Low Profile Adjustable Belt Tightener

by owen, published

Low Profile Adjustable Belt Tightener by owen Jun 5, 2012

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Adjustable belt tension with a screw. Low profile, suitable for Ultimaker etc.


Update: These won't fit on the 'Y' belts on newer UM's.
See Notes and Picture in the comments below.
Main picture here shows a clamp on the 'Y' belt of an older UM.

Parts required per belt

4 - M2.5 X 8mm small head screws. - http://www.ebay.com.au/itm/300521403792?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
1 - M2.5 X 30+mm screw. (35mm used here) - http://www.ebay.com.au/itm/370568422906?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
5 - M2.5 thin nuts - http://www.ebay.com.au/itm/120894813183?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649


  • Print 2 X Nut Side and 2 X Screw Side clamps for each belt (in there current orientation) and clean out with a 2.5 mm drill.
  • Work out where the outside pair will clamp to the belt and move the spot to the centre.
  • Twist the belt to assist in putting the clamp on.
  • Push through the adjusting screw all the way through the bottom clamp.
  • Place the other bottom clamp on the adjusting screw.
  • Put the nut on the adjusting screw a few turns and slide the free clamp up against it.
  • Clamp the top clamp onto the bottom clamp.
  • Tighten the adjusting screw and twist the clamps so they are horizontal.
  • Test tightness and adjust.


Over tightening makes it harder to move the extruder so test it still moves freely after tightening.

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Hmmm, this doesn't seem to fit in my Ultimaker on my Y. I wonder if they make the clearance less now?

owen - in reply to 3DTOPO

What's your measurement 3DTOPO of your gap there and I'll measure mine tommorrow and let you know if you like. :)

3DTOPO - in reply to owen

Thanks Owen! Mine is 9.38mm at best. The belt itself is only 2mm above the Y crraige block.

I see the difference now, they added a notch on the top left, here is a pic of mine.

owen - in reply to 3DTOPO

Yeah, I see the change.

Thanks for the update. DONT_KNOW

3DTOPO - in reply to owen

I think it is a conspiracy. Your belt tensioners made too much sense, so revisions had to be made! Note it renders your other belt tensioners useless for the Y as well.

I was able to install chasmaker's tighteners. I think the stock so called "tightener" really needs an overhaul - it was practically useless for me.