Using a hot knife with poly flag material

[Dede]

A little off topic here...

Our high school band received a generous anonymous donation, and I suggested using some of it to purchase a hot knife.  This would allow us to produce more professional-looking color guard flags than we have made previously.

I have never used a hot knife, and since I opened my big mouth... researching hot knives and learning how to use one is now MY job. HELP!

Fabric is "China Silk" (lightweight poly flag material, basically garment lining fabric).  Would we want this kind of knife, with a rod instead of a blade?



What do you use for a cutting surface?  Would a blade cut/melt cleanly through such thin fabric, or would the fabric bunch up in front of the blade?  Is it safe or wise to cut through several layers at once?

Trying to imagine every possible issue, but I don't even know what I don't know, so... ?


EDIT:  I originally said "nylon" -- fabric is actually POLYESTER.

[bobbin]

I have, use, and love an Engel hot knife.  Mine has the foot guard on it and I leave it in place when cutting.  I use it all the time on acrylics (marine and awning weight, also upholstery weight).  I have used it cut polyester fabrics of similar weight.  I think the Engel might be too much for banner weight nylon, though (and they're expensive). 

If you are willing to work on a metal surface I bet you could use one of the cheaper hot blades sailmakers use.  The Hot Tool Knife in the Bainbridge catalogue is about $65 and I've used them before; mostly to clean up threads and cut webbings/bindings/etc., and they work well.  Ungar also makes one that's probably nicer (looks to be about $80 at Bainbridge), but I've never used one.  Neither of these have a switch that allows you to control the heat, so you have to pay attention and you have to have a safe way to set it aside as you move the fabric around!

[Dede]

Fantastic information... thanks so much!  I will definitely explore the knives you mentioned.

Neither of these have a switch that allows you to control the heat, so you have to pay attention and you have to have a safe way to set it aside as you move the fabric around!

Are you saying neither has a thermostat?

Fabric used for color guard flags is actually lighter than banner weight nylon.  Lame' is often used as an accent color -- that's how light it is.

[Dede]

I just found the hot knife of my dreams... *sigh*  It's cutting what appears to be a very lightweight material here:

www.youtube.com/watch?v=N4kJMG0BxOQ

I will call Engel tomorrow for more information on the blade.  Maybe we can use it on a cheaper hand-held unit.



Edited to add... sadly, the "delicate materials" blade in the video is not interchangeable with any other unit and is way out of our price range.

[Allan]

Maybe a thermostat controlled soldering iron will work?

Allan

[Dede]

Maybe a thermostat controlled soldering iron will work?

Thank you, Allan -- good idea.  I will explore that as well!

[bobbin]

I can't speak to whether or not the Ungar or the Hot Tool have thermostats; probably they do but there is no switching mechanism to turn the heat on or off.  In the case of those knives they're likely always "on" and the top end of temperature is the shut off point.  

I like what I see on the linked promotional video.  But Engel is not likely to make that tip compatible with anything other than an Engel product.  I only hope it's compatible with the base of the hot knife I presently own!

[Mojo]

You might want to check our Harbor freight if your looking for a cheapie hot knife. They sell one for around $ 20 and is used in crafts, etc. It will cut acrylic fabric but not very well. It works good on lighter materials though.

It has a blue handle and a long blade. Check that model out.

Chris

[Dede]

You might want to check our Harbor freight if your looking for a cheapie hot knife. They sell one for around $ 20 and is used in crafts, etc. It will cut acrylic fabric but not very well. It works good on lighter materials though.

It has a blue handle and a long blade. Check that model out.

Thanks, Chris -- I'll check it out!

[Dede]

Well... talked to Engel today!  Very informative conversation.  For $203.05 we can get a nice hand-held unit, a blade for curves, a blade for straight edges, plastic carrying case, and a brass wire brush.  Not as nice as the table top unit in the video, but very serviceable.

Presenting Engel's advice, plus all the information offered here, to our band director today.  Thanks so much!

[gscmarine]

Try cutting on a piece of glass. Works well for sailcloth and nylon spinnaker fabrics.

[Dede]

Try cutting on a piece of glass. Works well for sailcloth and nylon spinnaker fabrics.

Excellent advice!  Engel also recommends cutting on glass.  My only question is... where does one obtain a piece of glass big enough for a spinnaker, let alone a color guard flag?  And where the heck do you store such a big piece of glass?

[gscmarine]

I just have a 3'x2' thick piece from an old glass desk. Just have to move it each time you need to move along the cut but no big deal. Check with a local glass and mirror shop for any old and or broken jobs, could pick something up for short money.

[Dede]

Just have to move it each time you need to move along the cut but no big deal.

Never actually thought of moving it around...  I will definitely check with a few local shops for scraps -- thanks!

[Dede]

Update!  Director left the decision up to me, and I chose the Engel.  FANTASTIC customer service, by the way.

Here's the unit:


Here are the blades I ordered with it:


The first blade is meant for curves, but the unit weighs two lbs and holding it with this blade is awkward.  Second blade is for straight cuts -- seems to work okay, but I haven't yet tried it with a straight edge (should be fine).  It can not be used upside-down because only the edge gets hot, not the point.


Ordered a couple of new blades to try for curves:


These are the "best" blades for curves that will fit in the hand-held unit, and the second one can be used upside-down if necessary.  They should arrive this week.

We have a gorgeous piece of donated glass that was mis-cut for a coffee table.  Score!