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TOPIC: Hummel Sander Leaving Chatter Marks

Hummel Sander Leaving Chatter Marks 28 Oct 2014 23:43 #12081

I have a 2007 Hummel 8" sander that is leaving chatter marks in the floor. I have replaced the upper assembly and the drum and I have replaced the fan bearing and the fan belt and it is still leaving chatters all over the floor. I feel like it is happening after the machine has been running for a few hours because it does not leave chatters right when it starts up. We did a job that was dark walnut 400 ft and no chatters, but the next day we did a job that was 1600 ft and there was chatters all through it. The chatters seem to be very tight together.

Any suggestions on what could be going on with the machine?
Thanks.

Hummel Sander Leaving Chatter Marks 29 Oct 2014 07:47 #12082

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check the weights on the drum and cover for loose areas
check tension on the belts
occasionally paper is responsible for chatter

Hummel Sander Leaving Chatter Marks 29 Oct 2014 16:50 #12085

  • tdmac
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I also have had those problems. We had waves, almost like chatters but farther apart in the floor; cleaning all the wheels cleared that up. I had my side wheels lathed down 1/64th
The bearings on the top roller went bad and caused a chatter. . I replaced them my self. those bearings do heat up and will cause the paper to skip chatter.. After an hour check those for heat! Even a new roller assembly could have bad bearings. They are easy to change and easy to find for $15.00 each..
Keep us posted.

Hummel Sander Leaving Chatter Marks 30 Oct 2014 16:02 #12090

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Chatter can be a nightmare.. it had me going crazy an entire summer because of a bad drum..

Hummel Sander Leaving Chatter Marks 30 Oct 2014 17:49 #12091

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Why is the drum bad.?? lose some weights? packed with dust dirt? Can it be saved? just wondering since my drums are 7 yrs old!

Hummel Sander Leaving Chatter Marks 03 Nov 2014 19:26 #12102

  • Avi Hadad
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The only times I had chatter with my Hummel was because of cheap belts and vibration from the sub floor.

Hummel Sander Leaving Chatter Marks 12 Nov 2014 12:31 #12124

The only time I've chatter marks were from improperly tensioned drive belts

Hummel Sander Leaving Chatter Marks 01 Dec 2014 08:54 #12276

It's a crummy sanding belt. At least when I get chatter from our Hummel that's what it is.
Christopher Hodges - Owner
Columbia River Hardwood Floors, LLC
SW Washington's, #1 Wood Flooring Contractor

Hummel Sander Leaving Chatter Marks 12 Dec 2014 02:34 #12366

  • Pony Deal
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I agree with Avi. A loose subfloor can cause the problem.

My standard procedure now, with my 8" Hummel, on a resand, is to
45 the floor with 80 on the first cut, 45 with100 on the second in the opposite direction and then
100 on the 3rd, going with the grain.

The Hummel is such a powerful machine that you can usually do the
above without any problems.

Many of the other suggestions given can cause problems as well.

But a loose subfloor is always the first thing I worry about and look for.
Last Edit: 12 Dec 2014 02:37 by Pony Deal. Reason: additional comment added

Hummel Sander Leaving Chatter Marks 12 Dec 2014 12:41 #12372

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Pony, Wow...on our standard refinish we start with 36 grit, may times on a 45 degree, then 60 grit on our 8" hummel. then 80 &120 screen!! How do you do it with a 80grit? Wow!! the chatter is many times from that top roller!! Need new bearings. $10.00 each and easy to replace.. :whistle:
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Hummel Sander Leaving Chatter Marks 12 Dec 2014 16:31 #12376

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Make sure you are emptying the bag before it gets half full. A full bag will inhibit the vacuum & you'll find the sander leaving clumps of dust which your wheels run over. This can leave chatter-like ridges which will extend across the floor as you run your wheels across them.

Hummel Sander Leaving Chatter Marks 12 Dec 2014 22:15 #12381

  • Pony Deal
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tdmac,

I used to use heavier paper but I found on most resands that the Hummel was capable of roughing
off finish with lighter grits. Commonly, I rough off with several used belts that have some cut left
on them. You just have to watch out they don't overheat and weaken the seam.

Using finer belts leaves finer cross lines to sand out and brings up fewer nails. That also means
less to set and goop. Less money spent on belts and more efficient use of used belts.

Cross sanding the first two cuts gives a nice flat floor without chatter or wave.

When I have to patch, I first try to flip damaged boards, using the existing wood for a better match.
If i have to replace some wood with new, I mix it in and blend with the flipped existing boards.

