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darryl
03-05-2011, 08:53 PM
I needed a strip of rubber today, and a piece of belting I had laying around caught my eye. I cut off a length to suit, then sawed the length into the width I needed, then- I sawed from both edges to take it down from 5/8 to 3/16 thickness. All sawing done on the table saw with the 'all purpose' carbide disposable blade. Now my shop is full of rubber smoke. It's starting to migrate upstairs. Just wondering what I should get up to for a while as it dissipates? Wash my vehicle- go for coffee (just did that)- perhaps clean up the yard- play on the computer

The smell isn't so bad although a bit pungent, but I don't want to stand around breathing it. Maybe it's time to install a large vent fan for times like this, along with a fresh air intake. I'm wondering if the smoke will settle out as dust, or if it will remain in the air even if the air clears-

I have some grinding to do on the rubber afterwards, so I'll be raising more stink, but probably not as much smoke as the sawing generated.

I would have just bought a piece of rubber if I could have found it. Inner tubes, etc are too thin, and the closest thing I did find was a rim liner from a truck wheel. I would have had to shave that down in thickness as well, so I think I chose the best option as the belting material was rigid enough to allow the sawing. Anyone else as crazy as me when it comes to machining rubber?

Reflecting back, I'm wondering if a slippery coating on the sides of the blade would have helped- I'd say probably would have, and probably a new blade would have been better also. This is another class of cutting altogether as the material wants to close up around the blade as you go- at least with belting you have some dimensional stability in it because of the carcas.

Well I need to get outside now, for some fresh air.

doctor demo
03-05-2011, 09:20 PM
Any time I cut rubber belting I use a sharp knife.

Steve

randyc
03-05-2011, 10:05 PM
...or a slower-speed tool like a bandsaw.

Brucey
03-06-2011, 12:33 AM
A quick way is to grab a bosch jig saw blade do a search for a T313AW blade i think that the american term is a sabre saw ? :confused:

Link to a piccy http://www.justtools.com.au/prod133.htm

Spray the rubber with soapy water as you cut, and peel the cut part away watch out it cuts quick :D

When it comes to grinding use the coarsest grit wheel you can you will need to watch out and use a heavy duty vaccum to get rid off the smoke / grindings please clean up well before you use the set up agian for steel / alloy as it will set fire to the remains.

To grind accurately you will need to support the rubber with crush plates or if playing with tube use hairspray as a low tack mount agent on a mandrel

Sing out if you need any more tips i work in the rubber industry

Good luck with it mate

Bruce

darryl
03-06-2011, 02:49 AM
Bruce, I just got the tip about soapy water as I was out for a beer to get away from the stink. Next time I'm cutting rubber I'll try that. I've wondered about the saw blade as well- more teeth or less teeth?

I actually don't recall whether I've tried the sabre saw routine, but maybe it's time to try that.

The first piece I cut I used a knife, but that wasn't belting. Last time I cut this material was with a skil saw, outside.

I'm attempting to make a v-ribbed flat belt, which needs to be of a size that I haven't found a source for. No matter that- I've made belts before, and the only difference in this case is that I'll need to grind the v grooves after the carcass has been laminated to the rubber ring. At this point I have the loop glued together using plasti-dip. I'm hoping it will hold together well enough while I grind the loop to an even thickness. I'm going to use shoe goo to layer on one thickness of fiberglass cloth as a bias ply, then wind on a flat layer of dacron, getting it impregnated with shoo goo as best I can. Once I have a cover coat over the dacron I'll grind that smooth, then invert the belt and grind the grooves. I'm thinking I'll use naptha to help keep the shoo goo from skinning over until the fiberglass strip and the dacron have been applied, then allow that to flash off and apply the final layer of shoo goo fairly quickly so it will bond all around.

My main concern is that because the shoo goo has a solvent in it, it will shrink as it cures. Same goes for the plasti-dip. It may or may not be a problem, but I guess I'll find out. The belts I've made previously haven't come apart, but they also are much narrower than this one will be. By the way, for those I used non-waxed dental floss for the circumferencial winding, and plasti-dip throughout for the carcass binder.

My preference for the whole belt project is to use UV curable urethane rubber, but at more than $600 a gallon I'll have to get a bit creative to secure a smaller quantity of it. For now I'll do it as said above.

Brucey
03-06-2011, 08:33 PM
Hi there Darryl

Cutting rubber is a no teeth is better option mate look here for the blades that are used there are no teeth http://www.caknife.com/industry/14/Rubber-and-Tire-Cutting-Knives-and-Blades.aspx also the piccy of the blade for bosh sabre saw is a no teeth blade its a knife blade with indents the closest way to describe it is a bread knife.

Man oh man i hope for your lungs that you have good ventilation my friend with that chemical mix have you considered Lord 252X it dosent cost that much or the old standby sickaflex

Bruce

darryl
03-06-2011, 09:04 PM
I have used sikaflex and found it good, although once opened the tube cured up pretty quickly. I don't recall now- does it cure by moisture absorption or by evaporation of a solvent- The 252x reads pretty much like the plasti-dip according to the msds. Similar solvents in any case. The plasti-dip gluing I did last night to bond the ends of the rubber strip, making it a band, seems to be holding well. Now I find that my tp grinder won't cover the full width of the belt at the diameter of the form, which being 8 3/4 inches is right at the full capacity of my lathe. That's swing over the bed, which means the carriage is in the way and I can't grind the full width of the belt, only about half of it. So here we go again, 'nuther little project to help out the previous one, which helps out the previous one, etc. What was the initial project anyway- :)

Got the place aired out and can't smell the fumage anymore, so that's good. I can't wait for it to be warmer so I can run the vent fan and refresh the entire household full of air. One thing I do have, and it's good, is a floor level pickup vent to extract any gasses that might be lingering that are heavier than air. I run that from time to time, and it does make a difference. Who knows what all might be lurking at basement floor level-

So now, with todays chores out of the way, I'm back into the shop to see about extending the arbor on the tp grinder.

Gary Heath
03-06-2011, 11:41 PM
A few years ago I read an article about machining rubber.
The author froze it first, then then was able to machine it like you would nylon/delrin, without the burning and smell.
I think it was in The Home Shop Machinist, or Machinist's Workshop etc.
I haven't had the need to try it myself, but the method stuck, and I'll give it a shot that way if I find myself needing to machine some rubber.

Best regards,

Gary

darryl
03-07-2011, 02:00 AM
Freezing rubber to machine it can work, but it depends on the particular compound. Urethane stays flexible to a much lower temperature, so you'd have a hard time with that.

From this point on, burning and smell will be the least of my worries. I just got finished preparing the tp grinder to handle the large diameter of the form needed to hold the belt for grinding. I thought initially I'd have to lengthen the arbor, but then I thought why not move the mount over instead. So I made a new mount to let the grinder hang further back and more to the left. I now have enough room to be able to do the job, with about 1/4 inch to spare.

This will be the first time I've had to use the maximum swing capacity of this lathe. When the final coat of rubber is applied over the dacron fiber layer, it will clear the rear way by about 1/16 of an inch. That's cutting it pretty close. I'll post some pictures when I get to actually start truing up the rubber. Should get to that point later this year :) Seems like all I'm doing is modifying equipment so it can handle the job- but I only have one more 'jig' to make before I can start that part. I need to make an MT3 insert for the spindle that will have a 1/4 inch diameter stub on it- this will be used to center the form that holds the belt for machining. The form will be screwed to a faceplate, but especially when I go to make a second belt, the form will have to re-center perfectly since I will not be able to remove material from the circumference to re-true it. Pictures will explain everything once I actually get the prep work done.