Page 3 of 5 FirstFirst 12345 LastLast
Results 21 to 30 of 41

Thread: Diesel Wrist Pins For Cylindrical Squars

  1. #21
    Join Date
    Oct 2005
    Location
    British Columbia
    Posts
    6,805

    Default

    Most industrial duty diesel engines do not require an oil hole in the connecting rod small end or an oil hole in the pin .
    Like the set of rods shown below from a design that dates back to the early 50's, a 6 cyl. 855 cu. in Cummins. The bushing in the rod for the pin was pressure lubed through a channel in the rod from oil bled off of the con-rod bearing.
    Those are 2.5" pin bores just give some perspective to the illustration.


    Last edited by Willy; 06-19-2019 at 02:10 AM.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  2. #22
    Join Date
    Mar 2003
    Posts
    4,418

    Default

    Has anyone thought about just looking for a new one, like off eBay? There's a bunch listed under "piston pin", "wrist pin", "large piston pin", "diesel piston pin" and so forth.

    Average price is less than $20, often with free shipping. The largest two I can find don't show any dimensions, but from the look of the boxes are in the ballpark of 1.5"-2" in OD, and 3-5" long.

    Doc.
    Doc's Machine. (Probably not what you expect.)

  3. #23
    Join Date
    Aug 2009
    Posts
    6,395

    Default

    Quote Originally Posted by BCRider View Post
    Joe, I was looking at the three pistons in your picture of your piston collection. It took me a few seconds to realize that I was looking at the bandsaw in the background. Then I just about spewed my nice after dinner bourbon over my monitor. Dem's some serious big pistons ! ! ! ! And yeah, toss a bit of a cushion on top and a set of casters and they would be amazing shop stools ! ! ! !


    I'm a bit curious about why the distaste for oil holes. If the pin you get has oil holes they don't cover much of the surface and would be easily avoided. So I really don't see what the big deal would be if the pins were right in every other way.
    Just personal preference I guess. Since they come both ways, I would rather have one without holes.
    On the other hand, one with a hole could possible serve as a way to mount a dial. Just thinking. Perhaps slide a rod through it etc.

    JL............

  4. #24
    Join Date
    Aug 2009
    Posts
    6,395

    Default

    Quote Originally Posted by Doc Nickel View Post
    Has anyone thought about just looking for a new one, like off eBay? There's a bunch listed under "piston pin", "wrist pin", "large piston pin", "diesel piston pin" and so forth.

    Average price is less than $20, often with free shipping. The largest two I can find don't show any dimensions, but from the look of the boxes are in the ballpark of 1.5"-2" in OD, and 3-5" long.

    Doc.
    Yea, I have. Mentioned it a couple times in previous posts. First I'll see what I come up with for used. If I can't find a nice clean one new is my second option.

    Getting it square off an end will be the next chore. Don't know how square the ends are but I'm betting they aren't perfect. I have a few methods in mind.
    Perhaps someone could offer some ideas.

    I don't see what the big expense is in buying an actual cylindrical square. I'm sure they are all centerless ground just like the wrist pins. Outside finish has got to be about the same as wrist pins, in fact wrist pins may be polished to a higher degree. Centerless grinding is the fast and easy operation, squaring an end to .0001 or so is where the work is.
    I guess they price is high because of what it is..... a precision tool.

    JL..............
    Last edited by JoeLee; 06-19-2019 at 08:05 AM.

  5. #25
    Join Date
    Jan 2004
    Location
    Missouri
    Posts
    31,542

    Default

    Quote Originally Posted by JoeLee View Post
    ......

    I don't see what the big expense is in buying an actual cylindrical square. I'm sure they are all centerless ground just like the wrist pins. Outside finish has got to be about the same as wrist pins, in fact wrist pins may be polished to a higher degree. Centerless grinding is the fast and easy operation, squaring an end to .0001 or so is where the work is.
    I guess they price is high because of what it is..... a precision tool.

    JL..............
    There is rather a large difference (although one might not realize it) between a piece that actually happens to be square, vs a piece that is intended to be square, was made to be that, and is known by testing to be square etc within a certain tolerance, having a paper trail to a known standard.

