PT50- Slight Mods

[Mark Reich]

I recently finished my first spool of media for my fabulous new PT50. Congratulations EOU, the PT50 is really a lot faster and easier to use than the original KN100! 

I had a couple small issues with the PT50A. I don't know how the PT50B is different, so this may or may not be applicable.

I don't always have a pair of reading glasses around when I need them, so I was having a little difficulty with a couple things. 

First, it wasn't easy for me to always get the edge of the blade in the slot of the blade rest. Sometimes I would drag the edge across the hard plastic, which probably doesn't make any difference to a 150 edge, but I've been working with fine edges lately. The rest also seemed a little tall, so I decided to customize one of the two knife rests that were included.

I took the magnet off so I could accurately cut the height down to the bottom of the groove, and super glued a wafer of cork on top, which can't affect even a super fine edge. Not having to hit the slot just makes things way easier for me. 

  
It wasn't always easy for me to get the media under the plastic nut on the yolk because of the groove machined into the yolk. I just thought it would be easier if I didn't have to back the plastic nut out of the groove, so I ground the groove off flush.




A couple things- It was easy to grind the groove off perfectly with the bottom of the yolk on the table of a grinder, but I wanted the extra traction of the scratch pattern being horizontal instead of vertical. This was a little trickier, because I had to lay the yolk on it's side, which is round, and eyeball it. I'm not sure how much difference that makes, but I barely need to snug the lock screw, so it seems to work considerably easier to me.

*Special Note* If you grind the groove off the yolk, do not forget to blow the screw hole out with compressed air! There will be metal filings in the hole, which will ruin the plastic threads. Also, the edges of the top groove will be sharp after grinding, so make sure to ease them with fine sandpaper or a buffer.

Just my 2¢.  YMMV

[EOU]

Great ideas Mark! We particularly like the cork knife fulcrum. Would like to let you put a little wear and tear on that idea and then we'll check back with you. Very well done for certain!

Grepper and Rick KR have made some pretty extensive modifications as well to their ATFs. Maybe they could share as well with the Exchange.

Remember this trick as well; if you ever lose the test media down the feed hole don't fight trying to get that curly stuff fed back through. Grab a sewing needle, feed the test media through the eye and then run the needle in the bottom and out the top.

[Mark Reich]

Thanks Mike! Mr. KG  can easily make one for a real test. I seriously doubt I'm going to make a dent in mine in a very long time. You can sand it down and round it to keep it in good shape.

I can't believe those guys are withholding information! That's not the spirit, right Mr. Ken?

But if you work all the bugs out first, you only have to write once...    

If you don't let the media hit the hole in the hole it's easier, but yes, a threader sounds better.

The yolk looked perfect before I tried to change the scratch pattern....

[grepper]

Great idea Mr. Mark. I too have experienced some of the same issues you have with the thin (too thin?) slot. Cork is a great idea. It's free! I wonder if a little cut out piece of self-healing cutting mat might work too. My wife used to use one of those mats for cutting fabric with a little rolling cutter thing.

[grepper]

Mr. Mark accusingly blurted, "I can't believe those guys are withholding information! That's not the spirit, right Mr. Ken?"    

OK, Mr. Mark, here's what I did. 

The reason that I did not post this is because I am almost totally bereft of any vestige of spirit!

(Just kidding).  The real reason is because there is some question as to if modifying the TMF may influence the readings due to a difference in the length of the threaded media.  This can be seen the the 20% reading variance of the test clips, however the test clip media length is much shorter and over-tensioned.  Slightly de-tensioning the media in the test clip is claimed to return the test clip results to be equal, or close to the same as the TMF.

I'm sure Mr. EOU will correct if I labor under delusion, but it is my understanding that the length of the threaded media is more or less determined by where the media goes over the edges/sides of the TMF.

