Anyone Know What Size Hex These Are?

Hello World,

I don't have a good assortment of hex wrenches to try but my 8mm seems to fit - but pretty tight - so I bought a 5/16 inch hex thinking that must be it and it also does not fit perfectly. I've already rounded one bolt a bit so I thought I would try asking you folks.
Here is a picture of the bolt. They are all around our HMMWV - in the bed and also inside the cab and most hold D rings to the floor.

CARC paint will make it a tight fit. Have you looked it up in the parts TM?

Those are USS threaded bolts so 5/16 would be the listed size, having said that 8MM is a better choice as it would be tighter. ( would rather fight the 8MM Allen socket to free it from the bolt than to strip them)

I have had these that are a bit corroded and hell to get out, some heat and penetrating oil on the nuts/threads will help, sometimes you just have to cut them off underneath with a torch.
I bought a lot of 100 of these flat head bolts so I always replace them.

Mogman said:

I have had these that are a bit corroded and hell to get out, some heat and penetrating oil on the nuts/threads will help, sometimes you just have to cut them off underneath with a torch.
I bought a lot of 100 of these flat head bolts so I always replace them.

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@Mogman - Is there a separate nut on these under the bodywork, or are they those nuts attached to the body? Also, where did you buy the 100 od these bolts? Are the ones you bought the same as the original part? I'm afraid I have damaged on already and will need to replace it. Perhaps some more before I am done if I am unlucky.

I just fit a T-50 bit in mine.

BadAmish said:

@Mogman - Is there a separate nut on these under the bodywork, or are they those nuts attached to the body? Also, where did you buy the 100 od these bolts? Are the ones you bought the same as the original part? I'm afraid I have damaged on already and will need to replace it. Perhaps some more before I am done if I am unlucky.

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Yes there is a nut and washer under the body, IIRC the ones I got were 1/2-13X1 1/2" I just picked them up on fleabay by size not part number
Here is the part numbers in case you want the real deal,
18 PAOZZ 5305000522232 96906 MS24667-77 SCREW,CAP,SOCKET HE 1/2-13 X 1.75.. 6
This is from TM 9-2320-280-24P-1, figure 199 reference number 18

They are 5/16 hex but they seem to have the "heat to remove" loctite on them from my experience

GeronimoK9 said:

I just fit a T-50 bit in mine.

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@GeronimoK9 - I think mine are hex / allen heads.

Mogman said:

Yes there is a nut and washer under the body, IIRC the ones I got were 1/2-13X1 1/2" I just picked them up on fleabay by size not part number
Here is the part numbers in case you want the real deal,
18 PAOZZ 5305000522232 96906 MS24667-77 SCREW,CAP,SOCKET HE 1/2-13 X 1.75.. 6
This is from TM 9-2320-280-24P-1, figure 199 reference number 18

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@Mogman - Thank you. I do not have that manual, I will go and find it.

DREDnot said:

They are 5/16 hex but they seem to have the "heat to remove" loctite on them from my experience

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@DREDnot - I think my 5/16 fits bet - 8mm seems pretty tight but might also work. I think I will need to heat these bolts but I do not have a torch so do you think a heat gun would work?

Mogman said:

This is from TM 9-2320-280-24P-1, figure 199 reference number 18

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@Mogman - Found the TM and yes that is exactly the bolt part. figure 199 does not show the nut and washer under the body though.

The bolts I am trying to remove are holding the radio cable channel guard to the bed. I want to remove the cables and see if I can put some insulation or gasket material under the channel to try and stop rain from flowing from the bed into the cabin. See photo.

I think you need a torch. One of those home depot brazing kit units that comes with a screw on torch head