A Brief Photo-Essay

Frank · Post by **Frank** » Fri Feb 27, 2009 6:47 pm

staffwalker wrote:I bought ZZ Minus sets in increments of .001".

What is the difference between the Minus and Plus type?

Tano · Post by **Tano** » Fri Feb 27, 2009 6:59 pm

Also, how long are they

staffwalker · Post by **staffwalker** » Fri Feb 27, 2009 8:02 pm

I don't know what the difference is I'll have to leave it up to one of the machinists here to explain. I bought the minus because they are much cheaper. I figured since I didn't need them to measure things but rather to plug them into a hole so I could turn things on the Taig for my purposes it didn't matter. It hasn't, if one doesn't fit I just go .001 smaller or larger.

I believe all I have are two inches long, that seems to be the standard size. I would like to have some longer in certain situations such as turning or squaring a shank that's not quite right but have never seen anything other than 2". I use them for all kinds of things such as making a completely round straight shank. If I do a round shank by hand on the sander but can't get it exactly right I go to the Taig, find a pin that fits in the mortice, chuck up the pin, use a bearing center in the tailstock to prevent the weight of the bowl from throwing everything out of balance and turn it exactly round. In a case such as this it would be nice to have the gages longer so I could get a better grip in the chuck.

bob gilbert

staffwalker · Post by **staffwalker** » Fri Feb 27, 2009 9:28 pm

I have seen guys here who say place a dot of glue on the bowl to prevent the bearing center from making a small hole in a bowl when turning in the manner I described in my last post on this subject. When one does this then you are faced with removing the glue without leaving a mark. Since I didn't like to either sand out the hole or remove the glue I came up with something else a year or so ago which works very well. I tear off about two inches of duct tape, make a circle with the sticky side out and fold it together until one is left with a square of folded tape about 1/4 inch by 1/2 inch with sticky on all sides. I then hold it against the bearing center and move the center to press it to the bowl. The duct tape sticks to the bowl and prevents the sharp point of the center from making a hole. When finished remove the duct tape it leaves no residue.

bob gilbert

FredS · Post by **FredS** » Fri Feb 27, 2009 9:37 pm

Frank wrote:
staffwalker wrote:I bought ZZ Minus sets in increments of .001".
What is the difference between the Minus and Plus type?

Gage Pins (or Pin Gages) are available in five classes - XX, X, Y, Z, ZZ. XX's are manufactured to the tightest tolerance and are thus the most expensive. ZZ's have the loosest tolerances (+/-.0002 for pins under .825” diameter) and are thus the least expensive. As described above, these guys are technically using them as mandrels, not gages, so the ZZ class is perfect. They don’t care what the actual size is, they just use the one that fits the best.

Within the five classes, gage pins are further classified as either "plus" or "minus" pins. “Plus” size pins are exactly on size or slightly larger, while “minus” size pins are exactly on size or slightly smaller. So a 1/4" pin in a ZZ Plus set would be .2500"~.2504”, while in a ZZ Minus set it would be .2496"~.2500". “Minus” sets are the most common.

Frank · Post by **Frank** » Sat Feb 28, 2009 2:51 am

FredS wrote:Within the five classes, gage pins are further classified as either "plus" or "minus" pins. “Plus” size pins are exactly on size or slightly larger, while “minus” size pins are exactly on size or slightly smaller. So a 1/4" pin in a ZZ Plus set would be .2500"~.2504”, while in a ZZ Minus set it would be .2496"~.2500". “Minus” sets are the most common.

Thanks Fred, you confirmed what I had deduced about the Plus/Minus.

ToddJohnson · Post by **ToddJohnson** » Sat Feb 28, 2009 12:26 pm

FredS wrote:
Frank wrote:
staffwalker wrote:I bought ZZ Minus sets in increments of .001".
What is the difference between the Minus and Plus type?
Gage Pins (or Pin Gages) are available in five classes - XX, X, Y, Z, ZZ. XX's are manufactured to the tightest tolerance and are thus the most expensive. ZZ's have the loosest tolerances (+/-.0002 for pins under .825” diameter) and are thus the least expensive. As described above, these guys are technically using them as mandrels, not gages, so the ZZ class is perfect. They don’t care what the actual size is, they just use the one that fits the best.

Within the five classes, gage pins are further classified as either "plus" or "minus" pins. “Plus” size pins are exactly on size or slightly larger, while “minus” size pins are exactly on size or slightly smaller. So a 1/4" pin in a ZZ Plus set would be .2500"~.2504”, while in a ZZ Minus set it would be .2496"~.2500". “Minus” sets are the most common.

Now THAT is an explanation. All I know is if one ain't a finnin' I go for a nuther.

Todd

RadDavis · Post by **RadDavis** » Sat Feb 28, 2009 12:46 pm

Here's a nuther helpful hint for facing both sides of an insert if'n you ain't got and cain't afford a pin gage set:

Place a section of the material in the chuck, drill it, counter sink, and face the one side. Remove it, slice a piece off and then put a couple of drops of super glue on the faced side. Glue it to the closed chuck face as close to center as possible (it doesn't have to be perfectly centered), making sure that the super glue drops adhere to seperate jaw faces.

Face the other side and make it as thin as you want/need. Open the chuck, and the glued piece will pop off of all but one jaw. Give it a light whack, and it'll pop right off the last one.

Sand the glue off with 320 grit laid out on a flat surface, like a pane of glass.

Voila.

Rad

staffwalker · Post by **staffwalker** » Sat Feb 28, 2009 4:09 pm

Now that is a good one Rad, there are times when I am starting with a piece from my junk box so thin it is difficult to use with a pin gage. I've thought about super glue but never tried it, couldn't figure out how to unglue it. Never thought about using two jaws then opening. Duh, my brain tends to vary from long periods of trudging along to the very occasional streak of brilliance.

bob