MikeAlmogy

power hammer die design. problem with dovetail

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Hi all.

Here is my design for my power hammer (Ron Kenyon simple air hammer with Larry Zoeller modifications) die.

At the moment it is just the base but i run into a little problem/dilemma.

https://cad.onshape.com/documents/e3c54a90c5026613737eea49/w/3c2b0ea84d0f4dc883b1228e/e/9e5e7e7e4e0c0513d97797a9

 

The problem is with the dovetail.

Currently i'm using a 50mm diameter, 20mm~ height, 60 degree, dovetail cutter. However, it's angle is way more steep then the angle i see on other power hammers die and bases (ram and anvil).

It is very easy to use the dovetail i got since i only have to use one tool to do it and it is pretty fair and simple. However, i'm not sure that it is the right thing to do.

How can i cut the base and die dovetail? i do not see any specific tool to do it. The die itself is relatively easy and in the "worst" case i can do it in two parts, one for the dovetail and other for the head itself with the die design.

But the base is hard. I can tilt the head of the mill to cut an angle but i will have residual marking and grooves on the base of the dovetail, which i think is not very good.

Any idea?

Thanks,

Mike 

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Rough it out square.  Tip the sow block, not the mill head.  Finish cuts with a ball end mill cutter.  

Steel hates a sharp corner.

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2 hours ago, Judson Yaggy said:

Rough it out square.  Tip the sow block, not the mill head.  Finish cuts with a ball end mill cutter.  

Steel hates a sharp corner.

not sure what you meant tipping the saw block. 

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SOW block is the part of the anvil block you cut the dovetail in for the bottom die. I believe he's talking about angling the SOW block to match the dovetail taper rather than trying to set the angle on the mill. 

The LIttle Giant Powerhammer book has the angles and taper they used in their dovetails. It's a really gentle taper. Something like 1/8" in 3'. Do NOT quote me on that!! :o it's just an example of how gentle the taper is I do NOT recall the specific numbers!

Frosty The Lucky. 

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Ok so do you think this design is better? 

no dovetail, bolts only. however the option to rotate the die is limiteddie.thumb.jpg.f2d5d484662fe293be69041916f4571d.jpg

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A shaper is great for large dovetails and the tooling is far less expensive then a dovetail cutter. See if someone in the area has one. image.png.b865e104500383bf559a6574a642d124.png

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If you have a shaper I would do dovetails.

If you do threaded I would do studs. Constant in and out with threads will wear them out. Easier to replace a worn stud than a worn out thread in a block.

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yes sure studs. 

Well i'm not sure yet what to do. still thinking of it.

The whole idea is to unify my die for power hammer and hydraulic press (which i did not built yet).

The power hammer is small. about max 20kg. The press however is the biggest i can build, hopefully 50 metric tons.

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For a press that big I suggest you make dedicated tooling separate from the power hammer.

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It will have tooling of it's own but i do like the idea of unify tooling or at least concepts. not sure it is the right word.

 

Anyway, for now it looks like dovetail won. I just need to figure out the angles and technique to actually do it. I thought that i got the right machinery to do it (I got Schaublin 13 mill) and i need a 5mm cutter to do the final angle cut. I also need to know the angle of the dovetail but in worst case i will use 10 degree angle. 

 

Thanks,

Mike

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I suggest you use a double key system. In that method the dovetail in both the die and sow block is straight and centered. One wedge goes on each side of the die but in opposing directions.  This system was used on Bradley' and works great.

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If all your dies are exactly the same thickness, yes. However, having a wedge on either side means that you can adjust the dies to one side or the other fairly easily. I saw something somewhere about deliberately offsetting the dies for particular forging effects (was it in Weygers's The Complete Modern Blacksmith? I can't remember), which you would not be able to do with fixed indexing on one side of the dies.

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all my dies will have the same size of dovetail. 

 

To be honest, still not sure if it is the right solution for me, depend on my milling skills and equipment.

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The double key system is the simplest to set up and cut on either a shaper or a mill. If you can cut a straight line on you mill all you need is a custom made dove tail cutter and and end mill. Rough out with the end mill and finish with the dovetail. If your dies are not long you can get a long bar and in a single set up mill the dove tail down the whole length of the bar. Cut the dies to length after milling.  Bradley used a 5 degree dovetail angle with about an 1/8 radius in the corner.  Keys were tapered 1//8 inch per foot. I had a customer cutter made by a local tool cutting shop. I think it was around $100 but it was made from a 2 inch diameter end mill I supplied. If you're using a a brigldgeport type mill you probably won' go over one inch diameter. You might consider having it made from carbide if you mill has the speed to take advantage of that.

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Thanks :-)

i do not have to use a costume cutter since i can tilt my mill head to the desire angle and simply use a 5mm round tip strait cutter.

Anyway, my shop is under construction at the moment so it will take some time for me to start this project (unless i will be impatience).

I need to do some testing before using my high carbon steel. 

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A 5mm endmil will have some flex and take awhile to mill that out. You said you have a shaper, that is the tool I would use. Much faster and it can hog a dovetail faster the the mill can.

A custom carbide cutter would be very expensive and they are also very brittle. We used solid carbide custom cutters that we ground in house at the last shop I worked at.

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Wood shapers and metal shapers are completely different machines!  So be careful when you go a looking...I found good pics with: metal shaper images  and  wood shaper images.  Wood shaper spins a cutting bit, more like a router bit ; metal shaper uses a reciprocating bit, one more like a metal lathe bit.

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I do not have those machines. Not sure that i need to. I have a simple small manual mill. Not micro mill, Schaublin 13.

Like i said, doing this project depends heavily on my ability to actually do it. If after i will try i will see that i need more special equipment (and expansive one) or that my milling and accuracy skills are lacking, i will drop the dovetail and go to simple bolts solution. 

Thanks :-) 

Mike

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