Disc sander attachment?

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Ive been looking into buying a disc sander and have come across Brodbecks Disc sander attachment. Seems like a convenient way so I can use the VFD and reversible feature of my grinder. Does anyone have any experience with them, and is there any inherit downside to not having a dedicated machine (besides work-rest) that i'm not thinking about?

Thank in advance
 

Stacy E. Apelt - Bladesmith

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Many folks have made a tool arm with a bearing and 2" wheel plus a disc or buffer. The 2" wheel is run by the sanding belt. This turns the disc/buff.
It works, but the position and angle of the disc isn't the best or safest for doing knife work.

A dedicated disc sander can be made very simple or very elaborate. For the simple one, get a 3/4HP 3-phase motor and a disc for the shaft. Make a simple mount from 1/4" to 1/2" plate (aluminum or steel). Screw/bolt the plate to the bench. Bot the motor on the plate and attach the disc. Run the motor with the VFD on your grinder and a three-phase three position switch (TPDT, ON-OFF-ON). Make or buy a dust funnel for the dust collector to sit behind the disc to catch all the grit and sparks.

HVAC fittings and adapters make great dust collectors for the grinder and other tools. Here is a site with images and names of these parts. You can find na=many of tese at Home Depot as well as a HVAC supplier.
 
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I made an adapted disk sander for my 2X72 which worked just fine. I finally got around to building a disk grinder and it's so much better than the 2X72 adapter.
 
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I made an adapted disk sander for my 2X72 which worked just fine. I finally got around to building a disk grinder and it's so much better than the 2X72 adapter.
Seems like the the consensus is to just build one. Thanks for everyones input. Ken I was curious what benefits you saw with the disc grinder over the attachment on your 2x72?
 

Stacy E. Apelt - Bladesmith

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This is the Beaumont disk grinder. Nice, but pricey.
1652639740264.png

You can make something that works yourself from a $30 piece of aluminum plate, a $50 motor, and a $100VFD ... plus a disc.

You can make the identical unit for 1/2 the price using Rob's base plate and a disc, plus a motor/VFD package from Ebay

1652640152246.png

1652640371510.png
1652640435168.png
 
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This is the Beaumont disk grinder. Nice, but pricey.
View attachment 1819018

You can make something that works yourself from a $30 piece of aluminum plate, a $50 motor, and a $100VFD ... plus a disc.

You can make the identical unit for 1/2 the price using Rob's base plate and a disc, plus a motor/VFD package from Ebay

View attachment 1819031

View attachment 1819033
This would be the route that I would take If i end up making it. Not sure how how practical or possible for crossing using my 2x72 motor and VFD since I roll my grinder outside to use just because of my shop not really being a shop lol. But I do wonder with buying a cheaper motor and homemade mount how much shake/vibrations does something like this have while running? Would I be able to get away with putting it on a smaller steel table to move around or would I need to bolt this to the floor or my workbench?
 
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This would be the route that I would take If i end up making it. Not sure how how practical or possible for crossing using my 2x72 motor and VFD since I roll my grinder outside to use just because of my shop not really being a shop lol. But I do wonder with buying a cheaper motor and homemade mount how much shake/vibrations does something like this have while running? Would I be able to get away with putting it on a smaller steel table to move around or would I need to bolt this to the floor or my workbench?
 

Stacy E. Apelt - Bladesmith

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They spin freely and smoothly unless you have a bent shaft or disc. Mounting it on a steel table would be fine. That way you could use the VFD on the grinder to run it.
Tip:
If you are going to plug different tools into the VFD, put a 3-phase socket on the power out cord of the VFD. Put a matching plug on all the motors you plan on running off the VFD. To switch tools, you just turn off the VFD, switch cords, and turn it back on. Use NEMA 12-20 or NEMA L12-20 (locking).
A three-position switch is the simplest setup for two motors mounted to bench tools side-by-side.
 
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This would be the route that I would take If i end up making it. Not sure how how practical or possible for crossing using my 2x72 motor and VFD since I roll my grinder outside to use just because of my shop not really being a shop lol. But I do wonder with buying a cheaper motor and homemade mount how much shake/vibrations does something like this have while running? Would I be able to get away with putting it on a smaller steel table to move around or would I need to bolt this to the floor or my workbench?
I have a rolling metal table for my grinder, and I just so happen to also have the Brodbeck attachment you asked about! As far as the table goes, no worries at all about vibration. As far as the disc grinder specifically, I will say that it is very high quality and I like mine a lot, however, I think if I were to make that decision again, I would make a standalone one like the others mentioned. My Brodbeck attachment works great, but I would get much more use out of a disc grinder if it were separate and all I had to do to use it was turn it on, especially for how pricey the attachment is. Having to swap out attachments is annoying. Just make sure that you have a VFD on whatever disc sander you end up choosing. It's the most important feature IMO.
 
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Seems like the the consensus is to just build one. Thanks for everyones input. Ken I was curious what benefits you saw with the disc grinder over the attachment on your 2x72?
Jake, one of the really big advantages of the disc grinder vs attachment is the ability to easily add a good work rest. Also the hassle of having to setup the attachment rather than the convenience of it being ready to go. I've also added a footswitch to the disc grinder to allow placing blade on disc before starting rotation for some operations.

Just a though, wouldn't a servo motor work for a disc grinder? I don't see why it wouldn't, it operates from around 100 to 4,000 RPM in 100 rpm increments. A $100 will get a 3/4 hp motor and speed controller that is dustproof. I've got 2 of these https://www.ebay.com/itm/312767608801 I'm using. One on a desktop drill press, and another on the Chinese ShoePatcher sewing machine.

