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[BigJ]

Welcome aboard!

Great advice above!

 

[Mysterious Mose]

In that case contact Rockwell and they will probably send you a new handle. The cap post will not last long if you continue with that razor.

I've written to Rockwell requesting a replacement handle.

 

[AimlessWanderer]

I have sometimes had a "head loosening" issues in winter, albeit with different razors.

I put it down to a cold razor being assembled, and the expansion of the screw post as the razor warms up. This would correlate with the OP saying this happens before the end of the first pass... i.e it starts off ok, but "let's go" as the heat from the hot water warms the razor through.

My solution... just give the head a secondary "nip up", once I feel it start to slacken. As I don't remove the blade between every shave, this will hold firm until I intentionally loosen the head, either for a periodic clean and flip of the blade, or to install a fresh one.

So personally, I don't consider this a razor fault. I haven't really noticed these issues in the warmer months, but it might have happened. Although, as I'm used to giving a razor a light secondary nip as needed, it wouldn't necessarily be a noteworthy event for me. I'd simply adjust as required and continue, without giving it a second thought.

 

[Mike M]

If the head is coming unscrewed then it is a fault with the razor. I have the 6C and find it a great razor though I tend to go for the R5/R6 plate and I have never had this problem with it.

 

[Invicta]

My solution... just give the head a secondary "nip up", once I feel it start to slacken. As I don't remove the blade between every shave, this will hold firm until I intentionally loosen the head, either for a periodic clean and flip of the blade, or to install a fresh one.

So personally, I don't consider this a razor fault.

It has been established in post #16 the handle is defective and has not been drilled and threaded deep enough.
The OP said; "As to the depth of threading in the handle as compared with the threaded post, the latter is about 6 turns deep, but the former is about 4 turns deep. I used a toothpick, not a match stick."
Any extra tightening, which the OP did try, will cause wear on the threads and early failure of the threaded zinc alloy post. Six threads is the minimum I would expect for adequate thread length as that equates to only ~ 5mm of threading contact. Using a washer will reduce that thread length contact.
This is a defective product and for Rockwell to replace.

 

[Mysterious Mose]

Rockwell has written me that they are sending me a replacement handle. Let's hope it works better.

 

[AimlessWanderer]

The OP said; "As to the depth of threading in the handle as compared with the threaded post, the latter is about 6 turns deep, but the former is about 4 turns deep. I used a toothpick, not a match stick."

I assumed that was four turns, PLUS the depth until the first turn starts, which looks as if that would span a couple of turns at least. If not, the OP wouldn't have had the head closed at the start of the WTG pass as I understood it.

Six threads is the minimum I would expect for adequate thread length as that equates to only ~ 5mm of threading contact. Using a washer will reduce that thread length contact.

General rule of thumb for thread engagement (not just in razors), is that the engagement length should at least equal the major diameter of the thread. At that point, the cross sectional area of the threads is at least the cross sectional area of the bolt. Though on on threads that are constantly used (tightened and loosened), a little extra engagement length can offset wear, so we are of similar thinking there.