Tips/Techniques 3 pin check for holes larger than gage pin

[slow-poke]

This is an interesting find..... https://holecalc.com/

Fairly common to want to measure a hole diameter larger than your largest pin gage (1/2" in my case)

By combining three pins you can accurately make a larger pin with three smaller gage pins

So for example I want a 1.000" pin

I use 0.5" + 0.499" + 0.348"

Next time I need to measure a bore, I'm going to compare results with telescoping gage, I'm guessing this method will be more accurate.

 

[YotaBota]

Bookmarked, thanks. That is a neat way to find the i.d. of a bore.

 

[Proxule]

So what do I do when I have no pins to start with ?

 

[Susquatch]

So what do I do when I have no pins to start with ?

Oh so many ways.....

Probably the best is cerosafe.

From best to worst

Use an air gauge - very expensive. if you have one, I wanna be your buddy!

Use cerrasafe - you melt it like solder and pour it in on top of a cloth plug. It shrinks when it cools and can be removed. Remarkably, it then starts to expand to the original diameter after so much time. It also comes with a time chart to calculate expansion vs original bore. Then you can measure the casting with a standard micrometer. It takes time to use cerrasafe but it's an amazing solution. Highly recommended. My favorite.

Pin gauges - although highly rated, I'm not a big fan. Too easy to get a bad fit because of burrs and other problems.

Inside gauges.

Inside calipers.

Measure the total OD, then subtract the two walls.

Use a tapered wedge hole gauge

Use drill shafts

Use an optical gauge

Prolly a few I forgot.

 

[Mcgyver]

I think I'd go nuts trying to find the the combo of three pins that fit. i've a lot of bore measuring stuff (right up to digital Mit boramatics), but 98% of the time small hole gauges and telescoping gauges are accurate enough. After them, if doing interference fits, bearings etc, the thing to get imo are dial bore gauges.

 

[Proxule]

Lol, what a reply. I love the ideas. It was more of a teaser question.

As to the cerrasafe.
I use sulfer. Heat it up enough to melt and pour. Much like the cerrasafe. Especially nice for rifle chambers-throat.

Thanks again.

 

[YotaBota]

I have a bunch of teaser suggestions but this is a family show and I don't know you well enough.

 

[jorogi]

Calibrate your fingers, jam them in the hole till you find the right fit. Easy peasy.

 

[Proxule]

I have a bunch of teaser suggestions but this is a family show and I don't know you well enough.

Sky's the limit with me. Tease away

 

[Susquatch]

As to the cerrasafe.
I use sulfer. Heat it up enough to melt and pour. Much like the cerrasafe. Especially nice for rifle chambers-throat.

I am surprised to learn that sulphur shrinks enough to remove from a chamber. How long do you have to wait for it to return to the cast dimension? Does it work in rifling too?

Cerosafe shrinks for a few minutes after hardenening and then returns to the pour size. Does sulphur do that too? Cerosafe is readily available from many sources, is very easy to use, is very reliable, and is consistent. So I confess that I'm quite surprised by your use of sulphur instead.

 

[Proxule]

I am surprised to learn that sulphur shrinks enough to remove from a chamber. How long do you have to wait for it to return to the cast dimension? Does it work in rifling too?

Cerosafe shrinks for a few minutes after hardenening and then returns to the pour size. Does sulphur do that too? Cerosafe is readily available from many sources, is very easy to use, is very reliable, and is consistent. So I confess that I'm quite surprised by your use of sulphur instead.

It neither grows or shrinks once it has been cast and set or cooled down, It is however very brittle!
I mix say 10% or so graphite into the mix and it releases much easier.
No need to rush and measure dimensions as it does not shrink or grow with age, It will how ever oxidize and change to a much darker yellow with age.
I enjoy working with it.

I was taught by the "old timer", what ever that means. And he pushed a can of sulfur over the table and said this should last you...... forever.
So that is really the only reason I have not tried cerrosafe.

 

[Susquatch]

So that is really the only reason I have not tried cerrosafe.

If it works, it works.

Apparently, dusting sulphur powder on the bottom of your pant legs and shoes is also a good way to repel ticks and chiggers.

 

[CWret]

Cerrosafe - never knew about that stuff. Now I’ll have to get some. Don’t know how i managed without it! Thanks, i think.
For others in my boat - here’s a short video of using cerrosafe in a barrel chamber. He also compared it to using sulphur:

Use an air gauge - very expensive. if you have one, I wanna be your buddy!

That’s a good reason NOT to buy an air gauge.
But - please explain- what is an air gauge?

