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Posted: 1/27/2012 7:28:10 PM EDT
Okay you machining guru's, I need your help!  John Thomas has been doing some testing
on a test casting and he found a problem.  We believe that the problem can be overcome,
but we need some creative minds to help us come up with a solution. I don't want to
place blame on anyone who has been involved in this project, I only want solutions.

Here is one of the first dimensional drawings that was developed for this project.



Here is the second dimensional drawing that was used to develope a rapid prototype
model that was used to build the mold.  Please make note of the notes on this picture.



I think that everyone who is not a machinist could not see the problem when looking at
the following picture of the prototype fsb next to a Colt M16A1 fsb.  You have to
measure this one to notice it.



I guess in the excitement of the whole project, we missed this error.  Again, please
don't blame anyone, we just need to find solutions to this problem.  This past week
John Thomas was doing some test machining as you can see in the pictures below.







I know what you're thinking, man those look great and I must say that I agree.  Now back
to the problem.  Notice in this next picture, the measurement of .519 on a standard
front sight block.



In this next photo, notice one of the prototype fsb's with a measurement of .430 which
is quite a bit smaller when we are dealing with such close tolerances.  Remember the
dimension of .437 is .430 in the final product, which is probably due to shrinkage in
the casting process.



Here is a picture of the space needed for the front sight post and detent/spring, which
comes to approx. .367



Now what does this all mean when having to machine the prototype fsb for the front
sight post and detent/spring area.  Here is an analogy and some numbers that John Thomas
came up with.



This next photo kinda helps put things into perspective.



Do you now see what I mean by HELP!!!!  We all have too much time and money in this
project to just ignore this problem.  We all need a solution that will make everyone
happy.  I know someone out there has an idea or the machining expertise and skills
to come up with a solution that we can all be happy with.

Link Posted: 1/27/2012 8:04:57 PM EDT
[#1]
since the FSB can't be modified easily the only parts left to modify would be the front sight post and spring and detent.

maybe the front sight base post can be turned to smaller diamer and have the notches recut.  along the same lines, maybe a smaller spring/detent can be used.  something like the a1 spring and detent for the rear sight.  by reducing the size of both of those things, you should be able to pull the front sight post into a smaller package.
Link Posted: 1/27/2012 8:08:48 PM EDT
[#2]
It seems to me that if there was a little bit of material machined off of the mold, it would result in more metal being left on the raw casting.  This should be correct, since the casting is an "imprint" of the mold.  How hard would that be to do?
Link Posted: 1/27/2012 8:13:01 PM EDT
[#3]
Can we just thread the FSB and leave out the detent.
I mean it is a prototype.
Who is to say that the FSB had a detent during the prototype phase.
That would work for those of us not interested in daily shooters.
Might be able to fabricate a non-detent front sight post.
Link Posted: 1/27/2012 8:26:21 PM EDT
[#4]
Quoted:
It seems to me that if there was a little bit of material machined off of the mold, it would result in more metal being left on the raw casting.  This should be correct, since the casting is an "imprint" of the mold.  How hard would that be to do?


I'm actually going to talk to the foundry on Monday to see about this option.  The order has already been placed for 200 parts, and they were given the go ahead to move forward.  The foundry ran 8 test castings for me to check out before the full 200 were poured, and we found that a new shrinkage point occured after adding the second gate to the mold.  The owner of the foundry assured me that we could fix the shrinkage by adding a third gate to the mold.  If they haven't already started pouring the 200 piece order, maybe I can get my hands on the mold and work it over with a dremel tool.  My only fear is that I'll booger it up and then it will look like crap.  I'll know more when I call on Monday.  If we can do that the problem is solved, I'm just afraid that I might be too late to change the mold.
Link Posted: 1/27/2012 8:29:26 PM EDT
[#5]
Quoted:
Can we just thread the FSB and leave out the detent.
I mean it is a prototype.
Who is to say that the FSB had a detent during the prototype phase.
That would work for those of us not interested in daily shooters.
Might be able to fabricate a non-detent front sight post.


