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advice need grinding Rockwell C 60 part

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
I'm sort of a glutton for knowledge and I know that EG knows his stuff about gear cutting. I soak up everything, so I don't mind a little related OT but I also feel like the OP should be allowed to steer his thread where he would like it to go. At any rate, I hope that the thrust washers at least make some improvement, let us know how it goes.
 
Joined
Apr 14, 2018
Location
Airstrip One, Oceania
Still, I think a thrust washer/spacer is likened to a bearing. Nobody/few would want a bearing to have 99 .250" balls and one .251" ball. Based on this I think a thrust washer/spacer should be near dead flat.
That isn't how these work tho. Depending on how old the machine is, on one side of the hob spindle there is a cone-shaped bronze bushing and a steel cone that runs in it. On older ones, same deal on the outside end, on newer ones just a straight sleeve. Some of the very very last ones have roller bearings.

So the thrust washer really doesn't do much. It sets the fit between the bronze cup and steel cone, but that's not very critical and even if it was way less than flat, as long as it kept those two parts at about the right distance, things'd be fine. Heck, a wavy one might get lube in there better.

If he's lucky, tightening up that fit will help with the chatter but ... let's hope so, but the drive train on those things changes directions about fourteen times, everywhere you look are bevel gears spur gears bushings and a worm gear; so many places for things to get loose and sloppy. It's real unlikely that getting a mirror finish and perfect flatness on this thrust washer is going to solve the problem.
 

bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
Alright, to explain what EG is describing, my hob spindle washer was about 0.002 (that is a lot) too thin. So when I adjusted the spindle to no play with the lockrings I was setting to the taper, so to speak, and the thrust washer was not contacting. Then in use, the hob spindle could move left-right that 0.002 (which is really a lot of play on the hob) but the real significance of this situation is the two thousandth motion into the taper was the same as pushing a morse taper into its socket another two thousandths, which on a Morse locks the taper. The taper is similar to a Morse or B&S. So in use my hob spindle, in addition to allowing the hob an unacceptable amount of left-right play, was attempting to taper lock every time it pushed toward the taper.

The work spindle was doing the same thing to the tune of 0.003. The oil film strength was sufficient for delrin and brass gears, but for the steel gears the tapers were moving and psuedo locking.

EG may be right that my 80 year old machine may still make sucky steel gears, but getting rid of the taper locking and eliminating the left-right play has got to be a good start at improvement.
 

bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
The washers ready to go to heat treat. I made an extra large one as a practice piece. Ground with the same 46H wheel I used on my chuck. I will be getting the recommended Norton 5SG-46H for grinding the hardened washers.


IMG_1473.jpg
 

TheBigLebowski

Aluminum
Joined
Sep 9, 2018
The washers ready to go to heat treat. I made an extra large one as a practice piece. Ground with the same 46H wheel I used on my chuck. I will be getting the recommended Norton 5SG-46H for grinding the hardened washers.


View attachment 344128

bll230, I tried to respond to your pm but your inbox is full, Response below.

Sorry for the delayed response, I hope you were able to grind those parts without too much trouble.

Plunge grinding is done with no crossfeed motion, only table and downfeed are used. Each time you pass the wheel over the part, you feed down slightly so wheel continues to grind away at the part. You do this until you've reached the depth you want. This will leave you with a slot the same width as the wheel that is near finished depth.
Next you would raise the wheel up to clear the part, feed over slightly less then the width of the wheel and repeat to cut away another slot, continue repeating that process until the entire surface is lowered.

It works great for roughing small parts where the wheel isn't in contact with the part for very long, though it would be ill advised to use on longer parts.

As for manual grinding (in my opinion) is capable of taking deeper cuts, its simply because you have more control and feedback on what the grinder is doing. You can almost instantly feel when a cut isn't quite right on a manual grinder and correct course.

On the flip side, it's not necessary to grind aggressively using an auto grinder with coolant, as you can simply walk away with it and let it do its thing.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
likely I already mentioned this, the chuck area far from your bump rail and close to the operator is often the most accurate part of a chuck and off to the right or left can be even closer. The fresh dress may be a little rougher finish than a wheel with a little grinding on it.

Gauging the part and even taking the last half thow can be done on a piece of abrasive paper.
Automotive wet paper is likely the best..and you can make it .000025 flat and size along with a mirror finish.

Still, you have to consider heat swell with using abrasive paper.

*Oh, and debugging between grinds can save the part from scrap.
 

bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
Here are the parts back from heat treat. News in my life is I am moving, so this project is going to be paused for while. Some here may have given me thoughts on how to move the machines on my moving thread. I'll get back to this thread this summer.

Thanks to all. John

IMG_1489.jpg
 

rogertoolmaker

Cast Iron
Joined
Jan 3, 2016
60H and 100K is the smallest grit I would try. Using 150 and 220 grit may cause trouble with burning. Dress the wheel using a sharp diamond. The traverse speed used to dress the wheel can affect the finish.

Roger
 








 
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