head column bolts

[mzayd3]

Has anyone else had any issues with the head clamping bolts (lock the head to the column) spinning in their cast bosses? I have had an issue with them since I got the mill secondhand. I ended up pulling the bolts out totally and found the threads were badly distorted from over tension. I can only figure that someone overtightened them repeatedly. The boogered up threads locked the nut to the bolt, causing the bolt head to round over and spin in its boss. My solution is to replace the 5/8" bolts with 3/4" bolts with the hex heads milled down to fit in the boss. Also, what size and thread type are your bolts? I have a sneaking suspicion that the bolts I pulled out are not original. I am replacing with a 3/4" fine thread bolt with a 60* thread. Are Acme threads more apro-pros?

 

[JimDawson]

I think you would be better with a 60* thread. An Acme thread would not hold as well.

 

[sdunt]

That replacing bolts thing sounds familiar. I recall reading someone write up about replacing the original (metric) bolts with US made bolts because the originals were really soft. Standard 60 degree bolts should tighten better and maybe grade 5 or grade 8 would be better. it takes a LOT of pressure to clamp one of the split casting models to the column. My RF is an Antique and it uses dogs that move independent of the casting to clamp the column.. SO far it works really well. Although I don't move it all that often.

 

[Whyemier]

That replacing bolts thing sounds familiar. I recall reading someone write up about replacing the original (metric) bolts with US made bolts because the originals were really soft. Standard 60 degree bolts should tighten better and maybe grade 5 or grade 8 would be better. it takes a LOT of pressure to clamp one of the split casting models to the column. My RF is an Antique and it uses dogs that move independent of the casting to clamp the column.. SO far it works really well. Although I don't move it all that often.

I have an RF mill and I'm not sure what you're speaking of when you say "it uses dogs that move independent..."ondering: You have a photo that might enlighten me. I'm always looking for way to improve the mill. I had also read somewhere using grade 8 bolting will help.

 

[mzayd3]

well, I replaced the bolts with 3/4 all thread and a few nuts. Welded one set of nuts to the all thread and milled them to fit in their bosses. Works well now. I can only imagine that someone had no idea how tight to make them and just over torqued them. You can see it in the threads.

 

[sdunt]

Ye Olde, picture is worth a million words. The clamps on my RF are in FRONT of the column, and I pulled one of them out and its hanging from the handle of the top one.

The dogs, or round slugs with the flats on them are two pieces.. One goes in the hole in the photo and the other goes on the other side in a similar hole. The bolt and handle compress the slugs - dogs against the sides of the round column to lock the head in place.

This is an Enco Model 105-1530 Enco support said It was made by a company called Fing, and no longer made NOR parts available. Of course I've got 2 lathes and this mill, so it might take longer, but I think I can handle the replacement parts, should that arise.

I have an RF mill and I'm not sure what you're speaking of when you say "it uses dogs that move independent..." You have a photo that might enlighten me. I'm always looking for way to improve the mill. I had also read somewhere using grade 8 bolting will help.

 

[Rbeckett]

Yup. A 60 degree fine thread is the best for the application. I would have gone a hardened bole and welded the extension on to that way. Once you got it nicely welded you could mill off an excess build to keep the seating surface flat. You would never break or round the threads on the bolt, all you would have to do then is insure you don't tighten it enough to pull the threads that are tapped to clamp the column. Good luck and looks like a fun and useful project.

Bob

 

[stupoty]

I had the bolts on my rf25 give up, they looked very much like the way your threads had gone, i used a quick fix of the longest studs from a clamping set as the nuts seemed to fit the hex recess quite well and i locked them off with regular m12 nuts.

i have ment to improve it some but it's been like that for a year and has been working fine.

stuart