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Surface Grinder Ripples

WakelessFoil

Aluminum
Joined
Aug 18, 2020
I am new to surface grinding and have been experimenting with our Proth surface grinder on a test piece of steel.

I have the feed rate pretty slow and the cut depth is very shallow (although the steel stock is not perfectly flat with high and low spots of a few thou). When I go to make a pass, I keep getting these ripples in the surface finish and no matter how much I tweak things, they seem to persist. The depth adjustment seems very sensitive to me; a 5 degree turn of the handle is enough to plunge the wheel into the stock and cause the spindle to slow down. I am almost certain this is due to user error as the machine was set up by a professional. Any input on this is greatly appreciated.

-Justin
image0 (8).jpeg
 
Could be a number of things.
- Wheel balance.
- Poor or no dress.
-The wheel not wrench-tight and so tightens at starting or engaging the part.
- Hardness of the wheel or of the part.
- Having a bow/hollow on the opposite side of the part.
- Using the wrong grinding technic such as down-grinding* or incremental cross.
for starters.

*But no point in guessing until we know what you are doing.

QT: (a 5 degree turn of the handle is enough to plunge the wheel.)
Do you mean to say 5 thousandths?
QT: as the machine was set up by a professional. and he made a decent grind?
*Good to post wheel specifications and part thickness and hardness -> File soft, or too hard to file...and your grinding technic.
(*down grinding .005 and even .0005 may be way too much depending on the wheel or the part.)
 
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Could be a number of things.
- Wheel balance.
- Poor or no dress.
-The wheel not wrench-tight and so tightens at starting or engaging the part.
- Hardness of the wheel or of the part.
- Having a bow on the opposite side of the part.
- Using the wrong grinding technic such as down-grinding or incremental cross.
for starters


QT: (a 5 degree turn of the handle is enough to plunge the wheel.)
Do you mean to say 5 thousandths?
QT: as the machine was set up by a professional. and he \made a decent grind?
*Good to post wheel specifications and part thickness and hardness -> File soft, or too hard to file...
Thanks for the input. The wheel does likely need to be dressed.

I used degrees because I was only trying to stress the sensitivity of the elevation handle. I am not moving the head 5 thou.
The machine did make decent cuts before. Like I said I think the issue has something to do with my methods/inexperience.
I cannot see the wheel specifications as they are covered by hub, I will try to find more info on the type of wheel. It seems pretty fine and has a dark grey color.
 
it is not uncommon that dark gray is better for long wheel life, but not for free cutting and cool grinding...but we don't want to blame the wheel with not knowing how you are using it.
If you tap on a thin part (<3/8) and it does not feel rock solid that can be a problem, not uncommon a thin part may get surface burns and suck up off the chuck.
The wheel flange nut should be as tight as you can make with the supplied wrench with one hand on the wheel and one hand on the wrench. The spindle nut as tight as you can wrist-twist a 5" long wrench holding the middle of the wrench.
The ( not slow) dress should be with a fresh sharp facet of the diamond.

*but just guessing here until you send some data.
 
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Like Midland said, it looks like it is burning, are you using coolant? Most dress the wheel wrong or the diamond dresser is dull. When you dress with a sharp diamond move fast across the wheel. Take a couple of .002" passes and on the last pass stop. Don't keep dressing it back and forth until you don't hear a noise. When you do that the wheel gets burnished and dull. I like a universal grit wheel 46 grit and if I was to describe it - it's feels like 100 grit sandpaper. You have to use coolant on that thin sheet metal as it gets hot fast. If you have too use a squirt bottle and keep the surface wet.
 
Say uh, Rich... Is the picture not showing for you? Just asking since, umm, y'know, you asked if he was using coolant. And there's, umm, a flood of it visible in the picture... :D

Bob! 😄

As for the rest, where to begin?! You fellas got him on the right track. Look at wheel hardness, grit, and table speed first I think. Then we need to know DOC and cross feed amount.
 
As for the rest, where to begin?! You fellas got him on the right track. Look at wheel hardness, grit, and table speed first I think. Then we need to know DOC and cross feed amount.
Newbie or crusty old geezer; who doesn't miss those Norton wheel charts that broke down wheel selection by grades of material?
If any one has a line on those............ I guarantee you'll receive more up-votes than you know who.
 
Is that actually coolant as some suspect?
Or is the steel a slice that was embedded in something?
(I can't tell, but eyes are getting older)

Speed up the table, slow down the wheel rpm, and dress it with a sharp diamond.

Or, reveal the wheel spec including hardness & porosity, and we can guess a better option.

