400 spindle thread adapter stuck

[OldFatMan]

The 400 my dad picked up for me has a 2 1/4" thread adapter for the 4 jaw chuck that is stuck on the spindle. Ive tried a couple of strap wrenches but so far I haven't been able to remove it. I'm reluctant to heat it but suppose I might put some compressed air through the spindle to protect the bearings but if I do get it hot enough to move I wont be able to use my strap wrench. The lathe came with a 3 jaw chuck and a face plate with 1 1/2"-8 thread but of course I cant use them with the adapter in place. I have a blank 1 1/2-8 threaded back plate ordered to remount the 4 jaw with the intention of turning the adapter off. Expecting (hoping) I will hit the bottom of the adapter before hitting the major diameter of the spindle thread and then be able to peel off the threads. I've no experience cutting threads yet but I do have the tools and change gears if it becomes necessary. Anything else I should be considering?

 

[KyleG]

Are the strap wrenches slipping, or are you reaching an uncomfortable amount of torque?

If the issue is strap wrench traction, you could cut a groove across the end of the face and try to remove it with a screwdriver or piece of bar across the slot.

If the wrench isn't slipping and it feels like you might break something, I wouldn't have any heartburn turning it off. One thing to verify is whether the register is larger than the thread diameter. On my lathe it is not, but if so you could hit the register before you reach the thread. Others wiser than me can provide better guidance here.

 

[OldFatMan]

Thanks Kyle- a bit of both- slipping a little but I've got more pressure on the pulleys and bull gear pin than I would like. My problem(?) is the 4 jaw is usable as is- I've been reluctant to do anything with permanent outcomes until I can do the permanent fix. When I have the new back plate in hand then I will get serious. I'll check on the register- thanks. Per the 3 jaw back plate and the face plate I believe the 1/4" "recess" in them is just cut to the minor thread diameter but it's worth another measurement and a close eye.

 

[Shiseiji]

Couple of options to consider. Warm up the adapter and try some Kroil or, almost as good, Liquid Wrench. Liquid Wrench being easier to come by. The heat will aid the capillary action. If that isn't sufficient, try using a can of Dust-Off as a coolant on the spindle. I'd spray it on the inside of the spindle. The spindle is massive enough that obviously I wouldn't be concerned about the metallurgy, but I wouldn't go crazy either. Have some propane/MAPP gas ready for the adapter. Cool off the spindle then warm up, not heat way up, the adapter. Use the Kroil or Liquid Wrench again after each cycle. I used to free up seized vintage sewing machines this way, just needed patience for sometimes several cycles over a few days. I knew someone who swore by Oil of Wintergreen as a penetrate, can be found as an "Essential Oil" but I don't care for the odor at all.

Ron

 

[Shiseiji]

On cutting it off. I'd cut the adapter threads off left to right starting ~ 1/8" shy of the register till you get just past the threads, looks like that will be safely shy of the spindle threads. That will give you a better surface for the strap wrench, or, why not, a big pipe wrench. If the adapter is soft, you can file a couple of flats on it. In lieu of having something to lock the spindle, rather than the back gear leaver, cut a wedge from a hard wood if you have any, soft wood if not, and put it between the bull gear and the spindle housing.

 

[Bob Korves]

A previous owner may have become tired of the adapter coming loose all the time and then mounted it with a strong setting thread locker from a squeeze tube. Some of that stuff can be quite difficult to get loose again unless significant heat is added. Other types might break down at higher temperatures and you will end up with a bunch of other nasty stuff stuck between the adapter and the spindle. None were designed for easy removal, and that may be what the previous owner wanted to achieve. Try to look the setup over with good light, good glasses, and any other things you can think of to help you to determine how the adapter was mounted.

 

[OldFatMan]

Success! Thanks guys- it is resolved! Needed a little more confidence and a combination approach I guess. I didn't heat it still to avoid any chance of affecting that special bearing and lube but did a bit more cleaning on it to check for thread locker and then gave it another dose of PB. In my search before posting this I had read about hanging a weight on something chucked across the face with the back gear locked up. Thought it was worth a try so I put the chuck back on, put the grub screw back in (another issue- the grub screw positioned the chuck away from the face of the spindle adapter and the chuck run out was really bad. More on this later.). I put a trailer hitch torsion bar across the face with wood blocks to protect the bed and gently hung a bucket on the end of the torsion bar with about 15' of 3/8 chain in it. Position my shop stool under the bucket giving it about 5" of clearance just in case it did work. Well it did- the torsion bar made an impressive crash when it slipped out of the chuck jaws and hit the concrete floor- took less than 5 minutes and the charater added to the shop stool is hardly noticable. I think now if I had of used the wood block you mentioned and been a bit more aggressive with the strap wrench it would have come but I was afraid of breaking the plunger pin. But now the added benefit (maybe?)- the adapter is still serviceable. Without the grub screw, the chuck back registers on the end of the adapter and the adapter registers on the spindle shoulder and runs reasonably true. That is how I have been running it- without the grub screw and have had no issues dialing in my work. Now I'm thinking about applying said thread locker between the adapter and the back plate without the grub screw so everything shoulders up and save my new blank back plate for a new 4 jaw sometime in the future- this one has seen better days and might be useful mounted on a fixture on the mill table one of these days (do you use a 4 jaw for that?). Pretty sure the adapter is steel but it's certainly not hardened. I don't want to cause myself to go down this path again with a stuck adapter- am I buying trouble reusing it? It wont need to come out of the chuck again- as long as I oil it before putting it on the spindle is it likely to stick again? I feel a little bit like the boy who cried wolf but the comments and advise gave me some direction. Thanks.

 

[OldFatMan]

Here is the grub screw arrangement in the back plate.

 

[Shiseiji]

Success! Thanks guys- it is resolved! Needed a little more confidence and a combination approach I guess. I didn't heat it still to avoid any chance of affecting that special bearing and lube but did a bit more cleaning on it to check for thread locker and then gave it another dose of PB. In my search before posting this I had read about hanging a weight on something chucked across the face with the back gear locked up. Thought it was worth a try so I put the chuck back on, put the grub screw back in (another issue- the grub screw positioned the chuck away from the face of the spindle adapter and the chuck run out was really bad. More on this later.). I put a trailer hitch torsion bar across the face with wood blocks to protect the bed and gently hung a bucket on the end of the torsion bar with about 15' of 3/8 chain in it. Position my shop stool under the bucket giving it about 5" of clearance just in case it did work. Well it did- the torsion bar made an impressive crash when it slipped out of the chuck jaws and hit the concrete floor- took less than 5 minutes and the charater added to the shop stool is hardly noticable.

Thanks for the mention of using a leaver. On another Logan forum a member posted a picture of another way to jam the bull gear using neither the teeth or the pin: https://groups.io/g/Lathe-List/message/42095

Ron