|The MGA With An Attitude
SELECTING A KNOCKOFF HAMMER - WL-105
At 08:15 PM 4/10/03 -0400, Steven Winegarden wrote:
>"I see that there K/O hammers of many different materials available, Copper, Lead, Rawhide, and dual type hammers as well."
A hammer is a hammer, sort of. If you use a big enough hammer and a strong enough swing, it will get the thing off. Many different types of hammers are advertised, and some suppliers only offer a single type, and they would like you to buy theirs.
>"It seems that lead is claimed to be the least damaging to the chrome."
It probably is least damaging because of the especially soft face of the lead hammer head. It also deforms some on impact, so it doesn't bounce back much, in effect delivering most of the energy of the swing to the part being hit. That makes it fairly efficient so you don't need such a heavy hammer, and weight of tools being carried was a consideration in the sports car. It was also the technology of the day when the cars were in production. Very low tech by today's standards, and lead castings were easy to make. Now lead is more expensive, and to some extent considered an environmental no-no. So unless you're a concours originality enthusiast, it may be time to consider the alternatives.
>"yet in many cases copper has been used for the life of the vehicle. Are these any advantages to copper or preferences that you see in these types?"
From time to time over the decades copper has been cheaper than lead, and it still is today. It is also more durable than the lead head if it has to be used a lot (like in a service shop). But when you do a cost vs benefit comparison for your portable application, you might not like copper. Copper has a harder surface, so it is more likely to damage the chrome. It is also much more rigid than lead, so it will bounce back on impact. This returns a negative energy to the hammer (reversing the direction of travel of the blow), so by the law of conservation of energy it actually delivers slightly more energy to the part being hit. The impact is harder and shorter in duration, so it is more likely to loosen a very tight knockoff (hammer weight being equal), but the part being hit may move a lesser distance with each blow. Once the knockoff loosens and starts to move a bit, the sharp rebound of the hammer is of very little benefit, and it also represents a decrease in control on rebound and an increase in the likelihood of accidentally hitting something you didn't want to hit on rebound, like the body of the car. Better to deliver most of the energy of the blow to the part to make it move farther with each blow. As a result, the copper hammer may require more blows to get this job done, as well as possibly damaging the chrome, so it might be functionally less preferable to the lead hammer (unless the part doesn't want to move).
Steel hammers are another step farther in the same direction, having more rebound and causing more damage to the chrome. Incidentally, the chrome itself is very hard and resistant to damage by hammering. However, the base metal of the knockoff may be brass or bronze, and either of those materials is quite soft by comparison to a steel hammer. So when you hit the soft part with a hard hammer it will dent the part, in turn causing the brittle chrome to flake off. If you want to protect the chrome, you have to use a hammer that is soft enough to protect the base metal from being deformed, which is why the soft copper faced hammer was originally supplied with the car.
Rawhide covered copper hammers are also available these days. These are generally more expensive, but may be very good at protecting the appearance of the knockoff. The rawhide face covering is soft, so almost like striking the knockoff with your fist, and it won't damage the knockoff (until you beat a hole through the rawhide). The soft face covering has another effect, not necessarily an advantage. Because the rawhide is soft and deforms on impact, it absorbs some of the energy of the blow. It also spreads the energy of the impact out over a bit more distance of travel during the impact. This has the effect of reducing the force of the impact (not the total energy), so it may require a harder blow to loosen the knockoff. As such, you might feel more comfortable using a 2 pound rawhide faced hammer in place of a 1-1/2 pound lead or copper hammer to get similar effect.
>"Also, although the original hammers were about 1.5 pounds, now there are hammers up to 4 pounds offered. You could probably swing a larger hammer slower for the same effect or a smaller hammer more times or faster."
If the hammer gets too light you can't move your arm fast enough in a coordinated manner to deliver a strong blow. A heavier hammer can deliver more energy to the impact, but there is a point of diminishing returns. In effect, enough is enough. You might be more comfortable using two hands to swing a 4 pound hammer, but that sort of a blow is generally overkill for the job at hand. Also the 4 pound lump is a bit much to carry around in the boot, increases the risk of getting loose and causing some damage during transport, and adds unnecessary weight to the sports car. In other words, it isn't necessary. 1-1/2 pounds is generally sufficient if you have a vigorous arm and don't use it too often. 2 pounds might be easier to use for a shop tool that is used more often, and brass will hold up better to long term abuse where lead would eventually be beaten into an ugly mushroom.
>"What would be best for the K/O nuts and the wheels and hubs?"
If you like to optimize the application, and you don't mind the cost (some are cheap), the very best tool for this use is a dead blow hammer with polyurethane face. Cheaper ones will generally be polyethylene without replaceable faces, but will still serve the purpose well for this "occasional" application. Check here:
enter "dead blow" in the keyword search box.
enter "dead blow" in the search box.
These will dampen the blow and virtually eliminate rebound, very easy to use, protect the chrome parts nicely, and are durable enough to last forever with occasional use. They may even last indefinitely in industrial use if you renew the working faces occasionally. And oddly enough, it will bounce around less in transport, so less likely to cause damage if it gets loose in the boot of your car. This is one really sweet tool for this application.