Mirror polishing machine

[JRM]

Hi All,

 After collecting and purchasing most of the materials needed, I have started construction of my polishing/grinding machine.

The size will be 40 x 24 x 30 with the top of the 24" turntable at 34" or so easily accepting my 20"  glass.

The frame is made of 2 x 6 and 2 x 4 with 3/4 ply on both sides.

Due to the fact that I can not get bigger pulleys I am running a three shaft configuration

the parts I have are as follows...

1725 rpm 1/3 hp motor

2 - 10" pulleys, one 3/4 the other is a 1" bore

1 - 8" 3/4 bore pulley

1 - 6" 3/4 bore pulley

1 - 3" 1/2 bore pulley, currently on the motor

3 - 2" 3/4 bore pulleys

1 - 1-1/2" 1/2 bore pulley

1 -  4 step pulley from 2 - 4-1/2"

2 - 3/4" by 16" round bar

1 - 3/4" by 24" round bar

1 - 1" by 24" round bar

6 - 3/4" pillow blocks

2 - 1" pillow blocks

1 - 1" collar

1 - 1" washer plus nuts bolts and washers to attach motor and pillow blocks.

a electrical box and light switch for power on/off 

I figure my lowest configuration will slow turntable to less then 5 rpm, no need for a dimmer

The 24" turntable will be cut from the 36" eight sided table top I already have, should be fun as it was made

from three pieces of 3/4 plywood glued and screwed together.

will also have to make a drip tray out of plywood.

this machine will just be a turntable for now but set to easily receive the fixed post configuration  when

need be.

will take pics during construction and post them to let you see how things progress

here shows the motor mounted in place and slots cut to receive the pillow blocks.

and

Thanks

Rick M

[RAC]

Sounds good but what about finding a motor with a reduction gearbox. You will find figuring sooooooo much more easy with it turning.

[Ajohn]

Used 3 phase motors with a gearbox turn up pretty cheaply on ebay at times as do 3 phase converters that provide variable speed.  Often these provide a right angle drive as well which means that the motor can be mounted on the base rather than the side with the spindle vertical. 

With a decent motor power it should be possible to safely get a 2 : 1 speed range by driving the motor from 40 to 80Hz. Running it more slowly for long periods might burn the motor out due to over heating so a couple of pulleys might be  good idea as well. Depends on the gearing of the motor. Most that crop  up will be too fast. I have wondered about removing the motor fan and adding a separate fan that always runs at the same speed - on your own head but it should help.

It has been said that gears are a bad idea in this sort of equipment as they may cause patterns to appear on the glass. TBD but I reckon it is worth a go especially when pushing by hand. Pulleys could too unless they are running precisely concentric.

John

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[mapstar]

Nice to see you are still battling away Rick.  An interesting project and one I will be looking into myself in the future for another bash at the mirror making.

Looks a sturdy table and the wood will dampen vibrations down. I've seen various wood built polishing machines on the net so they are wide spread.

The motor may be a little under powered you'll just have to see how it goes. Double pulleys are also a good idea to prevent slip too.

A 3 phase motor/gearbox/inverter combination would be a luxury and through the pulleys would give a wide range of speed control.

Anyway less of the waffle looking forward to seeing it come together.

P.s. Hope the wrist is feeling better.

[JRM]

Hi guys,

 Nice as they sound, a three phase motor and such is out of my budget at this time so pulleys and shafts it is...

I have been working on  the build , have three shafts and 6 pulleys installed and the 1" shaft situated in place with

one of the pillow blocks secured, just have to anchor the other and true them up.

I attempted to cut my turn table from the table top I was using before to no avail,cut off enough screws and ruined

the carbide blade, oh well, live and learn. will get a piece of plywood tomorrow and make the turntable from it.

tried it out today to see how things were and the last pulley turns at 17 rpms so when table is hooked up it should turn

less then 3 rpm, I did a slip test by grabing on to 17 rpm shaft, there is no slip what so ever.

I attempted to upload photos but keep runnig into errors, might be to do with the update to site, will try again later.

