4 jaw lathe chuck recommendations?

What Bruce said. Keep us posted. There are a few trick to making the back plate that we can help with.
Roberrt

 

Zapins - I mentioned above that I thought I had an extra 1 1/2-8 backing plate laying around, that was gonna send you. Unfortunately, I either no longer have it or just plain can't find where I hid it for safekeeping. Sorry.

 

Aw well thank you for thinking of me. I missed that post when reading through all the replies the first time around.

The back plate I linked got away ($70+shipping). I might just see if I can buy a steel/iron plate and try my hand at it. How thick does it need to be? 1"? 3/4"? I think an 8x8" or 9x9" plate would be big enough.

I am most uncertain of threading. How to grind the bit to the right shape to make the threads, how to actually do the threading. The youtube videos are all so neat looking and don't show what the operator is doing, only that the bit cuts perfect teeth.

When opening and closing the 3 jaw chuck back onto a part I'd guess it lets the part wobble by 1/32" to 1/64"? So trying to flip a part around or do anything to it that requires reseating is a recipe for a screwed up part. Maybe the teeth are out of line as you say, maybe the threads on the teeth are worn from 80 years of use? Either way I'd love to get the 4 jaw working because it is in fantastic like new condition and would allow me to individually manipulate the jaws to remove any kind of wobble.

 

1/32" is not related to a chuck jaw in the wrong position. Most likely wear- unfixable.
I'm sure the back plate your ordered will work. Clean the threads and then thread it onto the spindle. You will need to turn the face flat and then turn the OD to match the recess in the chuck plus .002. Calipers are sufficient for this if you are careful. Another tip- after you drill the bolt hole circle, drill an extra hole somewhere in the back plate and thread it. This will allow your to use a screw to remove the back plate if there is a problem or you want to reuse the back plate on another chuck. Otherwise it is very hard to remove. Ask me how I know...
Threading is a little bit of art. The grind for SAE threads is 60 deg. You advance the compound so you only cut with one surface. Not to be discouraging but I would stick to the threaded back plate until you have some flight time accumulated.
Robert

 

I didn't order the back plate I linked unfortuantely. It got pricey and I passed.

I'll see if another one pops up, or maybe try making one. I'll see if I can get the measurements of the current back plate so I can order the metal I need.

Here's a crazy thought. Couldn't I just make an adapter that threads over my spindle and into the new bigger lathe? Like a 1-7/8" to 2-/14" adapter? Or won't that work? Pretty easy and cheap to buy the correct size DOM pipe with wall thickness and cut threads into it?

Maybe a 3 jaw chuck with 1-7/8" thread would be a good purchase if I can find a knockoff china brand for cheap. I wouldn't mind if it was fairly true, it could be convenient for general learning.

 

I suggested making an adapter.

Have you tried marking your three jaws, maybe painting them different colors? Then pick one and mark your work where that jaw hits it. When you remove it, replace it with the same orientation. When you reverse the piece still align the mark to the same jaw. It should remove at least 90% of you error unless the scroll is very worn in a few places.

Take the jaws out and clean the scroll well and the jaws to make sure they're not loaded with chips holding them at odd positions.

 

Man I'm off my game today. Missing replies. Distracted with interview invites to different programs in real life.

I can try that when I get back. Clean out the chuck and mark the jaws to see if one is messed up.

I think what I need to do is order 50 pounds of scrap metal blanks for cheap off fleabay to practice on. Different shapes and sizes and just go to town.

I see people on YouTube flipping their part around and back again and it seems to be perfectly centered. Which is not at all my case! Haha.

 

They're never perfectly centered in a 3 jaw chuck. Closer in a 6 jaw.

It takes some time in a 4 jaw, longer until you learn how and it can be slow a frustrating when you're learning.

If a 3 jaw is 2 or 3 thousandth's off most people just live with it. For most stuff it really does not matter much. You'll never see the misalignment in service for slow turning or static pieces. You also don't have to turn everything around. Start with a longer piece, turn it, bore it, and part it off.

