Material suggestions needed

[Maplehead]

Hi All
I need to find a 1/4” sheet of material that is not metal, is an electrical insulator, will not melt while being routed on the CNC and can hold the form of threads to very small tapped holes, (slightly smaller than a 1/16”). Currently, I’m using acrylic but the plastic just keeps melting and building up around the bit, (yes, have changed speeds and feeds), and the threads easily break.
Any and all replies are greatly appreciated.

 

[PNW_Guy]

Have you tried Delrin?

It machines beautifully, and is an insulator - at least with the voltages I use.

 

[RJSakowski]

Phenolic materials, e.g. Bakelite, Garolite, etc. won't melt. It is commonly use as an electrical insulator. https://www.mcmaster.com/products/plastics/garolite~/

I machined acrylic without melting using flood coolant without any melting. I found a carbide router bit gave a superior finish vs. a carbide end mill. There is a significant difference between cast acrylic and extruded acrylic. Cast is more machinable.

 

[GeneT45]

Definitely Delrin (acetal) - nothing is going to be easier to machine, it won't melt, and it's insulative. At least some of the Bakelite/Garolite materials will ruin anything but a carbide cutter.

GsT

 

[benmychree]

I agree with RJ, phenolic is best for many high temp electrical applications.

 

[mksj]

I also use phenolic sheet for control boards, easy to machine, cut and tap with high strength. I prefer to work with the electrical grade linen reinforced brown Phenolic CE or LE, a bit cleaner to work with then the glass fiber impregnated, they have many types as to strength, temperature working range and insulating properties. Also check eBay. I power tap the holes after drilling the tap holes on the mill. I do not use acrylic plastic for anything, it is too brittle and prone to cracking with any stress.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

[Ultradog MN]

I don't know about its heat or electrical properties but delrin is the coolest stuff you will ever get to machine.
A couple of years ago I made a pair of bushings for the steering column on my tractor.
Original bearings were like cheesy bicycle bearings and had disintegrated due to rust and the lack of a way to lube them.
New ones were NLA.
I had machined some delrin when I was at the U 40+ years ago and liked its properties. It was brown colored. Dunno what the difference in color is.
It's definately a fun material to machine.

 

[Maplehead]

Ok, for Delrin vs. Phenolic, which one would be better suited for tapping and holding small threads, (like slightly smaller than #4 x 40)?

 

[Maplehead]

Ok, for Delrin vs. Phenolic, which one would be better suited for tapping and holding small threads, (like slightly smaller than #4 x 40)?

I’m leaning towards Delrin as I think the fibers in Phenolin could pose a problem tapping small holes.
The material will be used for the bottom plate for my guitar pickups. So they’re not really doing anything or under any stresses. However, they need to not be conductive, check on that, needs to hold tiny threads well, seems to be a check on that for Delrin, and I don’t want it melting and forming onto the end mill while cnc routing. lastly, I “pot” the pickups, meaning I put them into a pot of hot bees wax for fifteen minutes so that the wax infiltrates and fills up the spaces of the copper wiring. The temp of the wax is 150 F. Will Delrin hold up to that? The below is a copy from the Web. Looks like I may be borderline.
For elevated temperatures, Delrin® retains excellent strength at temperatures as high as 200° F with a tensile strength of 2,000 psi and flexural modulus at 180,000. Delrin®'s upper service temperatures are 180° F in open air and 150° F in water and can withstand brief temperature peaks of 250° F.

 

[Larry$]

To route Acrylic (cast prefered) use an O flute bit. Maintain proper chip load.
Best plastic for small threads?? Acetel machines beautifully but is relatively soft. I've threaded phenolic materials that worked well but never very small threads. It is quite hard so it seems like a good candidate.