Turning between centers?

[radfordc]

Last evening I made a crankshaft for my version of Chuck Fellows John Deere motor. This was the first time that I had tried turning a complete crank between centers. The project came out OK, but I ruined my tailstock MT3 dead center. Since I don't have a ball bearing "live" center I used the dead center to support the work. I drilled the correct 60 degree holes using center drills and used white lithium grease as a lube. I ended up with the tip of the dead center worn away and badly grooved.

So what did I do wrong? Wrong lube; too much pressure on the work; ???

Charlie

 

[GailInNM]

Charlie,
Just guessing, but probably too much pressure. You have to keep checking the pressure as you go along as the material will expand from the heat produced by cutting and the pressure builds up quickly.
Gail in NM,USA

 

[kvom]

Now you have a good excuse to buy a live center.

 

[Tin Falcon]

Invest in a live center. I have generally used a dead center in low rpm heavy load applications such as knurling with a push style knurl .Dead centers get little use in my shop.
Dead centers are good on the head stock end when turning with centers.
IMHO a live center and a drill chuck are essential lathe accessories.
Tin

 

[tel]

Hmmmm .... I've managed to get away without a live centre for 30+ years, but there's time yet I guess.

Lube and pressure are the keys - maintain it only just tight enough. For lube Kop-R-Cote is brilliant, or STP as a second choice.

 

[rake60]

A dead center needs to be lubricated with an Extreme Pressure grease.
At work they supply us with CDB Extreme Pressure Lube#3.
I bought a tube of it from the tool crib at the shop and use it at home as well.

Was your dead center carbide tipped?
This is the MT2 taper center for my Grizzly lathe.

It has been used quite a bit and is still in decent shape. That small flat on the
point was caused by this idiot dropping it point down on the concrete.

The carbide tip will stand up to a lot more abuse.
Centers can be reground if they are damaged or burnt up but with the
price of a new one being around $10, it's rarely worth the effort.

Rick

 

[joeby]

I use my dead centers almost as much as the live centers, I use the EP grease also.

You only need to tighten the tailstock center enough to remove any play. I adjust it so it spins easily, just a very light drag. The dog will drive it, you just need to keep the slop out of it and check it from time to time as heat buildup will cause your work to expand and require loosening of the centers.

Kevin

 

[radfordc]

Thanks for the tips. I think I will see about a live center. What about this one.
http://www.littlemachineshop.com/products/product_view.php?ProductID=1189&category=

Charlie

 

[rake60]

Personally I like the Grizzly offerings.
They are priced a bit higher than other vendors of the import products
but their customer service makes up for that if an issue evolves.

My Grizzly lathe did come with a live center to fit the MT2 tail stock taper.
It was too short and in the way for most of the work I wanted to do with it.
I bought this one to replace it.
Grizzly H7962 Precision Long Nose Live Center
It's $43 but the long nose design allow for more room to get the carriage
and cutting tool back to the end of the work piece.

Just something to consider.

Rick

 

[mklotz]

Rick is correct. I have one similar to the LMS offering and it crowds the tool when working at the tailstock end of the stock.

I finally broke down and bought this ENCO offering...

http://www.use-enco.com/CGI/INSRIT?PMAKA=251-3020&PMPXNO=2984208&PARTPG=INLMK3

In addition to several sizes of male points, it includes a female and a pipe center. Unlike so many tool sets I've bought, I've had occasion to use all of the points.

 

[cfellows]

So Marv, have you been happy with the precision of this center with interchangeable tips?

Chuck

 

[mklotz]

I haven't had any problems. Of course, I'm not one of those guys who pretends to work to tenths, either.

Remember, every live center is only as good as its bearings (plus the TS alignment). If you're doing something really critical, use a dead center.

 

[Bernd]

Sounds like Charlie used a soft dead center.

I'm sure that the crankshaft he is turning isn't made from steel harder than the tailstock center. Take a file and see if you can file the dead center. If the file just glides right off it is a hard dead center if you can file it then it's a soft dead center.

Bernd

 

[Mainer]

Like tel, I've always used a dead center. Just keep checking the pressure as the work heats up ---- you can do this with the lathe running, just back off the tailstock a bit and then retighten until it's just tight --- and use a good lube.

I've thought about getting a live center, but I've never thought I needed one badly enough to justify the cost.

 

[Tin Falcon]

Charlie:
I have recently watched some old film on lathe operations found here http://www.wswells.com/video/index.html interesting enough all the machining was done on dead centers with a drive plate .No live centers used. I did pick up some tip on using dead centers. Lube early and often . adjust the tail stock often . if the the part heats up it will expand and tighten. Sounds like your part had insufficient lube and was too tight on the center.
A live center would not hurt though.
Tin

 

[kvom]

I have yet to use a dead center in the tailstock, but this thread is interesting on how to do it.

My lathe's tailstock has a pocket with a dauber for applying red lead to a dead center.

 

[Stan]

Somewhere I read that the proper way to set a tailstock center was to position the tailstock so that the handwheel handle is in the three o'clock position when the center is touching the center hole. Let the weight of the handle maintain the pressure.

If you have a soft dead center it is a good candidate to make a half center. Put it in the headstock and recut the taper then cut away about forty percent off one side. This lets you face off the end of the workpiece right down to the center hole.

 

[Tin Falcon]

I tend to use the 3 oclock method as a habit even with live centers. especialy if I am turning a disk against the face plate with no other support than the ceter and friction or a little glue/double sided tape. Machinable centers are great in the head stock because you can true it ti perfect any time you intal it. making a dead center is good practice for turning tapers.
Tin