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  1. Quote Originally Posted by CheekieMonkies View Post
    Any advancments ?
    Not so far, family things got in the way yesterday :( and its too windy outside today to do a pour.. cant even keep the burner alight! And i dont want to do it indoors there's nowhere to run if it goes wrong! So I'm installing the 3phase motor and tidying up wiring...

  2. #52
    Quote Originally Posted by irving2008 View Post
    A proper mill - something that'll take a couple of cubic inches out of a casting in a relatively short space of time...
    Hi I’ve got a mill and travel from north down to Kent fairly regularly M6, M1, M25, A2M2

    Would you be interested in me doing some machining?

    Kevin
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by keebo; 23-06-2008 at 07:01 PM.

  3. Quote Originally Posted by keebo View Post
    Hi Iíve got a mill and travel from north down to Kent fairly regularly M6, M1, M25, A2M2

    Would you be interested in me doing some machining?

    Kevin
    Kevin, Thanks for the offer. I'm going to look at a short term fix first but will come back to the milling out option if that proves unsatisfactory.

    Nice mill btw...

    regards,
    Irving...

  4. Well despite my best endeavours nothing got done the last 2 weekends mainly cos of family things but the weekend before last was just too windy.

    Anyway, was going to do it this weekend. Got it all set up and then decided to DTI the spindle from the slide and see how parallel to the ways it was. The end result was it was 0.15mm out in 80mm, but I couldnt decide if that was the tailstock being out or something else. As you will recall from a previous post i am holding the chuck end of the spindle in place using an MT3 deadcentre located in the centre hole of a JT6/MT1 arbor held in the tailstock. But the tailstock wouldnt normally be at that end of the bed so i cant tell if the error is due to the tailstock, the centres or something else...

    So I decided to order an MT3-MT1 sleeve and an MT1 parallel test bar. The plan is to hold that in the spindle and locate the far end on an MT1 centre in the tailstock. That way the bar will better show the true direction of the spindle over a 300mm length and will allow me to DTI it from the slide more accurately.

    The runout on the reground spindle is impressive. It doesnt even move the needle on the DTI so better than 0.0025mm!

    Hopefully next weekend!

  5. Well i ordered the taper sleeve and test bar from RDG on Sunday eve, shipped out to me Monday, arrived this morning. Test bar wasn't as long as I expected, 100mm not 300mm :( Anyway, I fitted it all up for a trial and with relatively little adjustment was able to get 0.02mm across an 80mm traverse with .01mm runout on the taper sleeve. Quite pleased with that (<0.01degrees taper), so no more than 0.1mm out (4thou) over the full bed traverse. So will set it all up tomorrow night (and try to remember to take some pics) to give it time to dry for the weekend...

  6. well sods law prevailed... I decided before I finally did the pour that it might be a good idea to check the tailstock to spindle relationship when the lathe was actually bolted down and level... well suffice to say the relationship was far from level in the horizontal plane and when the lathe was bolted down and the spindle actually level the good parallel I'd measured went out the window. Eventially after much measuring and cursing I discovered that the lathe bed is twisted and needed packing about 3mm on two opposite corners when I bolted it down. This means I will have to pour the bearing with the lathe bolted in place to the bench. Once bolted down and leveled I then found the saddle would stick badly at a couple of points so I removed all that and cleaned it up, refitted and readjusted the horizontal and vertical gib strips. I also tightened up the leadscrew preload to give 4thou clearance and discovered a hitherto unknown screw that tighens the clasp-nut onto the leadscrew, which allows a modicum of backlash removal. Now it all runs much smoother than before if somewhat slightly stiffer than I would like... taper now measures 0.04mm in 80mm but its more consistent and doesnt vary with saddle travel direction. I also discovered that the tailstock has an adjustment underneath so I'll take the final taper out once the lathe is up and running.

    By the time I'd done that on Saturday there wasnt time to do much else and today was a washout (literally and metaphorically) as family things got in the way again...

    Hopefully next weekend...

