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Mattison Surface Grinder - Suddenly getting a chatter pattern.

Tunash

Plastic
Joined
Dec 18, 2019
Location
NY
Hi Folks,

This is my first post on this forum, thanks in advance for any help you can give. I am in charge of maintenance at a machine shop that specializes in precision grinding. I used to build new machinery for the textile industry, so maintenance on this type of machinery is fairly new to me although I am very mechanically inclined (if I may say so myself, lol). I have been here just over a year now and have learned a lot in that time.

On our large Mattison horizontal spindle surface grinder the operator is suddenly getting a chatter pattern in his parts. He had been grinding the exact same parts/material earlier in the day and getting a great finish.

We have already covered a lot of the common issues I found in this forum such as wheel balance, dressing, glazing. All ways appear to be getting plenty of lubrication. He is an experienced operator. He has been running this machine for over 5 years, so I have to trust in his ability to dress properly and know if the wheel is clogged or out of balance.

I pulled the wheel sleeve off and checked the spindle for run-out, we had about .0005" total. I tried pulling up and pushing down on the spindle itself, but saw almost no play.

In the trouble shooting section of the manual it suggests that the cross feed gib could be loose. I located the gib and upon inspection found that I could put a .005" feeler gauge between the front gib and the way. This seems like to much to me, but I can not find an adjustment procedure. The rear gib will not allow even a .003" feeler gauge to enter.

I was going to adjust the front gib just to see if I could close up that gap, but no matter which way I adjust it the gap remains about the same.

I do have a call in to our local machine repair guys and I am waiting to hear back from them. In the mean time I figured I would see if anyone had any suggestions here.


20191218_104734.jpg20191218_104752.jpg20191218_112752.jpg
 
Do you have pictures of the bad surface finish? That will tell a lot more than pictures of the grinder.

I doubt that your problem is in the cross slide. Being that the grinder suddenly is starting to give a bad finish suggests wheel or setup issues.

Mechanical issues usually come on gradually unless something is actually broken.
 
Yeah a sudden change would seem to indicate something like the wheel coming loose, insecure workpiece mounting/holding or maybe a bad dressing with a dull diamond.
 
Thanks Guys,

I did not get a picture of the parts with the bad finish, he had fixed them on another grinder before I got the chance.

We are going to put the wheel back on and try again. I think you guys may be onto something with the loose wheel suggestion. As I was cleaning things up I noticed the threaded holes in the wheel sleeve were a little beat-up. I will chase the treads and see if that holds the wheel better. I am thinking that maybe one of the three wasn't tightening up completely, and finally it was enough to allow a vibration to cause the issue.

I will keep you guys posted. And thanks again for your advice.
 
I can't remember the exact setting procedure for the gibs, but .001 at the tightest section of the travel would be a good starting point.

I once worked on a Thompson that had a similar issue. On that machine, the spindle housing bolts to the cross slide way. The bolts were all either loose or broken off. I suspect that they were not tightened when the machine was assembled after some kind of repair.
 
As others have said, the problem is most likely not in the ways. Grinding wheels can crack with no easily identified evidence. Or they can shift on the arbor. Or need dressing - Sometimes aggressive dressing. Also, check to be sure the wheel is not consumed. I've seen cases where the bond is so similar to the wheel that the operator was not aware the wheel was gone.

I would change the wheel out with a new one and see if the problem persists. Hope this helps.

Best Regards,
Bob
 
Thanks again Guys,

Your advice is much appreciated. I think we have it fixed.

As I mentioned in my second post, I noticed the threads in the wheel sleeve we beat up. I cleaned them out and also got some longer bolts so we were grabbing in the good threads deeper in the hole. We used the same wheel to see if we had made any improvement. After he dressed the wheel we did a quick test piece, it looks good. Tomorrow morning we are going to try a few more pieces and see where we are at.

So I am thinking when he put on the wheel and tightened the bolts, at least one of them wasn't tightening up completely against the wheel but rather just getting jammed in the bad threads so he thought it was tight. Maybe this held the wheel enough in the morning, but allowed it to work loose as the day went on.

At this point I think we have it fixed thanks to your help. I will let you guys know if anything changes. Thanks again. Best Forum Ever!!
 
When you tighten the gibs on the wheelslide, set the gib by hand as tight as you can go, then tighten the set screws 1/4 turn. Then tighten you SHCS. One thing I noticed in your pics is that area looks pretty crusty. I would clean everything and then make sure your lubrication is working. If your ways are dry and you tighten the gibs you will make your situation worse.

When we have had this kind of situation on our grinders the first thing I do is pull the wheel and do a ring test, possibly the wheel is cracked, that will leave a funny finish.

If you are in need of wheel hubs, I have Mattison Wheels hubs in Stock.

We just completed a spindle rebuild on one of our Mattison SSG's

The Kinetic Co., Inc. on Instagram: “Big day today! 😎 Installing the spindle on one of our Mattison grinders that went down and needed rebuild. The stator needed a rewind,…”

Did you check your spindle lubrication? Do you have ball bearings on you machine or a sleeve bearing? If you have a lubrication unit on the back of your spindle it is a sleeve bearing. Make sure this unit is functioning properly.
 
Thanks everyone,

I just wanted to fill you in that we did not solve the issue as I stated in my last post, but we've got it working now. When we did another test in the morning we still saw a very light pattern in the finish. It was hard to even get it to show up in a picture, but it was there.

