What steel to use for expander?

[Lance Boyle]

I have a set of .38-55 rcbs cowboy dies. Neither expander is large enough to accommodate my 0.383 bullet.

I am a new lathe owner and am considering turning and threading a custom expander.

What steel is appropriate? A2 tool steel? Stainless? Should I flame heat treat it?


Edited I posted in gunsmithing as I am likely to find more lathe experience here than in the reloading equipment forum.

[Kenstone]

You can use low carbon steel and case harden it with this stuff:
https://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/color-case-hardening/surface-hardening-compound-sku083000033-27119-52952.aspx?rrec=true
I've made small wood gouges/scrapers out of cut nails and used that stuff...
It's what I'd do,
:mrgreen:

[redneck1]

A2 would work just fine if you already have it , if you need to buy material I would get 02 instead .
The air hardening tool steel can work harden fairly easy if you aren't careful . The oil hardening is much more beginner friendly , plus it seems to give a very slightly better surface finish .

Both would likely outlive you without hardening

[country gent]

I have turned up expanders from 4140 pre hard, A6, o1, S7, Allen cap screws, and made one with a carbide pin soldered in. All worked well even cold roll left soft will last a long time here. I find finish is more important than hardness. A good smooth polished surface will hold up a long time and reduces friction also.

If you want to harden it then leave it .010-.015 large with a false center on the end so it can be finished after hardening. use carbide to turn to +.002 and finish with fine sand papers to a chrome like finish. When finished cut off the false center.

[Nobade]

I use a lot of 1144 for that. Cheap, machines well, and easy to harden if you feel the need. Those expanders don't need to be hard though, they last a long time anyway.

[Lance Boyle]

Thanks guys.

Finish on the surface with stainless I thought might be a bit tougher to get smooth.

False center. Good idea.

I have been practicing threading on scraps just to learn the techniques better. I last did lathe operations in the 80’s.

Turning on unknown mystery scraps is a bit hit and miss on finish looking for the right speed and feed.

I was wondering if hardening was necessary. It’s brass it’s contacting after all.

You have been most helpful.

[Reverend Recoil]

I have turned similar parts from automotive cylinder head bolts. I do no know for certain of the alloy of manufacture but they are strong, tough, wear resistant, and cost nothing.

[Lance Boyle]

:kidding:
And if used they’re heat treated.......a lot.

I am prone to recycle bits myself.

[Chill Wills]

Nobade is giving you good advice.
You don't have to over think or engineer this. Mild steel will outlast us. I made a 0.409" expander about 20,000 - 24,000 rounds ago from 12L14 and it is still giving the exact same diameter necks as the day I made it.
The use of hex stock makes up a nice nut on top that you do not need to knurl like round stock needs.
227388227389227390

[country gent]

For the easiest turning a false center on each end, this allows for the pin to be turned between centers with a small lathe dog. The expander leads and flare section along with the threads and head can be turned in one setup start to finish. For small parts we had the welder tig weld a small dia rod to the head for a dog. Get the lather running straight and turn the head dia then the thread dia here you can thread now or wait to thread after other dias are done. turn expander end and belling angle if one is desired. You can also chuck round stock long and do this. One trick when turning the expander end is to use HSS cobalt tool bit and grind it with the front angle at the angle you want the bell. Simply turn with this tool to length the angle is formed as the part is cut and a perfect blend from expander to bell is achieved.

[Lance Boyle]

I am taking all these in. The experience shown certainly kickstarts my thinking like a you put a jato bottle on my head. Even carpentry i stare at things a while. *(JATO jet assisted take off)

I measured my A2 round stock is too thin. So picking up some hex stock is simple. I saw some at fasten all, they’re pricey but I drive by several times a week.

[Lance Boyle]

Nobade is giving you good advice.
You don't have to over think or engineer this. Mild steel will outlast us. I made a 0.409" expander about 20,000 - 24,000 rounds ago from 12L14 and it is still giving the exact same diameter necks as the day I made it.
The use of hex stock makes up a nice nut on top that you do not need to knurl like round stock needs.
227388227389227390


Ok I am convinced heat treating is excessive for the job at hand. I wasn’t sure. I don’t know all that I don’t know!

[Lance Boyle]

I have regular Hss tool blanks. I have ground one cutting tool so far. It wasn’t too hard. I also have 1/2” carbide Chinese set with replaceable triangle 60 degree bits.

Grinding a cutter with the bell angle leading edge is a doable project.

