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Vacuum molded Horizontal/Vertical Sheath

Discussion in 'Sheaths & Such' started by HallHandmade, Jan 22, 2014.

  1. HallHandmade


    Jun 5, 2012
    This is my first post here. I used to do leatherwork as a hobby when I was younger, but just started again a couple months ago, and have been using vacuum molding this time around. I'm getting it dialed in enough that I thought I'd share. I'm primarily a knifemaker. Most of the sheaths I make are for my own knives, although I have done a couple commissions.

    I don't claim to be an expert leatherworker, far from it. I think I do get reasonable results, and the customers seem very happy.

    I've switched over almost exclusively to vacuum molding for my sheaths. Now that I have it dialed, the fit is amazing. The retention is good enough that in most cases I can hold the sheath upside down and shake it hard without the knife moving, yet the knife goes in and out smoothly and easily.

    I also prefer vacuum molding because you don't have to fool with the leather very much, so it preserves the natural grain much better than hand molding IMO.

    First I start by wrapping the knife in tape to protect it (this needs to be removed IMMEDIATELY after molding, or you may forget and have trouble brewing). I affix it to a few thicknesses of cardboard using the butyl rubber seen at bottom. This is also used to seal the vacuum bags.

    Why cardboard? You want something stiff, but not too strong. Vacuum can apply a good deal of force, and if the knife was being molded on a piece of steel, for example, it's conceivable you could damage the knife. Plus, the knife sinks in a tiny bit, which adds some pre-load so it has a snug fit once the sheath is assembled.

    I make spacers out of wood to make sure the mold allows clean entry/exit for the guard and blade. I also put a spacer under the blade so it has a bit of extra room (some of which will disappear).

    Next I cut an appropriate sized piece of leather. This is not a good place to try and cut it close. You don't want the piece to be huge, either, as it will be harder for the leather to move.

    I heat some water to almost boiling, then let it cool for a bit. You want the water to be nice and hot, but a good bit below boiling. Pre-soak the leather for a couple minutes before this in room temp water, to give it a head start.

    You want to soak the leather in the not-boiling water until it starts to curl a bit and starts to have a soft, flexible, almost slimy feel to it. If you see the color change on the edges you were too hot, or too long. Pat dry with paper towels.

    Sometimes it helps to curl the edges up, this gives you a better "corner" where the mold goes flat. You want to gently mold the leather to get it started. Don't go poking it with your fingers a bunch though. :)

    After that, I apply a layer of soft foam to distribute the force of the vacuum bag, this prevents wrinkles and overmolded areas. I add a couple strips of tape on the edges to hold everything in place. You don't want the tape to go all the way across the foam, or else it won't stretch right.

    This is what a very basic vacuum setup looks like. This is two Ziploc freezer bags taped together, using butyl to seal each end, and the hose. I'm using a basic refrigeration vacuum pump.

    I taped a small piece of fabric over the hose end so it doesn't suck in the bag and rip it. It's okay to have some small leaks... you don't really need to pull a hard vacuum on this.

    You can help it out a bit when first pulling the vacuum, holding the leather in place and pressing gently around the knife to help it mold better.

    You want to leave the knife under vac until you feel that it doesn't have anywhere else to mold to, and you see the leather start to change color just a bit, this means it has started to evacuate the excess moisture. This shouldn't take forever, a few minutes, sometimes a bit longer.

    If you're lucky, you'll get something like this (I still don't get it perfect every time). I normally like to use a couple layers of finer cardboard on top so not to get the lines as seen on this one, but they don't really hurt in the end.

    Let dry until fully returned to original color.

    secret trick: Using some gentle heat to accelerate the drying hardens the leather, which will help it keep the form of the knife, and keep good retention for longer. Just be careful. If you dry too fast you will make it brittle. super secret trick: If you use a heat gun on low to give the area around the guard a head start, it will be a bit harder there, which will help with retention of, um, retention.

    Ok, so skipped a couple steps here, but nothing that probably needs to be shown. Basically I trimmed the molded piece about 1/2" around the whole edge, and dyed it black.

    Then I cut another piece and dyed it black for the back piece, plus a thinner black leather liner piece that I skived down to zero taper and glued to the back.