If as you mention it was cutting ok before, the wheel might not have been tight enough & you maybe ran it over a thick area that knocked the wheel off center? Need to either infeed grind, or start wheel high and travel all over the part until it just kisses (find the high spot). If you use downfeed method as opposed to infeed method to grind, .0002 (2 tenths) per pass is deep enough to start. .001" is likely too much based on what you show without more info.

smt

PS, nevermind on the coolant Q - i can see where it is over the part in the upper rh picture now.
Apologies for confusion.
 
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Be sure your wheel flange nut is two hands tight on a ring-tested wheel that has blotters.

Tap tap the part with a 1/2 " steel bolt (or the like) with your finger on the part and see that it feels as dead solid all across the part as the chuck.
Consider the likes of a 46 K white or pink wheel (HIJKL is also OK).
Turn your diamond that is set in a 10 to 25-degree angle holder to a fresh facet.
Make brisk dressing sweeps across your wheel to have clean-up with the last sweep of .001 or .002... (No fine dressing)
If the wheel is too wide, and the part is very hard the wheel may not be able to penetrate for down grinding and may bounce or slow the wheel RPM in that case you may need to dress the wheel to half its width. *just dress -.020 for a half inch (or what) off the bottom / not the whole wheel width
Goin going long travel across a very hard part in the climb direction can make a wheel bounce or slow the wheel RPM so for down grinding (and not as often cross grinding) when this seems the case, down feeding (and rarely at cross grinding) only on the grind-side can be good.

Incremental cross-feeding with a set/constant down amount can be another good technic. Just down feed .005 .020 .060 or what, and then cross feed into the part .020 (or what) crossfeed increments when the wheel is off the part as far as you wish to grind across the part, then dress the wheel and down-grind the last .005 (or what) to size and incremental cross feed back to off the part.
Long travel just at a comfortable speed..not too fast...slow is better than fast.
Going off the part at the long travel ends when down-grinding or incremental cross grinding can give the part cooling time.
Don't long travel and cross feed at the same time.
Don't make big cross increment. I think the going 1/4 (or what) wheel cross incremental might be OK(at best) for a .001 or .002 stock remove.. only.

Yes, just general stuff because I don't know what you are doing.
 
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Thank you all for the replies! I'll be sure to answer all when I get some free time this weekend.

I wanted to quickly post an update. We dressed the wheel, and sped up the side-to-side feedrate. In my head I figured slow meant finer surface finish, but I was wrong. There is still some visible ghosting in our finish but it looks a lot better than our initial test!

IMG_0175.JPG
 
Much better. It looks like you either have some wheel loading going on or perhaps swarf recycling through the coolant line. Best to do a final dress shortly before finishing. Like maybe a thousandth or so ideally, a few thousandths is okay too. A filter in the coolant return can help if the swarf is causing issues.
 
Looks like the surface the part is sitting on is flooded with coolant.

(Took me a minute too, to figure out what we’re looking at).
Hell I even cleaned my glasses and I can't see coolant. It looks like it's sitting on a blue cloth to me. I owned a Thomson and G&L grinder and ground a lot of parts with Cim Cool pink coolant. My 72 year old eyes are getting tired. If he is using coolant lets see him take a picture of it while he's grinding it.
 
Is that new on the right? Look like that's from before and you left it. It's late and past my bedtime. How much are you taking in each pass? Have you measured how deep the bad are is? My Brother Tom sells Abrasives and I'll plug his company. He can help you figure out what wheel to order and a new diamond dresser. Be sure it is in a good block and no burrs on the bottom. Most never change the diamond and they get dull. Oh on the last dress pass run the coolant. https://blueribbonabrasives.com/
 
Thank you all for the replies! I'll be sure to answer all when I get some free time this weekend.

I wanted to quickly post an update. We dressed the wheel, and sped up the side-to-side feedrate. In my head I figured slow meant finer surface finish, but I was wrong.

Too slow longitudinal speed can load the wheel and/or cause burning.

Material as above is another consideration. I’m by no means an old grinder hand, or old, or a grinder hand, but I do a ton of hardened D2 grinding. Everything for my die sets outside of Blanchard grinding (which gets sent out). Ever run a Blanchard? 2” coolant hose with the gpm of a pumper truck. Doesn’t work in a small shop.

There’s a PDF on the web called “How to Run a Surface Grinder”. Maybe by DoAll? I have a copy at the shop- it’s like HTRAL but for grinders. Good for basics to get you going.
 
13662918-CE7D-40F0-9584-E6C384F34329.jpegThis is from that book. It is a DoAll manual that covers several models. After the front matter are some great instruction on wheel mounting, dressing, trouble shooting etc.

You can make an entire career out of running a SG, so this is clearly not an exhaustive treatise, it’s a start.

If you cannot find the PDF online, PM me. I’ll email it to you. If yer the dude with the glasses and tie in your avatar you’ll have no trouble consuming the 50+ pages of tips and tricks in this booklet.
 








 
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