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Suitable metal / enclosure for project

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Chris TickTock10/11/2019 22:22:28
591 forum posts
41 photos

Hi, I wish to enclose a motor with AC to DC controller within it and mount a switch either by fabricating a small box or buying an enclosure. I am minded to use metal. The motor will be attached to a 50mm diamond lap / sharpening wheel. The disk will be outside the box and a tilting / adjustable table / tool rest will be by the disk.

My questions being a novice to such work are:

1. If I get an aluminium enclosure are there issues with debris sticking to the aluminium. I say this because I think aluminium is anodised for several reasons one being to stop it being magnetised???

2. If I go the fabricating from scratch route what gauge and type of sheet metal is suitable baring in mind I have no bending tools. I do have a welder and rivet tool and a strong vice?

Chris

Chris TickTock10/11/2019 22:40:07
591 forum posts
41 photos

Hi, I have since my former understanding on Aluminium to stop magnetic debris sticking to it is not correct. Annodising improves the thickness and corrosion resistance but aluminium is not magnetic. However the basic theme of my questions are there in terms of making a small enclosure suitable to the project.

Chris

Emgee10/11/2019 23:37:33
1717 forum posts
231 photos

Hi Chris

I believe there will be an electric enclosure that will suit your needs, either in GRP or plastic material, either can be obtained in good IP ratings as long as you use a spindle seal where it exits the box.

Emgee

duncan webster11/11/2019 00:22:51
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2795 forum posts
41 photos

Do you need to think about motor cooling air? If it's metal make sure it is earthed

Pete Rimmer11/11/2019 00:29:35
780 forum posts
50 photos

If I can suggest - the motor on my 180mm diamond lapping machine is tiny, about 60mm cubed, and that uses disk far larger than you plan for your 50mm graver sharpener. It has a belt drive reduction for the large discs to get about 400rpm

Why not look into building a battery-powered machine perhaps using 18660 batteries and a geared DC motor with the disc mounted on a backing plate directly on the output shaft? All you'd need then is a small switch and charging port and mount it all into a plastic enclosure.

Chris TickTock11/11/2019 09:08:23
591 forum posts
41 photos
Posted by Pete Rimmer on 11/11/2019 00:29:35:

If I can suggest - the motor on my 180mm diamond lapping machine is tiny, about 60mm cubed, and that uses disk far larger than you plan for your 50mm graver sharpener. It has a belt drive reduction for the large discs to get about 400rpm

Why not look into building a battery-powered machine perhaps using 18660 batteries and a geared DC motor with the disc mounted on a backing plate directly on the output shaft? All you'd need then is a small switch and charging port and mount it all into a plastic enclosure.

Thanks Guys,

Have you any details of your machine Peter such as the motor details. The issue for me was both getting the speed and torque so went safe but not I hope silly at a 200w having read that some 120w grinders stalled at slightest attempt at real use. All down to motor..what is the spec or model of your machine Peter?

A second point introduced is that of air cooling. Firstly do air cooled motors normally have a fan attached as part of the motor or do they rely upon air movement?

Thirdly just so I can make a judgement what is the thickest guage sheet metal bendable using wood and a hammer 9no press)?

Chris

SillyOldDuffer11/11/2019 09:57:48
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Posted by Chris TickTock on 11/11/2019 09:08:23:
Posted by Pete Rimmer on 11/11/2019 00:29:35:...

...

The issue for me was both getting the speed and torque so went safe but not I hope silly at a 200w having read that some 120w grinders stalled at slightest attempt at real use. ...

A second point introduced is that of air cooling. Firstly do air cooled motors normally have a fan attached as part of the motor or do they rely upon air movement?

Thirdly just so I can make a judgement what is the thickest guage sheet metal bendable using wood and a hammer 9no press)?

Chris

1. 20W at 400rpm is on the weedy side, 2000W at 400rpm would be grossly over-powered. 200W at 400rpm has decent poke, should be fine.

2. Cooling depends on the motor. Some are fitted with a fan (impeller), and need a free airflow. Others use the mass of the motor itself to absorb heat, and may be fitted with fins to radiate it. Check the motor rating: many motors limit the amount of time they are allowed to be on and insist on cooling off periods. For example, my hobby grinder's motor is completely enclosed (no air vents) and is rated S3 - 50% for 40 minutes. In other words I can expect 20 minutes worth of hard grinding in any 40 minutes, after which the grinder should be switched off and allowed to cool down. If I overheat it, the insulation will fail. A professional grinder might be fitted with a motor of the same power, but with an 80% or even 100% duty rating - considerably more expensive but it won't overheat in a busy workshop. The 1.5kW motor on my hobby lathe is a fully enclosed 3-phase type with a separate fan running continuously. So far I haven't made it warm! For your purpose, check the motor by hand periodically. When the motor feels hot to touch, it's time to switch off and have a coffee.

3. Much depends on the metal. With sheet clamped between two bits of old angle iron I've managed soft Aluminium for radio chassis up to 3 or 4mm. Mild steel up to about 1.5mm. In both cases it's easier to work with thinner plates! Not all metal sheet is happy to bend: I have tough and springy Aluminium alloy and Stainless Steel plates that resist bending and are reluctant to stay in shape. Avoid bending awkward metals! Not done either myself, but in theory Copper should be easy, and Brass troublesome because it work hardens and might need to be annealed between stages. Car bodies are made from 'Dead-mild Steel', which is malleable. Not found anyone selling it locally, but it must be available to panel beaters.

Dave

JasonB11/11/2019 10:17:20
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If you are using electronic speed control to get the motor down to 400rpm then don't expect it to develope amy where near full power at those sort of speeds, you will only get full wattage at full revs. So that 200w motor may only be 20w at 1/10th its fastest speed.

