Clausing 8520 CNC Retrofit?


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    Default Clausing 8520 CNC Retrofit?

    After lurking here for months now, I finally have a question to ask. This is a terrific place to visit, and I've gained much great info from my time spent here.

    I've owned a small Clausing 8520 for over 30 years, and have used it extensively in my gunsmithing & manufacturing business. It's a great little machine, still in good conditon, and I'm considering retrofitting it to CNC for use in my tool manufacturing business.

    Ideally I would still be able to use it manually also, as well as in CNC mode for repetitive small part manufacture.

    Does anyone have any experience CNC-ing one of these small mills? Any ideas and suggestons will be most appreciated! Thanks in advance! Joe

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    i dont know the extent of you knowledge but very generically speaking, people here are handwheel-phobic.
    They use 5/8 5tpi ballscrew for x and y axes on benchtop mill conversions.
    3/4 5tpi for z axis
    Double angular contact bearings on one side, unsupported on the other.

    buy ballscrews here in order of affordability and, industrialhobbies.com homeshopcnc.com mcmaster.com

    Motion drives here. geckodrive.com xylotex.com, for the size of your mill the xylotex 500 oz/in is plenty enough torque, dont quote me on that, see my other post on torque.

    when someone cnc's a knee mill they usually go for the quill because the knee weighs half a ton, you dont have this problem.



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    Gunsmither-
    I have almost the same mill - Mine is made by Johannesson, before Johannesson was bought by Clausing. The main difference is the quill on mine has only 2" of travel, where yours has 3".

    I have thought about CNC'ing mine, but I already have a 3 axis CNC bridgeport. I even started to model up doing the conversion, see the attached jpg. I'm not "handwheel-phobic", as I took the time to ADD handwheels to my bridgeport which never had them before. If you add encoders to the ends of the ballscrews or the motor shafts, you can disable the drives and still use Mach3 as a DRO if you have the proper encoder reading software add-in. I would have to remember where I found the software, but it is somewhere on this fourm.

    I have been thinking of converting the X & Y axes to ballscrews, as I have many new .200" lead preloaded hiwin ballscrews. I would also like to install a DRO, as I like using the mill manually. The original screws and nuts are showing plenty of wear, (about .015-.020") as the machine dates to 1954. The ways are still in decent shape, and I really like using this small mill.

    I had another idea about the Knee (Z) axis. If you keep the original Z screw, just add a lock to the screw to prevent the handle from rotating when under CNC control. Then convert the nut on the base to rotate with a needle bearing to take the thrust load. Put a pulley around the nut and belt drive it with a motor. If you use a motor with a power off brake (I have a bunch of these as well). When the CNC is off, the brake will engage, and all you will need to do for the Z is unlock the Z handle and use normally. With this idea for the Z the encoder will not work when in the manual mode, as the motor and encoder are not rotating. Another idea for the Z motor is attach it to the base of the leadscrew that projects down into the steel base cabinet. The motor could travel vertically with the screw if you add a vertical rail to prevent the motor from rotating, then the DRO would function as the other axes do. Alternately, you could add a spline to the end of the Z screw and then the Z motor could be stationary while still rotating the Z screw. This arrangement could have trouble with backlash in the spline though. If you have the steel cabinet under the mill as I do, there should be enough room in there to mount the Z motor, power supply and the drives. Perhaps even a small sized computer.

    I have heard a few people talk about this conversion on the Yahoo site for Clausing mills and lathes:
    http://groups.yahoo.com/group/clausing_lathe_and_mill/
    But the only messages I could find about CNCing a mill are a few years old.

    Let me know if you are planning on going forward with the conversion, and we can talk about the ballscrews, motors and brakes.

    PM me if you are interested.

    NEATman

    Attached Thumbnails Attached Thumbnails Clausing 8520 CNC Retrofit?-long-axis-jpg  


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    Default Thanks for the replies!

    flakker, I'm very CNC challenged, so I don't know why folks would be "handwheel phobic" ? Can you elaborate on this phobia?

    I would have to be able to use the mill for manual machining also, as it's my only mill. I was visualizing some sort of clutch to dis-engage the handles when used in CNC mode; just a thought.

