First iron melt - Real time

Discussion in 'General foundry chat' started by Petee716, May 25, 2020.

  1. Ironsides

    Ironsides Silver

    Congrats on your successful iron pour! It is a great feeling to move to the next level from bronze. All you need to do now is to get the feel for when your furnace it the hottest and every melt after that should fill up the mold. My biggest problem when I started to melt iron was to understand what hot iron looks and feels like.
     
    Tobho Mott likes this.
  2. Petee716

    Petee716 Gold Banner Member

    Thanks for the kudos and encouragement!
    I made some headway machining the link arm. I found and internal inclusion, I'm assuming slag. I ran into it while cutting the slot. The endmill survived it but it's not my best one anymore.
    I just have to drill for the cinch bolt and cut the kerf.
    Boy, cast iron machining is a new experience. Messy. I had a bit of a issue boring the hole. I use a boring head with brazed carbide boring bar. Cheap Chinese kit, but not bad as far as I can tell. I drilled the hole to 1" diameter and bored it to 1.628 nominal. I say nominal because I had an accuracy issue. Here's what I mean. It's the first time I've used the tool so I figured it out. I used 375 ft/min per the Machinerys Manual and inserted the tool into the center position with the insert at what looked like the proper contact position. I began to bore and found .020 to be a good depth of cut without chattering. I proceeded until it seemed appropriate to move the tool to the off-set hole in the boring head. I only had a few more passes to go and I started noticing vertical lines in the cavity. I didn't really feel anything different and didn't realize that the effect was more than just visual until I was within about 3 thou. I'm thinking that it was from the angle of the tool. The pictures show the hole when the tool was in the first position on the mill, and then the final result on the table. 20201013_214450.jpg 20201013_230459.jpg
    Hopefully its visible.
    So in the end, the hole fits on the 1.625" shaft, a couple thou more than I was shooting for, but although I wouldnt sell the part, it will be perfectly serviceable.

    Pete
     
  3. crazybillybob

    crazybillybob Silver Banner Member

    Pete,
    Open the slit up an extra little bit and put an extra 1/4 turn on the pinch bolt you'll be fine ;)
    Nice work Sir!
     
  4. Petee716

    Petee716 Gold Banner Member

    I've been working on finishing the compound on the mill and discovered a pretty serious set of defects. It turns out that a few of the holes on the surface are merely openings for some pretty large internal voids. A few of them end up being at in unfortunate locations. Initially I knew their depth by probing but I had no way of knowing their volume until I started removing material. If I knew 2 weeks ago what I know now I might have scrapped the part but by the time I discovered the extent of them I had already spent a number of hours with it on my little Clausing mill. Initially I thought the defects were a result of the slag that can be seen entering the mold in my attached pour video but it's been pointed out to me that it may have been caused by solidification shrinkage and an ineffective feeder. The cavities are rounded and smooth inside, not jagged, so that seems like a better explaination. I've attached pictures showing the gating system along with a picture of the mold. As I noted before there is no sign of piping on the feeder on this casting whereas there is significant piping on the feeder of my other casting shown on the previous page. I thought that may have had to do with the slag evidently entrained in the feeder, but it may just be because it froze off. I didn't come across any recognizable slag in the casting. It may have all been caught in the feeder. I'll cut a cross section of the feeder and take a look at it.
    I made an attempt to braze the holes before finishing the dovetails. I'll post pictures later.






    image.jpeg image.jpeg image.jpeg
     
  5. dtsh

    dtsh Silver

    I realize this is heresy on a casting forum, but unless you need to tap thread in that particular spot I'd probably fill it with an epoxy and move on.
     
    Petee716 likes this.
  6. Melterskelter

    Melterskelter Gold Banner Member

    Agree! If a brazing attempt is made, chilled iron may result. That is sort of how flame-hardened iron for lathe ways etc. are made.

    Denis
     
  7. Petee716

    Petee716 Gold Banner Member

    +1 You and I are the same kind of heretic.
    After taking reference passes and roughing cuts on both the top and bottom of the part I had exposed a majority of the damage. I got into each one with a ball end burr to clean them out, spent about 15 minutes slowly preheating the entire part with an oxy/propane torch and commenced to filling with braze rod, meanwhile trying to maintain heat to the rest of the part. When I was done I buried the part in dry sand and left it overnight. Subsequent finishing showed no warpage (my main concern at the time). Whether the procedure resulted in chilled iron I don't know. What would be the symptoms?
    I proceeded to do the finish milling on the flat part of the ways and then cut the dovetails. This exposed areas of my repairs as well as a couple of small areas that didn't fill completely so I packed them with JB Weld. Once the epoxy cured after a couple of days I did the final passes. I started cutting the slots for the t-nut last night and have a little more work to do with the epoxy after I finish that up today. I'll post pictures when I get it off the mill.
    I've spent a lot of hours with this part on the mill. I can assure you I will be casting my parts closer to net size next time!

    Pete
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    You did all the right stuff to avoid chilled iron. Had you chilled the iron, you would not have been milling it without great difficulty. Chilled iron is very very hard—- Rc60 or greater. So, good for you!! I imagine some pics will appear before too long.

    Denis
     
  9. Petee716

    Petee716 Gold Banner Member

    Well here it is. I have to clean the oil back off it and get the surfaces smoothed and painted so it's cleanable, but it seems to do the job.
    Although I really wanted to stick to the original specs I made some changes. I made the cross section of the base of the t-slot 1/8 thicker and I shortened the leadscrew channel by 1/4". That raises my tool center by 1/8" and may require milling my tool holders to get back to the right height but that doesn't bother me. If I get a quick change toolpost,the adjustability should make it a non issue. I also had to trim 1/4" off the leadscrew resulting in less backward travel, but I think it's worth it. The original design had the screw channel terminate just short of the t-slot on the other side which is exactly where the other one broke. I think that modification will pay off because that botched-looking braze job in the t-slot is filling a hole that goes all the way to the back and required three 18" braze rods to fill. There's a real possibility that the brazing was ineffective, I don't know, so I'll take whatever I can get at this point.
    The gib adjusted up ok. The screws are original but the center one isn't acting quite right and all of them seem like they may be at the end of their travel, so I'm hesitant at the moment to touch the dovetail on the base. I'll make sure the threads are cleaned and maybe chased through the casting, but I'm pretty well ready to call this done. There are more things to deal with on this old mule so it's time to move on. At least it's cutting now.
    So, these were my first real iron castings. I consider it to be a reasonable success. It's been a real adventure and I'm looking forward to doing it again. A few things I'm taking away from the experience:

    Get closer to net size. This was a big job for my little mill.

    Get my furnace temperature dialed in to max heat

    Machining cast iron is very unglamorous. I'll be spending most of today thoroughly cleaning the mill and surrounding area.

    image.jpeg image.jpeg image.jpeg image.jpeg


    Pete
     
  10. Melterskelter

    Melterskelter Gold Banner Member

    Wow, having this job done must be a relief. Well done.

    Given the location of the defect on an inside corner in an area of the casting that should solidify late in the game, I am nearly certain that what you have are shrink defects. Were you to do this again, a riser in that area would likely solve the problem.

    If at some point you want to really optimize the compound function, scraping the mating vee-ways might be an interesting exercise. I did scrape in my compound and was rewarded with improved rigidity especially noticeable when parting and taking heavier cuts. But learning to scrape is a whole ‘nother skill set and big time investment.

    Denis
     
  11. Rotarysmp

    Rotarysmp Silver

    Congratulations on your first sucessfl iron castings. It it a pretty big jump up from Al or copper based alloys.
    Mark
     

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