Replacement For Logan Headstock Double Row Bearing

James_Douglas

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After weeks of research and a dozen conversations with bearing manufacturers I came up to a brick wall on finding a "correct" bearing for the Logan Lathes. There are several bearings that will in fact fit dimension wise, however the key design parameter is the fact that the original bearings had a preload in them.

The manufacturers all make a single row bearing with a preload, but no double row bearings.

I called Logan lathe and talked with Scott Logan before ordering his bearing. Since Logan Actuator sells the bearings, at a much higher costs than the other dimensionally same bearings, I wanted to know which of the 3 or 4 preloads that are generally available by the manufacturers he was using. I was interested in going up on step if possible. Since the bearing is a special order non-refundable item I wanted to know if there was any choice.

Scott would not discuss in detail the bearing. All he would say was that the bearing met the original specifications.

Below is an email I sent to Logan Actuator yesterday in the morning. I am waiting on an answer.

--------------------------------------Original Message---------------------------------------------------

From: James Douglas

Sent: Monday, April 13, 2015 10:35

To: 'Logan Actuator Co.'

Subject: Question on Logan 820 bearing

ATTN: Scott Logan,

Hello Scott,

I don't want to beat a dead horse. However, I was suspired when I opened the box with the bearings inside. They are SKF. Prior to talking with you on the telephone and prior to ordering the bearing from you, I had talked with SKF and a lot of other bearing manufacturers. They all told me the same thing. They did not make any double row bearings with a built in preload.

I assumed that you were having the bearings made by a specialty house with a preload just as the original 5000 series New Departure bearings that Logan used in the 820 lathe (see attached).

I emailed and talked with SKF engineering this morning. I read them off the part number on the box and the part number off the bearing. Their response was:

****************************************************

SKF 3208 A-2Z is by design a bearing that has internal clearance. This bearing has axial internal clearance equal to 0.0004/0.0011 in. which is considered in the "normal clearance" range. Other identifiers in the part number to specify internal clearance are:

C2: axial internal clearance smaller than normal

C3: axial internal clearance greater than normal

C4: axial internal clearance greater than C3

Again, this bearing cannot be preloaded as manufactured.

*****************************************************

There is no marking on the box or the bearing to indicate that it is anything other than a what SKF calls a "normal clearance range". Also, they stressed that clearance range and preload are not the same things and I was told not to confuse the two. They also made it clear that this bearing "cannot be preloaded as manufactured".

Since the preload is what makes the lathe shaft not walk forward or back and there is no provision to set any preload on the shaft (by design) then the bearing needs to have a preload.

Can you shed any light on this for me please? If the bearing was drop shipped, is it possible that I did not get the correct bearing?

Thank you for your time.

James.
------------------------------------------------------------------------------------------------------------------

If anyone can shed any light on the bearing issues I would be grateful.

It appears that what I got from Logan was a "tighter" bearing than the other generally available bearings of the same size, but still without a preload of any kind. If you see the attachment, which is a page from a New Departure catalog 19th edition 1948, all 5000 series bearings had a preload. The Logan 45508 bearing is a 5000 series ND bearing. The 4 in the number just denotes a snap ring.

I am starting to get somewhat upset with the fact that I did my homework, talked (or tried) with Scott Logan about the bearing and its issues, spent the money for his part numbers and then got a bearing that the manufacturer tells me has no preload which by definition does not equate the original specifications.

When I get a response I will let people know. And again, if anyone has any insights, I am all ears.

James

bearing_ND_45508.JPG ND_Bearing_page_pre_load.JPG
 
Not alot of detail to add but i can say that i ended up at the same place.

At work i deal all sorts of custom bearings made special for our machines. Mostly linear but also thin section. I have dealt with all of the big players and local distributors. In the end, i was satisfied that whatever Scott was selling, while made by the big players was made special for the Logan to match the old spec.

My Logan 400 origianally had New Departure Bearings. I happen to have a catalog from back in the day and if i recall was able to cross the bearing i remove with the specification but of course New Departure is long gone as no-one makes the same thing anymore. I even tracked down NOS New Departure bearings. I was able to find the rear bearing but not the front.

In the end i realized it was a dead end unless i wanted to go out on my own. i ponnied up for what Scott sells and have been very happy. (I was also VERY careful when installing them...)

I am pretty sure i have more info in my Logan 400 headstock rebuild thread.

