Diamond Knurling Specification

[jmarkus]

I am designing a press fit bushing to fit into a nylon part. The bushing is actually a compression limiter so that a bolt can be torqued down over the part (and not compress the nylon). I have specified a medium diamond knurl pattern, based on seeing similar press-in inserts, but I don't really know what is the appropriate knurling detail (size, TPI, spec?) to use. We are going to make a prototype and try it, but I want to start with something reasonable. What should I specify so my machinist can make a good part?

Thanks,
Jeff

 

[BillPSU]

You need to specify by teeth per inch or circular pitch. ANSI B94.6-1984 established perferred sizes. I'm para-phrasing the information from the Tool and Manufacturing Engineers Handbook. The Machinery Handbook also has a section on knurling. It gives formulas for knurling.

 

[jmarkus]

I don't have access to the ANSI standard. Is there an online reference that tells me how many TPI for a "medium diamond knurl"? Anyway I can verify, before I make the part, if that number of TPI will give me a good press fit into a nylon part?

Thanks,
Jeff

 

[BillPSU]

Get a Machinery handbook and review the information. The actual size of the part and the expansion will have to be found by experimentation.

 

[unclesyd]

I think you would be better off if you bought the compression limiter. They are very reasonable the last time I checked. There are formula's that allow you to verify if you have achieved the proper clamp load on the bolt. The compression limiter doesn’t have to press fitted, though I think it is better especially if the component is removed often
.
We use a lot of the item you describe made by the following.

http://www.spirol.com/apps/internet/spirol/website.nsf/SpirolSplash!OpenForm

 

[jmarkus]

Unfortunately, I haven't found a supplier (including Spirol) that offers an off the shelf compression limiter that will fit. They have quoted a custom part for us, but we think we can make it cheaper.

 

[mikeb350z]

Jmarkus,
Contact

http://www.accu-trak.com/

and they will help you through this. They're the best in the business!