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Author Topic: choosing the right electromotor, please help.  (Read 2779 times)

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #60 on: March 27, 2019, 07:38:04 PM »
Hi Makky, impressive.  How does it perform 50m. Down the brass from the collett?.
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #61 on: March 27, 2019, 10:21:33 PM »
It's still pretty good I was spinning a dop and couldn't see any run  out by eye. The run out on the gauge may have even partially been the brass out of round slightly.  I'll measure at 50mm for you.

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #62 on: March 28, 2019, 09:14:33 AM »
I think it should be pretty good.  Jim Piezchulski (I think that's how you spell his bame) has a few you tube videos on machining, including one on centering the job that is worth a watch.

He also has one that shows you how to make a centering device for precision machining such as cutting mandrels.  It us essentially a collet that is machined in the chuck jaws.
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #63 on: March 28, 2019, 12:40:50 PM »
For my first mandrel, as I only have about 0.01mm run out on my lathe 3 jaw chuck so I'm just going drill a 1/4inch hole through some aluminum round bar and loctite it to a bit 1/4"  brass rod. Then hold the brass rod in a er11 collet holder held in the lathe and machine the mandrel to size. Should get it pretty good. But I have a heap of other stuff to do before I do that  ::) . Too many things to do. I have a heap of parts that have arrived, T8 feedscrew looks really nice considering how cheap they are. I have also collected quite a bit of 12mm alloy plate offcuts I intend to put to good use.


FlashGP

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Re: choosing the right electromotor, please help.
« Reply #64 on: March 28, 2019, 08:26:41 PM »
Hi Makky,

From what I hear 0.01mm runout on a 3 jaw chuck is exceptionally good, is it new?

Wouldn't it be better to drill a hole the same diameter as the brass rod in a piece of stock mounted in the chuck, then mark the position of each jaw numbering them, then cut 3 cuts in the stock to form a collett for the chuck.  This will allow you to mount your cutting mandrels directly in your 3 jaw chuck without the need for packing to prevent the chuck jaws marking the job.

regards
Gordon.

This would eliminate any error introduced by the ER11 collett chuck when machining the cuters. 
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #65 on: March 28, 2019, 11:00:51 PM »
Yes the lathe is new and I was pleasantly surprised the 3 jaw is as good as it is, I haven't used my independent 4 jaw chuck yet.  You can see it in the youtube clip. I have fitted steppers to it and can use manually or cnc. I have a quick change tool post I have to fit to it which is on the to do list aswell.

One cut might even do, that is how I was machining dops.  But I was thinking I might just try drilling the stock, turn to size, loctite in the brass then part off the mandrel.

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #66 on: March 29, 2019, 08:36:33 AM »
Sounds good.
A lathe is on my wish list  as is the space to have one.  Have been turning cutting mandrels on a friends lathe, he is a a retired machinist/engineer.

You may need to approach the cutting face size in small increments to reduce sub surface damage, and produce a nice finish on the job and get all of the concave cutters within +/- 0.01mm of each other.

Ian had 6mm stainless rod from a printer, which we used as a mandrel, then sleaved it with brass from a tap spindle, turned that to size then pressed a piece of copper pipe with locktite over the brass and machined to size.

Kept one brass full cutter size as an experiment, it works well.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #67 on: March 29, 2019, 08:56:56 AM »
What diameter are you using for your mandrels? I have 6mm stainless from printers aswell, that may be better to use as most of the brass rod I have is very slightly bent. Brass should be nice for a prepolish/polish.

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #68 on: March 30, 2019, 06:30:35 PM »
Hi Makky


I purchased a couple of 13mm Darkside mandrels from Aussie Sapphire, old stock.  They also had a 13mm BATT mandrel which I was going to use for cutting and prepolish, but it had a 3/8 inch shaft that was too big for the ER11 collet chuck.


If I was starting again I would use ER16 colletts so I could use the mandrels sold by Polymetric.


The 13mm Darkside mandrels are 12.31 and 12.34mm respectively.  So we made 12.31 mm mandrels as I should wear the 12.34mm Darkside to 12.31.


These worked a treat for the 2019 AFG comp concave cut.  I've posted a video of it on the Faceting groups on facebook.  I had trouble putting it in the gallery of this forum, and gave up.  I had a bit of chipping on the edge of the rolled girdle with this stone so finished it with a 100K polish so it sparkled and Mrs Flash has claimed it.


The stone is 11.7mm in diameter and I think using mandrels about the size of your stone works well.


I also have 8mm printer rod which fits snugly inside 3/8" copper tubing and will make mandrels about 9.5mm in diameter.  we just need to turn the end to fit in the collett down to 6 mm, glue on the tube and size the mandrels so I have a set of 3 matched mandrels.


By the way, Polymetric sells mandrels in 4 sizes starting at 13mm.


regards
Gordon


Anyway 
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #69 on: April 16, 2019, 08:40:16 PM »
How much horizontal adjustment have you on your machine Flash ? How much do you reckon you need?
CheersMB
 

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #70 on: April 17, 2019, 06:05:22 PM »
Hi Makky,

Anoit 2.5cm each side of the centre of the mast.  It lets me cut parrallel facets on big step cut stones.

However, I found that you need to have the splash pan wide enough to accommodate the movement.

Am also looking to add splash protectors to my oscillation bearings.  When I use water as a coolant, it splashes onto the rods the bearings run on.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #71 on: April 17, 2019, 08:07:25 PM »
Thanks Flash, I wouldn't worry about the oscillation bearings too much just keep a bit of light grease on your rails. I'm going to use plastic ones as they will run a lot smoother. My brother has them on his 3d printers and they are really nice.Easy to swap into the housings you have if you decided to.



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