I then rough it off with the Hummel on a diagonal with as light a paper as possible and then dial
it in with the edger before roughing off the rest of the floor.

I only goop the floor before the last cut with the edger and big machine. It stays in better.
Not like the old days with Superior . That stuff never came out!
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Hummel Sander Leaving Chatter Marks 16 Dec 2014 13:29 #12394

Inferior quality sandpaper and subfloor issues are definite culprits to consider. While it is simple to address the former, not so much can be done for the latter, although as a general rule, a machine in an optimum state of tune, using top quality sandpaper isn't apt to leave as extensive chatter in a bad subfloor situation as a machine that is in some other lesser state.

The motor-driven moving parts of the machine all play a role in how smoothly your machine runs, and therefore, the degree of chatter you may or may not experience over the variety of conditions you are likely to encounter in floor sanding.The condition of V-Belts, V-Belt Pulleys (especially aluminum idler pulley that secondarily adjusts tension to vacuum impeller belt) should be examined, replaced as necessary, and tuned such that BOTH belts run as smoothly as possible at the same time. Upper Roller unit should be removed (see your Owner's manual) at least weekly for cleaning (thorough use of a good vacuum is recommended to remove wood dust). Upper Roller and Guide Rollers should be inspected for excessive wear, as well as and how well they are fastened into place. Loose fasteners should be tightened or replaced as needed. Bench test the bearings by giving the revolving part a swift spin by hand. The manner in which it comes to a stop is key: It should spin for no more than a second or two and come to somewhat of an abrupt stop. Its rolling should be smooth and quiet. If it spins freely and seemingly on and on, the bearing(s) is/are no good as this is an indication that the grease that is supposed to be inside is largely gone and no longer provides resistance to spinning. A bearing like this often bears an accompanying noise during this test as well. Of course a bearing that is entirely seized warrants immediate replacement of that part.

The Drum should be removed and inspected regularly (see your Owner's Manual) for damage, wear and missing balancing weights. Any dust that may have accumulated in its main cavity must be cleaned out to avoid an out-of-balance situation. The cost of replacing any Drum that's been adding any perceptible time to the sand job due to its condition should be considered a very wise investment.

The one bit on this topic that has NOT been mentioned on this thread is the Drum Nut that secures the Drum into place: It most definitely should be noted that one side of this nut has a very pronounced recess cut into its threads to allow clearance for the unthreaded portion of the Drum Shaft that protrudes from the Drum once it is pushed onto the shaft all the way. This means that the Drum Nut MUST be installed such that this recessed side faces inward against the Drum so that it pushes against the Drum's body upon final tightening, thus securing it in place for use. A Drum Nut installed incorrectly (with the recess facing outward) will tighten without properly securing the Drum in place. Usually one can feel "slop" between the Drum Pulley and the Drum when they are rocked by hand back and forth with respect to each other when the Drum Nut is incorrectly installed. The result of running your machine with an incorrectly installed Drum Nut is going to result in frequent chatter. It can usually be corrected by simply flipping over the Drum Nut, but if it has been run this way for too long, the Drum may need to be replaced.

The condition of your Drum Shaft, Drum Shaft Bearings, Motor Bearings, Motor Shaft, and Dust Fan Unit are also relevant items to consider, though if we are looking at a list of "Usual Suspects" for the chatter you describe, these tend to fall much further down that list as opposed to what's already been mentioned.

Remember: Keep your sander clean! Read your Owner's manual. Always use the best quality sandpaper you can get and employ proper sanding methods. Keep your machine in a good state of repair and always buy OEM parts!

Hummel Sander Leaving Chatter Marks 25 Aug 2015 14:32 #14613

  • UFOMAN
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Hi guys, new to the site but bought my first Hummel in 1987. Ive probably got 2-300,000 ft behind me at this point. I do all my business with Leese Flooring in Ct and US Sander in NY and got a tip from one that the other then affirmed. After all the technical data you guys threw out, I'm iimpressed. Obviously I'm not the only tech nut out there in" the business that we have chosen." I think chatter as more of a slotted drum problem. My guys call it the Hummel wave and comes from leaving the belt tension on a hot soft drum after running it for a while. The drum gets a flat spot when at rest and produces the Hummel wave. Obviously it will be worse if you happen to leave the belt on overnight. As soon as my drum stops spinning the tension is released on my Hummel. I've also owned a UFO for a dozen years, thus my affiliation with US Sander, and have custom made some of my own driver pads in case anyone is looking for some upgrades to make your UFO a 16"edger. I cut all my edges with my UFO and my back feels so much better. I havent used an edger 5 times in the last 5 yrs.

