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Can anyone suggest where I can buy some 18mm wide linear caged roller bearings ?

richo132

Plastic
Joined
Mar 16, 2016
Need to source some replacement linear caged needle roller bearings.
Width 18mm and with 3.5mm needle rollers.
Have tried all the suppliers I know of without success.
Narrowest I have found with 3.5mm needles is 25mm wide and will not fit.

linear bearing.jpg
 

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What is the application ? How critical ? how much load . if critical buy gauge pins cut to length and grind axles on ends , 3D print the carriers metal or plastic . Cheaper 3.5 mm drill rod and turn axles and harden if loads require .
 
I'd suggest not using gage pins for this application, unless you go for the expensive X class I think they're not round enough or finished smoothly enough for any but crude applications.

If all you need is a small number of rollers, I'd suggest buying some needle bearings of the right size (rolling element diameter and width) and cutting them open to salvage the rolls. Then mill a carrier from bronze sheet or similar.
 
My understanding is that the rollers are very slightly crowned to prevent fatigue cracking at the ends. A truly cylindrical roller is undesirable.
 
The application is to support the sliding table on smallish tool/cutter grinder - Astra Elite.
Very low speed and low loading.
 
Given the low-demand use, I'd go ahead with using cut size (gauge) pins of good quality. Be sure to grind or cut the ends square, with a generous corner radius and polish them smooth to prevent cutting into the guides.

Speaking of, do you have existent guides or must those be made too?
 
Picture one clearly shows the "tits" on the end to lock into the retainer.
So just cut off some stock is not an option as there will be no guide pin.
Picture two is a different style so I am confused.
Some styles have the cage in between and flat end pins but I find none under 25MM wide in this pin size.
Which of these is the real carrier?
Normally in this type bearing they are not crowned.

This is a very good question and somebody made them.
Bob
 
...., do you have existent guides or must those be made too?
I bought the machine last year and it was in sad condition, much worse than I realised. When I stripped it down for cleaning and inspection I discovered that the table is supposed to rest on 12 linear bearings lying in the horizontal plane and be located by 6 more inside the rear dovetail. All the rear bearings were missing and only 6 of the horizontal bearings were present. The missing bearings have 48mm long cages and sit loosely in the races in groups of 3. After cleaning in an ultrasonic bath, the bearings that were present are reusable.
They have pressed steel cages but I would also be happy with replacements that have polyamide cages - hence the 2 pictures.

So far, the nearest bearing I have found is FF3020 - 20mm wide with 3.0mm needles. If I am unable to get exact replacements, I can see a couple of options:
  1. Re-machine the 18mm linear races in the top surface of the knee to 20mm and use FF3020 bearings. This looks to be possible but I'm not keen on the idea because it would weaken the side of the race and reduce the clearance between the knee and the table.
  2. Buy 3.5mm diameter x 13.8mm long needle rollers (listed by SKF and NTN) and make my own cages by milling parallel 3.6mm slots in an 18mm wide by 3mm thick aluminium strip. If I go down this path I would replace the 12 missing 48mm bearings with 4 x 145mm units.
 
Re-machine the 18mm linear races in the top surface of the knee to 20mm and use FF3020 bearings. This looks to be possible but I'm not keen on the idea because it would weaken the side of the race and reduce the clearance between the knee and the table.
[*]Buy 3.5mm diameter x 13.8mm long needle rollers (listed by SKF and NTN) and make my own cages by milling parallel 3.6mm slots in an 18mm wide by 3mm thick aluminium strip. If I go down this path I would replace the 12 missing 48mm bearings with 4 x 145mm units.
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Don't make cages from Al, it has terrible tribological properties. Either chose the right bronze sheet, or use PEEK or similar.

Given how few you need, I'd still go the cannibalized bearing route if you can find one with the right 18mm width. Using narrower rollers seems like you're asking for more wear. Making the cages long and using more rollers sounds good if the operating dynamics allows it.

Are you sure the machine running ways are in good shape, not worn or damaged?
 
After lengthy deliberation I decided to buy some needle rollers and have cages made by a 3D printing service. This worked out extremely well and I am very happy with the result. Cost per bearing assembly was AU$10 per cage and ~AU$20 for the needles.

Close up of 3D printed cage:
View attachment 281798

Assembled bearings installed in races:
View attachment 281799

Pleased to report that the machine is now back in working condition.
 
Hope it works out. Where did you get the rollers from, were you able to buy them independently? Please list the vendor, others will find it useful.

Keep track of the printed cages, if they start breaking up the misaligned rollers could cause problems.
 








 
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