# help! 12" disc-sander trouble!



## AlWood (Apr 18, 2010)

Folks, I am mostly lurker, you can look at me as a newbie (at this forum) and a hobbiest with some experience... I like this forum very much: a lot of great experts and extremely resourceful people. 

OK, half year ago I purchased a combo (12" disc + 6" belt) sander from Harbor Freight (please, don't kick me in my rear; I've done it already many times myself with this sander, sigh...). Somehow I convinced myself I needed it, and nobody was there to stop me... When it arrived, I was too busy with my daywork projects, and didn't attend the toy for a while. I only discovered that both iron-cast tables were broken, but HF replaced them, and sent me some other replacement parts, and that was it.

It is a beast of a machine, but when I finally (with great delay) tried to get it to work, I discovered a lot of poor fitting here and there, but was able to get over that step by step by hole drilling, filling, making a wrench for semi-hidden bolts, etc. But here is a trouble I don't know how to deal with. A 12" disc is made of aluminum, and it vibrates like crazy; the wobble amplitude in the direction normal to its surface at the edge is 3/32"; everything (including my cat) around the sander is flying in all the directions...

OK, one possibility is that the disc is not flat. Indeed, when I put it on the surface of my table saw, I saw it being "un"-flat, by less than 1/32". I can try to make it flat by sticking a sanding paper to the table saw and trying to take that part of the wobble out by sanding the alum-disc. However, as I can see from the over-all wobble, the main part of the trouble is that the disc's hole is slightly off the line perpendicular to the disc's surface. (Notice: no vibrations when the disc is off.) Any idea how to handle that one? (and also, how to make the disc flat without sanding it on a table saw surface?)

Another (hope less daunting) problem is that the adhesive on the sanding paper (or whatever it is called) has completely dried out. What can be done with that one? Is it a contact cement, or anything else? Can I anyhow bring the dried-out adhesive back to life? If not, could I buy anything that would work for the aluminum+cloth surfaces?

Thanks a lot in advance! (and pardon my English..:huh
Alex


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## Kenbo (Sep 16, 2008)

I've got no advice on the hole problem, but a little double sided carpet tape should fix your sanding disc adheisive problem. Spray adheisive will also work. You just have to heat it up with a heat gun when you want to remove the disc.


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## Gary Beasley (Jan 21, 2009)

Have you contacted HF about a replacement disc? If you don't trust getting a good disc from them then take the disc to a machine shop and have them drill the hole out on center and true and to fit a steel bushing in it to fit the shaft. Might be more expensive than the machine was new.


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## AlWood (Apr 18, 2010)

Kenbo, thanks! As I have no idea what are those spray adhesives (and carpet tapes either -- there are big holes in my education, can you give me a couple of most common names? and places? (Home Depot?)

Gary, right, I'll be trying to get a replacement disc from them, but it is too late to get it as faulty item (more than half year has passed); will try to buy it from them, but as you understand, precision is not their cap of tea.... Will try. Great advice of going to a machine shop, though.. As long as I am there, may ask them to redo the entire thing for me...


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## AlWood (Apr 18, 2010)

Oh, Gary, one more thing: can I use the heat gun (actually the only thing I have around is a hair-dryer) on the dried-up adhesive sitting already on that disc? Will it (adhesive that is) stick?


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## Colt W. Knight (Nov 29, 2009)

I bought a HF 6x48 belt sander/disc sander when I was in Highschool because my grandpa had the exact same one for nearly 30 years. He did replace the motor once, but its still going strong, as well is mine. Mine doesn't have a 12" disc though, I think its 9 inch. Whatever it is, its an unussual size, because its tough to get quality discs for it. The only problem I have with mine is that the table for the disc sander only has support on one side, so you can't get a perfect 90 degree angle. 

When I apply those discs, I heat up the aluminum disc and the sanding paper with a 1500 watt heater, the stick it on. Most spray glues are designed to be peel and stick, so you have to buy one that is more permanent. Ussually when spray glue comes out, it is cold and filled with propellant. You have to allow it to warm up and the propellant to evaporate to get good adhesion. Its nice when your applying paper templates because you have time to move the paper around, but not when your putting sanding discs on.


