Turning between centers

shahargut · Sep 6, 2018

I have a part that has to be turned between centers to maintain accurecy when taken out and in the machine in the procces.
The plan is to allign the axel between the centers but i steel haven't figured out how to actually drive the part?

Any ideas?

plastikdreams · Sep 6, 2018

You need a lathe dog. They can be bought or made.

KristianSilva · Sep 6, 2018

face driver

Aejgx6 · Sep 6, 2018

I do all of my own driving, but if it’s an emergency you could call an ambulance.

M.B. Naegle · Sep 6, 2018

That guy.

Coadster32 · Sep 6, 2018

As stated...Lathe Dog or Face Driver are the most common methods. Sometimes if you're doing a light skim cut, just add a little more tailstock pressure, and then you don't need a driver.

pgmrmike · Sep 6, 2018

plastikdreams said:
You need a lathe dog. They can be bought or made.

KristianSilva said:
face driver

Coadster32 said:
As stated...Lathe Dog or Face Driver are the most common methods. Sometimes if you're doing a light skim cut, just add a little more tailstock pressure, and then you don't need a driver.

Yep. Small diameter and fairly light cuts, tailstock pressure works. Just dont get too aggressive with the pressure, too much on a small dia part can bend it.

Jashley73 · Sep 6, 2018

Face driver if possible. Lathe dogs work well, but if runout is super-critical, the unequal mass of a lathe dog can cause strange things, and this gets worse the higher the rpm.

If we're talking engine lathe speeds, then you're probably OK with a lathe dog, but if the runout & circularity is that critical, then stay as close to a face-driver setup [read: radially symmetrical, & dynamically balanced] as possible.

Gobo · Sep 6, 2018

Pretty vague. A wee bit more detail would aid your cause.

thermite · Sep 7, 2018

Jashley73 said:
Face driver if possible. Lathe dogs work well, but if runout is super-critical, the unequal mass of a lathe dog can cause strange things, and this gets worse the higher the rpm.

That applies only to the ancient ones, and they happen to be better balanced, dynamically than first appears. Lathes were slower, back in their day. It just wasn't a problem, nor need it be, now.

In any case, it isn't at all hard to shop fab a VERY well balanced one.

Two near-as-dammit identical bars, each with a Vee cutout arranged for equal length of bypass, opposite direction. Equal mass fasteners for clamping. That implementation must be easily 200 years old in use. A small "set" of forged loop and bent-tail were just handier.

You want a Rzeppa joint for TS set-over tapers? Have at it.

gregormarwick · Sep 7, 2018

thermite said:
That applies only to the ancient ones, and they happen to be better balanced, dynamically than first appears. Lathes were slower, back in their day. It just wasn't a problem, nor need it be, now.

In any case, it isn't at all hard to shop fab a VERY well balanced one.

Two near-as-dammit identical bars, each with a Vee cutout arranged for equal length of bypass, opposite direction. Equal mass fasteners for clamping. That implementation must be easily 200 years old in use. A small "set" of forged loop and bent-tail were just handier.

You want a Rzeppa joint for TS set-over tapers? Have at it.

You can balance a lathe dog I guess, but they still prevent turning the entire OD in one setup.

Face driver is better in every way. Especially the hydraulic ones that don't care about the precision of the face...

thermite · Sep 7, 2018

gregormarwick said:
You can balance a lathe dog I guess, but they still prevent turning the entire OD in one setup.

Face driver is better in every way. Especially the hydraulic ones that don't care about the precision of the face...

Must be a stock item? Show us a link. Locomotive axles to carburretor metering rods, please.

Otherwise, I'll stick with women for hydraulic "face driving", thanks!

gregormarwick · Sep 7, 2018

thermite said:
Must be a stock item? Show us a link. Locomotive axles to carburretor metering rods, please.

Otherwise, I'll stick with women for hydraulic "face driving", thanks!

So, the basic principle is the driving dogs are actually hydraulic pistons which all share a common reservoir, and therefore conform to the profile of the face with equal pressure. I think Sandvik Kosta were the first to make such, but they are commonly available from a number of manufacturers now. They can be had in surprisingly small diameters.

thermite · Sep 7, 2018

gregormarwick said:
So, the basic principle is the driving dogs are actually hydraulic pistons which all share a common reservoir, and therefore conform to the profile of the face with equal pressure. I think Sandvik Kosta were the first to make such, but they are commonly available from a number of manufacturers now. They can be had in surprisingly small diameters.

Thanks for that, Gregor.

I'm sure it will benefit "someone". I just don't happen to be he, this incarnation. At least not until I get another two Delta-Wye transformers bought and can get back to serious workholder hoarding again..

pgmrmike · Sep 7, 2018

gregormarwick said:
So, the basic principle is the driving dogs are actually hydraulic pistons which all share a common reservoir, and therefore conform to the profile of the face with equal pressure. I think Sandvik Kosta were the first to make such, but they are commonly available from a number of manufacturers now. They can be had in surprisingly small diameters.

Very interesting. Have never seen that type before. Thanks

Ox · Sep 7, 2018

gregormarwick said:
So, the basic principle is the driving dogs are actually hydraulic pistons which all share a common reservoir, and therefore conform to the profile of the face with equal pressure. I think Sandvik Kosta were the first to make such, but they are commonly available from a number of manufacturers now. They can be had in surprisingly small diameters.

Well if that don't beat all!

That is exactly what I envissioned from your previous description, but I really ??? the small chambers that it would have to be... ???

The Hydramax vise jaws have much more biggerer piston sizes, but apparently this works, and if so - would be a God-send for castings and such!

---------------------

Think Snow Eh!
Ox

DDoug · Sep 7, 2018

I have seen these, those piston ends are very sharp (think knife blade, crossed with a one way screw head)

I have seen the results, they leave a nice 6 way pattern
on the end of the shaft.

litlerob1 · Sep 7, 2018

I wonder if the "blades" or Drive pins (per the model) are a consumable item. I would automatically think and assume; YES, but how easy/cheap/accessible are they to replace?

R

DDoug · Sep 7, 2018

litlerob1 said:
I wonder if the "blades" or Drive pins (per the model) are a consumable item. I would automatically think and assume; YES, but how easy/cheap/accessible are they to replace?

R

Yes, I have seen them replaced IIRC the operator was able to replace them.

CalG · Sep 7, 2018

Now do any here actually think that the OP , who is asking about what is likely his first attempt at between center turning, is going to spring for a hydraulic compensated face driver?

Get real!

Just getting both a drive plate and a center in the lathe at the same time is going to be an issue.
Turning at "dog speed" is never going to cause a problem, that is why they invented carbon steel tool bits.

Jeesh!

Turning between centers

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