Cutting a wedge

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?

Hello Chris

Welcome to the forum.

You may be on the right track grinding down some cheap? chisels for the wedge assuming they are made from a tougher grade of steel than mild steel.

It would appear from the videos that they are worked pretty hard being struck with a heavy hammer I do not think plain mild steel would hold up. That leaves the feathers.....They are a bit less than half round on the back with a wedge taper that exactly matches the wedge that bears against them that is struck. Mild steel here also may lack the toughness required. I guess you could cut and grind one set up with the materials to hand and give it a try.

This link is a brief list of steel types and their uses. **LINK** You would may need to heat treat the pieces after you have made them. I guess a medium to high carbon steel that you can harden and temper in your own workshop would be what to look for.

I did find a lot of references to feathers and wedges on the net and a few videos. **LINK**

**LINK**

Regards
john

Don't overcomplicate it. Feathers and wedge is a simple rock splitting tool made for hundreds if not thousands of years by every backwoods smith there ever was. Just make the feathers from hot rolled rectangular strip. If you can heat them to red, just round the outer corners of the lower part and bend them. They do not need to be tapered, although they will work better if they are. The central wedge bar can be of any tool steel, made flat and smooth in the forge. Do chamfer the top end so it has less tendency to mushroom.

Good luck, JD

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.

Hello Chris,

I am also a dry stone waller and what Jeff describes is all that is needed. The feathers will deform readily to fit whatever hole you put them into and will become expendable, so don't waste a lot of effort on them.

The wedge will drive more easily with a little grease on the taper face. You will be surprised how many sets you need to split a big rock.

Regards Brian

Edited By Brian Wood on 14/01/2014 16:12:53

Edited By Brian Wood on 14/01/2014 16:13:23

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

My understanding is that the pyramids were made using these tools -but made of bronze.

Neil

Hello Chris, good evening.

Perhaps this information doesn't answer your question, but even so, I dare to post it because it might interest some participant in the forum.

When I was a kid, in the early 60s, I could see granite blocks being cut in a quarry forcing, with a large steel hammer, a set of bulky wooden wedges in a row of shallow holes. Those wedges were then wet, which increased their volume, so forcing the granite block to separate from the large mother rock.

Hope this has interest to someone...

Best regards
Dias Costa

Wow, my one time local village industry of cutting granite had moved to steel tools in tthe late 18th century. A few rocks up on the moor still show evidence of the larger holes used for the wooden wedge system.
I would start with round bar, hot forge to a slight taper still round which is pretty standard blacksmithing, before using the half round grooves in a swage block to put the flat on. The intial tapered round will produce the tapered section.