In the latest MA they say the glow plug thread is 1/4x28. When did they change it?

You would be pretty safe calling that a mis-print.

Sounds like a mistake to me, mine are still 1/4-32

Its a magazine I dont waste my time reading and wish I didn't get.

Same here!

I emailed the author. He admitted to, and apologized for, being confused. 1/4 x 32 it is. Even so, I thought this was a better than usual issue.

Well once upon a time there used to be quite a few different sizes of glow plugs.
At present we have two basic thread types, the regular 1/4x32 threaded glow plug and the Nelson plugs.
After that you have the short, intermediate (OS),  long glow plugs and 4 stroke type (OS F plug style) plugs , along with the Turbo plugs too.
My old vintage glow plug thread shows some of them http://www.rcuniverse.com/forum/m_10545790/tm.htm
At first they had big glow plugs designed to replace the spark plugs people were using at the time.
Champion even made glow plugs for a number of years too. Some of the early glow plugs looked like spark plugs.

Though I'm probably "young" by many (32), I find the older technology both nostalgic and pretty darn neat. I wish I lived closer to some of you folks that still have this stuff. I would be like a little kid in the candy store looking at your "loot".. haha.

although it has nothing to do with glow plugs, I still enjoy the MA magazine - at least it covers something besides just the latest ARF RC plane.. FF and CL articles are interesting, I figure I can always learn from what other folks are doing.

Were any of them ever 1/4-28?

Normally I would say no there weren't any 1/4x28 threaded glow plugs. But way back in the early glow plug days, there could have been some that were short lived.

+1

Bruce

The best use I've found for an MA magazine is to use it as a cutting board for small pieces. The articles are not worth reading, nor are they un-biased. So, after a few uses, I pull off the shreaded pages and have a fresh cutting board. I go through this process several times before using up the whole magazine. By that time, another MA magazine arrives.
Before I discovered this use for the magazine, they went straight in the trash every month.

When I first read this I thought it was a "RCU Thread" all about glow plugs! You know like club Saito or whatever. Silly me.

I usually don't read a lot of articles in MA, but I was interested in the subject of the referenced article, and saw the info on thread size. I immediately panicked! Two days before I damaged the thread on my (expensive) OS FS91 Surpass II / pump, trying to start a new plug into the hole. I pulled the head that night (just to make sure on debris had fallen into the engine) and chased the thread with a 1/4-32 tap. Seemed to work perfectly. After seeing the article, a furious internet search ensued. Every reference said glow plug holes are 1/4-32. I was relieved, and mystified as to the author's assertion that 1/4-28 is correct.

Strangely, the article said the 1/4-28 data was a correction to another article the month before, where he had (correctly) identified the thread as 1/-32. I have NO IDEA how the author in the following days was able to convince himself that 1/4-28 was the correct answer. Misprint had nothing to do with it. He went out of his way under a "correction" heading to spread the bad information.

Hope nobody ruins their heads trying to use the wrong tap.

Yes that 1/4X28 was a mistake. The fact that an occasional error appears should not be surprising except for you few who have NEVER made a mistake, I'm sure all one of you guys who are perfect will stop reading the magazine. Personally, having been in the hobby for some 70 years, I find the AMA magazine to be quite informative and covers most all types of modeling. I personally think they do a very good job for the money and provide a valuable service to the modeling community.
_____________________________

RIGHT BEHIND YOU I GOT 62 YRS AND STILL GOING STRONG IAM NOW 80

One day I went to the Home Depot for a 1/4-32 tap. The salesman assured me there was no such thing as 1/4-32 thread. Maybe the author ran into this same salesman.

THERE IS A 1/4 X32 TAP I GOT ONE FROM THE HOBBY SHOP

I would say someone had a DA moment.

+1 Rodney

Best thing I ever did was get a 1/4x32 die for cleaning up new plugs before installing. Apparently the plug's threads are just rolled and not precision cut from the factory. You would be amazed at all the shaving that come off of new plugs to make them right.

Ernie Misner

There ya go. Talking to a minimum wage earner at Home Cheapo. Most of the people working there are there to survive. May be knowledgeable in some aspects of the store but, machinist they are not, I bet.

Yes you have to special order the more unusual thread size taps and dies. Some engines use taps and dies intended for firearms too. So gunsmiths is a source for some too.  I ordered my 1/4x32 taps and dies from one of the specialty internet stores as well.

1/4-32 is National Extra fine. (NEF) You used to be able to order them through Sears. My current ones are Higley.