This is one of the solutions that John Thomas suggested.  His thought was to use something like loctite to hold the thing in place.  Does anyone really know if the original prototypes had detents on the front sight post.
Link Posted: 1/27/2012 8:35:45 PM EDT
[#6]
Here’s my suggestion if they cant alter the mold….
Eliminate the plunger and spring.
Replace them with a small set screw that’s about the same diameter of the plunger tip.
It would stick up and engage the notches in the front sight.
The taped hole would only have to be about 1/4 deep.
Adjust the sight at the range, then locktite the set screw in place.
Link Posted: 1/27/2012 8:39:48 PM EDT
[#7]
Quoted:
Here’s my suggestion if they cant alter the mold….
Eliminate the plunger and spring.
Replace them with a small set screw that’s about the same diameter of the plunger tip.
It would stick up and engage the notches in the front sight.
The taped hole would only have to be about 1/4 deep.
Adjust the sight at the range, then locktite the set screw in place.


You just might have something there with that idea.
Link Posted: 1/27/2012 9:28:15 PM EDT
[#8]
Quoted:
Quoted:
Here’s my suggestion if they cant alter the mold….
Eliminate the plunger and spring.
Replace them with a small set screw that’s about the same diameter of the plunger tip.
It would stick up and engage the notches in the front sight.
The taped hole would only have to be about 1/4 deep.
Adjust the sight at the range, then locktite the set screw in place.


You just might have something there with that idea.


 But best option would be to modify the mold, if they haven't already poured.

Link Posted: 1/27/2012 9:41:00 PM EDT
[#9]
Quoted:
Here’s my suggestion if they cant alter the mold….
Eliminate the plunger and spring.
Replace them with a small set screw that’s about the same diameter of the plunger tip.
It would stick up and engage the notches in the front sight.
The taped hole would only have to be about 1/4 deep.
Adjust the sight at the range, then locktite the set screw in place.


I could live with that.
Link Posted: 1/27/2012 11:20:04 PM EDT
[#10]
It's quite late for me so my brain is about machined  out for the day. If you still have troubles in the morning, I will check then. Otherwise, a cursory ( emphasis on curse) examination of your problem would reveal that your dies need modifications. Hopefully you have not had all of them cast so your bill is in the mail. The product does look appealing though!
Link Posted: 1/27/2012 11:25:52 PM EDT
[#11]
OK I did just burn a brain cell and examine your problem. The problem as I see it, is that the area that would be machined to accomdate the site post and detent were made the same size as those that you would find in a conventional FSB, but the rib that makes the edge, is MUCH thinner so you would need to make the other area bigger to allow machining for the post and detent. So if your asking, should we make this bigger? My answer is a question, should we make this functional? The answer is plain I think, yes, you should.
Link Posted: 1/28/2012 1:11:37 AM EDT
[#12]
If they haven't been poured, that would be an easy milling set-up for a machinist to increase the width of the cavity in the mold halves.



If they have been poured, I'd rather we simply use a site pin and no detent, If I use mine on a shooter and it moves beyond a simple blue/242 loctite fix, I would have no issues with drilling the front face for a 4-40 setscrew to touch the threads. It would look like a toolroom/armorer modification.
Link Posted: 1/28/2012 1:32:38 AM EDT
[#13]
200 parts at a buck a casting?  Change the molds.

200 parts at 10 bucks a casting?  Change the molds.

200 parts at 100 bucks a casting?  Find a new foundry and change the molds.
Link Posted: 1/28/2012 3:53:46 AM EDT
[#14]
My biggest concern with altering the mold is... it seems the texture where you removed metal would not have that "sand cast" look/texture as the rest of the mold and it would be very obvious where the alteration was done.

Another suggestion I had was to move the front sight post rearward and eliminate about half of the threaded shaft from the bottom of the sight post.  This way, we could drill a much shallower hole further back.  Obviously, this would have an impact on the amount the sight could be adjusted.

John Thomas
Link Posted: 1/28/2012 3:53:55 AM EDT
[#15]
Probably the all around best solution would be to modify the molds.

For match rifles in "service rifle" class, they generally extend the front sight hole and threads all the way through also so they can use a set screw inserted from the bottom of the hole to positively lock the front sight post into place after initial adjustment.  I don't personally get the utility, but, all the big boys do it like that so I do too.  Service rifle shooters are herd animals.  Moo.  Eat mor chiken.

Anyway, I know that might be visually objectionable, but, would work.  A set screw used in place of the detent pin might also be seen as visually objectionable depending upon whether you're looking at the top or the underside of the area in question.