    I don't have a DRO, but rely on the handwheel divisions for most work, as the screws are still accurate enough for the majority of gunsmithing work.

    If I had more room in my shop, I'd just go with a Bridgeport, or clone CNC. Might have to enlarge the shop again to make room for a dedicated CNC mill, and just keep the Clausing as is.

    Thats intersesting about the Johannesson company NEATman. I bought my mill in 1976 from a gentleman who said he bought it new in 1950. If yours was made in 1954, my guy must have been mistaken about when he bought it.

    I've checked out the Yahoo Clausing site, but have'nt found much on converting an 8520.



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    "flakker, I'm very CNC challenged, so I don't know why folks would be "handwheel phobic" ? Can you elaborate on this phobia?"

    All I really meant by that was people dont do it much and some of the ones that do take them off after the first cnc session finding them useless. doesnt mean you will.



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    Gunsmither-
    I can't be sure of the 1954 date, I can't even remember where I had seen that date. I've owned the machine for about 10 years now, and it's been great. I've always been vigilant about keeping it well lubrucated, but time has taken it's toll on the screws. I will replace the screws with the new ballscrews at some point, and perhaps I'll just CNC it at the same time too.

    Slip clutches wouldn't be needed, as on my full size bridgeport I have 42 frame 1600 oz-in stepper motors. When the drives are turned off, it dosen't take much to backdrive the motors. You would just have to disable the drives.

    I agree, I still haven't seen anyone who has converted one of these great mills, but perhaps the 6x26 millillingmachine yahoo group will yeild more results. Look here: http://www.iandalziel.co.uk/cncmill.htm
    I found this at:
    http://groups.yahoo.com/group/6x26mi...t=windows-1252

    Very simmilar in design, and this article will give you some idea of what it takes to convert a similar sized knee mill.

    Neatman



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    Default Thanks for the links!

    Thanks for the links NEATman! I'll check them out.

    The head bearings get very warm on my mill if I run it a long time at high speed. I pulled them out and greased them years ago; probably should do it again someday. The motor pulley bearings are about ready to be replaced again I think.

    The table/knee lube ports leave a lot to be desired. I built an oil pump gun to force oil into the tiny spring loaded oil ports. A one shot pump system would be kind of cool, especially if converted to CNC.

    I have a motorized knee lift on mine that I made from a drill motor and 1/4" chain/sproclet drive. I also have a table feed made from a vari-speed drill and chain/sprocket. The table drive speeds up production on some items I manufacture, and the knee lift is a joy to use.

    A VFD will be in the future for this mill, wether or not I ever convert it to CNC, as I'm tired of swapping belts!

    Best regards! Joe



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    Joe-
    One thing about the VFD's, they are great as I have one on my bridgeport, they do make the motor variable speed, but the torque is proportional to the motor speed. The motor only has full power at it original rated speed. For example, if you run it at half speed through the VFD, it will have half the torque.

    I have often thought about adding a one shot system also, but I haven't taken the time to take care of it yet.

    Neatman



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    Default Re: Clausing 8520 CNC Retrofit?

    Eleven years later and still no reply.

    "Does anyone have any experience CNC-ing one of these small mills? "

    I need to do a ballscrew conversion to my Clausing 8520 and will add a motor making at least the first step toward CNC.

    I sure would appreciate any help and suggestions.

    I doubt I can buy ball screws that are exact replacements so how would I machine the ballscrews?

    Thanks for the help.

    Ralph



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    Default Re: Clausing 8520 CNC Retrofit?

    Ralphxyz,
    Wow - I haven't checked my old-old e-mail in about 6 months, and this e-mail was at the top of the list. I've continued with CNC stuff & 3D printing, but the 45hr/week day job and the side business (www.airrocketworks.com), my excellent tool-enabling wife & two great kids takes up all of my time.

