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Rotary Table question

jcdammeyer

John
Premium Member
On a slightly different note - how do you delete your picture from your profile??

Because I can't show my face on the forum for a while.

In the spirit of Quinn, who always shows her screw ups: While double checking that I couldn't grab inside the hub on the outer drum, (opposite side from "A" side) I discovered that I COULD grab the inner hub with the smallest step on the jaws. Goes to show when you have an idea stuck in your head it might be a good idea to step away and come at it again fresh.

Of course this was after I took my vice off the milling machine table, and lifted the too large rotary table into place. Gotta build a little crane like Mr. Pete.

The mount is for a friends telescope. He found the plans online that call for the modification of a standard size brake disk. It's called a "Pier adaptor."

On the slightly humorous side, he told me the measurement is -0.75/-0.50, which is what someone has on the CAD sheet from Celestron.


Thanks for helping me look at this with fresh eyes. While I have the rotary table mounted, I think I'll give it a whirl with some scrap Al.
I'm going to venture a guess that it's something like this then?
 

Susquatch

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The mount is for a friends telescope. He found the plans online that call for the modification of a standard size brake disk. It's called a "Pier adaptor."

As far as I know, pier adapters are outdoor mounts. The pier is aligned and stays in place permanently. They are usually a large heavy concrete base with a steel adapter for the telescope to minimize vibration.

However, brake rotor composition is designed to be slightly porous for high friction and consequently it rusts very easily. I dunno about using it for a Pier mount....... Perhaps if it's painted.

Just the same, I'd love to see the plans.
 

PeterT

Ultra Member
Premium Member
Does surface A have to fit inside a mating surface ID? As others have said, end milling around the perimeter might not result in a finish you are happy with & be a bit finicky trying to hit a target dimension with control, depending on your equipment & experience. A turned finish would be better & more controlled. But looks like maybe you are working with what you have. Also I haven't turned an auto part like this, maybe others more familiar can chime in. If its unfinished as is, it might have some delightful casting crusty skin to get through.
 

Susquatch

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Also I haven't turned an auto part like this, maybe others more familiar can chime in. If its unfinished as is, it might have some delightful casting crusty skin to get through.

Brake rotors can be turned. In fact it used to be standard practice. Today, everyone just replaces them.

To be fair, that is usually on the flat ground surfaces of the plate, but you shouldn't have any trouble with the hub section either.
 

Darren

Ultra Member
Premium Member
Surface A in the picture in the first post is usually the thinnest part of the rotor. Cheaper rotors may not be that consistent either. Keep that in mind if taking off more than say 0.040 total DOC.
 

Susquatch

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I agree with @Darren - A is not usually very thick. If it turns out that A is too thin for your target dimension, perhaps you can find another Rotor that might be better for you. There are thousands of different size brake rotors out there.
 

jcdammeyer

John
Premium Member
I was just browsing youtube videos and found one by Tubal Cain done about 8 years ago. Seems he's had the same idea for centering the rotary table except he does it in two steps rather than with one longer tool like mine.

 

6.5 Fan

Ultra Member
Premium Member
Hmmm, i have 2 brake lathes sitting in the quonset. One, an old drum lathe, is being converted into a large case tumbler. Every good garage had these machines, now you buy new rotors, no fixing the old ones.
 

Tomc938

Ultra Member
Premium Member
I'm going to venture a guess that it's something like this then?
Yes, this is the idea. Apparently the telescope itself sits within a small "shed" so it will not be sitting out in the rain. I woudl assume a regular oiling will be part of the routine. My friend is a retired millwright, so stuff like this is right up his alley.
 

Susquatch

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I was just browsing youtube videos and found one by Tubal Cain done about 8 years ago. Seems he's had the same idea for centering the rotary table except he does it in two steps rather than with one longer tool like mine.

I am nothing if not consistent. Crap I hate YouTube. I am just too old to waste that much time. I bailed about a minute in.

