Replacement for THK GSR20T LM Block and rails

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23 Jan 2025 02:42 - 29 Jan 2025 16:15 #319688 by langdons
I am repairing a 30 year-old CNC machine.

It is a 3-axis XYZ CNCX router.

It uses THK GSR20T LM guides and rails on all axes.

The X axis and the Y axis work great.

However, I only have 1 working LM guide for the Z-axis (2 are broken, 1 mysteriously disappeared).


I really don't want to buy 3 THK LM blocks, they are absurdly expensive.

The Z-axis does not have to be quite as strong as the other axes.

Would it be make sense to just buy new Chinese rails and LM guides and just sell the existing rails and LM block (plus the broken LM blocks)?

Are there any LM blocks that use M5 screws and have the same screw layout?

Thanks!
Last edit: 29 Jan 2025 16:15 by langdons. Reason: Removed unnecessary requirements.

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  • rodw
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23 Jan 2025 03:11 #319689 by rodw
Funny, I was looking at these earlier today. Have a look at  Hiwin HGR rails, I know the heights are the same. No idea about the rest of the specs.

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23 Jan 2025 03:19 #319690 by tommylight
Replied by tommylight on topic Replacement for THK GSR20T LM Block and rails


Are there any LM blocks that use M5 screws and have the same screw layout?

The rails also need to work with the existing anchor holes, which are also M5.

Let me see when i have some 20 minutes of free time to search the web for the THK specifications as PDF and another 10 minutes to sift through them to find the hole raster.
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The following pertains to several topic where you keep refusing to provide the required info, so a friendly advice, stop shooting yourself in the foot consistently and get us the info so we can help you, i have at least 10 types of rails and carriages, i mostly know their hole raster for all of them, i can not help you as i do not have time to do the work you are supposed to do.
Some examples:
HiWin HGR25 has a 60mm M6 rail raster and 35mm M6 carriage raster
THK35 has 80mm M8 rail raster and 45x55mm M8 carriage raster
THK45 has also 80mm but M10 ratser and 55x35-35mm 3 rows of M10 carriage raster
Now i can miss something, but i have them, so i can easily recheck.

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23 Jan 2025 04:20 #319692 by Cant do this anymore bye all
Replied by Cant do this anymore bye all on topic Replacement for THK GSR20T LM Block and rails
Agree totally with Tommy.

See the dentist chair wasn't such a silly suggestion

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23 Jan 2025 15:16 #319717 by langdons

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23 Jan 2025 15:23 #319718 by langdons
Replied by langdons on topic Replacement for THK GSR20T LM Block and rails
I was just wondering if anyone knew of something.

Who knows?

Perhaps someone else has successfully replaced a THK GSR20T LM Block

That's all.

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23 Jan 2025 15:32 #319719 by Cant do this anymore bye all
Replied by Cant do this anymore bye all on topic Replacement for THK GSR20T LM Block and rails
Look mate when the guys were trying to help you with your homing issue you refused to supply your ini & hal files. Do you get it ?

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24 Jan 2025 22:01 #319788 by langdons
Replied by langdons on topic Replacement for THK GSR20T LM Block and rails
I fixed the homing.

But I do need to figure out this Z-Axis.

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29 Jan 2025 16:13 #320093 by langdons
Replied by langdons on topic Replacement for THK GSR20T LM Block and rails
The LM guide and rail must meet these requirements:

Use M5 screws externally (to anchor the rails and to attach something the LM guide)

The LM guide must have 4 M5 threaded holes, with the centres of each hole arranged in a 30mm x 20mm rectangle.

I can drill new holes for a new LM rail with a drill press, though I need a non-standard hex key that is long on both ends in order to remove the z-axis support.
The z-axis is attached to 4 GSR20T LM guides with 16 M5 screws in a recessed hole.
I need a hex key that has 2 long sides; one that is long enough to penetrate the recessed hole, and another that is long enough to amplify torque.

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29 Jan 2025 16:19 #320094 by langdons
Replied by langdons on topic Replacement for THK GSR20T LM Block and rails
The LM blocks are not directly connnected to the Z-axis, there is a steel spacer with screw holes that is about 5mm thick between the LM guide and aluminum Z-axis thingy.

Don't ask me why. Canadians are not known for their CNC machines. The only people who would ever buy a Canadian-designed CNC machine is a Canadian school board.

It's also 30 years old.

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