Chinese BS-0 Dividing Head

Mini Bike & Go-Kart Parts

was bored one night and ordered up a chinese clone of a Brown & Sharpe BS-0 dividing head for my mill.

it arrived ok, it weighs probably 30 pounds and it rattled around in the box on the way here, no damage but the box was pretty beat up.

as shipped the chuck had about 20 degrees of runout. the instructions were useless except for a table of dividing ratios in the appendix. youtube has a whole slew of dividing head "experts" showing how to pretty much damage your new dividing head.

long story short the chuck and mounting plate has to be removed to get to one of the runout adjustment locking screws. the chuck on mine was seized on the spindle. heat, pb blaster, kroil, and elbow grease were ineffective at getting chuck off the spindle so back it goes. the replacement it due here thursday. if the next one gives me trouble i'm buying a US unit.

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edit: and yes i used a heat gun on the chuck plate, not a torch, it succeeded in making the shop smell like eggrolls.....
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got the replacement dividing head saturday. the chuck popped off with no problem. stripped it down and cleaned all the metal chips, blackish gray gook, and had to remove one of the ball oilers whos' ball descended without provocation.

the spindle and associated parts are soaking in oil and tomorrow it gets put back together, all told a heaping teaspoon of grit and chips got flushed out. i might order up a new US made bearing if the chinese bearing doesnt survive the cleaning.

if the chinese ever got their s**t together they would be a decent source.
finally finished assembling the dividing head today. had to wait for the excitement of the minibike weekend and zanex to wear off.

if you decide to get one of these dividing heads be absolutely sure to strip it down to its components and clean it thoroughly.

when i first got it you could feel little bits of resistance when turning the crank. it also turned out the handle adjustment had the equivilent of 20 degrees of axial chuck run out.

the provided manual is worthless, it's a word salad at best. if you go the you tube route beware of the you tubers who used hammers and center punchs to remove gears and bearings. one guy ended up with damaged bearing when he beat it back in place with a hammer.

during reassembly i used ISO-68 hydraulic oil to lube everything. the factory grease that was in it had chips and grit so it all had to be removed.

i still need to test the chuck runout and have not gone through the tailstock yet. a piece of tight tolerance drill rod should help with chuck runout.

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there is a large black screw adjustment on far end of the hand crank worm gear. it positions the worm onto the 40 tooth spindle gear.

this large screw had a lock screw that is accessable from the lower front right side only after you remove the chuck and backing plate.
No no, this thing is rotated by a stepper motor and is under cnc control like the rest of the machine. 20,000 pulses will index 360 degrees. The locked rotor condition of the stepper motor through 100:1 rear reduction holds it in place.
No no, this thing is rotated by a stepper motor and is under cnc control like the rest of the machine. 20,000 pulses will index 360 degrees. The locked rotor condition of the stepper motor through 100:1 rear reduction holds it in place.
some day i will step up to cnc. i don't have the material and tool science down good enough for cnc.
i bolted down the dividing head to check run out at the chuck. first i swept the chuck o.d. as a starting point.

ended up with about half a thousandth on the chuck.

then i put a piece of ground carbide (+.0002" to .0000" tolerance" and ended up with two and half thousandths run out right at the chuck jaws. the peak runout is opposite of one jaw so there is probably junk or a chip on the jaw or scroll that i missed. it's getting cleaned again and retested.


yep. this chuck and backplate has no adjustment so a good cleaning will most likely fix some of the run out. like the dividing head the chuck has snags when turning the wrench.

i used ISO68 hydraulic oil with a rust inhibitor instead of grease inside and out of the dividing head. any thoughts on that??
got the chuck stripped down today. lots of dirty grease, grit, and a few chips.

i also found an off center ground pinion gear that engages the chuck key to the ring gear. take a look:



amazon hadnt picked up the first box so i picked the best pinion gear and swapped it out. runout is now + or - .0015" from 0 to 360 degrees on the chuck.

i might just order a timken bearing for the chuck end of the spindle and surface grind the rear bearing races.