New PM 1236 on its way!

Here you go. I got them from this place: http://www.devcocorp.com/gits.htm
Download the PDF catalog and they're GB style a few pages down.

I have 15 left and can spare you a couple. I havent replaced all the ones in my lathe yet and need a couple for a Mill mod that I'd like to get to one of these days. To get the old ones out, twist in a wood screw and tug on it.

PM offline.

Until you get them replaced, keep swarf out of there by twisting in a piece of paper towel etc. It won't hurt anything if they sink in. The ball is most likely jammed in the middle of the spring. Only take things apart if you dont get the ball out when you remove it.

Ray
 
Here is a prototype of the new fingers I'm making for my rests. Not complete yet but it works. New part.jpg

Bob

New part.jpg
 
Very nice Bob... What are you using for a bearing sleeve? Make a shoulder bolt if you can. The ID of those 25mm bearings is about 5/16 if memory servers and there's not much room for a bushing.


Ray
 
BOB

I had the same thing happen to my compound bb oilier.I was curios to what kind of shape your back plates are in? I know I had to true mine up starting with the spindle,I got my 4 jaw back plate trued up today so now I can true up my 3 jaw back plate.Have you tried your face plate yet?I was wondering if your taper was undersized?




JB
 
I trued up my faceplate a couple of days ago. It was only off a few thou. The 3 jaw seems to be OK so far. I haven't checked the 4 jaw.

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Ray C said:
Very nice Bob... What are you using for a bearing sleeve? Make a shoulder bolt if you can. The ID of those 25mm bearings is about 5/16 if memory servers and there's not much room for a bushing.


Ray
Click to expand...

Ray: I just used some bearings I took out of an old laser printer. I don't know what you mean by a bearing sleeve. The bearing I used has a 1/4" shaft hole so for now I just used a 1/4" set screw for the bearing shaft.

Bob
 
Bob,

Those threads are up against the hard steel of the bearing (most likely a 400 series stainless steel) and have a candle's chance in a rainstorm of lasting very long. Once they peen, the inner race of the bearing will want to climb around in circles and will cause you problems -especially if you use the CR with a cats head (when is when you need precision). For centering a shaft, probably not a show stopper. Here's a pic of a shoulder bolt. You want the inner race a snug fit on the shoulder. A bearing sleeve is what you'd put between the threads of a normal bolt and the inner race if for some reason, you could not employ a shoulder bolt. The sleeve would be threaded to fit the screw. It would "approximate" the shoulder bolt once constructed. -It's still a compromise. -not ideal.


SB-10200500---20.jpg





Both the 3J and 4J are pretty decent. They're the same as the house version of Shars brand and I just bought a 6" 4J from them. When you spin those chucks up to test them. Close the jaws (for safety) and spin-up from slow to fast.

Ray



rdfoster said:
I trued up my faceplate a couple of days ago. It was only off a few thou. The 3 jaw seems to be OK so far. I haven't checked the 4 jaw.

- - - Updated - - -



Ray: I just used some bearings I took out of an old laser printer. I don't know what you mean by a bearing sleeve. The bearing I used has a 1/4" shaft hole so for now I just used a 1/4" set screw for the bearing shaft.

Bob
Click to expand...
 
If I may make a suggestion. On the threaded side of the slot in your "finger", tap it for the shoulder bolt threads, but counterbore it about 0.050 or so to fit closely on the shoulder to gain support on that side of the bearing slot. On the other side, bore it through the same size as the counterbore. You could just ream it to full calculated depth before milling the bearing slot even. Probably a good way to ensure alignment on both sides of the slot. Then counterbore it generously to clear the shoulder bolt head, but do a little math and make sure the shoulder bolt bottoms out on the shallow counterbore on the "far" side. That way, you can tighten it properly without collapsing the slot at all and risk pinching the bearing. Those shoulder bolt have a ground OD on the shoulder area and are normally nominal to -0.002 in size and can be had in metric as well if needed to fit the bearing. Also known as stripper bolts, as they are used in punch press work to hold the stripper plate in place.


BTW, Ray, most ball bearing races are made of E52100 I believe. I've ground a few of them as specials for customers. But also have machined larger thrust bearings that were carburized and hard-turned after HT. They were 8620.
 
Thanks Tony about the bearing material... I was under the impression that the "roller skate" bearings were just 400 series SS... Anyhow...

Another thought about constructing a fork to hold a bearing, is to drill the holes first before you mill the slot. If mill first, pressure from the drill bit might actually bend the "tongs" of the fork. (ask me how I know this... :- I got to make that part twice that day. Practice makes perfect)).


Ray
 
Never had so smooth a finish. I first thought this steel was a piece of junk. I tried to turn it and it chattered and looked like crap. I don't know what I did differently but I think the finish is very good.
smoothfinish.jpg

Bob

smoothfinish.jpg
 
rdfoster said:
Never had so smooth a finish. I first thought this steel was a piece of junk. I tried to turn it and it chattered and looked like crap. I don't know what I did differently but I think the finish is very good.
View attachment 53183

Bob
Click to expand...

Bob!

That's an incredible finish! What DID you do?


Bernie
 
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