Thread: Putting my optical comparator to work.

Not bad Stu given its bee dickish size.

What is the paper that you should use on the comparator? I use tracing paper daily. I wonder if it might be similar stuff.

BT

Originally Posted by Stustoys

Well I ground up a tool for 8BA thread tonight. Perfect job for the comparator*.
I really need to dig out the proper tracing paper.
Needs a little more work but I think it will do the job well enough.

Stuart

*or a proper grinding jig but I dont have one of those yet.

Stuart
The screwcutting job looks to be a challenge.
You have done a nice job with the tool.
I just checked, & recalled making the same thread for a dial indicator point.
It was also an 8 BA it measures .087" outside dia.
Made it in brass, however cut the thread with a small die. All went well.
regards
Bruce

Hi Bob,
I really dont know what sort of paper "should" be used. I've only seen drafting paper used, the transparent paper used with the photo transfer, like a blue print but not a blue print. I dont recall its real name anymore, though a quick google came across this, not nearly as costly as I thought it would be. I can only guess that is is the same sort of thing.

Draftex Shopping Cart

I assume you would use something similar. How can two 36" rolls hide in my shed?

Hi Bruce,
This will also be in brass. A dia borrowed from Bob is the fallback plan

Thanks guys

Stuart

Nice Stuart

Those optical comparator devices must have been around for a long time . My 1940's GMH book shows one in use at their factory .

Mike

Hi Stuart,

Bear with my ignorance here, but where does the master profile come from?

Is that the same comparator that GQ used to have? And more to the point did you manage to source spare lamps?

Regards
Ray

Hi Ray,

"where does the master profile come from?"
Well I could have drawn the thread profile....... but I cheated and used the copy of thread profile I made when working out the thread angle of the part I am replacing. Though now I think about it a little more, two longer lines for the thread angle may have made lining things up a little easier.


"Is that the same comparator that GQ used to have?"
It is. I haven't looked for a spare bulb yet or the setup lens. I'm struggling to see why they are necessary.... though that would likely be more to do with my optical ignorance than anything else. Maybe it matters if you want an absolute measurement though I've checked it on 100**X with my 1mm scale came out at 100**mm*. So I'd say its measures over 1mm to well less than 0.01mm. Maybe its needed if you have the micrometer platter/table?

Stuart

*maybe that's another way to skin a cat?

**Its infact 50X not 100X

Instead of Mylar, try using greaseproof paper from the kitchen

Michael

Originally Posted by Stustoys

Hi Bob,
I really dont know what sort of paper "should" be used. I've only seen drafting paper used, the transparent paper used with the photo transfer, like a blue print but not a blue print. I dont recall its real name anymore, though a quick google came across this, not nearly as costly as I thought it would be. I can only guess that is is the same sort of thing.

Draftex Shopping Cart

I assume you would use something similar. How can two 36" rolls hide in my shed?

Hi Bruce,
This will also be in brass. A dia borrowed from Bob is the fallback plan

Thanks guys

Stuart

Stu, what happened? Your shopping cart is empty!

If Michael's suggestion doesn't work I can post over an A4 sheet of the stuff I use when I'm back at work on Monday along with the 8BA die if required. I dare say grease proof paper would be a far more economical option.

BT

Hi Michael,

That picture is of grease proof paper, its gets a litte "fibrey" at 100x. I am hoping the drafting paper will be better.. but I am yet to find it

Maybe this is what I have in the shed, a little more spendy than my first link.

Drafting Film; Drafting Film

Stuart

Another thought - could you use some clear plastic (like the covers for spiral bound books) and draw on it with something like a chinagraph pencil, overhead projector pens, white board pens or just fine textas (and use meths to clean). All you are doing is checking a form, so even a cardboard silhouette would do the job.

Michael

Hi Bob,
Sorry I missed your earlier post. Thanks for your offer but I've found the paper! Much better(sorry for the less the perfect pencil work).

Hi Michael
You could be onto something there, I'll keep it in mind(in fact I have the boss on it).

Hi Mike,
The transformer in this one was made in Sept 1968 so this ones been around awhile


Here is a picture of the other paper and my 1mm scale.(its only 50X I said 100X earlier)

Stuart

Well I pulled the QCGB off the lathe today to get the gear ratios.
As yet I've only worked out the ratios to the leadscrew, then just using the metric gearing found a pitch of 0.4286mm*, that should do.
One of these days I'll add the other change gears and have 6300 pitch and 6300 feeds lol
Now to put the lathe back together.

Stuart

*Assuming my maths is right I am yet to check it on the lathe

For those worried that a 1.4 micron pitch error wasnt close enough , I sorted out Vernons gear calc and now have a gear set that will have a 0.15 micron pitch error or 0.03578%

Thank Vernon, I had a few issues and have a few questions, I'll add a post to your thread later.

Stuart

p.s. a mistake in my gears fixed, I think the current setup has a pitch error of .005 microns.... thats Half a Ray!