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Mini Forging Press Goes Bang (With Pics)

Adam Thorpe

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Hey I Forge Iron My first post here


Ive been hanging around here for a few months well getting my tools (anvil, Forge, Post leg vice) together. This is still I believe to this is the greatest tool I've found yet.


Little bit about me: I am  a 21 year old Renovator 3.5 years in my craft. Also woodworking is my passion in life. learning about the old ways of wood working and tool making has led me to black smithing. love it haven't made any thing to wright home about YET.


 Till today I made a one of those Mini forging press you know the one that's been posted here a few times. I am in Ontario Canada Just out side the G.T.A so we have princess auto instead of Harbor Fright  most of the same stuff different badge. That s where I got my 20 ton hydraulic jack and the little flux core welder I used to weld the thing together. So when I came around to thinking about building this press instead of kidding my self about having the skill and equipment to weld this together I knew I had to use bolts every where I could so this weekend I started to bang this thing out.




So when I ran out of welding wire I decided to just bolt the top section to the base sit the jack in and test it out. kinda expecting my welds to break. I stool behind my steel shop door and let her have it. I mean I just gave her for about minute once the top and bottom anvil bottomed out. Then she made a bang I waited a few mins to check on it, released the pressure of the jack and noticed my welds were in fact fine but it was one of the grade 8 bolts that i have installed to attach the top to the base had sheered right off and flew about 2 feet away. Glad I practiced safe pressing. So as you can see in my pictures That there is a gap between the base side and upright where the bolt broke also there was no bolt shank in the ?? Lets call it shear zone ?? just before where the nut goes bottoms out. Might be answering my own question here bit it I put a piece of 1/4 in plate in the gap drill it out ,find the right size shankned bolt (If they even make 2 1/2" shanked 1/2' grade 8 bolts) and then weld it together dose it look to be a solid right to forge with? Hope this makes scene.


I got to say everyone on this forum rocks I don't think I would be as far along as I am now if it wasn't for all you great people out there. 


Thanks Adam Thorpe


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Did you calculate  or lookup the shear strength value of that screw?


I don't have the numbers in front of me but I think that the shear value of a half inch grade eight screw is several times less than the power of that jack.


That's backwards, there should be a safety factor several times in your favour, not the opposite



Not being a Safety Sally here, but strength of a pin relates to volume which goes up rapidly with diameter.


Grade eight screws will often break at a thread root

Think about using plain pins in much larger stock.




As has been said, rethink it all bigger and heaver.


Afer you havfe made hundreds or thousands of pressings, things will have worn and stretched and fatagued even more than now.



I wouln't trust a little flux core welder to hold it together either.

They're notoriously bad for poor penetration.

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If you look at this 20 ton A frame press you will see that all the bolts are in sheer alignment.  Not being pulled on.  That was your problem.  Much stronger as a sheer cross section.  In other words.  Don't pull on them or push  on them.  Set them cross wise to the forces.  They will hold up much better.


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Before you go any further you should buy Jim Batson's press book. http://www.iforgeiron.com/topic/15229-where-to-get-jim-batsons-hydraulic-forging-press-manual/ Even if the press in his book is too expensive for you right now, there is lots of engineering information on press building.  It will give you the information you need to do the math to do things safely.  A press is potentially Deadly, much more dangerous than a hammer.  I have a 40 ton press that I use for some forging and cold bending up to 2" round.   Even though all my tooling is way over built I always look at where things are likely to fly if things were to break and I don't stand there. 


For a design that does not need any structural welding which your welder is not likely capable of doing.  I would look at getting a piece burned out of plate.  True cut Steel in Hamilton is very reasonable.  I bet you could get a piece of 1" plate big enough to do an O shaped press burned out for considerably  less than $100

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