View Full Version : Drilling and Tapping for the first time - help!

February 23, 2012, 11:27 PM
I am planning on drilling and tapping an sks reciever. This is the first time I will be attempting this can anyone with more experience give me some pointers?

February 23, 2012, 11:29 PM

February 24, 2012, 12:26 AM
Don't screw up:p...Layout of the holes is key and drill some pilot holes if you can.

February 24, 2012, 04:06 AM
Receiver or the top cover? they are pretty cheep to replace as in get one to drill and go from there.

February 24, 2012, 08:41 AM
If it is a top cover,getting a replacement to drill is a good plan.

What do you have for equiptment?

I suppose some good advise might be "Don't do your first drill and tap job on a firearm receiver" Get some 1/2 by 3/16 or so steel and drill and tap hole patterns in it to match your base.Don't drill the gun till you are good at it.Maybe you can even experience your first snapped tap in scrap steel.
Look at Enco or MSC's web page.One of them has a spring loaded tap center.
Or,some tap handles have a slip dowel out the top.Either goes in the drill chuck to guide the tap square and straight while allowing it to feed in.

Begin with a small center drill,follow with your tap drill,then tap,all on the same location unless you have a good milling machine to accurately reposition your work.
Use a good tapping fluid like Tap Magic for drilling and tapping.

If this is a through hole,use a 2 flute spiral point gun tap.If it is a blind hole,use a 4 flute plug tap followed by a bottom tap.Blind holes take great care with the chips.About every 1/2 turn,back up 1/4 turn to break the chip.Stop,back the tap out,blow the chips clear if you feel anything!

Follow that with the bottom tap.t is very easy to break a bottom tap.Take a little at a time,clear the chips,and feel carefully for any increase in torque.Do not jam it into the bottom of the hole

I hope you have some means to precisely locate your holes.A drill fixture,an x-y vise,a mill,something,and at least a quality drill press.

Good luck

February 24, 2012, 12:05 PM
I did this SKS drill and tap ~ 15 years ago.

I did not have a mill at the time, but I did have a drill press.

February 24, 2012, 12:19 PM
That is exactly what I want to do. Any advice?

February 24, 2012, 01:58 PM
If it’s a plate, scope mount or something similar you want to mouth, if you can, clamp whatever it is where you want it mounted and use it as a template / guide for drilling. Small taps are very easy to brake. Go slow, make sure your tap is true vertically and horizontally, use oil and make sure you turn the tap ¼ turn counterclockwise ever time you make a clockwise revelation.

February 24, 2012, 03:55 PM
They said at ELDEC in 1982 that if more than two engineers were talking, they were talking about heat pumps.
They said at PED in 1985 that if more than two engineers were talking, they were talking about satellite dishes.
They said at Boeing tooling in 1995 that if more than two metal workers were talking, it was because the holes did not line up.

In 2007 I ran a team that designed, built, and wrote the software for a dynamic EMI load with radio frequency measurements everywhere. It was huge with sealed metal walls everywhere and heavy parts.
I am not usually in charge of anything. I am over priced smart Alec.
There was a technician that was drilling holes and they all lined up.
I took him out in the parking lot and gave him an unopened box from Century with a 1903 Turkish Mauser in it.

What does it all mean?
Getting the holes to line up is a big deal.
The drill for tapping is smaller than the hole for the screw clearance. The scope mount is then not self fixturing.

February 24, 2012, 06:55 PM
Center punch where ever you need the holes. Use a center drill to start with if you have one avaliable. Get the right sized drill you need to tap the hole. They have taping charts all over the web for the right sized drill to use. Make sure to use liberal amounts of taping oil, this will save you alot of headache. You can use a hand drill if you are carefull but the part has to be secure and the drill needs to be straight up n down. A drill press or mill is prefered. If the tap starts to bind then back it out a little. It can also bind while backing the tap out so be carfull of this also. I am not sure how deep you are taping but if it is not very think material, then it should be pretty easy

February 24, 2012, 08:40 PM
Well Mr. Clark I’m glad you’re.. “ not usually in charge of anything.” And that your just an “over priced smart Alec.” because If you have never heard of or don’t know how to use the item you wish to mount as a temple it’s a good thing you’re “not usually in charge of anything.” And are only an “over priced smart Alec.”

Square the item to be mounted where it is to be mounted and clamp. Use as a “guide”... bit same size as hole to make a divot center of hole. THEN use the correct size bit for thread size using the temple/bracket to make sure you have the same clearance ALL THE WAY ROUND the bit as you drill. See! Use the mount/bracket as a template/guide. I can’t believe I actually had to explain that. :rolleyes:

February 25, 2012, 01:16 AM


This is a "Transfer Punch Set" on sale for $8.

