Glow Plug Thread?

[Dennis Leonhardi]

What is the thread of a common glow plug?  TIA!

Dennis

[Brett Buck]

What is the thread of a common glow plug?  TIA!

Dennis

1/4-32

   Brett

[Dennis Leonhardi]

Thanks Brett!

Dennis

[Tim Wescott]

1/4-32

   Brett

AKA NSF, or "National super-fine" thread.  If you're looking for a tap.  Which McMaster-Carr sells.

[Brett Buck]

AKA NSF, or "National super-fine" thread.  If you're looking for a tap.  Which McMaster-Carr sells.

   No. UNEF, National Extra Fine

     Brett

[Tim Wescott]

   No. UNEF, National Extra Fine

     Brett

Whuups.  Thanks.  McMaster still sells them, though.  Or at least they did when I bought mine.

[Steve Helmick]

AKA NSF, or "National super-fine" thread.  If you're looking for a tap.  Which McMaster-Carr sells.

Tsk, tsk, tsk. Tim, Tim, Tim...

By the way, Fox Mfg. used to sell 1/4-32 taps. Maybe dies or die nuts, too. I think the tap I have came from them. A shop I worked at had some 1/4-100 (yes, 100 tpi) taps. They had to get them for a special job for somebody, and had to special order them and wait 6 months or so to get them. I'm not sure if the customer lost interest or not. Moral of the story is that you can get anything  you want, if you are willing to pay enough and wait for it to be made.  Steve

[Brett Buck]

Tsk, tsk, tsk. Tim, Tim, Tim...

    I wouldn't have said anything if it was not phrased as a "correction" - again.

By the way, Fox Mfg. used to sell 1/4-32 taps. Maybe dies or die nuts, too. I think the tap I have came from them. A shop I worked at had some 1/4-100 (yes, 100 tpi) taps. They had to get them for a special job for somebody, and had to special order them and wait 6 months or so to get them. I'm not sure if the customer lost interest or not. Moral of the story is that you can get anything  you want, if you are willing to pay enough and wait for it to be made.  Steve

   I was amazed at what you could get off-the-shelf, even at McMaster (as long as they are conventional sizes)- 1/4-80, 12-36, etc., in three varieties.  It's a lot more expensive than a pedestrian 1/4-32 or a 5-40, but apparently you can just call them up and have it in the mail tomorrow.

       Brett

[Howard Rush]

Moral of the story is that you can get anything  you want, if you are willing to pay enough and wait for it to be made.

A principle being applied to the new flying circle at JCT Manor as we speak.

[billbyles]

    I wouldn't have said anything if it was not phrased as a "correction" - again.

   I was amazed at what you could get off-the-shelf, even at McMaster (as long as they are conventional sizes)- 1/4-80, 12-36, etc., in three varieties.  It's a lot more expensive than a pedestrian 1/4-32 or a 5-40, but apparently you can just call them up and have it in the mail tomorrow.

       Brett

Just an FYI - I had an ST .46 head that had a sketchy glow plug thread when I got it & I nursed it along for quite awhile until it finally stripped.  I thought "No problem, I'll just go put a Heli-Coil in it & go flying!"  So off I went to my local tool supply store from whom I have been buying for years & told them to order the 1/4-32 Heli-Coil kit for me, and Oh, by the way, how long to get it & how much money?  Two months & $146.00 for the kit.  Clarence Lee in Sunland, CA does the repair for $17.00.  Didn't even need my HP calculator for that decision. 

[Steve Helmick]

A good alternate repair is to tap the hole out for a suitable pipe thread, screw in a piece of brass pipe nipple with some Loc-Tite, then drill and tap that for 1/4-32. There is a 1/16" pipe thread...maybe that is it. I have done this, but don't think it was for a glowplug repair. IIRC, Magnum engines have a brass insert for the glowplug. Maybe OS? 

Another good repair is to make a button head out of the stock head (machine a new combustion chamber). Harder to do with a baffled piston, but that's the way Fox made their "kit" .35 head...the one that doesn't help anything. If Fox could do it, almost anybody could manage. They pinned the combustion chamber part to the finned "clamp" part to help align the baffle with the slot, but it was a loose slide fit. Not sure if that guaranteed good clearance or not. With Foxes, it was always important to "get all the screws in the right place" anyway, so should be expecting to have to fuss with everything. Seems to be something that goes along with minimum weight engines. Or minimal quality?    Steve