Base grinder finish Issues

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stormyclouds
Posts: 45
Joined: Mon Jun 04, 2012 1:24 pm

Base grinder finish Issues

Post by stormyclouds »

I have a grindrite st600. Im achieving a great finish going though all the grits and then finishing with a scotchbrite belt. I get little ripples on a few of my belts for some reason. I thought maybe the bearing were going bad on the roller but it some belts work great. Any ideas? IS it a speed/pressure issue? Thanks!
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skimann20
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Joined: Wed Feb 27, 2008 8:28 pm
Location: Taxachusets

Post by skimann20 »

do you have a picture of the ripples? that would be helpful
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Dr. Delam
Posts: 423
Joined: Thu Feb 01, 2007 10:07 am
Location: Truckee

Post by Dr. Delam »

I've got the same machine and I think I am getting the same problem. My guess is what you are seeing is from the seam. I've only run two belts so far and both produce a mark from the seam, even after doing some dulling with a stone. One belt was a 3m and the other was from Econaway.

Another thing I noticed is the contact wheel is very hard. I've never worked on a machine with this hard of a contact wheel. I think this really contributes to the problem. I wish my machine had a softer contact wheel for autofeed finishing. Trying to get one is probably next to impossible and/or as much as I paid for the machine.

The manual suggests lowering feed speed but I think this would just put the ripples closer together.

Stormy, may I ask where you got your scotchbrite belt?
stormyclouds
Posts: 45
Joined: Mon Jun 04, 2012 1:24 pm

Post by stormyclouds »

I bought my scotchbrite belt at www.svst.com. Its 320 and makes the base buttery smooth. I also have a 420g wax buffing belt from Fintech abrasives.

I was thinking the seam as well. My 80g and a few of the 120g that came with the machine do not leave marks. All my new ones do. I knocked the grit down with a stone as well as spot stoned the actual seam which seamed to help. On some belts you can actually hear the seam moving across the platen.

If this could only be figured out I would be in heaven. After sanding 220 and scotchbrite the finish is amazing accept for the little marks.
gav wa
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Joined: Tue Feb 18, 2014 8:58 pm
Location: Perth

Post by gav wa »

Just chucking it out there, but when i grind by hand i find upping my travel speed a bit helps prevent the ripples.
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Dr. Delam
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Joined: Thu Feb 01, 2007 10:07 am
Location: Truckee

Post by Dr. Delam »

I busted out a new belt today and this one was much better. I also hit the seam a bit more on the other ones and it helped but still noticeable.

My other issue with the machine is that with the hard contact wheel the edges don't get hit if there is a base edge bevel. It's almost like running a stone grind where you are just hitting the base and not the edges. Today I tuned a few pair and in order to clean up the base edge and lightly sharpen I had to remove quite a bit of base material and it removed the base edge bevel. I then put a one degree base bevel by hand with a guide which I don't really want to have to do each time I want to do a minor tune up. Other machines I have worked on had a softer contact wheel that compressed a bit and ground the plastic and edge bevel evenly. I don't really want to increase feed pressure too much either as that would take off too much base material.

Anybody with this machine care to chime in on your solutions and techniques?
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