Best rubber for over-molding a hammer 1

[vbdesign]

Hello,

I'm designing a sledge hammer that will have a steel handle that will be over-molded in rubber. There are other products on the market that already do this, but I don't work for these other companies. So, what rubber would be suited for that application? Oh, I'm talking about the big 3 foot long handle type. We will also be coating the head in a harder (compared to the handle) durometer rubber (or other similar material) as well. This hammer will not be used for demolition of hard materials like concrete. But would still need to be durable. The thickness of the coating on handle will be a minimum of .170" and up to .300" in some areas. The coating on the head will be about .100"

I guess I should also ask what process would best be suited for this? Quantities will be low at first, maybe 100-300 in a year.

Thanks for any input.

 

[GrahamBennett]

I would suggest the handle is over-moulded with a TPE-based compound - soft to the touch. I would need to know more about what the end applications are before recommending a suitable hammerhead compound.

 

[vbdesign]

Thanks for the response!

I will look into your recommendation. In regards to the striking surface, I will send you a private message. There is a patent pending on this, but I rather err on the side of caution.

Thanks again.

 

[vbdesign]

OK, look like I can't send a message privately. Or I am just not seeing how it's done. So I will try to answer your question as best I can.

This hammer will never strike anything metallic or anything harder than the sole of a work boot. So stuff that is non-rigid. Sorry for the vagueness.

Hope that is enough info.

Thanks.

 

[Compositepro]

You should consider using PVC plastisol. You just preheat the handle to 500F, or so, and dip coat your part.

 

[btrueblood]

PVC dip works, and is cheap (probably the cheapest possible way to make a conformal grip). But it makes for a slippery grip. I don't like the TPE handles much for the same reason, though with a good mold it can be worked around (add ribs/holes for better grip). A more expensive approach would be an epdm grip, but the cycle time would be much higher (epdm must be cured, which takes time and temperature), and thus cost more, than a TPE injection mold. Initial tooling might be cheaper than the plastic injection molds for TPE, so it's something to consider if your volumes will be low.

Nitrile rubber or a urethane for the impact surfaces - both can take a lot of abuse, and can both be formulated to be non-marring. I think natural rubber might be an option too. If you are going have high volumes, then the world of plastic injection molding opens up to you for the impact surfaces as well. We have a bunch of 5# dead-blow hammers that appear to be molded in polyethylene, and they have held up well over the years.

 

[vbdesign]

Thanks for the responses!

Compositepro, the handle will have a specific shape to it, so the dip coat doesn't sound like it's a viable option.

btrueblood, You point out some things are becoming very apparent to me. That is there are many ways to make this work. Sometimes too many choices is not a good thing. Unfortunately, the volumes will be too low for plastic. Urethane is something I have been considering for the head. I imagine there are urethane compounds that would give me what I want for the handle as well. The reason I wonder that, is it seems finding a vendor who can do one, can't do the other. Therefor finding one process and type of material seems to be the best way to go.

Thanks!