Questions about Machining Neoprene Rubber

wrustle · Sep 27, 2010

Ok, this one has me very cautious. Looking at a job 500-600pcs.

Neoprene Spring Rubbber, nothing critical, in fact wide open tolerances.

1" OD +/-.125" x .530" ID +/-.03" by 2.00" lg. +/-.02"

The OD is a stock size, the ID however (from my limited search) is only available in .375" dia., and .625" dia., thus my question.

McMaster-Carr

Can this material be drilled, and hold some semblence of size? I was even thinking of a 2 flute HSS EM, or a flat bottom .562" drill, thinking that IF it does by some chance cut and not tear, it would shrink back down to somewhere within tolerance on the ID.

Does anyone have ANY experience with this material? I am really hoping for a "been there done that" session, and not just logical advice......no offense intended......but with 500-600 pcs at stake, I HAVE to know what to expect here.

As a side note...........I already "No Quoted" this job to my customer last week. He is now pleading with me to make these parts, as the previous shop has not been answering their phone for a over a week now, and he seems to think they are no longer in business, but needs parts right away.

I have no problem accomodating him, they are afterall a very large account for us, but I also don't want to take a bath on the job because I'm doing a favor.

Best Regards,
Russ

adama · Sep 27, 2010

I have machined rubber not neoprene though soft and harder varieties. For the holes forget normal cutting tools, you want a sharpened smooth tube. Basicaly as thin as you can get it. Coolant if its rubber compatible would help, i used 50% water 50% dish soap. Rotate slowly and feed in gentaly, it will cut out a nice clean slug if properly sharpened. Its at the upper end of stock sizes but you can get Hss paper drill bits that work great in rubber, basicaly a Hss tube with a parrelel end to fit in a paper drill. Go carefull if you go that route as not all paper drills have a parrelel shank. You will have to come up with a way of ejecting the slugs, stsd paper drills are hollow spindle afairs and just spit them out the top. Keep it sharp - but a slightly ragged edge not mirror polished works best for me. You could easly hold that 20 thou tolerance with one, so long as your not distorting the part holding it.

Holding its the challenge. its going to take a firm grip, something collet like might do it, but at a light pressure - large contact area is what you want. Cutting them to length is what i don't know though, that could be more of a issue.

Personaly i think you might do well to find some rubber molders near you and get them to qoute you. Normally they can work of relitifly crude molds and would probaly be cheeper, especialy if your going to be getting this job again!

Fasto · Sep 27, 2010

I have made rubber pieces similar in OD and ID but only 0.5" long from solid. I cut them to length with a shear of some sort and froze them in liquid nitrogen. I then machined both faces and the ID. I used regular HSS tools on a SB heavy 10, a 2-flute EM for the ID. I think it took several trips back to the liquid nitrogen. Once they aren't frozen any more they did not cut well. I did this at least 10+ years ago so sorry about the hazy memory. I also only made about 25 or so.
I dropped 1 or two and they shattered like glass!

steel hand · Sep 27, 2010

+1 on molding. The mold would be simple for this part. We mold a couple of our own rubber products, it's not hard at all.

Toolbert · Sep 27, 2010

Someone with a tilt-head taper-compensating waterjet can cut it out of 2" solid and hold tolerance. Even for waterjet, that's a tricky setup on account of holding onto the finished parts, and they're likely to cost several $ ea, plus the material. But it is an option.

alphonso · Sep 27, 2010

First question, what is the durometer? Anything less than 80 is a royal PITA. You can drill with a thin-wall tube like ADAMA says, but that is pretty slow.

Second question, what is the chemistry? Lots of different Neoprenes out there.

Molding is the way to go. I could make a compression mold for about $250 -$300. My primary business is rubber molds. Want me to ask one of my customers for a firm molding price?

cmailco · Sep 27, 2010

If it's 75A duro like the McMaster Carr stuff you linked, I'd look at building a mold, or outsourcing to a molder. There are a number of 80'ish durometer polyurethane's (if a valid substitute) that you can buy in 24" lengths; 1" OD, 1/2" ID... and most of those suppliers can change the core up easily enough.

Urethane Tubes, Polyurethane Tubes, Cast Urethane, Cast Polyurethane

Metalcutter · Sep 27, 2010

If it lends itself to grinding, that really works much better than you could ever imagine.

Try the thin wall tube first though.

Regards,

Stan-

DMF_TomB · Oct 3, 2010

machining rubber

if rubber is cold it gets harder and usually easier to machine. as was mentioned liquid nitrogen. maybe nitrogen can be kept in coffee thermos (don't put cap on tight or pressure buildup will cause it to explode). dry ice is also usually easier to get and keep in a Styrofoam cooler. only problem is it is solid.

some canned air (freon) when held upside down spray liquid freon and cool object as freon evaporates

motormaker · Oct 4, 2010

Easy source

Rubber "donuts" have been a staple tire material in the model car racing industry for over 40 years. The two most popular methods have been steel rule dies set in concentric circles to stamp from the sheet stock, or, more recently, water jet cutting for smaller runs or off standard sizes.

Try JACO RC racing in N.C. Sorry, I don't have a link in front of me, but I once found them on the net.

