Thinning Rims - What's your method? No Lathe

[Hanzy4200]

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?

[Scrounge]

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"

[country gent]

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.

[rking22]

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!

[EDG]

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.

[brstevns]

I have been watching this, what do you consider a cheap lath?

[EDG]

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.


I have been watching this, what do you consider a cheap lath?

[country gent]

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

[ulav8r]

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

[Scrounge]

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.

[country gent]

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

[Three44s]

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

[rbuck351]

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.

[country gent]

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).

[Lionel Allen]

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.

[rbuck351]

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.

[Drm50]

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.

[rintinglen]

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.

[country gent]

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

[Scrounge]

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.

[rintinglen]

My drill press was purchased from Harbor Freight for $69.00. My file was maybe ten bucks. Takes a lot of "saving" to equal the difference between that and even the cheapest lathe, especially when the cost of tooling is considered.

[toot]

I also use a drill press and put a dowel of the tightest fit in the case mouth and chuck it up, and hold a 1 inch pine board about 6 inches in length on the left side to put presser o the case when i am filing. first a flat bastard then a smooth milled one. works for me every time.

[EDG]

When you get through all you have is a cheap drill press and used file.
If you know how to run a lathe you can actually make stuff (and money).


My drill press was purchased from Harbor Freight for $69.00. My file was maybe ten bucks. Takes a lot of "saving" to equal the difference between that and even the cheapest lathe, especially when the cost of tooling is considered.

[rking22]

I hear you about the lathe! I am getting ready to retire and lose access to the plant shop, looking at the 7x12 mini lathe right now. I did my 40-70SS on the drill press because it was there and I got it done in less time than driving back to work. I wanted to shoot the Sharps NOW, kinda like digging 3 post holes by hand instead of pulling the bush hog off the tractor and mounting the auger. Just “easier” to do it the hard way........:)

[EDG]

It is just the trade off between set up and run time. Sooner or later the real lathe catches up to your file and drill press.


I hear you about the lathe! I am getting ready to retire and lose access to the plant shop, looking at the 7x12 mini lathe right now. I did my 40-70SS on the drill press because it was there and I got it done in less time than driving back to work. I wanted to shoot the Sharps NOW, kinda like digging 3 post holes by hand instead of pulling the bush hog off the tractor and mounting the auger. Just “easier” to do it the hard way........:)

[barrabruce]

I just used a drill and a hacksaw blade.
Run a fine tooth hacksaw blade so the teeth are running running along the case into the rim.
That way you are not disturbing the primer pocket.
Works for 32-20 for 310 cadet cases anyway.
Even works with my new cordless drill.
O.k a bit slower and more trouble than a lathe but it still works!

[Jabber]

I just finished trimming a bunch of .405 winchester brass for my 40-70 sharpes. I mounted a v-block on my bench belt sander and sanded the rim to size. with primer pockets being now shallower I use pistol primers. Works really well.

[Drm50]

I have a big old South Bend lathe. I been getting close to pulling the trigger on one of those harbor freight $499 jobs but I keep hearing they are pure junk. I would dearly love to run into a jewelers lathe, cheap.

[Scrounge]

I have a big old South Bend lathe. I been getting close to pulling the trigger on one of those harbor freight $499 jobs but I keep hearing they are pure junk. I would dearly love to run into a jewelers lathe, cheap.

I've had mine since 2008. They're not pure junk. Older ones do often need a bit of TLC. Go to: https://groups.io/g/7x12MiniLathe and join up, see what the guys there are saying. Or https://gadgetbuilder.com/ or http://www.varmintal.com/alath.htm Varmint Al is a shooter & reloader. He does not think they're pure junk!

A few years ago I did find one Made-in-USA Mini-lathe similar in size to the 7x10. It was $10K. No way I could afford one. I've got well less than 10K in my entire shop. Even a 6" Atlas lathe is around a thousand dollars now. And there are people who say the same thing about the Atlas lathes, despite the fact that home workshops have been using the heck out of them since the 1930's. They've been out of business since the mid-80's, and there is a brisk market for them still. Look around hard, you can find one. I did, finally. After more than 35 years looking. Search "atlas lathe" on ebay, and see what they cost. And they're not exactly superior to the 7x mini-lathes. People who use lathes professionally call them "spaghetti lathes" because they're so flexible, related to a "real" lathe. Of course a "real" lathe weighs 10-20 times what an Atlas weighs. My 10x24 TH42 is listed at 267lbs. The baby lathe in my classroom is 2700lbs. My 7x10 is 115lbs of mostly cast iron. For it's size, it's sturdier and heavier than the Atlas lathes. Not as sturdy as the South Bend lathes, but those are not as sturdy as a Monarch, or even the Clausing Colchesters. If you want something that will sit on a desk or workbench, you need a smaller lathe. The 7x lathes are good lathes, if you realize their weaknesses, and compensate for them. Same as using a clapped out old South Bend. Smaller parts, or lighter cuts and slower feeds, and you'll get where you need to go. You could thin the rims on up to .50BMG rounds on a more-or-less stock 7x12, though 20mm might be a bit harder. I think I'd want a 7x16 if I were doing something like 30 or 40mm. ;)

If I decide I need them, I could make brass for a .32 Colt on my 7x10 from scratch. Or .44 Mag, .45-70 to 150, et cetera, without a lot of fancy tooling that I didn't make for myself. I will be thinning the bulge at the base on some swaged down .32 S&W brass I was given to finish the conversion to .32 Colt. Any troubles I have doing this are going to be because I'm not the greatest machinist in the world, rather than a problem with the lathe.

Micro-Lux has a 7x16 minilathe on sale about $1100, Little Machine Shop has one for $1250 that's probably a little better package, or you can drop into the $600 range for the 7x12 from Harbor Freight. Most decent rifles cost more. Unless you're already a machinist you'll need to spend some time learning how to use it, but it's doable. If I can, you can. Ever build a kit rifle or pistol? Think of the lower end mini-lathes as a kit lathe, and it will make a bit more sense, maybe. You might have to do a couple of things to it to get it the way you want it, but mine worked better than I could right out of the box. I'm finally trained enough to get good work out of it because I know better what I'm doing with the measuring tools I have now.

[Drm50]

I just finished trimming a bunch of .405 winchester brass for my 40-70 sharpes. I mounted a v-block on my bench belt sander and sanded the rim to size. with primer pockets being now shallower I use pistol primers. Works really well.

I would have never though of thinning from the outside. When I have such work to do on cases if there is just a few I’ll turn them in drill press with file. If there is a lot of them I’ll make up a jig and use a parting tool anchored to drill press vise/ table to reduce from back of rim.