Installing a tang sight

[Creedmoor]

I recently picked up a nice condition Winchester Model 94 in 30-30.  This rifle was made in 1970 so it’s not a “pre-64”.  With the rifle I got a Lyman #2 Tang sight made for the Model 94.  The sight mounts with two screws on the tang.  It came with a long screw which replaces the one existing screw and a short screw which will need to have a hole drilled and tapped in the tang.  I have a couple of questions.  First, will I hurt the value of the rifle by drilling and tapping that second hole in the tang?  Second, how hard is it to do this yourself?  Third, how do you make sure that you get the hole centered properly?  I would imagine that the best way would be to mount the sight using the one long screw and then somehow center punch the exact center of the opening for the second screw.  It is hitting the exact center that concerns me.  Also, is the tang of such hardness that it can or can’t be drilled easily?  Lastly, what is the thread size I will need to get a tap for?  Appreciate any advice you all can provide.
 
 
 

[gunnut69]

Last question first..call lyman and ask about the screw size but it is likely 8x40. Brownells, who sells these and other sights will also gladly answer that question, as well as sell you the tap and drill you will need. The tangs arent' all that hard, although the 94's of that era can be a pita due to inclusions in the metal.. It won't hurt the value at all.. To find the correct spot use a dial calipher and measure the tang at the position the screw is to inhabit. A centerline can then be determined by measuring center from both sides. Transfer the hole to the correct point on the centerline by mounting the other screw and making a center punch using the correct transfer punch. These are specially sized punches that have a sharp point on one end. Chose one that fits the thru hole tightly and punch. A drill press will ensure a perpendicular hole and use plenty of TapMajic lube when threading the hole.

[Creedmoor]

Thanks gunnut69,

I kind of figured that was the correct way to go.  Although I didn't know about the transfer punch, I assumed some sort of tool must exist like it.  I do a lot of woodworking and we use a tool called a "vixbit" to center holes through hinge screw holes and other hardware.  Now, would it be less expensive to just have a smith do this little job than to buy the drill, tap and transfer punch?  I assume Brownells can also supply the transfer punch - they have everything!

[gunnut69]

Around here a smith would likely charge between $12-20 to drill a hole and mount the sight. A drill bit and tap would be less than $5 and the transfer punches come as a set. I bought mine from 'HarborFreight' for less than $6 a set(get the "wire guage" set). You will need a drill press but when the install is over you'll still have the tools.. Maybe next time,,,

[Creedmoor]

Ah, good news!  I was assuming the transfer punch would be spendy.  I already have a drill press and harbor freight is not far away.  I think I'll give it a wack.  Is Brownells the only decent source for taps/drills?

Thanks gunnut69 (why 69?)

[gunnut69]

No. The sizes most often used in guns are a little hard to locate but most machine shop supply houses, such as ENCO, have what you need. I prefer the carbon steel taps as they are easier to shatter when you break one off in the hole(notice I said when). For a tang you can use a standard tap. There are three kinds of tap profiles Standard(thru hole), plug and bottoming. They are listed in desending length of lead, with the bottoming being the shortest, it is used to cut those last couple of threads in a blind hole. Remember you should use some kind of lube when tapping. Brownells reccomnds cutting fluid and I've used 'TapMajic' for years with great success.