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Author Topic: Gemmasta GFE3 Re-alignemet  (Read 422 times)

Philip

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Gemmasta GFE3 Re-alignemet
« on: May 31, 2020, 05:37:31 PM »
Hi Guys

I have a Gemmasta GFE3 that i purchased about 1 1/2 years ago from it's original owner but in that time i have had nothing but trouble cutting on it.  From what I can tell, when i sweep across the laps I have a large variation in the cutting height, i.e. at the 1 o'clock position the stone is just shy of touching the lap but at the 5 o'clock position the lap is in contact with the lap.  This is the same across different laps.
Does anyone know of someone in the Melbourne region that refurbished or realigns faceting machines?  I have had a look at some instructions on how to re-align it myself and while i am good with my hands I would rather let someone who knows what they are doing have a look at it.

Thanks
Philip

MakkyBrown

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Re: Gemmasta GFE3 Re-alignemet
« Reply #1 on: May 31, 2020, 06:51:24 PM »
See if you can measure how far it is out. If you haven't a dial gauge, if the difference is less than the thickness of a sheet of paper I'd probably leave it. The biggest issue I've had with my gemmasta has been poor transfers. Using a transfer block fixes that.If it is out a lot on the horizontail swing you might need to undo the "do not undo screw". With my machine a found if i loosened it a bit and tapped with a plastic head hammer to move it worked well.CheersMB

REXL

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Re: Gemmasta GFE3 Re-alignemet
« Reply #2 on: May 31, 2020, 08:55:19 PM »
My GF4 had a similar problem after 25 years. The problem was a minute bend in the quill which I found after hours of measuring, checking etc. I bought a new quill.


Rex

Rusted

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Re: Gemmasta GFE3 Re-alignemet
« Reply #3 on: June 01, 2020, 08:13:12 AM »
Things I have found causing machines to be "out"

Worn mast base, You may find that the "outness" varies if you change the orientation of the base, so it will be out a certain amount with the mast base rotated furthest away from the lap as against rotated to the three or nine o'clock positions. Stick with the one position, the one you would use when cutting 90 degree girdle facets.
Get someone with a lathe to take a cut off the bottom of the base. That is an easy job it shouldn't cost much.
The slot where the mast base runs may be worn too, this will require a complete dismantle and a cut taken off the top of the base and the top of the lap bearing boss so they are both exactly the same.

You may find that someone has compensated for the worn mast base by packing the lap bearing up on one side. If you look underneath at the bearing housing and see the ends of bits of paper sticking out between the housing and the machine base then undo the three bolts and remove the paper.

Someone has fiddled with the do not undo screw, only touch this after eliminating the first suspects.
You really need a dial guage to get this accurate, you will need to build a quarter inch rod to go in your quill the other end mounted to your dial guage.  Sweep the guage across your lap, get a measurement. Carefully undo the "Do Not Undo screw" DNUS  and tap the head assembly lightly with a soft faced hammer, check and repeat, check and repeat. When it seems right do the DNUS back up and check again, if it has moved repeat all steps.

REXL I feel your pain, I walked into the club one day and found two people with a dop stick frozen into a quill, Aluminium dop, brass quill and water = corrosion, they had the dop in the vice and were stirring the quill like they were mixing porridge. I saw red but bit my tongue and took the quill out of the vice upended it and used a rod to drive the dop out from the other end. Oooh that was easy.

Dihusky

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Re: Gemmasta GFE3 Re-alignemet
« Reply #4 on: June 01, 2020, 09:32:49 PM »
Something that hasn't been included in the potential cause list, it sometimes referred to as 'casting creep' or warping. If a casting isn't annealed prior to machining the casting stresses may cause the casting to move, this is a known problem with Gemmasta machines, the solution is to skim the top of the base, bearing mounting face and mast mounting face. Then check the mast mounting is square to the mast.

This is the first part of re-aligning these machines that are consistently running out and laps, bearing wear, worn quills etc have been eliminated, having re-machined then you can tweak any final adjustments.

