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  #1  
Old 01-11-2014, 8:58 PM
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Default Made my own free float barrel nut/hand guard, what do you guys think?

Hey All,

I am in the process of building an AR specifically for when I shoot 3-gun. It has a surefire brake, heavy 20" SS barrel, and lightweight carrier/ adjustable gas block. I was looking at the JP FF handguards and then it hit me, what do these guys have that I don't, other than the proper equipment and decades of experience?

So, last year in school I got to take I project class where I learned how to turn on a lathe and mill and perform the most basic of functions. I thought this project would be fun and help further familiarize myself with the machines.

I took a ton of photos along the way. Feel free to ask about any of the finer details and I can probably show you a picture of my fixture and process.

Let me know what you think and be as critical as you like, I am about as amateur as they come in this area right now.

All that is left is to heat treat the barrel nut and figure out what kind of finish I want to put on it. Then I am also going to type III hard coat anodize the handguard. The nut is 4140 steel and the sleeve is 6061 Aluminum. The total length is about 15 1/4" and has an ID of 1 3/4" and OD of 2". It centers just about perfectly around the barrel and just barely clears the gas tube and block.






Thanks for looking,

Jon
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Last edited by $P-Ritch$; 01-11-2014 at 9:01 PM..
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  #2  
Old 01-11-2014, 9:10 PM
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Pretty sweet! You should torture test it to see how it holds up to abuse

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  #3  
Old 01-11-2014, 9:14 PM
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Thanks, I took it out of the vise last night and shook the bejeezus out of it and there was no wobbling at all. I want to wait until the nut is properly heat treated before I fully torque it on and test fire with it and really put it through the paces.
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Old 01-11-2014, 9:36 PM
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That is very nice.

Are you just using manual lathe/mill with a DRO....if so, props on the threaded portions. Not the easiest thing to do on a lathe.
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Old 01-11-2014, 9:42 PM
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Really nice! Good Job!
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Old 01-11-2014, 9:43 PM
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Nice! Make me one!!!
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Old 01-11-2014, 9:52 PM
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Thanks again, the mill had a DRO, but the lathe I used was all dials.

toddh, I did not have the tooling to thread on the lathe, instead I bought a 1 1/4" - 18tpi tap from brownells and used the dead center to help cut the threads. None of the tap handles in the shop could fit that monster.

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Old 01-11-2014, 9:52 PM
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So you programed that up on a vertical with a fourth axis swinging the A?
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Old 01-11-2014, 9:59 PM
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All hand cut? Gorgeous work!
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Old 01-11-2014, 10:02 PM
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looks great!
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  #11  
Old 01-11-2014, 10:23 PM
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Originally Posted by Syds Grandpa View Post
So you programed that up on a vertical with a fourth axis swinging the A?
Not sure what that means, I'm assuming it is CNC stuff. This was all manual on separate bridgeport mill and lathe. I got to make use of a dividing head for the first time and that made life a whole lot easier for the concentric details of the holes and grooves.
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  #12  
Old 01-11-2014, 10:28 PM
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Indexing head! I've heard shop teachers call the "Dividing heads" before, nobody in the trade calls them that. You are a very talented individual. We should talk sometime.
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  #13  
Old 01-11-2014, 10:33 PM
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***

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  #14  
Old 01-12-2014, 4:53 AM
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Nice work!
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Old 01-12-2014, 5:46 AM
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Good work for manual turning.
Man I miss my shop tools
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Old 01-12-2014, 7:09 AM
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Quote:
Originally Posted by Syds Grandpa View Post
Indexing head! I've heard shop teachers call the "Dividing heads" before, nobody in the trade calls them that. You are a very talented individual. We should talk sometime.
In all the shops I've worked in a indexing head was a collet indexer or a crude dividing head, But a dividing head was the precision heavy as hell tool that had the multiple plates on it.

P-Ritch you did have the tools to cut the threads you just didn't know it. And Nice work by the way. Get to the same point on the lathe as you did right before you used the tap then you go over to the gear box on the machine and set it up to cut you thread pitch


On my machine i'd set it up on "B" "2" with my standard gearing, set one more lever to engage the lead screw and disengage the feed shaft.