We switched wheels to eliminate that possibility. When the operator went to dress that wheel I could hear a quiet humming noise coming from the base of the dresser assembly. But he said he had been hearing that for a month now (I didn't know that)

A little background. Back in February my boss asked me if I could come up with a more efficient way to dress the wheel. The top mounted wheel dresser was long gone. He had been using a block that was mounted down next to the chuck with a dresser mounted in it. Every time he dressed he had to come down off of his parts, dress, then go back above the part and come down till he made contact again. Obviously this was costing a lot of time. I went to Bourn & Koch first, they wanted $6,500 for the top wheel dresser assembly. I wanted to try and see if I could come up with something myself, I love those kinds of projects. Plus it looks like the machine has been modified and I would have to make some changes for the original dresser to even fit.

I ended up buying a scissor jack designed for a motorcycle for $210. When I got it there was some slop when raising and lowering the jack. I did some machining and used some bronze bushings to get rid of the play. It worked great for 10 months, hopefully I will just find that the bushings are worn, then I can get it functioning again for just a few dollars.

So long story short, after screwing around for a day, it was just a bad dress caused by a vibration in my dresser arm lift. He went back to his old method of dressing and the chatter pattern went away.

Thanks again everybody

PS. If someone can tell me why my pictures keep getting flipped over I would appreciate it. lol
 

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I have some top dresser sticks in stock as well..... slightly used but fit for duty. Well less than B&K price.

I have a used over the wheel hydraulic dresser in stock, it needs to be rebuilt.

I like your scissor jack idea, that is pretty slick!
 
PS. If someone can tell me why my pictures keep getting flipped over I would appreciate it. lol

The pictures were taken with a phone, correct? Phones embed into the image which direction is "up" but sometimes they do it erratically, especially if the phone is held at a slightly off angle when taking the photo.

The best way to correct it is to open the photo in a legit photo editing program on your PC instead of your phone and rotate it there then re-save the pic. That will correctly change which end is ID'ed as "up." Most phone photo editing programs don't seem able to do this.

There is a shortcut you can use on a phone too but it will degrade image quality. Open the pic in a photo editing program on the phone and rotate it to the correct orientation, then take a screenshot. Attach the screenshot instead of the original photo and it will be right side up.
 
scissor jack designed..looks like a good idea.

Any chance a pair of pull down springs would hold it tight to the down position so make the bushings less a factor to movement.
Guess I would mount a plate to the bottom for better magnetic holding.

Only 4 posts..? You could add some more input to the site. post more often.

I never hung a grinder from the roof but if that works....
 
The pictures were taken with a phone, correct? Phones embed into the image which direction is "up" but sometimes they do it erratically, especially if the phone is held at a slightly off angle when taking the photo.
...
The problem is with the software handling the pictures on this forum not recognizing the orientation information now in the metadata of most every picture. Modern image editing software recognize such information, therefore most of the pictures edited with such software would still show up the wrong way here. Saving the picture as a new file, a different size and/or format would likely solve it.

Paolo
 
They don't still show up the wrong way for me. I just did it yesterday for one of my grinder pics taken with a phone that initially posted upside down here. I've done it a lot of times with same result on this and other sites too. I use Photoshop on the PC.
 
I like your scissor jack idea, that is pretty slick!

The idea is good, but the mechanism itself doesn't seem like it would be stable enough to be reliable. If there was some way to put a (dustproof) indicator against the diamond holder I'd bet you'd see some movement there in use, and that can't be ideal...
 
Paper blotters on your wheel can take a compression set over time and shrink. Try snugging up your wheel bolts.Redress wheel including the sides and rebalance.
 
Paper blotters on your wheel can take a compression set over time and shrink. Try snugging up your wheel bolts.Redress wheel including the sides and rebalance.

Holding screws can also take a set if tightened on the same width wheel for many years..Good to run screws in with no wheel and see they go past the wheel width smoothly .. with any deformation in screw they might be replace with new high-grade screws.
 
The idea is good, but the mechanism itself doesn't seem like it would be stable enough to be reliable. If there was some way to put a (dustproof) indicator against the diamond holder I'd bet you'd see some movement there in use, and that can't be ideal...

I was worried about the stability from the beginning. Quite honestly I was a little surprised it worked good when I installed it initially. It did seem to work for about 10 months though. I've got it on my work bench now for inspection, but I've got my hands in a few other machines at the moment.
 
It looks like set long ways would make it it a little more vibration free, less tip-over prone and a hold down spring (s) would make it more solid. Perhaps replacing some of the pins with screws and nuts so locking it solid at set-height.
I like to set a dresser height so it becomes my spotter so I know .002 or .0005 down dial from diamond position will make print limits. Yes a diamond will wear but still I have run a whole days worth of parts with only slightly changing my down dial number.
 
I would mount your dresser left of that handwheel up high
That is the ideal place for it
If the stone cannot reach that far you can mount it on that casting any convienient place
With a nonius on it you can dress by moving the wheel all to the front Back of a certain amount (always the same amount to remember it easier )
Next time you dress you go deeper a certain amount Then you know exactly how much smaller your wheel has become
You can lower the wheel that amount and you are back on track
Or put a DRO on it
Also easier to make a stiff set -up
Also no need to align anything
Here is a example
Google Image Result for https://www.bmtorino.it/en/resources/bmtorino/images_machines/Rettifica%20Tangenziale/4241-FAVRETTO-RTF%2060-131003__thumb_668_501.jpg

Also looking at this picture I see Mattison uses the same set-up
WZ Tool | CNC Machining and Product Gallery | High Quality Precision

So probably there is a machined surface on your machine prepared for the dresser

Peter
 








 
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