Swage Block Design
The Good, the Bad and the Ugly
There are infinite
possibilities in swage block design. Infinite good designs and infinite bad designs.
A mathematically equal chance. Oddly enough, about what you find in any group of swage blocks.
What is good and what is bad depends largely on the type of block.
Rules for a personal block are much more lax than that of a commercial product.
Then there is the material type. You can get away with more in certain materials but there are pros and cons both ways.
Last is largely the subjective. A matter of opinion and taste about what is useful in a block.
The most common error in block design is weak corners.
Even with careful planning you can end up with weak corners.
Although you can "get-away" with weak corners in steel or good ductile iron they are still a design flaw.
Weak corners are about the only flaw that applies to personal blocks as well as all others.
Weak corners are usually the result of two side features too close to the same corner or one large feature too close to the corner.
Good swage block designers often place large features near the center of the block and small features toward the corners.
Besides reducing weak corners this puts the heavy work in the middle and the light work at the corners.
It also makes a nicely symmetrical looking block.
Features too close to edges or each other
This is similar to weak corners.
It makes thin places in the casting that should be avoided.
Too much draft
In most castings you are better off with too much draft than too little.
However, in swage block design where every surface is a working surface too much draft means distorted features and a block that sets crooked.
Swage blocks should have as little draft as is suitable for the shape.
Many years of design have set proportions that work for swage blocks.
Most blocks are about 1/2 to 1/4 their width in thickness.
Square is generally better than rectangular, especially in industrial or general purpose blocks.
If a block is to be rectangular it should be very rectangular not nearly square.
The advantage of a square block is it will fit more ways into a stand built to support it.
The only block that this does not apply to is a personal block.
If you make a block for yourself and you are happy with it then you have satisfied the only person that counts.
In fact the beauty of many personal blocks is their open spaces and simplicity of design.
In all other blocks the art of the design is getting the most useful shapes on the block without weak corners or features that interfere.
In commercial block design every shape is put on the block in speculation. So you want as many as possible.
However, it is also possible to overcrowd a block. The space between each feature should be some minimum and no less.
In fact equal flats between features is the most attractive design.
In industrial blocks with holes the art of the design is to create a block with no extra heavy sections.
Fitting as many shapes as possible in the block while keeping a minimum spacing and equal thickness throughout.
The block will cast better and have less shrinkage problems than a block with thick and thin sections.
However, doing this perfectly is nearly an impossibility when dealing with the various shapes.
That is why it is an "art".
Blanks - Occasionally you will see a big blank space in an otherwise well designed industrial block.
This is usually a casting error. The moulder was short a core or the core print was damaged.
Instead of scrapping the mold the core print was "slicked over" and the mold cast with the missing core.
Useless or Over Specialized Features
Except on personal blocks every feature on a swage block should be as generalized as possible.
Shovel patterns, candle cup pans and other similar shapes should be the subject of a special die made by the smith, not a swage block feature (unless it is a personal block).
There are a number of swage blocks on the market with shovel depressions.
These are a huge waste of space.
Now if the depressions were such that any conceivable or a very wide range of shovel shapes could be made in them then it would be acceptable.
This is the challenge of swage block design.
I have always wanted to make a fantasy swage block with star and moon shaped holes.
They would be practically useless but would make an interesting personal art block.
For more about unique special use features see Unusual Swage Block Features
Impression Shape or Depth
There are several features on blocks that are poorly understood.
Parted in the wrong place
- Cast holes
- Should be straight through, may have cast edge radii.
May be tapered for specific purposes such as stake holders.
- Half round swages
- To prevent pinching and cold shuts a half round should be cleared on the sides, not oval shaped as some suggest.
- Hemispheres (large)
- These should be no more than 1/4 to 1/5 the diameter in depth.
Should have a large edge radius.
These are NOT a mold.
- Hemispheres (small)
- These should be no more than 3/8 to 42% the diameter in depth.
These may be a mold or heading die.
- Are generally made too deep. Do not need stem or handle clearance.
These are often poorly shaped. It is an "art".
- In general all edges and outside corners can be generously radiused.
The exception is the top parting edge on cope and drag patterns which by necessity must be sharp.
This is an error never seen until the most recent modern era.
Prior to a few years ago all swage block patterns were either made by the designer who knew what they were doing or by a pattern maker with specific instructions.
This is a critical unforgivable error.
RIGHT: Blocks are generally a simple cope and drag pattern.
They are parted (where the mold divides) at the top corner of the block.
This means they have a very slight taper (draft) on the sides so that they can be removed from the sand mold.
Almost all the pattern is in the drag (bottom) half of the mold. The parting has almost no effect on the usefulness of the block.
Blocks can also be cast with no draft but that is a more technical method than is generally necessary.
WRONG: Improperly parted blocks have the parting down the middle of the block crossing the side features.
This results in the features tapering to the middle of the block making them high and narrow at the parting.
This makes these features useless without an undue amount of grinding or machining far in excess of simple dressing.
There is absolutely no reason for the parting to be in the wrong place other than the foundry demanding that the part be equally divided between the two halves of the mold (OR ignorance).
If the foundry demanded this as a condition of taking on the work then they were not a suitable foundry to do the job.
Even the most complicated shape can be parted in such a manner as to not put draft where it does not belong.
In this regard swage blocks are different than most castings.
Every surface of a block is usually a working surface that is intended to be used as-is.
In foundry work it is common to make castings that are going to be machined.
Extra metal is put on this surface called a machining allowance.
It is not unusual to draft this surface as it is going to be machined off.
Proper parting of a swage block is part of the designer's and pattern maker's art.
The Perfect Block
I have yet to see the perfect swage block.
Even my own patterns have errors even though I knew most of the above when I designed them.
Every block has at least one error. Most often they are forgivable or not too severe.
But there are blocks with MANY errors.
Swage block design, even for industrial blocks but much more so for artist blacksmith blocks is an ART.
It must be combined with a knowledge of pattern making OR the pattern must be made by a pattern maker that has a good feel for what is desired and expected.
Besides function there should be symmetry and a sense of proportion.
- Jock Dempsey, November 2006
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