Continuing front post problems.

[Brass Rat]

My new post arrived today and I tried it in the block. It goes in about 3 threads and then gets very tight and I am afraid it will get stuck like the original.

There are no scuff marks on the outside of the plate so it is apparently a problem with the threaded hole in the gas block and I probably need to chase the threads with a tap.

Can anyone tell me what size and pitch the sight post bolt is?

[Brass Rat]

Thanks, I'll go by Ace and pick one up in the morning.

[W.E.G.]

Sometimes the outer radius of the disc portion (the part that has to dunk down into the recess in the sight block) is too tight. It has nothing to do with the threads.

I had to chuck a couple of mine in the drill and spin that outer edge against a file (poor man's lathe) to get the sight to drop smoothly into the sight block.

You can check yours by removing the front sight, the fixing plate, and the spring. Then flip the sight 180 degrees, and try to stick it post-first into the recess. If the disc hangs up on the block before it bottoms out, your disc is to fat for your block. Commence to WECSOG'n.

Pad the threads with electric tape, and clamp the threads in the drill chuck.

[Brass Rat]

Thanks, I didn't think of turning it upside down.

I just tried it and it drops right to the bottom and spins freely. Also, when I thread it down as far as it will go there are no scuff marks on the outer edge.

Is it possible that this is not a regular metric gas block?

How can I tell?

[Shootability]

Are the ears open or closed?

[Brass Rat]

Closed.

[gunnut1]

Rat try this.Thread pitch discussion (http://www.falfiles.com/forums/showthread.php?s=&threadid=97730)

Search works great. this is also a sticky in this forum.

[Brass Rat]

There doesn't seem to be a #12x28 tap in town.

[NoNotAgain]

Originally posted by Brass Rat
There doesn't seem to be a #12x28 tap in town.

Machine tool dealer only.

Order a bottom tap as the threads are already in the gas block and a starter tap has too much taper to be able to be fully inserted into the gas block.

www.mscdirect.com

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1995774&PMT4NO=8275387

www.use-enco.com

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=510-1038&PMPXNO=8910345

[W.E.G.]

I'll bet if you just put some JB Bore paste on the threads of the sight, and work it a bit, you can save yourself the inconvenience and expense of a use-it-one-time-in-your life tool purchase.

[Brass Rat]

I've got one coming from here (http://www.mcmaster.com/) for 7.50 shipped.

[Brass Rat]

Well W.E.G. you called it, the threads were crudded up but it is also hitting the inside of the recess with the outer edge of the disk. I put it under a magnifying glass (it's a bitch getting old!) and I could see where it is rubbing.

I took .035" off of it before the battery in my drill gave out and it was just too late to wait for it to charge last night.

It goes down further now but it looks like I will need to take another .020 or so off.


By the way, the company I ordered the tap from is great, they have a counter over on Fulton Industrial about 15 miles from me. I ordered it over the weekend figuring I'd have it in the mail by Wed but about 1815 yesterday a small pickup truck pulled in the driveway and then handed me a box containing 1 tap.