Here's a 1 hp unit: https://www.ebay.com/itm/124013148713?3907124
 
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Stacy E. Apelt - Bladesmith

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I have thought of those for other applications, but never tried it. My suspicion is the HP rating isn't true. 110V at 3A is 330W ... not 550W as stated. My other concern is how much torque they deliver.
They don't give the current draw for the 1HP unit, but I think it would be a better choice for the small price increase. I may get one and convert an old small drill press as an experiment.
The biggest issue is how to use the speed control lever. They are normally operated by a knee lever or a link rod to a mechanical foot pedal.
My Con-sew has an old 3/4HP non-electronic controlled motor made of steel. I think it would last longer in a shop than the plastic and aluminum of these light motors.

TIP:
If you connect a throttle control cable to a foot pedal it would work pretty well for a speed control and ON/OFF.
 
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That's the beauty of a servo motor, they have the same torque at 200 rpm as at full speed - well, close to the same anyway. I've thought about ordering another for my 10X22 lathe for variable speed. Currently I'm running a 1hp 3ph motor with VFD and at low speed thread cutting operations the torque is low, but actually plenty for thread cutting with light cuts. The 550 watt unit I have is mounted on a desktop drill press. The speed control has the return spring removed and stays where it's put so I move it by hand to the speed I wish as indicated on control unit.

I agree with you that 3 amp is NOT 550 watts, but I've not noticed any lack of power on either of the servo motors. I had the 750 watt unit mounted (replaced a 2hp motor) on a floor standing drill press where I drilled large holes with no lack of power. I removed the servo motor since I didn't really use the variable speed on the big drill press and I wanted to install the motor to the sewing machine.

While the motor housing is made of aluminum it's a heavy duty housing and I can't imagine it ever giving any problems due to being aluminum rather than steel. It's sturdy. The control housing is plastic, but I would hope it's not going to be beat on with a hammer so should be fine. It's also sealed so you don't have to worry about dust as the NEMA 1 plastic housings on the Chinese VFD are. After over 10 yrs of use I've never had a Chinese VFD fail due to plastic housing being broken.
 
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That's the beauty of a servo motor, they have the same torque at 200 rpm as at full speed - well, close to the same anyway. I've thought about ordering another for my 10X22 lathe for variable speed. Currently I'm running a 1hp 3ph motor with VFD and at low speed thread cutting operations the torque is low, but actually plenty for thread cutting with light cuts. The 550 watt unit I have is mounted on a desktop drill press. The speed control has the return spring removed and stays where it's put so I move it by hand to the speed I wish as indicated on control unit.

I agree with you that 3 amp is NOT 550 watts, but I've not noticed any lack of power on either of the servo motors. I had the 750 watt unit mounted (replaced a 2hp motor) on a floor standing drill press where I drilled large holes with no lack of power. I removed the servo motor since I didn't really use the variable speed on the big drill press and I wanted to install the motor to the sewing machine.

While the motor housing is made of aluminum it's a heavy duty housing and I can't imagine it ever giving any problems due to being aluminum rather than steel. It's sturdy. The control housing is plastic, but I would hope it's not going to be beat on with a hammer so should be fine. It's also sealed so you don't have to worry about dust as the NEMA 1 plastic housings on the Chinese VFD are. After over 10 yrs of use I've never had a Chinese VFD fail due to plastic housing being broken.
Hey I’ve been looking around for motors and came across something in my area second hand. Seems like you know much more than I do(have no experience with motors or anything electrical for that matter) was curious on your opinion if it would work. My questions are can 230/460(3 phase) be converted to 110 through the VFD or does it have to be 110/220? Also if it will work to convert to 110 does this affect the HP if its below 2hp. the one i'm looking at is a 1/2 hp. I know 2hp motors get dropped to 1.5 when wired for 110 but have no idea how that works below that. I am looking at the two you suggested but this one is a baldor SuperE less than 10 min from me and less than $100. Any input/advice is greatly appreciated.


 

Hubert S.

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Hey I’ve been looking around for motors and came across something in my area second hand. Seems like you know much more than I do(have no experience with motors or anything electrical for that matter) was curious on your opinion if it would work. My questions are can 230/460(3 phase) be converted to 110 through the VFD or does it have to be 110/220? Also if it will work to convert to 110 does this affect the HP if its below 2hp. the one i'm looking at is a 1/2 hp. I know 2hp motors get dropped to 1.5 when wired for 110 but have no idea how that works below that. I am looking at the two you suggested but this one is a baldor SuperE less than 10 min from me and less than $100. Any input/advice is greatly appreciated.


A KBAC-24D/27D VFD can take 110V and run a 220V 3-phase motor. The KBAC-27D can only provide 1.5 HP when wired for 110V input, so if you use a 2 HP motor, you only get 1.5 HP. For motors with less horsepower, the drive can provide all the power needed when connected to a 110V input. For the 1/2 HP motor you would only need a KBAC-24D. As far as I am aware, the KB drives are the only ones that have a 110V input option.
 
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Hubert has covered it nicely. If you have 220 available you have more choices.
 
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Hubert S.

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There is now a 110V import VFD available on amazon for about $115. I guess we are not allowed to provide links, but if you google Wisoqu VFD it should come up. Brian House has a video about it where he sticks the VFD into an ammo box. Not sure if that is a great idea with no airflow.
 
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