Thanks

Rick M

[Ajohn]

I had been collecting bits to build one for a long time. Cheap pulleys seem to be  a rarity in the uk especially as the size goes up so looking at the costs of those shaft's, bearings and belts the used 3 phase motor with gearbox worked out cheaper than anything I could buy especially new. A used inverter probably messes that up a bit but not by much. I happen to have a spare one so that aspect didn't matter much to me.

 Can't say that I am entirely happy about using an inverter. The motors make too much noise when driven with one. Having one with random switching helps but it's still a pain.

Look forwards to seeing some photo's of the build. I'm sure they will help others who want to do the same.

John

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[Astrobits]

When I made my grinding/polishing M/c ( not too far away from Rick's design ) I got my larger pulleys from washing machine repairers.  They might need some form of bushing if the central hole is bigger than the shaft but the principle that the strokes should be a bit irregular means that a bit of slop is quite acceptable.

Nigel

 

[JamesF]

This is something I want to do one day so I shall follow your progress with interest.

Useful hint from Nigel about washing machine parts.  My father-in-law used to repair commercial washing machines for a living and I'm sure we have a tub sitting around somewhere with a very large pulley on the back.  Could easily be 18" diameter.  I shall make sure that doesn't disappear anywhere so I can use it when the time comes if need be.

James

[Physopto]

What is wrong with a 3 phase motor with a large capacitor fitted between two of the phases. You lose some power but it works fine. Cheap to do as well.

All you need to do is calculate the required capacitor value for the size of  motor!

 

Derek

[Astrobits]

For the drive to the turntable I made my turntable from two pieces of ply. I cut both to the required diameter ( about 2'/600mm dia ) with an angled edge. These two bits were then bonded together so that there was a belt-sized V groove around the circumference. I then turned a V-belt profile into one end of a 1"/25mm shaft. This gave me a nice slow rotation of the table.

The actual work surface went on top and overhung the drive arrangement to keep it clean.

Nigel

 

[JRM]

Damian,

The wrist is better thanks, the build is coming along nicely, would have been best to draw out the plans first and go from there, I put something together then

have to move it  because its not in a good location, trial and error or live and learn I guess.

Nigel,

I tried to find some pulleys through that very route but no one had any, they are not used like the older machines, that is why I went to the three shaft configuration.

but thanks, I was planning to make a 16" wood drive with two pieces of ply also but no longer need to as the three axle configuration has enough pulleys to slow the

speed so a 10- 1/2 snowblower pulley I found will go under the turn table.

James,

  Store that thing away for the future project for sure, they are scarce and hard to find these days.

Rick M

[JRM]

Okay,

I installed the final pulley shaft and pulleys, cut the turntable a tad bigger then 24" in diameter,two pieces of 3/4 ply good one side, glued and

screwed them together, cut to 16" square pieces with 1-3/8 center hole bored through for brass bushing and secured them with screws to the

turntable, welded a locking collar to my 10" pulley and secured it to the bottom of the turntable as well,installed the 1" shaft with fixed pillow

blocks,hooked up the turntable and gave it a try, it rotates at 3 rpm ever 62 seconds, awesome.

I still need to tweek the turntable axle as the table has a slight wobble of 1/4" and need to sand edges of turntable smooth as it was cut with a skill

saw but thing are progressing nicely.

A lot of tweeking to get everything lined up, I still need to cut 7" off the table as it currently stands at 37" which is to high but I will fix that issue

soon enough, just glad to finally see the table turning and everything is working as it should be, nice feeling.

I tried again to upload photos but as of yet unable to do so, hope they get things corrected soon, will upload some as soon as the site

lets me.

Thanks

Rick M

the

[mapstar]

Things seem to be progressing nicely Rick.

 That's a very slow rpm and you should be able to work well with that.

I've uploaded a couple of photos so not sure why you can't do it? Saying that I've not tried it from the mobile so here goes.

Hope you get the pic of one of John's polishing machines used in the final stages of my mirror.

 

[JRM]

I guess it was my desktop that was causing the error, the laptop which I used for all the other photos works fine so here are some photos of the

pulley hook up..

 

 

 

[mapstar]

Hi Rick

Glad you managed to get some photos on and it's moving on quickly. These things take some figuring out with the available materials.

keep up the good work we're looking forward to seeing the progress 

[Astrobits]

When I made my m/c I decided not to rely on the central shaft to support the total weight of table and mirror on it's own. I therefore had a number of small plastic wheels under the table to provide extra support and to prevent any wobble.

