Friday, March 02, 2018

Getting HAMMERED - #3 Setting Up

Number three in a series :
Follows up from yesterday's post : (effects of hammer profiles)
and Wednesday's post : (looking at hammer shapes)

When you get a hammer as brand new - it is not ready to use.
We had discussed how individual head shapes and weights suit different individuals.
This is even more true for the handle of any hammer.

First thing: Look at the working face and peen edges.

Most new modern hammers will have been either cast or drop forged to make the metal head. (If you spent some huge amount for a 'custom profile', the head might have been hand forged?) This rough form is then polished on the face and peen end.
Most typical is to create a flat surface, with some amount of 45 degree bevel around the edges.

Left - brand new Italian / Right 'antique' Engineer's
In the image above I picked two hammers that had roughly the same shape and roughly the same sized faces.
You can clearly see the sharp edges to the manufacturer's bevel on the left hand (brand new) hammer.
The other has been set up correctly for use (in this case also a good long working life!) What you want to do is gently round off those sharp edges. If you don't, you are going to find that even with a dead flat impact stroke, each blow is going to leave a crescent shaped cut into the soft metal. This will become a serious problem if you start forging with the edges (normally done to more quickly sculpt the metal into shape).
Remember that this also applies to the peen side of the hammer.
I personally undertake this rounding of the factory edges with a fine belt sander, but a fine tooth file would work equally well.

Second thing : Change that handle!

My primary forging hammer with two new handles (click for life size)
• The ideal material for a forging hammer handle is ash or hickory wood, with a clear, dead straight grain.
• Fiberglas is seen as a substitute for wood. I personally find Fiberglas handles 'whippy', jumping up on the return stroke and thus more difficult to control. This does indicate good energy return from the stroke however, so your opinion may differ.
• Plastic handles are now found on cheap 'China' hammers. I personally find plastic handles almost completely impossible to use. With all plastic, the return bounce from any stroke can go almost anywhere. This makes it almost impossible to maintain any uniform rhythm, and also very difficult to control your aim between individual strokes.
• Plastic / Fiberglas core? I did purchase one of these, recently available on Mechanic's ball peen and hand sledge hammers. As I don't often work with the profile / weight of the sample, I can't reasonably offer an opinion here. I strongly suspect the result will be something between all Fiberglas or all plastic = not acceptable.
Note that 'all metal' handles are NEVER found on forging hammers (although seen on construction framer's hammers). For good reason. The shock effect on impact would be massive, with the amount of rebound from a stroke almost absent.
I have seen some 'fiberglass with metal core' handles, again on mechanics profile hammers. Again I don't expect those to function well for forging.

Above are seen two easily available replacement wood handles - at least here in Canada.
Top - from Princess Auto - Engineer's Hammer Handle
available as 14 inch ($10 at writing) and 16 inch ($13 at writing, seen above)
Marked 'Made in USA' *
Bottom - from Home Hardware - Benchmark Replacement Handle
available as 16 inch ($13 at writing) *

Now - look at the shape of the two new replacement handles (or on any new hammer) - compare with how my main forging hammer has been set up:

Setting up a new handle (click for life size)

In the comments above, you see continual reference to two primary aspects : Reduction of Impact Shock
Energy Return / Lift
You notice how the two aspects are directly linked to each other.

I maintain that reduction of impact shock is critical.
Impact shock goes right into your joints, most especially your elbow. One jolt per stroke. How many strokes in a heat cycle? In a forging session? Over a life time?
Obviously even a very small reduction in impact shock becomes massively important over the long term.
Consider energy return. Even a small increase in the natural 'bounce' return on each individual stroke again is multiplied by the huge number of individual strokes made. If that energy is not returned to the hammer, it will be your muscles contributing the difference.

