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Thread: More on lathe tools

  1. #1
    Supporting Member tonyfoale's Avatar
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    tonyfoale's Tools

    More on lathe tools

    I recently posted some adventures that I had cutting the back end off a lathe head stock. http://www.homemadetools.net/forum/i...515#post135903
    I was asked how I held the spindle for unscrewing chucks without any back gears. Well I never use back gears for that job, my mechanical sympathies cringe at the mere thought of it, it seems so brutal. That might come as a surprise from someone who cuts a lathe head in half without a second thought but I really hate abusing mechanical devices.

    My lathe came with a locking hole in the nose part of the spindle as shown next.

    More on lathe tools-lathegbh100.jpg Click images for fullsize version.

    I built a simple tool to securely locate in that hole using a G-clamp to save work. It rests against the foot of the lathe head and provides a very solid lock on the spindle and chucks unscrew easily. I hold it by hand when screwing a chuck on. There is no need to tighten chucks very tightly, that just makes it harder to unscrew.

    More on lathe tools-lathegbh103.jpg More on lathe tools-lathegbh098.jpg

    When doing the butchery on the head stock I needed to remove the rear taper roller bearing off the spindle. I also wanted to inspect the bearings and seals. There is a castle nut and an identical locking nut which provide preload to the bearings and hold the spindle assembly together, as shown below.

    More on lathe tools-lathegbh109.jpg

    I have seen people use a hammer and cold chisel to tighten and loosen this type of nut but in my book that is a method best reserved for emergencies and in the field when a proper tool nor the facilities are not available. This is doubly true when the nuts are on a spindle with bearings like a lathe. A hook spanner is much better but unless it is a very good fit it can slip off the nut. I had such a spanner which I modified for a better fit but although I was able to unscrew the nuts it was difficult to keep it in place.

    More on lathe tools-lathegbh101a.jpg More on lathe tools-lathegbh102.jpg

    As explained in my previous post I changed the motor and drive system from internal to external belt and pulleys. The top pulley on the spindle was from a car water pump drive and was heavily dished. The dish disallowed the use of a hook spanner or other type of flat spanner.

    More on lathe tools-lathegbh075.jpg More on lathe tools-lathegbh089.jpg More on lathe tools-lathegbh090.jpg

    I made a very solid wrench to handle the dish and fit all four of the cut outs in the nuts. The donor steel material all came out of the scrap box. There was a graduated ring from a handwheel off an old lathe, a very solid cup shaped piece from an old lantern style tool holder and a length of wrought iron work for the handle.

    More on lathe tools-lathegbh088.jpg More on lathe tools-lathegbh092.jpg

    I milled the ring to fit the nut and then turned a spigot on the piece from the tool holder to locate inside the ring.

    More on lathe tools-lathegbh091.jpg More on lathe tools-lathegbh094.jpg

    Then the pieces were all welded together to finish the tool.

    More on lathe tools-lathegbh104.jpg More on lathe tools-lathegbh105.jpg

    This wrench works extremely well, there is no tendency to slip off. The rigidity of it combined with the spindle locking tool permits a very fine adjustment of the bearing preload. Prior to the drive modification I used the hook spanner but the nut would always move in jerks due to its flexibility. Then adjusting the bearings was difficult problem.
    Good tools make light work of some jobs.

    More on lathe tools-lathegbh095.jpg

    Once the spindle nuts could be removed the spindle needs to be pushed out of the rear bearing to extract it. The spindle and bearings are fitted with interference and so considerable force is necessary to separate them. As before there is no substitute for doing properly with a suitable tool. A heavy mallet is the weapon of choice for many people but is certainly the wrong choice if you have any intentions of reusing the bearings. Heavy impacts will damage the bearings and greatly shorten the time before failure. A smooth force such as you get with an hydraulic or screw puller is much better. The puller than I used is very simple to make. It was made as a puller for separating crankcase halves of some motor cycle engines and had multiple holes to fit various tasks. To use with the lathe I only had to drill 4 more holes and find a couple of long 6 mm bolts and some 6 mm allthread.

