Press Fit Hammer

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lellasone

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Hello,

As part of my ongoing hammer project, I am experimenting with press-fitting the handle (2025 aluminum) into the hammer head (304 stainless steel). I currently have a 0.520" diameter hammer neck, and a 0.510 hole for it to fit into. However, I am somewhat at a loss to determine what the final dimensions should be. Ideally, I would like to have the two hold together just based on friction, but if need be, I could add glue as well.

In any case, I wanted to see what people thought about sizing the wholes and whether adhesive is necessary.

Many thanks,
All the best,
Jake
 
Jake, I am going to guess that a 0.010" press fit is ambitious. There are online calculators for this sort of thing but I would guess that a 0.005" fit might be more realistic. This assumes you have a suitable press. Of course, you can freeze the handle and heat up the head but you are likely going to have issues if you try for that 0.01" fit.

Personally, I would try for a more reasonable fit - 0.002" and I would pin the head on and not rely on any adhesive. Nor would I simply rely on a press fit to hold the head on. With repeated strikes, the head will come loose at some point and may then become a missile. Just an opinion.
 
If you are looking for the best friction fit then definitely heat the head and cool the handle to get the greatest temp difference possible. Be ready to assemble quickly as heat will transfer rapidly. Aluminum will deform relatively easily in an application like this so depending on how the hammer will be used consider the alternative of a slight taper and a maybe a screw on the end to lock the taper.
 
I would consider threading and Loctite but with only .020 left to play with, you will most likely require pressing.
 
I agree with the above posts, that the handle will eventually loosen up if not secured with some method. Don't thank Loctite will be the answer either. I would personally make the handle out of steel for this application.
 
Aluminum into steal won't stay tight. I would go with a .001 press and pin it with a 1/8" dial pin.
 
Is this a dead blow or a soft faced hammer? Any pics that you wouldn't mind sharing?
 
Mikey - What you are describe - the head flying off - is my worst nightmare for this project. When you say pin the head on, do you mean drilling a pin through the side of the head through the portion of the neck inside the head?

Tozguy - Any chance you could expand on what kinds of use case would make one option or the other more appropriate?

Sandia - That's a good suggestion. I wen't with aluminium for this handle because it was light (and free) but in the future maybe I will try using steel and then drilling it out to help with the weight. Would steel perform better as a press fit?

Emilio - Neither, it's a regular steel hammer with a point on one side. My school has a competition to see how quickly a (terminally damaged and irreparable) piano can be reduced to pieces small enough to fit through a 6" hole. Current students are not allowed to use traditional hand tools (sledge hammers or the like), so I am bringing a few pieces of scrap metal that happen to have been arranged in a hammer like shape (which, just to clarify, is exactly what that rule is intended to encourage).

Dulltool17 - I have been having more trouble than I would like to admit figuring out what a roll pin is via google. Do you mean these kind of things: Harbor Freight Link.

Everyone - Thank you so much for responding, I have been consistently blown away with how welcoming and helpful the Hobby-Machinist community has been (even in the face of silly questions).

At this point, it seems like there is a pretty strong consensus that pining it is the way to go. Does a 1/8th diameter brass rod seem like a reasonable option? My plan would be to sand the handle down a bit more till it will press fit in without LN2, and then insert the pin from the side through the hammer head. Not sure how to get the pins to be flush with the steel though, belt sander maybe?

Pictures as requested:
upload_2017-5-3_21-26-25.pngupload_2017-5-3_21-26-59.png
 
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