Question on drilling and tapping stainless

[fecmech]

I've D&T'd my Ruger GP and SBH for the Weigand scope mounts with no trouble at all and they are both blued guns. A friend with a Stainless Ruger SBH would like me to D&T his gun for the same mount. Are any different procedures required to D&T the stainless gun over the blued one??

[Jim Flinchbaugh]

New or very sharp tap, highly polished version not the sand blasted looking carp ones from the hardware store. Tap Magic, go slow and back up often!

[fecmech]

Jim--taps and drill bits were purchased from Brownells (6-48 tap) a while back and only used on 3 guns to date. Anything different i.e. drill speed etc. ?

[W.R.Buchanan]

Just run it the same as regular steel. You do need the tapping fluid though, as it breaks the surface tension of the metal and makes it so it is harder to stick the tap. Stainless is a little more gummy than regular steel.

I do this stuff by hand on the mill with a small center stuck in the hole in the top of the tap handle, and directly after I drill the hole . That way you are insured of getting the tap perfectly in line with the hole.

The vast majority of broken taps are as a result of not being properly lined up with the hole, or essentially going in sideways. The load on the tap is un-equal from side to side which causes the tap to break.

Good luck.

Randy

[fecmech]

Thanks to all for the info. I'll see if I can get some Tap Magic in town, I just used WD40 when I did my Rugers. I did something similar on my drill press, took out the drill, chucked the tap and turned the drill chuck by hand with the drive belt.

[gzig5]

I use Castrol Moly-Dee when tapping stainless and feel it gives a significant advantage over tap-magic or the others. I don't get that gummy-grabby feeling when drilling and tapping. Good idea using the chuck to keep the tap aligned, but you might loose some sensitivity. Large taps have a 60 degree cone in the back end to accept a center to aid alignment. Small taps may not have this, but most of the T-shaped tap holders have it in the back end. Use a center, ground rod or what have you that has a 60 degree point, in chuck to keep everything aligned. A little lube on the center keeps everything turning smooth. This gives you the best sensitivity so you know when to stop and back out. Never broke a tap using these methods. Freehand is another story.

[MtGun44]

Do not let the drill turn without cutting. In a drill press use low RPMs and high feed
pressure. If the drill slides it will deform the SS locally, which work hardens it. If this
happens with some SS alloys, they become so hard as to be nearly impossible to
drill. Slow RPMs, sharp tools, good lube.

Bill

[theperfessor]

MtGun44 nailed it. Don't let the drill just press on the surface, use enough positive pressure to keep cutting. Trying to drill through a piece of work hardened SS is no fun and a recipe for disaster.

[fecmech]

Gentlemen--Again thank you for the replies. Purchased some Tap Magic today and when my friend gets the gun I'll give it a go.

[Norbrat]

Re-grinding the drill point from 118° to 130° - 135° should help a bit too.

[targetfreak]

If you have taps which are already used, throw them away and buy new ones; ideally one for each threaded hole. They are cheap compared to removing a broken tap. I did this for more than ten years on stainless surgical equipment. Use twice as much TapMagic as you think would be prudent. Back up after every one-half turn. Tap each hole with the same setup immediately (without changing the setup) after drilling. Use a tap-follower (if you don't know what it is, stop right now). Only titanium is more difficult to machine than stainless.
You have my sincere hopes for good results. The gun is worth much more than the work which will be applied to it. Be prudent and extra careful, and good luck.

[perazzi]

also, if drilling on a cylinder, make sure you get a good center or spot drill starting. For the tap in the drill/mill, I use a 1/8 ball between the chuck and the tap handle. works the same as a 60* center. Always maintain pressure while tapping, small taps need to be back out often and cleaned.

get cobalt stub length drills, already 135* tip.

[nanuk]

perazzi: by 1/8 ball, I assume you are saying a 0.125" diameter hardened ball bearing?

[perazzi]

perazzi: by 1/8 ball, I assume you are saying a 0.125" diameter hardened ball bearing?

I'm sorry, I work for a precision (.000003) ball manufacturer. Yes, I should have been more specific.

Actually, I use tooling balls mounted on stems that I just clamp in the collet of the mill.



of course, I also have these...

[Lee]

Thems some big balls!!!

[Flinchrock]

Do not let the drill turn without cutting. In a drill press use low RPMs and high feed
pressure. If the drill slides it will deform the SS locally, which work hardens it. If this
happens with some SS alloys, they become so hard as to be nearly impossible to
drill. Slow RPMs, sharp tools, good lube.

Bill

Good advice!
Also,,for the lube I recommend either Anchorlube or the Moly Dee. I also like to ream the holes to size when I am working with stainless, especially if the holes are deep. Drilled holes are not normally round, more like tri-lobed, if a deep hole it makes the tap bind up the deeper you go...

Good luck

[fecmech]

Well my friend finally got his Ruger stainless .44 magnum and brought it over today. I had done a practice run on some 3/8" thick 8" stainless pipe scrap, drilling and tapping 4 holes with no problems. Stainless is definitely a different animal being really "gummy" and tough. On the pipe I would not have been able to do it without the tap magic. I tried that with just WD40 on the last hole and the tap would have broken so I backed it up and finished with the tap magic.
The Ruger was actually a piece of cake. The top strap was only about 1/4" thick and a less tough stainless than the pipe I practiced on. I never felt like I was straining the tap at all and the job came out perfect. Again thanks to all for your help.

[MtGun44]

Pipe was probably 300 series SS, the worst for work hardening problems. Check with
a magnet, 300 series (usually 304) is not magnetic, and not heat treatable.

Pistol is probably 400 series SS, much more like carbon steel in general behavior, and is
magnetic and heat treatable. Still can work harden, but not as dramatic as 304 SS.

Bill

[dragonrider]

As said above get new quality high speed steel taps. Also from Brownells get a 3 flute carbide drill of the right size and you will have no problems drilling. Don't know what moly dee is but I have always used Tap Magic with good success.

[dwdw]

Hi All:
Tap Magic is good but I prefer Rapid-Tap its thinner and sticks to the tap better. Brakes the surface tension of the metal and the 135 degree cobalt is a winner if you don't have a carbide drill. Feed slow but with nice even pressure not letting the drill slide and not cut, that will keep the stainless from work hardening thats real bad!
Tapping use only HSS spiral point taps and a 4 flute for bottoming and plenty of cut fluid.
There is two different gold colored drills and taps Titanium Nitride there is the home version very poor and the professional version, the prices are dollars apart.
Just my 2 Cents
Thanks
dwdw