    Next I glued the pieces together with contact adhesive, and after the adhesive was fully dry, I trimmed with a knife.

    The back.

    The sander is my favorite way to trim and even the edges, but you have to get the hang of it to get a good result. Make sure to use proper grits and speeds, you don't want to burn the leather. You should get a nice clean look as in this photo.

    After dying the edges. If you burn the leather when sanding, then you will get uneven dye absorption. This can be somewhat mitigated by using edge paint instead of dye.

    Next I cut the stitch groove. This sheath is a bit oddball, as it is black with brown stitching, which normally does not show up well. Because of that, I waited to cut the stitch groove until after dying.

    After rolling out with a stitch marker, I drill the holes using a 1/16" drill, which I find works perfect for standard waxed threads and 16ga needles. Some people prefer not to drill, but it seems to work well for me. It is a personal preference thing, if the piece is designed and constructed well, it doesn't seem to matter that much.

    Hidden step: Sealing the leather, I used Satin-Shene. You can see that it darkened the stitch grooves a bit, which is a good thing in this case.

    I taped the back piece/belt loop in place, it can be seen in the next photo.


    I match drill the holes, using a needle to keep indexed when moving to each new set. Remove the tape ASAP. It's ok to use it real quick to hold something in place, but you definitely don't want to use it on finished leather.

    Here I've started stitching the sheath. I use a saddle stitch. I fill in all of the areas that the back piece is not stitched. That allows it to be easily removable if necessary for change/replacement.

    Here's what it looks like finished. The lighting is terrible, sorry. It looks much nicer in person. The brown stitching actually shows fairly well in natural lighting. As you can tell, I added a second row of stitching at the top, just in case.

    You can see the stitching on the back of the belt piece, since I did it separately, I didn't have to run off the edges, so it is a cleaner look. The hole in the middle allows you to thread the sheath through a belt loop, so it doesn't slide around.
    Last edited: Jan 22, 2014
    Justin.P likes this.
  2. qwt55


    Oct 29, 2013
    Nice job !! Thanks 4 the post.
  3. HallHandmade


    Jun 5, 2012
    Thanks. :)

    Here's another I finished tonight, in brown.


    This is a molded backpocket sheath I did for a BF member.

    This is a pocket sleeve I did for another BF member.

    These two are not stitched yet in this photo, but you get the idea. These are my "standard" horizontal/vertical design. I do them a bit different for small EDCs than I do for the above knife.

    This is the one pictured on the right in the above photo, showing after stitching and smoothing out the stitch lines.
    Justin.P likes this.
  4. Mossyhorn

    Mossyhorn Enlightened Rogue Platinum Member

    Dec 6, 2009
    Those are great looking sheaths.
  5. HallHandmade


    Jun 5, 2012
    Thank you. :)

    I wanted to add, the OP sheath is about as big as I do for a horizontal/vertical, the knife is just over 10.25" OAL with a 5.25" blade. Most this size get a standard vertical sheath, such as the brown one I posted above. I do a whole bunch of the two-way version on my smaller stuff though.

    I've got a long ways to go, but I'm happy with where I'm at. I wanted to make sure I was very solid on my overall technique and dying/finishing of plain sheaths before I introduced tooling and multi-color into the mix. I'm also going to start experimenting with my airbrush for dying and finishing. I'm thinking there could be lots of potential for matching the figure in the handle wood, etc.

    I used to do some medium difficulty tooling when I was doing this as a hobby, but I've never combined it with molding. My eventual goal is to work on getting nice crisp vacuum molds with tooled leather, but it will take some practice for sure. I might need to tool the majority of the pattern, then wait until after molding, and tool the edging in right before drying.

    That's my strategy for continuing to keep the sheaths trimmed right up to the mold edge, but I'm not sure how well it will work in practice. I expect many second and third attempts in the beginning, if it is even possible to do and maintain the level of crispness I want in the tooling.

