Here is how I have replaced the rubber lagging on Underwood 3 Bank Typewriters and Corona 3 Typewriter:
- First remove the whole platen. Visit the link above on to see how to remove the platen shaft/knob and then the platen.
- The method I used below creates a new rubber, multi-ply lagging on the platen and I am happy with the result. I like to do things myself, so this method worked well for me. There are platen replacement services out there, which can be found on the internet, who will take your platen and reinstall a new one piece rubber platen. These services cost about $150 and advise that that is the most high quality way to go, vs the method I used below. I replaced my platen in October 2021 with the method below, and if the platen delaminates or fails in some way I will update this page to advise on that. The materials below cost about $15.
After removing the platen assembly from the typewriter, I checked the outside diameter of the rubber lagging. It was a wee bit over 1.25"
I was able to give the rubber lagging a twist and a pull and it came off the wooded platen body inside. The platen shaft with knob is shown on the right.
Carefully unscrewed both ends from the wooden platen body.
Now to the meat and potatoes of this project: Applying Marine grade, adhesive, waterproof rubber shrink-wrap tubing to the O.D. of the wooden platen body.
- I used 1.5" Diameter, 3:1 shrink ratio, Waterproof, Dual wall, adhesive, insulation-sealing, wear resistant, rubber shrink wrap tubing. https://www.amazon.com/dp/B07VLYMXDM?psc=1&ref=ppx_yo2_dt_b_product_details
-I cut it to overhang the wooden platen by about 1/4" on each end.
-Slide the wooden platen body into the rubber tubing
-I used a heat gun to gradually and carefully shrink the tubing onto the platen. Work the heat evenly around the platen, turning and spinning the platen carefully to shrink the tube evenly around the circumference of the tubing. Once the tubing was shrunk almost to the point of touching the platen, I then made sure to work from the center towards the ends. I think if one shrunk the tubing at the ends first, that this would trap air in the tube and create bubbling, so be mindful of that.
-Be careful not to burn yourself or to start things on fire, the heat gun get very hot as does the rubber. Do not do this near flamable materials and have a pair of leather gloves around to grab the hot platen. Do this at your own risk! Be careful!
-I repeated this with three layers of shrink tube, and at that point the outside diameter was perfect. I was lucky in this regard; if the diameter was too big, I would not have a good way to reduce the OD while keeping a nice surface on the rubber.
- I used 1.5" Diameter, 3:1 shrink ratio, Waterproof, Dual wall, adhesive, insulation-sealing, wear resistant, rubber shrink wrap tubing. https://www.amazon.com/dp/B07VLYMXDM?psc=1&ref=ppx_yo2_dt_b_product_details
-I cut it to overhang the wooden platen by about 1/4" on each end.
-Slide the wooden platen body into the rubber tubing
-I used a heat gun to gradually and carefully shrink the tubing onto the platen. Work the heat evenly around the platen, turning and spinning the platen carefully to shrink the tube evenly around the circumference of the tubing. Once the tubing was shrunk almost to the point of touching the platen, I then made sure to work from the center towards the ends. I think if one shrunk the tubing at the ends first, that this would trap air in the tube and create bubbling, so be mindful of that.
-Be careful not to burn yourself or to start things on fire, the heat gun get very hot as does the rubber. Do not do this near flamable materials and have a pair of leather gloves around to grab the hot platen. Do this at your own risk! Be careful!
-I repeated this with three layers of shrink tube, and at that point the outside diameter was perfect. I was lucky in this regard; if the diameter was too big, I would not have a good way to reduce the OD while keeping a nice surface on the rubber.
1.5" Diameter, 3:1 Shrink Ratio, Waterproof, Adhesive Shrink Wrap Rubber Tubing, cut to length to overhang the platen by about 1/4" on each end.
Here is the platen with 3 plys of rubber applied.
Diameter luckily turned out perfectly.
I let the rubber cool, and then carefully trimmed the ends of the rubber with a razor. Then I screwed on the ends.
Here is the other end of the new platen, showing the pawl gear reinstalled.
Here is the platen with new rubber lagging installed back in to my 1923 Underwood 3 Bank Typewriter.
This sample was done with nice light key strokes and I was very happy with the new rubber platen. Easier typing, better typed letters on the page, and quieter.