[deltaenterprizes]

I have used grade 8 bolts of the proper thread, 9/16-18 I have think it is to make expanders.

[country gent]

Another nice touch on a expander bell stem is a witness lone on the top. this allows you to see and count revolutions easily when adjusting. if 16 threads per inch the expander moves .060 per revolution. The mark makes seeing this easier

[country gent]

Grade 8 bolts ae good material as are allen head bolts. I have used allen set screws or odd projects but most of these require carbide to cut. Hex stock is quick and easy to machine and gives a good surface to hold on to. The other big thing is to use you file, break all the sharp edges and remove burrs from the piece.

[JSH]

I will second 12L14.

Odds and ends of scrap are ok for some things and practice. But I prefer a known alloy for things I deem important and don't want to have to do again.

I also had not messed with a lathe since the 80's. Messed around around trying to thread on some unknown round stock. Threads were ****. I did a whole lot of checking and measuring(lots of time), cut again on the same piece of scrap stock, same result. Went to a piece of known alloy,mproblem solved.

[hpbear101]

I made some out of grade 8 bolts for my "M" die. I put a nut with an Allen lock screw on it that way I can use the same die body with several different expanders (also do the same for compression dies).

[Lance Boyle]

Great thoughts. I have done some similar little projects with other stuff. Use a bearing collar with the grub screw replaced with a cap head screw with the tip turned down for a sight pusher.

[Lance Boyle]

Another nice touch on a expander bell stem is a witness lone on the top. this allows you to see and count revolutions easily when adjusting. if 16 threads per inch the expander moves .060 per revolution. The mark makes seeing this easier

I do this with a paint marker on my dies. A yellow stripe on the side to a reference mark on the press. Mostly for accidental loosening and loss of adjustment.

[55fairlane]

Shoulder bolts are good tough steel, and come hardened.....not to hard, HSS will machine it......machine it up, and use as is

[samari46]

I used some old grade 8 bolts that I had found. Machined a couple matching nuts so would butt up against the chuck without slipping. Used a center drill for the ball bearing center I had for my ancient 6" craftsman lathe. Cut with regular HSS and left slightly oversized and used various grades of silicon carbide paper to get where I wanted them at. Same size as the threads on a Lyman M die. Frank

[Whiterabbit]

I used a .5" stainless rod. Turned down, threaded one end to fit the die, GTG. My cartridge was 510 wells though, so it didn't take much material removal...

Polishing is fairly quick work on a lathe when you use the right tools to make the cut.

[EDG]

Just use a grade 8 socket cap screw.
It can be easily machined but is tough enough fo any job.

If you prefer to buy out right Track of the Wolf and Buffalo arms sell custom expanders.

[beemer]

I made an expander for the same set for a buddy. Nothing special, just a good bolt with the right threads. Leave oversize and polish. I cut the head off and cut a slot for a screwdriver.

He ended up with a .383 bullet also, if I remember correctly his expander ended up at just a touch over .381. We lapped the mold also, if it had been any larger it would have given trouble chambering. His bullet is a slip fit in the fired case. He sizes just enough to let the expander slip in the case.

[Lance Boyle]

Just use a grade 8 socket cap screw.
It can be easily machined but is tough enough fo any job.

If you prefer to buy out right Track of the Wolf and Buffalo arms sell custom expanders.


Re buying it , well that might make good sense but I got the machine and the little job.

I will do this ��. Thank you for the ideas.

If I was in a rush I would just grab a cap bolt but I need to practice my threading on the lathe too.

[Lance Boyle]

I made an expander for the same set for a buddy. Nothing special, just a good bolt with the right threads. Leave oversize and polish. I cut the head off and cut a slot for a screwdriver.

He ended up with a .383 bullet also, if I remember correctly his expander ended up at just a touch over .381. We lapped the mold also, if it had been any larger it would have given trouble chambering. His bullet is a slip fit in the fired case. He sizes just enough to let the expander slip in the case.


Thanks for your diameter comment. I was guessing two thou under bullet dia. What I was going to do was measure the big one and extrapolate up. I seem to recall it’s nominally a 0.379”.

[country gent]

A better more "fool proof" way is turn expander to bullet dia maybe bullet dia +1 and do a few cases with it checking for fit both the bullets and in the firearm. Polish down .001 to the fit you want, this will allow for any spring back. and its way easier to polish down size on a dia than back up. This way the one expander is finished to size and less likely to have to start over

[indian joe]

I have a set of .38-55 rcbs cowboy dies. Neither expander is large enough to accommodate my 0.383 bullet.

