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By MetalShavings

March 7, 2019, 3:44 pm

41v50 Rifle Barrel Steel

It's been a while since I visited here. I've been setting up to do some Spiral Fluting on an incoming rifle barrel project on my Tormach 770 mill.

Setting up everything including the 4th-axis is pretty straight forward. Working on typical 4140 and stainless rifle barrels isn't really hare either but, my apprehension here has more to do with metal alloy I'll be working with in this barrel project.

I've run the numbers in my copy of HSM Advisor and I'm coming up with some feeds and speeds numbers that kind of leave me scratching my head.

I'll be using a 30 degree helical 4-flute coated carbide end mill. My flute length and stick out is one inch. It's a typical configuration ball nose end mill. My DOC is only .008" and I'm running it with the "Pocketing" box checked. The alloy that this barrel is made of is 41v50 steel. I had never heard of this type of metal till I came across it when purchasing this sample barrel. Apparently the military uses this alloy on their AR platform rifles for durability and rigidity.

My reason for posting was to ask; has anyone here ever worked with this metal alloy? Also. I've deliberately not listed the feeds and speeds I came up with because I wanted to ask those of you who may be willing to run the numbers in your version of HSM Advisor and see what you come up with. It may be that there's something I'm missing or inputting incorrectly when I enter this info in the their respective text fields.

I can tell you that any time I do any milling with my One-Horse-Power Tormach mill I have to back off of the actual speeds and feeds I'm given by at least two-thirds. With hard metals like this 41v50 I'm thinking that I will most likely have to back off even further than two-thirds.

I'll check back here later in hopes of someone being kind enough to run these numbers to see how the numbers they come up with compare to what I've came up with. Thanks in advance. If more information is needed please let me know and I'll make sure to include that with a reply.

MetalShavings

Answers:

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Eldar Gerfanov

March 7, 2019, 4:57 pm

Hi,

You did not specify what diameter the tool is, so i assume its 0.5"
If you only do one pass slotting at 0.008" deep, then check the first screenshot.
I use 2 flutes because a 4 flute ballnose end mill has only 2 flutes cutting at that depth.

If you are actually making multiple 0.008 slotting passes to get to (for example) .125" depth, then you need to calculate as if you are slotting at 0.125". In this case you should set the number of flutes to 4. See the second screenshot.

You should provide more info because a seemingly insignificant detail may cause significant change in parameters for ball nose cutters.

A ballnose end mill may exert large cutting force on your machine, so do not forget to adjust for your machine rigidity.

Best regards.

1 pass 0.008 Deep 2FL.PNG Multiple passes ending with .125" 4FL_Deep.PNG
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MetalShavings

March 7, 2019, 6:32 pm

Hi Eldar:

I knew this was going to happen. I mean forgetting to enter more pertinent information. Actually I planned on using a 1/4" diameter 4 flute coated carbide ball nose end mill. It will be done in multiple passes of .008" each and the full depth is only .048" deep.

Why am I doing these spiral flutes this shallow? It's because I only want to score the surface with the spiral pattern I've modeled. I don't want anything deeper than this. Initially I was going to make the flutes .10" deep but when I calculated the numbers my feed rate was so slow that it was more a kin to a crawl-rate rather than a feed rate.

My HSM Advisor software was telling me that I needed an RPM of 10,000 and a feed rate of 3.7. With was with me backing down the feed rate to accommodate the low power of the mill and to minimize the torque and deflection of that skinny quarter inch diameter end mill.

I am glad to see in your screen shots that you picked as the metal alloy the 4150 alloy that was the harder of the two 4150 alloys that are listed in the drop down menu. At least I got that right.

Would you suggest using a two flute coated carbide end mill instead of a 4 flute? This project is still in the working stage so if something like a 3/8" end mill might be a better fit for this kind of spiral flute project (especially on this type of hard alloy) I still have a bit of time to order one to use instead of the 1/4" ball nose I initially intended to use.

Thanks for the quick reply.

