Bore Measuring

[JimM]

What do you guys use to measure the internal diameter of a hole when boring.

Is it simply a question of of using the 'back' jaws on a digital caliper or would a set of gauges such as these be a better idea

http://tinyurl.com/o9wztx

I know they're only cheap but I'm just getting 'tooled up' so every penny counts at the moment

Cheers

Jim

 

[cobra428]

That's the bore gauges I use. Smaller holes I have a set of pin gauges I got from Enco also helpful in setups.
Tony

 

[Metal Butcher]

I insert an {expanding hole gage} or {telescopic bore gage} in the hole or bore, Then after being locked in on the inner diameter they are removed and measured accurately. I measure using a micrometer.

The import gages are not very expensive, there are other more expensive ways and tools used to measure holes/bores.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94873

I have-and-use a small set, and a large set, of hole/bore gages.

This is what they look like;
Large Set- http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5649

Small Set- http://jjjtrain.com/vms/measure_transfer_inst/measure_trans_06.html

Remember this If you search on the internet, "Gage is a widely used alternative spelling of the word gauge."

Heres a link to some really nice stuff! http://catalog.starrett.com/catalog/catalog/PLH2.asp?NodeNum=22078&Mode=PLIST


-MB

 

[90LX_Notch]

Turn your own gauge(s) for the required diameter.



Make one smaller then what you need and gauge to it first or use drill bits depending on the diameter. Then take light cuts until the final gauge fits.

I did this recently for a project for my neighbor. I roughed the bore checking with my calipers. Then I used a drill bit as gauge to get within .004. Then I used a shop made gauge for the final diameter as I machined the last .004.

 

[kvom]

I recently got a set of expanding bore gauges. They showed that the inner jaws of my digital caliper were off by .003.

 

[Noitoen]

Turn your own gauge(s) for the required diameter.

Just an idea :noidea: Turn a gauge a little longer to the correct size and in the last few mm or in, make 2 or 3 steps of smaller diameter to aid in the last fit. scratch.gif

 

[mklotz]

The inner jaws of most dial calipers have minute flats on them which means that, while they can accurately measure the separation of two flat parallel surfaces, when used on a hole they acutally measure the distance between two very small chords of the circle. This ensures that they will always read low. If you own one, try measuring the ring standard for your inside mike with your calipers and you'll see what I mean.

True bore gages are hideously expensive and overkill for most home shops. The split ball and telescoping rod types shown in previous posts are very usable though they do require some practice to develop the right procedure and "feel" for using them. A set of pin gages is a worthwhile investment for any small shop since they can be used in more jobs that checking bore diameters.

 

[Stan]

Unlike Marv. I haven't been able to develop a good feel for bore gauges after thirty years of practice. Getting an accurate bore measurement is the toughest measurement I have to make. Consequently, I always make the bore first and then make the piston to fit the bore. It is much easier to polish down the piston than to enlarge the bore to fit.

 

[tel]

Just an idea :noidea: Turn a gauge a little longer to the correct size and in the last few mm or in, make 2 or 3 steps of smaller diameter to aid in the last fit. scratch.gif

For important bores that's what I do, with 0.005" and 0.002" undersized steps on the nose.

 

[JimM]

Thanks for all the replies guys, I've ordered the set from Chronos as it sounds like it will be useful

Also taken on board the other suggestions and no doubt will be trying them out as well in the weeks/months/years to come !

Jim

 

[rake60]

For small bore sizes I prefer my ball gauge set.

Here's a link to Enco's offering. Small Hole Gage Set
It works and feels very much like a telescopic gauge but takes less
of a feel to master.

Rick

 

[Tin Falcon]

I have used a variety of tools for checking bores.
AF tech school I learned with 'T" Gauges
I have a good small set of "T"gauges and small hole gauges the prices on the HF set are very tempting but have not tried them.
When I worked as a pro machinist We used dail bore gauges and bore mics and air gauges very precise. But very pricey and overkill for the home shop although I do have an air gage to set up one of theses days. Like Dave said when the order of Round tuits finally shows up.
Most recently Mrs falcon got me a .2-1.2 inside mic for my birthday.
And last but certainly not least . I have a set of Moore and Wright Sheffield hole gauges this is a set of 7 gauges that are adjustable transfer tools that have balls extending from the sides near the end so they will gauge from .125 to .500 inch .
Tin

 

[BobWarfield]

If it really has to be precise, dial bore gage. These are available for less money than you might think via eBay, but more money than you probably want to spend!

Nevertheless, deals are out there. I use these for bearing fits.

For everything else, I have the telescoping gages.

The advice to make a plug gage for your bore is excellent advice. It's easy to do and quite convenient to have one.

Cheers,

BW

 

[gbritnell]

As has already been stated, a bore gauge is great if you can justify the cost versus use. I served my apprenticeship using telescoping gauges (snap gauges) for most small to medium holes. I always had good luck with them but I developed a technique for using them. Measure once and check the size. Measure twice and see if that measurement matched the first. If it did you were generally good to go but if not, measure a third time to verify your measurement. I also bought a set of Starrett small hole gauges. These work but take a 'feel' to use them. After awhile I made a tool that would be as accurate as a telescoping gauge if not more. I made this around 1969 so there's possibly something out there similar today. It's not complicated, just a round bar with a square key along the bottom and a small dovetail cut into the end to hold one of my indicators. The moveable arm has a small ball tip made from drill rod and hardened and screwed into the arm. The arm is reversible giving me a range from .187 to 4.25 inches. The bar could me made longer but if would get a little unweildy. Usually when working up to my hole size I just put the ball on the moveable arm against my bore or slot and with the lock screw just snug I pinch the arm so that it slides out till my indicator reads. I then take a mike reading and adjust my cut. When I get close to size, .003 for example, I set the tool with my mike to zero first and then use it as a snap gauge. I find this is as accurate as what my machines will cut. Here's several pictures of my tool.
gbritnell

 

[90LX_Notch]

gbritnell - Damn, that's cool. If I ever get a mill that's a definite build.

 

[BobWarfield]

Indi-calipers!

Or is it a Dial-Test-Caliper?

Ingenious!

BW

 

[bob ward]

gbritnell, that is GDF brilliant.

 

[John S]

I like it, that's really neat and far better than the kludge i have used over the years.

JS.

 

[gbritnell]

Hi John,
Similar idea, just a different way of getting there. I thought about making a fine adjust screw for mine but it would need to be released whenever the jaw was turned around for long or short measurements. Maybe I'll look into it a little farther.
gbritnell

 

[ozzie34231]

Beautiful Britnell.
I assume you broached the internal keyway???
Ozzie