View Full Version : IMBEL inch receiver missing gas nut threads

April 10, 2002, 20:43
One of the MDFCA members is now the unhappy owner of a CAI-imported inch IMBEL receiver with no threads in the area where the gas tube nut is supposed to screw-in. The hole is there. But, it appears that they simply forgot to cut the threads. The hole is parkerized.

Two questions:

Am I correct that the thread pitch that SHOULD be there is 9/16-24 R.H.?

How common is this size, and how much can I expect to have to pay for a tap?

April 10, 2002, 21:52
Had to re-tap mine due to the fine craftsmen at Century crimping the area. 9/16x24 RH is correct. $18.01 from MSC.

April 10, 2002, 22:00
Any suggestions about tapping technique for tapping a virgin hole? ;)

April 10, 2002, 22:07
Gary, I would suggest first making sure the hole is the correct size then I would set the receiver up vertically on an angle plate on a mill. I would then indicate the hole and use the spindle by hand to tap the hole to make sure that is straight and square. Just my .02

April 10, 2002, 22:11
Gary, can you set the reciever up nice and square in a drill press? A mill would be handier, try and indicate the hole, use a point in the chuck to help keep the tap nice and straight, lots-o-oil also, when tapping, turn tap about a half a turn and back up a little to break the chip, it shouldn't be a problem.

April 10, 2002, 23:51
I know you are chomping at the bit and ready to fire up the Dremel, but why not ship it back for a replacement?

Some of these wacky out of spec features on this "Imbel" R1A1 receiver kinda makes you go...Hmmmmm.

Send it back!


April 11, 2002, 01:24
Gary,.. taps are center drilled on the end opposite the threads. Use a square to make sure that your receiver is pointing perfectly verticle in a drill press vise. You'll need something round with a pointed tip to secure in the drill chuck,.. a center punch should do it. Position the receiver under the chuck and lower the center punch which is in the chuck into the center drilled hole in the back tip of the tap. (you'll need to have the tap handle on the tap before you do this)

The center punch which is chucked up in the drill ,.. the tip of which is inserted into the center drilled hole in the end of the tap ,will hold the tap perfectly verticle while you tap the threads into the receiver. You'll need someone to apply pressure to the tap with the spindle of the drill press while you operate the tap. You're not going to run the drill press,.. you're simply going to use it as a press.

When tapping,.. make about 2 complete revolutions with the tap,.. then back it off about 3/4 or a turn to break the chips,.. be sure to use some dark thread cutting oil on the tap,.. it makes a huge difference.

It all sounds complicated,.. but it isn't,... you're simply inserting a verticle pointed object into the center drilled end of the tap to hold it straight and square to the receiver while you tap it. I could show you in 2 seconds,.. but I have to type a blister on my finger to explain it.

April 11, 2002, 11:08
All this talk about mills and drill presses has me concerned.

I have a very large vise (6 1/2" jaw-opening). And I have a Casey Elliott receiver wrench. I do not have a mill or a drill press.

Is there any reason why I can't just put the receiver in the CE wrench...then, put the CE wrench in the vise...with the hole in a horizontal position...then, run the tap in by hand? Is there really that much hazard in just eyeballing it for straightness? After all, the joint between the tube and the collar isn't exactly a precision press-fit. I should be able to tell if it is getting started caddywampus.

I suppose it could just be sent back. But, sometimes the old WECSOG spirit won't let go.

As for choice of tap, I know some have a tapered tip, and some have a square tip. I assume I have to at least start with the taper type. Will I have to follow with one with a square tip?

April 12, 2002, 00:19
Gosh Gary, I do believe that hole is more precise than you think. If it is not square, will the piston bind in the gas nut??? Kinda makes you go hmmmmm. I've seen some pretty tight fits between the piston and gas nut, why create anymore???????? Just a thought.
Heck, can't you borrow a house with a drill press in it??? ;)

P.S. Tap squareness is in direct relation to the amount of precision you want verses the depth of the thread, the deeper the tap goes, the more crooked it will be regardless of how straight you thought it was

April 12, 2002, 08:12
See, Marvel Mystery Oil. I knew that.
So, go ahead, eyeball it.
Then, when it's AFU, ship it back.