MetalShavings

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MetalShavings

March 7, 2019, 6:41 pm

I also needed to mention that in your screen shots you have listed as your milling machine a 30 horse power VS series Haas. Mine is a one horse power Tormach hobby mill and when I entered my numbers to get my calculation I too checked on the "Slotting/Pocketing" check box to activate it.

I didn't notice that difference in CNC milling machines when I first viewed your scree shots. I really loved the numbers you came up with when I first saw them. Even if I had to reduce those number by two thirds they still would have been faster than my numbers. That's when I noticed the difference in hose power and rigidity.

I really just want to confirm that the snails-pace numbers I came up with are somewhere close to being right. If I have to run a real slow feed rate I'm OK with it. I just want to make sure my feeds and speeds are good for the task at hand.

MetalShavings

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Eldar Gerfanov

March 8, 2019, 9:21 am

Hi,

Machine type actually does not affect anything in this calculation.
The HP requirements are so low, that it does not matter Tormach of HAAS.
There is stiffness issue of course, but it should not make too much difference.

Couple of points to make your machining more successful:

1. Most important: Use stub length end mill.
If you need reach, then you can stick it out further, but try to get the shortest flute possible.
1" long flutes that you mention is very long. your endmill will flex all over the place
2. Use 2 flute coated carbide endmill.
3. Use coolant: it will help you with heat buildup and friction in the tip.

I personally would start with the parameters as per screenshot.
But yet again i have not worked on Tormach, so you might want to start 50% slower in both the speed and feed.

Good luck!

0.25 Ball Engrave Capture_025.PNG
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MetalShavings

March 8, 2019, 11:22 am

Many thanks Eldar:

I notice in this latest screen shot this time around you do not have the "Slotting/Pocketing" box checked off. Is there a reason for this other than possibly forgetting to check off that box? It could be that it's not really needed in this type of milling operation, I don't really know. That's why I'm asking.

I'm happy to see the numbers you've come up with but it still leaves me scratching my head. With the exception of the "Stick-Out" and "Flute-Length" differences (and not checking off of the "Pocketing" icon) I entered basically the same numbers as you did and got some very different numbers. No matter; I would much rather work with the numbers you got than the numbers I initially had gotten.

My barrel blank should arrive next Tuesday so that will give me some more time to order a shorter quarter inch cutting tool for the job. I plan on doing some test cuts on some Delrin rod stock just to make sure my tool paths or OK. I still have to thread and chamber the barrel before I get to the fluting stage of this project.

I'll let you know how it turns out. Thanks again for your help. I really appreciate it.

MetalShavings
Tim M.

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Eldar Gerfanov

March 8, 2019, 11:52 am

Hi Tim,

The Even though "Slotting" is off, WOC is the same, so it does not affect anything.

I am not sure why you are getting very different values.
Please send me a screen shot of your HSMAdvisor window with all panels expanded.

Regards.

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MetalShavings

March 9, 2019, 10:45 am

I'll try to get that screenshot tonight if I can figure out how to do it.

MetalShavings

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MetalShavings

March 11, 2019, 7:15 pm

For the last couple of nights I've been trying to get that screenshot I promised in my last reply. No matter what information I've entered in the text fields I can't get it to churn out the same results I got the first time I tried.

The first time around I entered all the data I listed in my initial post on this thread. Entering that same information I'm now getting numbers that more closely resemble the numbers you came up with when you were kind enough to run similar numbers in your version of the software. I did find one difference in the data we input. My Stick-Out was listed at one inch with a flute length of one inch as well. Yours is listed as .625" and .500" respectively.

I'm not sure if that could account for the major difference. In my initial calculations I also lowered my feed rate to minimize the torque and deflection so maybe it was these three settings that gave me those initial feeds and speeds of 10000RPM and 3.7in/min.

I'll keep looking for the source of my error as time permits. I'll also remember to post the results once I get this project done.

Thanks for your help.

Tim M.