Go hand grind a internal thread cutting tool from a HSS blank or just buy one off the shelf for $15 set it up in the toolholder. Set up your compound at 29˚ to the cross slide, set your tool square to the part using a fish gage. set you RPM's at about 200, turn on the lathe and touch off inside the part, set your cross slide to zero and your compound to zero. Do a little math and figure out that you need to feed the compound in to about .055", dial the tool clear of the part on the carriage and bring it back to zero on the cross slide. Set your feed selection lever on the carriage to neutral and use the half nut lever to engage the lead screw. dial the carriage about a foot away from you part to test the direction of feed. turn on the lathe and engage the half nut. The carriage should be feeding toward the chuck, If not find you feed reverse lever and reverse the feed direction. Make sure your thread indicating dial is engaged to the lead screw and it is turning when the lathe is running.
Ok you are now ready to cut a thread. Dial the carriage up close to the part. Dial in .005" on the compound (keep in mind you are cutting an internal thread so you are feeding the tool toward you not away from you.) apply some cutting oil and hit the half nut when any line lines up with the arrow or dot on the thread indicating dial (even number of threads can engage on any number or line odd number can only engage on on odd numbers)

Watch the tool feed down the part taking a cut as it passes through the part and clears it disengage the half nut dial in the cross slide to clear the tool and dial the carriage back to your starting position. return the cross slide to the zero position again and dial in another .005" on the compound.
repeat this process until you are with in the last .010" of full depth. that when you can start checking your fit. then last .010 can be dialed in with the cross slide to produce a fine surface finish.

It's actually very complicated to explain as you can see but in practice is quite easy.


Now if you have access to a cnc lathe it would be programed something like this and no this is not an exact program and may not function as written but it shows the basic concept

N1 G50 S600
N2 G00 X20 Z20
N3 X-1.150 Z1.750 G97 S450 T101 M03 M08 M41
N4 G71 X-1.250 Z0.0 B60 D.010 U.002 H.110 L.3 F1 J18 M23 M33 M73
N5 G00 X20 Z20 M09
N6 M02

Yeah I can program those too. But I can have threads cut on a part before a guy can get the machine set up and programed on a CNC.
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  #17  
Old 01-12-2014, 7:49 AM
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Thanks a bunch for the explanation, kcstott.

Last year in my shop class we had to cut external threads with a lathe for a lab. So, this all sounds really familiar. The only part I'm confused on is how the math works to choose the proper feed rate. I'm not seeing how setting B2 correlates to 18tpi.
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  #18  
Old 01-12-2014, 8:45 AM
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What is the weight of the set up?

It looks beefy but you seems to have taken a lot of the weight out of the handguard with the holds.


For cosmetics- it looks great.

Please post pics after heat treat and HA
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Old 01-12-2014, 8:50 AM
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Quote:
Originally Posted by $P-Ritch$ View Post
Thanks a bunch for the explanation, kcstott.

Last year in my shop class we had to cut external threads with a lathe for a lab. So, this all sounds really familiar. The only part I'm confused on is how the math works to choose the proper feed rate. I'm not seeing how setting B2 correlates to 18tpi.
because you don't use feed rates you use the threads per inch feeds setting bottom left block on the face plate picture i posted. 1-6 across the top is a gear box lever and A,B,C. is another lever
all levers in correct position and it works like a champ.

Youtube is good for one thing after all.
I just went out to the garage and fired up the lathe. shot the video and posted.
Yes it quick and dirty but it gets the job done.


Look out I fixed it.

Last edited by kcstott; 01-12-2014 at 11:09 AM..
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  #20  
Old 01-12-2014, 8:57 AM
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That's a lot of cranking unless you had a powerfeed on the mill. Looks great.
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Old 01-12-2014, 8:59 AM
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Originally Posted by kcstott View Post
Youtube is good for one thing after all.
http://www.youtube.com/user/mrpete222
http://www.youtube.com/user/KEF791

Those two channels will inform and inspire.
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Old 01-12-2014, 9:20 AM
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Good info there milotrain. Now i'll have some hours to kill
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Old 01-12-2014, 3:38 PM
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Keith's videos are especially good, he goes on these tangents where I've learned a huge amount of information. He also makes a lot of custom cutters and silver brazes them to tool shanks, which opened my eyes as far as the capabilities of custom tooling goes.
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Old 01-12-2014, 7:16 PM
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Quote:
Originally Posted by hermosabeach View Post
What is the weight of the set up?

It looks beefy but you seems to have taken a lot of the weight out of the handguard with the holds.


For cosmetics- it looks great.

Please post pics after heat treat and HA
Have not had a chance to weigh it yet, but there is a scale in the shop I can check on tomorrow. The wall is noticeably thicker than my troy alpha rail and it is larger in diameter, but there not be a picatinny top rail should help even out the difference.

Quote:
Originally Posted by kcstott View Post
because you don't use feed rates you use the threads per inch feeds setting bottom left block on the face plate picture i posted. 1-6 across the top is a gear box lever and A,B,C. is another lever
all levers in correct position and it works like a champ.

Youtube is good for one thing after all.
I just went out to the garage and fired up the lathe. shot the video and posted.
Yes it quick and dirty but it gets the job done.
Thanks a bunch for the video! It helps a lot, I think when I try this again down the road I will cut the threads with the lathe.

Quote:
Originally Posted by milotrain View Post
That's a lot of cranking unless you had a powerfeed on the mill. Looks great.
No powerfeed, just crankin....
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Old 01-12-2014, 7:45 PM
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Quote:
Originally Posted by $P-Ritch$ View Post
Have not had a chance to weigh it yet, but there is a scale in the shop I can check on tomorrow. The wall is noticeably thicker than my troy alpha rail and it is larger in diameter, but there not be a picatinny top rail should help even out the difference.



Thanks a bunch for the video! It helps a lot, I think when I try this again down the road I will cut the threads with the lathe.



No powerfeed, just crankin....

if you've single point cut external threads you can do internal no difference in the set up.

Just get you levers set properly. Ask someone at the shop to confirm your set up or use some dykem and check your pitch. go slow and dial in very little at a time. the surface area of your cutting tool is much larger then a turning tool so dialing in .005" on the compound is actually dialing in .010" on the diameter and due to the surface area it's like dialing in .050" so if you dial in .020" you threads will tear and look like crap.
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Old 01-13-2014, 8:49 AM
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Only thing that is annoying about internal threads is that you need a threading tool holder to really boom out from the compound rest because the compound rest is angled back at the work. I was threading a large disk to make a faceplate and I had to grind a threading tool for a boring bar just to keep from crashing the compound rest.

Also I like nice sharp HSS for threading Aluminum over carbide. It cuts easier and you can run slower RPM. On the above faceplate I had a nice long cemented carbide boring bar that I never used so I ground it first but it just wanted to skip out of the work and I got a lot of tool deflection. The HSS tool bit I ground just cut right through, and my spring cuts took off very little material.
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Old 01-13-2014, 9:30 AM
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Use a typical 29 degrees setting with the compound swung away from the chuck and run the machine in reverse. You'll also have to feed in reverse too but it keeps you from crashing the compound or tool.

We would set up our threading jobs in reverse anyway so we were feeding off the part, not in to a shoulder, it's one reason I like left hand threads.

I caution the newbe in doing a set up like this as it takes a little bit of forethought. You can get all set up to cut a right hand thread and not think about your feed direction and cut it left handed. Seen that happen in trade school once.
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Old 01-13-2014, 9:52 AM
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My atlas motor is currently detached from the lathe so that I can wire up a new reversing switch. Primarily for metric threading though.
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Old 01-13-2014, 11:23 AM
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I was able to weigh the parts today.

Barrel nut: 5.15 oz
Handguard: 11.55 oz

Just for reference a 15" troy alpha rail weighs 11.12 oz
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Old 01-13-2014, 11:43 AM
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I am jealous of your skills! Very nice looking rail!
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Old 01-13-2014, 12:23 PM
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That bad boy looks awesome!
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Old 01-13-2014, 12:38 PM
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It looks nice enough to leave it as it is, good job.

Okay 2 questions;

1: At this point, roughly how much money do you have in it?
2: Roughly how much time so far?
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Old 01-13-2014, 1:24 PM
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Originally Posted by Hot Holster View Post
It looks nice enough to leave it as it is, good job.

Okay 2 questions;

1: At this point, roughly how much money do you have in it?
2: Roughly how much time so far?
1: a lot
2: a lot

I knew this project would cost me way more money and time and more than likely yield an inferior product than just buying an aftermarket rail. I did it because wanted to boost my experience on the shop machinery and I just enjoy DIY projects.

For more quantified answers,

Raw materials:
3ft Al tube (2.25" OD, 1.75" ID) from McMaster - $80
6" 4140 rod (2" OD) from McMaster - $24

The 3ft tube is enough for 2 15" handguards. If I went down to 10-11" I might be able to get 3 out of it. The barrel nut is just under 1.25", so I could get 4 out of the rod if I wanted to. That puts me at $48 for materials for this one I have made because I used half of the Al and 1/3 of the steel.

