Cutting scope mount screws

R

Rascal

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What is the correct or best way to cut the small 6-48 screws that are used to fasten scope bases to receivers.

I have some that need to shortened.
 
Thread them through a price of flat stock with the appropriate hole drilled and tapped then grind it off flush at the length you need.
 
Even a mill bastard file will be quick if you don't need to shorten them too much... For small items I put the file in a vice and then hold the piece with some vice grips.
 
Thanks, I bought a Winchester 94 and found one rear mount hole stripped.

I bought a dozen oversize 6-48 screws ... They are .146 x 48 and I bought the taps as well.

Cost me $80 but it will fix the gun right.

I plan on doing all four holes.

Apparently the taps will rethread the holes with no drilling, I bought the taper and bottom tap and screws from brownells

http://www.brownells.com/optics-mou...er-146-48-screws-sku080-719-112-795-3103.aspx
 
Chuck them up in your drill by the head and file to the appropriate length,you could use a couple of washers to keep the length all the same. You only use the chuck to hold the screw don't run drill.

R
 
Rascal said:
What is the drill size for .146 x 48 ?
Click to expand...

Tap drill is equal to Nominal Diameter minus the Pitch.

The Outside Diameter of Numbered screws is determined by the formula:

.060" + (# x .013") = OD of bolt

Therefore a #6 is:

.060" + (6 x .013") = .138"

One pitch is equal to One divided by the number of threads per inch

1/TPI = Pitch

In this case:

1/48 = .0208"

Therefore, if OD - Pitch = Tap Drill size:

.138 - .0208 = .1172"

As such a 3.00mm or #32 drill will work fine (.1181" & .1160", respectively).
 
Rascal said:
Thanks, I bought a Winchester 94 and found one rear mount hole stripped.

I bought a dozen oversize 6-48 screws ... They are .146 x 48 and I bought the taps as well.

Cost me $80 but it will fix the gun right.

I plan on doing all four holes.

Apparently the taps will rethread the holes with no drilling, I bought the taper and bottom tap and screws from brownells

http://www.brownells.com/optics-mou...er-146-48-screws-sku080-719-112-795-3103.aspx
Click to expand...

I would suggest only doing the hole that requires it... why alter them all to max size? Screws it up if you strip one of them...
 
Blastattack said:
Tap drill is equal to Nominal Diameter minus the Pitch.

The Outside Diameter of Numbered screws is determined by the formula:

.060" + (# x .013") = OD of bolt

Therefore a #6 is:

.060" + (6 x .013") = .138"

One pitch is equal to One divided by the number of threads per inch

1/TPI = Pitch

In this case:

1/48 = .0208"

Therefore, if OD - Pitch = Tap Drill size:

.138 - .0208 = .1172"

As such a 3.00mm or #32 drill will work fine (.1181" & .1160", respectively).
Click to expand...

The replacement screws are not a number screw , instead if #6 they have a listed size of .146, slightly over a #6 but I don't know if its oversize enough to the point where the .1172 drill would be too small , I don't have the starter tap just taper and bottom
 
Rascal said:
The replacement screws are not a number screw , instead if #6 they have a listed size of .146, slightly over a #6 but I don't know if its oversize enough to the point where the .1172 drill would be too small , I don't have the starter tap just taper and bottom
Click to expand...

I gotcha. Same theory applies. .146 - 1/48 and you have your tap drill size. Taper tap is the starter. Taper, Plug and Bottoming are the only three tap styles I know of.
 
Just fixing the one hole as guntech suggested makes sense. Once they are loctited in place the fact that one screw is different is not really a concern and as long as you inform future owners no big deal.
 
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