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MetalShavings

May 3, 2019, 3:44 pm

I didn't want you to think I'd forgotten all about this post. I'm still working on this project but I had to put it on the back burner while I repaired my backyard fence. I had some pin-headed teenager crash in mom's car through my back yard fence and it's taken some time to deal with my insurance company to get it fixed. I eventually had to fix it myself.

Also; because of the very small work envelope of my Tormach 770 mill I've had to fabricate extra parts in order to secure and index my barrel blank in my 4-Axis setup. I got the fence fixed. Now I have to find some more free time to continue with this barrel fluting project.

I shall return.

Tim M.

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Eldar Gerfanov

May 3, 2019, 3:57 pm

Lol damn kids!
Not as bad as a house on our street that was under construction and got gutted because some stupid kids decided to start a fire inside....8(

Do not worry about it.
When you get back to it, make sure to use the latest version as well.

Regards!

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MetalShavings

May 7, 2019, 3:38 pm

A few days back I spent the morning cutting air as a test of my tool paths with this fluted barrel project. My home made spring loaded felt marker confirmed that all my tool paths were good but I ran into a problem with the thread protector on the muzzle end of my barrel blank.

It seems that my 4th-Axis unit worked well enough but when the tool path called for a clock-wise rotation it tended to just unscrew the thread protector from the barrel blank so I had to fabricate another type of thread protector with a slit cut along one side so as to allow the jaws of my vice to clamp down on the muzzle threads without damaging them and securely keeping the barrel from rotating during machining.

I made a similar thread protector for the chamber end cause I knew if the muzzle end was unscrewing during certain milling operations the chamber end would most likely do the same.

After running those air cutting tests with my felt marker I determined that I had crisscrossing flutes that were spaced to far apart so that it really didn't look balanced out so I went back to the CAD software and added another flute. Now with the crisscrossing flutes it looked like I had to many flutes and it still looked out of balance so, I decided to run all my flutes in the right hand direction and call that good. They looked evenly spaced and overall they looked well balanced for a short barrel blank like this.

This morning I bit the bullet and decided to cut the flutes. My plan was to mill the flutes on the muzzle end of the barrel blank and while I had the barrel already indexed in the 4th-Axis I'd go ahead and do the short center flutes as well. The first three muzzled end flutes went off without a hitch so I loaded the G-Code for the center flutes and it was going just as well as the muzzle end flutes. The feeds and speeds seemed to be spot on. You should have seen the $#it-Eating-Grin I was sporting as I stood their watching my end mill do it's magic. Until, it got to the second to the last little flute.

I don't know what the heck happened. At first I thought that my newly made muzzle thread protector had slipped and the barrel wasn't turning in step with the 4th-Axis. Like an idiot I let it keep running and it did the same darn thing. For some reason my end mill did a left hand turn and started cutting toward the last flute to be cut. By then the end mill had already cut down to about the .1" depth of a .128" deep flute and I really expected for that little 1/4" two-flute end mill to just snap and put me out of my misery. It was at that point that I regained the sense to hit the "E" stop. That little end mill didn't snap. It hung in their.

The barrel isn't ruined by a long shot and it's not a loss of any kind. It's just a real head scratcher cause I checked to see if my muzzle thread protector had slipped and it was still synched down super tight. My computer simulations showed my tool paths working flawlessly but in doing the actual milling operation it went completely off the expected tool path on that second to the last flute. (enter foul language here)

Tomorrow or the next day I'll be cutting more air. This time I'll be testing the tool paths on the chamber end of my barrel blank. If I can get them to come out like the muzzle end flutes I'll be a happy camper with a semi-nicely spiral fluted barrel. I'll then have to go in and doctor up the bad cuts made when my end mill veered off course. If I take my time I'm pretty sure I can make it look like I meant for it to be this way all along but, it sucks that everything is going beautifully and then something like this happens.

At the time I thought to myself, "Oh well, if the bad cut is on the under side of the barrel blank as it sits in the stock it won't be that big of a deal, but as it happens, my tool paths started with the initial little flute being the one on the underside of the barrel blank. The tool path went off the rails as it was cutting the second to the last flute which sits to the right of the top-dead-center flute that I had pre-indexed when I mounted and head-spaced the barrel in the receiver. ****! I guess it could have turned out far worse. I did take some pics that I'll be posting a little later. I have to shrink them down so that I can upload them to the various online forums that are following this project.

