Announcement

Collapse
No announcement yet.

Building a coupling guard for a backhoe

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Building a coupling guard for a backhoe

    Well did my first successful trepanning operation. I’ve done them before but the quality was generally poor. This time however everything went extremely well and it was the most challenging trepanning I’ve ever attempted.

    The material was 1” thick 6061 aluminum. I took the corners off a 6” X 6” X 1” block with my bandsaw to speed up the turning operation. Once it was round I prepared a trepanning tool from 5/8” X 5/8” HSS with 8% cobalt. To speed up the grinding I used a .045” cutoff wheel to get the basic shape for the trepanning tool. Then it was just time to cut the slug out, and it took a long time. I probably should have made the tool a bit thinner. At 1/8” wide it took my 2 HP 13” South Bend forever to get through it.

    The part is a 13/16” long extension to a coupling guard for a small backhoe. The ID is 4 3/8” and the OD roughly 5 1/2” with 4 each 3/8” mounting holes. The rabbits are 0.100” wide by 0.125” deep, one male and one female.

    So my question is. How long would it take you to grind a trepanning tool and make this part if given a 6” X 12” X 1” chunk of 6061?

    Ron









  • #2
    I made a 3/4" trepanning tool a month or so ago. It was not grinding fast at all until I put a fresh 7" wheel on the angle grinder. Then it went pretty quick. Probably took another 30 minutes to get it shaped in on the bench grinder.

    As far as cutting: Theoretically 2.5 minutes for my piece, which was 5/8" cast iron, at 60 RPM and 4.5 thou per rev feed. Probably about the same for the aluminum. I can't say what the entire part would take me. Doesn't matter, it's not a race. You got a great looking part in the end. Nice job!

    PS. The ways on the South Bend look pristine. Got and more pics?

    Click image for larger version

Name:	IMG_7778ECS.jpg
Views:	229
Size:	69.8 KB
ID:	1899648

    Click image for larger version

Name:	IMG_7757ECS.jpg
Views:	222
Size:	120.3 KB
ID:	1899649
    21" Royersford Excelsior CamelBack Drillpress Restoration
    1943 Sidney 16x54 Lathe Restoration

    Comment


    • #3
      It took right at 27 minutes to get through the 1' thick aluminum. But the South Bend is under powered at 2 hp and wouldn't allow me to power feed even at the slowest feed rate so it was manual feed the entire way.

      Photos of the 1983 13" X 40" South Bend



      Comment


      • #4
        Wow, that's a nice one. Did you find her like that or did you have to go through it?

        One thing interesting I noticed (perhaps it was the cast iron) is that feeding it harder helped. I started at my normal parting feed, 2 thou per rev, but it was chattering something awful. Upon suspicious that it was too little feed I doubled it, and then went up one more notch. It still rang quite loud, but it was at least smooth after that. I didn't try to push it harder than that, the lathe was grunting pretty good.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

        Comment


        • #5
          How long would it take you to grind a trepanning tool and make this part if given a 6” X 12” X 1” chunk of 6061?
          Probably longer than it would take to 1) drill a maybe 3/8 in. hole, 2) thread a band saw blade through that hole and re-weld or silver solder the blade back together, 3) rough cut the large hole on the band saw, then 4) bore it to size on the lathe.

          Or maybe not, since I've never actually had to do it. However you got there, the final result looks great.
          "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979

          Comment


          • #6
            Originally posted by The Metal Butcher View Post
            Wow, that's a nice one. Did you find her like that or did you have to go through it?

            One thing interesting I noticed (perhaps it was the cast iron) is that feeding it harder helped. I started at my normal parting feed, 2 thou per rev, but it was chattering something awful. Upon suspicious that it was too little feed I doubled it, and then went up one more notch. It still rang quite loud, but it was at least smooth after that. I didn't try to push it harder than that, the lathe was grunting pretty good.
            I basically bought it this way except for a repair to the head stock pedestal, hence the off color South Bend gray.

            You ground a nice tool, well done.

            Comment


            • #7
              lovely looking work there nc5a! I've ground a few trepanning tools and there's always a trade off between length of tool (how thick a piece it will trepann) and width of tool, to get all the appropriate clearances. For my lathe (Atlas 618), about 2.5mm wide is pretty much all I can push, which limits length to around 15-18mm long. Any longer and they're prone to snapping, any wider and my lathe struggles with the cut.

              For cutting, slow RPM and high feed has worked well for me, much the same as parting to be honest.

              Comment


              • #8
                Thanks Matt.

                I set the spindle speed at 40 rpm, used a 1/2 can of WD40 and hand fed the entire 1". Very slow going. Any attempt at a constant feed and the lathe would stall. It's clear the tool was a bit too wide and the radius of the cut too large to expect much from the 2 HP lathe. The lathe doesn't have a problem parting with power feed but then the cut is usually within 1" radius of center line.

                Ron

                Comment


                • #9
                  Originally posted by nc5a View Post
                  Thanks Matt.

