Turning off a Stuck Backplate

[AGCB97]

Make a plywood wrench that fits the jaws.
Aaron

 

[matthewsx]

Thanks for the responses guys. I should lay out a few things. I have been oiling it daily, but I don’t think rust is an issue here, maybe chips stuck in the threads, . I had been using an Allen key in the chuck and a strap wrench to stop the spindle from moving and tried torquing and hammering to no avail. From there I made a large bolt with 3 flats to fit into the chuck and tried both an impact and then a 2’ wrench using full force on both the strap wrench and the 2’ and striking it with a sledge. No movement from that, even with the addition of heat. The jaws are starting to get a little beat and I really don’t want to hurt the spindle. I don’t have a ton of time to get this off and I have some projects I need to get the 4 jaw on for. The 3 jaw isn’t the nicest anyway and I’m okay with destroying the backplate in order to get what I need to get done, done. If I had more than a month left before I have to leave for school I’d be more than okay with leaving it to sit for weeks.

Definitely one of those situations where being in a hurry might cause bigger delays in the long run.

John

 

[benmychree]

Just make chips out of it, be very careful not to cut into the spindle.

 

[piper184]

Even if the spindle threads are in perfect shape and absolutely clean, some swarf in the internal threads can cause a jammed chuck. (ask me how I know....) Getting the internal threads absolutely clean is exponentially harder than the spindle threads.
For me, usually I can get the chuck loose by engaging the back gears and leaving the bull gear stud locked in. An adjustable wrench on one of the jaws and a couple of sharp raps with a soft blow hammer will knock it loose.

However excess chips or rust in the threads can add several layers of difficulty.

Heat is probably your best friend, but the idea is to get the backing plate up to it's maximum expansion temperature without getting the spindle to the same point. To that end you want to be able to apply LOTS of heat QUICKLY to the backing plate and have some way of keeping the spindle relativity cool. Even a wet rag stuffed into the spindle will help with that. The biggest part is that most home use propane torches just don't put out enough BTU to do the job. You might be able to do it with two torches at the same time, but even then the heat is likely to travel to the spindle and cause it to expand as well.

As an indicator, most oils will start to smoke at about 400F and also as a generalization, most metals quit expanding at about that temp as well. This is only a general guideline.

Using a long lever arm and smacking it hard with a hammer might do the trick, the point is to try and not exceed the shear strength of whatever parts are holding the spindle still.

As a last resort, I would certainly consider the backing plate as sacrificial. Especially in contrast the value of the gears or spindle. You can always turn a new backing plate.

Best of luck to you in this endeavor.

 

[rwm]

Pack the spindle bore with dry ice. ($3/lb at Harris Teeter here) Heat the back plate with 2 torches. You will need to configure a long cheater bar to fit the holes in the back plate somehow.



Dry ice used to remove a back plate stuck inside the chuck...

 

[tq60]

BFH...

This is in the old books.

Place the lathe in the lowest speed, NOT IN BACK GEAR.

It looks like a belt drive. Find someplace where you can use a c clamp to lock up the belt, clamp the belt together, or with a block of wood between, and different machines vary.

The manuals would direct using the chuck key, but you can get the biggest crescent wrench that you can find with the biggest hammer you can find.

Lock the spindle with one jaw horizontal towards the front.

Place the wrench on this saw, get the wrench as snug as possible.

Apply downward pressure to wrench.

Tap the wrench with the BFH.

Tapping is just dropping the hammer onto the wrench from about 6 inches, the spindle must be jocked for this to work.

Sent from my SM-G781V using Tapatalk

 

[Ultradog MN]

The idea of cutting it off is insane.
Two replies suggest heat.
That is the answer!
If you don't have an oxy/acet torch go to Home Depot or wherever and get a Bernzomatic torch and buy a bottle of Mapp gas which is a mixture of propane and acetylene and gets hotter.
You don't have to get it ferociously hot.
Just warm it all the way around to a couple hundred degrees.
I removed the stuck chuck on a 14" SB earlier this summer. Warmed the hub with a torch and it popped right off.
It took me about 1 minute.

 

[stupoty]

Thanks for the responses guys. I should lay out a few things. I have been oiling it daily, but I don’t think rust is an issue here, maybe chips stuck in the threads, . I had been using an Allen key in the chuck and a strap wrench to stop the spindle from moving and tried torquing and hammering to no avail. From there I made a large bolt with 3 flats to fit into the chuck and tried both an impact and then a 2’ wrench using full force on both the strap wrench and the 2’ and striking it with a sledge. No movement from that, even with the addition of heat. The jaws are starting to get a little beat and I really don’t want to hurt the spindle. I don’t have a ton of time to get this off and I have some projects I need to get the 4 jaw on for. The 3 jaw isn’t the nicest anyway and I’m okay with destroying the backplate in order to get what I need to get done, done. If I had more than a month left before I have to leave for school I’d be more than okay with leaving it to sit for weeks.

If you are bending the chuck jaws then it's probably a small spot of rust.

I had a very stuck chuck , I ended up holding a hacksaw blade by hand and slitting it, then used a wedge to fracture the last part to avoid damaging the threads.

I was going to replace the back plate but it's been fine so I just use it as is.
Stu

 

[SLK001]

I've tried all the methods and gone through all the threads for getting this thing off to save the backplate, but it is truly stuck.

Sorry, but you still haven't explained what methods you have tried. One of the best methods is to put a large lever arm horizontally in the chuck (or mount it using the screw holes in the back plate), then hang a bucket with weight on the end of it. Fifty pounds of weight at the end of a 4 foot lever arm will put 200 ft-lbs of CONSTANT force on your plate. This is usually enough to break a stuck chuck free over a couple of days (oil the interface daily).

If weights don't work, then use the @stupoty method of HAND HACKSAWING a slot in the plate, then a wedge to split the plate. Do NOT use an angle grinder. The grit from spent wheels will damage everything on your lathe. Doing the sawing by hand is a PITA, but it will not get damaging grit everywhere.

 

[jaker4p17]

Hi and welcome,

Are they still running the kart track at Ravenna? I always meant to get down there when I lived in Michigan but never made it.

When you say you've tried all methods for getting this off how long have you been working at it? My one experience with a stuck chuck it took weeks of patient effort but finally got it loose. It's worth taking more time if you've only been working at it a few days since it appears undamaged in your photos.

I guess if I were going to try and turn that off I would just cut it down until I only had maybe 1/2" left then cut a slot perpendicular to the spindle as close as I dared. With that, a few blows with a cold chisel should break the cast iron and get if off.

But, I'd really try a little harder before giving up. I'm sure someone who's actually had to do what you suggest will come along with better advice than me soon.

John

I never responded to you as I should have, I think I know the kart track you're talking about if it's the one on the dirt road, I think It may be running still but I've never seen anyone racing there but I have seen cars parked back there. But I don't think I've driven by in the past 5 years.