PFAFF 138 - Puzzled by double needle holder and compatible needle systems

[EMI]

This is my first post after a couple of years delving into the threads of this forum. First and foremost, I would like to express my gratitude and appreciation to this community for the great wealth of knowledge and expertise so generously shared for the benefit of everyone and especially members in need of assistance.
I am located in Athens area, Greece and have recently bought a wide (6mm) zig-zag version of the PFAFF 138-6 in very good condition, complete with table and clutch motor, missing only the presser foot knee lifter assembly (my search for replacement parts proved so far unsuccessful).

The full class designation details of the machine are 138-6/21 915/02-BS, meaning as per PFAFF coding system that she was configured from the factory for medium weight (B) fabric (S) and with part sets for cording & tween seams (915/2). 
As such she is fitted with an adjustable tween needle holder, part no. 91-064 652-91 (see attached dwg from parts manual and holder’s close-up photos for better illustration purposes).

According to PFAFF’s manual (as explained also in another relevant thread of this forum) she is supposed to be used with 438KK system needles of sizes from 60 to 100 for the “B” type. 
SCHMETZ catalog indicates 265KK and DPx438KK as 438KK equivalent and differentiate them from the regular 265 and 438 as having shorter shank.

Much of my confusion stems from the following contradictory facts:
1.    The machine came with a rather faded sticker on her face cover plate indicating what appears to be 134RK system needle (see photo). . 

The machine came with an assortment of PFAFF system 134 needles of various sizes from 120 to 180 (see photo).

Is PFAFF system 134RK the same as regular 134 ?
Are 438KK and 134 needles interchangeable? They appear to have the same length of 33.9mm to the needle eye and same 2mm shank diameter. I am not sure about the role of the shank length though.

3.  After thorough cleaning, oiling and adjustment of straight stich (“0” zig-zag width) position the machine appears to be sewing happily in all modes (straight & zig-zag) and full stitch range ( stitch lengths & zig-zag width) with the existing 134 needles and V69 thread. Apparently, needle bar length/hook timing has been adjusted for the dimensions of the 134 system needles.
However, it appears that the needle is partly grabbed in holder’s center slot between the two L&R adjustable blocks rather than fully inserted in the split hole provided for this purpose (the resulting hole with the L&R blocks matting surfaces in contact is to small for the 2mm needles shank).

This kind of needle mounting doesn’t look right from an engineering point of view and frankly speaking I don’t feel very comfortable operating the machine this way. 

4.  Since both 438KK and 134 system needles have a 2mm shank diameter, incompatible (oversized ?) with the existing smaller mounting holes of the needle holder, what needle system could be more suitable for use in a single (center line) or tween needle (L & R holes) configuration  in this holder? 

Since its the first time I am dealing with a single bobbin- double needle configured machine  I have no clue on how to proceed.  My intentions are to use her for medium weight fabric and canvas/upholstery work , supplementary to my other two sewing machines (a compound feed Consew 226R and a cylinder arm Adler 69 ) .

Any comment/advise on the above will be highly appreciated.

Thanks in advance for any possible response.

[Constabulary]

I´m not 100%  sure but the double needle holder where meant for small diameter shanks like the 287 / 1738 needle if I recall that correctly.

Edited November 3, 2020 by Constabulary

[EMI]

1 hour ago, Constabulary said:

I´m not 100%  sure but the double needle holder where meant for small diameter shanks like the 287 / 1738 needle if I recall that correctly.

Thanks for the swift response. I am trying to find a way to measure the internal diameter of the holder's holes so I could search for appropriate needles by their diemsions ( shank diameter/length). It appears though that the center hole diameter D1 is larger than the side ones D2. 

[EMI]

 

13 hours ago, Constabulary said:

I´m not 100%  sure but the double needle holder where meant for small diameter shanks like the 287 / 1738 needle if I recall that correctly.

Following the above suggestion I found in another thread here ( link below) that the 1738 system has been also proposed as a potentially successful alternative to the 130B for the PFAFF adjustable needle holder.

https://leatherworker.net/forum/topic/76473-pfaff-138-help/

On 7/4/2017 at 8:48 AM, alexitbe said:

An alternative to Needle System 130B is the 1738 needle system.  It has been used to some success on Pfaff 130-14-15 sewing machine, which is also requires the round schank 130b for its adjustable needle holder.  The 1738 is aka DBX1 16X231 16X257 1738.

 

Cheers

Alex 

So I've ordered some 1738/287/ DBx1 needles to give it a try and see. Their 1.62mm shank might fit properly in the holder's mounting holes. I will revert with the results in due time.

