How to make a tap, to make a tool, to fix a Sheridan

[SeanMP]

I had an interesting project come my way to repair a Sheridan. It became such an epic that this thread could be called "The winding road that never ends"

Quandry #1....What the H$!! is it? No model numbers no serial numbers. "Sheridan Products, Racine Wisconsin" But based on the rocker safety and the lack of any markings or serial number it was made somewhere between 1963 and 1970...Even no information can be useful at times.

But that means it's one of the infamous Sheridans with the soldered in valve, lead seals and a whole heap of misery. I've heard about these but I've never had to deal with one.

Quandry #2 How the H$!! do you get it apart?

Well it turns out that you need a double ended tool to first undo an internal cap nut then the other end of the tool screws on a 9/32"- 32tpi thread to use as a puller bar to jerk the valve core free of the two lead seals holding it in.

Well first thing you find out that all the original sellers of this beastie have disappeared.....except of course for Pyramid Air....So unobtainium. Second thing you find out is that because of the 9/32-32 threads no one has actually made this tool as it is supposed to be and published the information. So the purpose of this thread is to get that information published.

Seriously Sheridan 9/32" 32tpi....Was it really necessary to invent your own thread

[SeanMP]

The project starts with a piece 3/8" round bar at least 6" long. I used a 1/2 bar 12" long and turned the ends to 3/8. This way I could put a single hole in the center of the bar.

The square drive to remove the cap nut is relatively simple and has been publish here and there with varying degrees of accuracy.

Square drive end
Starting from 3/8 round stock mill or file a square that measures .350 across the faces. The corners will be left round at this point and they need to remain round.
Drill a 9/32" (.281) hole into the end of the bar that is 3/4" deep.
The wall thickness is only .034" so use alloy bar and harden the working area

[SeanMP]

It's not the software. The same thing has been happening to my emails when I insert a lot of pics

[AirGunEric]

What a wonderful learning experience!

I know, I'll shaddup now.

[SeanMP]

Haha...I don't necessarily blame you for this but there is association.

[SeanMP]

Sorry about the delay I get this thread moving along again. Obviously a 9/32" -32 tap is not a readily available size and you need one to make this tool. Either that or your a threading genius that can single point internal threads in a 1/4" hole.

Next thing was to do the thread calculations for a 9/32-32 tap
For anyone interested here they are
Major dia 0.281"
Minor dia 0.246"
Basic height 0.019"
Tap drill (75%) 0.250"
Compound infeed (29.5*)0.023"

With the calculations finished all that's required is to turn down a piece of tool steel to the major dia (plus .001-.002) The plus is for deflection of the work during tapping.
Put a 5 to 7* lead in angle. Just like a taper tap
Then thread it per the calculations

Tool steel always threads best when you are running as close to the rated SFM as possible. Ie the thread chase is whipping around like a ferrari....but you get a nice thread.

[SeanMP]

So finally getting back to fixing up the missing post and closing off

The next step to making a shop made tap is to mill or grind the cutting edges. This is actually not as racey as it looks. I'm sure you could make a usable cutting edge on a bench grinder. The farther past the centerline the more aggressive the cutter will be.
IMG_0372.jpg

Then the tap needs to be hardened and tempered the usual way
I protect the fine threads with this borax and clay mixture
IMG_0374.jpg

And here is the finished tap in action
IMG_0376.jpgIMG_0375.jpg

As seen in the picture the opposite end of the tool is turned down to 3/8" (not required but looks good) and then a .250-.255 hole is drilled .750 deep for the minor tap diameter. The tap in the picture is not ground very aggressively and as such needed to have the chips cleaned off every couple of turns

[AirGunEric]

I think I'm getting the idea why Sheridan went out of business/got bought out 20 years ago...

[SeanMP]

I think I'm getting the idea why Sheridan went out of business/got bought out 20 years ago...

Haha...That's funny I was thing exactly the same thing...." No wonder you stupid a$$es got sold"

[SeanMP]

So as previously mentioned parts for this thing are basically unobtainable here. However all the parts are replaceable with modern alternatives with the exception of the check valve. This is a simple flat disc cup 0.405 OD x .110" thick. The original is made of brass with a (delrin?) insert. It can be replaced by a simple piece of delrin of the same dimensions. I choose to remake the piece as it was originally because this is a customers rifle.
IMG_0383.jpgIMG_0381.jpg

The valve poppet can be replaced by a disco poppet. I had one but unfortunately the old seat was so cockeyed that it ruined the my only disco poppet so I had to make one. I do this by drilling an undersize hole in the delrin then spinning the stem at warp speed while pushing the delrin head on. This fuses the two pieces together then you machine the face and dress down the head to the right shape
IMG_0386.jpg

The lead seals can be replaced by (2) 015 orings. The first oring fits onto the valve as seen in the last pic. The second oring gets squashed between the cap nut and the valve core. Lots of threads out there say this seal is unnecessary but if it's not there the transfer port will leak.
Oring on cap nut.jpg

From this point the only difficulty is getting the little tab on the valve core lined up with the slot in the body that's soldered into the tube while simultaneously compressing the valve core spring and screwing in the cap nut...tricky but it works with the tool.