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Dupont Delrin/Staglon Research

Discussion in 'Schrade Knives Collectors Forum' started by Codger_64, Dec 9, 2006.

  1. Codger_64

    Codger_64 Moderator Moderator

    Oct 8, 2004
    As with any major manufacturer, cutlerys are constantly seeking new processes, designs, and materials to increase market shares and profits. Progress in all of these has been exponential throughout the past century, particularly here in America.

    Handle materials early on were mostly one of three materials; Metal (as on a lot of “waldemar “ knives), jigged bone (also including antler and horn), and synthetics (mainly variations of celluloids). Each of these materials have negative traits which caused the knife manufacturers to try all types of alternatives.

    The progress made in the 20th century in plastics development was key to the advancement of knife handle materials. Celluloid, somewhat corrosive and dimensionally unstable (and highly flammable), was replaced by more modern plastics which were in many ways just as nice in appearance, and much more stable over a long period of time.

    Likewise, natural animal derived handle materials were by and large replaced with plastics formed to imitate the appearance and feel of bone, antler, and horn, as well as ivory. A revolution in plastics molding technology, co-developed with improved plastics, eliminated much handwork required in matching and fitting the natural materials.

    Also, the advent of processes to “anodize” metals and plate plastics made it possible to own a “gold” or “silver” knife at a fraction of the cost of the genuine article.

    Early plastic handles were a type of styrene. Styrene is more stable than celluloid, and cheaper than imported antler to produce and assemble, but still not both hard and completely dimensionally stable.

    Delrin

    The real revolution came when Dupont invented Delrin. Delrin is an acetal thermoplastic resin (PolyOxy-Methylene or POM) which has a semi-crystalline structure, is machinable, and possesses excellent strength and dimensional stability, high lubricity (low friction characteristics), and good wear resistance.

    Dupont’s advent of Delrin came about from their post-WWII search for wider applications of their popular nylon. When Department director Frank McGrew and their chemists in the Polychemical department searching for a plastic replacement for metals first came across the formaldehyde derivative which we now know as “Delrin”, they named it “synthetic stone”. This was circa 1952. It took another four years of development to refine the process for production and in 1956 they were granted the patent for Delrin. Another four years and twenty million dollars was invested in a facility to manufacture Delrin, and in 1960 the plant in West Virginia opened and began large scale production with a twenty million pound annual capacity.

    After a total fifty million dollar investment, Dupont cited patent disputes and competition for shallow profits on the material. Bad for Dupont, but a boon for the knife industry as Delrin quickly became a premier handle material for many companies, Schrade and Camillus included. Nearly fifty years later, Delrin is still an important material in the cutlery industry.

    Along with the properties of Delrin already mentioned, another very important one exists which makes this plastic such a winner for knife handles. It can not only be colored as a base material, but it can be dyed after molding to add accent colors. This is what gives “Staglon” it’s stag appearance, and “Genuine sawcut Delrin” it’s sawn bone appearance. Early in my explorations of the Schrade manufacturing processes, I assumed, as most people do who give it any thought whatsoever, that the “dual tone” of the Schrade knives was the result of applying the darker colored Delrin to the inside of the mold before injecting the lighter base material, the heat fusing the layers, then buffing or “glazing” removed the high areas of the darker material leaving highlights which closely approximate the natural material. I later learned from a former employee the actual process.

    After the Delrin handles are molded, sprues and gates (sometimes called runners) trimmed, they had to be dyed. Two heated dye tanks are used, one brown for OT covers, and an additional black for the UH covers. The tanks were heated to 180 degrees, far below the melt temperature of Delrin. but hot enough for the dye to penetrate the surface and set. I am not familiar enough with this particular dye to tell you what the color base material and mordant are, but most dyes (as with most paints) have mineral base ingredients. A mordant is a chemical (usually acid or alkali) which acts as a penetrating agent and carrier solution. Like the vinegar used with Easter egg dyes. In this case, it could well have another type of mordant.

    The covers were dumped into the first dye vat and an operator stired the parts every few minutes to prevent the parts from streaking from dry spots, and weakened dye, or contact with the vat. They also occasionally lifted some parts with the stir paddle to check the color. If the dye was fresh, time in the dye tank was about 25 minutes. When the dye was weakened from use, dying times were extended by the operator to compensate, until they judged the dye needed replacement.

    This whole operation was dependent upon the judgement of the operator. When the parts reached the desired color, they were removed from the dye vat with a shovel and are placed in a basket in the rinse tank. After rinsing clean, the basket was lifted and drained, and the parts spread on a drying table. Ours in the machine shop are perforated stainless with reversible air flow for updraft heated air, or downdraft cool air, depending on the part.

