1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. PLEASE: Read the FORUM RULES BEFORE registering!

    Dismiss Notice

Press Fit Hammer

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by lellasone, May 3, 2017.

  1. lellasone

    lellasone United States Iron Registered Member

    Likes Received:
    13
    Trophy Points:
    3
    City:
    Pasadena
    State:
    California

    -Return to Top-

    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
     
  2. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    1,745
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii

    -Return to Top-

    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.
     
    scwhite, woochucker, 4gsr and 4 others like this.
  3. Tozguy

    Tozguy Active User H-M Supporter-Premium

    Likes Received:
    625
    Trophy Points:
    113
    City:
    Drummondville
    State:
    Province du Quebec

    -Return to Top-

    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.
     
    4gsr, lellasone and RJSakowski like this.
  4. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    2,155
    Trophy Points:
    113
    City:
    Barneveld
    State:
    Wisconsin

    -Return to Top-

    I would consider threading and Loctite but with only .020 left to play with, you will most likely require pressing.
     
  5. Sandia

    Sandia Active User H-M Supporter-Premium

    Likes Received:
    164
    Trophy Points:
    43
    City:
    Sandia
    State:
    Texas

    -Return to Top-

    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.
     
    4gsr likes this.
  6. kd4gij

    kd4gij United States Active User Active Member

    Likes Received:
    913
    Trophy Points:
    113
    City:
    St. Petersburg
    State:
    Florida

    -Return to Top-

    Aluminum into steal won't stay tight. I would go with a .001 press and pin it with a 1/8" dial pin.
     
    Bob Korves likes this.
  7. wawoodman

    wawoodman himself, himself H-M Supporter-Premium

    Likes Received:
    483
    Trophy Points:
    83
    Location:
    Seattle, WA
    City:
    Seattle
    State:
    Washington

    -Return to Top-

    Agreed. Pin it.
     
    scwhite likes this.
  8. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

    Likes Received:
    271
    Trophy Points:
    63
    City:
    HUNTINGTON
    State:
    New York

    -Return to Top-

    Is this a dead blow or a soft faced hammer? Any pics that you wouldn't mind sharing?
     
  9. dulltool17

    dulltool17 United States Active User Active Member

    Likes Received:
    92
    Trophy Points:
    28
    City:
    Weaverville
    State:
    North Carolina

    -Return to Top-

    My take:

    .0015 interference.
    Heat Head; Chill Handle
    0.060 roll pin thru
     
    whitmore likes this.
  10. lellasone

    lellasone United States Iron Registered Member

    Likes Received:
    13
    Trophy Points:
    3
    City:
    Pasadena
    State:
    California

    -Return to Top-

    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.png upload_2017-5-3_21-26-59.png
     
    scwhite likes this.
  11. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    1,745
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii

    -Return to Top-

    Yes, I would use either a roll pin or a solid pin (steel). Roll pins are hardened and are perfect for this job. If you drill a 1/8" hole through the side of the head, right through the part of the handle that fits inside the head, that roll pin will hold the head solidly. If it ever needs to come out you can drive it out with a punch. The roll pin can be ground to length so it fits the width of the head perfectly.
     
    lellasone likes this.
  12. Tozguy

    Tozguy Active User H-M Supporter-Premium

    Likes Received:
    625
    Trophy Points:
    113
    City:
    Drummondville
    State:
    Province du Quebec

    -Return to Top-

    Ah, a hammer for demolition needs to be pretty solid. A small hammer like that will have to work very hard to reduce a piano to 6'' pieces so pinning is a must. Does the 'scrap metal' need to be assembled into a hammer on site? If so maybe make it a close slip fit and use a couple of set screws into pockets instead of a pin to secure the head to the handle. That way the screws can be tightened on site as needed.

