Amscope Double-boom replacement bearings

[Hoggy]

Well, I have the problem of the boom not sliding smoothly at at.
Judging by the descriptions of a couple videos I saw, I likely already have the hardened steel rods.

But the cheap lousy bearings seem to be the problem.

Amscope wants me to send the whole boom stand back for repair, which will likely wind up with the same bad bearings - on top of being without my precious microscope for a while.  I use that thing every day for non-soldering related tasks.

However, I've surmised that the bearings are likely held in the boom by two 1.5M set-screws I was able to access.  Also, I can't remember where, but I thought someone said that 2 bearings are needed.

The trouble being that I have no clue about bearings...  What I might need, to replace them with high-quality SMOOTH SLIDING bearings?

Does anyone have any idea on what and where to get the proper bearings?

[voltsandjolts]

I have the same problem, I've just been ignoring it for a while.
Looking closely at the stand, I see there is some text printed on the visible rubber seal of the bearing "L20UU", which seems to be the appropriate bearing:

https://simplybearings.co.uk/shop/p690008/LM20UU-Closed-Linear-Ball-Bushing-with-Rubber-Seals-20x32x42mm/product_info.html

Looks like there is two of these butted together in the sliding head.

Maybe someone who has done this fix already will be able to confirm.

[voltsandjolts]

The replacement options for this bearing seem to range from cheap crap "2 for 5 bucks" up to name-brand "1 for 50 bucks", with nothing in between.

Since you are in USA this might be a an option, if you are looking for quality bearings:
https://www.ebay.com/itm/224067293254

The same bearing here in the UK is £50 from RS!

[m3vuv]

are we talking about linear rail/bearings here?

[voltsandjolts]

Yes, linear bearings.

This guy had an issue with the rod material and ended up buying proper hardened rods:
https://technitoys.com/review-amscope-trinocular-boom-stereo-microscope/

I think this is the eBay supplier he used for the replacements rods:
"20mm Diameter Chrome Steel Linear Motion Shaft 32" inch Long Hardened Rod 813mm"
https://www.ebay.co.uk/itm/401637289882

[Hoggy]

Awesome!  Thanks guys!  (And yes, I've been putting it off for a long time too.  But I'm finally sick of the jerky movements when sliding it.)

Fortunately, I almost certainly have the hardened steel rods already..  There is no pitting or grooving either seen nor felt - and I've done plenty of sliding, albeit rough-riding.

I was about to immediately order these bearings when I thought maybe I should inform Amscope of the quality bearings.  I already have an open ticket about this rough-riding boom, so maybe they would order those and send them to me under the 5-year warranty?  Or should I just forego that and order them directly to make sure I get nice and smooth quality bearings?

One thing I notice is that Amscope (United Scope) doesn't respond to emails.  I had to file a Better Business Bureau complaint to get them to swap out the improper head when I discovered it wasn't simulfocal like I had ordered.

So maybe it's just easier to get them from that Ebay link.?   

[Hoggy]

Finally got a reply from Amscope.  So I just ordered it from Ebay.

Reply below:
-------------
Unfortunately, we don't send out parts for customer's to perform repairs.
What is covered under your warranty is the repair service.
 
You may send back only the parts that need to be fixed.
If you do not have the original packaging, please package it carefully in another box to prevent damages.
-------------

[aqibi2000]

I would highly recommend not using actual ball bearings for this application.

Find these, far smoother and there is no load so you don’t need ball bearings. This is smoother and a damaged surface by the old bearings won’t cause a hinderance.

No need for hardened steel rods.

[voltsandjolts]

Do you know a source for 20x32x42mm versions of those plastic slides?

[highpower]

[ Specified attachment is not available ]

Yes, linear bearings.

This guy had an issue with the rod material and ended up buying proper hardened rods:
https://technitoys.com/review-amscope-trinocular-boom-stereo-microscope/

Been there done that. The rails used by Amscope are made from soft steel that have a thin chrome plating applied to them. The balls in the linear bearings however are quite hard. This results in the hard balls crushing the thin chrome plating and compressing the soft steel under the plating. This fretting of the surface can been seen near the center of the rails in the picture of my original rails below. By the way the damage to the upper rail was evident after only a dozen or so movements of the scope back and forth through the bearings supporting it. Note that only the upper rail is supported by linear bearings. The lower rail is merely a guide rod that runs through the casting.

The replacement shafting https://www.mcmaster.com/6112K66/ I used is 1055 carbon steel that is deeply case hardened to C59 Rockwell. VERY hard. After machining the new replacements the scope now glides smoothly using the original linear bearings and without making any of the crunchy noises it did while running over the original shafts. The caveat being that proper linear shafting is hard as a coffin nail and doesn't machine easily. You need the proper gear to be able to cut it and turn it.

Edit to add: I forgot to mention that another reason the boom on my scope stand dragged so badly was because the original rails were undersized. They measured well below 20mm when checked with a micrometer. My guess is they made the shafts slightly smaller in diameter to allow for the thickness of the chrome plating they put over it. Problem is there isn't enough plating on them to bring the diameter back to the full 20mm. So with the boom extended the rails droop inside the bearing sleeves, causing even more friction & wear. The hardened and ground shafting I bought to make the new ones measures exactly 20mm in diameter and fit like a glove in the original bearing sleeves.

