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21-9-2016 13:36:23  #1


Replacng a platen

At what point is a platen ready to be replaced? I have some machines that when I type with them, I get holes in the paper when typing, especially the punctuation marks.  I usually use at least two sheets of paper.  Should I try using more sheets or is this a signal that my platen is in need of replacement? Could it be part of my technique?


Smith Premier 4 typewriters are cool!
 

21-9-2016 15:56:43  #2


Re: Replacng a platen

Generally speaking, if you're blowing holes through paper, backing sheets and/or ribbon, it's the sign of a rock hard platen. I highly doubt it's anything to do with your technique. Some machines have an impression control meant for use with carbons; I don't know which models you're talking about, but if they don't have this feature then you will need to address the platen.

I would start with applying rubber rejuvenator to the platen. I have transformed unusable platens into ones that could were fine to type on with a backing sheet with this product. Search the forum for the term 'rubber rejuvenator' and you'll find it's been discussed often here and you'll get a few brand names of the products in case you want to buy and try it. Some dismiss the product, but I've used a durometer (a device to test the hardness of the platen's rubber) and have proved to myself that it works. On one machine it lowered the average durometer reading for the platen from 96 down to 93 after just three applications of the rejuvenator. A general purpose platen would originally be rated in the 90-92 range, and 93 is highly usable. 

The other option is to have the platen professionally recovered. This is good option for a machine that you plan to keep and use for a very long time, but prohibitively expensive if it's just another model on the shelf that you only use on occasion. 

Whatever you end up doing, don't sand the platen. Everything that I've read on the subject that was written by professionals and manufacturers strongly advise against doing this.


"To save time is to lengthen life."
 

21-9-2016 16:52:40  #3


Re: Replacng a platen

Uwe wrote:

Generally speaking, if you're blowing holes through paper, backing sheets and/or ribbon, it's the sign of a rock hard platen. I highly doubt it's anything to do with your technique. Some machines have an impression control meant for use with carbons; I don't know which models you're talking about, but if they don't have this feature then you will need to address the platen.

I would start with applying rubber rejuvenator to the platen. I have transformed unusable platens into ones that could were fine to type on with a backing sheet with this product. Search the forum for the term 'rubber rejuvenator' and you'll find it's been discussed often here and you'll get a few brand names of the products in case you want to buy and try it. Some dismiss the product, but I've used a durometer (a device to test the hardness of the platen's rubber) and have proved to myself that it works. On one machine it lowered the average durometer reading for the platen from 96 down to 93 after just three applications of the rejuvenator. A general purpose platen would originally be rated in the 90-92 range, and 93 is highly usable. 

The other option is to have the platen professionally recovered. This is good option for a machine that you plan to keep and use for a very long time, but prohibitively expensive if it's just another model on the shelf that you only use on occasion. 

Whatever you end up doing, don't sand the platen. Everything that I've read on the subject that was written by professionals and manufacturers strongly advise against doing this.

Oh, come on, now. I've been sanding platens for years, and know several old typewriter men that did the same.  None of the machines I did this to have had any adverse effect.  However, I will concede that if you can get a new one, or one recovered, it is always the best way.  The same with power rolls under IBM and other typewriters that use them.
 


Underwood--Speeds the World's Bidness
 

21-9-2016 18:45:54  #4


Re: Replacng a platen

TypewriterKing wrote:

Oh, come on, now...

I'm not making this stuff up.

My comments on sanding are from every manual that I've read, and when I discussed this subject with two professional typewriter repairmen who live in my area, both agreed with what was written in those professional books. One of the two men was factory trained by Underwood here in Toronto, and the other learned his trade in Europe, and after emigrating to Canada worked for a service shop that had large corporate accounts. 

This was written by Murray Harris who taught typewriter repair to learning repairmen and is an excerpt from his basic training manual:

"Never sand down a platen — you are doing the customer a disservice by sanding. Any platen that has a surface that is bad enough to sand needs replacing."

Another source:

"A newly recovered platen tested in a densimeter shows a dial reading of 11-13, which indicates the perfect medium grade used for most purposes. Old hard platens tested on the same machine show readings of 4.5, which is a definite indication that the platen should be replaced. A platen, sandpapered to restore a smooth surface, shows no improvement in resiliency (4.5) and impairs paper feeding action. Regrinding an old platen eliminates pits in the surface but does not improve resiliency or paper feed and causes the diameter to be undersize." 


