1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. PLEASE: Read the FORUM RULES BEFORE registering!

    Dismiss Notice

Adding A Column Riser To A Solid Column Mini-mill: Lots Of Questions

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by TIGL, Sep 28, 2015.

  1. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    Pretty much what it says in the subject: I keep running into problems with a lack of of Z-axis height on my SX2 and I thought this would be a good thing to try after seeing that they're fairly common on b-port machines. I found this thread on another forum and am interested in giving it a shot. The two things I'm wondering most about is what material to use and how to finish the top and bottom faces for maximum parallelism. My current plan is to get a 2x3x12 inch piece of gray cast iron from mcmaster and chop in in half and make a pair of 2x3x6 spacers. I can use one or both to get 2 or 4 inches of rise respectively. Is cast iron a good choice for this? Would something like cold rolled steel be better? If the cast iron block is not flat enough to begin with, could I face the top and bottom with a fly cutter and get sufficient accuracy? Also how tough will it be to drill 4x holes for M8 bolts in CI? I'm worked almost entirely in aluminum up to this point. Would this mod completely kill what little rigidity this machine has already? Should I be worried about stripping out the threads in the base casting if I go a little overboard on the tightening?

    Thanks!



    Relevant picture from the linked thread:

    33e43394f97651766b78bff844994343.jpg
     

    Attached Files:

  2. Cobra

    Cobra United Kingdom Active User H-M Supporter-Premium

    Likes Received:
    350
    Trophy Points:
    63
    Location:
    Moncton
    City:
    Moncton
    State:
    New Brunswick

    -Return to Top-

    Cast would be a better choice than CRS. Much more stable.
    I would decide how much lift you want and do it once. Changing the spacers would be a continual pain in some portion of your anatomy.
    As far as stripping the threads in the base, have a look at the recommended torque for the threads in the base material and use a good torque wrench.
     
    brino and Bill C. like this.
  3. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

    Likes Received:
    2,604
    Trophy Points:
    113
    City:
    Barneveld
    State:
    Wisconsin

    -Return to Top-

    Grey cast is fairly easy to machine. There are multiple warnings about cast iron chips though. Most machinists protect the surfaces from the machining swarf as it tends to chew up any sliding surfaces.
     
    brino and Bill C. like this.
  4. Bill C.

    Bill C. United States Active User Active Member

    Likes Received:
    152
    Trophy Points:
    63
    City:
    Clarksville
    State:
    Indiana

    -Return to Top-

    Cover the ways and table with heavy paper or use a strong shopvac. With any casting you need to take at least enough material off to get a clean flat surface. Use a carbide cutter to mill CI. It tends to crumble instead of cutting chips. Sometimes a edge can chip off if the cut is to heavy. Don't use any cutting fluids.
     
    brino likes this.
  5. Bill C.

    Bill C. United States Active User Active Member

    Likes Received:
    152
    Trophy Points:
    63
    City:
    Clarksville
    State:
    Indiana

    -Return to Top-

    I can hear my Dad say torque them like head gasket bolts. Start by snugging the front left bolt then the right rear one and so on.
     
  6. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

    Likes Received:
    1,356
    Trophy Points:
    113
    City:
    Riverton
    State:
    New Jersey

    -Return to Top-

    Machinable cast iron would be an excellent choice yet messy, mill the non-mating surfaces to size first as these features are simply clearance for the rest of the machine components. Mill the mating surfaces leaving .010-.020" of material on each side for finishing, drill through in 2 places where no other holes will be located then counter bore each face for socket head cap screws.

    Clamp a piece of material onto the table leaving enough room to fly cut a spot large enough to hold the part without hitting the clamps. Fly cut this plate in place then drill and tap it for the size holes that you put in the part. Bolt the part down and skim one side, flip it over and skim the other side to dimension, do not remove the fixture between steps. This is about a accurate as you may achieve on a mill much like grinding a magnetic chuck face on a surface grinder in place. You have created a reasonably flat parallel surface relative to both the X and Y axes. Also the hold down screws do need to be very large as this is a finishing operation so the cuts should be very light (-:
    Use clamps on 4 sides of the fixture if possible as removing material from one side will often cause CRS and some aluminum flat products to move a good deal.
    Like so millinplace_zpsvorrpqen.jpg
     

    Attached Files:

    Bemac50 and T Bredehoft like this.
  7. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    I'm thinking I'll put both in and leave it like that unless the hit to rigidity is too serious. I'm sure I can borrow a torque wrench from the maintenance shop

    They ways have rubber accordion covers, would not be enough? I plan on using the shop vac as well if needed. I'm not sure if the bar stock I'm getting is a raw casting or if its been saw cut to size already. I would guess that its been cut to size already but I'm not sure. If it's the latter it will already have a decent surface finish but I probably would do better to try and improve it. I'll be ordering a left handed turning tool with carbide inserts to put into my fly cutter so that I can use that for surfacing. that way I can crank up the spindle speed and not have to hand crank my table for 2 hours to get a good finish.