Just to let you know; my barrel blank is a $39.00 barrel blank I bought from Green Mountain Barrels so it's not like I'd be out alot of money if I had managed to destroy my barrel blank. Now that I've learned a few things the hard way I may just buy another of these barrel blanks and do it all over again with a little more confidence.

I'll be back with those photos later. I'll be back when time permits. Pray for me brethren; and don't act like nothing like this as ever happened to you either. If it hasn't, just give it some time and I'll be able to empathize with you; or maybe commiserate.

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MetalShavings

May 8, 2019, 5:26 pm

Here are the photos I mentioned earlier. I tried to get a clear close up of the bad cut made by my wondering end mill. The accompanying photo didn't come out as clear as I'd hoped. I chalk that up to being in to much of a darn hurry all the time.

For the most part the spirals came out as I'd hoped. It's just that one 4th-Axis snafu that still leaves me scratching my head trying to figure out what happened. Oh well. I should have did my air cutting tests on all the flutes instead of some of them and then assuming they were all good.

Now for the worst part of all my milling projects. Now I have to clean my mill. I hate that part. Also; I need to mention that in the photos I mistakenly wrote that the Tikka T3 rifle was a Tikka Hunter rifle. My mistake. That was my last project. This particular Tikka is just a Tikka T3 Lite with a synthetic stock.

The feeds and speeds I uses were, RPM 10000 and the feed rate was just 9. Judging from the way my two flute carbide end mill cut through this hard metal when it veered off course, my feed rate could have been a bit faster or my DOC could have been a bit deeper and I still would have come out OK but, after experiencing that unexplainable wondering end mill cut, I'm glad I was cutting as shallow as I was.

MetalShavings.

Spiral Fluted Bull Barrel spiralflutes.jpg Wondering End Mill Bad Cut fluteerror.jpg
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MetalShavings

May 8, 2019, 5:28 pm

Eldar Gerfanov

I almost forgot to thank you for your help with these feeds and speeds. Although I'm getting better at figuring them out, there are still times when I have to cut materials that I've never worked with before. Times like that I'm glad I have people I can ask for input.

Tim M.

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Eldar Gerfanov

May 8, 2019, 6:55 pm

Hi Tim!

I am glad I and my software could be of help!

You did an excellent writeup and I hope you will not mind if I feature your experience/photos on the front page linking to this very thread for details.

I got to ask, though, what is your opinion on how such barrel modification could affect accuracy? I know steel must be pretty stable, but still, is this a factor, especially as the barrel heats up and cools down?

Thank you and best regards!

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MetalShavings

May 8, 2019, 11:08 pm

I've always heard that a more rigid the barrel the higher the likelihood of good accuracy but honestly, I've never owned or shot a rifle with a fluted barrel and from some of the writeups I've read on the subject, I really thing it's more of a cosmetic or aesthetic preference than anything else.

I'm sure that some will swear that it helps accuracy but I don't have any first hand knowledge on the subject. I hope to have once I get this project done. I mainly did it to bring the weight of my barrel blank down to more closely match the weight of the factory barrel I took of this same rifle; and because I think it looks kind of bad-ass with flutes as apposed to just a straight tapered barrel.

By tapering it and then fluting it I was able to get the weight to within .7 ounces of the weight of the factory barrel. What this means is that the balance of the rifle will be about the same as it was when it was in it's factory configuration. That's what I was shooting for. I will have to wait and see if all of this effort has produced an accurate rifle. If not, I now know how to do this so I can either give it another shot or just put the factory barrel back on.

In regard to using this write up; I don't mind. I know I'm not the only one who has had machining snafus. I still have to figure out exactly what happened to make my end mill veer off course but I'll worry about that after I've finished this project.

Thanks again Eldar

Tim M.

Answers:

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