Rem 700 8-40 Screw Upgrade

[Danpd]

Just a bit of an Insight into the process I use to ensure scope base holes are in alignment with the actions centreline....no more lost windage adjustment!

 

 

Todays Victim is a Remington In 25-06 which I re-barreled last year. The customer was having issues with the factory screws so he sent it in for the upgrade.

 

 

 

First I set up the action in the vice with a precision ground mandrel located in the raceway.

 

 

Then I indicate across the flats of the action raceway to ensure it is level.

 

 

 

Then I indicate off of the mandrel to ensure it is level in the Z axis

 

 

Then the same for the X axis

 

 

Next I ding both sides of the mandrel to find the centre

 

 

 

 

Then I'll insert a close fitting pin gauge into the rear most scope screw hole and find its position

 

 

In this case the hole was about .006 out of alignment with the true centreline of the action.

 

 

Touching off the first tool to set the Work offset.

 

 

 

Then The Minor diameter of the new hole is helically bored with a 3mm 4 flute carbide endmill. An endmill will not follow an existing hole, and as such we re-establish the new hole in the correct position.

 

 

Checking the minor diameter with a pin gauge.

 

 

Now the new threads are milled at 40 Tpi with a 2.8 mm single point carbide threadmill.

 

 

The end result of which is lovely new threads cut in the correct position.

 

[gunner]

Proper job , thanks for sharing .

[Simon J]

Not like my school metalwork class at all - we never got a thing right!

[munkjack]

Plus one the metalwork classes id don't think my meter metal rule would cut it

[trucraft]

Very nice work Paddy.

[MJR]

Nice write up and some nice gear there too. Thanks.

[Danpd]

Heres a close up of the expensive little carbide chappy that makes it all possible.

 

[John MH]

Interesting, thanks.

[Offroad Gary]

Nice job Paddy, same upgrade as the Tango 51.

[borden]

excellent read paddy, its nice to read about craftsmanship

[bradders]

Must be nice to have that kind of machinery

I've never seen thread milling done before

[AckImp]

Quality post, thanks for sharing. Closer to watchmaking than it is to gunsmithing! I didn't even realise that a thread could be cut like that. I'd imagine the "little carbide chappy" is just as expensive as you've intimated!

[Danpd]

Quality post, thanks for sharing. Closer to watchmaking than it is to gunsmithing! I didn't even realise that a thread could be cut like that. I'd imagine the "little carbide chappy" is just as expensive as you've intimated!

They aren't so bad, around £65 a pop...... but they will break very easily, you also need to run them in high precision chucks, as the better the TIR you can get them spinning at the longer they will last. So with all that in mind figure in you are around £300 on the tooling just to mill the thread.

[Big Al]

They aren't so bad, around £65 a pop...... but they will break very easily, you also need to run them in high precision chucks, as the better the TIR you can get them spinning at the longer they will last. So with all that in mind figure in you are around £300 on the tooling just to mill the thread.

 

And are you really noticeable more accurate than it would be running a tap down the hole?

[Danpd]

And are you really noticeable more accurate than it would be running a tap down the hole?

As long as the minor diameter of the screw hole is established correctly then no. The benefit to thread milling is that it gives you control over the fit of the thread and provides a stronger thread form due to a larger percentage of thread engagement. I can also use the same tool to cut metric threads, or to mill threads to within 1 pitch of the bottom of a blind hole.

[Big Al]

As long as the minor diameter of the screw hole is established correctly then no. The benefit to thread milling is that it gives you control over the fit of the thread and provides a stronger thread form due to a larger percentage of thread engagement. I can also use the same tool to cut metric threads, or to mill threads to within 1 pitch of the bottom of a blind hole.

 

I read the thread with interest, its nice for people to see the methods and gear you used to establish correct hole centers, when it reached the point of cutting the thread I was thinking to myself you used the milling method because you could rather than because the job really needed it. Nothing wrong in that of course as its made a good job of it but probably nat as cost effective as a simple chuck aligned tapping operation. I appreciate the use of this single point tool for other applications as you have described, that a nice set-up you have there, something I would very much like myself

[pwinnall]

As long as the minor diameter of the screw hole is established correctly then no. The benefit to thread milling is that it gives you control over the fit of the thread and provides a stronger thread form due to a larger percentage of thread engagement. I can also use the same tool to cut metric threads, or to mill threads to within 1 pitch of the bottom of a blind hole.

Hello Paddy,

Your attention to detail and process are excellent!!

I'm sure I will be using your services soon.

Kind Regards

Phil