    At this point, the covers would be a uniform dark brown color. For the UH covers, they went from the brown dye (approx. 15 min, or until the proper reddish brown color is achieved) then to the rinse, then to the black dye tank for another 10 minutes or so, depending on dye strength. They were again rinsed, and went to the drying tables.

    Now, considering the number of manual steps required, and the amount of objective judgement required by the operator, you can see why they were trying to streamline the process.

    I have several knives assembled with undyed covers, and also several with the dye not reduced by glazing. Some of the tan base knives have had a slight dyeing, some not, all I have seen are buffed, and yes, in my collection of 897UH knives, I have a pretty wide variety of color combinations. The tan was used occasionally for them instead of the ivory (the resulting knife type often called a "buckskin"). And dyes seemed to change with some knives having distinct reds and yellows, while others (most particularly the later ones) were more consistently colored. A part of this would be attributed to changing operators over the years (and dye strength), but some are because of experimenting with different dyes since the UH introduction in 1967.

    The dark knives are not buffed at all. Backspring pins are still conical and proud, and the peaks of the stagging on the cover are really sharp, and also proud of the bolsters. The nickname of this dyed but unreduced type is a "blackie", and they are an interesting variant, though they are just the product of leaving out the finishing manufacturing step, whether on purpose or by accident. I have blackies in three different UH patterns, all came from an estate collection (where they had been for years), so they were not factory leftovers. Perhaps the collector ordered these from the factory this way.

    The fact that Delrin takes and holds dyes so well made the material a good substitute for celluloid handles of ad specialty knives also. A heated die was pressed onto the handle over a dye tape, scoring the handle and filling the impression with dye. In 1975, the resident Schrade artist, a very talented man by the name of Frank Giogianni, bored with the commercial art he created for packaging, logos, and commercial ad knives, presented Henry Baer for his consideration a cream Delrin handled scrimshaw knife of his own design. Baer enthusiastically approved and the commercial art became creative decorative art and the popular Scrimshaw series was born.

    In late 2002 or early 2003, a significant manufacturing process change was begun. Previously, the 34OT Middleman covers (scales) were molded in the Ellenville factory from tan base material as slabs, then batch dyed with the brown accent color. They were then placed in a die that cut the slabs to exact length and punched the pin holes. When the covers were mounted and glazed (finished) flush with the bolsters on the ends, the tan base material showed abutting the bolsters. With the new process, the covers were molded to length with the holes in place, then dyed. These new covers can be spotted because the ends next to the bolsters are dyed, and a thin brown line is formed at the joint. While all assembly and finish work still took place in Ellenville, the covers themselves were imported ready to assemble, saving molding, cutting and dying steps. Knives with these new style covers include all of the 2004 anniversary issues, both in the Centennial tins, and the dual shield editions, as well as all regular 2003 / 2004 production.

    Other patterns were scheduled for the same process change such as the 108OT, 807UH, and 834UH, so a few of those may be seen with similar characteristics, but there were, as with any major process change, problems encountered which were being worked out on the 34OT while the other patterns were mostly assembled with the older style covers in the traditional manner. It is uncertain how many of these other patterns were produced using the new covers. Probably sample amounts of 200 or less, if any. I have in my collection the 834UH and several other examples of the new cover dye process.

    One drawback of the dyed Delrin is that it is not absolutely colorfast under prolonged UV light. No doubt, you have seen faded handles on Old Timer fixed blades and covers on folders that spent a lot of time in displays under florescent lights, or worse yet, in direct sunlight. I have had some success in restoring the color by burnishing, then applying some light oil to replenish the volatile oils originally in the surface of the plastic.

    A “worst case” example came to me with almost all of the accent color gone, rubbed off during years of hard field use by an old hunter. The appearance of the Staglon on this one was somewhat restored by applying Feibings leather dye in several light coats, drying and buffing between coats. As the original dye was composed of both brown and black baths, I applied first the brown, then followed with black. The result was acceptable for a user. The dye did leave a shinier surface than the original, but I could buff it with OOOO steel wool and get a more “factory” appearing finish.

    Codger
     
  2. tobyrogers

    tobyrogers

    786
    Oct 8, 2005
    Good information Michael.Did they buff the sides of the handles,around the tang on the 152, to take the dye away.Arnold
     
  3. Codger_64

    Codger_64 Moderator Moderator

    Oct 8, 2004
    Any area where you see the underlying base material on the OT/UH knives was glazed, I believe. As the entire cover blank was submerged in the solution. even the backs, ends, and sides were dyed (as well as the shield cavities). I don't have any examples of unfinished Old Timer fixed blade knife scales to examine and show, and am not in a position to obtain any from the only possible source, so this is presently only speculation based on knowledge of the process. Perhaps one of you has, or can obtain a set to confirm this.