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## Nate1778 (Mar 10, 2008)

I like the 3M #77 multi-purpose adhesive, you can buy it a Home Depot or Lowes. You can buy carpet tape at the same locations, make sure you get the sticky kind and not the kind you have to heat up. They make two kinds. 







http://solutions.3m.com/wps/portal/3M/en_US/3M-Super-77/Super77/


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## Ghidrah (Mar 2, 2010)

Alwood,
What is the arbor size? If you can't expect to get a proper replacement from HF it's quite possible the Delta 12" disc shares the same arbor dim

Delta discs

I wouldn't suggest milling off the discs arbor run out it'll shrink the diam. I'd also stay away from trying to true the discs side, you'll lose too much metal and weight and may create another prob, a convex shape on one side may cause the sanding disc to loosen up due to centrifugal force. If you place a pad on that side

Lastly I use 3m Super 77 spray for tonza stuff including the 10" sanding/calibration disk I use on my TS. I've pulled a good pad off a few times and the stick side got dusty. Spray both and allow to tack before placement. I suggest making a short dowel to fit into the arbor, it helps aligning the sanding disc big time. 

If you don't mind losing 2" of disc there are the 10" Calibration discs that double as TS sanding discs


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## TimPa (Jan 27, 2010)

"disc not flat" i would try to flatten the disc on the ts flat surface some

"wobble on runout" try to shim the 2 mating surfaces, disc hole and shaft od. i don't think i read about the mechanical fastening method here - set screws? is there room for shim material? some shaft filing may be in order. the machine shop could true the face for sure.


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## Kenbo (Sep 16, 2008)

Spray adheisive is sold at home depot umungst other stores. I think they sell Elmers brand and it is sold in the paint and glue section. (not sure on that) It's about $6.00 a can.
Here's a link to 3M brand http://solutions.3m.com/wps/portal/3M/en_US/3M-Super-77/Super77/
Just to give you a liitle information on it. Heating the old adheisive will not regenerate the stickiness of it. Keep us informed.


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## Cincinnati (May 5, 2010)

Alex

It doesn't take much of an imbalance at 12" DIA to create a huge vibration issue at full speed. 

Runout and imbalance are two different issues. One way to check disk runout is to slide something (a piece of wood) onto the table and against the disc. Rotate it slowly by hand and let the wood push away. Then mark the high spot in the disc with a sharpie. Slide the wood back against the high spot and rotate the disc until the gap appears the largest. Measure it. I don't know what acceptable runout measurements are. I have a Shopsmith MkV with more runout than I preferred on the 12"disc but very little vibration. The sandpaper at the high spot does most of the cutting.

As far as correcting any problems, it is difficult with an aluminum disc. If you grind it flat, it may make the vibration worse by creating a bigger imbalance on one side of the disc. 

Can you look at the design and see a problem with symmetry. For example, If it has gussets on the back, do they appear fairly uniform in size?

How is the disc secured to the shaft? If there is a boss for a set screw or worse, a locking bolt to attach it to the shaft, is it overly large? If so, this is a design issue that you can't do much about. Just use the shortest fastener possible. 

If you can afford to sell it and buy a better design, do that. Otherwise, perhaps bolting it to a workbench or otherwise mounting the sander will effectively add mass and dampen some of the vibration.

How does it function - Are you pleased with the results on the wood?


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## AlWood (Apr 18, 2010)

Colt W. Knight: very informative; thanks a lot. As to your table: yes, I am familiar with the problem (the table is supported only on one side, so it is flexing), that is one of the reason for me to make my choice (the sander I bought has a disc table supported from both sides). About adhesive -- very detailed advice; great thanks, will know now what to do and which adhesive to pick. I realized however by now that my main problem is that damn aluminum disc; I cannot do anything before I solve the problem.

Nate1778 and Kenbo: the same; great thanks about sources and adhesives (and about carpet tape too; gosh, I didn't know that they come in two different kinds...) You guys have to be patient with me: with some stuff I have quite an experience, while there are things (tools and materials) of which I've never heard... Back in my youth (I even don't care to remember how long ago it was...) I was building cow-barn roofs and log cabins with an ax and a two-man two-handle saw in my old country and never have seen a stationary table saw, let alone a router... Whatewer...

