How to mill concave radius on scope rail for round action

[cbailey1956]

I have a 1.350 diameter round action (10x 22lr) that I would like to mount a one piece pic rail on. I would like to set my scope farther back and higher than I'm able with the traditional dovetail setup. I have a manual mill and did achieve this thru trial and error (4 hours). I used a small fly cutter and tilted the head at 50 deg in the x axis. Initially I set the fly cutter to cut a 1.350 diameter circle but that did not cut the proper concave for the action. Kept making the flycutter smaller and smaller untill there was a good fit to the action. But is there a formula for this,, or easier way. Have looked but failed to find. Dro installed has no program for this so its basically a 3 axis counter. Thanks,

 

[paperpuncher]

Boring Head works

 

[Walt Krafft]

Cut a shallow V. Maybe 15 degrees per side. Bed it if you want it precise.

 

[cbailey1956]

Have thought about leaving it with rough ridges and bedding it. It actualy turned out fairly smooth and fits good but who wants to spend 4 hours and then retramming the head. Nice way to spend a hot day though.

 

[Skunce]

Try this: https://silios.gr/calculators/large_radius.php

I used it to cut a 6" radius with a fly cutter once.

 

[cbailey1956]

Thanks

 

[ridgeway]

You will find that it will end up cutting more of an ellipse rather a true radius.

 

[LVLAaron]

You'd have to search around this forum, Dave Tooley had some pictures of his setup doing this. Basically, boring head.

 

[marazzi59]

Check out Joe Pie on YouTube, Advanced Innovations. He has a video about milling a radius

 

[Alan Warner]

Cut coordinates with a ball end mill. Do the trig with incremental steps. I like using the same incremental angle steps.

 

[DaveTooley]

There's a formula that takes the cutter diameter and the desired radius then gives you a number. Then there's a chart that takes that number and gives you the angle to set the milling machine head. For 1.350" I think it's a 1" diameter cutter and 44 1/2 degrees. I always make a trial cut on a piece of scrape. I'm headed out of town in a few minutes but someone remind me next week and I'll scan and post the chart.

 

[boltfluter]

Cut coordinates with a ball end mill. Do the trig with incremental steps. I like using the same incremental angle steps.

Alan makes a good point. This will make a nice radius and there will be a little room for bedding if you feel the need.
Paul

 

[cbailey1956]

Thanks for the inputs, looking forward to Daves chart after he has a vacation. enjoy the 4th weekend all

 

[Tucker65]

How to cut a scope base

Making a scope base today. I thought some of you could use this. Pretty simple and you're only limited by your imagination. I make Remington bases using the actual offset from front to rear. I use a stacked feeler gage to get the desired cant. I'm making a base for a 1 1/2" diameter action with...

forum.accurateshooter.com

 

[LVLAaron]

Have you checked with Murphy Precision for what you need?

 

[WSnyder]

But is there a formula for this,

Marc Klotz website has a program that’ll calculate tilt and cutter diameter. I’ve posted the link on this forum before.

Dave Tooley posted a formula on this forum awhile back. I have it saved but you can probably search and find it faster than I’ll get to it.

FWIW This method cuts an ellipse, not a perfect radius. You want to (and it will) create an ellipse where the outside edges touch first rather than the center.

Edit: Doh! Tooley posted above

Edit: The Marc Klotz website is down, not available. Hopefully it’s temporary. I have the radius.zip file saved.