    Not all of that higher price is a "because we can" charge.
    1601

    Keep eye on ball.
    Hashim Khan

  6. #26
    Join Date
    Aug 2009
    Posts
    6,395

    Default

    Quote Originally Posted by J Tiers View Post
    There is rather a large difference (although one might not realize it) between a piece that actually happens to be square, vs a piece that is intended to be square, was made to be that, and is known by testing to be square etc within a certain tolerance, having a paper trail to a known standard.

    Not all of that higher price is a "because we can" charge.
    Good points. Since the ends of a wrist pin are an insignificant surface I can understand the mfg. not fussing with them.
    Interesting to see just how close one might be. I'm sure they all vary.

    JL..............

  7. #27
    Join Date
    Apr 2017
    Location
    Kelowna BC
    Posts
    2,484

    Default

    In manufacturing squares, the difference between grades, is often a reflection of the amount of finishing to get it to spec.
    I have read that most Starrett squares are the same, the higher grades just have more hand finishing involved.
    Something about a dark room with a small light on one side, and checking against a master square.
    Last edited by 754; 06-19-2019 at 10:50 PM.

  8. #28
    Join Date
    Dec 2015
    Location
    Chilliwack, BC, Canada
    Posts
    5,455

    Default

    There's some testing you'll want to do to check the WP to determine if it will serve you as a cylinder square. I went through them when I made my own cylinder square last Fall or whatever it was. Basically anything reasonable can be used as a cylinder square if it passes the tests. And alternately with good measurement tools and techniques we can tune up a cylinder square to some extent.

    First off measure the diameter along the length and at at around about 5 "clock points" mark the points you measure at the ends so you keep the radial lines for these consistent along the length of the pin. Repeat these five or so radial measurements at about 6 to 8 positions along the length. You're looking to see if there's any "egg shape" or multiple lobes that might be present... or rather there will be but you're looking to see just how bad it is and if it's close enough for your needs. Or at least to know what you've got. Keeping in mind that if you know what you have then you can account for it when using it.

    Next and if it passes the diameter measuring set it on a couple of good V blocks (should be a matched set) and run a DTI on a stand along the length to check for any curvature of the axis. I'd repeat these along the same axes you did with the diameter measuring.

    Finally make up a table of the readings and length variations which would allow you to do up a map of the pin diameter and straightness.

    For all this you'll be wanting to use a mic that has a 10's vernier and at least a DTI which has .0005 graduations. And generally you an resolve both of these to within .0002 without too much eye strain.

    I did find that when doing this that it took a bit of focus and repeating measurements because there's a feel to it before you know you're getting consistent readings. So figure on repeating a lot of the early measurements after the first time through to double check your technique. It doesn't take a whole lot of sloppiness to mess things up when we're looking at resolving down to plus or minus a tenth of a thou. Or a hundredth of a millimeter.

    Do a "map" of the pin using the measurements. If the diameters are "eggy" or "lobe'y" with two or more fat places around the diameters then it might still be useable provided the end to end checks done in the V blocks indicate that it's straight even if it has a lobe or three and is not truly round. But that's why you're measuring it to find all this out. And you need to map any and all features first before you can start to think about squaring up the end.

  9. #29

    Default

    Ask yourself this question. What are wrist pins made for?
    The working surface of a wrist pin is often ground to a high degree of accuracy on the OD. This is the surface that does the work.
    The ends do no work short of holding them in place, grinding the ends as if making a tool would not improve its function. Many are simply turned before hardening and finish grinding of the OD.

    Roll the dice.

  10. #30
    Join Date
    Jun 2001
    Location
    North Central Texas
    Posts
    2,537

    Default

    Quote Originally Posted by Bented View Post
    ...grinding the ends as if making a tool would not improve its function.
    Unless they are full floating pins, in which case the ends will be ground to a very tight tolerance for squareness (and length - else they pound the locks out). I have no idea how common full floating pins are in the large diesel engines being discussed. Such pins also do not get pressed in or out, so a used one might still be in pretty fair shape.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •