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Thread: Thinning Rims - What's your method? No Lathe

  1. #1
    Boolit Master

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    Thinning Rims - What's your method? No Lathe

    I am in the process of forming 8MM Nambu brass from .40 S&W. After much trial and error, and the help of a good member here (Thanks garandsrus!), I have formed, trimmed cases. The last hurdle is the case head rim. They are about double the thickness of a factory 8MM, and as such the extractor cant grip them. Is there a better answer than using a hand file?

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    Boolit Master
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    Quote Originally Posted by Hanzy4200 View Post
    I am in the process of forming 8MM Nambu brass from .40 S&W. After much trial and error, and the help of a good member here (Thanks garandsrus!), I have formed, trimmed cases. The last hurdle is the case head rim. They are about double the thickness of a factory 8MM, and as such the extractor cant grip them. Is there a better answer than using a hand file?
    What do you have to work with? Cordless or corded drill? Drill press? Only hand tools? You can make a lathe fairly easily if you have a drill or drill press, or just use them as is. Make a mandrel to hold the shell, put it in the chuck of a drill, and put the shell on it. Use a file or graver to thin the base. Or you could lay a file flat on a table, and stroke the shell across it until you get where you want.


    http://www.lathes.co.uk/fonly/ for "if I only had a lathe"

  3. #3
    Boolit Grand Master

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    with just hand tools a simple wood clamp to hold the cases in a vise and fine file to cut down. Use 2 pieces of hard wood ( aluminum brass or steel would be better if you have a drill press). clamp the 2 pieces together and dill 2 dowel holes then in the center of them dill a hole thru size of case body or slightly bigger then epoxy bed this to a case. clamp cases in this in a vise and file rims to desired thickness. If you have a drill press the stop can be set and a very short flat ground drill used to cut them lightly.
    You actually want to thin from front of rim so the primer pocket dosnt need re cut after wards. This is easiest done in a lathe. and is almost impossible in a drill press or by hand.If made right your clamp blocks will show how much to remove and act as a gauge with a layer of tape on the top.

  4. #4
    Boolit Master
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    I have thinned rims on 40-70 brass in a drill press. Unless you want to recur the primer pocket depth you should trim from the front. I made a plug, slip fit to the case mouth to prevent deforming with the chuck. You will need a safe edge file, or just grind a safe edge on one you have with a belt sander. Chuck the case with the plug in the drill press, then use the file on the spinning case rim. The smooth edge of the file will not cut the case dia while the teeth remove the rim thickness using the case body as a guide. “Redneck lathe” style. You can use calipers or make yourself a little gage to check the rim thickness as you go. After a few you get pretty good at judging when you are close. Be CAREFUL, you will be working close to the spinning chuck, no gloves, loose clothes or rings!
    “You don’t practice until you get it right. You practice until you can’t get it wrong.” Jason Elam, All-Pro kicker, Denver Broncos

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    Boolit Master
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    Some times you have to invest in the right piece of capital equipment to do a job or it simply cannot get done by any shade tree process.
    A cheap lathe will do a lot of things that you cannot do conveniently by any other means.
    EDG

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    Boolit Master brstevns's Avatar
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    I have been watching this, what do you consider a cheap lath?

  7. #7
    Boolit Master
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    Lathes are kind of like airplanes. They make doing a lot of things you cannot do otherwise very convenient.
    If you can not afford it or chose not to buy one you just do without.
    Most folks can afford a lathe they just chose to do without because they cannot operate one well enough to make good use of it.
    It appears the minimum cost for a lathe that is useful is about $2000 or about 2X one of your Trump covid checks.

    Quote Originally Posted by brstevns View Post
    I have been watching this, what do you consider a cheap lath?
    EDG

  8. #8
    Boolit Grand Master

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    For this job the cheap harbor freights will do great. I bought a 7 X 12 a few years ago on sale for around $500 but there is a smaller model also. No read outs but variable speed and easy to operate. Also old jeweler lathes and small bench tops with 4" swings and 8-10" beds are available check out little machine shop on the web. For most case work you dont want or need power feed or threading. These machines can go for about the price of a decent drill press. Some are small enough and light enough to pick up and store on a shelf when not in use. The harbor freights for this are nice as they have 0-2500 rpm spindles, are small light and are easy to work with. The 3 jaw chuck for my 14 x 40 nardini with D 6 spindle weighs and costs more than the whole HF lathe

  9. #9
    Boolit Master

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    The Taig lathe is probably the lowest price new lathe that would be suitable for this type of work on cases.

    http://www.cartertools.com/specific.html
    Spell check doesn't work in Chrome, so if something is spelled wrong, it's just a typo that I missed.

