I’m looking for the name of a certain type of mortise and any tips on doing it. It’s the type that doesn’t go all the way through the metal and forms a pocket. I’m looking to put some 3/8” holes in some 1/2” strap. I’ve done a little experimenting and had marginal success. I’d really appreciate help with the process and the particular tools used. 

That would be a blind mortis, tho a countersunk riveted mortise is almost invisible and may be what you are looking for.  

In wood it is a strait forward job to cut a blind mortise, and use a wedge at the tenon  when the joint goes together, I don’t see any way to forge a blind mortise (at least the keyed pocket) and riveting the tenon would just be a pain. 

A mortise punched threw and countersunk from the top with the tenon riveted and filed flush on the other hand is relitively straitforward

Thanks Charles, blind mortise is term I was looking for. I’m after that certain look for what I’m working on so I don’t really want to punch my mortise all the way through. On top of that, punching a 3/8” hole through 4” of 1/2” strap on edge sounds like a pain. 

Cool the mortise and heat the tenon as hot as it will take; but only on the end and let it upset itself in the hole; shoot I've done it with punches when I was first starting out!

Thomas, I take it you start out like you’re punching a regular mortise? Is there any particular profile I should use for my punch? 

You would like the bottom of the hole to be larger than the top. (Which in my early days happened because the punch got too hot and upset itself in the hot stock; I'd expect you could try working a small punch around the bottom edges to make the hole larger there without destroying the punch.  I would use a high alloy punch for that---like S-7 or H-13)

That’s a great idea about using the small punch to waller the bottom out. To make the actual hole, would you use a slitting punch then drift it to size or use a punch the size of the hole/pocket I’m wanting?"

Greetings Ranchmanben,

          Why don’t you just drill a few 3/16 holes through the 1/2 at the joint than plug weld . This would be a tight joint but would require some finish work at the welds. 

Forge on and make beautiful things 

Jim

I hope I’m not stepping out of bounds here but why not just make an interference fit instead of trying to rivet or upset the one piece into the other?

I’ve never done this so I’m only asking out of my own curiosity. As I have a chair project I’m planning that could benefit from a nice detail like this blind mortise. 

I’m not actually concerned with the security of the tenon in the mortise. The parts with the tenons will be in mortises on each end. I’m having somewhat of a difficult time figuring out the best way to make the mortise that deforms the material the least. 

Pilot drill your mortice, perhaps 3/16"or 1/4" for that size stock.  Chase the drilled hole with a punch/drift for the swelled look.  

Thanks Jud, I’ll give it a try tomorrow. 

„Fritz Kühn, Geschmiedetes Eisen“ has a small picture where he shows a wide bottomed hole and it was made such that there is a raised center section to help "push" iron into the sides---at least that is how I interpret the picture.  My German was good enough to ask about old smithing books at the fleamarket in Frankfurt; but some of the odd smithing details were just not covered in my highschool German classes in the mid 1970's...I have a 1939 original copy.

B.t.w. this guy (me, myself and I ) is a native German, so if some IFI member need some (german/english) translation I will do my best. Don't hesitate to ask in case. Your welcome.

Cheers, Hans

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On 06/01/2018 at 4:27 AM, ThomasPowers said:

You would like the bottom of the hole to be larger than the top. (Which in my early days happened because the punch got too hot and upset itself in the hot stock; I'd expect you could try working a small punch around the bottom edges to make the hole larger there without destroying the punch.  I would use a high alloy punch for that---like S-7 or H-13)

It would give you a slightly different look on the surface of the mortise, but wouldn't it be simpler to make the mortise and tenon both regular & to the same size, then whilst cold file a groove out of the tenon just below it's shoulder, fit the tenon cold, heat the mortise & pein the mortise to make it fill the groove in the tenon?

I'm remembering an old YouTube video by Torbjorn Ahman where he did something similar in the course of making a swage of some sort.

In Rowan Taylor's video series about reproducing the Sutton Hoo axe, he shows how he put a swivel on the end of the handle by creating a wide-bottomed hole and upsetting the stem of the swivel into it. His procedure might be useful/inspiring for your mortise problem. Here's the relevant video; the bit with the swivel starts at about 10:48.

 

Although it’s now what I’m after for this project, it is a very cool video and gives me a few ideas for other projects. 

How'd it go?

Should be meeting up with a buddy tomorrow to work on this project. I’ll post the results. 

Update time. I asked a friend of mine, who’s more handy with a lathe than I, to make me a punch out of S7. It worked out exactly how I wanted. Here’s the first trial run. I got a little off center but i know how to prevent that in the future. 

2 hours ago, Ranchmanben said:

@Judson Yaggy Update time. I asked a friend of mine, who’s more handy with a lathe than I, to make me a punch out of S7. It worked out exactly how I wanted. Here’s the first trial run. I got a little off center but i know how to prevent that in the future. 

 

Looks good!