Though I've flogged you and I've flayed you,
by the living Gawd that made you,
you're a braver man than I am,
Gunga Jeter.

Seth Livzz
April 12, 2002, 08:36
Any decent machine shop in your area should be able to tap it for you at minimal expense.

Just an idea...

April 12, 2002, 08:58
Hi Gary
I aslo would recommend the machine shop route on this one.It is too easy to cock the tap a little and not see it.Looking at one of my Imbels;start with tapered tap untill You get a few threads cut fully,then
bottoming tap,Carefully.

[ April 12, 2002: Message edited by: rnajr ]

Viking Warrior
April 12, 2002, 22:06
Dont you guys realise what you are asking Gary to do?? Borrow a house with a drill press? Go to a Machine shop???
PAY someone to do work for him??
You might as well ask him to go to a gas station and ask directions. Shhesh..
"Caddywampus" Coyote hitting his thumb with a nine iron... http://www.stopstart.fsnet.co.uk/mica/cavy.gif

April 13, 2002, 12:21
as most above have mentioned, keeping tap parallel to the bore axis is very important, but not insurmountable, if you don't have a drill press. you need a small square to do this correctly by hand. use a tapered tap and lots of tap oil. start tap in hole with a few turns to get started,then use square to check straightness of tap in 2 places 90 degrees apart, and then adjust tap accordingly (push/pull left/right) turn tap 1/2 to3/4 turn check again with square always check again after turning tap. you can not check to often, if you do this until hole is completely tapped you should be ok. good luck if you should chose to accept this mission :eek:

April 13, 2002, 20:59
Gary, just a word of encouragement - I have hand tapped two recievers (one Imbel and one Hesse) that came minus the gas nut threads and both are functioning fine. The depth of the hole tends to lead and true the tap. Just go slow, use cutting oil and back it up a bit frequently.

April 13, 2002, 21:04
You ran into TWO that were missing threads??? Man, this is starting to sound like an epidemic!

Did you have to use a bottoming tap?

April 14, 2002, 06:18
Hey Gary!

Just a thought...

Isn't that 9/24 RH tap the same as the bbl threads on a L1A1? Sounds like someone could start Dremelling some ersatz FH's up for Commonwealth guns! :D

BTW; Are you coming on the 5th?


April 14, 2002, 06:52

Tap drill for that hole is 33/64" which is just beyond your normal 1/16 to 1/2 drill set. Get one when you order the tap. Not worth trying to tap unless the hole is the right size.

Taps come in 3 styles.

1) Taper (longest taper to first full thread)
2) Plug (a little less - most common)
3) Bottoming (almost no taper - for blind holes)

Just get a taper style tap from MSC. Use Break Free CLP (great alternative to tapping fluids in a pinch). Eyeball square from 2 directions. Turn a couple of turns to get started. Then turn a bit, back out a bit (until you feel the chip break), go a little farther. Pretty soon, you're done.

Man, I am loosing faith. I was hoping to see the Jeter dental pick threading method explained.... :D

[ April 14, 2002: Message edited by: blackbird ]

April 14, 2002, 07:23
While some oils suggested are okay for what you want to do, such as Tap Magic, the rest of the oils suck except for what Temp was saying.
The best oil for tapping this type of material is the dark, black cutting oil, such as used in cutting pipe threads on bkack gas pipe. This oil has a high sulfer concentrate for better lubricity.
I don't know this because I grew up in a machine shop, I know this because I've worked in one, every day, for the last 20+ f*cking years.
Just take it to a machine shop and have them tap it, instead of dealing with the hassles of sending it back. Take another with a tapped hole with you to show them exactly what you want.
It is imperative that you keep the bore of the hole lined up with the tap. If the hole is tapped crooked then the piece that screws into it will be crooked.

April 15, 2002, 00:50
my goodness, no blistering wrath for unexcuseable QC snafu's????? least its an Imbel :)