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Thread: CNC router build to machine wood and aluminium (1mX1mX0.4m)

  1. #61
    Member peteeng's Avatar
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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Hi Rupesh - try here
    Screws Nuts Washer Sizes Peter

    Attached Thumbnails Attached Thumbnails CNC router build to machine wood and aluminium (1mX1mX0.4m)-iso_thread-gif  


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Thanks Peter.

    That helped. If I keep 15mm Dia for a M15 nut it falls under H tolerance class which has no-tolerance fit and this is why its so tight. I need to make the shaft around 14.8/9 to get a easy but still no-play fit (4g6g class).

    This led me to beautiful website.

    Metric screw thread: M Profile calculator

    Thanks a Ton!!

    -Rupesh


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Quote Originally Posted by Tony_Stark View Post
    The height really gets the attention, isn't it. :P

    I think that is why Peter suggested to make web for the columns to prevent that twist action. I think for my application the total Z travel can be cut a bit and the horizontal spread can increased. But I am still figuring it out.

    I have no access to my laptop untill next mid week. meanwhile, I practiced threading for ball screw end on a aluminum round. The end nut at the coupling block side is M15 for 2005. The nut is M15X1. So I set my lathe to cut a pitch of 1mm. can any one tell if there is any formula to calculate the shaft diameter for cutting a M15 thread. Does it has to be 15mm exactly or less and then thread is made over it. Cause the nut is fitting over it but its very tight. I have used 60 deg thread cutter tool.
    You don't normally need the diameter to be more than ( .1mm ) under or a diameter 14.9mm this will depend on the quality of the nut, if the bearing size is 15mm then this will let the bearing slide over the thread as well

    Mactec54


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    Talking Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Quote Originally Posted by mactec54 View Post
    You don't normally need the diameter to be more than ( .1mm ) under or a diameter 14.9mm this will depend on the quality of the nut, if the bearing size is 15mm then this will let the bearing slide over the thread as well
    Thank you Mactec.

    I will look for a external thread die as my lathe leadscrew has some play which is ruining the threads cut on it. M15 is an odd no, hope I get it here. Meanwhile I would like to share my experience of machining the ball screw. I searched the forum and found some technique. I hope this will help others too.

    Ballscrew, It tough, really tough. Initially I started machining using carbide tool. Two carbide tool became dull in going through just the threads and then it became work hardened. Then I had to heat the ends by a portable propane torch to realign the grain structures and relieve the stresses (Annealing). I heated it for like 5 minutes till it started glowing dull red and then let it cool for another 15 minutes. After that it was cutting like a butter. I could cut through it using HSS tool. It just the tool will get dull frequently. So a carbide is better here.

    To ensure the heat doesn't dissipate to other threads, I used some wet rag wrapped around the ball screw where heating was not required. First attempt was not that good, some heat went through and discolored 2-3 threads. But on the other end (floating end) I could keep it well within limits. Its easier to machine once annealed. On the floating end I just heated it and let it air cooled and then machined.

    As I have a mini lathe and I can't admit much within the centers, I made a arrangement to stop whipping of the ballscrew. You can see the arrangement . Just machined a aluminum round and press fitted it at the other end of the lathe spindle. That limits the whip but doesn't eliminate it completely. I avoided tail end support here as I could not get the ball screw it centered in three jaws. I used a coca cola tin can in-between jaws to avoid any dent on the ballscrew. Then checked the centricity using a dial gauge. I positioned it in the ball groves and turned the chuck by hand simultaneously moving the carriage to keep the dial at in the groove. Works ok. Could see 1mm deviation but I should be ok with that.

    Once I was close to the bearing fit, I used emery paper to make the final fit. This is a time consuming exercise but worth doing and one should not to rush. One sec its too tight and other sec its wobbling.

    @peter. I got the angle grinder from STANLEY 900W. I think this would be enough to cut the aluminum using cutting blade. Need to think of some guide to keep the cutting straight. Also, I got the next batch of rail guides. I will get my laptop in 2 days. Then I plan to finish designing in another two and hopefully will start by the coming weekends.

    Attached Thumbnails Attached Thumbnails CNC router build to machine wood and aluminium (1mX1mX0.4m)-img_20200921_010706_1-jpg   CNC router build to machine wood and aluminium (1mX1mX0.4m)-img_20200921_010720_1-jpg  
    -Rupesh


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Quote Originally Posted by Tony_Stark View Post
    Thank you Mactec.

    I will look for a external thread die as my lathe leadscrew has some play which is ruining the threads cut on it. M15 is an odd no, hope I get it here. Meanwhile I would like to share my experience of machining the ball screw. I searched the forum and found some technique. I hope this will help others too.

    Ballscrew, It tough, really tough. Initially I started machining using carbide tool. Two carbide tool became dull in going through just the threads and then it became work hardened. Then I had to heat the ends by a portable propane torch to realign the grain structures and relieve the stresses (Annealing). I heated it for like 5 minutes till it started glowing dull red and then let it cool for another 15 minutes. After that it was cutting like a butter. I could cut through it using HSS tool. It just the tool will get dull frequently. So a carbide is better here.

    To ensure the heat doesn't dissipate to other threads, I used some wet rag wrapped around the ball screw where heating was not required. First attempt was not that good, some heat went through and discolored 2-3 threads. But on the other end (floating end) I could keep it well within limits. Its easier to machine once annealed. On the floating end I just heated it and let it air cooled and then machined.

    As I have a mini lathe and I can't admit much within the centers, I made a arrangement to stop whipping of the ballscrew. You can see the arrangement . Just machined a aluminum round and press fitted it at the other end of the lathe spindle. That limits the whip but doesn't eliminate it completely. I avoided tail end support here as I could not get the ball screw it centered in three jaws. I used a coca cola tin can in-between jaws to avoid any dent on the ballscrew. Then checked the centricity using a dial gauge. I positioned it in the ball groves and turned the chuck by hand simultaneously moving the carriage to keep the dial at in the groove. Works ok. Could see 1mm deviation but I should be ok with that.