    Thats the plan

    That a very good idea for maximum accuracy but I'm not sure if my mill table is big enough for that big of a production. I think I will try to to face the blocks either in the vice or bolted to the table normally first and if I can't hold the modest tolerances I'm usually going for I will go back and address it using your method on the bridgeport they have at the local makerspace.
     
  8. Andre

    Andre Active User Active Member

    Likes Received:
    577
    Trophy Points:
    113
    City:
    NY
    State:
    New York

    -Return to Top-

    Grey cast iron is very easy to machine.

    Look up specs and use a torque wrench as stated above. As far as I know, once you get close to the yield point of bolts they actually loosen up.
     
  9. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    Got an email back from McMaster and apparently it's just a raw casting. Hopefully getting under the hardened skin of the CI won't be too horrible.

    Looks like the max torque for grade 12.9 M8 bolts is 27 ft-lbs so I'll probably shoot for 25. BTW i'm talking about the threads in the existing mill base which I assume is also cast iron. Thanks for everyone's help so far, any additional input anyone has would be welcome since I'm so new to this material
     
    brino likes this.
  10. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

    Likes Received:
    1,356
    Trophy Points:
    113
    City:
    Riverton
    State:
    New Jersey

    -Return to Top-

    One may also clamp a flat piece to the table by drilling, counterboring and clamping it down with socket head cap screws and T-slot nuts, then skim the surface, drill and tap and then screw your part down. It does not need to be any bigger then the part itself, if you have the Z clearance to do it in a vice then there is certainly room to do it screwed to a sub 1" high fixture on the table.
    This sort of simple flat fixture may be reused many times, simply bolt it down to the table and skim it again, drill and tap new holes for the new part and have at it.
    Good Luck with your project.

    If one is overly concerned about accurately "tensioning" threaded fasteners a torque wrench is about the least accurate method (aside from a large handheld non-torque wrench) yet the only method available for general work.
    For those hobbyists suffering from crippling OCD about accuracy , Rotabolt as well as several other manufacturers such as Maxbolt™ make exactly what you seek. However you will not be at all happy with the cost.
    http://www.rotabolt.co.uk/how-it-works/
    Maxbolt https://www.vfbolts.com/product/maxbolt-load-indicating-fastener-system/
     
    brino likes this.
  11. Charles Spencer

    Charles Spencer Active User H-M Supporter-Premium

    Likes Received:
    966
    Trophy Points:
    93
    City:
    Worcester
    State:
    Massachusetts

    -Return to Top-

    "I'm thinking I'll put both in and leave it like that unless the hit to rigidity is too serious. I'm sure I can borrow a torque wrench from the maintenance shop"

    ...and Elizabethtown, Kentucky. Are you at Fort Knox?
     
  12. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    That would work pretty well actually. I've got a big plate of 5/8" 6061 and some short SHCS I could use as a base. Thanks! Now my only real worry is getting under the skin of the casting without carbide tooling. As for the torque, I don't plan on being super anal about it, I just want to really crank them down without stripping the threads out of the base.


    Nope, I do R&D at a plastics company in E-town itself.
     
  13. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

    Likes Received:
    1,356
    Trophy Points:
    113
    City:
    Riverton
    State:
    New Jersey

    -Return to Top-

    There is no reason that the CI will have a hard surface unless done intentionally.
     
  14. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    Really? Just about everything else I've read has said that raw gray iron castings have a hard "skin" where the molten metal quickly solidifies as it touches the cold mold and that getting underneath that can be a bear.
     
  15. Cobra

    Cobra United Kingdom Active User H-M Supporter-Premium

    Likes Received:
    350
    Trophy Points:
    63
    Location:
    Moncton
    City:
    Moncton
    State:
    New Brunswick

    -Return to Top-

    Haven't had a problem with HSS. Just don't try to take a 5 thou first cut.
     
