# LMS 3990 Mini-Mill



## ebolton (Mar 13, 2019)

I've had it for about a year, bought with my bonus money from last year. Right out of the box, one of the 4 holes in the base to which the column is screwed was stripped. I knew I could fix it with a helicoil, and returning it would be a pain, so I've lived with it till now. I think that has prevented me from getting a stable tram on the mill. Everything else about the machine has been perfect. It's been accurate enough for me so far even if it isn't as stable as it could be.

I've decided to up my game some, and I bought a DRO with this years bonus money. This was along with an M8 helicoil kit. Since the column needs to come off to get enough room to drill for the X axis DRO installation, it seemed like a good time to do both.

I pulled the column last weekend and helicoiled all 4 holes (why not?)  this morning. I plan on starting the DRO install this coming weekend.

I have no real point with this post...just an obtuse way to say "hello" I guess.

-Ed


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## markba633csi (Mar 13, 2019)

Hi Ed - sometimes it's advantageous to just drill and tap the holes up to the next standard size and use grade 8 bolts, stronger and more rigid
No reason to keep the original butter bolts when it's easy to upgrade, as long as you have the room to accommodate the larger bolt heads
Mark


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## ebolton (Mar 14, 2019)

I think the helicoils will get the job done, but if I ever have to pick them out of there, I'll probably keep it metric and go to M10.

-Ed


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## yendor (Mar 18, 2019)

Look up a product called TIMESERT as a Thread repair option.
Different from Heli-Coil but i have used these and find them to be much-much better.


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## Latinrascalrg1 (Mar 18, 2019)

ebolton said:


> I think the helicoils will get the job done, but if I ever have to pick them out of there, I'll probably keep it metric and go to M10.
> 
> -Ed


Going by your first post its apparent that you already feel that the single helicoil you added as a repair to the OEM mounting setup was causing you problems with getting the specs you are after thus making it the weakest link in your mind so i kinda find it difficult to see how is it that you feel that adding 3 more helicoils to the OEM setup will give you the  better results you are looking for?

I agree with Markba633csi that you would probably be much better off drilling out the old threads and tap it the Next size up.


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## David S (Mar 18, 2019)

I don't think Ed ever did do the one heli coil fix.  Sounds like he kept putting it off till he wanted to do the DRO and then did all 4 inserts.  I think that is what he is saying.

David


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## ebolton (Mar 18, 2019)

David is correct. I did put it off until I wanted to install the DRO. Since the column has to come off on this machine to do that, it was really no more work to fix the one bad hole I had been putting off. I decided to do the other three also, since I had plenty of inserts in the kit I'll probably never use for anything else, and I think the helicoils really improve the strength of the bolted joint. On this machine, when you need to tram it you have to loosen these screws to shim the column. The helicoils really make sense in this application. Or timeserts or keyserts, for that matter. I'm just more used to using helicoils.

-Ed


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