  7. Well a weekend came and went... but today I managed to get the day to myself, as SWMBO went shopping with daughter...

    So rechecked everything, was still as I'd left it 2 weekends ago. I'd already decided that the main problem before, primarily, was not enough heat in the bearing housing so the metal set too quickly. So I wrapped the whole lot in loft insulation and pointed my 500W heat gun into the centre and left it to cook for 30min. That got it nice and hot. Unfortunately I didnt take any pics cos my camera battery was flat and I couldn't find one of the kids. Anyway, melted the metal, skimmed the slag off the top (using a bit of wood, not metal apparently is good practice) and proceeded to pour. Now being on my own (which prabably wasnt a good idea) I was trying to hold the heat gun in one hand and the ladle in the other so as to keep it all hot as it went in... this worked but it was impossible to pour slowly as I had intended and some 'missed' the hole and ended up on the drip tray. But the two vents seemed to work and hot metal bubbled up all three holes at the same time...

    Left it to cool, by which time son was home and found me his camera. So banged the spindle out with a rubber mallet... its a tight fit.. i found a quick reheat helped to release it...

    took the first 'dam' off...



    Well that was looking good... but wait a mo, whats that down in the RH corner... took the other dam off.... :(



    bu***r, almost got it right... oh well set up for another go...



    Dont' know if that problem was lack of heat down there, or an airlock. So for next time (tomorrow hopefully) I'll put a couple of additional air vents down there... like this... note I'm only using the firecement to form the vents. Standard bathroom silicone selaer is all thats needed to fix the aluminium sheet 'dams'... it stands 380degC no problem...





    more to come tomorrow hopefully...
    Last edited by irving2008; 23-11-2009 at 11:50 AM.

  8. Quote Originally Posted by Kip View Post
    Looks like a partial fill Irving :(
    Thanks Keith for that deep insight :D...

    Ok, so the story continues...

    Here's some pics of the heating arrangements...hot air gun and some rockwool...





    Note the cute funnel (made out of ally) to try and avoid spillage. Oh and did I show you my VFD install on the wall behind (RH side pic 2)

    So... heat it all for 30min (till it all too hot to touch) while melting the metal in the ladle and pour slowly using both hands this time...

    and leave to cool....



    Well it clearly filled to the top on both sides and in the centre... and a probe with a scriber in the smaller vents shows there's metal in the bottom of the upper vent... but nothing in the lower :( ... oh well nothing to do but remove the dams and have a look...



    this side looks OK, note the slot caused by a shim in the bearing housing slot... that worked well and made it much easier to get the spindle out... nice clean bearing surface from this side...

    but OMG once again a failure from the other....



    it can't have been an airlock so I can only assume it wasnt hot enough and the metal solidified too soon - you can see there is a nice curved flow edge. Also note the nice clean edge to what would have been the 'slot'.

    Clearly I need to find a way to get the lower half of the cavity hotter, but I'm getting closer and I can see this will work eventually...

    just takes a good hour to chop it all out again and another 2 or 3 to line it all up and prepare it and then 24h to leave it to dry (even with a 10min blast from the heat gun)... so next attempt will be next weekend as I wont have time during the week.... :(

  9. #59
    What can I say? Nemo repente sapit, your perseverence is amazing :D

    The problem may be asking the metal to go all the way around and then rise to fill in below the slot. Perhaps is you added a channel on the ends so it could go around the slot ends so everything flowed downhill, or, up ended it and put a fat sprue over the slot with a diametrically opposed vent?

  10. Keith/Robin

    Thanks for your comments.

    I am not entirely sure I understand your point Keith, I don't think its an airlock issue as there was plenty of room for the air to come out, I am pretty sure its a heating issue, thats the furthest corner from the fill.

    You will note in the previous attempt (which didnt have the shim all the way into the spindle) that that side filled OK but the other side failed. I am wondering if the best option is to have two fill points, one through the top and one to the side to fill from the bottom up initially and then from the top.

    Keith, your casting experience is far greater than mine and this is clearly a 'casting' problem so I am grateful for your thoughts. I am a little loath to heat the metal a lot more as I have read that overheating causes some of the trace elements such as antimony and bismuth to leach out, but I don't know how hot that means - I cant get anywhere near hot enough to boil it!

    I will persevere... it will come right one day...

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