  16. Fabrickator

    Fabrickator United States Active User Active Member

    Likes Received:
    342
    Trophy Points:
    63
    City:
    Lakewood
    State:
    California

    -Return to Top-

    I got almost another 2" I think it is out of just changing the gas strut to one off an old Riviera. I also made a new stop to go with it. I have not been looking for any more height since making this mod. It's more than enough room to change out tooling, if you keep the projects proportional to the size of the equipment that your using. I also made a stiffener for the column at the same time because mine is not the solid mounted type. In my pics, I show how I did it along with the part numbers and plans, along with a whole host of other mods I've made to my mini mill.

    http://www.hobby-machinist.com/threads/my-lms-mini-mill.22202/
     
    royesses likes this.
  17. spongerich

    spongerich United States Active Member Active Member

    Likes Received:
    26
    Trophy Points:
    18
    City:
    Orange County
    State:
    New York

    -Return to Top-

    I'm looking at adding a spacer to my Clausing and came across some threads suggesting MIC-6 Aluminum plate.
    It's made for jigs and comes already pretty flat. Seems to come in thicknesses up to 4". Offcuts are cheap on eBay.
    FWIW, I'd also think about making your part L shaped so it comes down over the rear of the base. You could add a couple of bolts there to resist some of the flexing force.
     
  18. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

    Likes Received:
    1,356
    Trophy Points:
    113
    City:
    Riverton
    State:
    New Jersey

    -Return to Top-

    The molds are sand which is an excellent thermal insulator, some molds have "chills" incorporated into them in order to achieve different characteristics in specific locations on the same casting. A cast iron stock product, round bar and tube, rectangular bars etc. intended for later over all machining would not benefit from such a practice, if one day you come across a casting that that has an intentionally chilled area you will know.
    I turned a piece of 2 1/2" round CI stock from McMaster yesterday, the surface was no harder then the rest, on a complex casting you may encounter sand inclusions which are an entirely different animal.
     
    Last edited: Oct 1, 2015
  19. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    I got the CI bar yesterday and took it to the makerspace. Unfortunately the vice they have on the bridgeport is absolute GARBAGE. I tried to use the brazed carbide bit I had that bought for my current fly cutter but halfway through the cut the casting started moving around and the bit got trashed. So I went to plan B and made a new fly cutter that would fit on the threaded arbor for my boring head using some 2.5" 7075 round bar and a 7/8-20 tap. The new head can take a bigger tool bit that has carbide inserts so I have more than one try if I mess up.

    I finished the fly cutter head this morning at work and tried fly cutting the CI smooth on my mini-mill and it worked great. I had to walk the fine line between getting under the skin and not bogging down the spindle with the small motor buy I only stalled out once. Hopefully once it's all squared up the rest of the project (drilling holes and mounting the column) will go fairly smoothly.
     
  20. 3dshooter80

    3dshooter80 United States Master of Metal Malpractice Active Member

    Likes Received:
    453
    Trophy Points:
    63
    City:
    Raleigh
    State:
    North Carolina

    -Return to Top-

    Please take & post pix during this mod. Very interested in seeing the results.


    Sent from my iPad using Tapatalk
     
  21. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    Alright, wall of text time:
    First things first, in facing off the cast iron with my homebrew fly cutter I noticed i kept getting these weird flakes as I was cutting. I just kept taking 0.007" passes until I found a plane that was clean so NBD really. Still weird though.

    M2X7qZ4.jpg

    Once I got done, I took the column+head off and saw what a packing grease and cast-iron-chip-filled mess it was so I decided to do a full teardown of the machine and give it the good cleaning and TLC it never got when I first bought it. I washed the dovetailed ways, gibs, leadscrews and everything else out with acetone, took off the saddle and the nuts that ride on the screws and cleaned out the threads. Then I painted everything in fresh lithium grease and reassembled.

    7JrgclC.jpg

    I also took the opportunity to install the DRO kit I've had laying around forever. I put the column back on to test the fitment of the blocks I made. Turns out the M8 bolts I ordered were too short so I rethreaded the holes in the base as 5/16" and got some 6" bolts from THD.

    PUPta2g.jpg

    The additional height made a HUGE difference. To make the most of it, I took the old z-axis rack from before I installed the air spring conversion and added it below the new one.
    qH96nca.jpg

    I also bumped the current one up one screw hole so that extends above the top of the column casting. the head will come more than half off the dovetail before the rack flexes back enough for the pinion gear to start slipping. I backed off 3/4" from that point and installed a stop so that I couldn't go above that and strip the gear over time.


