Need tooling advice, long undercut

Tap_or_Die · Jul 30, 2019

I need any advice on an existing tool or the possibility of making a tool to do the undercuts in the picture. This will also be rubber material that we have been cutting so the tool will need to be extremely sharp.

P.S. An insert style tool would be needed also, rubber is abrasive....

BoxcarPete · Jul 30, 2019

1. "Rubber" means a lot of different stuff. If you are more specific, it might help your case.

2. You're cutting that, not molding it? Hmm, might be possible if you form everything else before going in for the undercuts. IF it's overmolded to the can, and not assembled.

That said, if you absolutely must cut the profile, get it cold. Depending on the actual compound you are using, "cold" will be a different temperature.

Edit to add: You might consider going in with a razor blade (or similar) to separate the "arm" from the bulk. Looks like you have the clearance for it. Then, it'll be much easier to go in and clear out the rest of the material.

Tap_or_Die · Jul 30, 2019

Its 85 duro, probably epdm, or viton, Customer hasnt told us what compound. We have had great results with a VCGX sandvik insert with out cooling the rubber. That being said. I was hoping to clearance the arm like you have it drawn, then plunge with a radius style insert like RCGX sandvik or similar but smaller. I could plunge the angle then turn the o.d.

Tap_or_Die · Jul 30, 2019

Who makes the smallest round uncoated inserts?

4GSR · Jul 30, 2019

That looks like the profile of a wiper plug. Nitrile or Buna-N at the most. Just saying. Freeze it with CO2. Fix up a cooler with CO2 ice, if it's big enough for your part. Ken.

BoxcarPete · Jul 31, 2019

EPDM and NBR/Nitrile are close in cost, so "at the most" would only eliminate FKM/Viton from the discussion. 85 durometer is pretty hard for EP though, so at this point it's anyone's guess?

If you know the fluid media it will be in contact with I could make a better guess. A dry ice cooler would likely get FKM too cold, it gets brittle (i.e. fractures rather than bends) anywhere from -10°C to -20°C unless it is a special-grade low temp FKM for automotive use.

thunderskunk · Jul 31, 2019

Tap_or_Die said:
View attachment 262221

... engineers are assholes.

I’m sure he or she had their reasons, but I bet there was some small way they could have made things just a bit easier.

BoxcarPete · Jul 31, 2019

thunderskunk said:
... engineers are assholes.

I’m sure he or she had their reasons, but I bet there was some small way they could have made things just a bit easier.

At least there are no tolerances listed on that un-measurable part

CAMasochism · Jul 31, 2019

BoxcarPete said:
At least there are no tolerances listed on that un-measurable part

Used to have an engineer that worked for us, on a few of his parts I would bring them to him and ask him how to check his dimensions to which his normal answer was, "I'm not sure/I don't know" at which point I would have him change it to something that could be measured. Of course he also hadn't touched a mic or caliper before he came to work at our company after getting out of school and getting his "holier than thou" diploma.

Tap_or_Die · Jul 31, 2019

So this is a r and d deal im sure. The part will most likely be molded after the design is finalized. This company has been using us for down hole application to prototype different seals or plugs. Seems its cheaper to have us machine the rubber and test it vs getting a 10k mold only for the mold to be revised after a few parts. As I said before we have had extremely good results turning this material before, so im not to worried about the machine-ability. Just need to find a sharp/small/round insert, something with a IC of .125 or smaller. I can make a tool holder to do the job after that.

4GSR · Jul 31, 2019

Dad used to grind HSS to the right radius for stuff like this. One time use, may be the way to go. You may be able to take a larger top notch insert with the right radius and make a holder to hold the insert with a home made clamp that would attach and hold the insert from the back instead of the side. Look at Tool-Flo's website and go thru all of their catalogs and see if something there will work. Ken

4GSR · Jul 31, 2019

thunderskunk said:
... engineers are assholes.

I’m sure he or she had their reasons, but I bet there was some small way they could have made things just a bit easier.

NOPE!!! It has to be designed this way to serve the purpose needed in application. Engineers can be assholes, I'm one, but I have 40 plus years in the machine shop, and know what to do and not to do in designing something that has to be machined. Might become difficult to some machinists to make but manageable. I look at it this way, if I can't make it in my shop, the design doesn't leave the office, period!

What the OP is showing us is common stuff, may be specialized in his case, the oilfield uses daily and has been for nearly 100 years. Most shops down here have no issue machining this. I don't either. Ken

Tap_or_Die · Jul 31, 2019

4GSR said:
Dad used to grind HSS to the right radius for stuff like this. One time use, may be the way to go. You may be able to take a larger top notch insert with the right radius and make a holder to hold the insert with a home made clamp that would attach and hold the insert from the back instead of the side. Look at Tool-Flo's website and go thru all of their catalogs and see if something there will work. Ken

Ive tried HSS on this before and it will dull in 1 pass. Inserts last about 30-40 times longer.

Philabuster · Jul 31, 2019

Just because the engineer could draw it, doesn't mean I can actually make it. :rolleyes5:

I have to say that about once a week to the noobie engineers.

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