Member postings for Chris Hunter

Just to round this off in case anyone comes across it in future it seems that EN-31 is a good choice for my application and is used for injection moulding ejector pins

Again, thanks for the replies, I know that solutionising is the interesting bit but I was asking what would be the best material for to something akin to a cold chisel, i.e.something that is going to be bit with a hammer against a hard surface and is as tough as possible.

I guess I was hoping that someone would suggest a steel grade such as EN19 or EN24 or know what things like SDS drill bits are made from. I only mentioned the 8mm to avoid a lot of replies telling me the best material is a cold chisel or some engineering steel alloy that is not available in 8mm.

As I said for this application 8mm round section is the only option.

And just out of interest here is one that failed, as you can hopefully see a piece has sheered off the business end and the other end is bent

Edited By Chris Hunter on 23/07/2022 13:10:18

Just to add that I have got a decent propane torch and what I have been doing is setting up a firebrick nest on top of the gas BBQ and letting everything get up to about 150-200c then bringing it up to the curie point with the propane torch and quenching. After quenching I test with a file which usually just skates over so I am fairly convinced I am getting the rod pretty hard. As I said I am tempering in a domestic oven so the whole rod is tempered, obviously the oven temperature setting might be off but I do have a fairly new, decent quality toaster oven with a digital temperature setting. I know this might not be accurate but its probably as good as anything else without going to much expense.

Thanks for the replies, I had considered something like a screwdriver repurposed, what I hadn't though of was welding/brazing different materials together. As I briefly mentioned in my second post the slender rod screws into a holder which is the part that gets hit with a hammer, so may be a screw driver of the right diameter with a threaded rod welded on one end and a hardened piece on the other is the way to go.

I suppose the question there is around whether it is possible to weld a tool steel tip on to the screwdriver and then harden it without affecting the strength of the screwdriver shaft too much. I'm pretty busy for the next few weeks but I'll do some tests when I get chance. It may be that a chrome vanadium screwdriver would be hard enough anyway for the intended application.

I'm using heat and hope I don't do a lot of heat treatment so alternatives aren't really cost effective. And yes, getting consistent temperature over 250mm with a blow torch is challenging. Suggestions for low cost better ways of consistent heating most welcome. I use the domestic oven for tempering.

The 8mm over 250mm is what it is, it screws into a larger diameter holder.

I want to make what is essentially an 8mm diameter cold chisel about 250mm long. It needs to be hard but also resist bending when struck with a hammer. It needs to be circular in cross section so using something like and old drill bit is not an option.

I have tried silver steel tempered at a range of different temperatures but it either breaks because it is too hard or bends or both.

Is there a better grade of steel for an application like this? And ideally available in 8mm dia stock, I don't have turning facilities and the diameter needs to be very close to 8mm.

p.s. I know this post will raise questions about why and what for but I really don't want to get into that as it will just raise other concerns. I am certain that this is what I need there is no other option but a circular 8mm hard resilient rod

Thanks Brian, always good to get the view of someone with experience.

Thanks for the replies.

Jeff - I think you have hit the nail on the head (excuse the pun), I was over-complicating it, I guess if I heat and hammer some flat stock along it's width it will get "fatter", providing a basic taper. I'm fairly confident that I can make a jig to run the resulting bar across the bench grinder to improve the taper.

Hi,

first post so I hope this is in the right section and you will offer some advice even though this isn't strictly Model Engineering.

I want to make some sets of Plug and Feathers for splitting rock -

I want these to fit a 12mm hole, for the plug (wedge) I was planning on grinding down some cheap 12mm cold chisels but I am unsure as to how to make the feathers?

The few ideas I've had are

• hand saw them by cutting some round bar at an angle so that I get two feathers from one cut
• use something like a slitting saw to do the same thing with less elbow grease
• forge them - but then I presumably need some sort of tapered former to hammer them into
• just grind some round bar down - seems wasteful

Are any of these ideas practical? Is there a better way?