    UekdKAp.jpg

    I had a problem though: I realized with the 11" air spring I would not be able to get the head far enough down use small endmills on short workpieces. So I bought an M10 tap and made an extension for the rod that supports the head from some 3/4" delrin I had laying around. (I actually had to reassemble the mill most of the way so I could use it to get everything lined up and drill a straight hole through the rod. Oops :p)

    7lgTcoe.jpg

    I had another problem though, with the extension in place I couldn't raise the head up high enough before the spring hit max extension to make use of my extra tall column. This is where the real inspiration struck. I replaced the lug that connects the bottom of the air spring to the back of the column casting with a tube that has a conical plug in the bottom.

    eL4us8X.png

    This way, when the air spring extends to its max length, it simply lifts off the bottom of the cone instead of binding. When you lower it back down, the cone shape centers the tip of the spring rod back to the same place in the center of the tube to avoid any side load that would ruin the seals on it. There is no support once it lifts off so you need to be careful to use the gib lock or fine feed clutch to hold it in place above that point. I also don't have a lot of confidence in the rigidity of the machine when the Z is maxed out like this but it's great for trying to get long drill bits into the drill chuck when you're near the limits of the work envelope.

    The result of all this is pretty impressive. I now have a gigantic Z space to work in which should make my life a lot easier when working on the sides of my molds.This is the max height
    MZ3NQBq.jpg

    And the minimum. This is dictated by the height where the top connector of the air spring touches the top of the rack

    NxDZson.jpg

    Once I got everything back together I tested the tram and the X axis is pretty much dead on but the the column was tilted a little forward in the Y axis. WIth a dial indicator in the spindle, the front edge of the table was reading about 2.5 thou higher than the back so I put a single 0.001" shim under both of the front column bolts and tightened everything back down. now there's about about 8 tenths between the front and back of the table (~4") and about 15 tenths left to right (~16") which I'm pretty satisfied with.
    WlpEW0S.jpg

    My original fear about the riser killing what little rigidity this small machine has appears to be unfounded. I can still take a 0.030" cut with a 5/8" roughing endmill without any chatter so I'm pretty satisfied.

    v5WFKXF.jpg

    I've already put the thing into use making this totally stupid and pointless wooden pistol grip stock for my mossberg 500.

    Neujbbe.jpg

    Also, here's a picture of the vertical stand I made for my portable band saw that I've been too lazy to make a thread about.

    8F5nU9H.jpg

    Happy hacking!
     

    Attached Files:

    Last edited: Oct 16, 2015
    royesses, noah and hman like this.
  22. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    Not sure why some of the pictures are huge. Anyone know how to fix that?
     
  23. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    BTT because I'd really love to get some feedback on my work so I know what I can do better
     
    turnitupper likes this.
  24. turnitupper

    turnitupper Australia Active Member Active Member

    Likes Received:
    134
    Trophy Points:
    43
    City:
    perth

    -Return to Top-

    Nice work TIGL, must do something similar to my mill someday:rolleyes:. Is that orange thing on the left in the second last picture the detachable power feed as I have a similar model?.
    John.
     
  25. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    That's the one! it makes tramming and vice squaring much less of a pain
     
  26. noah

    noah United States Swarf Registered Member

    Likes Received:
    0
    Trophy Points:
    1
    City:
    Brunswick
    State:
    Maine

    -Return to Top-

    Nice mod, I've been thinking of doing the same. What did you use for / where did you get the blocks? have you done anything else to stiffen the column?
    sorry if I missed the answers in the OP.
     
  27. banny tadd

    banny tadd Japan Swarf Registered Member

    Likes Received:
    0
    Trophy Points:
    1
    City:
    nagoya
    State:
    Outside US / Canada

    -Return to Top-

    Hi, Nice work , I have LMS3900 cnced mill.
    Id like to mod onto colum base.
    Can I get dimension of the riser?
     
  28. TIGL

    TIGL United States Active User Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Elizabethtown
    State:
    Kentucky

    -Return to Top-

    The hole spacing is 135mmx50mm. I'd post the diagram I got from chris at LMS but he specifically asked me not to distribute it since apparently they're working on a factory riser.
     
  29. higgite

    higgite General Manger - Proofreading Dept. Active Member

    Likes Received:
    583
    Trophy Points:
    93
    City:
    Houston
    State:
    Texas

    -Return to Top-

    They now carry a 2" riser.

    Tom
     
  30. MetalMuncher

    MetalMuncher United States Active Member Active Member

    Likes Received:
    7
    Trophy Points:
    8
    City:
    Sandusky
    State:
    Ohio

    -Return to Top-

    Well, I read this thread so I could tell you LMS has a 2" riser. Lol. Old news I guess. I've got the solid column conversion kit on its way, along with the 2" riser. Wondering if anyone has doubled up and used 2 risers? I'm also glad to read you feel added stiffening isn't needed. I've got a stiffener on my tilting X2, and it made a huge difference. It's already got the 3900 oversized table, with powerfeed on both X and Y (the latter I designed myself) so it will be a lot like a 3900 once this kit is installed. You did a nice job! And I was wondering about the issues with the air spring lift, so I liked reading how you dealt with that. Well done! :)
     

Share This Page