?


Nick
 
Hmm its .006 -.007 thick if it deforms peal it off put on new and continue or go buy one one of those sets from a hardware store take out the .006 and .007 one use the radius ends. emeory cloth the others to close to thickness and use them
 
Even a radius in that size range would be subject to deformation and wear. I wonder about a small hole gage with two small pieces of snap ring attached in some manner. The attachment of the pieces would be the tough part.

Regards
 
OK, attached are two sketches.
One shows the side view (x-section) with one measuring point in place. The other one shows one such part in perspective view.
If you have a lathe and a mill (or a saw and a selection of files), it's easy to make. You need two of them. Place them into the grove, slid the inside mike into the bores and align it. Locktite the pins in place. You are done.
If you need to, harden and grind them. Or turn it from hardened and tempered steel.
Oviously, only serves for the diameter.
The width shouldn't be a problem if you cut two gage blocks to fit inside as a go-no go. :D


Nick
m1.jpgm2.jpg
 
Finish bore that little lip with your grooving tool after you cut the groove. Hold better than +/-.001 on the diameter of that little lip, and your groove is good.
 
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