Dialing IN a Surface grinder?

Hankins

Hankins

Well-Known Member
Dialing IN a Surface grinder?
Finally after ten+ yrs was able to get a surface grinder... to make stuff flat:eek:
Got her all wired up and the chuck ground. Started surfacing a Pre-HT Bowie blank that looked Flat!
Anyway after thinking things were just Hunky Dory I decided to Flip the piece over (Same Side up) and more material was coming off..Not expected!?
Now this is not a new machine by any stretch (Former high school shop) so maybe there is wear in other places...
Any Tips Tricks to figuring this out? Any help is appreciated
 
Job #1 would be to get a dial indicator (even a cheap one from HF would work) and clamp it to the wheel head and run the perimeter of your chuck or magnetic vise. The ways on the bed may not be truly perpendicular to the verticals ways. If you use a clamping vise, it could be going out of square when tightened.

Steve
 
It is a Magnetic Chuck...
That will be my next project this week, Thanks for the advice!
 
Are you using a magnetic chuck? If your work piece is thin and not flat, it will suck down to the chuck, you grind it "flat" then when you turn the magnet off, it twists back to its original twist. You can remedy this be not using the magnet on the first side. Double stickey tape or a vise works well.

If you ground the chuck on the machine, it should be parallel to the stone. You could check by attaching a indicator to the head and indicating the mag chuck it should read the same end to end.

If this doesn't make sense, I'd be happy to walk you through it on the phone. Good luck, Duncan
 
One other thing. I would expect to need to flip the knife blank at least once and maybe a couple times to get it truely flat. The is due to surface irregularities, internal stresses on the blank, and the dymnamics of how a mag chuck works.
 
Here's how I true things on my surface grinder...including any time the mag chuck gets changed or moved....

Keep in mind that my surface grinder is setup for belts, so it has a 100 durometer urethane contact wheel rather than a stone.

1. First: Using a 220 grit belt or finer, I grind the face of the mag chuck to match the surface of the chuck to the contact wheel.

2. I put a large file on the mag chuck, and lock it down, Then, WITH NO BELT IN PLACE, I gently run the bare urethane wheel over the file for how ever many passes it takes to clean the contact wheel up so that its true.

Once all that is completed, I've managed to keep my HF surface grinder's accuracy to about .0005.

I've found that much has to do with the quality of mag chuck that you have on a surface grinders. Within a week of purchasing my surface grinder, I trashed the cheesy mag chuck that came with it. Since I have gone through 3 different chucks. The one that's on the machine now is a fine pole, that cost nearly as much as the surface grinder.

A note about warped materials being "sucked" flat and then popping back. Steve Kelly turned me on to a trick of using feeler gauges....I purchase 3 of the feeler gauge sets that go from .0002 through .080"....pulled out the screw/nut combo that held the whole thing together, and if I need to surface grind something that is warped (you can always tell when you turn on the magnet) I will slip an individual feeler gauge under the "warped" area of the part, then clamp on the magnet.....sometime is takes a few different feeler gauges to get the job done, but it works very well (Thanks for the tip Steve!)
 
If you want to to see how it's grinding, get a pretty thick piece of stock so that you dont have to worry about the magnet flexing it.

Grind one side flat, corner to corner and spark out.

Flip it over and repeat. It may not grind uniformly on the 2nd side since it was probably not true and flat yet.

Now flip it back over and it should be pretty much dead on.

if it's not start by checking the gibs and ways are all tight. A lot of time when a machine gets moved it has to be tweaked back into square.

We want to see pics of your machine too! :)
 
I use feeler gauges also to grind out warped material. I'll lay the steel on my granit block, determine how much warpage there is with the feeler gauge then put that one under the piece I'm going to grind, in the proper place, to keep it from pulling down, then turn on the magnet. I grind that side flat then turn it over and take off the same amount on the other side. I always use a dial indicator and take off the same amount on each side.
 
Mothers Day so this will be Brief...
Picked up a HF Dial indicator (Across the street from the Grocery store ;)) but right now there are more pressing issues, like BBQing ribs
Looks like another trip to HF tomorrow is in line for feelers
Pic later after everyone has eaten
 
Here is the Post HF Pic
Needs a Paint job but it does have a Racing Stripe!
 

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This weekend I had frustrating time on my surface grinder.

I was grinding a 6" by 16" by .207/227" piece of CPM-S35VN. It hadn't been descaled.

Grinding off the scale on one side caused it to flex pretty dramatically (I'm grinding with coolant, so at least I don't have to worry about heat-related dimensional changes).

The end result was .020" of a bow (tapering down to the ends).

Just to make it extra frustrating, I was getting more than .001 of wear on my wheel per traversal (.005 of wear when cutting the scale). This was with a 3M SG wheel. I don't remember anywhere near this much wear grinding 1084/Cru Forge V.

The whole point of grinding a large piece like that was to get a better handle on what was really going on with my surface grinder, and it was certainly an educational experience.
 
Removing the scale on the other side caused it to move again.

Slowly it got flatter. And thinner.

Near as I can tell, surface grinding S35VN with the scale on it is a waste of time, at least on such a large piece (I'm assuming that the 6" by 16" by .2" is a factor). There's too much strain interacting with the magnetic chuck to be stable.

Next time I'll knock off the scale on my grinder and use either 3M double-sided tape or Black Max for the first side.
 
What is "Black Max?"
Got the Dial indicator going and it was off .001 on one end of the chuck.
Started at the high end and ground the whole thing Flat ...Again
Moral of the story is it came out Flat on 80% of the surface so where do I go from here???

Realizing that as you grind a large surface such as a Chuck you are also removing wheel heigth as you go. It stands to reason that towards the end of the grind will be higher than the start.

How do you compensate for the Wheel diameter loss?
 
Gabe Newell said:
Removing the scale on the other side caused it to move again.

Slowly it got flatter. And thinner.

Near as I can tell, surface grinding S35VN with the scale on it is a waste of time, at least on such a large piece (I'm assuming that the 6" by 16" by .2" is a factor). There's too much strain interacting with the magnetic chuck to be stable.

Next time I'll knock off the scale on my grinder and use either 3M double-sided tape or Black Max for the first side.
Click to expand...


Hey Gabe, if you buy me a double disk grinder, I will grind all your steel for free! :)

2thumbscool 1
 
Hankins said:
What is "Black Max?"
Got the Dial indicator going and it was off .001 on one end of the chuck.
Started at the high end and ground the whole thing Flat ...Again
Moral of the story is it came out Flat on 80% of the surface so where do I go from here???

Realizing that as you grind a large surface such as a Chuck you are also removing wheel heigth as you go. It stands to reason that towards the end of the grind will be higher than the start.

How do you compensate for the Wheel diameter loss?
Click to expand...

You might have been better off just shimming up that end of the chuck.
 
Calvin
I know squat about Magnetic chucks Etc...
Please explain: Are there any adjustments on these things? How can it be taken apart?
 
Hankins said:
Calvin
I know squat about Magnetic chucks Etc...
Please explain: Are there any adjustments on these things? How can it be taken apart?
Click to expand...


It basically just bolts down to the table. I what he was saying, I think, was to put a shim under it and bolt it back down to raise to low end.

I think you'd want to dust the chuck off either way to it's a small matter... When you grind the chucks, turn them on, that is how you are gonna be using it.... :)
 
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