I'm thinking for my purposes, I'll most likely zero the front sight for elevation, lock it down using whatever provision is eventually provided, and forget it.  If the mold cannot be modified without major trouble and/or expense, I'm thinking leave out any provision for detent pin altogether, and blue locktite the front sight post after zero.  Or possibly, just use a small blind pin in place of the detent that could be set (edit to say, "permanently set") in place after zeroing the front sight post.  I mean, how often to you mess with the front sight post anyway?

Link Posted: 1/28/2012 4:22:55 AM EDT
[#16]
Quoted:
My biggest concern with altering the mold is... it seems the texture where you removed metal would not have that "sand cast" look/texture as the rest of the mold and it would be very obvious where the alteration was done.

Another suggestion I had was to move the front sight post rearward and eliminate about half of the threaded shaft from the bottom of the sight post.  This way, we could drill a much shallower hole further back.  Obviously, this would have an impact on the amount the sight could be adjusted.

John Thomas


John's concern with modifying the mold and loosing the textured cast look is my fear with changing the mold.  Another fear is that the production run has already been poured or is in th process of being poured.  I will find out more on Monday when I call the foundry.
Link Posted: 1/28/2012 4:24:44 AM EDT
[#17]
Looks like you could put the extra material on the front strap or webbing, it looks a lot thinner than the stock FSB, this area looks machined or belt sanded, so the mold change texture wouldn't be a big deal.
Link Posted: 1/28/2012 6:16:03 AM EDT
[#18]
if you sandblasted the mold after modification wouldn't that even out the surface texture?
Link Posted: 1/28/2012 6:31:32 AM EDT
[#19]
If you already have done the parts run, the easy solution is just to tap and drill for an AK front sight post.  it uses the spring action of its legs to be retained, and doesn't require a detent or spring.

Apex gun parts has them for $2 each if I recall correctly.
Link Posted: 1/28/2012 6:35:19 AM EDT
[#20]
Quoted:
if you sandblasted the mold after modification wouldn't that even out the surface texture?


I'll ask that question when I talk to the foundry.  They do make molds for people who don't have one, so they will have the equipment to modify the mold.  I seem to remember the owner telling me that they media blast the parts after the gates are removed.  That is why they have a brighter look than the first test casting that Jess had done.  Maybe I'm worrying about something that won't even be a problem.  Again, this is all dependant upon the whether the foundry has started the production pour.

Link Posted: 1/28/2012 6:37:35 AM EDT
[#21]
Quoted:
If you already have done the parts run, the easy solution is just to tap and drill for an AK front sight post.  it uses the spring action of its legs to be retained, and doesn't require a detent or spring.

Apex gun parts has them for $2 each if I recall correctly.


Sven, that's a good idea.  Now the purists here may condemn us for even considering a part from the dark side, but I think you might be onto something there.

Link Posted: 1/28/2012 6:55:07 AM EDT
[#22]
I like the set screw idea - why not mount the set screw horizontally, so it impacts the sight post at a 90 degree perpendicular angle? A small allen head set screw, say 4-40 should do it, and it'd be an easy fix. It wouldn't impact the detent notches on the sight post, just the post itself, but who gives a rats ass? I also think the AK post idea has great merit, perhaps simpler and more elegant solution. Does it have the adjustability required however?
Link Posted: 1/28/2012 7:01:53 AM EDT
[#23]
Here is a picture of Yugo AK sight post compared to a Colt M16A1 sight post, what do you guys think about this solution.  We would need to do some machining or filing on the ak sight to get it closer to what I think most of us would want.  What say the hive?

Link Posted: 1/28/2012 7:14:37 AM EDT
[#24]
Quoted:
I like the set screw idea - why not mount the set screw horizontally, so it impacts the sight post at a 90 degree perpendicular angle? A small allen head set screw, say 4-40 should do it, and it'd be an easy fix. It wouldn't impact the detent notches on the sight post, just the post itself, but who gives a rats ass? I also think the AK post idea has great merit, perhaps simpler and more elegant solution. Does it have the adjustability required however?


What I like about the AK sight post idea is that we could use one of those cheap $5 AK front sight post tools to adjust the elevation on the sight.  Here is an idea of how we could modify the AK sight to look more like the AR sight.

Link Posted: 1/28/2012 7:27:52 AM EDT
[#25]
You could drill & tap for a locking heli-coil. This would solve the problem of retaining the sight post without the detent or a set screw, and it will still be easily adjustable. I used one on the rear sight for my Gatling project and it holds great.