    Once I was close to the bearing fit, I used emery paper to make the final fit. This is a time consuming exercise but worth doing and one should not to rush. One sec its too tight and other sec its wobbling.

    @peter. I got the angle grinder from STANLEY 900W. I think this would be enough to cut the aluminum using cutting blade. Need to think of some guide to keep the cutting straight. Also, I got the next batch of rail guides. I will get my laptop in 2 days. Then I plan to finish designing in another two and hopefully will start by the coming weekends.
    The Ballscrews are case hardened so can be a challenge to machine but doable with the right inserts heating is one way as long as the heat does not travel to far up the screw, you should thread it with the lathe as much as you can as using a die will not cut a square and parallel thread which is needed for the nut to lock up square against the Bearing

    I hope you mean 0.1mm 1mm would not be good

    Mactec54


  6. #66
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    Quote Originally Posted by mactec54 View Post
    The Ballscrews are case hardened so can be a challenge to machine but doable with the right inserts heating is one way as long as the heat does not travel to far up the screw, you should thread it with the lathe as much as you can as using a die will not cut a square and parallel thread which is needed for the nut to lock up square against the Bearing

    I hope you mean 0.1mm 1mm would not be good
    Oh,Is it. Then I need to practice more on threading to perfect it. Also I will try some mean to bring down to 0.1mm. I have not machined the floating end completly so will tune and try bringing it around 0.1mm.

    -Rupesh


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    one thing that helps keep the screw centered in the chuck is to cut a sleeve to slide over the screw with a split down the length of the sleeve so when you tighten the chuck it acts like a collet. just put the split on the sleeve in between the chuck jaws. self centering chucks could work but a 4 jaw chuck and a indicator would probably be better since it can get adjusted. the bore of the sleeve should be as close as you can get to the O.D. of the screw so your turns are concentric with the screw. Another thing the sleeve does, is to give you something better to indicate in. just set an indicator to zero when it barley touches the sleeve so it does not bounce to much when it passes over the split in the sleeve.

    it's good that the ball screw was hard to begin with. now you know it's made well.



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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Quote Originally Posted by Tony_Stark View Post
    Oh,Is it. Then I need to practice more on threading to perfect it. Also I will try some mean to bring down to 0.1mm. I have not machined the floating end completly so will tune and try bringing it around 0.1mm.
    Even 0 .1 is a big number Ballscrews are normally machined very precise .003mm or better

    Mactec54


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    I tried yesterday and after ten minutes of adjustment I brought it down to almost none. The dial gauge I have has a least count of 0.1mm. I couldnot see it move between the division. It just move very fine. so I think it must be perfectly centered. But I need to find a way to make it easy to do. the trial and error adjustment consumes hell lot of time.

    The CAD work will speed up now. I got the laptop which has solidworks. I also found out that getting the profile is very costly due to low volume and also its not available locally. I need to replace those with some other structure may be by hollow MS square?.. I probed the local market here. while I can get all the aluminum sizes, Getting profile is seems far fetched. Need to modify the design.

    -Rupesh


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    Quote Originally Posted by machinedude View Post
    one thing that helps keep the screw centered in the chuck is to cut a sleeve to slide over the screw with a split down the length of the sleeve so when you tighten the chuck it acts like a collet. just put the split on the sleeve in between the chuck jaws. self centering chucks could work but a 4 jaw chuck and a indicator would probably be better since it can get adjusted. the bore of the sleeve should be as close as you can get to the O.D. of the screw so your turns are concentric with the screw. Another thing the sleeve does, is to give you something better to indicate in. just set an indicator to zero when it barley touches the sleeve so it does not bounce to much when it passes over the split in the sleeve.

    it's good that the ball screw was hard to begin with. now you know it's made well.
    The sleeve idea is great. I will machine one and see if that makes things easier for me.

    -Rupesh


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    it's about impossible to indicate a screw because of the pitch of the screw is not suited for locating the concentricity of the shaft, the split sleeve gives you 4 points 90 degrees apart from one another to indicate in so you have next to no run out on your bear block diameters of the shaft. it works really well as long as the sleeve bore is almost a bearing fit. it should just barely fit over the screw with out having to force it before you cut the split in it. once you cut the split it will probably spring open some but that is ok since the chuck will compress it around the shaft when you do the machining. just take your time getting a nice fit over the screw before you split the sleeve so you don't get to much run out.



  12. #72
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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    Yes, that's sound perfect way to do it and make sense. I tried putting a flexible strip over the screw while holding its one end in the tool post i.e. The rectangular strip's one end was clamped in tool post and other end lying over the screw. This way it help see the deviation but still this is not that perfect way of doing- just a makeshift.

    One correction in my earlier comment:

    I just checked, the dial indicator has 0.01mm as least count and all long I was counting 0.01 as 0.1mm. WTH. So when I mentioned the deviation as 1mm in my previous post it was 0.1mm at that time.

    -Rupesh


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    Default Re: CNC router build to machine wood and aluminium (1mX1mX0.4m)

    .01mm of run out is pretty good and i think you would be fine up to .03mm of run out. the flex coupling will compensate for some minor run out. i would try to get it as close as you can regardless since the less you have the better off you are. the small hobby lathes should be able to do better than .1mm that's close to .004 imperial and that is getting out way more than what you want. the method i explained should get you into the .03mm or better range if you take your time with it. i have a 9" x 21" hobby lathe and i was able to make a spindle with .0002 imperial of run out on that machine so it's hard to do much better than that with the hobby machines.



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