I am a new lathe owner and am considering turning and threading a custom expander.

What steel is appropriate? A2 tool steel? Stainless? Should I flame heat treat it?


Edited I posted in gunsmithing as I am likely to find more lathe experience here than in the reloading equipment forum.

anything (steel) at all will do but you need a polish finish on it and take account of the polishing in your measurements.

[hermans]

Had two expander plugs made for my 45 and 9mm setups in my Dillon 550. The material was 316 Stainless Steel. Have used both for a few years now, still the same measurements on the plugs, and my ammo works perfectly, not down sizing my boolits any more.

[Lance Boyle]

Thanks. I found a 3/4” o1 drill rod at Fastenal. Yes they’re expensive there but I think I got a ok deal. The counter lady told be it’s regularly $36 but she could discount it to commercial account level and said $28. Me: ummmm the price tag on the rack with the correct item number says $18 and change. I guess the floor people didn’t catch up with the computer people. We both agreed with state pricing laws.

She made a phone call to over ride the computer price locks and sold it to me for the rack price. Nice lady agreed with me about state pricing laws, first time in 50 years I ever pressed, however slightly, that issue.

[Willbird]

I bought a new Grizzly lathe, it came with these tools included, they really work nice and the inserts are not terribly expensive. Knowing how to grind a HSS tool bit is a good thing too, they work great for a lot of things as long as we are not in a big hurry to get done :-).

http://www.grizzly.com/products/Lathe-Tool-Holder-Right-Hand/G7028

Here is the catalog page that shows the inserts too.

http://www.grizzly.com/catalog/2018/main/648?p=648

Lots of industrial inserted carbide tools are negative rake and do not work their best in a small lathe, these work really nice. Kind of sucks they are closing them out.

As for steel if you look around Ebay you can find "drops" or "bar ends" of 12L14...it is a leaded free machining steel that turns really nice, and is a good steel for a lot of garden variety stuff. For things like expanders and the like I keep some O1 drill rod around. it is decent as is for some things, and pretty easily heat treated and tempered if you want something hardened.

Bill

[Willbird]

Here is another option here if Grizzly does away with the tools I have not.

https://www.latheinserts.com/1-2-HOBBY-LATHE-KIT-500-Lathe-kit.htm

The inserts are a lot more expensive, and only have 2 corners instead of the 3 the grizzly offer.

https://www.latheinserts.com/CCMT-3251-CVD-COATED-INSERT-FOR-STEEL-STAINLESS-CCMT-3251-CVD-insert.htm

Cheaper on Amazon

http://a.co/d/4QfdCD6

holder and inserts on ebay for $24 shipped.

[gishooter]

"I found a 3/4” o1 drill rod at Fastenal. Yes they’re expensive there but I think I got a ok deal."
I buy a lot of stock from speedy metals. http://www.speedymetals.com

KBC tools also sells drill rod in O-1 & W-1. On sale frequently. And low shipping. Check out the current sales flyer. I usually buy from them. https://www.kbctools.com

[country gent]

For Small projects check out online metals they sell by the foot many different materials brass copper steels tool steels titanium plastics in various shapes and sizes. Another is to become friends with the local machine shops they throw out a lot of small lengths that are still useable for projects

[Shopdog]

I will add,whatever steel you use(O1 here),since you're setting up to make them.....uhh,make several. That way,you can do side by side comparison and,you may have more than one rig in the same chambering?

[Lance Boyle]

Good idea. I have a 36” rod. Should be able to get at least two usable ones. :kidding:

I will be in the shop today. It’s raining and my day off.

[samari46]

While I mentioned using grade 8 bolts for making expanders, I have also made them from grade 8 threaded rod. The few remaining pieces I have were 36" long and can easily be cut with a hacksaw. I normally cut them to about 3" or maybe 1/2" longer. I stick each end in the lathe one at a time and face each end off then bevel then so as not to get caught by the odd section of thread that always remains. The British do their cut ends in "Higby" fashion which is the rounding of the flat face sort of like a dome. I took two 9/16and whatever thread nuts and face off each side for a total of 4 sides. The two nuts and their flat faces seem to do a better job of keeping the threaded rod from migrating in the chuck. I but the buts against the chuck jaws and then center drill the working end and then proceed to machine away anything that doesn't look like an expander. First cuts to get through the hard outer skin and after that they do machine easier. get it to where you want it plus about 2-3 thousandths. Use some silicon carbide paper to make it smaller and polish. When done flat face a couple or two 9/16 nits as they serve to lock the homemade expander in place. By the way grade 8 bolts or threaded rod isn't the only metal to use. Good old screw machine stock in the proper thread will also work. Best part none of these have to be hardened. Chances are they will outlive you. I used kasenit but they don't make it anymore. Cherry red as sold by Brownells will also work, So if you feel the need go ahead and harden them. And if you want high speed steel will work fine just hone the bit before using. Frank

[Lance Boyle]

:kidding:Thanks for all your help and ideas. I better not retire and take up gunsmithing just yet. Unless I can get hourly rates.