 

[historicalarms]

One thing to be aware of when using sulfur for a chamber casting...the fumes that come off that stuff can be very nxious when being heated, always do it outside with a breeze blowing and stay upwind. Sulfur can have enough H2S residue in it to knock you down. and it dont take much of that stuff to kill a person.
That being said I have used sulfur a few times and once got a bit sick for a couple days but come out of it seemingly unharmed.
another point is that you can strengthen the brittleness by hanging a length of some kind of cord down the center of the bore you are casting, it seems to hang together better if you give it a backbone.

 

[Susquatch]

That’s a good reason NOT to buy an air gauge.
But - please explain- what is an air gauge?

First of all Cerrosafe is as safe as melting lead. I do it indoors all the time. You don't need to boil it, just melt it.

I was NOT advocating air gauges. They are WAAAY too expensive. But many bore manufacturers have them and use them to measure bore IDs to 50 millionths of an inch. That's 0.00005 or half of a tenth. More accurate systems exist but that's plenty accurate enough for me.

Air gauges funnel air into a plug with exit holes around its diameter. You stick the plug into the bore and them measure the back pressure against calibrated standards. You need lots of plug gauges for the various diameters and charts to plot diameter vs pressure.

 

[CWret]

measure bore IDs to 50 millionths of an inch.

Interesting concept and impressive accuracy

 

[Susquatch]

Interesting concept and impressive accuracy

You can get tenths with cerrosafe.

 

[mbond]

I am surprised to learn that sulphur shrinks enough to remove from a chamber. How long do you have to wait for it to return to the cast dimension? Does it work in rifling too?

Cerosafe shrinks for a few minutes after hardenening and then returns to the pour size. Does sulphur do that too? Cerosafe is readily available from many sources, is very easy to use, is very reliable, and is consistent. So I confess that I'm quite surprised by your use of sulphur instead.

does the rebound happen as the material changes temperature or for a mechanical reason?

 

[Proxule]

does the rebound happen as the material changes temperature or for a mechanical reason?

Sulfur does not shrink!
Or are you referring to cerrosafe?

 

[Susquatch]

does the rebound happen as the material changes temperature or for a mechanical reason?

I am pretty sure it's a mechanical response because it is very time sensitive and the material would have temperature stabilized almost right away. It keeps changing days later. Here is a quote from Brownells for the curious.

"There are various products on the market which can be used to make a cast of a chamber. To be certain that the product we are offering you is the best and most practical, we contacted the basic manufacturer. They recommended Cerrosafe because of its unique features. Unlike Woodsmetal which swells upon cooling and cannot be removed from a chamber, Cerrosafe shrinks during the first 30 minutes of cooling and then at the end of an hour, is EXACTLY chamber size. At the end of 200 hours it will have expanded approximately .0025'. This factor is well known by all toolmakers and they will take it into consideration when making dies or reamers or gauges from your cast - if you will tell them the cast is of Cerrosafe. Cerrosafe melts between 158° - 190° F. It should be melted in a clean, iron ladle. Source of heat should be removed as soon as the alloy is completely melted, at which time it is ready to pour. The solidified casting should be removed from the chamber before, or when, it cools to room temperature. If allowed to remain in the mold over an hour, it will grip the chamber walls and be difficult to remove. Clean the chamber thoroughly, then plug the bore immediately ahead of the throat with a small rag - but not so tightly it cannot be driven out. If possible, pour the molten Cerrosafe through a small tube into the bottom of the cast, gradually removing the tube as the chamber fills. If the chamber is cold, warm it to room temperature or above before making the cast. When cooled, remove from chamber, using a rod or dowel from the other end. "

Here is a link to the Brownells product page.

BROWNELLS Cerrosafe Chamber Casting Alloy 1lb SKU: 080027100 | Brownells

Check out the BROWNELLS Cerrosafe Chamber Casting Alloy 1lb SKU: 080027100 available Online at Brownells Today and many more Reamers & Cutters products are available in our Tools & Cleaning Department.

www.brownells.com

It is available in a Canada from

Cerrosafe

Bar Weight and Size = approximately 1 lb. / 4½" L x 1½" W x ½" H Non-Eutectic Alloy Melting Temperature 160-190º F or 71.7-87.8º C Density .341 lbs./In3 9.4 g/cc Shrinks initially, grows to .0000” in 1 hour and continues to grow to .0025”. Chamber Casting Alloy. Brownell Cerrosafe

boltonmetalproducts.com

And here is a photo of the expansion rate information. Note that this is inches per inch. Also note that it is all done expanding after 200 hours. I like to remove it at 30 minutes and measure at 1.5 hours. If I miss the 1.5 hr window, I just let it sit for two weeks and then calculate the change based on 0.0051 per inch.