Ghidrah: the arbor size is 5/8"; and you must be right, it looks to me that the entire thing was a Delta-clone. (Actually, the picture you referred to is of a disc-alone sender, and mine is a disc+belt combo, or stationary sander
http://www.ereplacementparts.com/delta-31735a-type-stationary-sander-parts-c-3275_4142_4145.html

which was also produced originally by Delta, but it doesn't make a big difference; I guess the arbor is the same, and the motor is the same, 1 hp). I fully agree with your analysis of forces on the disc, and frankly after a few tries (see below) realized that it is a time/effort losing proposition trying to fix this damn and unworthy disc; I better try to get another one from them (with a little hope to have a better sample), or better yet to try to get better one from Delta. BTW, I was pleasantly surprised with your mentioning TS calibration/sanding disc; I have the same and actually was going to buy another one -- a very stable and well balanced steel disc, a pleasure to work with. I'd be happy to put it on that new sander -- the hell with lost 2" -- but the trouble is that the arbor on the sander is designed differently from the one on TS (on TS it is kept the same way as a saw blade, by screwing in an arbor nut, whereas on the sander it is kept on the arbor by a little side screw/bolt sitting on the disc, the same way as with a pulley, which is a lousy way to set a large disc).

Cincinnati (and TimPa): thanks so much for looking into the situation in detail. Yes, I do understand all the factors mentioned by you. As far as runout -- yes, I've measured it as I said in my original post, although I failed to call it properly as "runout" -- another hole in my education -- it turns out to be huge -- 3/32", compare that with that on a saw blade, ~0.001", i. e. two orders of magnitude larger... I hear what you say (that it may not necessarily a big reason for vibration), but still I think it is large enough to scare the s**t out of me (let alone my cat... Imagine such a runout in your TS... Besides there is a substantial radial imbalance; and "unflattness" seen when I put it on a flat surface (TS bad).

I even went so far, as to make a "sandwich" to try flattening the disc -- two rough discs of the roughly the same diameter made of 3/4" ply (one with the appropriate hole in the middle) sandwiching my alum disc, and put a squize on the plies using a few clamps -- with no effect whatsoever (as one my envision....

Well, whatever -- I realized that the damn lousy disc isn't worth my efforts anymore. So far I stoically was taking the situation as a challenge to my wits, ingenuity, and persistence, but I've got enough of it. Will go for a new disc; if that one wouldn't work, you'll hear screaming curses coming to you in the night air from the crabby state of Maryland...

Oh -- thanks again guys; it is so nice to have so many people so willing to help. You saved my day by just being there to help.

Alex


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## Ghidrah (Mar 2, 2010)

AlWood.
I kinda flaked on your description. 

1. The arbor "fastening bolt" screws into the arbor and presses up to the disc?
or 
2. The disc slips over the arbor but the fastening bolt screws through a separate hole on the disc and then into the side of the arbor flange?

If #1 then that's not an issue, although the only place I ever saw that set up is on circs. At worst if the disc is recessed past the pressure point of the Arbor fastening bolt all you need to do is shim the offset with a bored out fender washer.


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## AlWood (Apr 18, 2010)

Ghidrah said:


> AlWood.
> I kinda flaked on your description.
> 
> 1. The arbor "fastening bolt" screws into the arbor and presses up to the disc?
> ...



Gosh, Ghidrah, you got me here; trying now not to get flaked myself:icon_smile:. OK, the way I see it, you are asking me whether it is (1) OR (2). If that is so, then the situation is as in (2): the disc has a thick extension (flange?) which accepts the arbor shaft; after you push the disc, it slips over the arbor shaft; and then a bolt sitting in a hole in that extension perpendicularly to the arbor shaft, is screwed in to press against the arbor shaft. So it is exactly the same setting as with a pulley sitting on a arbor shaft; simply imagine that you replace a pulley by a sanding disc...

If it is an arrangement (2), do you have an idea how to true the disc with the arbor shaft? There is no way one can put a shim between the arbor and disc extension -- everything is too tight ...


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## Ghidrah (Mar 2, 2010)

nOpE! I 9Ot yoU now, #2 was way out in left field foul territory. It was late, my body was a giant swollen crampy achy ball of jelly from digging raking and wheel barrowinginginging dirt from one side of my yard to another, me broin were a 'urtin and not working right. I'm still sore but the brain is working betterer.

Pulley wheel Allen set screw and keyway on arbor, (maybe with flat spot). I didn't pay attention to the layout and fastening mech when looking at the replacement disc. 

This might help.

Adapter


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## AlWood (Apr 18, 2010)

Ghidrah said:


> Pulley wheel Allen set screw and keyway on arbor, (maybe with flat spot). I didn't pay attention to the layout and fastening mech when looking at the replacement disc.
> Adapter


Wow, you've got me here real good!!! I am sure your backyard looks now much different when you looked at it this morning; hope you were digging the right side of it. I tried to decipher your instructions, and realized I need to do the same work with my backyard as you did to get tuned:laughing:. However by looking at the adapter in your link, I realized that essentially you are trying to suggest for me to convert #2 into #1. But it would not work; the flange on the disc is too thick to be engaged by that little adapter screw. Besides, with a large 12" disc, the entire thing would be so unstable and unreliable, I wouldn't dare to stay close to it when the motor is on...

