New lathe project

Discussion in 'Other metal working projects' started by Petee716, Jun 27, 2018.

  1. Petee716

    Petee716 Silver Banner Member

    image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg I believe you're right OIF. There really shouldn't be much wear on them from the sliding action.
    I couldn't find any appropriate pins locally neither in brass nor steel and I didn't want to buy 50 from McMaster Carr but I came up with a bit of a hybrid solution using suggestions from OIF and Mark's castings. I found a thin walled brass tube 6" long in my 3/16 diameter. It was in the "miscellaneous shapes" drawer at Lowes. I found it while searching for pins. Anyway, a 10 penny nail fit inside it almost perfectly! Almost an interference fit but not quite. I was able to extract the roll pins by squeezing them one at a time in the vise and gently prying up on the shaft face without any damage. I sprayed out the hole with brake parts cleaner. I cut everything to the needed lengths and mixed up some JB Weld. If they were any closer I would have tried just using loctite but I figured epoxy would be more secure.
    I think we have a winner.
    I then set my sights on the back gears. As you may have noticed from previous photos, the handle is broken and the eccentric on the small gear end was hanging out of the casting. I have no idea what might have gotten the assembly into that state but the only thing that I could really find wrong was a missing woodruff key that holds the handle-side eccentric in position on the shaft. The groove in that eccentric and the pointed screw that prevents side movement of the assembly are present and in good condition so there's no telling what the previous owner was up to. By all accounts it should be fine. By the way, don't expect anyone at Lowes to know what a woodruff key is. They showed me all sorts of other keys, none of which goes on a shaft. I'm sooo disillusioned. Even the old men in the hardware store ain't what they used to be. I found it at ACE hardware.

    Let's see how the photos sort themselves.

    Can anyone tell me the purpose of the two segmented gear teeth.

    By the way, thanks for the suggestion guys. I hope I didn't let you down, lol

    Pete
     
  2. joe yard

    joe yard Silver

    Hi Pete
    The segmented teeth are a repair. The damage was dun when someone engaged the back gear without disengaging the pin to allow the chuck to free wheel. This is not an uncommon accordance it this type of back gear set up.

    Just a thought on the tool post and slide. Cut off the damaged part and keep only what is pictured. In the square use the flat that is left on the cut end. Use the slide flat end as a pattern to cast a L shaped cover say with the new dove tails that will mate up to the top of the original casting and wrap around the end. Bolt it to the face of the cut off portion with counter sunk Allens. All pressures is downward when cutting and the casting could easily be made of brass or bronze.
    Joe
     

    Attached Files:

    Last edited: Jul 9, 2018
  3. I was thinking today that you could get a feel for the relative shear strength of the various pins by getting two 24" by say 1" lengths of flat mild steel bar and drilling a 1/2" hole in one end of the bars and bolting them together so they touch but can pivot around the bolt using the bars as handles like a pair of pliers or tin snips would. Then you can open the "handles" apart and drill a pin sized hole through both bars at the same center distance as your lathe gears. Then various pin materials can be sheared and you can get some idea of whether it's going to be a catastrophic level of force. Also if you need brass pin material in a wide range of diameters, then a brazing rod from the welding shop should be an easy local source.
     
  4. Zapins

    Zapins Silver

    I am constantly amazed by how much the folks here on the forum know about fixing machines and tools. What a skill set to have. I don't know where you all learned how to fix these tools or where you get the confidence to disassemble a lathe and put it back together again and have it work. I took apart my sander and struggled to get the new bearings pressed on correctly, it still is sitting in my garage in a non-working state. My hat goes off to you.

    Maybe the school systems shouldn't have canceled shop class for budget reasons...
     
  5. oldironfarmer

    oldironfarmer Silver Banner Member

    It is common for someone to engage the back gear without disengaging the pin in order to lock the spindle for doing things such as taking the chuck off. It's a bad practice and overloads the gear teeth. So don't be tempted (directed to no one in particular).
     
    Hopefuldave likes this.
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    Guilty...
     
  7. oldironfarmer

    oldironfarmer Silver Banner Member

    :eek:
     
  8. Petee716

    Petee716 Silver Banner Member

    image.jpeg image.jpeg image.jpeg image.jpeg image.jpeg Yeah its too bad. I rarely think about the "character building" i received from the sports programs i was involved in when i was in school, but i use the skills and approaches to problem solving i learned in my shop classes almost every day. Of course learning how to beat others or how to get beaten has value although i cant really think of what. Gotta keep the kids fingers out of danger though, unless of course they're slow. Then you can ship them off to vocational.
    Dismount soapbox.
    That tooth repair looks pretty tidy, almost like it was meant to be there. The pin isn't exactly in mint condition either but it'll work. This machine has been banged more times than..., well never mind. I'll heed the advise on not abusing the back gears.
    So the apron reassembled nicely and I've moved on to the gears. I've got some reading to do. There was a stack of gears that came with it ranging from 32 to 46 teeth that are die cast, probably zamak, and they match my outer gears but they are the wrong shaft diameter. They are 3/4" but they can be opened up to 7/8" if I decide to use them. There are 2 other gears that match my inner gears and are the correct shaft diameter. One is 24 and the other is 80. The 80 has the same paint as the machine. The large inner gear currently on the machine which drives the lead screw is a 96. I'm not sure if the "inner" and "outer" gear trains are supposed to have different teeth or not. Like I said, I have some reading to do.