    More on lathe tools-lathegbh084.jpg More on lathe tools-lathegbh085.jpg

    The bolts and all thread were screwed into the 4 holes that normally hold a seal plate, an aluminium plate protected the end of the spindle from the force of the puller screw.

    More on lathe tools-lathegbh086.jpg More on lathe tools-lathegbh025.jpg

    With the spindle extracted and devoid of the internal pulleys etc. I reassembled it to check for alignment. This is normally done by means of a hardened and ground test bar or by test machining and measuring. What better than to do it with the spindle? This requires that the spindle is not bent and is parallel over the measured range. Checks showed that both requirements were fullfilled. My last lathe tool in this post is both simple and crude but rigid enough and effective. I checked and corrected both vertical and horizontal alignment. The following pix show it better than words can.

    More on lathe tools-lathealigning-03.jpg More on lathe tools-lathealigning-04.jpg More on lathe tools-lathealigning-05.jpg
    45 Best Harbor Freight Tool Modifications


  2. The Following 3 Users Say Thank You to tonyfoale For This Useful Post:

    allenz (06-28-2019), Jon (06-28-2019), Seedtick (06-26-2019)

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    Thanks tonyfoale! We've added your Lathe Spindle Locking Tool to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:



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    Thanks tonyfoale! We've added your Lathe Pulley Removal Tool to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




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    Thanks tonyfoale! We've added your Lathe Spindle Removal Tool to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




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    Thanks tonyfoale! We've added your Spindle Straightness Checking Tool to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:




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    Supporting Member tonyfoale's Avatar
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    tonyfoale's Tools
    Quote Originally Posted by DIYer View Post
    Thanks tonyfoale! We've added your Spindle Straightness Checking Tool to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools.
    This is an alignment method not a straightness checker. Straightness needs to be checked prior to the use of this method.

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    Supporting Member tonyfoale's Avatar
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    tonyfoale's Tools
    Quote Originally Posted by DIYer View Post
    Thanks tonyfoale! We've added your Lathe Pulley Removal Tool to our Lathes category,
    as well as to your builder page: tonyfoale's Homemade Tools.
    Not a pulley remover but a spindle nut remover.

  9. #8
    Supporting Member DIYSwede's Avatar
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    DIYSwede's Tools
    Excellent job! -Now, I might be a lousy reader of your step-by-step walk-thru -
    but am I correct in assuming that the dished pulley fits between the castellated nuts?

    And when finally adjusting the pre-load, you're holding the inner nut (re: to the spindle) with the hook spanner,
    whilst tightening up the outer one with your clever crown spanner, pinching the pulley between the nuts?
    How much axial play is lost when you're tightening these nuts?
    Did you do this adjustment when housing is warmed up or when its cold?

    Perhaps I'm moving ahead a bit, and should relax, waiting a few posts for the answers?

    Keep up the good work!

  10. #9
    Supporting Member tonyfoale's Avatar
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    tonyfoale's Tools
    Quote Originally Posted by DIYSwede View Post
    Excellent job! -Now, I might be a lousy reader of your step-by-step walk-thru -
    but am I correct in assuming that the dished pulley fits between the castellated nuts?
    No, the pulley is not sandwiched between the nuts, they would not work as lock nut if it were. The pulley is welded to the gear which drives the change gears, that gear is keyed to the shaft.

    More on lathe tools-lathegbh012.jpg More on lathe tools-lathegbh015.jpg More on lathe tools-lathegbh075.jpg Click for full size image

    The first pic shows the gear and the pulley, the upper piece was some junk cast iron that I turned to make a welding alignment jig. The centre of the pulley was milled out for the welding leaving 3 tabs for alignment during welding. The second pic shows the gear and pulley assembled on the jig read for welding. The third pic shows the welded assembly after the welded area was faced off for the nut surface.