Everything you do to compensate for a misaligned chuck is what you should be doing anyway when you don't know your chuck is misaligned, because they all are to some extent. When you get used to keeping track of your workpiece with the jaws you'll help yourself again and again.

For precision you turn it between centers.

I'd try to get some lathe time in before spending too much on more chucks.

 

My 4 jaw backing plate only needs a 3.5" dia disk to start with. You need to take the plate that's on the 4 jaw off and take your measurements from that. The Cost of a 6" disk of Gray Iron and a 3.5" disk is about 3X. I'd order enough material to make 2 or 3 backing plates (the shipping is going to be the expensive part if you don't have a local supplier).
Use the backing plate you have now as a pattern. Just change the bore size for the spindle threads.

 

Ok so I got everything measured.

Yes the lathe spindle is 1-7/8" and 8 tpi.
The back plate is 5" diameter x 1" at the max depth.

I found that the back plate is actually made in a way that the threads are not part of the back plate metal and are instead held in place in a recess cut into the back plate. I wonder if this would be something I could buy as an insert?

I looked and found a guy selling 6x1.5" hot rolled steel rounds. He hasn't quoted me a price for 2 or 3 of them yet but I'm guessing 60 to 70 shipped sounds about right. That would give me 3 attempts.

How do I figure out the tool to cut the teeth on the back plate? I'm not sure what the pitch and degrees should be to match my lathe spindle and I don't think I have a thread pitch measurer. Is this information something that would be available on the interwebs or does it have to be measured on my lathe?

Also I wonder if it's possible to remove the spindle and replace it with a 2-1/4" down the line. That seems to be the more common thread for chicks nowadays? I mean the spindle should be replaceable right? It wouldn't make sense to damage the threads and have to replace the entire lathe.

 

I would buy 10" you use it like face plate
Some times you may need a large chuck

For back plate I use iron weight from Wal-Mart or any sporting store

Dave

 

Why a 10"?

The plate on the 4 jaw chuck is 5"

 

The thread is 60 degree angle. The pitch is 8 threads per inch, and you set that by putting the right change gears on your lathe (or shift a quick change gear box) to get 8 TPI.

Does your lathe have a thread dial? You need to learn how to use it to make threads easily. It lets you engage the split nut at the right time so the tool will track the previous path as you take deeper cuts.

 

The lathe does not have a thread indicator dial. I did however 3d print one for my lathe at 100% infill from PLA, but I haven't installed and tried it yet so I don't know if it will fit and work as intended.

Do you think I should just buy a 60 degree cutter or will grinding one be easy enough to get right?

I found a 4140 Steel Round Bar Stock - 7.125" x 1.375" Length for $25 shipped. I think this is the cheapest option I've seen. Do you think I should go with a few of these and just cut it down to size?

https://www.ebay.com/itm/4140-Steel...LZa8H~2:sc:USPSPriority!37813!US!-1:rk:7:pf:0

 

The most South Bend Lathe use same thread on lead screw as the spindle mount
A threading dial is not need

Dave

 

https://www.ebay.com/itm/southbend-...033142?hash=item3d77177d36:g:ztUAAOSwoBlaiJ3p

I've watched many of this guys videos http://www.thatlazymachinist.com/free-training.html

Also mr Pete on YouTube. Among others. Once you've seen their demonstrations, what OIF is saying will make perfect sense.

Pete

 

4140 is some tough stuff. You might do OK, but I sure like the idea of buying a cast iron one and modifying it.

You can grind a good 60 degree point if you're careful. Set your compound at 30 degrees so you only cut one side of the thread. Much easier because you're cutting less width. You'll need to have a sample bolt to use as a reference to make sure you don't overcut or under cut the thread.

 

You don't need the threading dial, it's handy but if you don't have one just leave the half-nuts engaged when you run it back for each pass. It's the same when doing metric threads since the thread dial doesn't translate for that.

When you reverse it make sure to back the tool out as even a few thousandths of slop in the leadscrew can make enough of a misalignment that it cuts a new track on the way back taking out your threads along the way.

I recommend cutting threads on a piece of scrap first, it's easy to mess up when first learning.

 

Is the thread left handed or right for the back plate?