Nigel

[JRM]

Hi Nigel,

 I was plannig on a collar with washer to support the weight as I don't think the pillow blocks would

stand all that weight but they might, just not going to chance it.

I am liking the wheels as a more reliable method, will pick some up tomorrow.

Thanks

Rick M

[JRM]

Okay, more pics of progress

tabletop with wheels, I tried four at first but three works better.the slot cut out by the small shaft is to allow for losing shaft to fit belt to 10-1/4 pulley

on bottom of turntable

turntable on the wheels

and the turntable installed

will hookup the electrical tonight so I can power on and off with the switch, and put a coat of primer on the turntable to prep for

the many coats of paint.

Rick M

 

 

 

[mapstar]

Excellent work Rick. 

You could use fibre glass resin to seal it with. I used it on my wooden laps. A couple of coats and it was water tight. Was a little sticky for the first couple of days.

The three support wheels look like they will work a treat.

What are you going to use under the mirror ontop of the table? I used tho anti fatigue type mat which allowed the mirror to be turned randomly every so often.

[JRM]

Thanks Damian,

 I have a 24 by 24 mat that I will cit into a circle for on top the turntable, much the same as what I used under the glass before but stiffer.

my tabletop ended up at 24-1/4", not a perfect trim job but close enough.

Rick M

p.s. did not have time to paint or stain, will do so tomorrow for sure.

 

 

 

[JRM]

Hi All,

 Over the last few days I have done two coats of stain on the turntable and three coats of clear varnish on both

the table top and the turntable, still waiting for the last coat to dry (put it on good and thick) but should be a go

for tomorrow to cut the mat and spend some time getting the mirror centered perfectly.

I willl be holding the glass in place with four blocks so two of them will be painted and permanently set to the

tabletop until the 20" is done, that way I can easily get the glass back to the proper spot using those two as the guides.

hope to be pushing glass by Wednesday after some Coulder mask testing first, will keep you posted.

 

Thanks

Rick M

[JRM]

HI All.

it is done..... for now.

 

I went with three blocks to hold glass in place, the two you see will not be removed till mirror is done, this way I only have to remove one to take it off

the turntable for testing. I will not be closing the front in as I will be changing out the frame for a metal one in the future, I did not bother with cutting

seven inches off the table but instead will build a 7 inch deck for in front of the stand to make up for the high table.

I will pick up a cover for the switch tomorrow  and also install plastic on the wall behind the stand.

It runs nice and smooth but Wednesday will tell the tale when I try figuring,will let you know how that turns out.

one good thing is I know have a dedicated  place for my mirror test stand, the table saw stand my previous table was set one, will attach

a piece of plywood to the top of it and my test stand can reside there right next to the machine.

 

The plan to make it into a fixed post is still on if I got to metal or not, all I need to do is run two pieces up the front and back then from

front to back on top with track to slide cross piece to proper position and skirt with plywood for strength.

I do not have a drip try install, really don't think it is needed for the slow speed figuring but will make one if need be, there is plenty of

room for it under the turntable.

hope you all liked my having this discussion on here, maybe it will inspire others to give it a go, I am sure there will be some bugs to

work out in the next little bit but that's okay, they are expected, nothing ever comes out perfect on the first go round and I will

keep you posted as always.

Thanks

Rick M

 

[mapstar]

That's a nice Job Rick and fingers crossed it will work as you intend it to. Eventually I will attempt one myself as my mirror making experience has left me wondering still and I do not like to be beaten.

Looking forward to your progress with it and your mirror looks mighty fine too a top the table. Always nice to see the polished glass without the coating.

Thanks for sharing your progress as it brings together good ideas from lots of people who have experience in the field.

Keep up the good work

[RAC]

Awesome looking good.

[Astrobits]

Don't forget that you will need to rotate the mirror on the mat fairly frequently to prevent astigmatism creeping in.

I used three blocks with one of them well away from the mirror and a loose wedge to lock the mirror gently. That prevented me from having to unscrew  and screw blocks, wood screw holes will soon become loose.

Nigel