I also did not have all the lathe tools and end mills that I needed. I spent about $150 on those, but those will be available for other projects as well now.

Lastly, the finishing. I expect to spend around 150 bucks to get the handguard blasted and anodized and the nut heat treated and parkerized (or whatever kind of coating they offer).

All in all it will be getting close to $500 for the first iteration. I want to try and refine my process and design and if I do a MkII variant it should be considerably cheaper.

In regards to time: I easily have at least 30 hours put into it. Once again, that was a lot of figuring things out for the first time and learning along the way. Now that I have gone through from start to finish I feel the second attempt would go by much faster.
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Old 01-13-2014, 1:28 PM
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Quote:
Originally Posted by $P-Ritch$ View Post
1: a lot
2: a lot

I knew this project would cost me way more money and time and more than likely yield an inferior product than just buying an aftermarket rail. I did it because wanted to boost my experience on the shop machinery and I just enjoy DIY projects.

For more quantified answers,

Raw materials:
3ft Al tube (2.25" OD, 1.75" ID) from McMaster - $80
6" 4140 rod (2" OD) from McMaster - $24

The 3ft tube is enough for 2 15" handguards. If I went down to 10-11" I might be able to get 3 out of it. The barrel nut is just under 1.25", so I could get 4 out of the rod if I wanted to. That puts me at $48 for materials for this one I have made because I used half of the Al and 1/3 of the steel.

I also did not have all the lathe tools and end mills that I needed. I spent about $150 on those, but those will be available for other projects as well now.

Lastly, the finishing. I expect to spend around 150 bucks to get the handguard blasted and anodized and the nut heat treated and parkerized (or whatever kind of coating they offer).

All in all it will be getting close to $500 for the first iteration. I want to try and refine my process and design and if I do a MkII variant it should be considerably cheaper.

In regards to time: I easily have at least 30 hours put into it. Once again, that was a lot of figuring things out for the first time and learning along the way. Now that I have gone through from start to finish I feel the second attempt would go by much faster.
Actually, I think you did well for the money-material ratio.

I would have thought a few hours less in time, but I didn't figure in the prepping being the first run for this.

I still think it was well worth it.
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Old 01-13-2014, 3:52 PM
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OP, this career machinist rates your work two thumbs up! Looks great.
As far as spending money on tools, you got it, buy it once and take care of it and you'll have it to use over and over again.
I wish I had your enthusiasm, but after 35 years in the business and countless "G jobs" from custom choppers to camera parts, I'm pretty much burned out on spending any more time in the shop than I have to.
BTW, kcstott is a good man to listen to, he is very knowledgable about all phases of manufacturing and is always right on with his advice.

Congrats on a job well done!
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Old 01-13-2014, 6:44 PM
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I like your work.

I recently inherited a mini lathe and am working on learning how to use it. I turned down a handguard end insert to fit another handguard today, didn't do the cleanest job but at least it's all hidden. Yours, on the other hand, looks nice.
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Old 01-13-2014, 6:54 PM
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Yeah I'd be tempted to clear anodize and call it good. It does look top notch.
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Old 01-13-2014, 7:58 PM
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Thanks for all the compliments guys. I'm probably going to anodize black because it is hard to see in the pictures, but every other groove in the texturing has these little micro burrs/flags in it. I was zig zagging back and forth with the cutter. Only on the conventional cuts did the burrs occur. When I was doing the climbing cuts the cutter went through it like a hot knife through butter and left a super clean finish. I can flake off all the little burrs with just my finger nail, they are that thin, but there still a small mark where they used to be. So, I figure a good, thorough bead blasting with take every last one of them off and give it a nice uniform finish with plain old matte black.

Victor, I'd imagine 35 years of any activity will start to wear on you a bit. I'm definitely appreciative of all you experienced gentlemen on here that can point us noobs in the right direction and give us sound advice.

Jon
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Old 01-13-2014, 8:07 PM
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Nice machining work !
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Old 01-13-2014, 8:11 PM
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Thanks again, the mill had a DRO, but the lathe I used was all dials.

toddh, I did not have the tooling to thread on the lathe, instead I bought a 1 1/4" - 18tpi tap from brownells and used the dead center to help cut the threads. None of the tap handles in the shop could fit that monster.

Looks like a Victor lathe
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