As you will see, my mod shortens the length of the threaded media by about 1/4", because I clamp the media at the edge rather than a little way down the side of the TMF.  It is my understanding that test media has very little stretch, so I would think that the difference in length of my mod would be of little consequence because it clamps the test media at the edge where it would normally be.  If indeed threaded media length is determined by where the media passes over the edges and media stretch is not really a contributing factor I would think that my mod would have marginal, if any, impact on readings.

Moreover, I have not done razor blade testing since I did this mod.  It would be a crude test verify that my mod had no impact on readings.

As I understand it, the gods of BESS certification are a picky and demanding lot. I get the idea that if you stare really hard at your TMF and even think about modification, your TMF would lose certification.  Now..., that is a good thing and completely necessary for a reliable standard. 

That said, before continuing to read, please check the following box to confirm that you have read and understand the Terms of Use Agreement.

OK, I'm done babbling.

The reason I did the mod was because I found it a bit fussy and slow to get the media under the screw on the side of the TMF.  When the media is pinched in the finger, it tends to hold the media off the side of the TMF and catch on the side of the screw rather than go under it.  This mod totally eliminates that, and reduces the process to a very smooth and fast operation of literally one or two seconds. 

I drilled a 45° hole in the TMF and stuck a stud in.  I made the little knob on the lathe from a chunk of 1/4" aluminum rod then drilled and threaded it.  The 45° knob is a lot easier to grab the the fussy little screw on the side of the original unit.  The bottom of the knob is just wide enough to cover the slot in the TMF so it can pinch the media at the out edge of the slot.
 
   

The top edge of the TMF is rounded and polished for two reasons.  One, it provides a flat spot for the bottom of the knob to grip the media at the edge of the slot and two, because it is so smooth all I have to do is get the media anywhere on side of the TMF, pull toward the knob and it effortlessly, automagically, drops into the slot. (The new nickel plated TMF units may accomplish the same smoothness without the need for additional rounding and polishing of the edge.  I did this on an original non-nickel plated unit.)

Putting the knob on a stud rather than having a screw that threads into the TMF, eliminates the problem of having the media getting additionally tensioned, pulled into and becoming stuck in the hole because with a screw, rather than a stud, the screw threads grab the media and pull it into the hole as it is tightened.  Another way around that problem is to counter drill a slightly larger bore at the top of the thread bore for the screw which is what is done on the standard TMF.  But that is another step which is eliminated by using a stud rather than a threaded bore in the TMF.

   

   

   

[Mark Reich]

Hmm... Well, at least I managed to remain on the side of law and order. At least until proven guilty.

Don't be such a cheater, Mr. Grepper. Your self esteem will grow back eventually.

[EOU]

Bernie is deep in the woods at his cabin this weekend. You guys can feel free to violate away.

[grepper]

When the cat's away...

Anyway, I do this stuff by myself, very late at night in the basement with all the doors securely locked.

[Mark Reich]

I was teasing, of course, Mr. Grepper. I appreciate the thorough thought process of your extensive modification.  

Are you bereaved simply because your mod disqualifies your TMF? 

Did you grind the mortise off your TMF straight away too, or did they originally come with a flat side?

I understand (now) that modification of the TMF (what the heck does that stand for?) is off limits for official score keeping. Of course I would never have thought of that. My only thought was , "This is really a lot more difficult than necessary". 

So theoretically (since we are able to discuss this for the holiday weekend), a guy should be able to grind the mortise off, without reducing the qualifiable length of media necessary, and install a more usable locking screw/stud/nut (whatever... something for fat fingers).... maybe? 

If the length of the media shall be constant as the distance across the top of TMF, it seems like your mod really doesn't shorten that distance very much, Mr. Grepper. IOW, the 1/4" length of the media from the groove to the screw on the side shouldn't count, theoretically, of course.

And one more thing, what is the difference between the PT50A vs B?

[Bud]

And one more thing, what is the difference between the PT50A vs B?

I can answer that Mr. Mark. PT50A has one gram of resolution and B has 5 grams. A is supposed to be more heavy duty  and faster as well. I've got a B and it works just fine as long as I press the edge down pretty slowly. Like the manual says, you're not chopping carrots, you're testing an edge.