    I'll check back in tomorrow. I need to hit the sack, tomorrow is a grinding day so I need to be on top of my game. :)
  6. leatherman

    leatherman leathermoderator Moderator Knifemaker / Craftsman / Service Provider

    Nov 30, 2001
    Very nice step by step there! Thanks for taking the time to make it. :)
  7. harronek


    Nov 29, 2013
    Very nice sheaths .
    I am a fan and devotee of the plain simple sheath .
    Someone here said awhile ago something like " Simple is very hard to do "
    To achieve near perfect lines and blemish free finish on the leather is something that is very high on my wish list .
    Interesting idea about the vacuum forming , I actually find the wet molding part of the sheaths production one of the most enjoyable parts , but I can see the benefits of what you are doing .
    Is it possible to crank up the vacuum and get really sharp edges and contours ?

  8. rayban


    Apr 14, 2007
    My thoughts exactly Ken......seems like you can get a lot sharper lines and get closer to the knife if you use your hands to mold.
    And I see no welt is used...makes me wonder how long this design would hold up out in the field.
  9. HallHandmade


    Jun 5, 2012
    I think that maintaining the grain is probably the main reason I'm running with this.

    I love hand molding, but it just does not mix well with my OCD. I end up overworking the leather every time. I need to keep things simple and stupid so my brain does not cause me to run out half a shop day on nothing. :)

    I mold a bit harder than maybe I should, if you wet the leather down to hand molding level, then you should get a very tight fit. Also, if you were to swap out the pad with something more compressible, but you'd need to watch your creasing.

    There something like 500lbs of evenly spread force if at full vac on a mold this size. I think you can press harder hand molding, which is why I like to help it out with my hands. The other people I've found doing this seem to use a similar method.

    I feel like this allows the leather to stretch more evenly and naturally, and the finished, hardened result is more uniform and mechanically stable.

    I also wanted to add, I'm using some fairly heavy leather here. It's at full thickness, which is pretty heavy on this hide. I dream of the day I have a nice splitter. The corners are just huge when running this weight of leather.

    Where this really works its magic is on medium weight leathers, where they are heavy enough to have some stiffness when hardened, but light enought to really soften up when molded.

    As far as the lack of welt, I shared your concern. That is what led me to getting very particular with those little spacer blocks. I try to make a springy channel in the first 1/3 of the sheath, so the knife and blade automatically follow a certain path.

    I've also done this with welt, cut it first and place it around the knife on the fixture board before molding.

    Now that I've got control of my process, I'm getting a very good result imo as far as function. I've read other sheath and holster makers say that the draw feel on a vacuum molded sheath is like nothing else, and I'd have to agree. It holds the knife very tightly without moving, but slides in and out smoothly and with little effort.
  10. HallHandmade


    Jun 5, 2012
    Well, I just got an answer as to how these do under hard use. Customer came by for a resharp last night and I had to snap a photo. I kid you not, when I took the knife out of the sheath, a small rock and some dirt fell out. :D

    Retention still good, and no visible damage from lack of welt.

  11. zachtateknives


    May 4, 2010
    Very nice!
  12. popedandy

    popedandy Gold Member Gold Member

    Dec 8, 2006
    Very nice work, and thanks for the step-by-step.
  13. Diomedes Industries

    Diomedes Industries Gold Member Gold Member

    Mar 19, 2007

    It is cool to see different approaches. I enjoy learning from you - even if something fails - we all learn.

    I wager a lack of welt will be of little issue in thinner knives.

    Keep us up to speed.

  14. i4Marc

    i4Marc KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Oct 19, 2011
    Good stuff Ian. Thanks for sharing. I'll be "borrowing" your technique at some point.
  15. mccandmatt


    Oct 29, 2013
    Thanks for the look into what you do. I like these, and IMO much better than Kydex (Now I have to hide from the Kydex fans :D ). Can't help it, not a Kydex fan at all :foot:
  16. HallHandmade


    Jun 5, 2012
    So far a good rule of thumb has been on any knife where the blade is longer than the handle, but sometimes the shape of the blade/handle too. Smaller knives seem to be held rigidly enough that they don't really move once in the sheath, and if I set the spacers up right, the blade doesn't rub going in either.

    No prob. I don't claim to be an authority on anything, but a customer was curious what I meant by vacuum molded sheath, so I figured it couldn't hurt to post a thread. :)

    I'm not the biggest fan either. I do work in it sometimes (mostly on custom orders for tactical knives). I just think that leather goes so much nicer with my knives, particularly the ones with natural materials.

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