"For accurate transferring of drilled or tapped hole
All punches .0025" undersized for easy use
Heat treated
Punch Sets; Punch Set Type: Transfer; Punch Set Style: Standard; Punch Size Range (Inch): 3/32 - 17/32; Number of Pieces: 28;

I use these all the time.
I make my own scope mounts from scratch, modify commercial ones, or use off the shelf. I am really hung up on getting the holes to line up and getting the scope bore parallel with the bolt bore parallel with the barrel bore.
Here is a video on my Mosin Nagant scope mounts

February 25, 2012, 06:04 AM
Pawn shops used to have a lot of really butchered otherwise nice rifles from the old side mounts,like the Weaver "N" mount.Crooked holes,sometimes some extras,maybe even brass 1/4-20stove bolts.

Yup,I can tell some folks out there still know how to do a real nice job.

February 25, 2012, 01:17 PM
Clark, nice set and I'd love to have one if I needed it. I’ll tell you why I don’t have one and why I don’t tell people to buy tools. I’m a tooalholic! I have three roll around tool boxes and two walls of my shop/garage filled with tools. Can you say $$$$$. I have so many that I’ve only used once that I can’t count. I’m now at the age that if I can do a “good” job with what I have on hand I won’t buy something I’ll only use once. It’s hard to resist the urge. I can’t remember the last time I had to drill and tap a pattern of holes or even one that had to be precise. Now I had to tap a hole a few weeks ago. It’s been several years since I had to use my tap and die set. However that’s something you can’t work around when it’s needed.

I really want a lathe but can’t justify the cost for the amount of use I’d get out of it. However every time I want to make something I start looking really hard at them.

You’re right and I advise if the OP can afford it to buy it. :)

Edited to add: I read the review of the set and here’s one problem with buying cheep tools.

These punches seem to not be heat treated very well, most of the ones I have used, the tips have flattened punching soft steels.The steel itself seems OK. I turned new tips on the flattened punches and heat treated them and they seem to retain their point much better.but if you dont want to mess with them, you might be better off getting a better set.

February 25, 2012, 02:09 PM
I once had a fantastic machinist, always asking what precision we needed on our parts. If you told him, 5/1000 you could be sure your pattern was perfect. If he got the initial positioning right that is, for some reason that one eluded him from time to time. But not to worry, if the first hole was off 0.5", all the others were withing 0.5005 and lined up perfectly...

February 25, 2012, 05:12 PM
Transfer punch sets are great in their place.I think they have limited use for gunsmithing.One issue would be they are typically fractional.Tap drill sizes for sights would typically be of a number drill size.

I would use a trasfer punch to make a very light layout mark.I do not use them as a center punch.

I realize old school machinists and gunsmiths did use layouts,center punch marks,and drill presses.They created a lot of problems that way,too.

The web,or chisel center point of a twist drill has,for practical purposes,no cutter speed and little cutting edge.It is a problem that causes a drill to wander.Add to that a twist drill is flexible.

I recomend against using a center punch mark.

Get a good,small center drill,a number 1 or 2.Look for a 3/16 body dia.

Now,if your chuck wobbles,dont use a center drill,you will break it.Go with a spotter drill.To see/buy these,go to MSC or Enco.Browse around.

These stubby drills will make a real nice start for your tap drill.The web of the tap drill touches nothing till the body of the drill is guided by the hole.Use a center drill and drill right,and your hole will not wander .001.A center punch mark will not be perfectly under the center of the spindle.It will deflect the drill,and the hole will be out of square.

You do need a vise,and the vise need to be clamped down.It will take patience to get the hole lined up and clamp down the vise.Use a little dead blow hammer to slap it around a bit.

Actually,if you use a pin or dowel a bit smaller than your base holes,your eye can center pretty close.Look from different angles.I use a Browne and Sharpe .0005 test indicator to spin in the hole till the needle does not move.Then I know I am centered.I do not do trailer hitch grade gunwork.

At this point,I'd do one end screw with your base clamped in place some how.I have even used superglue.That is not a recomendation,just gitterdun.

Center up on the hole however you will.Now,without moving anything,center drill,tap drill,lightly chamfer,then tap your hole,all on one location.

Then clean up and deburr.Now,use that one screw hole to attach your base.Your screw should center on the hole.Now,you know that one lines up.

Carefully position and clamp the other end,and drill and tap the other end hole

Then put another screw in,and finish.

Or,you could take a piece of steel stock,practice transfering the holes to that steel stock and tap drillng your practice piece.Do it till you get 4 precise holes that line up.Clamp that to your reciever and use it for a drill fixture.It will guide your drill just fine.