8mm M42 cobalt coring drill. Cores standard 8mm guides. Why a coring drill? Because it is the only proper way I know of to remove a guide from the head without swelling or damaging the guide hole in the head. For years I was frustrated with having the guides come loose in the heads after a few thousand miles. I had the guide holes measured with some electronic bore gauges and found out that they were not straight, round or the same size from one end to the other any more. The aircraft engineer suggested that we core the guide 75% to 85% of the way and then drive it out to eliminate this problem. It did eliminate it. We also discovered that race heads which had the bosses cut would come right out without breaking the boss off. This slick tool does just that by first spot facing the spring end of the guide flat with our GB 706 (be sure all of the guide head is removed) to the aluminum boss and coring from the spring side 75% to 80% of the way through the old guide. You can then tap out the guide with an old 10mm head stud with no damage to the head. The new guide will now be straight in the hole with the proper press fit from one end to the other. Remember, even bosses cut for inner and outer springs are not normally broken or damaged with this procedure. The Berg coring drill resists breakage due to an exclusive design. Provides years of trouble free service and can be resharpened. Also available in 9mm as GB 712-9
Made in USA by Gene Berg Enterprises.
9mm M42 cobalt coring drill. Cores standard 9mm guides. Why a coring drill? Because it is the only proper way I know of to remove a guide from the head without swelling or damaging the guide hole in the head. For years I was frustrated with having the guides come loose in the heads after a few thousand miles. I had the guide holes measured with some electronic bore gauges and found out that they were not straight, round or the same size from one end to the other any more. The aircraft engineer suggested that we core the guide 75% to 85% of the way and then drive it out to eliminate this problem. It did eliminate it. We also discovered that race heads which had the bosses cut would come right out without breaking the boss off. This slick tool does just that by first spot facing the spring end of the guide flat with our GB 706 (be sure all of the guide head is removed) to the aluminum boss and coring from the spring side 75% to 80% of the way through the old guide. You can then tap out the guide with an old 10mm head stud with no damage to the head. The new guide will now be straight in the hole with the proper press fit from one end to the other. Remember, even bosses cut for inner and outer springs are not normally broken or damaged with this procedure. The Berg coring drill resists breakage due to an exclusive design. Provides years of trouble free service and can be resharpened. Also available in 8mm as GB 712. Made in USA by Gene Berg Enterprises.