Boyar Schultz 612 Spindle Rebuild
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    Default Boyar Schultz 612 Spindle Rebuild

    I don't profess to be a spindle expert, but here's how I rebuilt mine based on multiple recommendations here and elsewhere.
    Remove the wheel hub and wheel guard.
    02-wheel-guard-removed-large-.jpg
    Loosen or remove the rear way cover so that the front dust shield can be removed.
    03-way-cover-removed-allow-front-shield-come-off-large-.jpg04-front-dust-shield-removed-large-.jpg
    Remove the two screws for the rear dust shield and slide that out of its groove.
    06-screws-remove-rear-dust-shield-large-.jpg

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    Remove the two bolts holding the motor to the motor mount and set the motor aside on a 5 gallon bucket or other support. The motor on newer machines is removed via the four access holes on the sides of the column after aligning the motor screws with the holes per information from the internet.
    07-rear-dust-shield-removed-large-.jpg 08-motor-removed-large-.jpg
    Remove the screw from each side of the top cover and lift it off.
    09-top-cover-removed-large-.jpg
    A taper pin holds the small bevel gear to the horizontal shaft. Tap it out from the small side. Loosen the socket screw on the rear of the shaft housing and pull the shaft out to remove the small bevel gear. Note that there is a spacer behind the bevel gear.
    10-taper-pin-removed-shaft-large-.jpg 12-allen-screw-backed-off-bevel-gear-spacer-removed-shaft-cropped-2-large-.jpg

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    Support the motor mount with a block of wood and remove the nut and washer from the large bevel gear.
    14-supporting-spindle-release-long-screw-large-.jpg 15-nut-thick-washer-removed-top-bevel-gear-large-.jpg

    Hold the spindle with your hand, but place a wood block under the area of the elevation screw, or on the chuck/table of the grinder to support the spindle after you gently tap the elevation shaft to release the bevel gear. Note that there is a thrust bearing under the large bevel gear and the gear is keyed to the shaft.
    18-thrust-bearing-under-bevel-gear-large-.jpg
    You can unbolt the motor mount from the rear of the spindle and then lift the spindle out of the housing.
    20-supporting-spindle-wood-befor-removing-motor-mount-rear-large-.jpg21-motor-mount-removed-large-.jpg

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    Unscrew the elevation screw from the spindle housing and you’re ready to work on the spindle.
    This is a good time to thoroughly clean the exterior of the spindle housing before proceeding further.
    29-spindle-pan-ready-exterior-clean-up-large-.jpg

    After cleaning the spindle, it may be worthwhile to see how much runout there is in the spindle prior to the rebuild. In my case this was 0.00025”
    34-.00025-runout-before-rebuild-large-.jpg

    The spindle pulley is held on with a single set screw which bears on a square key.
    24-set-screw-spindle-pulley-large-.jpg25-pulley-off-three-screws-holding-back-cover-large-.jpg

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    After removing the pulley, remove the rear outer dust cover, which is held by a single set screw which bears on a flat on the spindle.
    36-releasing-first-back-cover-large-.jpg 37-outer-rear-dust-cover-removed-slot-spindle-set-screw-large-.jpg

    After this remove the three socket screws holding the inner rear dust shield and wiggle it out to reveal the slotted nut which holds the spindle together.
    40b-inside-inner-rear-dust-shield-next-spindle-large-.jpg

    Here is a diagram with dimensions of the spindle nut tool I made. My spindle was belt driven so the dimensions may be different from models with direct Lovejoy coupling drives. At a minimum, my nut tool may have had to be longer since more of the spindle protruded to the rear to accommodate the pulley. I welded a piece of pipe to the rear of the nut tool in order to clear the spindle housing rather than welding on a nut and using a socket with an extension.
    46b-boyar-schultz-spindle-nut-tool-large-.jpg 51-nut-removal-tool-mill-large-.jpg

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    Here's the machined nut tool without the tail end welded on yet.
    52-not-removal-tool-after-milling-large-.jpg

    Now turn your attention to the front of the spindle. The slotted nut at the rear is on tightly and the front of the spindle will need to be clamped tightly in order to remove it. I bored a hole in a board and tightly clamped it in a wheel holder. The wheel holder needs to be tightly held on the spindle. If the wheel holder spins when removing the slotted nut, it may gall the spindle so the wheel holder must be screwed onto the spindle very tightly. An alternative and potentially safer way to hold the spindle is to make a clamp which bears on the flat used by the front outer dust shield. Note: the photo of the spindle clamp is borrowed from another member of Practical Machinist. It was presumably held in a vise or a large wrench
    53-clamp-front-spindle-large-.jpg boyar-schultz-spindle-clamp-tool.jpg

    Now return to the slotted nut. It is held from turning by a tabbed washer. Find the tab(s) which are in a slot and gently bend them out of the slot. Don’t over-bend the tab and weaken it since you may need to reuse the same tab.
    48-locking-tab-slot-nut-large-.jpg

