Grinding Tip

To All:
    Here's a short video from Cutting Tool Engineering Magazine with a surface finish grinding tip for those shops doing grinding work.
http://www.ctemag.com/aa_pages/2009/0911_GrindingDoc_Ep3.html
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That's actually a pretty good video. Use a finer wheel, dress is rougher. Most people do the opposite.
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Good chart & info. Don't know about other moldmakers, but we were not to concerneed with RMS. Its heat generated whilst grinding, directly relating to flatness & size. Yes its the dress, Alice.<g> Don't use a "ball bearing" diamond, as many do. I like to finish dress wheels above 100g with a sharp diamond. You can hear the sound.... shooooooooo, & feel the grit hitting you in the face<g> Simply put you are opening up the pores of the wheel instead of pushing them over. My fav all around wheel= Norton 46H/I - Hey Norton! ya Ralfy boy!
So that being said & done, WTF is the wheel to use on Titanium alloy? mostly dry. We use the green silicone carbide 60g - soft wheel - breaks down quick, but still gernerates heat like crazy! & loads, but not as quick as Aluiminum oxide wheels. I've suggested, at least try a "cold gun", they aint that expensive! Oh well...... the horses don't want to drink. I've been looking to buy my own, damn local industrial supply places aint open Sat. any more. The "rigged" air hose trick helps in a pinch & also a mr. Misty or mrs. Misty, its personal preference, mine is miss misty- cool,& always wet.<g>
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cncmillgil wrote:

Gil:
    Yeah, for truing the grinding chuck, I'd dress the wheel about as fast an I could crank the handle, then come make a pass and move the table over almost the full wheel width, make another pass, move out another 1/2" and continue. Very little heat and you'd end up with very flat tables with a finish that had miniscule grooves in it that could trap dust and grinding grits when "wringing" your part down on the table.

    Temporarily drape a damp rag over the back parts "catcher" support, then most of the grits hit the rag and fall straight down rather than ricocheting all over the shop and under the grinder's ways. Don't leave the rag there when you start grinding or you'll may set it on fire.

    46H is sort of a universal wheel for Die Makers (which I was in a former life). If you need sharp corners you'd go back in with a 100J or if you REALLY needed a sharp corner a 120K wheel.

    Did you try pushing some candle wax in the wheel and applying a light brushing of oil on your part when grinding titanium? That I mentioned about 3 months ago. It also works for aluminum grinding as well.
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wrote in message

I'm a 60J man myself, norton all the way!

For corners I like an 80J with a negative 1-2 degrees on the face, so as you dress the botton, the edge stays sharp.

I found the 100I get's me there. The wheel is a bit soft, but allows it to dress easier. But most of the time I use the 80J, and dress from the corner I want sharp to the opposite corner. The diamond will lift the wheel, and as you come off it, thats when it breaks the edge.
Lots of people say you can't get any sharper corner than the grit size, as in you need a 120 to get a .0003 corner. Iv'e found that to not be true. I can get down to a tenths corner with an 80. Maybe the grit is breaking and creating sharp corners smaller than the grit size.

grinding titanium does require a cold gun, or coolent or something.
Oh well...... the horses don't

Yah but that stuff gets in your lungs. Maybe one of the newer models might not do that. Maybe a micro drop.

I would try grinding with the face as opposed the bottom. Try using something harder and finer, maybe an 80j. Dress the face smooth, and the bottom dress a little rougher. As grinding, try to keep the spark on the front tip of the wheel by feeding in as your traversing. And use coolant or a cold gun. If you have no coolant, get a cheap fish tank pump, and a bucket. Use rags for the filter on top of the bucket. I used to grind a lot of cpm10v, real nasty stuff, you couldnt side wheel it whatsoever. But for flat grinding the above process would work great.
What you can do is set your diamond next to your part. Dress your wheel. Take a dust grind on your part, zero out your readouts or dial. Now go over to your diamond using a stop and just touch it. record that number or put a mark on the dial. (thats the relationship of the wheel to the part) NOW...you can grind a pass, then go dress your wheel, when done dressing, reset the dial or readout to the number you recorded or the mark you made. You are exactly back where you were. Go grind another pass, dress, reset the dial, etc... It's real fast... homegrown wheel comp.
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Good stuff! Thx guys. Vinny your a manual CNC head.<g> I do the same with the diamond setup outside my work travel, come over & feed into it, longitudinal, continue dressing by down feeding, then back over to your work,move light to left,looking down the work from the right, can usually eyeball within a few tenths. Why do people put the light on the right? Opitidressers are the ticket for form grinding, if you have an xtra 10k? I have tried oil & crisco on Ti like Al grinding. not much difference. But.... the light show is fantastic! You'd swear it was the 4th of july! The burning little sparks of oiley Ti actually make a snapping sound. I turned the light off & had fun.- od grinding on the AB/harig spinner- The service tech guys were ready to call the fire dept<g>
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vinny wrote:

Vinny:
    Let me start off by saying that personal preferences can vary all over the map, and still work for each person.
    An old time rule of thumb is that you use hard wheels (J) to grind soft material and soft wheels (H) to grind hard materials. In Die making 90 percent of what you grid is hardened (RC 62-65) A2 & D2.

