Are there any thru holes that are used for mounting the "grill" to the case? If so, it would be fairly straightforward to use depth mics or the tail of dial calipers to go through the holes to a flat surface. The flat surface could be something as simple as a 1-2-3 block.
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Need a super-sized micrometer
- Thread starter pbiYoung
- Start date
Great idea, but no thru holes.
I need drill and tap some mounting holes without penetrating the outside surface. Would like to get within .025 of the penetrating surface. The "grill" looking thing is simply a hump in the bottom to illustrate that the bottom of the box is not uniform thickness. I guess I should have drawn an arrow pointing to it that says "hump of unknown height". Maybe I'll update the drawing.
Thanks
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In that case, I would set up my drill press to stop .025" short of my support surface and drill. You ill want to prevent the box form lifting up by clamping firmly down. The thickness doesn't really matter.
For tapping shallow blind holes, I grind the point off my tap. In some cases, for plastic in particular, I modify a tap or bolt to cut the last one or two unformed threads.
Yep I was afraid someone would respond with that as soon as I mentioned drilling holes and stopping short of the bottom.
That definitely seems like the simplest and easiest solution but for discussion purposes what if your drill press wouldn’t reach the center where you needed to drill a hole? … and you didn’t have a friend with a big enough drill press to borrow?
Drill sacrificial holes for pins to use ?
That’s an awesome tip about the screw mod for blind tap fasteners !
Thanks
That definitely seems like the simplest and easiest solution but for discussion purposes what if your drill press wouldn’t reach the center where you needed to drill a hole? … and you didn’t have a friend with a big enough drill press to borrow?
Drill sacrificial holes for pins to use ?
That’s an awesome tip about the screw mod for blind tap fasteners !
Thanks
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That is a problem. You will probably want to need an idea of thickness then. Drilling with a hand drill is an iffy situation in any case. When you want to achieve .005" accuracy on your drill depth to within .025" of breaking through, it just gets worse.
You didn't mention what tools/equipment you have at your disposal or what the box material is. That might help to determine a solution to your problem. Is the reason for a non-through hole purely esthetic or something else? What is the estimated thickness and the tap size?
It's purely an academic discussion at this point. I already completed the task with solutions very similar to what you suggested with a little setup and jigging work. I thought though that it might be helpful to some members if there were other proposed solutions involving different ideas and equipment. Many threads on this site describe multiple ways to skin cats depending on ones budget, existing equipment , and skill level.
You touched on the original question and dilemma with your last question when you asked "What is the estimated thickness and the tap size?" That is what I was hoping to determine (by measuring) prior to deciding if drilling and tapping would be possible.
I purposely withheld relevant information to the project so as not to cloud the discussion and see if multiple ideas would surface regarding measuring something very difficult in the hopes that it might be helpful to others. Once it became clear that I wanted to drill a hole then the discussion became narrow focused to a solution involving holes. It did generate a good discussion and provided some different solutions. FYI the case was waterproof hence the need to avoid penetrating the surface.
Thanks for the input and the tap trick.
Hopefully more members might chime in if they know of another creative way to address the original measuring problem.
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he said to the accuracy of 5 thou (.005) a normal caliper would do that.
Just take some blocks either jo blocks or any measured blocks, and close it on the block, then zero it.
Then measure the inside.
You can even do it with an old style tool used the same with a block so you can get it out.
then measure the gap.
Just take some blocks either jo blocks or any measured blocks, and close it on the block, then zero it.
Then measure the inside.
You can even do it with an old style tool used the same with a block so you can get it out.
then measure the gap.
I would try something like this:
1) You need a pillar of metal, with flat upper and lower surfaces.
2) A relatively flat area to set up in.
3) A dial indicator and holder, with a long-ish arm, with as much travel as you can get.
Procedure:
1) Put the pillar in the center of the flat surface.
2) Mount the dial indicator to the flat surface, far enough away to allow for 1/2 of the width of the box.
3) Set up the indicator so that it’s just touching the top of the pillar, and zero it.
4) Carefully raise the probe of the indicator, and then sneak the lip of the box through the gap. Center the box, and then let the indicator probe rest on the bottom of the box. The indicated reading is the thickness of the bottom of the box.
Note that nothing needs to be particularly flat or level for this to work, but nothing can move other than the indicator probe.
1) You need a pillar of metal, with flat upper and lower surfaces.
2) A relatively flat area to set up in.
3) A dial indicator and holder, with a long-ish arm, with as much travel as you can get.
Procedure:
1) Put the pillar in the center of the flat surface.
2) Mount the dial indicator to the flat surface, far enough away to allow for 1/2 of the width of the box.
3) Set up the indicator so that it’s just touching the top of the pillar, and zero it.
4) Carefully raise the probe of the indicator, and then sneak the lip of the box through the gap. Center the box, and then let the indicator probe rest on the bottom of the box. The indicated reading is the thickness of the bottom of the box.
Note that nothing needs to be particularly flat or level for this to work, but nothing can move other than the indicator probe.
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Presumably he needs something that can get to the center of the 25" side. One like this might do the job:
OUTSIDE CALIPER 500MM - Precision measuring instruments | Limit
With flat shanks and adjusting nut.
limit-tools.com
I had a similar situation once and I bolted together three pieces of flat stock to make an impromptu caliper.. I was looking at +/- 1/16" though.
That's another good solution.
Its about 13 inches to the center where the measurement needs to be taken so I did try this with a set of 18" reach calipers that I have but they seemed a little springy at the business end and it was challenging to get repeatable measurements, but I suppose with a quality set of giant calipers you could get an accurate read.
Thanks