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    After the tab is cleared, apply your spindle nut and front spindle wrench. The slotted nut is on very tightly so expect a little struggle. It is a standard right hand thread.
    54-nut-removal-tool-nut-large-.jpg 55-rear-nut-removed-w-text-large-.jpg

    Now loosen the set screw and remove the outer dust shield from the front of the spindle. It may be fairly tight to the spindle and may require penetrating oil and wiggling.
    56-outer-front-dust-cover-w-flat-spot-spindle-set-screw-large-.jpg

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    Then loosen the set screw on the housing for the inner dust shield. Others report that you may now be able to remove the spindle by pushing or lightly tapping the rear of the spindle. Mine required more than light taps so I used a press. The rear bearing can be removed from the housing with your fingers alone. There are two domed Belleville washers in the housing behind it. Their convex surfaces face each other.
    57-backing-out-set-screw-inner-front-dust-shield-large-.jpg 58-pressing-out-spindle-large-.jpg 59-spindle-assembly-w-rear-bearing-still-casting-large-.jpg

    At this point, look on the spindle near the bearings for any marks such as an X or a punch mark that may indicate the high spot of the spindle. Do the same for the inner bearing races to see if they have a marking for the high spot. My bearings and spindle did not have this but others rebuilding spindles have noted these marks. When reassembling the spindle align the spindle and bearing marks. I don’t know if the marks are to be on top of each other or 180º apart.

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    Remove the inner slotted nut. Similar to the rear nut, bend out the locking tab first. I used a spanner to remove the inner nut. It wasn’t on very tightly. Of course, clamp the spindle on a non-bearing part when doing this.
    67-removing-front-bearing-nut-spanner-large-.jpg 68-tab-lock-washer-keyway-large-.jpg

    Once the inner nut is removed, the front bearing can be pressed out. Bore a close fitting piece of pipe to the correct diameter to press on the inner race if you intend to use the bearing again.

    My machine is only used intermittently in a home shop environment, so I elected to try reusing my bearings. It was disassembled because it was becoming noisy. Others have reported successfully quieting noisy bearings by regreasing them. The alternative would be to do nothing and let the bearings deteriorate with each use.

    I cleaned my bearings in paint thinner / Stoddard solvent / mineral spirits using a tooth pick and tooth brush using multiple changes of solvent per bearing. Do not use acetone; it is reported to harm the phenolic cages. Much of the grease came out in chunks. There are warnings on the net that ultrasonic cleaners may damage precision bearings so don’t use one. Blowing compressed air through the bearings did not remove any grease or dirt for me. After the bearings were ostensibly clean with the mineral spirits however, a spray of carb cleaner removed additional particles as seen in the paper towel to the right of the can. Prior to the carb cleaner, I could feel a little grittiness in the one bearing. The carb cleaner removed any hesitation in the bearing.
    73-old-grease-picked-out-toothpick-cropped-large-.jpg 76-extra-grit-large-bearing-carb-cleaner-after-previous-thorough-cleaning-large-.jpg

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    Although the usual recommendation is to use one of the Kluber greases, after a discussion with one of the other members I used Chevron SRI-2 spindle grease because I was reusing my bearings and Chevron SRI is intended for spindle bearings. The dN number of the bearing is dN= diameter in mm X spindle speed). I used the average of the inner and outer races for my diameter and a spindle speed of 3600 RMP. The dN for these two bearings is roughly 122,400 and 129,600. Even using the diameter of the largest outer race 52mm instead of the average diameter, the dN works out to 187,000. The capability of SRI grease is up to 400,000 dN. Kluber NBU-15’s capability is 850,00 dN and Kluber NCA-15 is 1,300,00 dN by comparison. If I were using new bearings, I’d probably follow the recommendation to use Kluber.

    I greased my bearings using a syringe and needle. The rear bearing (Barden 204H) is reported to require 1.5cc of grease and the front bearing (Barden 205H) 2.0 cc of grease. To my eye, these amounts yielded a bearing fill of approximately 50%. Fill recommendations vary but seem to be around 25% to 30% or a match-head or BB sized blob between each ball. Nevertheless, my bearings did not get hot with 1.5 and 2.0 cc of grease when I ran them in.

    Grease the bearings and put them in a baggie until you’re ready to install them.
    80-greased-bearings-ziploc-bag-large-.jpg

    Turn your attention back to the spindle. Examine the bearing surfaces with magnification. The recommendation on the net is to lightly stone any scratches.
    79-inspecting-bearing-surfaces-scratches-removing-stone-large-.jpg

    After stoning the spindle, clean it, then oil it (I used Dexron transmission oil), wrap it in plastic kitchen wrap and put it in the freezer for a couple of hours to shrink it. The oil and kitchen wrap are to prevent condensation when you remove it from the freezer. When it was time, I warmed my front bearing on a 100 Watt trouble light until it was about 300º+ (10-15 minutes). When I placed it on the chilled spindle, it literally dropped in place. The side with the writing / small diameter side faces toward the interior of the spindle. Install the tabbed washer adjacent to the front bearing. Note that one tab is bent toward the front of the spindle and rides in the keyway. Tighten the slotted inner nut until it firmly holds the bearing on the spindle. Bend a tab into an open slot on the nut.
    81-heating-front-bearing-work-light-large-.jpg

    Using a heat gun (hair dryer if you don’t have one) warm the spindle housing until you almost can’t stand to put your hand on it. Again this heating is enough to allow the bearing to be pushed into the housing with hand pressure.
    83-heating-casting-heat-gun-prior-inserting-spindle-w-front-bearing-large-.jpg

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    Place the two Belleville washers with convex surfaces facing each other into the rear of the spindle housing. The rear bearing can be installed by hand with the writing / small diameter facing the interior of the spindle. Install the tabbed washer and the slotted nut. Put whatever you’re using for a spindle wrench back on the front of the spindle. Apparently bearing “preload” is as tight as you can get it in this system. I had placed an inquiry regarding how tight to tighten the rear nut and got no responses. Really tight was where the previously bent tab aligned with a slot in the nut, so that’s how much I tightened it. I backed it off to see if I could feel the Belleville washers relaxing a little, but I couldn’t feel that. It was either tight or immediately loose, so tight it was. Install the front and rear dust covers.
    Place the pulley on the spindle and tighten the set screw. Put the belt (Gates TruFlex 2210 21” x ½”) on BEFORE reinstalling the elevation screw. Or, if you do as I did and try to put the belt on later, you have to unscrew the elevation screw until the belt will clear.
    84-spindle-lowered-bottom-mount-belt-large-.jpg

    I spent some time cleaning the ways, elevation screw, and nut before I did the reassembly. Reassembly is pretty much the reverse of the disassembly. The fit of the spindle housing to the column and the motor mount to the rear of the spindle housing is incredible. I checked the spindle runout after reassembly. It was zero on my 10ths indicator. I must have randomly assembled the bearings and spindle with the high spots cancelling each other. Wish I were that lucky all the time.

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    After assembling the elevating mechanism and the motor to the spindle I did a run in using my Variable Frequency Drive. I ran it for 20 min at 15 Hz - about 900 RPM. It didn't get warm, so I upped it to 30 Hz for another 20 minutes. At most I could feel a little warmth in the spindle housing by this time. After that I ran it at 60 Hz for another 20 minutes. It didn't get hot, so I called it good and completed the reassembly. After this I did a small project and the bearings didn't get hot.

    As someone else who did bearings professionally noted, plan your work flow so that you have all of the tools you need ready so that there are no delays, especially once you open the packaging of new bearings. At that point you must complete assembly of the spindle to decrease the risk of any airborne dust contaminating the bearings.

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    Thanks for taking the time to provide a detailed step-by-step. I have a different kind of grinder (Jones and Shipman) so this is obviously more useful to someone with a Boyar Schultz, nevertheless I found it interesting and I am sure a number of people will find this helpful in fixing up old Boyar Schultz grinders.

    Cheers,
    Bruce

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    RLamparter,

    This represents a huge amount of work involved in making uncluttered, sharp, and well-lit step-by-step photos accompanied by clearly descriptive and thorough text plus custom tooling plans. You have provided an invaluable resource for the B/S owner who needs to tear down his spindle. Most likely other brands of spindles will, in many cases, be of similar construction so that someone launching into teardown and rebuild of a different brand will find benefit here, as well.

    Good work! And thank you.

    Denis

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    Great write-up! My 612 is direct drive, but other than that the spindle is identical to yours in every detail.

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    This is a great resource! It takes a lot of work & dual-focus (on the task, and on coherent recording) to keep stopping and taking photos. Even though my 618 grinder is a B & S, your clear procedure, documentation, and advice will be generally applicable if i do ever get around to the spindle bearings. I re-scraped the machine 15 years ago, but have been putting up with the noisy bearings since.

    Thanks much for posting this!
    smt

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    Quote Originally Posted by Conrad Hoffman View Post
    Great write-up! My 612 is direct drive, but other than that the spindle is identical to yours in every detail.
    Thanks for your off line advice on how you did your spindle rebuild.

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    Excellent write up!

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    Thank you for this procedure. Did you grease the bearing before or after heating on the bulb? If you greased before heating, did the heat melt the grease? Thanks!
    Jim

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    Quote Originally Posted by jbhigley View Post
    Thank you for this procedure. Did you grease the bearing before or after heating on the bulb? If you greased before heating, did the heat melt the grease? Thanks!
    Jim
    I greased before heating on the bulb, and the grease did not melt out of the bearing. The operating temperature of Chevron SRI grease is up to 350ºF. The dropping point of SRI is 470ºF. The net says that that's the point when it turns from a semi-solid to a liquid. My recollection is that, left on a 100W bulb long enough, a bearing will get to 400º+ degrees, but I only had to use this trick one other time, so I don't remember for sure how hot I got the part I was heating on the light bulb.


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