1/4" to 3/8" screw on tripod head..

I have a knock off version of the Velbon ph 368 head. Does anyone how to remove the 1/4" screw as seen in the image below?

Try a screw driver....

Issue is probably getting sufficient force on it to break the bond of Loctite or similar thread lock adhesive.

A coin (Penny, Dime, Quarter) works like a charm,
and is always available.

Jim

That can be a problem because people use Loctite without knowledge and it can be near permanent on small thread diamters for which it isn't intended. On small thread diameters I recommend the use of clear nail polish. It holds but the bond can readily be broken.

I would attack your problem by carefully examining for any residue. If you find some blue residue you might get it off easily with a screwdriver and some heat, assuming there are minimal plastic parts nearby. If there is red residue your are likely in trouble anyway you attack it.

Clarification on common LocTite products, by color.
Blue is "Medium Strength" and for 1/4" Thread or larger.
Red is High Strength - Permanent" type for 1/4" Thread or larger.
Pink is "Medium Strength" and for smaller then 1/4" Thread.
Red for smaller threads is available, but not common in consumer retail market.

Blue and Pink are generally weak enough to break free with a screwdriver alone. If too difficult, apply heat carefully, such as from a hair dryer or tip of a soldering iron, depending on situation. You must consider what else is getting heated up (i.e. plastics)!

Red is considered Permanent, do not attempt to remove by screwdriver alone. It is easily removed after applying heat as described above. All of this is based on Mfg supplied information. I use at least 4 types of Loctite on a regular basis.

Jjwheels723 wrote in post #16104649
A coin (Penny, Dime, Quarter) works like a charm,
and is always available.

Jim

Great idea, thank you sir.

CanonCameraFan wrote in post #16105925
Clarification on common LocTite products, by color.
Blue is "Medium Strength" and for 1/4" Thread or larger.
Red is High Strength - Permanent" type for 1/4" Thread or larger.
Pink is "Medium Strength" and for smaller then 1/4" Thread.
Red for smaller threads is available, but not common in consumer retail market.

Blue and Pink are generally weak enough to break free with a screwdriver alone. If too difficult, apply heat carefully, such as from a hair dryer or tip of a soldering iron, depending on situation. You must consider what else is getting heated up (i.e. plastics)!

Red is considered Permanent, do not attempt to remove by screwdriver alone. It is easily removed after applying heat as described above. All of this is based on Mfg supplied information. I use at least 4 types of Loctite on a regular basis.

Only qualifier I'll add to that is "What we call [colour]". Loctite has specific numbers they describe their various products; some may appear to be one colour based on the packaging but fall into a different category of adhesion. They also make a variety of other adhesives, which wouldn't be suitable for temporary or reversible fastening. I got a "blue" LocTite not too long ago and it needed a blowtorch to loosen it (3/8-16-1/4-20 thread adapter like in the OP's question).

"Pink" Loctite for small threads is unusual in the States. Blue (#242) and red (#271 I think) will likely need heat. Loctite says 450 deg F which may not be practical.

If you get it out, as I previously said, consider clear nail polish the next time. That is what was used years ago by most camera repair techs.

Take a 1/4" 20 screw( very common). Heat it on your stove or whatever to glowing hot.
Thread it into your 3/8 to 1/4 bushing on your tripod. Let it cool. Then you can use a screw driver or coin to remove it. The heat deactivates the thread-lock.
Good Luck.

Al