TF99 Total Rebuild Project

[mcmi]

Ok, Mod, if I'm posting this in the wrong category, please put it where it goes.

This thread is going to detail an entire TF99 rebuild. My goal is to have it done by Christmas 2008. I picked this gun up at Airgun Depot for 200 and change. It was a combo with a pretty nice scope. The mounts were crap. I threw them away 25 minutes after mounting the scope and shooting. I'll fix that later. For now, I want to make this gun right.

To start, I like this gun. It feels great in my hands and despite the shoddy interior, it actually shoots pretty accurately. That said, it isn't fun to shoot. Cocking it feels as fun as fingernails on a chalk board. Pulling the trigger is kind of like walking in mud, atop gravel with someone throwing grapes at the back of your head while calling you Nancy, or something similar. Basically, this gun sucks to shoot.

I'ma make it better.

Today I started with the easiest problem; the front sight. It's ugly and it stands up high enough to make an ugly shadow in the scope while sighting. Unfortunately it is not "removable" without a few sharp tools.

This afternoon I lopped off the ugly hoop with a band saw and prepped if for a quick weld. It's made of cast aluminum so it was quite easy to work. 25 seconds on the band saw and about 5 minutes on a belt sander with 400 grit. The hole where the roll pin secured it to a notch in the barrel end forces me to add aluminum before I can go further. I'll have one of my guys take care of this in the morning and I'll finish it and paint it flat black tomorrow afternoon. That'll knock step one off the list.

Then we'll work on a new piston.

[dave2288]

well, i am VERY interested to see how this turns out.  keep us posted!(for anyone that might know...is this just an underlever of the 89?)

[Crzyfrlss1]

I'm very interested too in seeing how this turns out as well.

I almost bought one of these as my first air rifle, I'm glad I didn't.

But, I'd like to see what could become of one with some work done to it.

[shadow]

Nice start on the upgrade of your shooter we'll be following along to check out your progress on her, nice work. Ed

[mcmi]

Quick update:

I had one of the guys fill the hole with weld this morning. It was a tough one. Aluminum is a bear to weld if there is any contamination on it. You have to clean it spotless before welding or you'll get pits and a poor weld. Cast aluminum (especially from China) tends to be full of contamination from within the actual material used to cast. That makes it especially tough to weld. Anyway, he did the best he could and filled the void with metal.

There was a bit of an overfill that had to be cleaned out of the bore of the part, but that was pretty easy with a reamer on the mill.

I sanded the weld off to get everything flat again and filled the small voids with body filler. Two coats of semi flat Krylon later, I left it to dry.

I put it back on the rifle a few minutes ago and took a couple of photos. I think it looks a lot better.

I'll tear this whole thing down tomorrow and start dimensioning the piston so I can draw up a print for that project.

[shadow]

Looking great Kev, were following along. Ed

[Crzyfrlss1]

I'm certainly following along too.

And wondering what kind of shop you're working in and what you do there.

But I want to know more about how this gun turns out.

[mcmi]

I'm probably boring you fellas to tears but I'm having fun with this. The fellas at work are all pretty stoked about participating as well.They're donating breaks to the build and I appreciate that. As much as I love to design and create, I'm not much of a metal worker. The guys at the shop are irreplaceable in that regard. The 'Library' here is also pretty amazing. By the time this project is finished, I'll owe a lot of thanks to a lot of talented people.

[mcmi]

Thanks Ed, I've been impressed with your work and I appreciate the positive feedback.

Crzy, I work for a large foam manufacturer. I design and help build the equipment that we use to convert extruded profiles into hundreds of different products. It's a fun job and I work with a pretty cool bunch of guys. Thanks for following along.

[Crzyfrlss1]

It sure sounds like you like to be where you're working, using all the things that you use helps too.
And you got good people to work with too, work is no fun when you can't enjoy being around your co-workers.

I use alot of tools myself...mostly of the Snap-On and Matco brand, and enjoy making money with em'.

Thanks for sharing this project with us...don't stop now.

[shadow]

Just a "Jack of all trades and Master of none" Buddy hehehe. The joy of airgunning is that I still learn something new everyday and I enjoy working on em almost as much as I do hunting with em, almost hehe. Ed

[gunsup0331]

im not bored!! Keep up the good work! tell your coworkers we said thanks!

[mcmi]

Ok, tonight I took the TF99 down to take an inventory of what parts need to be rebuilt.

I have decided that the compression chamber will not need to be replaced but I'm going to give it a serious polish job, inside and out.

The first joint on the cocking lever is flimsy. I'm going to have to tighten that up. It has some side to side sloppiness that I might be able to fix with some shim stock or perhaps a larger pin can be bored and installed with a tighter hole. The second joint is fine.

The receiver is is pretty good shape. I'll pretty much leave it as is.

The worst parts are the sear, safety and trigger. I'm rebuilding all three of these. The sear is 3 - .08" slivers of garbage steel that have been riveted together. It's pretty shoddy. I'll build a replacement out of some .25" cold rolled steel. The three individual stamped pieces of steel in the current sear are all mismatched and misaligned. Replacing this alone will be a huge improvement in the way this gun feels while shooting.

The safety is just as shoddy. It's triangle shaped on the finger end and it wiggles side to side in the gun. I want to replace this with a softer shape and shim the new one into the gun to make it feel solid.

The trigger itself is just a piece of stamped and formed .04" sheet stock with a cast steel insert at the top to contact the sear. It's junk and it really takes away from the feel of the gun. The trigger alone makes this gun feel cheap and shoddy. I'm going to cut one out of cold rolled steel and replace it altogether.

The piston is a stamped piece of hot rolled .08" sheet that has been roll formed and pressed into a cylinder with a tapered end. The seal is leather with a nylon compression bushing to hold it on. I imagine that this is like most of these Chinese guns would use.I wouldn't be surprised if this piston fits 20 other guns. The choice of hot rolled sheet is more for the manufacturing ease of forming than it is for the purpose of it's use in a rifle. I plan to replace this with a turned piston of the same shape but made with a harder steel. It will wear better and back and forth more consistently. This should make the gun fire more consistently and that should help accuracy.

The last thing I want to replace is the spring guide/end cap. It's plastic now and I'm going to turn one out of hot rolled steel. I'll cover the guide rod with teflon shrink tubing to keep from having the spring rubbing on a steel guide and causing wear. That should be the easiest of the parts to replace.

[dave2288]

can't wait to see how it turns out!  when do you think it'll be done?

[RCnMo]

You mentioned cold rolled steel for the sear. Not to sound like a party pooper, but unless you plan on case hardening it, you may want to try some oil hardening or air hardening steel for that part. CRS won't hold up for more than probably 20 shots. If you take an old file and grind your part out of that, it would make an excellent sear. A file can be annealed so you you can shape your part, then you can re harden and temper that piece. If not, you can silver solder a hardened 'sear' to your sear arm and it should hold up forever. I don't have exact specs on hand, but, silver soldering will withstand several thousand psi before it breaks. Just my 2cents. Keep us posted on the progress. It's nice to see someone turn a piece of coal into a diamond.