[Constabulary]

Are you sure D2 is the needle holder? The double needle afaik is for sewing tucks and for sewing tucks I think the two "D2 holes" are to far apart - or not?    If D2 are needle holders would the needles pass through the slot in the needle plate? I´m not sure... I´d rather say the 2 needles are clamped in the notch left and right of the center needle holder but 1738 most likely is the right needle anyway.

Edited November 4, 2020 by Constabulary

[nylonRigging]

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19 hours ago, EMI said:

Since its the first time I am dealing with a single bobbin- double needle configured machine  I have no clue on how to proceed.  My intentions are to use her for medium weight fabric and canvas/upholstery work , supplementary to my other two sewing machines (a compound feed Consew 226R and a cylinder arm Adler 69 ) .

Any comment/advise on the above will be highly appreciated.

Might have your machine model have come with ( 2 ) factory needle clamp setups ? , single and a double .
My Bernina 217 straight/zigzag combo machine as 2 thread tension assembly setup like your Pfaff model .  and also the Bernina offered 2 different factory needle clamp setup's to quick change out for single/double needle stitching .

( I don't think ? ) that ( D 1 ) slot in the center of the Needle clamp is for a needle . space ( wide gap )  in between the 2 needle hole, It In No Way resembles a hole to place a machine needle into . That needle clamp in your Pic. looks like a double-needle clamp only .

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[EMI]

3 hours ago, Constabulary said:

Are you sure D2 is the needle holder? The double needle afaik is for sewing tucks and for sewing tucks I think the two "D2 holes" are to far apart - or not?    If D2 are needle holders would the needles pass through the slot in the needle plate? I´m not sure... I´d rather say the 2 needles are clamped in the notch left and right of the center needle holder but 1738 most likely is the right needle anyway.

Thanks Constabulary & NylonRigging for your follow up.

I wish I knew !! However, I don't see the reason to be made by PFAFF with 4 channels (2 inner & 2 outer) if it was meant to be used only with the outside ones.

Things are getting even more confusing from the fact that 3 out of the 4 needle holes are drilled all the way through to the top (with the corresponding needles vertical travel terminating at the holder's recess top flange) while the inner channel of the left block stops short from the top (see attached photos). And while the diameter of the outer holes is approx. 1.62mm the inner ones are approx.1.8mm.

 

 

 

Edited November 4, 2020 by EMI
photos removal

[EMI]

I’ve checked the manual of PFAFF 130-115 (predecessor of the 138) to find any possible info related to PFAFF’s twin needle holder configuration.
As it turned out, the 138-6 twin needle holder seems to be a variation of the 130-115 one with essentially the same features. It is meant to be used as a single, double or triple needles holder with (most probably) 130B system needles.
Extracted pages of 130-115 manual hereby attached for easy reference.

It appears that round shank 130B needles are used in the outer holes.

A single 130B needle or two 130B needles may be inserted in the middle clamp jaws grooves.  For very fine cording two special type left and right needles 130BL and 130BR with flattened shank (like the domestic needles) are inserted in the middle clamp jaws grooves as a single needle with the flat surfaces facing each other.
I still didn’t manage to find out the purpose of the L & R middle grooves length difference though.

My biggest concern now is if the machine could be used with its current needle bar/holder and probably matching DPx1/1738/287 needles for my intended purposes (medium weight fabric & canvas/upholstery works with needles sizes up to 110/18-120/19) or shall I consider modifications to a regular 138-6 needle bar/holder ( assuming availability of necessary replacement parts).

Edited November 4, 2020 by EMI
Add extra photo, editorial corrections

[EMI]

After a more careful re-measurement of the needle holder holes I believe that my previous assessment is wrong, so please disregard my last post above.
The two outer holes are 13.5mm apart (a rather big distance for a single bobbin twin needle configuration) and of 1,44mm diameter (too small for any needle shank), so I tend to believe that they are just clamp’s slit termination strain relief holes and not needle sockets.
It appears to me that the only needle sockets are the two middle holes, approx. 1.85mm in diameter and of 7.93mm (L) and 8.72mm(R) length.

[EMI]

11 hours ago, Constabulary said:

Are you sure D2 is the needle holder? The double needle afaik is for sewing tucks and for sewing tucks I think the two "D2 holes" are to far apart - or not?    If D2 are needle holders would the needles pass through the slot in the needle plate? I´m not sure... I´d rather say the 2 needles are clamped in the notch left and right of the center needle holder but 1738 most likely is the right needle anyway.

You were absolutely right.