Hummel Sander Leaving Chatter Marks 25 Aug 2015 19:21 #14623

  • Pony Deal
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Obviously, one never leaves the drum down on the floor
when not in use.

It's also a good idea to take off the paper and release the
belt tension if the machine is not going to be used for a while.

One of the leading causes of chatter on a slotted drum
machine is that the edge of one side of the slot is slightly
higher than the other.

When you condition/sand your drum, you have to spin it
in BOTH directions!! You have to get an oversize drum
belt to do this and you have to install it in a crossed 8
configuration. You also have to tie or chain the sander
down because , when you drop the drum on the sandpaper,
the machine will try to come towards you.

Once you condition the drum in both directions, it should
sand perfectly flat without chatter.

I also staple my paper shims on the inside of the paper
so that they push the edges closer together and reduce
the gap.

Hummel Sander Leaving Chatter Marks 26 Aug 2015 23:03 #14644

  • CF12Driver
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WOW!!! :woohoo:

Hummel Sander Leaving Chatter Marks 27 Aug 2015 20:17 #14654

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Sorry guys i should've proof read better. The Hummel wave I was referring to is caused by leaving the sanding belt on with the tension on andleft long enough causes the flat spot which then makes the waves. Haven't had anything but perfectly flat floors since I started attending to my belts more closely and make sure as soon as my drum stops spinning the tension is released or the belt is removed. Another cause for waves can also come from not cutting new flooring "over wood" on an angle and rounding over all the high butt ends. When doing wide flooring I sometimes hit all the butts first and then cut the entire floor. I cut all my new floors on a 45° angle to level out all the butts. I do the same on refinishes also so I make sure I don't follow a prior poor sanding job. Angle cuts with my Hummel and a 60 disc cut across the field with my UFO then an 80 screen and you have a very flat floor that's so smooth it shines. Took me years to get my grit progressions and order down but feel I've got it figured out at this point. I also use my UFO to do all my edges normally with a 36 grit. There's so little edge left I use a little 3" Metabo hooked up to my Proteam vac. I might have used my edger last year and I think that was on a subfloor. Interested in how some of you guys do your floors from start to finish and the equipment you're using.

Hummel Sander Leaving Chatter Marks 27 Aug 2015 21:17 #14656

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UFO man.... I think its is the wheels that have flat spotted!!! I have had 2 12 " super Humells and 4 each 8" hummels and the damn wheels are always the problem. Had them lathed smooth and VIOLA fixed that problem. Never had what you are talking about, but that's is just an Ol Farts' assessment!

Hummel Sander Leaving Chatter Marks 27 Aug 2015 23:29 #14661

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Always been one to respect my elders and have only been a member for less than a week and it's obvious to me I'd be smart to consider your opinion. I do a lot of R & Qtd thus vertical grain and other tthen wide fleck bands expect near perfectly flat floors so when I saw the ripples the time it happened to me you're right, the first thing I did was order wheels. So it could well be thats what fixed it. I do however hhave much respect for the guys I got the info from so I've made a point to never leave a belt on with tension on it. Honestly I do so much UFOing I might not see the damn waves if I was still making them. Whatever the cause its definitely exasperated if the flooring is loose. I get that a lot here in the Northeast. You know the drill, when they put the planks down across the joists and the flooring across the planks the hardwood is all running with the joists and after a few years of seasonal movement the fasteners all pop and the floors are floating. Makes for a frustrating job. Don't know if you see that much where you are. Looking forward to running stuff bye you from time to time, I'm not an old dog yet I'm happy to learn some new tricks.

Hummel Sander Leaving Chatter Marks 05 Sep 2015 18:41 #14725

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My Hummel is one of the first sold in this country in the 80's. Still running the original drum and motor. I rarely do any maintenance, I've cleaned the roller a few times and grease the fittings when I hear a squeek. Replaced the roller and vacuum fan once and the wheels twice. I expect a motor rewind eventually. Only chatter ever is from an occasional loose subfloor. No wave, I think in part to Gary's recant of the Hummel owners manual...

On the first paper (36 in my world) cut at a 5-7 degree angle. Second paper (50) cut at 5-7 degrees the opposite direction and straighten it out on the final (100). The main problem I have had over the years is ridges, (which can happen on either side), this has really helped out a lot. Hardest part is deciding what is 5-7 degrees.
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