I have the coaxial indicator he used in his next video. No, I didn't watch that one either. The subject was sufficient to know what he did. That's how I used to do such things on my drill press and mill/drill before I got the knee mill last year.

But I had no DRO back then, and I have not mounted my rotary table yet since I installed the DRO. So this short exchange is a good place to discuss a better way to do it with my new DRO. Today, I would probably use my digital ball edge finder and DRO divide by two function on an MT3 Stub of almost any kind in the center taper of my rotary table. The ball edge finder eliminates any concerns about the top taper or profile on the MT3 stub. I prefer this kind of approach over grabbing the stub in the mill spindle because I can put my rotary table where ever I want it, bolt it down perfectly in the table slots, and not worry about it moving when I do. Then instead of centering the rotary table on the spindle, I'll center the spindle/mill on the rotary table using the DRO.

A nice advantage of my DRO is that it remembers zero even through a power outage. I can shut it down overnight and pickup where I left off a week later.

I think I could even leave the rotary table setup on the mill table for a long extended period of time and do other jobs on the vise because the DRO has multiple saved zeros. I dunno about that one till I try it though.

Ya, the DRO is changing my life.

Like always, the required precision of the job dictates the precision of the setup. It's hard for me to imagine a rotary table job that requires more precision than an MT stub, edgefinder, and DRO divide by 2 function though. But I'd bet good money that one exists.
 

Susquatch

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Yes, this is the idea. Apparently the telescope itself sits within a small "shed" so it will not be sitting out in the rain. I woudl assume a regular oiling will be part of the routine. My friend is a retired millwright, so stuff like this is right up his alley.

@Tomc938 & @jcdammeyer

Very cool to have his own little observatory. A Farmer down the road from me had a small rotating dome. I never saw any sign that he used it so I had planned to stop by and ask if he was interested in selling it. But the heat from a house fire took the fiberglass dome with it and that was that.

What kind of shed does he have? Flip roof, rotating dome, rolling shed?

Cool to read in that article that the pier mount is the "standard Meade LX200" mount. That's what my big telescope is. It's a little 8 inch though. LOL!

I keep it setup in the barn. Easy to carry it in and out to the open yard right on the tripod.

Still have not seen any aliens..... LOL!
 

jcdammeyer

John
Premium Member
I am nothing if not consistent. Crap I hate YouTube. I am just too old to waste that much time. I bailed about a minute in.
I never had the sound up and was watching TV with my wife while I dragged the pointer through the video to see what he was doing. I also have ad blocker so I am never bothered by that crap. I probably should have said that what he took a half hour to describe using two different pieces of metal I did in what: 3 photos and a bit of text?

In fact my alignment tool was done on my Gingery Lathe using the MT2 taper feature on my ELS and turned between centers. About the only thing that might be wrong with it is if it's dropped and ends up with a slight bend. I've never indicated it to see if it's exact although now that I have my fancy indicator connected to LinuxCNC I can ask it to find the center of a round piece and it will do that automatically for me.

John
 

Tomc938

Ultra Member
Premium Member
Surface A in the picture in the first post is usually the thinnest part of the rotor. Cheaper rotors may not be that consistent either. Keep that in mind if taking off more than say 0.040 total DOC.
My friend ran across a website that suggested this exact brand and part number for the modification.

If course if it does end up too thin, not my fault!

Picture below.

IMG_5716.JPG
 

Darren

Ultra Member
Premium Member
They must be using a rear brake rotor with a drum in hat park brake, which are fairly thick in that area, like the drawing. Shouldn't have any issues if that's the case..
 

jcdammeyer

John
Premium Member
Speaking of rotary tables etc. I was passing a link to one of my youtube videos to a friend and noticed a 12 year old one (very fuzzy video). I was drilling all the mounting holes and counter sinks etc. for the CNC router motor mounts.
In this case my ELS Z axis was connected to the small motor on the tiny rotary table. I changed the jog increment to issue the number of steps required to turn 90 degrees. So each tap of the button moved me to the next drill point. The quill was moved by human power.
 
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