Posted: 5/8/2006 3:49:20 PM EDT
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I know nothing about using lathes, etc. I'm having a local machinist do some work for me. I'm wanting an 18.25" seamless 4130 steel tube that is 1" OD and has an ID of .912". The best he could locate was a 1" tube with an ID of .902". I originally told him that I'd make the .902" work. Now I'm having second thoughts and wondering if I should have him ream it out or something. He works second shift, so I won't be able to contact him until the weekend. Anyway, I'd pick up a reamer for him to use if I knew what I needed and where to find it. He'd be using it in a lathe. Thanks. |
| Very difficult to hold a thin wall tube like that for any kind of reaming. Didn't look at a chart, but if .912 is not a standard fractional equivalent, you would have to use an expanding reamer or have one custom made. Best way to get a precision ID is to ream close to size, then have it honed to final size. A hydraulic cylinder shop may be able to help. Or talk to a shop that does shotgun barrel work. |
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the closest one I could find to .912 was .920 on mscdirect.com. He could always grind down a reamer on an OD grinder to give him the right size if he has access to alot of used up reamers. www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1697924&PMT4NO=0 He could also hone it out if he has a mandrel long enough to do at least half the length. |
| If you are not worried about the tolerances of the dia of hole you could get it done with a gun drill. Go with solid bar stock and drill to desired dia. Look here |
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Thanks for the replies so far, guys. It sounds like it may be a difficult process. The closest two ID's he could find in a 1" tube were .902" and .930". The original tube that I'm trying to replicate has an ID of .912". This project is a shotgun magazine tube. Srinking the ID by .010" will require a custom shell follower, as the stock one will not fit inside a .902" tube. |
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Piece of cake. A reamer will need to be ground, but that is not a big deal. 19 inches of reach is not a problem either. Since you are only taking out .005 per side, the reamer will follow the hole just fine. Bore one end of the tube to .9120 with a boring bar about 1.5 inches deep, so the reamer gets a nice straight start. Use plenty of lube, and keep the chips cleared out. Just buy a 15/16 reamer and have it re-ground. Or, you can contact McMaster-Carr, and ask for part # 2777A999 - they will ask you what diameter, and you tell them .9120 Brand new .9120 reamer to your door. I would NOT reduce the size of the magazine tube bore by .010 This could affect functioning, or lead to shells stuck on the tube. BTW - trepanning has NOTHING to do with deep hole making. Lem |
Lem, thanks for the very detailed reply. It sounds like just the info I need. As for the clearance for the shotgun shells, they slop around pretty good in the .912" tube, so I doubt that the .010" reduction would cause tightness. Still, I'd like to replicate the factory size if possible. |
I'm wanting to fabricate a one-piece magazine tube for a Benelli M4 shotgun to replace the current two-piece style. This requires a tube 4.5" longer than the stock one. |
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M4: There are many other ways to do that job. He could press a mandrel through the tube, and size it to .912 - then grind the OD to size... My point is, this just seems complicated. A fresh reamer, and a straight start is all you need. I would recomend flood coolant, and lots of it. He should be able to feed the tailstock by pushing the whole assembly - cutting so little material. Stone a radius on the end of the flutes at the shank of the reamer to avoid gouges when removing the reamer from the tube. Stop the spindle before removing the reamer to clear the chips. Just simple first year apprentice bullshit really. Lem |
Lem, I'm probably just making it complicated due to my lack of machining experience.  Yeah, the guy is very experienced -- he's been a tool & die man for General Motors for over 30 years and also has a machine shop at his home. We never really discussed increasing the ID, as I figured .902" would work -- until I considered the magazine follower issue. The mag follower issue isn't much of a concern to me, as I want him to make me a new one anyway, because I'm trying to rake up enough US-made parts to be 922(r) compliant. Others have expressed interest in these tubes on another board, and I would just as soon not have to have new mag followers made for each one if I were to hook them up. |
Don't pay him much - that is a standard tube size that can be bought from any supplier. |
How about 0.035 wall tube? For this application, you should think about finding some 1020 or 1025 alloy at a race shop. You can also get a sheet metal fabricator to bend (roll) a piece up, or you could fab an aluminum tube yourself, but it will take some work and you will end up with some waste. If you want to go wild, get a piece of aluminum tube and chem mill the inside with muriatic acid - follow all the usual precautions and wear eye protection. |
Look an see if These Guys have any. |
Nope. For this application, the perfect size would be a wall thickness of .044", which results in an ID of .912". A .035" wall yields an ID of .930", which would be way too big. That's the delimma that the machinist and I have encountered -- we've found ID's of .902" (.049" wall) and .930" (.035" wall) for 1" tubes. One's too small and the other's too large. I guess my only choice is the .902" ID. 
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Nope. I already checked there yesterday. www.aircraftspruce.com/catalog/mepages/4130tubing_short.php |
Make a sleeve (or two one half perimeter sleeves) to install inside the 0.035 wall tube. Bond in with everyone's favorite (almost, not mine), JB Weld. For your application, you don't need 100% coverage of the tube interior to support the follower. Make yourself a mandrel from a 7/8 OD dowel, add a slot in the end, add two flappers of 40 grit paper, chuck it in your drill, and worry the ID of the 0.049 wall tube to size. Progressive polish the tube to finish. Buy an expansion reamer from any machine supply house. |
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cgi.ebay.com/1-x-058-wall-4130-Tube-Chrome-Moly-Round-Steel-Tubing_W0QQitemZ7615025216QQcategoryZ31490QQrdZ1QQcmdZViewItem I would give this stuff a try at $3.37 per foot. I doubt the 0.887 ID will be much of a problem. |