The point of the second quote is that sanding does not soften the platen, and therefore the damage that is done to the machine when typing on a very hard platen has not been alleviated.

Some claim sanding is done to help prevent paper from slipping, which again is incorrect; the proper method is to wipe the platen down with alcohol, or better yet, a specifically engineered product such as rubber rejuvenator to remove some of the glazing that causes paper slippage.

I realize that none of this is likely to change your mind on the subject, and that's fine. You're free to do what you think is right with the machines that cross your path, and I'll continue to do what I believe is right with the machines that cross mine. I'm not one to make up solutions, after all, I am not a typewriter professional. I rely on the information that I find in published books written by professionals, which includes cleaning techniques and the chemicals most appropriate for the tasks.

Along those lines I don't think that I'll be offering advice any longer in the maintenance/repair sub-forum. It's a priceless asset when a professional such as thetypewriterman weighs in and helps someone out, but too often the rest of the advice from the rest of us turns out to be contradictory and ends up convoluting the information being given a novice who has no experience repairing machines. From now on I'll stick to repairing the machines that are local to me and limit my activity in the repair sub-forum to moderation duties.


"To save time is to lengthen life."
 

23-9-2016 15:27:06  #5


Re: Replacng a platen

I have to come down on the side of TypewriterKing !  In theory, and with unlimited money to spend, a re-rubbered platen is always best.  However, when the problem is poor paper feed, it can be transformed by sanding the platen down and throughly cleaning the feedrolls underneath.  Remember that back in the day, some firms paid their service engineers a commission for every re-rubbered platen.  In the same way, a new set of tyres on your car every year (regardless of wear) would give good results.  However, you would normally only replace your car tyres when you actually needed to !  And yes, I sand platens quite often too

 

23-9-2016 16:56:20  #6


Re: Replacng a platen

The OP was concerned about her typewriter having a hard platen, something that sanding will not change. And as for improving its grip, rubber rejuvenator works wonders with the added (primary) benefit of softening the rubber at the same time. I've never needed to touch a platen with sandpaper, and never will.


"To save time is to lengthen life."
 

23-9-2016 17:31:01  #7


Re: Replacng a platen

Replacing, or recovering a platen, though the proper procedure in repairing platen issues, can be prohibitively expensive, and don't you have to have a minimum number of platens or other rollers to be able to have the work done (I remember the name J. J. Short as a company that still does this work).  I have been toying with using a thin rubber "backing sheet" between the platen and the paper.  I have, for a long time, used at least two extra backing sheets of paper.  My primary concern is the type slugs.  I worry about the wear and tear on them, and for years, I have used backing sheets of paper.  I used to use only one, but lately, I've been using at least two.


Underwood--Speeds the World's Bidness
 

23-9-2016 19:17:53  #8


Re: Replacng a platen

TypewriterKing wrote:

don't you have to have a minimum number of platens or other rollers to be able to have the work done (I remember the name J. J. Short as a company that still does this work).

J.J. Short does individual platens. I have not sent them any feed rollers--so I can only speak about the platens--but there is no minimum order for platens. I have had them do several. They do excellent work.

 

23-9-2016 19:19:27  #9


Re: Replacng a platen

When I sand a platen, it's primarily to resurface it rather than to improve its grip, although that sometimes does happen.  I've seen platens so pitted and eat up so bad I would take one off of an old parts typewriter and use that in the other one's place.  I've also had to sand down out of round rollers and put heat shrink tubing over them.  I've also sanded down IBM power rolls as a quick and dirty until I could get another roll to put in its place.  Yes, if you have, or can get, proper replacement parts, it's the best thing.  But if you can't, you just have to work with what you've got, or you have to put the machine away until you can get the parts.


Underwood--Speeds the World's Bidness
 

24-9-2016 23:30:45  #10


Re: Replacng a platen

I appreciate all the thoughts on the subject.  I will just have to see about having a couple of platens recovered by JJ Short.  I have been using several of these machines quite a bit and will have to see what it will cost as money is tight at the moment.


Smith Premier 4 typewriters are cool!
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