Presto 1-B guts and questions

[electronrancher]

Hi Folks,

Got a 1-B, and I'm currently cleaning it up and getting the lay of the land. There is zero gap between the armature and the E-shaped laminated iron cores on either side, this can't be right - can it? Can anyone advise me on what gap I should be seeing between the E's and the armature?

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When I look at the E-cores, their screws do not seem centered, which adds to my suspicion. Is this something that the little guy can recover from, by just removing and reinstalling the E-cores?

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Also thought the damping was curious, decided to throw up a pic. I expected it to be more similar to the 1C/1D stuff I saw on here, a big old block of elastomer. This one's got just a little cube.
A pic of the weird little block of elastomer. Still soft, but kind of squashy like those moldable grey eraser blocks artists use. Any hints on whether that's correct, or whether it should be purely rubbery with no deformation?

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[Fela Borbone]

Hello,
Yes,you are right,to allow movement threre should be an air gap between armature and E polepieces. I settle mine loosenig screws and placing plastic strips of about 0,20 mm. thick in the gap while adjusting. I remove the plastic when finished .

[Fela Borbone]

But before that, you may want tho make shure the stylus is at 90 deg. Using a long metal bar instead of stylus for reference,

[Fela Borbone]

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[Fela Borbone]

The bar in place of the stylus can be adjusted with the little screws at the back, but be carefull! Too much pressure can break the screw head or permanently deform the spring. Note the locking screws before the spring drive screws.
0,2 mm can be actually more than needed,
but it works for me,despite i dont need such a big deflection

[Presto Repairs]

but be carefull! Too much pressure can break the screw head or permanently deform the spring. Note the locking screws before the spring drive screws.
0,2 mm can be actually more than needed

Start with the centre screw that has the straight pin, Then begin balancing the top and bottom screws....

[electronrancher]

Thank you all for your replies and advice! I have also been speaking to Markrob and his comments are in line with your own - those clever tips and tricks from those "in the know".

I am interested if there is any guidance on the B spring (straight middle one) that holds the armature to the knife edge. I did take it apart (of course) and put it back together rather gently, but this seems as if "too loose" would run the risk of rattling/distortion so I imagine I'll have to do a bit of tuning here.

The alignment rod and gapping tricks are great stuff - anything similar for the B spring?

[Fela Borbone]

Hi,

The certre segment (I dont think it has spring asction,but holding the blade hinge in place) can be reproduced whit a 1mm or so drill bit, making its ends conic by placing it in a drill and sanding it in rotation against sanding paper 1000 or over, at a not too critic angle, but 45deg can work.
In the Presto datasheet says that the adjust has to be done at the microscope(?). But I dont know what to look at. Instead i place the metal bar(1.6mm welding electrode) in the stylus place. This amplifies the "feel" of the hinge action when hold with my fingers and , taking into account that the armature is in place,the segment is at 90 deg to the armature, and it moves but feeling smooth witout feeling little strokes, i secure the screw.

[Presto Repairs]

Hi,

The certre segment (I dont think it has spring asction,but holding the blade hinge in place) can be reproduced whit a 1mm or so drill bit, making its ends conic by placing it in a drill and sanding it in rotation against sanding paper 1000 or over, at a not too critic angle, but 45deg can work..

The centre pin is not a spring, merely a locking pin, I've been working on a jig to make the A+C springs, I have the straight B pins in stock but chose not to announce anything until I had perfected the A+C springs...

Just like the A+C springs, the centre pin is held in place by a very small recess on the armature - the difference is that the b pin sits further in + locks the armature to the knife edge and the A+C springs are used to balance/centre the armature...

If the b pin is not secure, then yes distortion is a real possibility.... At the same time, if you over tighten damage to the screw, pin and knife edge are all possible...

Although the data sheets say calibration should be done with a microscope, it isnt necessary... Feeler gauges, plastic strips, right angle tools etc can all be used....

[electronrancher]

Cool, thanks guys. I need to get some of that drill rod! I had no time to mess with it tonight but I will give your suggestions a try tomorrow.

Great to know you will be a source for the pins, PR. Setscrews as well? As you see my bobbins are shot, so I might be in the market for a misc parts tuneup kit soon.

Tell me, when you mention feeler gauges - are you actually shimming something into the v-slot to check the tightness? Looking at it briefly, it seems there's lateral motion if the knife edge is not tight. I am guessing that is what they were using the microscope for, but it's just a guess. I'd be interested to hear how you do it day-to-day.

[Presto Repairs]

Cool, thanks guys. I need to get some of that drill rod! I had no time to mess with it tonight but I will give your suggestions a try tomorrow.

Great to know you will be a source for the pins, PR. Setscrews as well? As you see my bobbins are shot, so I might be in the market for a misc parts tuneup kit soon.

Tell me, when you mention feeler gauges - are you actually shimming something into the v-slot to check the tightness? Looking at it briefly, it seems there's lateral motion if the knife edge is not tight. I am guessing that is what they were using the microscope for, but it's just a guess. I'd be interested to hear how you do it day-to-day.

They used a microscope to ensure that the armature was sitting dead centre ontop of the knife edge. After 70 odd years the knife edge looses its edge so to speak...

I have found that laying the cutter on its side positioned on the edge of a bench where I can access the screws from below and begin setting the b screw and balancing the A+C screws helpful and I can also check over the calibration at any time with my usb microscope...

I dont place anything in the v slot... the feeler gauges are used for spacing the armature between the polepieces...

http://www.kincrome.com.au/product/412092/feeler-gauge-32-blade-metric-and-imperial-105mm-(4~)

I actually have to check with my supplier to see if they have some locking screws because I am in need of 2... ill let you know how I go...

[Fela Borbone]

Found a lock screw screwed in the center of my 1D, apparently for no pourpose (?)
Presto Repairs, Its great to have repair service and spare parts of Presto guts, you are doing a great work!

[Presto Repairs]

Thanks Fela,

The 1-C and 1-D Usually have a spare locking screw (aka grub screw), placed in the horizontal block on the back of the frame that the back cover is fastened to...

I could just go through my heads and take the spares, , but it doesn't solve the problem as it will leave several heads without a spare...

The real question is why did presto supply an onboard spare when all the paperwork available suggests that adjustments/calibration/repairs "Should" be done at the presto factory...

My guess is the word "Should" was used to encourage the masses to send their heads back to the presto factory and the spare grub screw was placed onboard so that the minority who chose to adjust/calibrate/repair their cutterhead independently could do so... (Catering for everybody, so to speak)

Being a 1 man operation with limited space, I simply cannot cater for the massess, but I can assist the minority...

My supplier has grub screws listed but I have to check if they have the correct size and length, otherwise I will undertake manufacturing them myself...