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advice need grinding Rockwell C 60 part

bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
I am making a hardened thrust washer for my Barber Colman. 3.75 OD, .335 thick. I found a heat treater in Los Angeles that will work with me and charge hobby pricing rather than industry pricing. O-1 material, Rockwell C60-62. The heat treat manager said to make the part 0.015 oversize, which coincidentally is the same as on the original BC 1921 blueprint.

The back of the washer can have grind marks on it, the front I want as mirror smooth as possible. Looking for advice on grinding wheels and technique to remove the 0.015. The tolerance of the final part is +-.0002. I have a Boyar Schulz 6x12.
 

AD Design

Stainless
Joined
Jun 27, 2012
Location
Tennessee USA
What wheels do you have? For something like this there's not a lot of material to remove so it's not terribly important how hard/soft the wheel is but the grit does make a difference. I'd use a 46 grit to get close, +.0007 of finish, flipping and verifying flatness/size. Then at least a 60-80 grit to .0001 of the high side of finish. After that I'd consider lapping it in with progressively finer grades of abrasive until you're satisfied. You'll need to be careful of lapping technique as it's easy to dome the surface so it's no longer flat. I presume you're familiar with allowing it to cool and using and indicator on a surface plate to verify flatness.

O-1 is an easy tool steel to grind but it's not very wear resistant if there's any friction on it, sounds like there is if it's a thrust washer application. If there is friction I'd likely have chosen D-2 for wear properties because I'm familiar with it. If you have the original drawings for the washer does it state the material used and the Rc? O-1 at 60-62 Rc isn't much of a draw back if any. If you do choose to use D-2 be aware that it doesn't stick to the mag-chuck very well and will require blocking in. It may seem to stick but it won't for very long against grinding pressure. D-2 will polish to a higher finish due to the higher chrome content. A-2 is also a better choice than O-1 for abrasion resistance but not as good as D-2. Selecting either A-2 or D-2 will require a good furnace control, wrapping in SS foil to avoid getting a soft "skin", and a higher price for HT. You won't get the added performance a better steel will provide if the HT'er doesn't do it correctly. Do you have a hardness tester?

You know more about your application than I do, just offering suggestions.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
What have you got available for wheels? Budget to purchase any? Got coolant? If budget is low, might just grind the washer then lap the side you want highly finished. Ideally, you'd grind with something around a 46 grit I hardness. Plus or minus a little on hardness won't kill you if you take it easy with only .015" to remove. Do whatever you can to get a sharp, free cutting dress so you don't build heat. Hand feed I'm assuming so probably run your cross feed a little lower, maybe .025" - .050" per reversal. You want to avoid any burning/discoloration at all costs.

Pfft. AO beat me to the punch. :D

Buck will be along shortly and fill in more that we forgot.
 

bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
Budget is enough to do job properly. I’ll get what I need. The original 1921 material was 1098, which I couldn’t find. The heat treat chemist recommended O1 after seeing the blueprint and seeing the application. In use it is on the work spindle with RPM on the order of 10s, very slow, and it is slathered in oil all the time, that is how these these Hobbers are going strong 60-80 years later. I am new at grinding so the non-magnetic material probably not best for me.

I have hydraulic feed on the table in my Boyar Schulz, but no coolant. I can spray coolant with an atomizer. I have a bunch of wheels, I’ll get another if I need to. I have 46, 60, 100, 150, and I think 220. I’ll get the mist coolant device if it is necessary.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Budget is enough to do job properly. I’ll get what I need. The original 1921 material was 1098, which I couldn’t find. The heat treat chemist recommended O1 after seeing the blueprint and seeing the application. In use it is on the work spindle with RPM on the order of 10s, very slow, and it is slathered in oil all the time, that is how these these Hobbers are going strong 60-80 years later. I am new at grinding so the non-magnetic material probably not best for me.

I have hydraulic feed on the table in my Boyar Schulz, but no coolant. I can spray coolant with an atomizer. I have a bunch of wheels, I’ll get another if I need to. I have 46, 60, 100, 150, and I think 220. I’ll get the mist coolant device if it is necessary.

Then I'd stick with the 46 for roughing in and just kiss/tickle a bit off at the end with the 100 you've already got. Lap it finer than that if you need it. Much easier and less risky than trying to grind super-fine without flood coolant IMO. I would do what you can to get some coolant on there, whether it's a spray unit or whatever.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
Does the mating face (thrust side) have slots to feed in oil? If not, may want to consider adding some ~3/32" cuts about a 1/32" deep to promote oil flow into the face.

