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mcskipper
10-25-2009, 09:03 PM
Hi Guys,

Just stumbled on to a drawing of the Picatinny Rail Mount.
This is also a Weaver mount, but the groove dimension is .180" for Weaver

www.wikipedia.org/wiki/FileM1913A_Rail_CrossSection.svg
Part way down the page.
Double click on the box & it will go full screen.
It can also be found under Mil Spec M1913

I've been making my own scope mounts for years & this drawing would have saved a lot of time checking mounts I had on hand.

Did take the time after I made a few to make a gage. That was a BIG time saver.

How close did you guys get w/ your drawings?

Ken_Shea
10-25-2009, 11:29 PM
Had the correct dimensions so it was not a problem.

The link seems invalid, link to the drawing.

http://en.wikipedia.org/wiki/File:M1913A_Rail_CrossSection.svg

38_Cal
10-26-2009, 12:33 AM
Here's a link to the Brownells website tech department article I wrote for them several years ago, before they declared me "excess" to their needs. This not only gives the cross section, but the slot spacing and dimensions, which are also critical to the design.
http://www.brownells.com/.aspx/lid=10724/guntechdetail/Picatinny_Rails__Weaver_Rails__What_s_The_Differen ce_

Boucher
10-26-2009, 09:08 PM
What is the best sequence of cuts to make one of these on a milling machine? I made one on the top of a one piece barrell bedding block. I need to do another one.

Ken_Shea
10-26-2009, 09:41 PM
What is the best sequence of cuts to make one of these on a milling machine? I made one on the top of a one piece barrell bedding block. I need to do another one.

Byron, not sure it makes any difference really.
I usually face to needed thickness, drill, use a 90 deg double angle for the 45 degree and then the slots.

mcskipper
10-26-2009, 11:08 PM
I set the mount in the mill on it's side.
Make the cuts that make the.617"
Do the two 45's.

Note:
I found that most rings did not have a perfect 90 Deg. all the way to the bottom of the rings.
So I will always knock .010" off so that if you looked at the side of the mount there will be a small flat.

If you are going to make a number of these (And you will) I made a tool like a fly cutter with an index carbide insert.The insert is set so that I can get the 45 Deg. with out having to move the mill head off tram.

deth502
10-27-2009, 07:41 AM
http://www.biggerhammer.net/picatinny/

lots of other milspec prints in that site too.

Ken_Shea
10-27-2009, 07:48 AM
I use this for the 45's but the idea of the indexable insert is a good one. As I recall Enco is where it was purchased and is made in Japan, good quality.

http://www.use-enco.com/CGI/INSRIT?PMAKA=367-7110&PMPXNO=948042&PARTPG=INLMK32

Dimensions are not critical and you would really have to work at trashing a mount so don't get all caught on super precision with regards to this, rings are very forgiving.
I did not accuratly state the set up, while I do face off the top first the final height is finished last.
You can also buy these blanks for a lot less then it takes time and material to make but of course that is not the point and/or immediate need may dictate otherwise.

mcskipper
10-27-2009, 07:53 PM
I,m retired now so I have all day to carve out mounts and other things.
I need to get more of my own machines so I can stop bugging my pal.

Secondly, Must my mounts go on hand cannons and I like making a stiff steel mount and use 6 screws to hold them down.
The slots can be milled just where you need them. And I use a .125" ball cutter open up slot to .187" The radius spreads the strain better.

How are you guys doing the radius for the barrel?

Ken_Shea
10-27-2009, 08:43 PM
How are you guys doing the radius for the barrel?

Fortunate enough to have a cnc mill and using planer finish, when I didn't I used a ball mill, when done it would not be a perfect form fit but would contact on each side and the top, still very solid, usually close enough that you couldn't see any real appreciable gap, I saw it though and didn't really like it but it was all that I could come up with.

I am interested also in how others solve this problem.

mcskipper
10-27-2009, 10:14 PM
CNC is a great way to go. I would not have any idea as to how to turn one on.

You bet Ken!!!!!
There is a lot of sharp guys out there.

mattm
10-29-2009, 01:12 PM
For the radius I put the base vertical in the mill and use a boring head set to the radius i want and mill the radius.

You could also do it in the lathe with a faceplate and an angle plate or maybe set it up in a 4 jaw. I haven't tried either but I imagine it would work ok.