Turning between centers on the g0602

[dewbane]

I've talked about this bits and pieces in other places, and still don't have a plan, so I thought I'd start a thread here.

I wanted to try turning between centers, so I bought some factory dogs from Grizzly. They didn't remotely work. Elsewhere, someone pointed out that a drive plate is a different animal from a faceplate. Here is a picture of an example of a real drive plate, posted by darkzero:



My original faceplate was pretty bad anyway. The first time I put it on, I had to face off an alarming amount of material to get it flat, and it still doesn't run true about the axis of the casting. Somebody was drunk that day. Anyway, I bought a replacement to use whenever I actually want to bolt something to a faceplate, and I machined one of the slots in my wonky one to accept all the sizes of dogs I had. I also took the slots closer to the inside and outside edges.

I'm not going to swap everything around to take a picture, but what I ended up with looked a bit like this, except with my own redneck version of a dedicated drive plate. (Picture also by darkzero.):



In my case, it's probably a lot worse than that. The dogs are missing the plate by a mile, or at least a good inch or two.

Possible solutions:

Buy a real drive plate to fit this lathe. I went looking, and didn't find anything promising. I didn't find anything for sale that looked anything like darkzero's pictures, actually.

Extend the legs on the dogs, or make new dogs. While thinking about that, I ran across a comment in some other thread, where someone pointed out that factory dogs are all smooth and round, and this can be the difference between bruised knuckles and sticking your hand into a blender full of bailing wire. That was a good quote. I can't find who said that, or I'd give proper credit. Anyway, valid point. Making nice dogs that have all the pointy parts eased would take a lot of time. Plus I already have a bunch of dogs that would work perfectly fine if I had any way to drive the things.

Extend the reach of the plate itself. I thought about fabricating some kind of rigid extension out of angle iron or something. This seems like a potentially lethal accessory though.

Buy a big hunk of cast iron, and pay some guy with a much better shop to make me a drive plate. I've seen Atombomb76 or whatever his name is make one from scratch. I bet that didn't come cheap though.

Source a 4MT center that's shorter. It looks like these things cost upwards of $75 though.

Finally, since this is basically the only use I can see for the center I have, I could spend an entire afternoon whittling it down.

Anyway, lots of head scratching. I've put some thought into this, and still don't have a good plan. I feel like I can't be the only person who ever tried to turn between centers on a g0602, and I'm ready to say I give up. I'm ready to quit guessing, and just let somebody tell me the answer now. I figure there just has to be an easier answer, and I'm just overthinking and making life too complicated again.

 

[fitterman1]

Obviously you're using bentleg dogs.
What about modifying the dog you wish to use by cutting off the bent section and putting a threaded driving pin into your faceplate?

 

[dewbane]

Obviously you're using bentleg dogs.
What about modifying the dog you wish to use by cutting off the bent section and putting a threaded driving pin into your faceplate?

I forgot to add that to the list of possible solutions. I looked at that, and I completely agree that it's a viable solution. One bad thing about parts that are smooth and curvy is it's hard to drill into them at a tidy angle. I'm also concerned about the smaller size dogs. I'd have to get down to numbered machine screw sizes on the smaller ones.

I mean it might really be totally fine. The small dogs are for small work that won't be fighting as hard as something that needs a 1/2" drive pin. To get a right angle, I could scribe the center line and mount the thing using a height gauge or something to make sure the part is level in the vise. The angle isn't critical.

It seems like a lot of work though. I just find it hard to believe that it's impossible to use Grizzly dogs on a Grizzly lathe with a Grizzly center and a Grizzly faceplate without going to one or another of these extremes. It still feels like I'm missing the solution I'm expected to use. Like hook this to that and bang. Maybe it really is this complicated, and almost nobody cares, because people rarely want to turn between centers.

Thanks for the input though. I'm kind of snarking and running off at the mouth here, but it's not because you had a bad idea.

 

[RJSakowski]

I've talked about this bits and pieces in other places, and still don't have a plan, so I thought I'd start a thread here.

I wanted to try turning between centers, so I bought some factory dogs from Grizzly. They didn't remotely work. Elsewhere, someone pointed out that a drive plate is a different animal from a faceplate. Here is a picture of an example of a real drive plate, posted by darkzero:

View attachment 337762

My original faceplate was pretty bad anyway. The first time I put it on, I had to face off an alarming amount of material to get it flat, and it still doesn't run true about the axis of the casting. Somebody was drunk that day. Anyway, I bought a replacement to use whenever I actually want to bolt something to a faceplate, and I machined one of the slots in my wonky one to accept all the sizes of dogs I had. I also took the slots closer to the inside and outside edges.