    Are you primarily grinding graphite? The sharp edge you create would tend to break down pretty fast in hardened materials, and you have to constantly adjust your Y in feed.     I always liked to dress a small (.050-.1) lip on the back surface. It will last for a number of dressings with adjusting the Y position.

    Good point, you always want to START at the corner you'll be using. Since the corner your diamond comes off the wheel on can tend to take chunks of wheel with it due to pressure. Kind of like flaking flint by pressure in making arrowheads. That parallels what you said, but from another perspective.

    Soft grinding wheels tend to wear down the grits until the point that they are flung out of the wheel when enough pressure is exerted. I would say you could easily get away with keeping your corners sharp grinding graphite, where they would be much more likely to break down when grinding hard materials. Hence my use of fine grit wheels on hardened materials.

    Misters are pretty common in most of the shops I've been in that have some surface grinders. The evaporation of the liquid from your parts really helps to draw the heat away. But you're right, some people have a hard time dealing with mist though. You can always use a vacuum apparatus on the grinder, and/of use a breathing mask.

    Full face side wheeling on hardened material is asking for trouble. Burning the material can create heat-checks and weaken the material, even if later light cuts remove the evidence of the earlier burn marks.

    Wet rags and a pan of cold water can do for some materials in a pinch, but SOME sort of cooling is important. And make sure before you do the finish pass that the part is at ambient temperature, even if you have to go away and do something else for awhile.

    That's a good tip. You have to have a very stable diamond (that won't move during dressing forces), and an accurate X stop.     I tended to just count the hand crank revolutions (up or down) to reach the diamond. That would get me close and a little 1/2" wide Magic Marker line would help me pick up where I left off. You don't want to mark the whole length of your part (unless it's warped), since you don't want to load your ultra-fine wheel with Marker ink.
    I'm actually surprised! A relatively On-Topic thread lasting more than two posts in here. LOL
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wrote in message

Not really what I meant. When grinding I would use a wheel with a flat dressed face, still grinding like normal, but while traversing, cross feed in to the point the spark is on the face of the wheel. Not sidewheeling, but technically it is. Even if just taking a 1/2 a thousandth, keep the spark on the front of the wheel. Cross feed too slow and it will wear the wheel. Same concept as hard milling, keep the spark out front and the heat is concentrated in front of the wheel, and that part grinds away.

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AH side grinder head! joke when you see your co workers trying to push back heels on inserts. When alot of stock has to be taken off a face, I hand relieve the face with carborandum or the diamond holder standing up on the magnet, till just the corner of the face has a small flare, like making a cup wheel out of it. It wears but can really remove stock without that burn/heat checking. Feed right into the work-(side grinder head)<g> not down for roughing. The finish will be an X pattern on your part if your square to the spindle, not just a C pattern(one side of the X) is what you get most of the time, spindles not quite sqr to the cross travel? Thats ok for shoulders & heels that dont require an nice surface finish. Ya kinda screw up the wheel & you cant dress too much off the bottom before loosing the flare. Oh well its a perishable cutting tool! Same kinda thing when bottom grinding like HSS. - releive the bottom so only a small area like 3/16-1/4 of a 1/2"wheel contacts

I just pushed a 40mm R back on hardened CPM10v last week 1/2'! I was amazed. Ya it got hot, but a couple of norbide swipes, by hand to de glaze the wheel & it was good to go! OD plunge grinding. It was not a critical R. I found a 1" 46h wheel in the cabinet all dressed from my predecessor(retired now, but was a moldmaker in previous life-go figure) Old moldmakers/diemakers don't go away they just .....???? <INSERT HERE> Get better.

Exactly, place the wheel close to the part & let it run. The wind from the wheel helps cool it down a little faster. Now work on G job.<g> Ok, sweep or clean something if the boss is around.

Also not much input from the usual crowd either? Hmmmmmmmmmm wonder why? Their taking notes? Copy, Cut & pasting to other more popular most read BLOG's? Ah FYI: guys thats cntl<c> cntl<x> cntl<v> on your keyboard "PEBCAK" still ROFLMAO

Ya how come were talk'in manual stuff then? because good manual machinists make great CNC machinists- end of story morey
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.0003 with a 80 grit wheel? I think you had a zero too many, Vinny.
A 90 degree corner is one thing, but when it comes to grinding really fine threads or detailed profiles, we use 150 or even 250 grit.
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wrote:

Iv'e gotten below .0005 with an 80j no problem. 2-3 tenths with a 100I.

Of course..(no pun intended). The problem with a v type form or a thread shape is there's no bond to support the corner, so it basically falls off on rougher wheels when dressing. When it comes to stuff like that it's basically a comprimise between what a wheel can support and it's ease of dress. As far as 250 grit goes, ok for an orange wheel grinding round stuff, but for flat I would never go higher than 100. But it's way more complex than that. For regular flat stuff I'll use a 32 hardness bond, but for round stuff I use a 38 bond hardness. A good wheel for grinding threads on round parts is a 38A120L. A good wheel for flat grinding and holding a dead sharp 90 degree corner is a 32A80J. If you have butloads of round parts on a centerless grinder where there's tons of pressure I'd use a green wheel(silicon carbide). Lots of variables, lots of wheels.
Last place I worked had a 400 grit wheel. I wonder what dumbass bought that wheel. Looked like cloth.

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Was interesting. Wished the chart was on-line. The idea is in the brain the numbers are in the books.
Martin
BottleBob wrote:

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