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Author Topic: Facetron wandering dial indicator issue  (Read 4641 times)

RoughCreations

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Facetron wandering dial indicator issue
« on: April 21, 2021, 11:13:40 AM »
I have an annoying problem associated with the dial indicator on my ~3 year old Facetron. The problem has always been there since new, and I have learned to work around it mostly. I believe it is exactly the same problem as raised in the following link on another forum by user Caedmon:
https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=8&t=13174

The transcript:
Quote
I'm getting frustrated trying to cut to a consistent depth with my Facetron. It's got a dial indicator for the depth, which seems like an ok idea except it turns out it's not very repeatable. I thought I should be able to cut until the needle goes to 0 then repeat at other indexes. But after using it a bit I realized that there's a quicker way to get the needle to 0 than cutting. All I have to do is lift the dop arm up and put it back down and the needle will often move up to 4 divisions closer to 0. The first time I noticed this the needle went past 0 and I had overcut a facet. At this point I only trust the needle for coarse grinding and after that I'm constantly checking how far I've cut visually.

So for any Facetron experts out there, is this normal for this machine or have I got a defective indicator or some other problem? If it's normal, what other way can I go about getting consistent cuts without constantly looking?

The problem is most noticeable cutting at 90 degrees or thereabouts, but happens at all angles. If you lift the quill to inspect the stone and then simply lower it back to the same place on the lap to continue cutting, the dial reading is often a few graduations closer to zero than before. The dial needle will often gradually migrate back closer to where it should be, following several seconds of cutting activity vibrations. The end effect is that it is hard to get even pavilion tiers using the dial. Sounds like user Dor in the gemology online discussion had the same problem, too. It isn't related to the way I am using the machine, it is a real, physical hardware problem somewhere, and not necessarily the dial indicator itself imo.
I did try and replace the standard Chinese dial indicator that comes with the Facetron with a better quality dial a while back to see if that would help, but unfortunately I didn't order the correct model and had to return it, and put the problem in the too-hard basket since then.

So, has anyone else noticed this issue with their newish Facetrons and can help?
Regards,
RC
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RoughCreations

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Re: Facetron wandering dial indicator issue
« Reply #3 on: April 21, 2021, 12:39:37 PM »
Starting this thread has jogged my memory - I also remembered there is a slight skewness to the dial indicator mount block on my machine (from new) that shouldn't be there I think, see images below. I bet that is related to my problem... Can those with a Facetron check their machine and see if it is only mine that is dodgy in this way?







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Bucket

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Re: Facetron wandering dial indicator issue
« Reply #4 on: April 21, 2021, 12:45:57 PM »
RoughCreations, I've got a Facetron and have found that when cutting at 90 degrees, the dial indicator is next to useless so like you, I only use it for rough grinding. There should also be a 'hard stop' as well which can adjust to stop over cutting. Can't remember how to adjust it offhand and I'm still away from my machine so can't double check it for you. If you still have the manual, have a look, it should tell you how to do it. The mechanism might also need a clean, again it should be in the manual. By the way, nice plug Makky!
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RoughCreations

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Re: Facetron wandering dial indicator issue
« Reply #5 on: April 21, 2021, 04:12:03 PM »
RoughCreations, I've got a Facetron and have found that when cutting at 90 degrees, the dial indicator is next to useless so like you, I only use it for rough grinding. There should also be a 'hard stop' as well which can adjust to stop over cutting. Can't remember how to adjust it offhand and I'm still away from my machine so can't double check it for you. If you still have the manual, have a look, it should tell you how to do it. The mechanism might also need a clean, again it should be in the manual. By the way, nice plug Makky!

I have tried the Facetron hard-stop a number of times but have found I still cannot get an even tier of pavilion facets, and I think it (once again) could be due to my machine. My spidey senses are tingling and I have a hunch that the skewed dial indicator block on my machine may also affect the proper operation of the hard-stop - after all, the hard-stop is right next door to the indicator.
Incidentally, I have read online of other Facetron owners in the USA criticising the machine's hard stop mechanical system as not as good as other makes, but I think my experiences using the hard-stop may be worse than a 'straight' machine.
RC
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Dihusky

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Re: Facetron wandering dial indicator issue
« Reply #6 on: April 21, 2021, 04:50:36 PM »
Those photos RC show some pretty sloppy manufacturing. We pay good money for Faceting machines and one would expect a high manufacturing standard.

That said, if everything is fixed in place and tight, things should not move. If the machine is over cutting something is sinking/dropping, if it is only happening when you lift the quill, then there could be a problem with the bearings the quill arc rotates on or with the Hard Stop screw configuration.

What engages the dial indicator? Looking at the picture on the Operators manual, it doesn't show how this part operates and RC's photos make it look as though it might be concealed, which is a worry as it would mean taking the back of the machine off to find out what's going on.

mehoose

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Re: Facetron wandering dial indicator issue
« Reply #7 on: April 21, 2021, 04:59:49 PM »
RC, we have completely different machines but I too was experiencing  constant changes of depth of cut and realised my micrometer was swinging freely with every sweep and changing its position. I had to tighten a nut and just as well I asked Gearloose because I would've done it the wrong way.My machine is his old design but naturally the new 'owners' have started tinkering and cheapening the build.
Keep em comin!!!