Running your motor slowly will mean any mechanical fan is less effective

Length of the bend will affect what you can form as much as thickness, easy to bend 10mm wide strip of 1mm steel but needs a lot more effort to bend a 200mm length of the same thickness.

Douglas Johnston11/11/2019 10:21:14
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704 forum posts
34 photos

Just been watching this video and thought it contained a number of good ideas for fine grinding of carbide with a diamond lap. https://youtu.be/GOBtH4m2TYo

Doug

Chris TickTock11/11/2019 10:29:55
591 forum posts
41 photos
Posted by JasonB on 11/11/2019 10:17:20:

If you are using electronic speed control to get the motor down to 400rpm then don't expect it to develope amy where near full power at those sort of speeds, you will only get full wattage at full revs. So that 200w motor may only be 20w at 1/10th its fastest speed.

Running your motor slowly will mean any mechanical fan is less effective

Length of the bend will affect what you can form as much as thickness, easy to bend 10mm wide strip of 1mm steel but needs a lot more effort to bend a 200mm length of the same thickness.

Apparently these motors are used to replace the motors on a Chinese lathe that being the case I am hopeful i will get enough torque at 400 rpm, but hey until I test it can't say for sure. the max speed is 2600 which is similar to my Sherline but is it any where as good......???

Chris

mark smith 2011/11/2019 11:00:17
671 forum posts
331 photos

Are people not over estimating the power needed to sharpen tools for clockmaking with a 2" diamond lap???

I bought a few of these dc peristaltic motors with controllers for £20 off ebay (they cost a fortune from cole palmer,the latest models are almost £1500 for one motor and controller) ,they are only 75 watt and suitable for a lot of smaller stuff. Only problem is overcomming the spiral splined 8mm shaft .

heres one i`ve used for a flexible drive.

p1340760.jpg

 

Edited By mark smith 20 on 11/11/2019 11:01:54

Ian P11/11/2019 12:24:40
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2420 forum posts
101 photos

This might sound like silly question but on a forum such as this the level of knowledge and skill of the members varies over a very wide range. One of the many benefits of even just reading the various posts is how much information gets picked up that then becomes part of one's knowledge. Like most things on the internet there is also a lot of misinformation and it is one tiny bit of this that prompted me to write this.

Why are the grinding wheels that ChrisTT is going to use now being called 'Laps'?

Ian P

Michael Gilligan11/11/2019 12:35:43
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16373 forum posts
714 photos
Posted by Ian P on 11/11/2019 12:24:40:

[…]

Why are the grinding wheels that ChrisTT is going to use now being called 'Laps'?

.

One man’s grinding is another man’s lapping

It’s worth looking at this: **LINK**

https://www.eternaltools.com/small-diamond-grinding-wheels

... and especially; noting the grit sizes, and watching the video.

MichaelG.

Ian P11/11/2019 13:30:19
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2420 forum posts
101 photos

Was that the link you meant to send Michael?

The product description and the video is all about grinding. Lapping as far as I know is a different process. True both use abrasives but my original point was not to be a pedant but to avoid misleading forum readers.

Ian P

JasonB11/11/2019 13:38:55
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Once you get down to the 2000g one that is getting into lapping but not as fine a stropping.

Howard Lewis11/11/2019 14:26:48
3608 forum posts
2 photos

Removing metal with a carborundum wheel would be Grinding in my book.

Using a diamond wheel for the final polish, to remove very small amounts of metal would be Lapping to me.

Howard

Ian P11/11/2019 14:34:40
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2420 forum posts
101 photos
Posted by Howard Lewis on 11/11/2019 14:26:48:

Removing metal with a carborundum wheel would be Grinding in my book.

Using a diamond wheel for the final polish, to remove very small amounts of metal would be Lapping to me.

Howard

Removing metal with a (driven) diamond wheel would be grinding in my book too, however fine the grade.

Ian P

Michael Gilligan11/11/2019 14:34:53
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16373 forum posts
714 photos
Posted by Ian P on 11/11/2019 13:30:19:

Was that the link you meant to send Michael?

The product description and the video is all about grinding. […]

.

Yes ... hence my opening remark

Perhaps I should have written: “A rose is but a rose by any other name”

For comparison, note that EZE-LAP diamond sharpening devices are commonly called hones.

The product page is specifically about what Chris is proposing to use.

MichaelG.

.

Edit: Thinking a little further about this ... It is difficult to distinguish a dividing-line between a ‘charged’ lapping plate and a CBN ‘grinding’ wheel. ... ferinstance :

https://www.axminster.co.uk/woodcut-tru-grind-cbn-grinding-wheels-ax933820

Edited By Michael Gilligan on 11/11/2019 14:44:56

Ian P11/11/2019 15:07:18
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2420 forum posts
101 photos

Grinding and lapping are both material removal processes but they are distinctly different techniques as far as I know.

Eze-Lap is just the name the manufacturer chose for the product, I've seen them referred to a diamond 'files' too.

Ian P

Howard Lewis11/11/2019 15:27:48
3608 forum posts
2 photos

How big does the enclosure need to be?

It is possible that there may be someone near you, with the facilities / skill to bend / roll sheet metal to the shape that you require.

Where are you located?

If you are worried about ingress of debris, the "front end" could be at least partially sealed with sheet rubber.

Your problem is going to be admitting cooling air for the motor without giving easy access for abrasive debris.

Maybe plenty of fins (Kept clean ) on a close fitting enclosure would do the jobs of both protecting and cooling?

Howard.

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