    I never did get around to CNC'ing my little Johannesson, as my Bridgeport is still running well (I've added a 4th axis too). Also, the Johannesson is just the right size for my kids to learn manual milling with, so I've left it alone. Funny thing is my 10 year old son wasn't even born yet the last time I replied to this thread. Now he's running this mill from time to time, and loves spending time in the shop inventing stuff. :-)

    The easiest way to convert a machine like this would be to use steppers. You can get a great 4 axis system from Gecko Drive for $300, then you'll have to add motors, cables & limit switches. G540 4-Axis Motor Control | GeckoDrive You'll need a PC with a parallel port to connect direct to the G540, and Mach3/4 or LinuxCNC software.

    Regarding modifying the ball-screws, as they are usually case hardened, you will need to grind through the outer layer, then machine the bearing journals to size on a lathe. I have used a tool post grinder in the past, but be sure to cover the lathe ways to keep the grit from getting in them. In a pinch, you can hose-clamp a dremel to the lathe tool post, but it's really slow. Also, your dials will now be incorrect, as they are 0.100" per rev. Most ball screws start at about 0.200" per rev. If you remove the manual handles & dials, it really doesn't matter, as you need to calibrate the motion on each axis anyway.

    Keith (NEATman)

    NEATman
    Basic research is what I'm doing when I don't know what I'm doing. Wernher von Braun


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    Default Re: Clausing 8520 CNC Retrofit?

    First of all how about some pictures!
    The ballscrews can be made to any length, bearing journal and thread size you want. Having bearings on 1 end or both is up to you also.

    Ditch the handwheels as they are not needed and the screws dont provide enough resistance for manual machining.

    A lazy man does it twice.


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    Default Re: Clausing 8520 CNC Retrofit?

    Quote Originally Posted by Fastest1 View Post
    First of all how about some pictures!
    The ballscrews can be made to any length, bearing journal and thread size you want. Having bearings on 1 end or both is up to you also.

    Ditch the handwheels as they are not needed and the screws dont provide enough resistance for manual machining.
    Wow is right, thanks for the replies.

    I am brand new to machining, I have a Clausing 8520, that has seen years of machine shop usage as the primary mill, a mini lathe
    and a Craftsman 12x36 lathe that is still outside in a crate for the past six months.

    My mill has excessive backlash (0.0500) on both X and Y not sure about Z.

    So I am thinking about doing a ballscrew conversion and really looking for some help.

    I would probable do the angle grinder on a lathe for machining the screws.

    I can get ballscrews relatively cheap off ebay, but I have no idea what the quality but anything would be an improvement.
    It might be wise to start with the cheap ball screws off ebay just to go through the exercise of doing the replacement then I could get more expensive ball screws if needed and have the knowledge of how to fit them.

    Would I be able to turn the screw on the lathe with carbide tools after I removed the top layer with a grinder?
    If so then the Dremel might work.

    Here are some ball screws from ebay, they are nicely detailed and a great price.

    Of course I am trying to insist that I get my workshop (which I have been building for three years now) finished to the point where I can install
    the 12x36 lathe before I do the ball screw project.

    This past winter I installed a variable speed motor and full DRO instead of finishing the shop as I was supposed to.

    Thanks again for the replies, I am looking forward to the help!!

    Ralph



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    Default Re: Clausing 8520 CNC Retrofit?

    I would probable do the angle grinder on a lathe for machining the screws.
    Yikes!

    Neatman's tool post grinder would be a lot better than an angle grinder.



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    Default Re: Clausing 8520 CNC Retrofit?

    Thanks,Do you have a link to Neatman's tool post grinder?

    The tool link is meaningless.

    I searched all of Neatman's post but could not find a tool post grinder.

    Ralph



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    Default Re: Clausing 8520 CNC Retrofit?

    My experience with ball screws is with LinearMotion2008 on Ebay. I have dealt with Chai as have many others here. I am sure there are other reputable sellers too.
    He will build the screw to the dimensions you provide, threads and all. The prices are very reasonable in my opinion as are the delivery times. I do however replace his square threaded nuts.
    Initially on my G0704 I was in the .003 or so backlash for a while. I have experienced backlash up to the .007 range, with single nutted ball screws. I could get that down a few thous with double nuts and maybe I will. In the meantime Mach3 and its backlash compensation work very well, again in my opinion.
    Are you confident in your thread cutting abilities on a manual lathe? If so, grinding off the hardened area should be a snap. To me, manual threading is a whole new can of worms. I can do it but not consistently.