[voltsandjolts]

Replaced the bearings with INA KB20-PP as shown in the RS screenshot above but sourced from eBay at quarter of the price.
Bearings were perfect fit. Fixed it, so much smoother now.

[Hoggy]

Well, I replaced the original bearings with the linear version mentioned from Ebay (Shaeffler).

Now it doesn't ride like it was traveling on a gravel road - it's nice and smooth.

However, I seem to be having trouble figuring out how to get the dual rods lined up properly for it to be able to move as freely as possible.  It's now smooth, but not as 'free moving' as I had hoped it would be.  Getting the 2 rods properly in-line seems to be harder than I thought.

After much playing around, part of the trick seems to be the order in which you tighten the hex nuts all along the boom.  So far it seems to be the best I'm going to get it.
I did this by cranking the tightness of the focus/head attachment in place WITHOUT the scope head on it.  Then I brought the booms so that the area was smack-dab against the vertical post (pushed in all the way).  I then cranked the tightness for the boom arms (prevent from sliding) - this seems to line up the 2 arms very well for THAT end, to which I then tightened the hex screws for that end of the boom.  Then I moved the head-side farthest out from the vertical post (extended all the way out), and tightened down the rod-movement knob.  Then I tightened the hex screws for that end of the boom.

This seems to make it about as good as I might get it - there are no 'squeeze' points along the boom anymore, where it really stops wanting to move freely.
Now I know why they ship and replace the whole boom-arm assembly as a single piece.  But there must be a set procedure they use to do this at the factory.

I feel like I'm really close (if not already there), but wondering if other people had the same experience when replacing either the bearings and/or rods - and how they might have solved this?

[JonasCz]

Find these, far smoother and there is no load so you don’t need ball bearings. This is smoother and a damaged surface by the old bearings won’t cause a hinderance.

No need for hardened steel rods.

For reference those are often called "drylin" bearings, both original made by Igus, there are also cheap clones on aliexpress. You can also 3d print them (https://www.thingiverse.com/thing:1895518), but you need to add grease for that.

[voltsandjolts]

Interesting, thanks.
Igus part number "RJ4JP-01-20" is the right dimensions (20x32x42mm).
They do free delivery in UK so it seems you can get two delivered for £3.10 and they take PayPal!
Cheapest option I've seen, if I hadn't bought bearings already I'd be tempted to try these.
https://www.igus.co.uk/product?artNr=RJ4JP-01-20

[highpower]

This seems to make it about as good as I might get it - there are no 'squeeze' points along the boom anymore, where it really stops wanting to move freely.
Now I know why they ship and replace the whole boom-arm assembly as a single piece.  But there must be a set procedure they use to do this at the factory.

I feel like I'm really close (if not already there), but wondering if other people had the same experience when replacing either the bearings and/or rods - and how they might have solved this?

I would bet dollars to donuts that your rods are under size. (Less than a full 20mm in dia.) With the boom fully extended it droops in the bearings up top because of excess clearance, causing the lower rod to tilt as well and it rubs inside the housing.

Position it to where it wants to stop moving freely and then lift up on the scope head a bit and see if it starts moving smoothly again.

[jfiresto]

+1

I have a similar problem and use that fix with a grizzled, Swiss-made boom stand that has worn down its Teflon bearings. (In my case, the sleeve bearings have become too large.)

[aqibi2000]

Just use igus bearings

[2N3055]

Just use igus bearings

1+ for Igus

[Hoggy]

I would bet dollars to donuts that your rods are under size. (Less than a full 20mm in dia.) With the boom fully extended it droops in the bearings up top because of excess clearance, causing the lower rod to tilt as well and it rubs inside the housing.

Position it to where it wants to stop moving freely and then lift up on the scope head a bit and see if it starts moving smoothly again.

I measured ~19.90mm with a caliper, so not sure how much play is usually supposed to be in that number.

The main problem at first seemed to be left-right alignment (as if looking from the top) of the 2 rods when tightening the 'end caps'.  That strange order-of-tightening thing I finally conjured up seemed to correct that quite a bit.  However right now there aren't really any points where it binds up due to the right-left alignment of the 2 end caps.  It's smooth all the way across now - just more difficult to move than I had hoped it was going to be.

I tried lifting the head end slightly to see if it would move more freely, but it seems the same to me.

I have a feeling that my expectations were just too high.  I was hoping the new bearings would make it 'float in air'.    But there still is a lot of weight involved, so that was probably never going to happen.  At least it's smooth now though, and without much stiction (my bad memory seems to remember the old bearings having a high amount of stiction).

[voltsandjolts]

Interesting, thanks.
Igus part number "RJ4JP-01-20" is the right dimensions (20x32x42mm).
They do free delivery in UK so it seems you can get two delivered for £3.10 and they take PayPal!
Cheapest option I've seen, if I hadn't bought bearings already I'd be tempted to try these.
https://www.igus.co.uk/product?artNr=RJ4JP-01-20

Waking this thread to add an opinion...

So, I fitted two of the Igus RJ4JP-01-20 to an amscope double boom stand. It needs more effort to slide the head than with traditional linear bearings because you have to lift the weight of the head before it will slide. When at full extent, the slide action is more or less jammed until you lift the weight of the head. That said, when it moves it's smooth, despite the soft chromed (unhardened) rods having surface damage. My impression is that getting hardened rods and good quality linear ball bearings would be the best solution for me.