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Old 06-01-2011, 12:03 PM
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McClary McClary is offline
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Default best wood for Hammer forms

ok .. im in search of some good wood for a hammer form....
one of the uses i will need it for , is a truck wiper cowl i make from 20g crs ...
i have to hammer down all 4 edges for this...
i have made a MDF hammer form... but its about to be worn out from all the use...
i would like to make another one out of some good wood that will keep its shape for longer.. cause its a pain the make these forms... with the angle cuts and etc.. and to keep the gaps right on the trucks....
so whats a good recommended wood that wont break the bank?



this just example how they go... this one is not fasten down yet... so dont mind the miss alignments and gaps.. lol





thanks...
mat
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Old 06-01-2011, 01:48 PM
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Mat, I have used kitchen counter scrap to make hammer forms. It holds up well and you can shape it easily. There was a counter top manufacturer here the would give me some of the cutout and short left over sections from jobs. The formica laminate top holds up very well even with a radius sanded on the edges.
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Old 06-01-2011, 02:20 PM
Overkill Overkill is offline
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Default Harder the better

I've used poplar, it's hard, but tends to crush a bit. Oak is better, and likely maple would be best.

Cheapest source of oak is pallets that were made for heavy items.

Also think about other materials - plastic cut offs from Tap Plastics, scrap aluminum and steel.
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Old 06-01-2011, 07:58 PM
Rick Kilgore Rick Kilgore is offline
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Default Re: best wood for hammer forms

This was part of a tech article I was working on and addresses a number of different materials suitable for hammer forming. This is more a categorization of materials I have experience with and from a fabricators perspective.


Materials for hammerforms.

Before you start a couple of questions need to be answered. What material will the formed part be made from? How many pieces are needed? What level of accuracy and /or repeatability is needed? What is the budget? What material/s are handy?

Once you have answered these questions the process of choosing the hammerform material can begin. You can break up the materials into a number of categories, for the sake of this article I will stick with function with an occasional comment on cost.

For simple shapes, one or two finished parts made from soft material.
To define a simple shape for the purpose of this article we will use a part that is mostly flat with a profile consisting of gentle curves and straight sections. Similar to a belt guard.

Wood

Soft woods - Pine, Spruce, Aspen, Birch, Mahogany, MDF. Regional availability may dictate which is most plentiful.
Pros – easy to work by hand and easy on tooling. These types of woods have widespread availability.
Cons – Not very durable, prone to denting, splintering and splitting in heavily worked areas, especially when working with the grain.
Consider the areas of highest stress when choosing your part’s orientation to the grain direction. Plywood varieties can assist with durability at the expense of some workability.

Hardwoods – Oak, Maple, Hickory, Ash, Walnut, Lignum Vitae to name a few. Regional variants would be available.
Pros - Easier to work than metals in most cases and can still be managed using hand tools available to most craftsman. An inexpensive form is available from recycling pallets, especially ones used to ship metals or machinery.
Cons – Has many of the same issues as soft woods, just to a lesser degree. Plywood made from hardwoods offer no significant advantage. These woods are more costly to use in many cases, sometimes rivaling superior materials of an appropriate amount.


Plastics
Fiberglass, UHMW and Die Planking

Fiberglass - Polyester or epoxy resin with fiberglass cloth or matting.

Pros - Works well for capturing complex shapes and can capture details with care, often quicker than other methods. Is very good for pulling a duplicate from an existing part. If thick enough can withstand considerable abuse. Polyester is relatively inexpensive to work with.

Cons - Cure times can be a problem for simple items. Requires multiple layers to build up an adequate thickness to hold up to abuse. Can be a skin and/or respiratory irritant. Polyester will attack untreated forms made from foam. May require additional learning to acquire necessary skill level. Can build up high heat during curing, sometimes significant enough to cause burns and possibly a fire. Heat build up can also cause distortions in the form requiring additional work to correct. Often requires additional structure for support.

UHMW - Ultra High Molecular Weight Polyethylene.

Pros - Can be used as a substitute for wood in many instances. Can be cut and shaped using wood working tools. Lower cost than many hardwoods at retail prices. Stands up well to moderate impact abuse. Will hold up to multiple parts better than wood in many instances.

