Question bout what steel to use

[DustyDave]

I need to machine some studs with custom threads and would like to end up with similar to grade 8 strength, free machining is desirable. Which steel do I want to use?
dUSTY

[10scDust]

I think you want the best of both worlds.
Free machining steels typically have lead (sulfur in some) added into the composition to make it easier on the cutter, machinery doing the cutting, chip length, etc.

Grade 8 bolts are of a high carbon content and generally heat treated for case hardening, while others use alloys added for the higher tensile strength.

I am by no means an expert here, but it seems maybe 4140 for the strength you seek. Surely a more knowledgeable person will give their recommendation.

[Dougtheinternetannoyance123]

I need to machine some studs with custom threads and would like to end up with similar to grade 8 strength, free machining is desirable. Which steel do I want to use?
dUSTY

I can ask my wife, She works at a high production machine shop, In the trades its called a "Screw shop" but few people outside the machinist world know what that means.

However, not being a smart ass here, But theres a LOT more to this. First, depends on what type of machining you are going to do? Lathe? Mill? Drill press or your Dewalt drill clamped in a vise? Diameter of the stock? As you probably know its easier to use existing bar stock, but depending on sizes you want makes this really variable. Hell,,, depending on what you want to do.. we could ship you some mill ends.
Depending on the tooling, machinery, size of the material and then your follow on resources predicates the best material. As she does not only scheduling but logistics lead, Sourcing materials right now is challenging. So whats ideal vs whats economical is variable. She has 20 years experience from tooling, to machine operator and now production mgmt.

Lastly, No doubt you are aware, but rolled threads are preferred than cut threads. And then,, how many of these bad boys do you want to do?

When planning a job, they have engineers that look at all these issues and in most cases depending on the customer needs they pick something that fits their production, and customer call outs.

*They had a raging debate a while back about cow tags. Machined parts for hanging a tag from a cows ear. The QA lead at the time was rejecting what was coming off the floor.. He didnt understand the customers issues. Finally got it sorted out that the tolerances were not that critical. Cow Bling.

In most cases you get soft material, and then heat treat. Depending on the issues, as noted it might be a surface heat treat or the entire thing. Gearbox parts for example have very hard surfaces but soft inside that absorbs shock and loads. What about fatigue life? Elasticity? Surface treatment? Are you going to leave a rough machined surface or do you want a near polished surface? Are you going to plate it? Cads a problem and about 20 different colors, Zinc is more economical but is softer. Nickel generally builds too much thickness and a PIA to work with often stripping mating fasteners.

They make a lot of firearms and sporting goods supplys,, All those carabiners Mt climbers use? Yeah..... better make sure they are engineered right.

Give me more details, or if you want a production quote, PM me direct.
heres a few pieces that they make,, Steel, copper,brass, even gold, and some plastics.

[JBinNC]

I think you want the best of both worlds.
Free machining steels typically have lead (sulfur in some) added into the composition to make it easier on the cutter, machinery doing the cutting, chip length, etc.

Grade 8 bolts are of a high carbon content and generally heat treated for case hardening, while others use alloys added for the higher tensile strength.

I am by no means an expert here, but it seems maybe 4140 for the strength you seek. Surely a more knowledgeable person will give their recommendation.

You mentioned both leaded steels and 4140 in this post. As it happens, there is a 41L40 leaded chromoly steel, and it can be had in a heat treated condition, 41L40 HT, also called 41L40 PH, which stands for pre-hardened.

Steels that are going to be through hardened have a medium to high carbon content. Steels that are going to be case hardened generally have a low carbon content, the casing process providing the carbon near the surface of the part for hardness. 8620 "stressproof" is one example of a very tough alloy that is intended to be case hardened.

D,
The 41L40 HT would be my choice for your studs, but be advised that the result will be less than Grade 8, and as mentioned above, rolled threads are stronger and a better choice than cut threads if a Grade 8 type stud is what you are after. But for your custom application, your homemade studs may be sufficient.

Jim

[DustyDave]

The Bonneyville Scout uses cylinders that are at least 78 years old and and I have some as old as 85 in my stash. I don't want to insert every hole. So I plan to single point oversize studs since it's going to be blown fuel. The original head bolts didn't have a head mark but spark test and feeling the stretch seemed to be about grade 5. There will be 14 each 7/16 studs in each engine, hopefully I will have a backup engine. The great majority can be turned out of 7/16 stock a few will probably have to come out of 1/2" stock. The length is still to be determined but probably 2.5 to 3". The heads are Fortrel HR an improved 7075 the lower surfaces are done but we are still arguing over the top. I really want to avoid heat treat if possible, this is a lobuck operation. The heads were a mill drop the only way I could afford them.
Dusty

[JBinNC]

The reason I suggested 4140 HT is that it is already heat treated, as opposed to the common annealed alloy. The leaded version will be even more free machining, but I think you will find that the straight HT will be less gummy and give a better finish than the annealed. It would probably be more than strong enough for your application.

