What is the best method to measure this hole

[James H Clark]

I used to have a job that would come in occasionally that was similar. I cut the center part of an old Ford brake drum and used the center hole to clear the shaft. It was roughly shaped in a crescent shape. I drilled and tapped for small set screws on each end. polished a radius on the ends of set screws. Used one of the lug bolt holes to provide a handle. Works great, took about a 1/2 hr to make. Used it like an inside mike, then checked the dia. with an outside mike.

JH

 

[lazz]

Thanks we have several option to try and compare results...

 

[Grinder74]

https://www.mscdirect.com/browse/tn...ArSuF0eb7vXNIY_G1K_-8ihHAp8b9eDQaAqf0EALw_wcB

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[Illinoyance]

An asymmetrical telescoping gauge like Slowmotion showed might work. Lock it collapsed. Stick it through one of the open holes in the bar. Feed it into the hole. Unlock the plunger and re-lock it. Back the bar out of the hole and mike the gauge.

 

[Silent_Man]

If you have ever done this, please explain. How do you push the Pi tape in the hole and get it squared up, and still read the markings?

I have not measured an ID, only ODs. However Pi Tape makes ID versions down to 3/4" so it must possible to do.

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[Mud]

This Interapid gage will do it and is accurate to .0001 or less on holes up to 6".

INTERAPID IRA 2 Comparator Gauge Set 79.111402 - 12-089-9 - Penn Tool Co., Inc

It's hugely expensive and delicate, I'd hate to send it out on a field job, but it does answer the question. I have one and keep it hidden away until it's absolutely necessary.

 

[gbent]

I have not measured an ID, only ODs. However Pi Tape makes ID versions down to 3/4" so it must possible to do.

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I didn't realize there were id Pi tapes. After watching their video, it looks like they are using an internal step to square the tape. That would be doable with a snug fitting split cylinder or a welders wrap a round. Having to read the tape with a mirror due to the boring bar being in the middle looks to be a greater challenge.

 

[hvnlymachining]

I have not measured an ID, only ODs. However Pi Tape makes ID versions down to 3/4" so it must possible to do.

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use a small mirror held at an angle ( think dental mirror) there are sold in a wide variety of sizes shapes and lengths from nearly all hardware stores, auto parts stores and tool suppliers. they also work great to find that socket that fell into never never land.

 

[Hodge]

This Interapid gage will do it and is accurate to .0001 or less on holes up to 6".

INTERAPID IRA 2 Comparator Gauge Set 79.111402 - 12-089-9 - Penn Tool Co., Inc

It's hugely expensive and delicate, I'd hate to send it out on a field job, but it does answer the question. I have one and keep it hidden away until it's absolutely necessary.

Correct me if I'm mistaken, but wouldn't the cutter bar interfere in getting a proper measurement?

 

[Zahnrad Kopf]

The Berco gauge is the better way. However, before I had that luxury I milled two flats on the bar and used internal mics between the bar and the bore. ( measure each side to accommodate for being sprung ) Lacking that, adjustable parallel against the flat on the bar with a pin against the bore. Add the adjustable parallel and the pin for total gap.

 

[Mud]

Correct me if I'm mistaken, but wouldn't the cutter bar interfere in getting a proper measurement?

If you can't reach in with that, you can't reach in with spring calipers either. There are shorter contact tips in the kit if those are too long to clear the bar.

 

[robadams0206]

These snap gages can be used in an empty hole in the bar. One end is spring loaded so you when you release it, both ends get pushed against the bore. They are good to a half thou.

View attachment 262749

Do you know where to get a set of snap/telescoping gauges like these?

 

[Peter S]

A while back I saw a You Tube video from Cutting Edge Engineering which shows a method similar to the offset tele gauge idea, but without the handle.

There is a hole through the boring bar. You put the compressed gauge in the hole and then run the boring bar into the bore, adjust the gauge to the bore size then reverse the bar back out of the bore. Remove gauge and check size with micrometer.

I can't recall if the gauge was spring loaded or screwed like an internal micrometer.

I don't like the idea of moving the gauge back out of the bore, but it probably works OK as long as your machining is OK....

I presume the gauge comes with the boring/welding equipment - Sir Meccanica. Looks like you could make something similar?

 

[jims]

I would measure the outside of tube . Then measure the wall thickness on each side of tube. Add the 2 wall thicknesses and subtract from od of tube.
old school.

 

[fciron]

This is a three year old post. No point answering the OP’s question now.

 

[EPAIII]

Well, rats! I had a good answer.

Good thing I read all the way down.

This is a three year old post. No point answering the OP’s question now.

 

[AD Design]

Well, rats! I had a good answer.

-That answer is......? Inquiring minds want to know. No BS, what were you going to suggest?

 

[michiganbuck]

Very crude one might set/hold a ball or diameter thing against the ID wall then feel a jo block stack to gauge from the round whatever to touch the boring bar then add half the boring bar diameter. likely get .oo1 or .oo2 accurate, so shoot for -.002 or -.003. smaller than the target.

Getting close (-.oo3) then use a bar of bent CRS that was surface ground to be a - .001/no and a +.0002/GO fit gauge.

Re: (This is a three year old post. No point answering the OP’s question now.)
-> Unless the Op is still waiting for a usable answer..

Agree inside spring caliper would be best/good/quick/.

Spring Divider Caliper, Inside Spring Caliper, Labor-saving Portable For DIY Tools DIY Hardware 150mm - Walmart.com

Arrives by Thu, Dec 15 Buy Spring Divider Caliper, Inside Spring Caliper, Labor-saving Portable For DIY Tools DIY Hardware 150mm at Walmart.com

www.walmart.com

 

[JBTR]

Do you know where to get a set of snap/telescoping gauges like these?

Just a tip, you're probably much better off if you start a new thread with a good descriptive title, to ask this question. A lot of people wouldn't bother to trudge through this 3-year-old thread to get to your question.