Drill press restoration - Zapins

Discussion in 'General foundry chat' started by Zapins, Dec 19, 2021.

  1. Yep, this is a budget drill press being bought up to spec, not your latest invention to save mankind/make big dollars. Or as one guy said after seeing my drill press efforts: "Gold plating a coprolite".
     
  2. Zapins

    Zapins Gold

    Haha true.

    Although replacing all the worn out bearings with quality bearings has been pricey too. Getting close to $80 on basic material costs so far.

    I got most of the paint work done. Just a couple more to do. The down side is that the angle grinder with wire wheel got me good. Flicked out of my hands and nailed me in the shoulder. A nice rug burn.
     
  3. I've been nailed by a 3" cup wire wheel in a 5" grinder before, I was running it right on the maximum speed limits and it was shedding wires occasionally. Even wearing jeans, safety glasses and a full facemask: I was showering and saw blood in the shower from a wire to the nutsack. A welder in the neighbouring workshop even had a swelling on his inner thigh and X-rays showed a fragment of wire made it into his circulatory system before jamming further upstream and needing surgery.
     
  4. Zapins

    Zapins Gold

  5. It's coming along nicely, I found with hammertone, it needs a coat of primer underneath or a second coat as I'm getting rust on the metal forming in the low spots of the hammertone texture. That's a nasty wound, fortunately it could have been in a worse location. There was a local eye surgeon who said the most common injuries were caused by cheap bungy cords and hand held wire brushes. That motor sounds like it has a centrifugal switch inside for starting?.

    As for the grease, black molybdenum disulphide needs a high crushing force to function, like rollers or balls with a high force loading or it can damage bearings in high concentrations...there's a reason they only add 2% or so to grease. Teflon is made as a powder before rolling or extruding into sheets or bar and again, too much in a lubricant and it can roll or extrude into stringy masses that jam gears and things.

    Plain old lithium soap grease, literally soap made from lithium hydroxide ( a mild alkali) and used to thicken oil is all you really need to handle the job. Not to mention it's cheap too.
     
    Last edited: Jan 1, 2022
  6. Zapins

    Zapins Gold

    Why temper twice? Whats the purpose of the 500f one? Wouldn't raising it to 1000f undo the temper from the 500f ? Couldn't I just do one temper st 1000 f?

    I'm heating up the kiln now. Going for broke! Hopefully the kiln works haha. I've never used it before (the big one I snagged for $50)

    20220103_181627.jpg
     
  7. Zapins

    Zapins Gold

    Ughhhhh I'm heating up the kiln for the first time looks like the top 2 elements are dead or are not connected for some reason. Ughhhhleee. Will need to dig into that later. Testing to see how hot I can get the kiln without all 4 elements going. Hoping I can hit 1550 and be done.
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    The purpose of the first 500 heat is just good practice to not chill parts to room temp after quenching so that the piece does not crack----never had that happen, but all the authorities say it is good practice. Your kiln would be too hot for an hour or two most likely. So, after you temper at 500 you can do a final temper to 1000 whenever you want. Double tempering is also recommended at the target temp (1000 in your case) as an ideal practice. I don't usually do that. All this stuff (and more) is in Bryson's book I mentioned above. There is a decent chance your local library has a copy.

    Too bad about the kiln. Just when you were ready to give it a go. :(
    Denis
     
  9. Zapins

    Zapins Gold

    So the good news is that the elements work i just didn't turn the knob the right way.... :)

    I was planning to leave the lid open in the kiln to fast cool it to 1000f during the quenching then putting it into the kiln for the 1000f so I can eliminate the 500f step. The furnace is all light fire brick so it has very low thermal mass.

    I'm a bit concerned about the oil quenching. I have a steel black pipe that isn't much bigger than the rod I'm quenching so I'm a bit worried it will explode. I will probably just throw it in and run. If it doesn't go off like a bomb I'll come back and swish it around a bit. How cool do I get it before stopping and doing the 1000f?
     
    Melterskelter likes this.
  10. Zapins

    Zapins Gold

    Also how long do I leave it at 1000f and do I take it out and let it air cool? Or do I leave it in kiln to slow cool over night? Do I quench it again with oil after the 1000f?
     
  11. Melterskelter

    Melterskelter Gold Banner Member

    You need more oil than that and if it is close to the same size it might burp. But, you HAVE to have enoughg oil to cool the metal rapidly or it will not harden. So, for what you are doing, I think you need a half gallon minimum. Other wise you may heat the oil to 1000 F itself---and that might get interesting from a combustion standpoint. And you do not throw it in and run. It must be vigorously aggitated. Otherwise, a layer of vapor will cover most of the rod and heat transfer will slow.

    I would reread my prior suggestioned procedure:
    "So, before you machine them (so you do not later harden them and induce warpage) put them in a kiln and heat them to 1550F and hold them there for a half hour (you could hold them for 90 mins to do this all according to "the book") and then fish one out with a large plier or tongs and dunk the bar quickly into a about a gallon or more of oil---canola or veg works fine as does lubrication oil. Best done outdoors as a fair bit of smoke will be generated. Also expect that vaporized oil (smoke) to catch fire. (welding gloves will be nice) No biggie. It wont last long. Vigorously aggitate the bar in the oil with an up and down and side-to-side motion. In a minute or less it will no longer be glowing or smoking much and you can just let it rest in the oil and let it cool. Pull it out of the oil and stick it in the oven you preheated to 500 and temper it in the oven. That will only take it down to Rockwell 50 or so. So you will want to retemper at 1000F to lower it to 32 or so. Use the kiln for the second temper. But it will be too hot to just temper immediately after quenching. Thus oven first and then 1000 in the kiln."

