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Sorry if this is a stupid question.

I have a tripod (cheap, Chinese, bought on Amazon) and I wanted to change the ball-head it came with to a 3-way head, so I bought a Velbon PH-157Q head.

When I unscrewed the ball-head from my tripod I saw this screw: http://postimg.org/image/c23ely0kf/

...which is obviously the right size for the head I just unscrewed, but too big for the screw hole on my new Velbon head:

http://postimg.org/image/ooh68trxx/

Basically...how can I screw the new head onto this tripod? Thanks for any help.

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You need an adapter such as this one (or this alternate one, or this one) that has a 3/8-16 hole on one side and a 1/4-20 screw on the other.

enter image description here

You can get them without the large flat circle, but they are more for adapting light stands and such. For a head on a tripod the larger round base will provide more stability, which is the whole point of a tripod.

From the comments below:

Actually, it looks like maybe all you need to do is remove the adapter that's already in the head... see that slot for turning it? Actually, on second look, the insert seems a little big for that, but... check it out.

and

All we can see of the brass insert is the head -- there's no way to tell what size socket it fits into. I agree with @junkyardsparkle that the slots cut into the insert are clearly meant to let you unscrew it. I'd try a large flathead screwdriver rather than a coin.

and

always possible that the brass insert has the equivalent of a bolt head to stop you screwing it too far in... Looks like it's clearly intended to be removable, so I'd try unscrewing it before splashing out on an adapter that may not be needed.

Based on Tom W's review under the review tab of the Velbon PH-157Q at Adorama, if the 1/4-20 insert is removed another insert with 3/8-16 threads must be used:

works as advertised; had bit of a tussle trying to get 3/8-16 bushing shipped, as advertised, but Customer service came thru- finally ... suggest you confirm available bushing sizes B4 ordering this item ...

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    Actually, it looks like maybe all you need to do is remove the adapter that's already in the head... see that slot for turning it? Actually, on second look, the insert seems a little big for that, but... check it out. – junkyardsparkle Sep 25 '15 at 2:02
  • Manufacturer page says it has a 3/8 socket... – junkyardsparkle Sep 25 '15 at 2:14
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    You have to click on the "panhead" tab after the link, sorry. It does look big, but threaded stuff can be deceptive that way... but possibly they use an insert for 3/8 models, too. – junkyardsparkle Sep 25 '15 at 3:03
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    @Calab, a lot of Amazon links went dead at midnight last night. Maybe it will come back on line. – Michael C Jan 1 '18 at 17:02
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    @Caleb Thanks for the ping, I forgot about this question, but in the meantime I've seen a few inserts just like this one. Posting an answer so I can add a picture. – junkyardsparkle Jan 1 '18 at 21:20
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While it sounds like it may not be true in this particular case, some heads with 3/8" native threads come with installed bushings to adapt to 1/4", and can appear to be larger than 3/8" due to a flange on the bottom. If you can't determine otherwise from the specs, it's probably worth checking before resorting to adding yet another adapter (and possible point of failure).

enter image description here This is a one such adapter I've encountered.

  • It may well be that the insert has a flange head (which is totally different from a bolt head as mentioned by Jerry C to a comment on the other answer), but if so the one pictured in the OP is still significantly larger in diameter than the one pictured in your answer. Based on a review by Tom W. in the PH-157Q head's listing at Adorama, a different bushing (insert) with 3/8-16 threads is needed, rather than the hole under the 1/4-20 insert being threaded at 3/8-16. – Michael C Jan 1 '18 at 21:38
  • That seems strange, but I'll take your word for it... maybe it's an attempt to shift towards a more robust and/or metric standard? I'll leave the answer as it may be useful for other cases, but I'll edit it to clarify that it may not always be the case. – junkyardsparkle Jan 1 '18 at 21:47
  • I suspect it may have something to do with the grade of aluminum used for the head's body. Softer metals require larger threads to tolerate the same amount of torque. One solution in many applications is to use steel inserts threaded into larger holes in aluminum. – Michael C Jan 1 '18 at 21:54

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