    Michael
     
  4. fireman

    fireman

    201
    Dec 27, 2005
    this is the tyope of info that i just adore!!! i have seen the differences in UH handles, and noticed that the design is basically the same on most, especially the 885, but have often wondred why there is a difference in tones. again michael, u have ridden in and saved the day! thanks for the info, it is greatly appreciated!!!

    kris
     
  5. Codger_64

    Codger_64 Moderator Moderator

    Oct 8, 2004
    I brought this post forward to augment the answers on Dupont Delrin in a current thread. The computer I am on will not allow me to copy and paste text or web links. Danged cybernanny!

    Michael
     
    bucksforus likes this.
  6. knarfeng

    knarfeng senex morosus moderator Staff Member Super Mod Moderator

    Jul 30, 2006
    Thanks for bumping the thread. I'd never seen it and appreciate the information.
     
  7. Dave Thinkstoomuch

    Dave Thinkstoomuch Banned BANNED

    Jun 15, 2009
    (bumped thread again) This is great info!
     
  8. delmas2nd

    delmas2nd Gold Member Gold Member

    984
    Apr 14, 2008
    this is why this site is sooo nice. lots of information freely given.
     
  9. xbxb

    xbxb Basic Member Basic Member

    Jun 23, 2005
    Thanks so much Codger---hope things improve more for you
     
  10. Codger_64

    Codger_64 Moderator Moderator

    Oct 8, 2004
    I have put a lot of effort into the research posts I have made on this forum since 2004, and I hope that those who are interested in reading them will go to the minor expense of obtaining a membership so they can do a forum search to find them. Quite a few people helped me find and correct this information including Larry, several former Schrade employees, other collectors, original company archive materials etc. Until I ever get around to publishing this information in printed form, this is your best chance to access it, here in these forum archives.

    Michael
     
  11. tongueriver

    tongueriver Gold Member Gold Member

    Dec 28, 2007
    And I appreciate your research and help a lot, Michael. A great season to you, Sir!
     
    Last edited: Aug 3, 2015
  12. Dave Thinkstoomuch

    Dave Thinkstoomuch Banned BANNED

    Jun 15, 2009
    I hear ya. I truly appreciate your efforts. When Spark accepts PayPal I will upgrade mos def. I know this has been somewhat of a sore issue and I know where I stand. Last I read Spark said he was gonna start takin PayPal but whenever I try to join it hasn't happened yet... It would make it much easier to join for all Canadians. So far I have been trying to "give back" with anything interesting I find out and am also committed to sharing knowledge.

    Thanks again Codger for taking the time you do to share what you know!

    p.s. reading every thread in Schrade sub-forum in it's entirety cause I can't search has to say something about my commitment and yes, you have been very busy filling this sub-forum with gems. People like you, Codger, are precisely why this site is worth paying for. I hope Spark thanks you (and maybe gives you a "cut") too!
     
    Last edited: Nov 6, 2009
  13. Dave Thinkstoomuch

    Dave Thinkstoomuch Banned BANNED

    Jun 15, 2009
    Ok...so he does accept PayPal now. I just checked again and found it. I will put my money where my mouth is shortly. Fair is fair... Cheers! :)
     
  14. Codger_64

    Codger_64 Moderator Moderator

    Oct 8, 2004
    I certainly don't get a "cut", but several members here did take pity on me in my current financial circumstances ( :eek: ) and bought me my curent membership upgrade when my GOLD expired. Thank you once again gents!

    Michael :)
     
  15. know what i mean

    know what i mean

    194
    Oct 4, 2007
    Interesting article Codger. Your research and contribution to the forum has answered more than a few questions I've had come up. Thank you. Dale
     
  16. Dave Thinkstoomuch

    Dave Thinkstoomuch Banned BANNED

    Jun 15, 2009
    Nice! I like kindness and money's not everything. Stay proud and keep your chin up Codger. Well done gentleman! Codger's help is invaluable!
     
  17. Larry303

    Larry303

    Jul 28, 2005
    ...bumped up for Pygy....so he doesnt get an inferiority complex regarding his Delrin question...I found it nearly interesting mate...Hoo Roo
     
  18. Jamo

    Jamo

    205
    Aug 24, 2009
    Codge must still have sore fingers .
     
  19. Pygmalion

    Pygmalion

    987
    Oct 7, 2007
    Thanks, Larry303. I don't feel quite as inept as I did.
     
  20. Jamo

    Jamo

    205
    Aug 24, 2009
    He's just sucking up as UL or one of his mates has the the
    .... 2....................................O...........Teeeeeee
     

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