I’m replacing the head in my Delta DJ-20 8″ jointer. The bolts that hold the beaing blocks in place are cap head screws with split ring lock washers under them. The only markings on the bolt head is FKE 12.9. The old lock washers are pretty crushed, so I’m planning to replace them.
Are these hardened bolts?
Should I use hardened washers?
Does anyone know the torque spec for tightening these bolts?
Replies
You can run a file across them to see how hard they are. There's no need to go grade 8 in this application. Just a firm snugging is all you need. I repair machines and used to do independent repair work for Delta. There are no torque specs I know of. Don't get bogged down in tiny details.
12.9 is the grade of the bolt, it is hardened alloy steel. This isn't a grade you see very often. it's a real hard bolt. As such, it will take a lot more torque to stretch it. Does it tap into the iron? I'd be careful about stripping the threads. I think I would contact Delta, you can sign up free on their website for their service section. If the 12.9 bolts are correct, you need enough torque to keep them from rattling loose but you don't want to break anything either. Probably why the washers are crushed. Foot pounds will change if the bolts are oiled. Parts should be available and you can contact a service tech.
Beat it to fit / Paint it to match
Concern over breaking the bolt was my main concern. I have a tendency to over tighten. I found a chart that specified 33 foot pounds for an 8mm diameter, 12.9 grade bolt. I replaced the original lockwashers with grade 8 lockwashers and tightened to 33 foot pounds.
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