So - when you examine the new handles, you see the wood is thickened, just below the head, just before the shaft diameter. Why? Because this is typically where a handle will break. Handles are manufactured this way to 'make them last longer'. But thickening the shaft also makes the handle more rigid = more shock + less bounce.
You can see that I thin out the wood below the head, down to the minimum diameter of the shaft - and along the entire shaft length. This *absolutely* shortens the effective working life of the handle. I typically get 18 - 24 months use out of one of the indicated handles before it breaks and needs to be replaced.
** What does a replacement elbow cost? **

Any new handle will have either paint or lacquer on it (done to keep them looking clean in storage).
At a bare minimum, you will want to remove the coating down to bare wood. This is because that coating will hold moisture from perspiration onto your palm. If the skin gets damp, it will soften. If it is soft, you are likely to get blisters. Most certainly you will not be able to work with painful (!) torn open blisters. (Note that as you work more and more, your skin is going to toughen. Eventually your hands will likely stop sweating at all.)

Remember the discussion on suiting total handle length from yesterday?
Cut the handle down to suit your body size.
(more on this below)

The next important alteration is to shape the handle to your individual grip. This will be a combination of diameter, and shape.
Diameter is largely based on your actual hand size, a combination of palm and finger length and thickness. (Mine is 8 inches / 20 cm. I've mentioned Kelly, hers is 6 inches / 15 cm. Obviously, we need quite different diameters to our hand grip section of a handle!) Just grab the handle (after the head is attached ideally) and keep modifying it until it feels comfortable.
Shape is based on grip strength. For most people this will be some oval cross section. You will find a perfectly round handle hard to control. You can not 'feel' where the head is positioned, and a round handle tends to shift (rotate slightly) on the return bounce. These days my joints are stiffening (arthritis from all those hammer stokes!) and I find I need a very flat sided shape to really grip and control the hammer.

Now, I also apply some tape to the working handle.

I suggest for new students that they apply a simple loop of tape marking the correct grip point on the handle. Note that this on the far end of the handle.
The purpose of this tape is to remind you to keep your hand grip at the correct place on the handle.
If you find you are constantly sifting your grip forward down the handle towards the head - there is something wrong with this hammer - for you personally.
Get a different hammer! Most commonly this means the handle grip section is not comfortable (diameter and shape). It may mean that the head profile, thus dynamic in motion, is just wrong for you. It may additionally mean the tool is simply too heavy for you to correctly control.

I usually run a length of spiral wrap down just below the head, about 3 or 4 inches (7 - 10 cm). I will sometimes first use a layer of aluminium metal duct repair tape, always followed by good old hockey tape.
There are two reasons here. I find that when I'm making large sweeping curves, especially complex shapes that involve me really leaning over the horn, well , sometimes I do miss. That layer of tape protects the top of the handle from damage if I end up missing and hitting the top of the handle against hot metal. (That is why electrical tape is a bad choice!) I regularly put aluminium tape on to ball peen and crowned hammers, which I use for hot dishing sheet. The reflected heat off a piece of sheet at forging temperatures is incredible, and this just helps protect the wood . (I did actually have a handle catch fire one time!)

Remember that bit about damp hands? My skin is toughened and so dried out that my hands don't actually sweat any more.
This is important as it relates to the red tape surface seen over the handle grip. This is a self sticking silicone rubber tape sold for making quick plumbing repairs. I apply a double layer thick wrap of this to all my personal working hammers. The effect is to create a slight shock absorbing layer over the handle.
This tape can be purchased from sources like Lee Valley Tools, (at writing $12 - it now comes in colours!), one roll I get three hammers worth. The application is not extremely durable, I find I have to replace it about every 12 months.

* Be careful about the marking 'Genuine Hickory'!
The Benchmark handles were originally made in the USA - of *American* Hickory. Recently these have been sourced from China, still marked 'Genuine Hickory'. 
I had checked this out when my last purchased handle just did not perform as I expected. The handle was too rigid (both increasing shock and reducing bounce height). I found out that there *is* a species known as 'Chinese Hickory'. It obviously does not have the same mechanical properties - as are required.
Home Hardware does have an alternative available : '16 inch Blacksmith's Hammer Handle (listed at $12). I have just ordered two from this new supplier to check on the quality.

No comments:


February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE