New Shop Tool: Covel Surface Grinder

#21
Oops...same things apply to boring out a hole, reduce feed rate if tool still burns up or switch to tool steel with 2-3% cobalt, the cobalt really makes for a tough tool. The difference is obvious when you try to grind up a new tip.:)
 
#22
i do have some m42 cobalt hss blanks. i am just about through with the big end of the
wheel puller. i'll post some picks later on today or tomorrow. been busy with memorial
days guests!
 
#23
got the wheel puller done today and it popped off the wheel hub with a few twists of the bolt.

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i was thinking about making one of these wheel hubs but
my lathe clearly is under powered.

i need to buy or make a wheel balancer next.

:cool:
 
#24
these poor little guys broke during two separate "goofs". on the left is a 3/4" hss cobalt roughing mill. i was squaring up a piece of
1/4" plate steel, a neighbor stopped by to talk, i turned off the spindle but left the x power feed on. heard a loud band. trashed
the end mill and had to tram the head.

the center end mill is a 1/2" hss cobalt roughing mill that was damaged along with the 123 block. i got lazy and had the end mill in a
drill chuck. i was climb milling and the end mill pulled out of the chuck going deeper in the piece until it hit the 123 block and boogered
it up. this is why i do not buy expensive end mill and 123 blocks. i was machining aluminum.

this all happened while making switch box covers and a motor mount for the surface grinder.

:scooter:

phil


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#25
Well I'll just bet you don't make those mistakes again. Been there done that...and it always puts and ache in my back pocket!!! Happy to know there were no injuries from that shattered tool, sometimes those endmills send fragments clear across the room.
 
#26
i will try to remember to NOT trash 50 bucks of fine M42 tool bits and $12.95 worth of cheap chinese 123 blocks next time.

it is probably for the best i killed the 123 block. when i got it my mindset was " steel is steel, and square is square", i ended
getting a pair from suburban tool, the 11 hole version. i keep these hidden away for special occasions and use the amazon
"with 6 you get eggrow" 123 blocks for setups.

should i be checking for any damage to the spindle or bearings after the 3/4" tool crash? the head came out of tram
for that goof.
 
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#27
Yes Phil, use a dowel pin in the collet and check for runout. If it's crooked try a different collet or drill chuck, if they run crooked also you bent the spindle. If it is just bent a little you can probably coax it back to straight in a press, use your indicator as you push on it so you don't over do it.
 
#29
alright, i put some thought into this. measuring runout on the outside of the spindle
or through a collet and dowel pin will let me measure total runout, the sum of spindle
runout and the tooling runout.

i put a dial test indicator on the taper inside the spindle, hand turning 1 spindle revolution
or running at 90 rpm gets me a faint flicker on the dial test indicator. maybe a couple tenths.

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i don't think i damaged anything, it seems the taper would be the best place to measure runout.

the spindle is quiet, or at least i don't hear any new sounds.
 
#31
whew! dodged a bullet on the mill spindle!!!! back to the surface grinder.

everything is back together, got the 3 phase converter and control panels
wired and mounted. next 'goal' is to dress then balance the grinding wheel.

the little rectangular piece of steel with the slanted round is a diamond pointed
dressing tool i made. the mounted diamond point was purchased from mcmaster
carr and it's has a 1/2 carat point.

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norton has a pretty good tutorial on abrasives and they specifically address dressing and
balancing, it starts on page 31:

https://www.nortonabrasives.com/sga...Industrial_technical_data_health_safety_8.pdf

DSCN0565.JPG this is the spec for the grinding wheel i will be starting out with. 38A is the abrasive, aluminum oxide, 46 is the grit size, J is binder
hardness which is about halfway between soft and medium hardness, V is for Vitreous bond, and the BE are not defined in the
reference material i have.

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here is the magnetic chuck. it came off a Brown and SHarpe 510 surface grinder, i bought it used on ebay.

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here you can see the three phase disconnect on the side of the grinder. when i got the grinder someone had
relocated the start and stop buttons to a kludge box mounted just to the left of the X hand wheel. the
proper box location is just to upper left and behind the grinding wheel shroud. not the best place and
OSHA would probably condemn the machine just for that, but thats where it was. it had separate spindle
on and off buttons, and, it also had separate pump on and off buttons so this little baby once
had liquid cooling, i really wish it was still there. some of the old brackets and plumbing pieces were on the
pallet but the cooling system in its' entirety was mainly missing.

next i will be dressing and balancing the grinding wheel and hub assembly. i had to make a balancing
fixture and luckily i have a starrett 98-12 machinist level to level the set up. i had fits figuring out the best way
to balance the wheel and i will post some pics of the fixture i made. i also learned that the concrete slab
in my shop bends and the starrett level can detect the flex in the slab.
 
#32
a couple, or so, people asked me where am i going with this surface grinder. this is where it all
started; when i got my mill and figured how to NOT use it i slowly started out how to properly use
it and the tool bits associated with its' use. at first i produced crap on it. nothing was flat, or square,
and the fit and finish was on par with a cub scout den project. even if i made something i had nothing
to compare it to. nothing to verify angles, flatness, dimensions etc. a little while ago i produced this:

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it is the epitome of my accomplishments on the mill. my goal was to make it square. using
the metrology i now have it can be proven to be square within .002" over any of its' corners.

the rectangular hole is there because the piece of stock had a drill hole the was in the wrong
spot so i turned a piece of scrap into a useful experiment. before i do any surface grinding
on this piece i will heat treat it as it was purchased annealed.

i have a starrett 13 machinist square that was calibrated against a reference square at the factory.
the square is guaranteed to be square within .0015" over its' length. using a monochromatic 380 nM
blue light source i look for gaps between the machinist square and block of steel. if i cant see blue
light between the square and block the gap is less than .000015". so my basic measurement precision
is the accuracy of my machinist square or .0015" which isn't too bad. i can see some blue
light along the sides so the steel block is not perfect. but for making it on a mill it isn't bad. the error is
an unknown value between 15 micro inches and 1.5 thousands of an inch, most likely closer to
1.5 thousands.

depending on the runout of the surface grinder i should be able to achieve square and flatness
well beyond my current metrology accuracy, which is what i want to do with the steel block.

my metrology consists of a granite surface plate for flatness, a mitutoyo gage block for length, a
spherometer, two reference squares, several good and junk dial indicators, one mitutoyo dial test
indicator. i am also working on a cylindrical square and gage.

this stuff gets out of hand, i actually started ass backwards, i bought the mill first without being
able to measure anything. i had no idea what a surface plate was or why you need gage blocks.

i've done a few small jobs for local people, a cast iron bearing for a case tractor, cast iron piston
rings for an ancient mccullough chain saw, and 50 small mild steel weldlets for a guy repairing a
boat trailer (this was the only job that didn't cost me money!)

ciao~

:D

phil
 

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