SFM Meter Anyone

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wwbrown

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I am planning on building a knife grinder and I thought it might be nice to have a display that would show what the surface feet per minute is. With a continously variable speed VFD drive the meter would allow the operator to know what the SFM was instead of guess.

I am building a meter for my build that will use a non-contact sensor that would be non-optical so the dust would not cause failures. The sensor is a hall effect that would be triggered by a small ceramic magnet that was mounted in the drive wheel or any other wheel that would provide easier mounting. A 3mm diameter hole would need to be drilled about 2 mm deep to hold the magnet. The speed of the belt would be displayed on a simple LCD display.

Is their any interest in people for purchasing a SFM sensor for their grinder?

Maybe one of these sensing systems exist if so could you reply to this thread with a link to the sensing system.

Thanks for your time,
wade
 
This is build into the VFDs. If you dig into the setting you can have the display show HZ, rpm or a custom number. You calculate the feet per rpm and enter this number into the controller and bam the display shows SFM. So if you need to know the SFM it's becaus your using a VFD and if your using a pulley system then you know the set speeds of the puly steps.
 
There is more than one speed???:rolleyes: I use WFO or slower than a snail the only 2 speeds that matter...
 
Careful with the sales talk at your membership level. Personally, I don't see the need for an SFM meter.
 
wwbrown said:
I am planning on building a knife grinder and I thought it might be nice to have a display that would show what the surface feet per minute is. With a continously variable speed VFD drive the meter would allow the operator to know what the SFM was instead of guess.

I am building a meter for my build that will use a non-contact sensor that would be non-optical so the dust would not cause failures. The sensor is a hall effect that would be triggered by a small ceramic magnet that was mounted in the drive wheel or any other wheel that would provide easier mounting. A 3mm diameter hole would need to be drilled about 2 mm deep to hold the magnet. The speed of the belt would be displayed on a simple LCD display.

Is their any interest in people for purchasing a SFM sensor for their grinder?

Maybe one of these sensing systems exist if so could you reply to this thread with a link to the sensing system.

Thanks for your time,
wade
Click to expand...

Yeah no sale talk if your not a paid member
 
I work on boats, and I am always amazed at how many customers want "Tilt trim" gauges.

No disrespect sir but as others have stated... either it is working or it is not.

Numbers make for poor judgment. They do NOT make up for it. (in some instances)
 
I can see how the standardized numbers can be useful for returning to a known good setting, or for comparing different machines. Personally though, I'd rather have a scaled speed control pot for repeatable settings and use a calculator for working out SFM from the VFD speed readout on the rare occasions it is needed.

As said above, most VFDs can display SFM directly if that's what you want them to do.

A cheap bicycle speedometer can be used to give a surface speed readout. These normally pick up on a magnetic sensor attached to a wheel spoke, but will pick up on a Neodymium magnet glued into a hole drilled in a drive wheel. It's then just a case of working out the wheel diameter that gives an appropriate speed indication.

These have been used to give a low-cost speed readout (usually in RPM) on hobby lathes and there are write-ups out there. A search for "Tachometer-made-from-a-bicycle-speedometer" is a good place to start.

I used a cheap "Halfords" (a UK motor & cycle accessories store) branded one on a SouthBend lathe a few years ago (if you are not in a hurry, similar units are available on ebay for around 5 bucks delivered from China). I'd be less keen on using a magnetic pickup on a grinder though: It will definitely collect grinding dust.
 
Yep, as said most VFD's will provide the SFPM indication - I like having the speed displayed, but that's just me. Makes it easy to return to a set speed that works good with the belt being used. Also, remember with a 4" drive wheel, the SFPM is just slightly above the RPM of drive wheel.
 
Wade, since your only presence on BF is this thread, I have to consider it a sales pitch. I will lock the thread for that reason. Feel free to post threads about knifemaking and any knife related topics, or show photos of your grinder and readout setup. Just no sales or sales related talk without a Knifemaker membership.

You are sort of re-inventing the wheel. Most VFD's have a tach out reading. You can display it in Hz, RPM, or in some cases, program it to read SFM. It can also be sent to a conversion program and read out as any function you put in the parameters for. Most folks don't really care what the exact SFM is. They just need to know slow, medium, fast. They adjust the speed as needed to get the grinding results desired.

Additionally, most of us are pretty particular about the drive wheel being balanced. Your drill and fill would probably barely make a difference, but should be considered, as any vibration gets magnified at 3500RPM.
 
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