    As far as how long to temper---the part will take some time to soak through to 1000. So for a 1 inch part I'd soak it for an hour. Then pull it out and let it cool in the air. You could quench in oil or water. Not really needed. Then test with a file or drill bit. It should cut.

    You quench container could just be an ordinary galvanized garden bucket. Cheap. Large enough volume. Room to aggitate.

    Denis
     
  12. Zapins

    Zapins Gold

    Well ugh. I'm not sure if this is going to work with what I did then. I put about 0.5 liters into the pipe and then dumped it in. Ran back away and saw only small fire like you said then came back and vigorously shook the pipe and the rod inside it around. Then put the first rod into a ceramic fiber blanket and did the 2nd rod with fresh cold oil then put the first rod into the kiln at 1000f. I turned the heat down and have got it around 1000f to 1020 f and am maintaining it by burping the kiln and lowering the temperature.

    The oil got pretty hot by the end and was roiling a bit. But the glow if the metal disappeared almost instantly so I'm hoping it quenched it fast enough?

    The rods have a black burned exterior and I've got them in the kiln at 1000f now.

    Just reread last post and saw how to finish the process. I will air cool the rods then. Less messy with oil.

    I will need to see if I can get some hardness testers to see what I got. Will the metal be evenly tempered through to middle or just case hardened/tempered?
     
    Last edited: Jan 3, 2022
  13. Zapins

    Zapins Gold

    I'm done with the annealing process. The temperature range over the process was 980-1040f and time at the extremes didn't last long, maybe 20 seconds or so. Not sure if the heat transferred to the inside of the metal rods. I think it went ok?

    I have taken the rods out of the kiln and have them cooling now.

    They are still hot af but a file does file them so its not super hard at least. No cracks either.

    20220103_222535.jpg
     
    Last edited: Jan 3, 2022
  14. Zapins

    Zapins Gold

    Also I think I found my next restoration project after I finish the drill press:

    I noticed that the temperature readout on the kiln is about 200f less than what my thermocouple reads. Pretty interesting. Unsure why that is but ill have to sort that out at some point. I wonder if I can calibrate the analog temperature meter?

    20220103_230623.jpg 20220103_223128.jpg 20220103_230653.jpg
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    Maybe they will be moderately hard. That is all you need.

    If they are not, you can redo it perhaps following recommended procedures more closely which will virtually assure hardening. Finding some way to test them would be great. I have done enough that I can get a general idea by using a center punch on a soft piece of steel and whacking it with a hameer and then whacking the hardened steel with a similar blow. The divot will be smaller if the steel hardened. That is a very gross test. Actually, I use my Wilson 3Jr hardness tester which is calibrated and accurate. If you send me a coupon of steel---cut 1/4" off the end, I will test it. Maybe someone near you has a tester or a set of hardness testing files.

    Another gross test is to just chuck up the hardened bar in your lathe. It should turn with a very nice finish if moderately hard and cut with more resistance than a dead soft piece of steel. And drilling it should show evidence of greater hardness on the hardened steel.

    Try to get it objectively tested.

    Following proper recommended procedure is very reliable and predictable with respect to hardening and tempering 4140 or 4130.

    Denis
     
  16. Chazza

    Chazza Silver

    A simple hardness tester which can be made at home, is the shore scleroscope. The scleroscope is a comparative-hardness tester.

    The one I used, was a glass tube fastened to a vertical wooden post, with a scale inscribed on the post - a ruler would work perfectly. The tube could slide in its fasteners so that the sample to be tested, could be placed under the tube and also touch it. The samples were filed and sanded smooth and were the same thickness.

    Into the top of the tube was dropped a steel ball, which rebounded and the height it bounced to, was recorded. In this way, we students could understand quickly how much harder tool-steel was than mild steel, or brass, or aluminium, etc.

    When hardening and tempering 4140, it could be a useful test to help one understand the changes between fully-hard and all of the colours on the tempering chart,

    Cheers Charlie
     
  17. Melterskelter

    Melterskelter Gold Banner Member

    Similar in principle to a Leeb hardness tester. But the Leeb measures the velocity of rebound of an impactor. The impactor passes through a coil and generates a voltage dependent on the velocity. I have one. Very handy for parts not easily placed on a standard bench hardness tester.

    https://en.wikipedia.org/wiki/Leeb_rebound_hardness_test

    Very handy is the fact that the impactor can be oriented vertically, 45 deg, 90 and 180 from vertical. Some limitation too. But a great tester IMHO.

    Denis
     
    Chazza likes this.
  18. Zapins

    Zapins Gold

    Hmm weird. I got the bars tested at a local machine shop. One bar is about 45 one is maybe 42ish? Im not sure why they aren't 32. Maybe my temperature was off somehow. I will try calibrate my thermometer again.

    Is the 42 rod too hard to machine with carbide inserts? Or too brittle to be a proper shaft? Will it be less hard the deeper in I cut?
     
  19. crazybillybob

    crazybillybob Silver Banner Member

    You should be able to turn 42 RWC with carbide. As for the hardness at depth?? Depends on if it's a proper hardened shaft or just case hardened. Things like Hydraulic rod have a hardened chrome layer on them if you can get under that they turn easier. But a hard dowel pin will be hard the whole way through. Is 42 too hard for a proper shaft. Depends on the alloy if it's something like 4140 not really. Only way to know for sure is try it..
     
    Melterskelter likes this.
  20. Zapins

    Zapins Gold

    Well I made sure to heat the rod thoroughly through and through so I'm hoping the changes go deep.

    As long as I can cut it on the lathe and it won't shatter when used as a shaft then I'll give it a go and see how it "turns" out.
     

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