Philip

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Re: Gemmasta GFE3 Re-alignemet
« Reply #5 on: June 01, 2020, 11:08:07 PM »
Thanks for all of the replies guys.

I don't have a dial gauge to test with unfortunately. 

I'll have another look at it tomorrow night when i get a second and see if i can narrow the issue down a bit more.  I don't even get as far as transferring the stone before I have issues :(
To be honest i haven't had a lot of time to cut stones recently so I'll have a closer look and let you know what i find out.

Philip

Rusted

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Re: Gemmasta GFE3 Re-alignemet
« Reply #6 on: June 02, 2020, 10:21:33 AM »
Something that hasn't been included in the potential cause list, it sometimes referred to as 'casting creep' or warping. If a casting isn't annealed prior to machining the casting stresses may cause the casting to move, this is a known problem with Gemmasta machines, the solution is to skim the top of the base, bearing mounting face and mast mounting face. Then check the mast mounting is square to the mast.

This is the first part of re-aligning these machines that are consistently running out and laps, bearing wear, worn quills etc have been eliminated, having re-machined then you can tweak any final adjustments.

That is something I always suspected. I had the club rebuild the faceting benches out of sturdier materials because I suspected the wonky wobbly old benches were warping the machines. Good to know.

Dihusky

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Re: Gemmasta GFE3 Re-alignemet
« Reply #7 on: June 05, 2020, 06:58:59 PM »
I think any machine which sits on 4 legs as opposed to 3 might suffer from misalignment issues when on a dodgy bench. I've just been through everything on my Hall 2000 extended, Moth was discussing problems with his 2000, and discovered one of the four legs was 3mm different, so went about equalising all the legs and then a total alignment check. Going to be interesting doing the transfer on the current stone.

steveo

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Re: Gemmasta GFE3 Re-alignemet
« Reply #8 on: June 06, 2020, 01:38:16 AM »
I put a level on my machine 3 or 4 times a year and have a 1mm shim under one foot.
Steve

Philip

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Re: Gemmasta GFE3 Re-alignemet
« Reply #9 on: June 08, 2020, 11:33:07 AM »
Hi guys

Thought i would post a quick update.

I finally managed to get time to look at the machine late yesterday afternoon and found that I had a few issues.  Firstly the machine wasn't sitting on all of its feet so there was a slight wobble.  I can't change the desk I'm using so a temporary folded paper solution was required and it is now stable and level.  Next i checked the sweep across the base plate and found it was thicker than a sheet of paper, from my measurements on the fine height adjuster it was about .12mm out with the 1 o'clock side lower than the 5 o'clock side with the mid height being at about the 3 o'clock point..  While trying to measure this I i found i had to also tighten my fine height adjuster as it was too loose so that;s working much better now.  As i don't have access to a lathe and I don't know anyone that could re-machine the mast, etc. for me, I checked the issue was still present even if the mast was rotated and it was.  I took MakkyBrown's suggestion and loosened the do-not-undo-screw and then realigned it.  Initially it was worse but after a bit of trying i have now got the variation down to about 0.04mm and the mid point is sitting at between the 4 and 5 o'clock positions.

With everything tightened back up again i sat down last night and re-cut a square step smokey quartz piece that i was having issues with.  Last time i tried it i couldn't get the corners to meet at all and the facets tapered off to one side.  This time all of the corners meet without issue the facets are even.

Thanks again for all of your help and suggestions.

Philip


Rusted

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Re: Gemmasta GFE3 Re-alignemet
« Reply #10 on: June 08, 2020, 11:48:57 AM »
That's a win Philip.
Now you have had a look and a bit of a fiddle you know a lot more about your machine and how to get the best out of it.

MakkyBrown

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Re: Gemmasta GFE3 Re-alignemet
« Reply #11 on: June 08, 2020, 11:56:27 AM »
Good to hear it is better. If your machine is like mine there is always a tiny bit of play in the fine adjuster so the faceting head leans forward slightly. When cutting I roughly align the central position of pivot to the mid point of my cutting sweep. Except on girdle facets where you can't.MB

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