Pneumatic power hammer build

#1
Hi All, first post after lurking here for a while.

I am moving from general blacksmithing (hobby, I work in I.T. and need a hobby with no screens) into bladesmithing and am in the process of planning a pneumatic power hammer to help with Damascus and my shoulder. I was going to make a tire hammer but saw a bargain online and bought a big bucket of basically new and reconditioned pneumatic cylinders dirt cheap and decided to go down that path instead. They look a lot easier to make as long as you have the air supply.

My question is this. I don't have any experience with pneumatic cylinders. The Kinyon style hammer calls for about a 1.5" - 2" bore and a 10" stroke ram for a 50-75lb hammer. I don't have any cylinders this size so need to know where the important dimensions are. I have a 3" bore with a 6" stroke, a 2.5" bore with a 12" stroke and a 3" with a 12" stroke as well as some smaller ones, all are working and seem to have no leaks. In testing, the 2.5" is slower than the 3"x 6" to move on the same air supply and the 3"x12" is in between. This may just be because the 2.5" is new and tighter. My question is regarding the stroke. Is 6" enough or should I go with the 12" ones? Obviously the system can be set to not go full stroke easily enough but I am not sure if I would have enough air supply for the larger longer stroke. Would the smaller 2.5" be likely to loosen up with a bit of use and move faster or are they pretty constant over time? I am not sure that its current speed is fast enough to work well as a hammer (it may be different with 75lb and gravity assisting). Should I just go larger and make the hammer bigger as well? I have a really big compressor that is also being reconditioned so once I have 3phase, I will have the air but the switching valve will get very pricey as well.

Any insights greatly appreciated.
Cheers, Ben
 

EdCaffreyMS

Forum Owner - Moderator
#3
Personally, I'm not a fan of hammers that are built with pneumatic cylinders.... seems people spend more times chasing issues than using them. That being said, Based on ones I've used, I'd favor a longer stroke versus a shorter one..... provided the bore was large enough to handle the ram weight.
Be very aware of the air consumption required! These type hammers generally take a 7.5hp/two stage compressor to run efficiently.... I've see time and again where folks have tried running them on a typical 5hp/single stage (at the recommendation of the maker/seller), and it just isn't enough air.
 
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#4
Thanks Ed. The long ones it is then.

My dad gave me a huge 10HP 3-phase compressor with an 8ft tank when he downsized so when I get my warehouse in a couple of months, air volume wont be an issue. I will start with the 2.5" and see if it loosens up but will make sure I can just slot the 3" in if required. The 2.5" should lift at least 250-300lb which is way bigger than I need. If I cant get it to work right, I can still convert the stand and anvil to a mechanical hammer, I will just make sure the throat depth is compatible before I start. My biggest issue (I expect) is going to be finding a 5 way pneumatic switch for such high volumes without it costing a fortune.

Cheers, Ben
 
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