    Quote Originally Posted by DIYSwede View Post
    And when finally adjusting the pre-load, you're holding the inner nut (re: to the spindle) with the hook spanner,whilst tightening up the outer one with your clever crown spanner, pinching the pulley between the nuts?
    How much axial play is lost when you're tightening these nuts?
    The first answer makes this question redundant.

    Quote Originally Posted by DIYSwede View Post
    Did you do this adjustment when housing is warmed up or when its cold?
    That is a very good question. There are many recommended ways to do this. At least one major lathe manufacturer suggests putting a large bar in the chuck, putting an indicator on the chuck then lifting the end of the bar (lever) the indicator should show around 1 thou (0.025 mm). You gotta be kidding me.

    More commonly the suggestions are to run at high speed for more than ten minutes, then when you check the temperature around the bearing housings they should be warm but not so hot that you cannot hold your hand there for long. That is a pretty useless method also. I have found that loose or tight the bearing housings warm up about the same. Seal friction is considerably more than the bearing friction and that will not change with tightness. However, what I have found on my lathe is that it is the oil level which determines running temperature more than any other factor. I always suspected that the default oil level was too high, resulting in a lot of churning and power loss which turns into heat. I did some tests starting with what I regarded as enough oil and added oil in several steps up to the maker's level indicators. Each time the temp rise was greater.

    So what do I do. Firstly I chose to do it cold (there, that answers your question) because the spindle will generally heat up more and expand more than the housing. Therefore the preload on the bearings will loosen with temperature rise. If I did it hot then the bearings would be too tight when cold and that shortens their life. Taper roller bearings are not ideal for a lathe spindle application. The proper way to do it would be to have two back-to-back preloaded angular contact bearings at the business end to provide lengthwise location both fore and aft, and a (or more) standard deep groove bearing at the other with spring loaded inner or outer races (not both) such that the shaft can float axially. Why don't lathes have that? Some quality machines do but Taper rollers as commonly installed are far cheaper.

    I tighten the clamp nut carefully always rocking and push/pulling the spindle to feel the bearing clearance. This is easy up to the point where you are close to zero clearance, then you are only left with a feeling for the tightening torque, and that is hidden within the total torque which is swamped by the torque needed to move the bearing on its interference fit. Once I get to the point where I can detect no clearance, I go a little farther (do not ask for a quantity, it is purely based on an unquantifiable "feel"). Then I put a lump of fairly hard steel 50 to 75 mm diameter in the chuck and start turning. If it turns rough and the operation is noisy then I nip the bearing up a little more until it turns as I would like. A slow and tedious process but it is not something that I do daily. As I then use the machine on a regular daily basis I will tighten things a little more if results indicate that it is needed. Once set I check the temp rise at high speed. When fitting new bearings it is wise to run at say 1/3 to 1/2 of full speed for an hour or so before running at high speed.

  11. #10
    Supporting Member DIYSwede's Avatar
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    DIYSwede's Tools
    Thanks, Tony for your elaborate and quick reply, which fully answered my perhaps silly questions.
    Your general discussion on bearing types is right up my alley -
    angular contact ones is the 1st choice for my upcoming change,
    but also your choices for dismantling tools and why (incl pics)...

    The last paragraph's description of your method of bearing alignment is very helpful,
    reminds me exactly of how I way back had to make a device for adjusting wheel bearings on my TT bicycle:
    Adjusting the cones on the hollow axle for a good fit, only to have that overtight by the quick-release "skewer" bolt.
    Had to devise a way to compress the axle to nominal skewer pressure whilst adjusting the cone & locknut at the same time...
    No team bike tech I then knew had any idea what I was talking about - even less that it was a problem.
    Just put a screwdriver on the axle end, put your ear against the handle, turn the wheel and "listen to the bearing song"...

    And as always: -It all boiled down to "feel for play", and washing thru all the mutually exclusive methods supplied by manufacturers and "know-it-alls".
    There's exactly where your generous sharing of your own thoughts, methods and experiences are so useful!

    Cheers

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    tonyfoale (06-26-2019)

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