                  I set the spindle speed at 40 rpm, used a 1/2 can of WD40 and hand fed the entire 1". Very slow going. Any attempt at a constant feed and the lathe would stall. It's clear the tool was a bit too wide and the radius of the cut too large to expect much from the 2 HP lathe. The lathe doesn't have a problem parting with power feed but then the cut is usually within 1" radius of center line.

                  Ron
                  I feel like your belt is probably slipping. Or your motor isn't getting antiquate power. 2hp is not weak. I was only cutting mine with about 3.5hp, and it sounds like it went tremendously faster in a tougher material.
                  21" Royersford Excelsior CamelBack Drillpress Restoration
                  1943 Sidney 16x54 Lathe Restoration

                  Comment


                  • #10
                    Originally posted by nc5a View Post
                    Thanks Matt.

                    I set the spindle speed at 40 rpm, used a 1/2 can of WD40 and hand fed the entire 1". Very slow going. Any attempt at a constant feed and the lathe would stall. It's clear the tool was a bit too wide and the radius of the cut too large to expect much from the 2 HP lathe. The lathe doesn't have a problem parting with power feed but then the cut is usually within 1" radius of center line.

                    Ron
                    Something is not right.....

                    2 HP should do that job faster. I think I could do that in back gear on the Logan 200 with 1/3 hp in a similar time.

                    1) are you using a VFD to slow the spindle? I see the VFD and controls.....

                    2) have you cleaned any oil etc off the pulleys and belt recently?

                    IIRC, those machines have a 2" or so flat belt to the spindle.

                    When you slow the spindle with the VFD, you have constant torque corresponding to whatever speed you get at 60 Hz, so the power to the spindle is proportional to the speed. If you turn it down to 1/8 speed, your 2 HP turned into 1/4 HP, just like that . When you slow with back gears and lower speed belt settings you get torque that increases as speed slows, and basically constant power, so you would have 8x more torque, and keep your 2HP at the slow speed.
                    1601

                    Keep eye on ball.
                    Hashim Khan

                    Comment


                    • #11
                      Is the slug coming out of the middle waste? If it doesn't matter the width of the trepanning tool used then I think I would have found this a good candidate for a rotary table and a few passes with a 1/2 inch end mill. Just my thoughts. Of course, all this on the grand assumption that a rotary table was available. Nice looking finished part. Nice lathe too.

                      Comment


                      • #12
                        Metal Butcher and JT you guys called it. I got to thinking about the belt slipping and robbing power. So I cleaned the upper and lower cone pulleys and belt then adjusted the tension on the belt. She runs and cuts like there's 5 HP behind the spindle. I've had this lathe for about 3 years and other than oiling it religiously, putting a new belt on when I first got it and repairing the pedestal it's been trouble free. Always cut like a champ but to date I had never really pushed it until the trepanning operation.

                        Anyway good call guys.

                        JT there is a speed control rheostat but I rarely use it so I should have max power in every belt change.

                        Ron

                        Comment


                        • #13
                          Originally posted by nc5a View Post
                          Metal Butcher and JT you guys called it. I got to thinking about the belt slipping and robbing power. So I cleaned the upper and lower cone pulleys and belt then adjusted the tension on the belt. She runs and cuts like there's 5 HP behind the spindle. I've had this lathe for about 3 years and other than oiling it religiously, putting a new belt on when I first got it and repairing the pedestal it's been trouble free. Always cut like a champ but to date I had never really pushed it until the trepanning operation.

                          Anyway good call guys.

                          JT there is a speed control rheostat but I rarely use it so I should have max power in every belt change.

                          Ron
                          Nice, glad to hear. I've seen other SB's slipping badly so it came to mind. Do you remove tension when you leave the lathe to sit? I was taught to do that and have noticed it makes a big difference on my camelback in regards to belt stretch.
                          21" Royersford Excelsior CamelBack Drillpress Restoration
                          1943 Sidney 16x54 Lathe Restoration

                          Comment


                          • #14
                            I'll bet that was a time consuming job ! Somewhere I saw some supplier that sells rings of various thicknesses, OD's and ID's. Was there a local shop somewhere that could have laser cut it, or plasma cut it to save you all that time?? Just curious.

                            I'll bet you were cringing when you were getting close to breaking through. The last thing you would want is to break through and have the disc jam up between the ring and cutter and cause a crash. I've seen that before. I would have got myself a box of Depends before I started that job and doubled them up !

                            I have a trepanning tool but it has a spring loaded center to hold the plug in place. I still don't trust it.

                            JL...............
                            Last edited by JoeLee; 09-17-2020, 08:26 AM.

                            Comment


                            • #15
                              Metal Butcher:

                              My best guess is I remember to release the tension on the belt about 90% of the time. The times I forget are generally short periods like during lunch but there have been a couple times when the belt was under tension several days. I'll have to watch that more closely.

                              I didn't mention in the previous post what caused me to suspect a slipping belt. I was turning down the ends of 3/16" mild steel rod and I noticed a very slight change in spindle speed. So it was pretty clear then that something was slipping.

                              Of course now I want to do another trepanning operation to see how it does. But I have too many other projects in the works to take the time and basically waste material

                              Ron

                              Comment

                              Working...
                              X