    BTW you might have trouble passing that off as scraps, it sure looks like a beautiful hammer to me.
     
    scwhite and lellasone like this.
  13. whitmore

    whitmore United States Active Member Active Member

    Likes Received:
    32
    Trophy Points:
    18
    City:
    Shoreline
    State:
    Washington

    -Return to Top-

    At only half an inch, a 1.5 mil interference fit is VERY agressive, heating
    the iron to 400F only expands the hole by 0.0011. I'd cut it down to .001 interference.
    If retention is an issue, drill and bellmouth an exit aperture in the head, and peen
    the handle to rivet it in place. If it has to be pretty, bellmouth the head
    and center-bore the handle, and force a cone into the center-bore
    with some loctite or a light knurl, to wedge the assembly.

    0.005" of bellmouth is a lot (wood-handle hammers use twenty times that).
     
    scwhite and lellasone like this.
  14. cascao

    cascao Active User Active Member

    Likes Received:
    330
    Trophy Points:
    63
    Location:
    Belo Horizonte, MG Brasil
    City:
    Belo Horizonte
    State:
    Outside US / Canada

    -Return to Top-

    Have seen many projects like these here before and it let me thinking about metal handles vs wood handles.
    I think wood handle is more confortable due some vibration dampening but yes, metal handles look awesome and is durable.
    Don't you guys who made metal handles had some harsh feeling?
     
  15. Tony Wells

    Tony Wells United States Vice President Staff Member Administrator

    Likes Received:
    19,271
    Trophy Points:
    113
    Location:
    Tyler, Texas
    City:
    Tyler
    State:
    Texas

    -Return to Top-

    Roll pins are not hardened. They are soft. Many people incorrectly interchange the terms "roll pin" and "spring pin". A roll pin is actually a strip of metal rolled into a size slightly larger than the hole it will fit, and compresses as it is pressed or driven in. Once removed, it will not return fully to the original size. It is malleable.

    On the other hand, a spring pin, aka split pin by some, is hardened and is a single turn of spring steel that is just shy of the actual calculated circumference of the target hole, giving it the gap, or split. If measured, they are a bit oversize as well, like the roll pin, but unlike the roll pin, when removed they will return close to the original size. They are considered reusable, whereas true roll pins generally are not.
     
  16. mikey

    mikey Active User H-M Supporter-Premium

    Likes Received:
    1,745
    Trophy Points:
    113
    City:
    Honolulu
    State:
    Hawaii

    -Return to Top-

    I stand corrected, Tony.
     
  17. Rockytime

    Rockytime United States Active User H-M Supporter-Premium

    Likes Received:
    57
    Trophy Points:
    28
    City:
    Arvada
    State:
    Colorado

    -Return to Top-

    Thanks Tony. I was not aware of the difference between a roll and split pin. At 78 I was sure I knew everything. At the rate I'm going I'll soon be as smart as a teen ager.
     
  18. dulltool17

    dulltool17 United States Active User Active Member

    Likes Received:
    92
    Trophy Points:
    28
    City:
    Weaverville
    State:
    North Carolina

    -Return to Top-

    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.


    Yep!= well actually that is a spring pin, but it is what I had in mind. I think 1/6" is big enough and 1/8 might be too big.

    Maybe 3/32" (.093)
     
    lellasone likes this.
  19. Tony Wells

    Tony Wells United States Vice President Staff Member Administrator

    Likes Received:
    19,271
    Trophy Points:
    113
    Location:
    Tyler, Texas
    City:
    Tyler
    State:
    Texas

    -Return to Top-

    Well, just for fun, let's add a little more confusion. There is also a "groove pin". Basically a dowel pin with a linear placed vee bottomed groove rolled or pressed into it. Usually just one. But because the method of grooving is a displacement method, the edges of the groove are upset and make the pin fit tightly in a precision hole. Usually these work best in a closely sized hole and are pressed or driven in.
    A variation is a pin with upset serrations a short distance from one end only, sort of a "head" if you will. The advantage of these is they don't tighten up in the hole until you reach the serrated area near the end. So you can actually hand assemble something to check for alignment and fit before driving the pin into final positions. You will see these in assemblies where there is a piece captive yet not immobilized between two close fitting holes either side of it. Think gun parts like a trigger or hammer. They have to be free to move, but the pin obviously has to be secure against movement. It's just alternative to having the moving part with a clearance hole allowing a regular dowel pin in it. You won't see too many roll or spring pins in applications such as those.
     