Link Posted: 1/28/2012 7:47:15 AM EDT
[#26]
Link Posted: 1/28/2012 7:51:51 AM EDT
[#27]
Sorry if this is mostly my fault. There seems to be plenty of material on the rapid prototype. I think the best solution would be to move the front sight post forward a little bit and either not use the detent or use a different kind of detent like a set screw or something else.
Dustin
Link Posted: 1/28/2012 7:56:40 AM EDT
[#28]
Link Posted: 1/28/2012 8:13:33 AM EDT
[#29]
Quoted:
Sorry if this is mostly my fault. There seems to be plenty of material on the rapid prototype. I think the best solution would be to move the front sight post forward a little bit and either not use the detent or use a different kind of detent like a set screw or something else.
Dustin


Dustin, please don't blame yourself for this.  We are lucky you donated your time and skill for this project.  I think this is one of those small oversights that many of us involved did not catch, so pointing blame won't help.  Oh, shrinkage on the part didn't help us either.  I only hope you understand how much all of us appreciate your help with this project.  If there is one thing that I've learned in this whole process it is that we should all appreciate what a company goes through trying to bring a product to market.  How many times in history has such a problem occurred.  Who's to say that the original FSB even had a detent, maybe it had something more like the AK.
Link Posted: 1/28/2012 8:26:32 AM EDT
[#30]
I very much like the idea of the AK type site and sincerely appreciate the work and effort that you and others are putting into this project.
Link Posted: 1/28/2012 8:28:48 AM EDT
[#31]
It seems to me that the easiest way to solve it might be to move the sight pin forward a bit and tap the hole all the way through. A small set screw up from the bottom would lock the sight pin shank and wouldn't be visable. I think that is what Andouille said, and it's how I'd finish mine.

It's unfortunate that this happened but it's common in design & development. Most of the initial run usually goes in the trash.

Thanks for your work with the castings JT, I'm sorry that my present situation has prevented me from being more involved
Link Posted: 1/28/2012 8:39:17 AM EDT
[#32]
Quoted:
I very much like the idea of the AK type site and sincerely appreciate the work and effort that you and others are putting into this project.


A big +1 on this. As an aside Jerrell - good to 'see' you here. Please give our best to Susan.
Link Posted: 1/28/2012 8:40:40 AM EDT
[#33]
I don't know if this will help but, I do have a picture of the original.

The detent is in the front and the material is very thin, the detent may even be smaller.

Link Posted: 1/28/2012 8:43:19 AM EDT
[#34]
I'm wondering if a different detent from a LPK would be a smaller diameter? Don't have my LPK bin in front of me, but it's a thought.
Link Posted: 1/28/2012 9:01:45 AM EDT
[#35]
Quoted:
I'm wondering if a different detent from a LPK would be a smaller diameter? Don't have my LPK bin in front of me, but it's a thought.


smallest one with a lip is the a1 rear sight wheel detent iirc.
Link Posted: 1/28/2012 9:08:40 AM EDT
[#36]
Is it smaller than the front sight detent? I mean, they don't need much extra material from the look of that last pic.
Link Posted: 1/28/2012 9:21:37 AM EDT
[#37]
I love how this forum comes together for the collective good of the group.  It sure sounds like we have several great ideas here.  Well, one way or another several people wanted a raw casting to do their own machining, so it will be interesting to see what some people end up doing with their stuff in the end.  I for one don't have those skills, so I'm going to rely on someone else to help me with my sight when I get it ready to be machined and mounted.
Link Posted: 1/28/2012 9:25:11 AM EDT
[#38]
Quoted:
I don't know if this will help but, I do have a picture of the original.

The detent is in the front and the material is very thin, the detent may even be smaller.

http://i28.photobucket.com/albums/c248/GKCF/Internet%20photos/arfsp4.jpg


Well, that picture confirms it.  Thanks 57Octane
Link Posted: 1/28/2012 9:35:29 AM EDT
[#39]
I think a + 1 is in order for using the rear site detent if the mold can't be modified. Here is a top down view of the front and rear site detents.The rear site detent will engage the slots on the frt site pin IF positioned close enough. If you need actual caliper measurements let me know and I'll give you a digital readout.
Link Posted: 1/28/2012 9:42:57 AM EDT
[#40]
Quoted:
Sorry if this is mostly my fault. There seems to be plenty of material on the rapid prototype. I think the best solution would be to move the front sight post forward a little bit and either not use the detent or use a different kind of detent like a set screw or something else.
Dustin

No finger pointing,,and if anyone dares to,you can rest assured the rest of us will beat them down. You did one HELLAVA job with this project.Hell,I was NEVER even "in" for one,but after seeing this all come together,,,how could I not,even my Buddy Nick is down for one!!!

