Plasma Cutting Bolt Holes

Back in August 2010 we obtained a contract to make transfromer core clamps for a company near us. It originally started out to be 5 clamp sets per day which consists of 4 angles of various sizes averaging 16" in length with an average of 6 holes / slots and tapped holes put into them. It was to double in size over a few months. In the 2 months it went to an average of 30 clamp systems or 120 parts, 7 days a week from 5 days a week. We where using the CNC plasma to cut all the slots and holes and used the mill for the tapped holes.

In the two months we produced over 7000 angle parts, which corelates to 42,000 holes . The accuracy of the plasma is dependant on how long you alow the tips to run before changing. For cutting holes in wall thickness from 1/8" to 1/2" thick and hole diamters from 1/4" to 1" we can hold +- 0.035" diameter easily and location +-0.008 with ease. We did however have to give up the order as the customer required a tolerance that was tighter than this for the hole diameter.

We believe the project has been a success even though we did loose the order. It has given us a very strong base line for future quotes and has opened up the range of possiblities for new customers. If you happen to a product line that requires parts to be bolted together and the tolerances given above are acceptable which we believe they are for most structural work, then plasma cutting is without doubt the most cost effective way to do it.

We set up custom jigs to load and unload the CNC plasma table with angle, channel, beams etc from which we procede to cut the holes and parts required.