  10. #10
    Boolit Master
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    Quote Originally Posted by ulav8r View Post
    The Taig lathe is probably the lowest price new lathe that would be suitable for this type of work on cases.

    http://www.cartertools.com/specific.html
    The Taig lathes are cheaper than the HF lathes mostly because they don't come with a chuck, motor or tailstock. Honestly, they're probably better made, but they're mostly aluminum, so not as sturdy or vibration resistant as the HF lathes. I investigated the heck out of them in the early part of this century, and wound up buying the HF. If you know you will never need to do larger parts, a Taig would be good. You will need the chuck, tailstock and motor, so you're going to spend at least another couple or three hundred bucks, not counting tooling. If you know you want to do larger parts someday, the HF will be better. Though if you're going with the HF, get the 7x12, not the 7x10. If you really want a 7x10 mine could be for sale or trade. Without most of the extra tooling! One of the things that affected my purchase was the plan to upgrade to a larger lathe when/if I could at a later date. I found an Atlas TH42 10x24 lathe in 2015, and much of the 7x lathe tooling fits it. I still have the small lathe because they are handy for doing small things. I've got the HF fitted with a ER32 collet chuck, and it came with a 3" 3-jaw chuck. For a lot of cartridge work, the ER32 collet system would be about perfect. Also things like a 1911 Colt firing pin, and similar small parts. I know a guy who made a 9mm Lugar barrel on a Unimat lathe, which is closer to the Taig than the HF. The HF would let you make a much longer Lugar barrel, for example. Or a barrel for one of the Dan Wesson revolvers. Taig is going to be hard to put parts through the spindle bore, since it's 10mm, IIRC. The HF has a 19mm/3/4" bore, and mine has been reamed out to 13/16". I still have the reamer if someone wants to ream theirs out. You lose a little bit of the #3 Morse taper in the spindle, but gain the ability to put larger objects through the headstock for turning. That's handy when you need to make several parts to a specific length.

    A Taig lathe is better than no lathe, and you could get the parts a few at a time. You can rig up pulleys and drive it from an improvised motor setup slower or cheaper than the factory job. Though you might find you want another larger lathe real quick, too. I know, I've been there with the 7x10. And the 10x24. And I'm sure I'll do the same when I get the 10x33 South Bend going, one of these days. Thing is, a lathe is really handy for a guy who likes guns. Likes to shoot guns. Likes to reload for guns.

    This is a guy you want to learn some stuff from if you get any sort of lathe, btw: https://www.youtube.com/user/mrpete222 He's a retired shop teacher.

  11. #11
    Boolit Grand Master

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    One thing I did was I bought a straight shank er 32 collet set up these collets have more range than a 5c so most cases can be held with them or you can block one open with shims and bore to desired size holds easier than a pilot usually. For case and most gun work with these little lathes a good set of collets is better than the chuck is. The biggest draw back too the mini lathes is the small almost non existent spindle bore. I also recommend the 12" beds or longer on the 10" a drill chuck takes up 3" a drill 3-5 any out of the chuck and your out of room.

    But for reworking cases these little machines wont wear you out near as fast moving tail stocks or feeding tooling like a bigger machine will With the er 32 collets and stem modified for a stop you can run pretty quick and accurate. The one thing these machines should have is a carriage stop and lock

  12. #12
    Boolit Master
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    This is just a thought:

    I have been working a bunch of mil surp 5.56 recently. After a trip on the RCBS press mounted swagger, I run the brass on a Wilson trimmer.

    In checking the length, I run into a number of cases with a sharp ridge raised circle around the mouth of the primer pocket. I have used a carbide twist drill bit to clean off that circular ridge but yesterday evening I just swapped ends on the case/case holder and cranked a few turns on the trimmer.

    The flat cutter of the Wilson trimmer cut ridge right off the case head. If I went farther, I could cut away the head stamp. The Wilson is cutting accurately because the ridge is a smaller diameter than the case back stop center but I want that ridge gone because it will affect chambering and even cutting primer pockets to a uniform depth.

    Could this feasibly thin a rim from the head stamp forward to the OPs taste?

    Three44s
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    “There is more to this than dumping lead in a hole.”

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    Boolit Master
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    A HF 7x14 is about the handiest piece of equipment on my reloading bench after the loading presses and costs about what a new rifle costs.

