SKS Side Rail Question

PECHENEG

PECHENEG

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Hi guys,
I just bought an original SKS Side rail mount, made in Russia. Pretty much same in dimensions as Choate or Promag one.
I ordered it from BC, from ebay. But on my Qs what drill size and tap size to use.. there was no reasonable answer back, neither it was shipped w/ instructions in that regard. All they said is that the screw is 8 - 40.


When I check this site: http://westrifle.com/wrstore/index.php?main_page=product_info&products_id=1524.com, WestRifle , this guys have drill/ tap size indicated and they provide 8 - 32 screws, more standard ones for taping. 8 - 32 drill bit+tap is standard, why the hack 8 - 40? The difference is 2.5 threads less per whole/screw x 4 screws 10threads less. I think it will still hold well.

So I decided to go w/ 8 - 32, 12.9 grade Steel Screws, but when I check the specs for the tap drill size: http://www.shender4.com/thread_chart.htm, SHENDER

They provide 75% thread+ tap drill size for plastic only and 50% thread for steel.
So... the Q is, what tap drill size for 8 - 32 to get 75% thread in steel?
29 or 27?

Tap size, I imagine, will be 8 - 32, included in standard taping box from Princess Auto, or CanTire , for example

Sorry for stupid Qs
And THANKS
 
No, I ordered from alex-Something on ebay, and then I was looking for the whole size to drill and the tap to use and since that ebay account was totally useless in providing simple info I looked further and found WestRifle recommendations: for 8-32 x 3/8 screws the say: 8-32: drill (1/8', I guess this is 27 bit), tap 8-32.

WestRifle which sells same product uses 8-32 scres, and this is what they say: "Soker 8-32X3/8"(4 pcs included), Drill - 1/8'HSS, Tap - 8-32 TAPPCR"
 
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Mine came with 8-40 also and I tapped it to 8-32x3/8". You won't be disappointed with a receiver scope mount, I love mine and it holds zero 100%. A few things I would suggest is making sure it is level to the barrel, just high enough to remove the cover for cleaning and that it is set back far enough to insert stripper clips. I drilled and tapped 1 hole at the back, mounted it and then checked everything was good. I think I had to move mine back 1/4" from the measurement given in the instructions for stripper clips to work. For leveling to the barrel I had a 1" piece of pipe 3 feet long that I mounted, with rings on the mount, that stuck out over the barrel. I then used inside calipers, between the pipe and the barrel, to make sure the mount was leveled with the barrel. After that I bore sighted the the scope to varify all was good and then marked a tapped the remaining screws.
 
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FreedomIsn'tFree said:
Mine came with 8-40 also and I tapped it to 8-32x3/8". You won't be disappointed with a receiver scope mount, I love mine and it holds zero 100%. A few things I would suggest is making sure it is level to the barrel, just high enough to remove the cover for cleaning and that it is set back far enough to insert stripper clips. I drilled and tapped 1 hole at the back, mounted it and then checked everything was good before I marked and tapped the remaining screws.
Click to expand...
This is exactly, what I thought and it's cool other people think this way!
So you used drill 27 or 29 to make a whole?
And, of course you used 8-32 Tap as it is pretty str8 frwd and logical :)?
I usually do not work w/ metal of that degree of precision :)
Forgive me my amateur-ism
 
FreedomIsn'tFree said:
Make sure you use blue threadlocker on the screws before installing them.
Click to expand...

Why Blue? I would red for sure. This isn't something you want to be taking apart at a later date, you want it to be as secure as possible. Although I'd probably skip on going all the way to green locktite, because that #### will only ever come out if you are lucky. Red, you just need to add some heat to it.
 
Suther said:
Why Blue? I would red for sure. This isn't something you want to be taking apart at a later date, you want it to be as secure as possible. Although I'd probably skip on going all the way to green locktite, because that #### will only ever come out if you are lucky. Red, you just need to add some heat to it.
Click to expand...

The blue seems to work well, but the red could be used if a person wanted.
 
Also one more...
Well I have a synthetic stock and the mount is just at the level of the lower side of the triangle wholes... when you align it with the gun body (cover out) , no cuts required to the stock.

But somewhere I read that the mount has to be 1/16'' or 1 mm lower i.e. the lower side of the CUT triangle wholes should overlap with the gun body (when the back cover is out) for 1/16'' or roughly 1mm.
It means that I have to precisely trim my stock for 1-2 mm down.... which I was thinking not a big deal... but I'd prefer to keep the plastic relatively intact and those 1-2-3 mm 1/16 or 3/16'' the rail elevation up or down... does it really play a big role? Anyways, there is enough "meat" I mean metal to screw in, no matter how you align the MOUNT's CUT WHOLES TRIANGLE lower side-even with the body of the gun or just 1/16'' down. kind of difficult to explain.
Am I right?

I am referring to this:
http://www.milsurps.com/showthread.php?t=19207
 
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