Cast iron straight edge

  1. grim_d

    grim_d Unlikeable idiot.

    Messages:
    2,952
    Location:
    Scotland - Ayrshire
    I'd like to have a go at the scraping at some point and as such I'd like to start with making a straight edge.

    Commercial ones are much expensive for something to play with but I have a big chunk of cast iron bar, about 4 inches diameter and a couple foot long, I would imagine it's ductile.

    Is there any reason I couldn't turn this into a rough machined straight edge in anticipation? Make and screw a handle to it? Or is there good reason why they are cast the way they are and I'm breaking all the rules?
     
  2. eLuSiVeMiTe

    eLuSiVeMiTe Member

    Messages:
    12,445
    Location:
    Bedfordshire England
    I'm assuming all the ironwork above is to try and reduce the movement of the straight edge
    Lot of work to scrape one in to find next time you use it it's warped
     
  3. minimutly Member

    Messages:
    1,309
    Location:
    Pembrokeshire Wales
    Well here's one - in work we have a large sprocket - 2 ft in diameter, an inch thick. I'm not sure what it's made of, but it looks cast - would this be a candidate for cutting in half, or nearly half to make a straight edge?
     
    eLuSiVeMiTe likes this.
  4. Pete.

    Pete. Member

    Messages:
    9,490
    Location:
    Kent, UK
    I think that if you machine that round bar it'll move all over the place. I tried to machine a triangle from a piece of round cast and it bent like a banana.

    You could have it heat-treated to relieve stresses but the money you would spend would pay for a used straight edge.
     
  5. spencer 427 Member

    Messages:
    6,925
    Location:
    uk colchester
    Pressbrake a forum member might have a few straight edges left as he had some casted. I have some of them.
     
    pressbrake1 and mtt.tr like this.
  6. pressbrake1

    pressbrake1 Forum Supporter

    Messages:
    2,659
    essex england
    That’s lump of 4” diameter cast is worth quite a lot of money, selling it could possibly raise enough for a straight edge casting
     
    mtt.tr likes this.
  7. pressbrake1

    pressbrake1 Forum Supporter

    Messages:
    2,659
    essex england
    Been there, it takes several normalising runs and multiple cutting set up and as heat treat is between £1-£2 per kg it gets out of hand
     
  8. grim_d

    grim_d Unlikeable idiot.

    Messages:
    2,952
    Location:
    Scotland - Ayrshire
    Probably, but if it didn't?

    I've read that in ye olden days to stress relieve some cast iron they would simply rough machine then leave it outside for a year, then machine again and scrape in, any merit?

    He just sold the last one, it was the for sale thread that got me thinking.

    Did not think of that.
     
  9. Dragnet Member

    Messages:
    58
    Location:
    Cornwall, UK
    There was a video on making Colchester lathes I saw the other day. They left their castings outside to 'season' on stacks of pallets, before bringing them in to shotblast and mill down (after hand applying filler and wet sanding)...
     
Advertisements