    A lazy man does it twice.


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    Default Re: Clausing 8520 CNC Retrofit?

    Quote Originally Posted by Ralphxyz View Post
    Thanks,Do you have a link to Neatman's tool post grinder?

    The tool link is meaningless.

    I searched all of Neatman's post but could not find a tool post grinder.

    Ralph
    I think he was referring to tool post grinders in general, not to a specific grinder.

    Start here and do some research:

    https://www.google.com/search?q=tool...=1920&bih=1021



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    Default Re: Clausing 8520 CNC Retrofit?

    Yes, I was talking about a tool post grinder. I have this model:
    https://www.dumoretools.com/tool-pos...8vloaf6vorngg1

    I got it from a friend for $100. It was used once, and is about 15 years old. Pristine condition with a nice steel box case. I was floored when I saw the selling price of near $2k!

    When I had to grind something in the past, (before the tool post grinder) and the best method I found was to use the lathe headstock to drill a hole in a block mounted to the tool post. Into that hole you can load an old style dremel flexible shaft handle (aluminum body) like this:
    http://www.jeff7.com/projects/scanne...0flexshaft.jpg

    I use this trick all the time on my little Emco Unimat 3 lathe. I'll try to post a pic of that tomorrow. It gets plenty of use at work, especially with prototype parts for the LUKE prosthetic arm that I have helped design. Mobius Bionics Home Page

    You can also get a more substantial flexible shaft tool like this one, and do the same trick:
    https://www.dremel.com/productimages...lUx9i1lSpG.jpg

    By using the lathe headstock to drill the hole, you are always on centerline, and parallel to the ways. If you want to get fancy, you can use a boring head in the headstock to make the hole just the right size to fit the OD.

    Just remember to cover the ways with tinfoil to prevent the grit from getting into the ways!! It stays put and won't catch on fire. The grinding grit will wear out your ways very quickly otherwise.

    To prevent backlash with ballscrews, you want to get preloaded nuts. There are a couple different styles, but they prevent the axial play found in "catalog" ball screws. The nuts are usually matched to the shafts and are not interchangeable. I had sold dozens of ballscrews just like this years ago - leftovers from my last job. I could check to see what I have left.

    NEATman
    Basic research is what I'm doing when I don't know what I'm doing. Wernher von Braun


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    Default Re: Clausing 8520 CNC Retrofit?

    Thanks Neatman, Wow the Movius Bionics project is fabulous, I would love to be involved in such a project, once I learn what I am doing.

    I have a dremel and the flex shaft, I wonder how well one would work grinding the ball screw.

    I am amazed at the prices I have seen for different grinders, I really do not understand the WHY, the components seem pretty straight laced, nothing really special about them that I can see.

    I purchased two ballscrews off ebay, they were relatively cheap so I figured that would be a good way to start, if I mess things up I will not be out a lt of money.

    I got a 1000mm and a 250mm ball screw. I can chop almost a foot off the 1000mm screw to use to learn how to grind it to size.

    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!
    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!

    Your second link to 404 Not Found just goes to a intro image not what you intended.

    The dumore grinder is awesome but expensive you got a great deal.

    I also got some ballscrew nuts to make up my own preload nut assembly, we will see how they work with unmatched screws.

    Now I have to set them aside I cannot be working on this project, I have other projects that need to be done first!!

    Ralph



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    Default Re: Clausing 8520 CNC Retrofit?

    I too have a 1954 Clausing Mill, with a really low serial number. I would first check to make sure that your leadscrew nuts and shims are in good order before I tore into it to convert.

    If you are REALLY hellbent on converting, you should try to sell it first and buy something like a G0704 instead. You''d be surprised at what small used machines in the right market would go for.

    As far as toolpost grinding- avoid it at all costs on small manula lathes. That dust will mess your lathe up bad really quick. You are best advised to get the scews made to order.

    just my 2 cents

    Dennis P.
    Northern, Illinois



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