A true "lapped flat" mate to the other part without passages may seal out the oil.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I agree with AD and Ekretz that a 46 would be a good get near size wheel and a 60-80-100 to make near the mirror.

Might be good to ask the hardening guy about stress relief.

Your chuck is likely best/flattest away from the bump rail so I would choose a set place perhaps 3" away from bump rail and Perhaps 5"" away from the left chuck edge, good to have some flat stock to set your part about there and in the same place at each grind. you could have a v notch flat bump stop set in the go direction.

The part needs to be/get dead flat as soon as possible so I would strike it with a good flat stone to see if there is a concave or convex side as it came from heat treat. I would place the concave side down on the chuck after stoning or flat paper lapping to have a little more flatness for the first chuck setting, then skim and flip a few times to be sure much of the surface stresses wire out.

Looking for .0002 and mirror you might take a practice run to a plus size perhaps .3400. Take it down to .3405 with the 46 wheel flipping to have taken the same from both sides(about). Check it for dead flat.
Perhaps wet paper lap it with figure – 8s and turning the part at about every 3 8s..you might even go down a few paper grits to paper lap it to a mirror finish.
Then confident that you can make .3400 +-25 millionths.. and knowing howcloseyou want to roughit in.

Yes, you may find the 46 grit finish is just too far away from mirror and proceed with the 80 or 100.
The 80 and 100 will be burn capable wheels so wet and special care needed...and a burn when a half thow away can scrap a part.
RE: automotive wet paper even down to 3000 (and finer) can be handy in a grind shop, to act like a lapping block.

If you are not very skilled a grinding you might consider making two part.

You might ask the hardening guy if he has any small hard scrap parts you can purchase, for you to practice on.
likely he will give you a few parts for free. Hard parts are a new ball game from mild, they like to burn, slide, warp, heat swell, shrink more.
 

Matt_Maguire

Stainless
Joined
Oct 17, 2011
Location
West-Central Illinois, USA
Budget is enough to do job properly. I’ll get what I need. The original 1921 material was 1098, which I couldn’t find. (snip)

That's a dead match for W1 water hard. .95/1C, .25Mn & .25Si, very clean steel & NO problems getting the hardness. Attached Crucible Black Diamond, they mad maybe 3-4 W1 water hards... Geez

Attached data

Good luck,
Matt
 

Attachments

  • Crucible.jpg
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bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
All the Barber Colman thrust washers, and there are a lot, have 3 radial oil grooves. BC made superb machines. As good or better than my 10EE.

The heat treat guy recommended the O1 over W1, maybe because of my grinding skill. I asked specifically about the W1.

I’ll come up with some coolant arrangement.

I have some spare pieces I made. I’ll send those as well to have practice parts.

Thanks for all the info. Hopefully I’ll have good results. Sending them off to heat treat tomorrow.
 

Paolo_MD

Stainless
Joined
Apr 6, 2013
Location
Damascus, MD
Definitely, I don't have much experience in grinding. However, given the application and the suggestion of using D2, which is less magnetic when fully hardened, it came to my mind this video from Don Bayley (Suburban Tools) "How To Surface Grind Super Flat Parts?"

He uses residual magnetism in the chuck. I would probably profit of the reduced magnetism of D2 and use some blocking.

Paolo
 

rrrgcy

Aluminum
Joined
Jun 5, 2013
Location
South Florida
O-1 is an easy tool steel to grind but it's not very wear resistant if there's any friction on it, sounds like there is if it's a thrust washer application. If there is friction I'd likely have chosen D-2 for wear properties because I'm familiar with it.

Tribolgy International June 2006 comparing O-1 to D2 at same high hardness Rc 60 - “ For relatively low sliding speeds AISI O1 steel performs up to 12 times better than AISI D2 steel in adhesive wear. For higher sliding speeds, however, this order is reversed due to oxidation taking place on the surface of the AISI D2 steel. The wear rate of both tool steels in three-body and two-body abrasion wear is proportional to the applied load.”

A lot to unpack, esp with definitions, and other readings indicate oxidation plays a role contrary to what I’d have thought - it increases wear resistance to sliding forces.

The heat treat chemist recommended O1 after seeing the blueprint and seeing the application. In use it is on the work spindle with RPM on the order of 10s, very slow, and it is slathered in oil all the time.

