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Building a D1-3 drive plate

M

MrBen

New Member
Hello all,
I have a couple of jobs coming up that require me to turn between centres. Previously I had just chucked up a piece of stock in the 3 jaw and drove the dog off one of the jaws. This works ok but I would like to refrain from running the dog against the jaws. My Bantam requires a somewhat hard to find MT 4/12 sleeve or centre to fit the spindle nose. I’m thinking about making a drive plate with an integer all MT bore to take the centre. Is there any reason I shouldn’t try this? I can’t find any commercially made versions, so I wonder if it’s not a practical idea. Any input is welcome.
Thanks.
 
If I understand correct, I think I've had a similar idea but its lower on the project list.
- buy a D-style backplate. This takes care of the spindle fit up
- machine a hole if required to accommodate your dead center which fits in the spindle socket I assume
- machine the face to something like what the old style dog plates used to be. Some have slots of various sizes, some have a threaded for a an extending post
Its been a while since I looked but even the dogs are getting a bit hard to find & spendy for what they are. But anyway the size of those may dictate the size of slots

1755712731283.png
 
Ya, that’s exactly what I had in mind. What I’m wondering about is why it’s not something somebody made. I think you would need the drive plate on a D style nose, so why not have the MT bore in it?
 
I would think that the plates aren't bored for a taper since concentricity would depend on the accuracy of the mount? IOW, much less precise than the taper already in the spindle.

But, apparently Grizzly sells a sleeve:

www.grizzly.com

Grizzly P97302912 - SPINDLE SLEEVE MT#4.5-MT#3 - Grizzly Industrial, Inc.

Grizzly P97302912 - SPINDLE SLEEVE MT#4.5-MT#3
www.grizzly.com www.grizzly.com
(Picture looks odd to me, though.)

If the sleeve works, then you could use a standard MT3 drive centre.

Craig
 
Exactly as Craig says. The best concentricity will be between the dead center & your spindle taper, eliminate the middle man.

But there is one more issue now that I'm recollecting. When you plug in a typical MT dead center directly into your spindle socket, you don't have as much control of dead center stick-out protruding beyond the chuck adapter plate because that's just how they make them. The plate itself takes up some space. Seems to me I measured & it was going to be quite close so I was looking at a smaller diameter D1-4 backplate in order to be a bit thinner. Making an arbor with a longer straight section is doable but a lot of extra work to get the correct MT fit. My 14x40 has an MT5 spindle socket. The lathe came with MT5/MT3 adapter sleeve which is quite accurate. I have not tried using that combination, or an MT-5 dead center for that matter, to see if that yields adequate stick-out. I've been dragging my butt because I have not had to do center turning but its coming up. I think the spindle nose geometry on older style lathes facilitated these dog plates better. Not sure why.

I have seen the dog resting on the chuck jaw method too & admit I did it for light duty center turning. One nice thing is you can turn a point in-situ being held in the jaws & it can stick out a bit which is required sometimes for over-travel. I don't think its hard on the jaws for light duty, but its probably not great for them in any heavy turning. The cutting torque is being transmitted laterally across the jaw seat. I'm probably being overly cautious. Call me a hand wringer but chucks are expensive.
 
The South Bend approach is a smaller drive disk threaded onto the spindle instead of the chuck. It has a slot for the drive dog.
When I acquired my Heavy 10L it didn't come with a center that fit in the spindle. One of the people on the SB Group made an adaptor to MT-3 for me. My only complaint is the MT-3 center sticks out too far for my liking. But I've done a lot of between centers stuff because it's so quick and easy to set up.
 
PeterT said:
I have seen the dog resting on the chuck jaw method too & admit I did it for light duty center turning. One nice thing is you can turn a point in-situ being held in the jaws & it can stick out a bit which is required sometimes for over-travel. I don't think its hard on the jaws for light duty, but its probably not great for them in any heavy turning. The cutting torque is being transmitted laterally across the jaw seat. I'm probably being overly cautious. Call me a hand wringer but chucks are expensive.
Click to expand...
This was also my thought.

On the matter of concentricity, I reason a good collet chuck has minimal run out, why not a MT bore? I suppose I will just have to make one and report back.
 
MrBen said:
On the matter of concentricity, I reason a good collet chuck has minimal run out, why not a MT bore? I suppose I will just have to make one and report back.
Click to expand...

I'm not exactly sure. The dead center (and the collet chuck analogy) has the benefit of longer contact area within the spindle seat vs a shorter longitudinal distance constrained by the dog plate thickness. It might also have to do with the size of the spindles (big hole) relative to smaller diameter MT center, but that's mostly a threaded spindle issue. Its almost like when the D-pin system became popular on lathes, you just don't see as many dog plates, which is weird. The used ones I see are often banged up in the dog slot which is a bit concerning. You are supposed to tie the dog back somehow so they don't smack on stop/start, but I've seen bigger dings.

Some guys bolt a dog pin on their faceplate, which I've considered too. But there actually isn't a lot of meat on the slot webs.


1755735560231.png
 
MrBen said:
On the matter of concentricity, I reason a good collet chuck has minimal run out, why not a MT bore?
Click to expand...

^ This

The spindle MT Bore will likely be as concentric as the quality of the bore grind, the bearings, and shaft allow. Certainly one level better than a collet chuck.

That said, if you cut a new center (or index one after making it), it will definitely be as good as the bearings allow.
 
PeterT said:
I have seen the dog resting on the chuck jaw method too & admit I did it for light duty center turning.
Click to expand...

I don't think its something you need worry about admitting to or restrict to light duty 🙂. There is no way you are creating plastic deformation with those loads and it's not moving so you're not create wear. SOP for machinists afaik, fast and the most accurate because there no sources of error like with a drive plate and spindle mounted centre (centre is perfect after a skim cut in situ).

If for some reason you didn't want to do so, consider making your drive plate with a hole able to take a stub of CR that you secure with a set screw or two - something replaceable that you can skim every time to 60 degrees.

Personally, I think its work/expense that produces inferior result vs turning a centre stub insitu in the three jaw....I've 800 years worth of projects so anything can be pushed off the pile is a win!
 
Mcgyver said:
SOP for machinists afaik, fast and the most accurate because there no sources of error like with a drive plate and spindle mounted centre (centre is perfect after a skim cut in situ).
Click to expand...

Someday I need to take a course in plain English. You just said what I said in far fewer and far better words. Well done.
 
When I am grinding between centers on our Landis Cylindrical grinder, there is a hole on the drive side that is fitted for a 3/8 X 16 bolt. In the years of use the different length bolts show no wear of concern.

Just some notes for future viewing.
Install the center and machine it to center it to the spindle. Important.
Mark the center to sit in the same position when put back in. Also important.
Tailstock center has to be solid, either tighten the ram or if no way to do so, modify the tailstock so that you can.
Deflection at the tailstock will have you chasing a taper that when the part is not being cut will not be apparent. The reason I mention this, is our Landis is somewhere over 70 years old. The socket in the tailstock seemed fine but a taper was showing up on the finished part. Under investigation we ended up removing the ram and spinning it in the lathe to recut the socket. We used a reamer to do so. The exterior of the ram itself is worn, but the ram is can be made solid via the tailstock.
Pierre
 
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