Is hot knife cutting a hazard?

[baileyuph]

I had to do some awning work and this question crossed my mine because there was an article or discussion not long ago I read about this same subject.

Yes, it was sunbrella.  Being in doubt and i had an option on this job, I  bound the edges and it worked out that I didn't use a hot knife. 

Moreover, is the hot knife still the cutter of choice and is there any reasonable concern about dangerous fumes?

Doyle

[Gregg @ Keystone Sewing]

I'll wait to see other responses, but I don't think you would need 'seal' the edges where binding is being applied.  Most like to use the Engel SHG-0 cutter we sell (I've had people not know we sell this item) seems to be the cutter of choice.  About the fumes...I have no idea, and no MSDS about cutting synthetics like a Sunbrealla, but I do know it's a common practice to both cut with a hot iron like you are asking about and to heat weld this material as well. 

[scarab29]

It's not like your burning plastic , well it is but not like a fire. If i'm doing a lot of cutting I turn on my little tabletop fan to keep the fumes out of my nose. I work in my basement so it's not all that well ventilated. Open warehouse i'd think you would have better venting and more air moving around and be better.

[Mike8560]

I read once that there was formqldihyde in sunbrella
I used to justmelt my zippers to make stops a d the smoke used to really burn my nose mow I make a loop
with binding.  I dTNT kni if there is any danger.
I knew a guy who comained about the dust tha used to come off the thread and clog the machine
he spent years making dump truck cover and had breathing problems when he retired. 

[Grebo]

 formqldihyde ?   :D   Go on Mike, have another go  ;D

[Miami Mike]

I read once that there was formqldihyde in sunbrella
I used to justmelt my zippers to make stops a d the smoke used to really burn my nose mow I make a loop
with binding.  I dTNT kni if there is any danger.
I knew a guy who comained about the dust tha used to come off the thread and clog the machine
he spent years making dump truck cover and had breathing problems when he retired. 

:-\ :-\  Formaldehyde is in the Finish of all Acrylics. And I understand that it's not good to breath the smoke when your cutting with a hot knife.  Make sure you do have air flow.  Acrylic fibers are fine, it's the finish that is bad. The coating that gives the water repellant.  :o

[fragged8]

cutting zippers with a hot knife is tricky, I generally blow the smoke away while cutting
otherwise it will make you choke and also make your eyes water a bit like CS gas.

It is Delrin a plastic i used to mold when i worked in plastics,  or also known
as Acetal Resin. If not handled correctly when injection moulding you can gas out a whole
factory. you don't need to know how i know this :-)

basically avoid it when you can. cutting acrylic with a hot knife isn't
necessary when binding but can be useful to cut the waste from a dart
as it stops the weave shifting like it does with a cut edge.

Rich

[Mike8560]

I forgot to say. I don't cut mt sunbrella much with a hotknife when I do a cockpit cover my center seam is generally blid stitched with binding on the inside I find it more waterproof and n thread is exposed.

On a large top I'll just cut with sissors and  i bind the isdide of mt seams before topstitching
I find cutting with sissors much faster to me it offsets the cost of the binding.
When I mted zippers to
make a stop somtime it woud  flame up if I wasn't w
carefully  it was dagerous

[DBR1957]

Almost always use a hot knife on Sunbrella, Coastguard and the like. I've repaired too many covers, even with bound edges, where the scissor cut edge frays, binding pulls off, etc.. There are times when it is not necessary though. Test for your self. Cut some scrap, 2 pieces with scissors, 2 pieces with hot knife. Sew the scissor cut together with binding and likewise with the hot knife cut. Pull on the edge of each and see what happens. Keep in mind your customer will be pulling on it much more than you will.

Best way to use a hot knife is to cover your table top with luann board and sand and finish with a sealer. Make it smooth! Take the foot off the hot knife if it came with one. Cut through the fabric on the luann table top. As the residue builds up on the blade file a new edge. The luann table top is also great to push pins into for holding materials for patterning, etc.  

I bind the center seam on bimini tops for looks. Keep in mind that I'm binding the factory edge that is laser cut anyway. But it's still top stitched. On cockpit covers I start with blanks double blind stitched along the factory seam.

I never burn a zipper to make a stop. Used to do the binding wrap technique. Now I just use the SS stops. So much easier. YKK even makes a top stop now that you push on the last tooth and twist. Haven't tried those yet.    

[bobbin]

I am definitely "dead meat". 

[206RB]

I've started, but never finished some research on this subject.
Seems to me there is nothing good for you from breathing the fumes. Add to that the fumes that are put off from the wood underneath. Add to that the fumes that are put off from all the glue and other build up which accumulate on top of that.
Call your local OSHA rep and they will get to the bottom of it...

[Mike8560]

i tried the SS stop and the crimp tool i found it somthing esle to buy and another process ive alway got the binding handy. plus at the time they onluy fit # 10 zippers and i used allot of #8

[DBR1957]

I've started, but never finished some research on this subject.
Seems to me there is nothing good for you from breathing the fumes. Add to that the fumes that are put off from the wood underneath. Add to that the fumes that are put off from all the glue and other build up which accumulate on top of that.
Call your local OSHA rep and they will get to the bottom of it...

Like others have said on the fumes, ventilate. That's a given. If you keep the blade with
a nice edge and don't hold it in one spot you will greatly minimize any smoke/fumes. Also,
cutting is such small part of the job. Bad knees from climbing up and down, Carpal tunnel
from cutting, gripping, pulling. Back ache from carrying rolls of material, vinyl, drums of
Strataglass. Then coughing, sneezing and sinus headaches from the dust, pollen and
mildew on boats and covers. Answering the same questions over and over again for the
same customer. BS sales calls constantly after you've asked to be on the "Do not call" list.
Believe me the fumes are the least of my worries.

OSHA? Came into a neighboring shop one day. Small boat repair shop. Made them throw
out their chemical masks. Didn't tell them they had to use them. Only that if they were to
use them then each user had to be fitted and certified to use one and the shop supervisor
had to take a certification course. That course cost roughly $10,000.00. I think they stopped
doing the work requiring the masks. The $10,000.00 would have eaten up any profit margin
for a few years.

[fragged8]

Mike, sewing a fabric stop onto the zippers while you are sewing the zipper in
is common practice here, it's been done that way for years and as most people
here don't have access to the fancy stops its the easiest too.

or sometimes i finish zippers like this.


Rich