Jim

[DustyDave]

I asked a friend and he said you dumbass just buy long grade 8 bolt and use the threads that are already there for the top. Saw it to length and cut your custom threads on the sawed off end. Never occurred to me.
Dusty

[farmall]

If rolling were critical some machine shops have thread rollers. Worth remembering if you need a batch.

[DustyDave]

If rolling were critical some machine shops have thread rollers. Worth remembering if you need a batch.

I think that single point thread IN GRAD8 will still be stronger than the threads in an 80 year old castings no matter how tight I fit them.
DUSTY

[Dougtheinternetannoyance123]

I think that single point thread IN GRAD8 will still be stronger than the threads in an 80 year old castings no matter how tight I fit them.
DUSTY

Maybe assuming they are the same pitch. I think Indian stuff was fairly standard but 80 years ago not everyone used the same standards. Also dont rule out the quality of vintage metals. Some are still around because they used quality materials by real craftsman. Technology has evolved... but not as much with quality.

I asked SWMBO, and her reply was : "most of the jobs we make studs for that require strength are made from S4140 most of them do also have HT though"

She went on to say they make parts for bolts and studs for a company that supplies assys and components to mostly offshore oil rigs (Certed) as well as industrial applications where the materials used have to meet pretty rigid standards.

If you wanted the heat treat instructions or details, can probably download and send them next week as they are on file for that material. Her shop works with several vendors. However using most of those metals in your application WILL require heat treat. Heres another detail you should know.
Those materials, depending on which one, will either shrink or expand post heat treat. So you machine to tolerances that will AFTER heat treat be the right size.

Thats the nice thing about tech data. Predictable outcomes and standardized results. And yes,, when running that material, Bar ends-mill stock they often have 6" to 12" scrap and they fill a very large roll off metals scrap bin every 2 weeks.

However you are right. Repurposing existing hardware WOULD be the easiest. I assumed you had already eliminated that choice. But again, if you CUT threads, those will be the weakest link in the chain.

[Dougtheinternetannoyance123]

Lastly 2 points. Might not be relevant to your application but worth knowing about for high performance regardless.

First, Its funny how some people get tunnel vision. If its not HD,Italian, German or British it does not exist outside your specific application. Waisted bolts and studs are well known for stretch. Many auto applications now use stretch bolts which are 1x use and then scrap. Especially Ford junk since they have a long history of head gasket problems unlike a Chevy which generally uses 5 evenly spaced bolts around a cyl.

But Norton people believe the world revolves around their Balloon knot so think they are pioneering the waisted bolts & studs

However the Norton folks have a LOT of problems with cyl head sealing and blowing gaskets so need all the help they can get. Several topics on other forums like its a new concept, but it does work.

See: https://www.accessnorton.com/NortonC...s-cases.24274/



As to using alternative alloys for stretch and hi-tensile this reply was to using Silicone Bronze alu-Bronze.

" Interesting idea. I think part of the reason you don't see them is that even high strength aluminum bronze fasteners are not as strong as typical steel head bolts, and certainly not up to the 160 - 170 ksi of the ARP stainless bolts or 8740 steel bolts. The highest strength aluminum bronze fasteners I've seen are in the 110 - 130 ksi range, and would probably have to be custom made to get sizes needed for our applications. That looks like a fairly expensive exercise. The material also has less fatigue resistance than most steel fastener alloys, although I don't know if that is as significant in our application. I haven't looked at its crack sensitivity compared to the steels we now use, but that's something you'd want to evaluate before trying them. Doesn't mean it couldn't be done, but it looks like maybe not enough benefit for the cost and effort.

The ideal material would seem to be something like Dilavar, the high expansion steel alloy that Porsche (and some Italian engine builders) used for some of it's race car cylinder studs. It has a thermal expansion rate right in the middle of the range for the common aluminum engine parts alloys. That was some time ago, and I don't know if you can still get fasteners made in it, or a similar alloy.

Regardless of the material used, a waisted design fastener is still superior in terms of consistent clamping force and fatigue life. That's why you see it used so much in high end engine fasteners like con rod bolts and head bolts and studs.

Ken (Ken is a retired mil-aerospace engineer, generally pretty knowledgeable)

But I have had a lot of problems with fasterners coming loose from expansion and contraction so will be making some custom top end bolts for some of my projects as well as case bolts as on certain ones, they just keep coming loose, (I safety wired them too)

But on some race engines, some just exceed the base materials. Especially with aluminum. Either custom cases ($$$$$) Or very complicated modifications. However when I was in the UK back in 1980s watched some various bikes "Sprinting" as they called it (Drag racing) and a bunch with turbos and superchargers including some Asian bikes.

But many used whats called a Head girdle. A steel frame and long studs top and bottom that clamped the head-cyl-case like a vise and without them they just couldnt handle the pressures.



Not seeing a lot of examples to link too online, But I have some older British and German magazines with a bunch of these race bikes in them. This looks like one of them on auction. Might be able to zoom in and see.
See: https://www.bonhams.com/auctions/14255/lot/514/