    4gsr and lellasone like this.
  20. scwhite

    scwhite United States Active Member Active Member

    Likes Received:
    99
    Trophy Points:
    28
    City:
    Shreveport
    State:
    Louisiana

    -Return to Top-

    That is what I would do to
    Pein it with a ball Pein hammer make your handle long 1/8
    .001 or .002 press fit then Pein that 1/8 good and tight
     
    Last edited: May 4, 2017
  21. westsailpat

    westsailpat United States H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    121
    Trophy Points:
    43
    Location:
    SoCal
    City:
    long beach
    State:
    California

    -Return to Top-

    Nice hammer Jake , here is another thought ... Drill a clearance hole for a screw through the hammer head and c'bore it , and thread the handle for the screw . Get it welded up and file it down and polish .
     
  22. Chipper5783

    Chipper5783 Active User H-M Supporter-Premium

    Likes Received:
    319
    Trophy Points:
    63
    City:
    Red Deer
    State:
    Alberta

    -Return to Top-

    This is a very good topic. I encourage you to study up on "Limits and Fits" (see Machinery Handbook). The general rule of thumb for holding reasonably well is 0.001" interference, per inch of diameter. If you get enough interference, you absolutely can get it to hold without the cross pin. We put 50,000HP though a 10" coupling (shaft size) with no keys, no splines - just a lot of interference (much attention to detail and specialty tooling).

    Usually a person would bore the hole, measure it carefully and make to handle (pin) to the correct size for the fit you are looking for. You are dealing with dimensions in 0.0001" and it is easier to hit that number on an OD than it is on an ID.

    With aluminum and stainless, you can probably get 0.001"-0.0015" of interference together without too much difficulty. Do you have access to liquid nitrogen? You could certainly run a little test (or do a bit of number crunching) and figure out how much shrink you can get on the aluminum. When you are doing a large shrink fit (and .0015 on a 1/2" pin is), make sure you are well set up and things go together fast (you get one chance and it last about 1 second).

    Let us know how you make out, Regards, David
     
    scwhite and lellasone like this.
  23. whitmore

    whitmore United States Active Member Active Member

    Likes Received:
    32
    Trophy Points:
    18
    City:
    Shoreline
    State:
    Washington

    -Return to Top-

    I've heard this from carpenters, that steel shank and even fiberglass are
    hard on the tendons. That little bit of shock that travels back up the handle
    when a nail is struck... can add up. Those carpenters preferred wooden handles,
    and wanted the grain of the handle to be aligned so the growth rings were parallel
    to the head-t0-claw direction.

    Makes sense to me (and my tennis elbow). Comforting, that Dad's old wood-handle
    hammer was like new for the first fifty years, and still functional at seventy
    with the original handle.
     
  24. Cadillac STS

    Cadillac STS United States Active User H-M Supporter-Premium

    Likes Received:
    112
    Trophy Points:
    43
    City:
    Grand Rapids
    State:
    Michigan

    -Return to Top-

    To make a piano fit through a 6 inch hole the main problem will be the iron sound board. You need something with big mass to fracture the cast iron down to pieces small enough to fit through. The small hammer is really nice but you need something bigger.

    My plan would be to burn the piano as it sits to ashes and put them through the hole. Then all the smaller bits should be small enough to go. That will leave the large cast iron sound board the wires are connected to and that would take something with mass to shock and break the cast metal like a sledge hammer or some metal in that form.
     
  25. Cadillac STS

    Cadillac STS United States Active User H-M Supporter-Premium

    Likes Received:
    112
    Trophy Points:
    43
    City:
    Grand Rapids
    State:
    Michigan

    -Return to Top-

    Back to the press fit question and your specific hammer. Could you drill all the way through the hammer head and press fit the handle all the way through but also thread the handle and have a nut on the handle on top of the hammer head to keep it from pulling through?
     
  26. scwhite

    scwhite United States Active Member Active Member

    Likes Received:
    99
    Trophy Points:
    28
    City:
    Shreveport
    State:
    Louisiana

    -Return to Top-

    What is this hammer used for
     

Share This Page