How does someone gauge the power of a DC or AC motor?

[John HaineParticipant @johnhaine32865]

I can't understand why you don't just put it in the lathe. Normally that's frowned on because normal grinding wheels throw abrasive grit everywhere but used carefully diamond wheels shouldn't do that. Anyway you can cover the ways with paper to keep it off. Eternal actually say use them in the lathe.

[JasonBModerator @jasonb]

I suppose the problem with that is you can't easily touch up a tool part way through a job unless you take it out of the lathe and possibly chuck too if you are using that to hold an arbor.

[Chris TickTockParticipant @christicktock]

Posted by John Haine on 09/11/2019 17:23:14:

I can't understand why you don't just put it in the lathe. Normally that's frowned on because normal grinding wheels throw abrasive grit everywhere but used carefully diamond wheels shouldn't do that. Anyway you can cover the ways with paper to keep it off. Eternal actually say use them in the lathe.

John , you may be right but I need to look first at the alternatives.

Chris

[Chris TickTockParticipant @christicktock]

Hi Guys, I have finally gone for better or worse a 200w DC motor and speed controller / convertor. Reason being the motor is one used on a tread mill and has good reviews. Also the speed controller allows the speeds I wish for at around 400 rpm. This means I can directly attach the diamond wheels without complicating matters without additional gearing. The motors shaft is 10mm so the only question is whether to go with a 3 jaw chuck or ER16. I have looked into this and for the purpose of sharpening / grinding I would think a cheap 3 jaw chuck will do. As always time will reveal if my plans fail or otherwise. I am learning lots from this post including to match a chucks taper with the adapter. if anyone has thoughts on my best method of holding an 8mm arbor for my sharpening wheel to this 10mm motors shaft feel free to offer your opinion.

Chris

[Chris TickTockParticipant @christicktock]

Hi, I ended up not going for the kit including the ER11 collets for several reasons but mostly the idle speed was far too high.

I have decided and bought a treadmill DC motor with pulse width control this gives speed control with one really good bonus…..maximum torque at all speeds. Reason: max torque is when max current and pulse width is either on or off (max).

I am thinking of just using a 1.5 to 10mm drill chuck to mount the 50mm grinding wheels and other related small disks.

Chris

[JasonBModerator @jasonb]

By the time you have modified the motor shaft to take a chuck or made an adaptor for the chuck as  well as an arbor for the disc to be held in teh chuck you may as well eliminate one or two sources of run out and simply modify the motor shaft so you can fit the disc direct to that or make an adaptor/arbor to fit the shaft and hold the disc on the other end

Edited By JasonB on 11/11/2019 18:19:26

[PekkaNFParticipant @pekkanf]

Or you might get something out of this vid.

 

Edited By PekkaNF on 12/11/2019 11:16:13

Edited By JasonB on 12/11/2019 11:19:37

[Ian PParticipant @ianp]

Thats one of the better produced YouTube videos and I learnt two useful things from it, one that he describes it use as lapping as well as grinding, secondly, I want one!

The diamond disks that he uses are much cheaper than I thought they would be and two from different sellers are on their way to me now.

Ian P

[PekkaNFParticipant @pekkanf]

Build something like that 2017 to lap carbide scraper blades. I used 90W 2800 rpm furnace blower motor geared dow with round belt pulleys.

I used scraped aluminium profile for frame and build very simple spindle with two ball bearings that acsept 12 mm shaft. i glued one bearing (fixed bearing) and left another easy fit. All parts and materials from scrap box.

Work table is mild steel to allow fixing jigs there with magnets.

Different holes for different r (on scraper blade radius).

Plinth made of C-section mild steel is milled to proper angle (scraping blade needs small negative angle).

Slow speed works fine and even blade change is not too hard with knurled knob.

 

 

 

Edited By PekkaNF on 12/11/2019 17:31:09

Edited By PekkaNF on 12/11/2019 17:32:50

[Chris TickTockParticipant @christicktock]

Adapter now made not 100% happy with as blind hole face could be better but on whole acceptable and should do the job

Thanks for all help and posts which are appreciated.

chris

[Howard LewisParticipant @howardlewis46836]

Commercial Plummer Blocks are OK for shafts, but not for precision grinding. There will be chatter!

BEWARE!

One of our bearing suppliers made up a broach grinder using commercial plummer blocks. The chatter ground into the broach was small, circa 0.00001" and was reproduced in the bearings. It caused the white metal bearings to fail. The chatter marks acted as drains for the oil, despite being pressure fed.

Howard

[Ian PParticipant @ianp]

Whoa!

Is there some danger to life or limb that warrants an all capital beware warning?

I doubt it myself, and dont see the connection with where an imperfect surface (less than a quarter of a micron) causes loss of oil pressure. I think there was more wrong with the design of the 'broach grinder' than the plummer blocks.

Ian P

[Ian PParticipant @ianp]

Posted by Chris TickTock on 16/11/2019 12:40:45:

Adapter now made not 100% happy with as blind hole face could be better but on whole acceptable and should do the job

Thanks for all help and posts which are appreciated.

chris

I would not be in the slightest concerned with the state of the face at the bottom of a blind holes, its not like anyone will ever see it and its serves no functional purpose whatsoever. As long as the shaft enters far enough its done its job.

One observation I would make is to say that ideally the grubscrew should make contact with the shaft about half way along their engagement length. It helps to increase the chance that the axis of the two parts are parallel with each other.

Out of interest, how did you ensure the concentricity of the bore relative to the threaded shank?

Ian P

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