Well, will have now to find me a right "digging" hole in my fridge, and do a real good digging till my problem goes away...:smile:


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## woodnthings (Jan 24, 2009)

*This sander is 12" HF*

http://www.harborfreight.com/12-inch-direct-drive-bench-top-disc-sander-43468.html
Not the combo unit however. The disc plate may be the same arbor size? the manual doesn"t specify. The cost is $110.00 if you must have a separate 12" sander, it may be cost effective to just leave the combo with the belt and ditch the disc portion. 

Their current combo unit is a *9" disc* and 6" x 48" belt:
http://www.harborfreight.com/6-inch-x-48-inch-belt-and-9-inch-disc-combination-sander-6852.html

A machine shop would probably true the bore with the surface of the disc correctly and sleeve the arbor. But it may cost more than a new disc from HF parts.
manuals from here: http://manuals.harborfreight.com/manuals/43000-43999/43468.pdf :thumbsup: bill


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## Ghidrah (Mar 2, 2010)

AlWood,
NOW YOUR JUST BLOCKING!
5/8-1/2" bushing
Diamond/Round Insert

Similar to original link but slightly more expensive with double inset screws
5/8-1/2" motor shaft adapter

If in your attempt to get HF to replace the existing disc fails for whatever reason consider the Delta replacement disc with the above accessories option or in conjunction with the 10" calibration disc you already have.


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## AlWood (Apr 18, 2010)

Ghidrah: blocking or not, I am running for cover!!!: all this adapter business is like trying to use a kitchen faucet to close that Gulf oil leak; it may be good only for small disc or pulley (I tested it on my grinder...)

woodnthings: thanks for getting into this little fry... That 12" disc-only sander has been already mentioned in this thread by Ghidrah. Let me go into more detail. I happen to be familiar with that one. A huge piece of junk, imho... 
(1) albeit 12" disc, it is attached to the motor shaft differently as compared with combo (in the sander shown by you, the disc is attached to the shaft
by using a fastening bolt that screws into the arbor and presses up to the disc; and Ghidrah was convinced too that this is the way it is done for combo -- but it is not!) . 
(2) When I ordered that one, disc-only couple years ago, it came with both "hind legs" broken; so I've sent it back; the combo is much sturdier. But then I've got a chance to see what that sander is all about, and realized that there is no way I'd want it at all (strongly recommend the same to anybody). 
(3) See, it is a direct drive machine; the disc is sitting directly on the motor shaft -- and I hope you do understand what that mean -- anything happened to the disc -- and the motor is gone. The same problem as in direct drive table saw as compared to e. g. contractor saw. In my combo unit I have a belt driven by motor. If anything happens, the belt would slip, and that's it. 
(4) Another major thing is that with that unit I have already the disc rpm reduced from that of motor by a factor of 2; and may easily install another pulley to reduce rpm even further. This is a huge plus, especially when handling different woods. 
(5)And the last but the least thing is that disc stability on both (single disc and combo) models is lousy... No point even to think about that single disc unit.

By now I can clearly see only two (actually one) options left. Either I purchase a similar disc from Delta (the damn thing is pricey -- with handling, delivery, etc will cost me nearly $150, more than 50% of the machine I bought -- and at that no guarantee that the delta disc would be any better!!! -- it is aluminum, for crying out loudly...) -- or will try to get replacement from HF for free or simply buy it from them, and will be sending back anyone of them that make that terrible vibrations... Will be calling them on Monday. Will let you guys know how this sander saga ends up...


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## Ghidrah (Mar 2, 2010)

Alwood,
Truth, your suggestion may be so, the only adapter I ever used was for router bits on my RAS. My only concern was that the inclusion of the adapter might have interfered with the disc to table spacing.

However, many saw blade brands used to come with the 1/2" arbor inserts included especially diamond arbored blades that could be used on worm drive saws. Back in the 60s and 70s when the new manufacturers began producing circs many or most were 1/2" arbored drives. When the 5/8" drives came out the blades were cut for 5/8" with the adapter installed to maximize usage.

I hope you solve your issue without spending lots of money.