Cons - May be difficult to get in the sizes needed. Difficult to bond for increasing thickness. May only be available online with shipping for many areas. Smaller/finer details will be lost with repeated abuse due to flattening. Denting can occur from misplaced hammer blows or to many blows in a particular area i.e an area requiring considerable shrinking. Dents are pretty hard to repair to continue using the form.

Die Planking - A machinable plastic compound used for machining program prove outs and die try outs. Some types have metal particles cast in the compound for more impact resistance.

Pros - Shares many of the same pros as UHMW with one exception being cost.

Cons - May only be available online with shipping for many areas. This can make the cost prohibitive for many.

Metals


Basically any metal that can be machined and or welded into a shape has the potential for becoming a hammerform.

Aluminum - A common material with widespread availability.

Pros - One of the easier materials to machine. In some instances wood working tools can be used cautiously. Grinding with a rotary file or burr is possible and repairs can be made by welding. A number of parts could be assembled in a fashion to rough out a shape leaving less contouring to achieve the final shape. Fairly durable for multiple parts, can be repaired.

Cons - Cost can be an issue. Lack of access to machine tools and/or welding machines capable of welding aluminum can make using this material a non-starter for some.

Steels - Low carbon steels or alloys would be most desirable.

Pros - Scrap steel can be used. The most basic fabrication tools can be used for much of the work required. Can be easily stacked creating a rough shape to be ground to the final shape. Welding is more accessible. Very durable for multiple parts, easy to repair dents and dings.

Cons - Can be difficult to grind final shapes, taking both a lot of time and abrasive materials. Can be heavy to maneuver sometimes requiring team lifting or some form of lifting device to assist.

Concrete


Concrete - A number of possibilities exist here. Mortar, Ready Mix, Lightweight concretes with gypsum.

Pros - Pretty durable for larger shapes. Available pretty much everywhere. Works well for casting an existing shape when the existing shape can be used as a mold. Repairs can be made using the same materials.

Cons - Requires some skill to shape freehand. The majority of the shaping needs to happen before the material cures. Does not hold fine detail very well, chips easily. Can become quite heavy or unwieldy to move.
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Old 06-01-2011, 08:42 PM
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Well done Rick. One other option is fiberglas reinforced bondo like Dynaglass. Very tough, can be reinforced with steel.
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Old 06-01-2011, 09:10 PM
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Or aluminum. Can be cast, poured, easily cut and machined, quite possibly even poured over an existing part with a wire backing like a wireform. Can be shaped on a router table, or cut with a circular saw.

Havent tried the cast and pouring bit yet, but it gives me some ideas.

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Old 06-01-2011, 10:46 PM
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thanks for all the info ..

actually it gave me an idea... im thinking , to keep the cost down... i can get a 1/4" steel plate cut to specs... then cut small 1" tall long pieces and weld to all the sides and polish smooth... this would give me the thickness i need for the sheetmetal to fold over , and yet keep cost down...

mat
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Old 06-01-2011, 10:56 PM
Richard-S Richard-S is offline
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I never thought of casting an aluminum hammer form, and I have a foundry in my sculpture studio.

The one thing you have to account for is shrinkage. I'm not sure what it is for aluminum as I cast mostly bronze. I can imagine making a pattern a bit over sized from something soft, plaster or white pine, casting it in sand, and doing the final machining of the edges on a router table.

Many is the time I have beat something out of stainless sheet metal and wished I had a hammer form, but wooden hammer forms and stainless don't go well together. (About the only way to form stainless is when it's red hot.)
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  #9  
Old 06-14-2011, 01:50 AM
Rich Pauza Rich Pauza is offline
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My favorite is called Baltic Birch.

It's pricey - but it works bad ass.

Two coments - # 1 When using ANY kind of woods - were you will be tac welding ( on buck ) wrap 2 pc's of the heavyest aluminum foil you can find over your buck & under your weld seems - even small amounts of heat will draw the resins up out of the wood & into your tac weld - the result is a tac that looks like a chunk of lunar rock.

#2 Kind of surprized it was not mentioned yet, buy for me anyway, the biggest plus to an aluminum or steel buck Or even concrete is the fact you can use so much more heat when you are forming aluminum or copper. Un beleivable amounts of ( heat shrink ) can happen while working over material that wont catch on fire....!

RMP
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