Razor Thread Conundrum

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I can't fathom this out. Any ideas?:

I tried the R41 head on my new bulldog handle. It wouldn't get past the first rotation. Even with some 'applied mechanical bias' it wouldn't screw any further.

Assuming there was a problem with the bulldog, I pulled out a few different razors: GC, Yaqi, Marvel and the 3one6. Every one of these heads screwed on to the bulldog with no resistance. Similarly, the R41 head screwed on to all those handles with no bother.

What's going on?
 
I can't fathom this out. Any ideas?:

I tried the R41 head on my new bulldog handle. It wouldn't get past the first rotation. Even with some 'applied mechanical bias' it wouldn't screw any further.

Assuming there was a problem with the bulldog, I pulled out a few different razors: GC, Yaqi, Marvel and the 3one6. Every one of these heads screwed on to the bulldog with no resistance. Similarly, the R41 head screwed on to all those handles with no bother.

What's going on?

Where did the bulldog come from? If it's from the US it may be using some perverse measurement instead of metric.
 
I can't fathom this out. Any ideas?:

I tried the R41 head on my new bulldog handle. It wouldn't get past the first rotation. Even with some 'applied mechanical bias' it wouldn't screw any further.

Assuming there was a problem with the bulldog, I pulled out a few different razors: GC, Yaqi, Marvel and the 3one6. Every one of these heads screwed on to the bulldog with no resistance. Similarly, the R41 head screwed on to all those handles with no bother.

What's going on?

It's Aliens for sure.
 
Dunno then, I have an iKon bulldog too and it fits everything. :unsure:
Just tried a few more razors. I think the tolerance on the bulldog is a little out. The R41 was fine on the General and Parker Slant handles but both of those heads couldn't screw in to the bulldog. I'll have to arrange a replacement from Connaught.
 
Most likely the bulldog has an American #10-32 thread. The R41, being German, certainly has an M5x0.8 thread.
The difference is tiny. The R41 screw can be up to 5mm in diameter, a #10-32 hole is made for screws up to 4.826mm.
There are tolerances. An M5x0.8 screw must be 5mm or less, a #10-32 hole must be 4.826mm or more.
If you're lucky the M5 screw is small enough and the #10-32 hole big enough to make things work.
If you're unlucky... you already know what happens when you're unlucky.

Then again... there might be a problem with your handle.
 
Most likely the bulldog has an American #10-32 thread. The R41, being German, certainly has an M5x0.8 thread.
The difference is tiny. The R41 screw can be up to 5mm in diameter, a #10-32 hole is made for screws up to 4.826mm.
There are tolerances. An M5x0.8 screw must be 5mm or less, a #10-32 hole must be 4.826mm or more.
If you're lucky the M5 screw is small enough and the #10-32 hole big enough to make things work.
If you're unlucky... you already know what happens when you're unlucky.

Then again... there might be a problem with your handle.
That sounds like it could be the problem. Thank you for the info. I'm not sure what the Colonial General thread is. If this is #10-32 also, there's definitely a fault with the handle. If it's M5x0.8, I'm unlucky with the tolerances as you've said.
 
Thread pitch is not an issue between M5x0.8 (0.8mm) and #10-32 (0.7938mm) - it's the diameter that's the issue (when the screw is bigger than the hole).
A thread pitch gauge is also not very useful for determining the thread of the hole inside the handle - it's for the screws.
 
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