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## woodnthings (Jan 24, 2009)

*Vibration/wobble*

You should determine if the wobble is caused by a bent arbor or an out of 90 degree angle in the disc. The bent arbor is a real problem, probably not a home fix solution,
The hole in the disc can be made 90 degrees to the face of the disc, either by hand, drill press or machine shop. If it's a 5/8ths hole, get a snug fitting dowel that diameter and insert it the hole and check it for plumb/vertical, 90 degrees by eye. Hold a machinists square to it in various places around the dowel. Look for varying degrees of daylight between the dowel and square.

You can wrap a dowel with sandpaper in a drill press or hand drill, or use a small dia. drum sander inserted in the bore. Once the bore is vertical and as round as possible, it can be sleeved with a section of aluminmum can or copper pipe whose inside diameter is the arbor size. Epoxy the sleeve in place and the disc all at the same time on the greased arbor to prevent adhering. The whole set up can be registered on the table to align it as close as possible by slowly rotating it against a reference block until there is a minmum of wobble. 
Any lack of concentricity can be remedied with a file held against the edge while the machine is slowly brought up to speed on and off.

If all that sounds like too much effort, a machine shop would probably bore out the center for less than an hour of shop time after which you would sleeve and epoxy it yourself or have them do it.
Personally I don't like to give up on any machine that has the potential to be restored or repaired. But that's just me.... 
I kept a 1960's Craftsman saw going for 45 years, and several sets of bearings and various motors. The 220V Baldor 2 HP would rip through anything. :thumbsup: bill


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## AlWood (Apr 18, 2010)

Guys, sorry for being slow with my reply.
Ghidrah: thanks for your wishes; I am still trying all possible venues. BTW, I liked your expression, "YOUR JUST BLOCKING" -- I guess I got the point, yet out of curiosity (my English is sort of shallow: the dusty streets of my youth were busily buzzing in far-away places...) -- what is precise meaning of that? -- "being stubborn"; "playing a fool", "pulling feet"; "being in denial": anything else?

woodnthings; most unfortunately, you might be right about possibility of a bent arbor. In the very beginning, I was quite sure that the arbor is fine, but after your comment I took a rough measurment (just by a caliper), and it looks like its center point at the end is off the real axis center by about 1/32". Need to do now more precise measurments, got to find the tools; then I can figure out what runoff it can produce (my current measurment of the runoff at the edge of the disc is 3/32"). If this is the cause, I am in real trouble; off-the-axis or bent arbor shaft nixes the entire machine, which is a shame; in general I like it... Will see. As of right now, I have to put the stuff on a back burner; my dayjob duties grab me by the scrap of my neck...

Thanks, guys.


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## AlWood (Apr 18, 2010)

*Problem solved! thanks, guys*

Ghidra and Bill (woodthing), and the rest of guys who replied to my cries about a sander -- thanks again. As I promised, here is my report on the progress: a new, spare disk just arrived, I've checked its flatness (more or less OK), put it on -- and great relief! -- my sander is running with only tiny vibrations, with almost a kitten sound. The price of a heavy 12" alum disk was $19, which is fair (plus $8.50 shipping, but this is OK). The only problem left was what kind of adhesive to use; and on that, special thanks to Bill (woodthings) -- on one of your pictures I saw a glue (next to your home-made sander) -- 3M Feathering disk adhesive, type II, specifically designed for multiple use with sanding discs, and ordered it ($10 for 5 ounces). Cheers,
Alex


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## woodnthings (Jan 24, 2009)

*Great news!*

Where did you locate a new disc? Nice price! Glad to have helped a little and you obviously did a little research to see the 3M adhesive on another thread. :thumbsup: bill


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## AlWood (Apr 18, 2010)

woodnthings said:


> Where did you locate a new disc? Nice price! Glad to have helped a little and you obviously did a little research to see the 3M adhesive on another thread. :thumbsup: bill


Ha, good question:yes:... In the same place where I bought the sander, HF. I found the part number on their layout, call them up, and ordered it (I knew from my past experience with them that they would sell spare part if you have its number...). Actually, I've ordered the whole bunch (disk, two bearings, arbor shaft) just in case (was suspicious that it was arbor shaft that gives me trouble; but the disk was obvious villain anyway). All of that for the price $54, including delivery, would you believe that?
They sent in the disk, and the rest are on a back-order; will be calling them and canceling that back-order if they would go with that...

As to that 3M-adhesive, I was looking for it for a while (didn't know the name), and found it thanks to your nice touch:thumbsup:. Alex


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