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| Thickness sander issues... http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=53541 |
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| Author: | oval soundhole [ Tue Sep 22, 2020 10:31 pm ] |
| Post subject: | Thickness sander issues... |
I've had a Supermax 16-32 for about a year now and learning to set it up correctly has been... difficult. I've finally reached a point where it works pretty well for thicknessing tops and backs/sides but sanding larger stock has been tricky. I've been attempting to thickness a neck blank (well two) down to 18.5mm (18 is my goal but wanted to use my jointer plane to make sure all surfaces are nice and flat) but after sanding I found the ends to be 18.5 but the center to be 17.5. This seems to be the opposite problem of snipe and I'm curious if anyone knows of any way to remedy this. BTW, I'm using 120 grit paper and only turning the handle 1/8 turns each pass |
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| Author: | Marcus [ Tue Sep 22, 2020 11:06 pm ] |
| Post subject: | Re: Thickness sander issues... |
Make sure your infeed and outfeed tables arent flexing the wood up in any way. Also, a similar thread came up awhile back and the results were a warped feed table. So try removing the feeding belt and checking the flatness of the platform underneath. |
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| Author: | Pegasusguitars [ Wed Sep 23, 2020 12:58 am ] |
| Post subject: | Re: Thickness sander issues... |
Sometimes multiple passes on the same setting will help with that. Using a sturdy backing board, which is a pain, can also be useful to reach a critical measurement. I've had a number of sanders with similar issues, but luckily my current one runs pretty close to true. Good luck!-Bob |
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| Author: | Colin North [ Wed Sep 23, 2020 1:25 am ] |
| Post subject: | Re: Thickness sander issues... |
oval soundhole wrote: I've had a Supermax 16-32 for about a year now and learning to set it up correctly has been... difficult. I've finally reached a point where it works pretty well for thicknessing tops and backs/sides but sanding larger stock has been tricky. I've been attempting to thickness a neck blank (well two) down to 18.5mm (18 is my goal but wanted to use my jointer plane to make sure all surfaces are nice and flat) but after sanding I found the ends to be 18.5 but the center to be 17.5. This seems to be the opposite problem of snipe and I'm curious if anyone knows of any way to remedy this. BTW, I'm using 120 grit paper and only turning the handle 1/8 turns each pass If the joint in the belt (if it has one) is thicker than the rest, the blank sits on the joint it will lift it resulting in a thinner area - but 1mm sounds a lot? |
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| Author: | bluescreek [ Wed Sep 23, 2020 5:39 am ] |
| Post subject: | Re: Thickness sander issues... |
ok Brian when you turn 1/4 turn how much is it taking off? 120 is too fine. I have used a number of these style machines . You want to dial in about .010 to take off at a time. With 120 that is not very coarse and you will over stress the machine. I found 60 grit is good on these drum sanders. I would take it to within .005 of what I wanted to allow sanding out bench rash . These machines are not finish sanders . A good tip is this what is getting warm , Wood ? Paper? or the Dust? You want the heat in the dust . Once you get to hot the belt glazes over and get worse. Learn the feed rate for the grit your using. In this case coarse is better. |
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| Author: | Greg Maxwell [ Wed Sep 23, 2020 8:34 am ] |
| Post subject: | Re: Thickness sander issues... |
I agree with John, 120 grit is too fine for stock removal. I use 60 or 80 grit for thicknessing, and 120 through 180 for cleaning up. A well-tuned machine can leave a very clean and accurate surface if you follow the right progression. My spruce tops come out within .003 across the top and with almost no sanding marks left. I used to have a lot of trouble of the kind the OP describes when I tried to adjust the accessory in-feed and out-feed tables level with the feed belt. Any irregularity would lift the work and cause uneven sanding thickness. I now use the tables for convenience only and have had no further issues. |
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| Author: | mountain whimsy [ Wed Sep 23, 2020 9:47 am ] |
| Post subject: | Re: Thickness sander issues... |
Marcus wrote: Make sure your infeed and outfeed tables arent flexing the wood up in any way. Also, a similar thread came up awhile back and the results were a warped feed table. So try removing the feeding belt and checking the flatness of the platform underneath. That was me. had the the problem from side to side - the edges were thinner than the middle. Turned out my table was warped down in the middle. But I agree with the other comments as well. Check your feed tables. Sounds like they may be holding the ends up resulting in a lower middle. This would not really be an issue when doing tops and sides that will flex easily. And I also use 60 to 80 for material removal. |
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| Author: | Jim Watts [ Wed Sep 23, 2020 11:49 am ] |
| Post subject: | Re: Thickness sander issues... |
The other thing can cause deviations in the thickness is the seam in the feed belt. I try to avoid that if possible. As Bob mentioned, several passes at the final thickness helps too. |
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