RoughCreations

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Re: Facetron wandering dial indicator issue
« Reply #8 on: April 21, 2021, 06:02:51 PM »
Those photos RC show some pretty sloppy manufacturing. We pay good money for Faceting machines and one would expect a high manufacturing standard.

That said, if everything is fixed in place and tight, things should not move. If the machine is over cutting something is sinking/dropping, if it is only happening when you lift the quill, then there could be a problem with the bearings the quill arc rotates on or with the Hard Stop screw configuration.

What engages the dial indicator? Looking at the picture on the Operators manual, it doesn't show how this part operates and RC's photos make it look as though it might be concealed, which is a worry as it would mean taking the back of the machine off to find out what's going on.

Yes, it is concealed. Looks like I might need to operate.. sigh.
You can remove the dial indicator with two grub screws and peer down the hole from memory, not sure you can see much. I am hoping that the skewness is caused during the unit assembly, and not something harder to rectify such as holes/threads in the wrong position.
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RoughCreations

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Re: Facetron wandering dial indicator issue
« Reply #9 on: April 21, 2021, 06:04:20 PM »
RC, we have completely different machines but I too was experiencing  constant changes of depth of cut and realised my micrometer was swinging freely with every sweep and changing its position. I had to tighten a nut and just as well I asked Gearloose because I would've done it the wrong way.My machine is his old design but naturally the new 'owners' have started tinkering and cheapening the build.
Fingers crossed it's something that simple!
Cheers,
RC
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RoughCreations

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Re: Facetron wandering dial indicator issue
« Reply #10 on: April 22, 2021, 04:59:52 PM »
OK, so I have taken the back plate off my Facetron and have included some images as a reference for other Facetron owners if curious.

A.K.A How to void your warranty

The lever in the image below (seen from underneath) has a ball bearing sitting directly on top of it, then the tip of the dial indicator sits on the ball bearing.



You can see the ball bearing in this picture (view from top):



Opening up the back plate (below). You can see the two allen head bolts that I had to adjust to fix the skewed block. You can also just make out the small lever poking through the back plate. The lever sits against the back of the toothed, square section rod.



You can see the lever clearly in this shot of the back plate below:



You can see the little slot for the lever in the picture below as well as the possible location for a brass washer or shim mentioned below:



The machine is actually made of quite good quality components.

I think I have worked out what is going on. I have managed to fix the skewed dial indicator block by loosening the two allen head bolts, twisting and re-tightening - nice.

What I have also learned from opening up my machine is that the wandering dial indicator problem is not caused by the skewed mounting block. It is caused by excessive up/down play in the large brass toothed gear shown in the photos and in the video below hosted on YouTube. Watch this video and the others on my channel to get a better idea of what I mean, and to see what happens internally when changing angles and nearing the hard-stop:

https://www.youtube.com/watch?v=rNYbvlirbCQ

Some of the quill movement when approaching the hard-stop or zero position on the dial indicator is unfortunately transferred to (unevenly) lifting the brass gear a little (because it can), not to moving the dial needle smoothly, as it should. The small unwanted play present allows the dial to wander within those limits.

I reckon the dial indicator wandering problem could be fixed by pressing the shaft a little further downwards if that is possible, or by inserting a thin brass washer or similar in the position shown.

Some further investigations are required to determine the best approach.
RC
« Last Edit: April 23, 2021, 09:00:14 PM by RoughCreations »
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Bucket

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Re: Facetron wandering dial indicator issue
« Reply #11 on: April 23, 2021, 06:11:20 PM »
Wow, you're slightly gamer than me RC, but needs must. Sounds like you may be onto something with sorting the problem out. A thin shim from brass might help your problem, not sure where you'd get some that thin though. You're also right. it looks like there's some quality in the parts, glad I've got one now.
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MakkyBrown

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Re: Facetron wandering dial indicator issue
« Reply #12 on: April 23, 2021, 06:48:42 PM »
I have shim material in a lot of sizes if you want some RC.
MB

RoughCreations

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Re: Facetron wandering dial indicator issue
« Reply #13 on: April 23, 2021, 08:25:34 PM »
Wow, you're slightly gamer than me RC, but needs must. Sounds like you may be onto something with sorting the problem out. A thin shim from brass might help your problem, not sure where you'd get some that thin though. You're also right. it looks like there's some quality in the parts, glad I've got one now.

I made up a thin shim and installed it, tried my machine again - but it didn't help! The play that is present (that I was going on about) isn't an issue after all.
The problem was actually the little spring under the lever shown below - it's too short.


I removed the spring, added a slightly longer, stiffer spring I luckily had of about 18mm length (the original was 13mm long) so it reached the little lever better. I put the machine back together and it works like a charm!

Very happy the solution was so simple. The small and gentle movements of the gear mechanism that occur whilst cutting transfer to the dial indicator fine if the return spring is long and compressive enough to properly hold the toothed bar to the brass gear (see below). The return force present in the dial indicator is insufficient on its own.



My Facetron and I are friends again.

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Bucket

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Re: Facetron wandering dial indicator issue
« Reply #14 on: April 24, 2021, 10:11:06 AM »
Thankfully it was such a cheap fix RC. Glad you got it sorted, you'll have to start cutting again now. I'm hanging out ot get home and start again.
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