  14. #14
    Boolit Grand Master

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    It will thin the rims accurately but primer pockets will be way shallow and deepening them that much will thin the case head and possibly enlarge the flash hole. (the inside of the case head isn't normally flat but radiused so if it gets to there flash holes will be larger).

  15. #15
    Boolit Mold
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    I thinned a bunch of 45 Schoefield rims in a little drill press last winter. Just chucked them and spun them as slow as the press was set for. Didn't take too many hours to do all 100 pieces, but then I didn't do them all in one session.

    Had to be careful how tight I chucked them. No boolit, just a big gaping case mouth that deformed rather easily. A couple of new 8" triangular files and I was off to the races.

    I kept the firearm I was going to use these cases in handy to use as my go/no go guage.

  16. #16
    Boolit Master
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    If your time has any monetary value, get the 7x14 mini lathe. HF, Grizzly and others sell the same lathe (different colors). You will find more uses for this than you can even think of. A short list, sizer dies, case trimming, 22lr derimming and swaging dies, thinning rims from either end, M dies, gas check makers, chamber adapters, barrel liners and the list is endless. If I didn't have 3 lathes already I would figure out how to get at least one and the 7x14 mini has a lot of good features for not a whole lot of money.

  17. #17
    Boolit Master Drm50's Avatar
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    It would have been easier to thin rims before you formed Brass. Chuck up in drill press and use file on them. You can do it in a hand drill if you clamp it down. I’ve seen guys use big hose clamps for this. I built me a mini lathe just for cases and such. Mounted sewing machine motor on Aluminum channel, and have it wired through foot pedal. I’ve made all kinds of attachments for it. Made tail stock for it, all made from junk parts. I can’t do hard metal but brass, alum, plastic and wood is no problem. I used it last to thin rims on 38Super that I was loading as 9mm Largo and Banyard. I was afraid of breaking extractors of old generation pistols. The Spanish Destroyer carbine and Star B will work with 38acp or 38Super but still puts undue strain on them.

  18. #18
    Boolit Grand Master
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    If you don’t have many to do, say 100 tops, a drill press and a file will get you there, for a lot less than the price of a lathe. While a lathe is a neat tool to have, one worth having is pretty darned expensive just to use for making thinner rims.
    I thinned 45 colt brass Rims in this fashion to make 455 brass for an old S&W hand ejector that I used to have. Do work from the front and don’t be in a hurry.
    _________________________________________________It's not that I can't spell: it is that I can't type.

  19. #19
    Boolit Grand Master

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    One thing I find interesting is a guy will spend more for a progressive press or even some single stations then balks at the price of a cheap lathe. That makes modifying and reworking so much easier and handier.

    On sale the mini lathes can be had for around 500.00 They only weigh 70-80 lbs can be stored on a shelf when not in use, and when needed set on the bench leveled and used. 110 outlet and standard plug. They usually come with enough tooling to get started and for most reloading / case mods tooling can be made as needed on the machine

  20. #20
    Boolit Master
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    Quote Originally Posted by rintinglen View Post
    If you don’t have many to do, say 100 tops, a drill press and a file will get you there, for a lot less than the price of a lathe. While a lathe is a neat tool to have, one worth having is pretty darned expensive just to use for making thinner rims.
    I thinned 45 colt brass Rims in this fashion to make 455 brass for an old S&W hand ejector that I used to have. Do work from the front and don’t be in a hurry.
    I've used large (relative to a 7x14, anyway) industrial lathes and smaller ones, as well. Within it's envelope, it's as worthwhile as the 15" Clausing Colchester lathes in my school. In careful hands, it is just as accurate, and just as capable. I looked for a 13" CC lathe, as my class has one of those, too, and I really liked it. For my purposes, it was a lot lighter also, at only 2700lbs. The 15" CC is 3800lbs. A 7x14 is around 125lbs. Weight is not the only criterion, but it is one. Price is another. The fanciest 7x14 runs well under $2k. I found a very used 13" CC lathe, vintage 1969 a few years ago. It was $6900 used. Most likely worth every penny, too. A new Monarch 10EE (a very very nice lathe!) is about $100K. If I hadn't spent all that time trying to become a teacher, I could have bought one. The modern South Bend lathes run upwards of $7500 (recently on sale) to $10K for the new version of the Heavy 10L. Those bigger lathes will do good work more easily, but you pay for that capablity up front in hard cash, or do without. If you plan on being a professional machinist, go with the much more expensive lathe. It will pay. For a hobbiest, doing machine work to support another hobby, you do not need a $10K lathe, though it would sure be nice.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check