    Anyway, on to the highlight of my evening. While fiddling with the (banjo?) I tightened it down and the casting broke. You'll see it in one of the unsorted pictures. It appeared to be an old repair. It even looked like the original paint. It must have been ready to go because it gave way under very little force. It looks like I'll be an iron caster sooner than later.

    Pete
     
  9. Sounds like you have discovered all the bits that could have broken with one single crash: using the back gears to do a threading job at low speed, when suddenly the tool in the lantern holder shifted and dug in, snapped the compound slide off, sheared the pins and some gear teeth, broke the lead screw support all at once......although that is just speculation.
     
  10. oldironfarmer

    oldironfarmer Silver Banner Member

    I know they've got a bad rap, but I've never had a problem with a tool in a lantern holder. I could sure see it if the tool were set much above center, and you do have to check them.

    The back gear teeth are pretty strong since it is geared so low while in back gear. My belts always slip before I could damage a tooth by stalling the machine.
     
  11. I understand part of the problem with a lantern tool holder is that it's base it relatively narrow compared with a quick change tool holder so it's less rigid and more likely to flex while placing greater stresses on the base at the compound slide. Like you say, if someone accidentally sets the cutting point above center it'll rub without cutting and if the user increases the depth of cut to try and cut, it suddenly digs in and can crack the compound slide at the thin part of the casting. Personally I found a lot of issues with chatter and poor finish went away when I fitted a four way tool post to my first lathe and I just kept a tin full of various thickness shims to set center height for each cutting tool. I also love being able to keep up to four tools in the tool post and spin it round to 45 degree increments to machine different features and finally part off the item.
     
  12. Petee716

    Petee716 Silver Banner Member

    I have both qc tool holder as well as a lamp post for my SB 9. I only use the lamp post with the cutoff tool because i dont have the right tool for the qc. Of the tools ive used, the cutoff has been the most challenging. The learning curve has been hard on the machine and tools. I bought an indexable cutoff to go in the qc but broke it immediately through inexperience. Keeping everything as close and rigid as possible has been helpful. So has understanding the limitations of the equipment.
    I moved on to the countershaft. The drive pulley is badly bent and will be replaced but otherwise the cone and bearings are ok. Im quite certain the pulley was an arbitrary size so Id like to get an appropriate sized replacement. Does anyone know a rule of thumb i can use for a target rpm for the shaft? At this point i dont even know the rpm of the motor because the tag is covered by the power box and i havent gotten around to uncovering it yet.
    Fortunately im almost at the end of the machine and although the repair projects have mounted, i remain optimistic.

    Pete
     
  13. oldironfarmer

    oldironfarmer Silver Banner Member

    Is there a chart on the lathe that shows RPM for various belt positions? If you can find that, or copy from a similarly sized lathe you can work backwards to determine the required pulley (sheave) size. You need to check because that may not be a 1750 motor, but likely is. Spindle speed from a similar SB would be a good place to start.
     
  14. Petee716

    Petee716 Silver Banner Member

    image.jpeg image.jpeg image.jpeg I got the machine jiggled around to its final spot and started looking at the motor. More surprises. It is a 180V DC motor! Could someone explain how this gets plugged it to an AC outlet?

    I've got some work to do on the countershaft mounting position as well. How many ways can you say NO!?
     
  15. joe yard

    joe yard Silver

    You could build a simple DC power supply with a full wave bridge and a capacitor.
    The component cost would be under $15. This will work OK but have a fixed speed.



    It was most likely used with a dc drive. To vary the speed.
    Joe
     

    Attached Files:

  16. ESC

    ESC Copper Banner Member

    Pete, Surplus Center has 90/180 volt boards at about $90 that I have had good luck with. Your amp draw would require the heat sink, but being able to run variable speed is a joy. I use treadmill motors and for my lathe set up a separate switch so I could reverse rotation.
     
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  17. Petee716

    Petee716 Silver Banner Member

    Thanks for the responses. I saw this motor run briefly when I bought the machine and I think it was just a regular 220v outlet, so it had most recently been run this way. No on/off switch was wired in. Just plug and unplug.
    As seen in the picture above the input power is wired into 3 bridge rectifiers and then just run into the motor. You can't see it but some of the white wires are brownish, presumably from the heat, but there is no other discoloration and all of the insulation is still pliable.
    Because of the current configuration of the countershaft/motor mount , this is not going to be a plug n play situation like I'd hoped, and since I have to modify the mounting anyway I'll probably be opting for the treadmill motor as an alternative. I've used them in other applications and it would be a great alternative for a number of reasons. Plus I have no great attachment to the DC motor that's on it now.
    However, that 180V DC motor isn't junk as far as I know. So the question of the hour is, if I decide to use that motor for a different application at a different time, is the present wiring setup safe to just plug into a standard 220V outlet? It doesn't seem like the power conversion should be quite so simple.

    Pete
     
  18. joe yard

    joe yard Silver

    If used with a bridge rectifier and no filter capacitor. The 220 is just a bit high at 200 +/- and if run off 120 with a capacitor. It will be a bit low at around 160 with no load and will drop a bit in use 150 +/-.
    Joe
     
  19. Petee716

    Petee716 Silver Banner Member

    Yes, I believe that's what I have now.
    Thanks!

    Pete
     
  20. crazybillybob

    crazybillybob Silver Banner Member

    If I remember my motor ease it's like a 10%-20% fudge factor on power input on those. So it should be ok as long as it's got good airflow.
     

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