bsky4463
fully equipped rock polisher
Member since September 2013
Posts: 1,696
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Post by bsky4463 on Sept 25, 2013 9:36:20 GMT -5
When is a drum ready for replacement? What are the signs?
I recently picked up a vintage Star grinder which has an expandable drum/belt setup on one side. The drum is throwing small bits of rubber. Additionally, the expansion ribs are showing some cracking - at least on the outside. I have used the grinder once and its seems to be performing well. So while I realize I will need to replace the drum - I don't want to do so prematurely.
Many thanks for your input
Cheers
Andy
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Roger
fully equipped rock polisher
Member since January 2013
Posts: 1,487
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Post by Roger on Sept 25, 2013 21:30:42 GMT -5
If the belt stays secure and you are still able to use the full width without the belt "catching" on the stone, you should be okay. If the belt moves around or there are soft spots, it is probably best to replace the drum.
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bsky4463
fully equipped rock polisher
Member since September 2013
Posts: 1,696
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Post by bsky4463 on Sept 26, 2013 15:56:31 GMT -5
thanks - that was my hope.... Belt is staying put so I will let it ride for now, no need to spend unnecessarily. Cheers.
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Post by Peruano on Sept 26, 2013 18:08:32 GMT -5
I wouldn't take the chance on that drum. If its really deteriorated, it can eventually give way and come off like a banchie and do some damage to the operator. Yes the belt provides some resistance to it flying apart but we have all seen those belts give way due to age, abuse, etc. Change the drum and don't risk your safety. JMHO. Tom
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barclay
has rocks in the head
Lowly Padawan of rocks
Member since November 2011
Posts: 510
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Post by barclay on Sept 26, 2013 20:25:38 GMT -5
I would also go with replacing the suspected bad parts now versus later. In addition to hurting you when it flies apart it could fling your stone across the room never to be seen again  |
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Sept 26, 2013 21:20:27 GMT -5
Also you should never run an expandable drum without a belt on it. This can damage the drum.
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Post by pghram on Sept 27, 2013 10:47:53 GMT -5
Always better safe than sorry, or injured.
Rich
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bsky4463
fully equipped rock polisher
Member since September 2013
Posts: 1,696
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Post by bsky4463 on Sept 27, 2013 11:44:05 GMT -5
Good points from all, thanks for the input. I decided to error on the safe side and order a new drum - maybe I am getting smarter as I get older...probably not, just getting better advice.
Also great point on not running the drum without a belt - fortunately I read that before I used the machine.
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Post by Rockoonz on Sept 27, 2013 11:55:10 GMT -5
Good points from all, thanks for the input. I decided to error on the safe side and order a new drum - maybe I am getting smarter as I get older...probably not, just getting better advice. Also great point on not running the drum without a belt - fortunately I read that before I used the machine. All drums are not created equal. The Rayspans are Asian made and short lived compared to the Lortone (Scott-Murray) made in the USA. Also when installing mind the spin direction. Lee |
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Post by mohs on Sept 29, 2013 22:20:05 GMT -5
I just bought this new expandable drum  my old one was whacked and out of round it got dropped in just the right way again  do I have this wheel mounted the right way for spin? Thanks! Ed |
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Post by Rockoonz on Sept 29, 2013 22:49:56 GMT -5
Yep, mounted correctly Ed.
Lee
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spicer m
spending too much on rocks
Member since October 2008
Posts: 337
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Post by spicer m on Sept 29, 2013 22:51:36 GMT -5
Yes Ed You do
Mike
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Post by mohs on Sept 30, 2013 0:19:54 GMT -5
I'm on roll now !!!
thanks, guys!
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Post by bobby1 on Oct 2, 2013 9:00:33 GMT -5
I like my drums to run softer so I have my machine running at about 1450 rpm. If you want it to run softer you can reverse the direction. It doesn't hurt anything.
Bob
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Post by mohs on Oct 2, 2013 13:33:08 GMT -5
I'm not exactly sure what you mean by softer and reversing direction
But its interesting
My theory is to run the wheel at the slowest speed possible
and still maintain an efficiency of cut.
With a targets speed of around 1400 to 1500 wheel surface speed
Give or take a few rpm.
My reasoning behind this is that it gives tiny abrasives more time to cut.
Does this make any sense?
mostly
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Post by Rockoonz on Oct 4, 2013 11:51:35 GMT -5
Reversed direction will work as long as you use a light touch, bearing down hard could cause the belt to slip but as Bobby says it won't hurt the drum, only thing that can cause damage is running without a belt. My Graves 6 inch grinder has a 2 speed motor and the belt grips fine at low speed which if I recall correctly is about 1400.
When grinding and rough sanding to 600 I like using the lower speed.
If you use diamond belts all the way to 14000 or 50000 I think that with hard jaspers and agates using a higher speed to warm up the surface of the rock a little will result in a higher gloss.
Ed, what do you glue your hearts with? I have a project that will require a super strong bond and not sure what to use.
Lee
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Post by mohs on Oct 4, 2013 22:08:41 GMT -5
Thanks for the advice on the speed, Lee
I'm using the Hughes E-330 on the hearts
Its working really well !
Superior even.
I started with E-6000 on the hearts.
It was good-- but its biggest drawback is that it doesn't dry clear.
Plus it is only rated at 150 degree heat resistance
I have many 5 year old rock'n hearts that are bonded with the E-6000
no broken hearts
and many have gone through considerable abuse
I can't same the same for my own
I've been wanting to experiment with some other expoxies.
I think Loctite as a really good product.
What I'm looking for besides strenghth is the bonds heat resistance.
Loctite claims its bond stay stong up to 300 degrees.
This is important for dopping & heating that stone for a final polish
(I can't seem to find technical data sheet on the Hughes E-330
so I don't know what it heat rating is?
Although I haven't had a problem when dopping the hearts.
But I real careful not to get it to hot in the final polish
this might account for my less than stellar shine
I'm working on it)
Anyway I hope this season to have more data.
Happy Intarsian !
Ed
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Post by mohs on Oct 4, 2013 22:24:35 GMT -5
O I would add because of the rocking heart design
and the skimpy bond in the middle of the two stones
there is lots of stress put on that bond through out the grinds.
I'm always amazed at the strenghth of these expoxies
I mean.... the rocking hearts as got to be one most stressful type
of intarsia project to expect from an epoxy bond.
Plus I dop the hearts on both sides & double dome.
So that bond gets a real workout
I've tried to break a heart by hand
it withstood heavy handiness
mostly
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Post by bobby1 on Oct 5, 2013 21:04:21 GMT -5
Running softer means the speed is slower and the drum doesn't get as firm. A softer belt/drum allows the surface to conform to the cab's surface and it removes the mini post grinding flat spots better.
Bob
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bouldergal
freely admits to licking rocks
Glacier Meadow
Member since July 2007
Posts: 783
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Post by bouldergal on Oct 10, 2013 22:45:38 GMT -5
I'm not a fan of expandable drums.....my neighbors in Florida loved them! OK, you wonder why? Because they loved watching me chasing them down the driveway when they flew off of my old HP combo unit!  |
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