Thread recommendation for Cast Iron part



Hi dear friends and resp. seniors,

My topic is about to have ur valuable suggestions regarding thread type to be used in cast iron parts as per the application.

So basically I am working on design modification of cotton Ginning machine in which all the bolts were given earlier in BSW threads. We used it for more than 4 decades. But due to the shortage in availability and market trend of switching from BSW to metric bolts, we had also switched from BSW to metric threads and bolts. But as time goes on we faced some problems of getting thread failure in some casting parts like made up of FG200 grade. Then we analyzed the difference in both the threads of similar diameter and found that there is lot of variation in the thread height and pitch. We come to conclude that thread height and pitch in BSW threads is more as compared to same dimension Metric thread. Due to more thread height, the gripping between male and female thread is higher in BSW thread and due to more pitch, the quantity of material in two consecutive threads in more which results in more stripping strength to the threads. Also refer attached image of example of comparison between Metric and BSW thread.

I want your valuable suggestions after looking into the fact in above paragraph that which type of threads/bolts will be technically more beneficial to use specially in casting parts, after neglecting the issue of availability.



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