O-1 seems good. I heat treat O-1 all the time in the garage w a furnace and hit Rc 55-60 no warpage even on slender long parts all day. Don’t know about D2 I don’t work w it. But as for Tribology Intl. there’s probably a lot of good research out there on comparing various tool steel friction wear, just scratching the surface.

Q. Is the part coming de-carbed or will you need to do so? What is your plan for that, pickling and fine s-paper? I sometimes screw up on fine tolerances by finishing much too close and then post-heat using the grinder to cut through the carb and lose just enough thousandths of good stock because it’s done on both sides (grinding down that uneven carb crap) for the fine finish. Your .0075” extra stock buffer on each side should be more than good despite unevenness of the carb finish from post-heat treat to still allow you to grind both sides right away.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Hopefully your heat treat guy has a vacuum furnace. That would avoid most issues with oxidation.

Also, I'm curious, what's the mirror side of the thrust washer butting up against? Is it a bronze flat surface or balls or needles?
 

rrrgcy

Aluminum
Joined
Jun 5, 2013
Location
South Florida
You think you slipped that by us...
Ha! Almost ended up near you in Manchester, near 30 years ago interviewed w a law firm at the old post office which had been converted to office space… didn’t take the job, ended up in South Florida. I find materials science/engineering very interesting. One of my better classes in college for a consistent C-grade engineering student!!

I have no recommendation to wheels but suspect finest end finish possible is optimal.

Off topic, I just looked up Iron Trade Review magazine from 1912 (enjoyable read if you’ve worked in the steel industry) on a BC Hobber (spindle) says the front bearing is conical and runs in long bronze bushings and the thrust washer(s) have lock nuts to provide for adjustment in case of wear.
 

bll230

Hot Rolled
Joined
Jun 14, 2007
Location
Las Vegas
Rrrgcy, that is correct. Both work and hob spindle have long tapers that run in bronze. The work spindle thrust washer is pinned to the spindle, the mirror finish runs against bronze. The hob spindle washer the opposite, the washer seats against the bronze and the runs against the hardened spindle.

My machine is immaculate, sold to International Harvester in 1942, but in investigating why my tooth surface wasn’t as good as I thought it should be I found out that both spindle washers were too thin, allowing the spindles to essentially taper lock in their bearings. Why too thin? No idea, a previous owner thinking he knew how to grind to fit?

I don’t know anything about decarbing. What do I need to know?
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
I don’t know anything about decarbing. What do I need to know?

If the heat treatment is done in a vacuum furnace, I don't think there is anything to worry about.

Regarding the finish on the washer, I would have thought that a mirror smooth finish is not needed. Where it contacts the bronze shoulder, the washer will ride on an oil film that is a few microns thick. Provided that the washer finish is smooth at that level, there should not be any wear. (I may have read that to maintain the oil film some amount of microscopic roughness is in fact desirable, but I am unsure about that. I think the reason given was that some roughness is needed so that oil is dragged into the lubrication gap.)

Cheers,
Bruce
 
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michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
I haven't read all the posts here so these may have been mentioned.

Turn your diamond to a fresh facet sticking up.
Know your grinder's habit if there is a slight difference incrementing crossfeed in or out.(only go one way)
Debug in/during the process so you don't set on a bug with only one-tenth to go.
Know where you are by remembering the down feed number at dress and touch, so you know the hit place at a half thow away.
Know you wheels abilities, so not testing/experimenting on an important part.
Let a part set on a CI or steel plate for a time before measuring, so cooling back to size.
Might wear cotton gloves that have been through the washer a few times.
Alcohol and water makes a faster cooling solution than water(overkill perhaps)
Water spray with a little dish soap is a good coolant.
Water with some washing soda makes an anti-rusting coolant (But still need an oil wipe when done)
Good to plate check a close size compared with a calibrated JoBlock.
If micrometer sizing a part, still compare to a JoBlock.
Oh, never engage with conversation when doing close work.
It can be good to oil stone a chuck with a large new condition smooth stone 2"x6" in figure 8s.

The Boss: Hey Buck, what do you think about the Mets yesterday?
(thinking...)
what, who cares?
what did they do?
who were they playing?
Whoops! crash!...Darn.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Oh, never engage with conversation when doing close work.

Hey Buck, what do you think about the Mets yesterday?
what, who cares?
what did they do?
who were they playing
Whoops! crash!...darn.

Buck, all of your advice is good and very much appreciated, but this bit really rings true. I think I'll put up a sign with this.

Another one that hits the mark: you can't do fine precision work in a messy shop.
 
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