The sharpened thinwall tube works for extremely short runs. The .530" (17/32") size is a standard in K & S metal racks found in better hobby shops, usually brass - hence the short tool life.

motormaker · Oct 4, 2010

Contact info

Russ,

Thats JACO Racing Products, Inc.
600 Shenandoah Ave.
Elkton, VA 22827

540 298 - 0446

[email protected]

P.S. - Russ, please update the tale of the late lamented Ikegai.

wrustle · Oct 4, 2010

motormaker said:
Russ,

Thats JACO Racing Products, Inc.
600 Shenandoah Ave.
Elkton, VA 22827

540 298 - 0446

[email protected]

P.S. - Russ, please update the tale of the late lamented Ikegai.

Will do on the Ikegai. Been trying to stay ahead of the curve here in the shop. Just hired a full timer the beginning of last month, and we are just about back on schedule now.....not too mention life is sooo much easier just adding one person.

I found the rubber cut just fine in the turret lathe holding the piece in the collet and using a .562" HSS end mill to drill out the ID to .530" on the print, and it ended up coming in at about .535".

Ran it without coolant, fed it rather quickly by hand.....you know how it is when it just feels right.

The face comes a out little concave when facing it after it's released from the collet, but other than that, the part is perfectly acceptable.

Now I am just waiting to hear from my customer on the order, but I just had to try it my own to see if I could do it first. Won't matter to me if I don't get it either.....the stuff stinks when you cut it, and it makes a friggin' mess!!

Later,
Russ

gorrilla · Oct 4, 2010

wrustle said:
Will do on the Ikegai. Been trying to stay ahead of the curve here in the shop. Just hired a full timer the beginning of last month, and we are just about back on schedule now.....not too mention life is sooo much easier just adding one person.

I found the rubber cut just fine in the turret lathe holding the piece in the collet and using a .562" HSS end mill to drill out the ID to .530" on the print, and it ended up coming in at about .535".

Ran it without coolant, fed it rather quickly by hand.....you know how it is when it just feels right.

The face comes a out little concave when facing it after it's released from the collet, but other than that, the part is perfectly acceptable.

Now I am just waiting to hear from my customer on the order, but I just had to try it my own to see if I could do it first. Won't matter to me if I don't get it either.....the stuff stinks when you cut it, and it makes a friggin' mess!!

Later,
Russ

Yes, I'm sure it is a mess. Try turning a 54" diameter molded part. Fortunately it was a seal molded to a steel ring. Still not fun to hold round. Had to take about 1/8" off the od. PITA!
We used a HSS tool ground in house to a "spoon" shape, VERY positive rake. Only lasted about one part between sharpening. Carbon in the rubber was abrasive as cast iron. Customer didn't do enough of them to justify that big mold rebuild. Toleances were VERY loose, as you've stated on your part, but our part was about 54", as I said in opening line. Rubber comes off in ONE LONG STRING! Turned on a 60" Bullard.

wrustle · Oct 4, 2010

gorrilla said:
Yes, I'm sure it is a mess. Try turning a 54" diameter molded part. Fortunately it was a seal molded to a steel ring. Still not fun to hold round. Had to take about 1/8" off the od. PITA!
We used a HSS tool ground in house to a "spoon" shape, VERY positive rake. Only lasted about one part between sharpening. Carbon in the rubber was abrasive as cast iron. Customer didn't do enough of them to justify that big mold rebuild. Toleances were VERY loose, as you've stated on your part, but our part was about 54", as I said in opening line. Rubber comes off in ONE LONG STRING! Turned on a 60" Bullard.

Damn.....that is a big part. I couldn't imagine working anything that large. In my shop, if it doesn't fit in your hand.....it's a large part!!

alphonso · Oct 5, 2010

gorrilla said:
Yes, I'm sure it is a mess. Try turning a 54" diameter molded part. Fortunately it was a seal molded to a steel ring. Still not fun to hold round. Had to take about 1/8" off the od. PITA!
We used a HSS tool ground in house to a "spoon" shape, VERY positive rake. Only lasted about one part between sharpening. Carbon in the rubber was abrasive as cast iron. Customer didn't do enough of them to justify that big mold rebuild. Toleances were VERY loose, as you've stated on your part, but our part was about 54", as I said in opening line. Rubber comes off in ONE LONG STRING! Turned on a 60" Bullard.

And we still do batches of 3 or 4 about 6 times a year. Extra fun when the steel ring isn't round.

Steve Seebold · Oct 5, 2010

Freeze it in liquid nitrogen and it cuts like aluminum.

USMCPOP · Oct 5, 2010

If you do need to cool it off some, dry ice in Acetone is worth a try.

evansmachine · Oct 5, 2010

wrustle, are you really making these for $2 each? :skep:

wrustle · Oct 5, 2010

evansmachine said:
wrustle, are you really making these for $2 each?

Ok....now you've got me wondering, when did I say they were $2/ea.? :confused:

I know I'm getting old, but I just reread my posts twice, and I don't see any mention of price. Am I losing it? :nutter:

motormaker · Oct 5, 2010

Russ, you didn't... but:

Russ,

If you can get me $2 ea. + shipping, and advance enough for the material (yield from 2" sheet approx. 80/sq. ft.) I would happily make them for you.

After paying for the material, I would make myself $60/hr. using nothing more than a Chinese mill/drill and some brass tube, stainless pipe, and my hobby lathe.

+/- .125" inches ROFLMAO!

To think I hold .0001 concentricity on my commutators and .001 on bore dias. through ceramic magnet material routinely and make half that much makes me want to just scream how unfair life is!

Dead serious - PM me if that sounds interesting.

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