Link Posted: 1/28/2012 10:17:21 AM EDT
[#41]
Looks to me like the rear sight detent scheme is the winning hand.
Link Posted: 1/28/2012 10:55:20 AM EDT
[#42]
Does anyone know what happened to all the surplus M16A1 small parts that JSE Surplus recently had on their website.  I seem to remember them having New Old Stock (NOS) bags of A1 rear sight detents.  Now I can't find them.  Surely they didn't sell off all that stuff.  They had like sixty something of the M16A1 pistol grips for like $8 ea.
Link Posted: 1/28/2012 11:27:50 AM EDT
[#43]
Try Sherluk - I'm pretty sure they'll have them.
Link Posted: 1/28/2012 11:46:12 AM EDT
[#44]
Im gonna try and get my head  wrapped around this. After getting my h/g's and 601 lower in yesterday, I was thining about checking up on this thing.
Looks like my SBR stamp wont be a hold up on this build.

If you guys want some A1 posts and detent to work Ill supply them


I personally like that original sight post.
Link Posted: 1/28/2012 11:46:57 AM EDT
[#45]
You could also drill the hole for the detent and spring at a slight angle, allowing for more material front and aft of the assembly.  I don't see anything wrong with the original FSB configuration either.
Link Posted: 1/28/2012 3:34:53 PM EDT
[#46]
Another angle would to be blind cross drill a 1/6 dia. hole into the sight post threads and inset a piece of 1/6 nylon rod. And make it into a self locking thread.  self locking screw
It would stay put, but still turn easy enough to adjust with a front sight tool,
I've had several USGI surplus no drain hole butt stock screws that was made with a white nylon locking insert to keep the screw from loosening up.
You can get 1/6 nylon rod from McMaster Carr.
1/6 nylon rod
Would not need to worry about a detent pin.
Just a thought.
Link Posted: 1/28/2012 4:37:45 PM EDT
[#47]
My choice would be
Mod molds if pour hasn't happened
Smaller detent
loctite
4-40 drainhole setscrew.


pezboytate, aprox 200 of us have OK'd the design by our excitement and pushing this forward. Even more have seen the thread. You have no part of any blame for what we all missed. Shrinkage was brought up early on. We were all worried about the cosmetics being perfect. It is normal during R&D to find issues due to castings, foundry techniques, alloy, machining, fixturing, and sometimes finishing, that all require minor changes or complete redesigns. This may not be the last issue before we get these in our hands.
I want to thank everyone who has been involved in this project with their time, suggestions, work, and enthusiasm.
Link Posted: 1/28/2012 7:30:54 PM EDT
[#48]
use a wire, as a tension or torsion spring to fit in the detent slot on the front sight,
maybe have it coiled or inserted in a base (think extractor for a grease gun/1911 type) that is inserted from the top, short enough to extend just slightly above the base of the sight at it's full adjustment height, and strong enough to spring against the front sight  and still be able to be pushed out of the way to adjust,

just a thought
Link Posted: 1/28/2012 7:51:31 PM EDT
[#49]
Guys,

I think I have this figured out!!!  I squeezed the threaded post and detent as close together as I thought I could, then cut the notches in the sight where the detent rests a little deeper.  It works great, and looks correct.  

There is one thing that I may do differently... it's the gas tube hole.  On the photos I saw of the original prototype FSB, the hole went all the way through, but the gas tube extended nearly to the front face of the FSB, so the hole in the front was very shallow.  With the length of today's gas tubes, the face of the gas tube is recessed pretty deeply in the FSB and the hole in the front is deep rather than shallow.  I'm going to recommend not drilling completely through as I did on this test piece.  I think it will look more accurate if we just go to the required depth.

Thanks to everyone involved in this project to getting it where it is now.  Especially 04ZREX.  It appears we are getting close!!!

Pictures are below (forgive my use of an A2 sight post... I didn't want to ruin a A1 post in case this didn't work)––also, at the very bottom is a photo of the original showing what I mean about the face of the gas tube:



















Link Posted: 1/28/2012 8:03:18 PM EDT
[#50]
bravo.  clap clap clap.  
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