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Cylindrical grinding 4140 shaft questions

Rapid_Tech

Aluminum
Joined
Oct 27, 2014
Location
Toronto
Gentlemen,

I'm looking for advice on cylindrical grinding 4140 shafts. We make shafts ranging from about 1.5" diameter X 18" long up to 6" diameter and 90" long. Material is sometimes pre-hardened (~30Rc) but most often induction hardened (~55Rc).
Our two machines are TOS, one is 2 meter capacity and the other is 3 meter. Wheels are 24" (I think, but around there) X 3" wide. Tolerances are typically +/- .0005". Finish isn't too important, sizes are the most critical, mainly for bearings.

What wheel would you recommend, brand and type?
Coolant? Right now we use Cimcool Cimstar 40B
Any tips or tricks you might have for grinding

Thanks,
Peter
 
Very likely you are the man on this, or your shop is and it would be difficult to give much other than simple grinding techniques like turning your diamond and honing your centers, stuff you already know.
You might call Radiac Wheels and ask what wheels are most common for similar work.
Unless you have a specific problem that the PM guys could think about.

I use the Norton 5/8" point mounted center lap, but I see Msc has one for a low price. Don't know how good it is?... yes you throw it in a grinder and regrind the 60*


 
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Buck,

Yeah, I recently took over this shop and we do lots of cylindrical grinding of 4140. Personally, I don't have much grinding experience but would like to improve our grinding process as it is the biggest bottleneck in the shop. Eventually I'd like to try hard turning the shafts, either to finished size or at least to rough them down so grinding is sped up.

Cheers
 
Lathe turning is faster than grinding so the initial time improvement might be to make your turning operation as efficient as possible so as to get grinding take as low as possible. Stopping to measure eats up time so on the fly measuring might be good with using height set diamonds so off a hand-feel or DRO travel from a gauge point can safely give +.005 on the part for rough-in size. Live centers need be the best, and a good set up to regrind them to zero, (poor quality lives, even with regrinding are still poor lives because they have internal wobble that regrinding does not correct. Lives should run <.0001. One point lives run better than multi /changeable point lives. Royal single-point lives or the like are good (anything less is a time-waster..

Lapped part centers are good and a simple drill press can become a decent lapper.

Indicator dial micrometers set to a size comparison are a must and a good set of JoBocks. Size masters for repeat sizes.

Centers can be made with a circle-grind diameter so the center becomes a gauge reference, and a set height diamond can be the +.005 part size off the dress. Such can become the +.0005 of the dress.

Hard turning with ceramic or diamond tool bits is a very good idea.

IMHO a grinder boss can never know as much as an experience Grinder Hand so a grinding shop should have at least one top experienced grinder hand.
 
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