I'm not going to swap everything around to take a picture, but what I ended up with looked a bit like this, except with my own redneck version of a dedicated drive plate. (Picture also by darkzero.):

View attachment 337763

In my case, it's probably a lot worse than that. The dogs are missing the plate by a mile, or at least a good inch or two.

Possible solutions:

Buy a real drive plate to fit this lathe. I went looking, and didn't find anything promising. I didn't find anything for sale that looked anything like darkzero's pictures, actually.

Extend the legs on the dogs, or make new dogs. While thinking about that, I ran across a comment in some other thread, where someone pointed out that factory dogs are all smooth and round, and this can be the difference between bruised knuckles and sticking your hand into a blender full of bailing wire. That was a good quote. I can't find who said that, or I'd give proper credit. Anyway, valid point. Making nice dogs that have all the pointy parts eased would take a lot of time. Plus I already have a bunch of dogs that would work perfectly fine if I had any way to drive the things.

Extend the reach of the plate itself. I thought about fabricating some kind of rigid extension out of angle iron or something. This seems like a potentially lethal accessory though.

Buy a big hunk of cast iron, and pay some guy with a much better shop to make me a drive plate. I've seen Atombomb76 or whatever his name is make one from scratch. I bet that didn't come cheap though.

Source a 4MT center that's shorter. It looks like these things cost upwards of $75 though.

Finally, since this is basically the only use I can see for the center I have, I could spend an entire afternoon whittling it down.

Anyway, lots of head scratching. I've put some thought into this, and still don't have a good plan. I feel like I can't be the only person who ever tried to turn between centers on a g0602, and I'm ready to say I give up. I'm ready to quit guessing, and just let somebody tell me the answer now. I figure there just has to be an easier answer, and I'm just overthinking and making life too complicated again.

Three possible solutions: 1. The MT4 will fit in the OEM four jaw. and the four jaw extends 2" further than the faceplate. Use your lathe dogs riding against the side of one of the jaws. 2. Bolt a block to the faceplate to act as a stop for the lathe dog. 3. Machine an adapter drive plate tha bolts to your OEM faceplate.

 

[Tozguy]

Like hook this to that and bang. Maybe it really is this complicated, and almost nobody cares, because people rarely want to turn between centers.

I don't avoid turning between centres because of the challenge of driving the work. Setting up a drive mechanism with a dog or otherwise is one area where hobbyist have to get creative because most jobs are one off. It is not complicated once you realize how many options there are for improvising. My drive plate and straight or bent tail dogs are considered a last resort.
A home brew drive set up does not have to be sophisticated or pretty, it just has to hold a moderate amount of torque.

 

[machPete99]

You can also use a regular chuck to do between-center work.
Buy or make your own center that can be gripped in the chuck.
Touch up the center after mounting so that it is perfectly co-axial with the spindle.
Arrange for the dog leg to hit against one of the chuck jaws.

 

[projectnut]

You don't need a MT4 center or a drive plate on the headstock end to turn between centers. As mentioned by machPete99, chuck up a piece of round or hex stock in either a 3 or 4 jaw chuck and turn your own center. You can then use one of the jaws on the chuck to engage the dog on your part.

Here's a video on how to make a center, and turn between centers. As a side note the video is made by The university of Wisconsin Engineering School. That's where I went to school some many years ago.

 

[benmychree]

Generally, in the past, lathes were provided with a driving plate similar to those shown in the pictures above, which is OK; the only problem here is that the center used is not appropriate for the job, too big, too long; those centers originally supplied were smaller in diameter than the spindle taper, and there was a tapered bushing to fit the spindle taper, and it was of an appropriate length to allow the dogs to engage the driving plate slot(s). In short, this particular lathe with a #4 MT spindle hole should have a #3 center and a #3-#4 sleeve (a 3-4 MT sleeve with the tang and knock out slot cut off to allow the center to stick out the small end). The center may have to be cut to length to get it's projection correct to allow the dogs to engage the plate slots. Generally, the centers for the headstock were left soft so that they could be easily trued up on the 60 degree taper with an ordinary cutting tool. Such centers were marked with a ring cut around the working end to show that they were the soft center. I also mark the center with a "0", with matching marks on the bushing and the spindle end to keep them running true when reinserted in the spindle.

 

[pontiac428]

Maybe a MT2 center in an adapter? If the center is flush with the drive plate, the dog will fit. Turning between centers is the purest form of lathe work.

 

[benmychree]

On my 9" Monarch Jr. lathe, the center projects about 3/4" from the end of the spindle and the drive plate, which is flush with the spindle end (normal for threaded spindles) This length allows a bent tail dog to engage the slot in the driving plate. If the center were flush with the face of the plate, the dog would be a considerable distance down the length of the part being turned, and possibly in the way of the operating being performed.