After the usual couple oopses I got one that will work.

First one I turned down cutting away from the head stock. All spiffy, put knurling (weak) on the top, then changed gears threaded it. Looked great, smooth threads, held up factory part to compare thread depths,.......forgot to select to the headstock threading. Anyone need a left hand threaded expander?


Did a second one, all was looking good, halfway through the threading operation and my nice threads suddenly looked like a plow turning over field. My threader tip chipped. I tried to change the insert but the the screw buggered and I tried drilling it out but couldn’t get more than the head out. Grabbed the threader from my little 1/4 set but couldn’t get the point indexed the same to salvage the threads.

Third one is the charm. (Mostly, while it goes in the die smooth and straight, I pulled the set up before checking the little lock nut. The nut is too snug. I will have to run a tap through that.) I was impressed with my concentricity, no wobble on the expander tip while threading in the die, must have left the threads a bit too proud over thread specs. Of course my machinery handbook showed up in the mail later

I am getting a .382” case mouth with a slight bell. This should work.

My hat is off to you guys who do this for a living, My feet are sore as hell from standing in front of the machine for the better part of two days.


Thanks again for your tips, wisdom, good ideas and just being here.

Warm regards

[indian joe]

:kidding:Thanks for all your help and ideas.

My hat is off to you guys who do this for a living, My feet are sore as hell from standing in front of the machine for the better part of two days.


Thanks again for your tips, wisdom, good ideas and just being here.

Warm regards

Get some rubber matting to stand on - old mine conveyor belt is good - a couple layers of yoga mat - you can even buy stuff in the home depot type stores - I like conveyor matt x 2 layers - its heavy enough to stay put and a smooth surface so If you drop a small screw or such it doesnt vanish into the matt - long sessions at the lathe will kill you if its on bare concrete

[Lance Boyle]

Yep bare concrete, 5” with rebar. It didn’t flex much.

I will see if I can grab some scrap belt. I actually have to talk to the quarry guys for some gravel.

Even more good wisdom.

[country gent]

You will need a special set of mics to measure threads , some what expensive and a pain to set up and use as they are only good for a certain range of pitches. Mitoyo made a set o-1 with interchangeable anvils. You can use thread wires 3 wires of a set dia and a chart with the constant to convert. Wire sets are cheaper but require some math and coordination to use. holding three wires 2 in bottom threads 1 in top of threads takes some practice. Unless truly needed we used wires and measured the matching part or existing part. Made the new thread the same.

We did a lot sitting on a tall stool. Not really sitting but a sort of propped up standing. Feet were on the floor and butt was on the stool sort of leaning against it . Mills Shapers grinders we sat and ran them. ( One young Female apprentice had a box to stand on so she could reach the bridgeports head and on the big lathes see over the tool post). The last shop I worked in had wood block floors and were much easier to stand on. We used metal belting in one shop rubber mats are comfortable but can snag feet up when lifting or moving.

[Lance Boyle]

I know that test fitting in something, like in a stock nut, is a hack and liable to be off spec, like it was.

I had my machinist friend demonstrate the thread measuring wires in his shop. I have not picked up a set yet.

I burned myself there, I backed away the compound and the live center and was test fitting the die body. I completely over looked the little lock ring that ended up not fitting.

Learning curve!

My set up was good practice for setting up barrels when I get appropriate experience. I used the four jaw chuck, the live center, and used the spider screws on the spindle’s left. Dialed in all three to indicating less than a thousandth. My gunsmith friend, where I used to live, taught me how he set up through the headstock with a four jaw for barrel work on his old Sheldon.

My feet and back are mostly better today but I need a pad for sure.

Ps the box step isn’t a bad idea. The grizzly lathe stand on my leveling feet is a touch tall to see around the tool post. I am only 5’3”.


ETA on the plus side I am happy to not be able to see any runout when threading the expander into the die, straight and no excessive slop. My factory expander stems have enough slop to wobble and can be locked off center if you don’t set up with due care.