Matthew H
 
Thanks for the input Matthew. I also am at a dead end and will have for the time being to use the bearing that Scott sent.

The SKF engineers did in fact look up the dimensionally identical MRC bearing they sell and it has more clearance than the SKF I got from Scott. So, the one Scott sells is "better" than most of the other dimensionally identical bearings to the ND bearing.

That said, I plan on using my lathe, in addition to other things, to make some number 14NF screws for my 1940's Desoto's. Chrysler corp used #14 and #16 screws in the body that things like the dash bolt into. All in body welded or caged nuts. Since the local and mail order houses don't have them anymore...

That is one reason when I am interested in the least movement on the spindle I can reasonably get.

I did talk with the folks at NSK Bearing. They have a spindle bearing with a choice of four different pre-loads to choose from. I found one that has the same ID as the New Departure (ND) bearing. As a set of two it is within 0.5MM in length. The problem is the OD is smaller.

An NSK engineer said that I could make a sleeve out of billet steel...that was on the exact low side of allowable ID...that I could press the two bearings into this new collar. If the collar had the snap ring in it the sleeve would float (expand dur to heat) against the cast iron on the headstock like the original outer race.

I think what I am going to do is use the bearing supplied by Scott Logan for now and hit ebay looking for another spindle. I will them make up a sleeve and get the NSK spindle bearings and then swap them out down the line. Of course taking measurements both before and after to see what I get.

One thing the engineers told me. That since this is a hobby lathe that I can use more preload to get a much tighter spindle. The life of the bearing would be 1/2, but using it at home and not in production it would still out live me.

James.
 
James,
Are there any special markings on the bearing races? That might indicate a custom version of the stock SKF bearing.
 
James,
Are there any special markings on the bearing races? That might indicate a custom version of the stock SKF bearing.

Hi, there is nothing on the races but the usual numbers. I asked the SKF engineer if one could special order a double row bearing with a preload. Their response was that you could not in anything but very large quantities. They do not do small order specials and have not for a long time. Also, the type of bearing in question they said was manufactured in such a way that would preclude doing a preload.

Now it is possible that the two different SKF personnel I talked with are wrong. But, I doubt it.

I am interested in hearing back from Scott Logan on this. So far, over 24 hours and nothing in reply. Not even a note to say they are looking into it.

When I asked him in our phone conversation some weeks back about if I could special order a larger preload he would not even talk about it. He just said the bearing he sells is the same as the original specification. I am starting to wonder if the reason he did not want to talk about it is because the bearing does not have any preload.

If the bearing does not have any preload then although it may function, it is not as I was told a bearing that met all the original bearing design specifications. The New Departure bearings all had preload and unless Logan or SKF can demonstrate to the contrary...the shipped bearing I have does not meet those original specifications.

What irritates me is the lack of transparency on the whole thing. If the shipped bearing is the best that can be done without re-engineering the headstock, then so be it. But be upfront about it and publish the original specifications and the specifications of the replacement bearing and acknowledge the differences. The someone can make an informed decision if they want to investigate re-engineering the bearing solution or not.

James.
 
I have no experience with lathes with ball type spindle bearings. But I will point out that one way to introduce preload on the bearings would be to place an inner race shim on one end of the spindle or the other, in the desired thickness. This would be much cheaper than modifying the headstock.
 
I have no experience with lathes with ball type spindle bearings. But I will point out that one way to introduce preload on the bearings would be to place an inner race shim on one end of the spindle or the other, in the desired thickness. This would be much cheaper than modifying the headstock.

Unfortunately, the design of the headstock makes using shims a moot point. One person used a Belleview washer to ad a preload, however, the SKF guys told me to be careful using an external preload with this bearing due to its internal design.

JD.

PS. Still not reply to my inquiry to Scott Logan.
 
Besides the fact that Belleville washers aren't suitable for setting spindle endfloat on a lathe, if you can install one of them such that it reduces the end float with no thrust applied, then I don't understand why an inner race shim of the proper thickness wouldn't do the same thing plus not be sensitive to thrust in one direction. But I don't have a headstock or headstock cross-section drawing to look at.
 
So has the dog caught it's tail yet? I have a friend who works at SKF and I will just take my bearings over to him and figure out a replacement.
When I find out the proper workable replacement I will sell all of you the information $1,000,000.00. I'm thinking a cone roller bearing will
do the trick instead of a preload.
 
It's interesting how many iterations of this bearing topic on these lathes I've seen. I'm not sure I have ever seen any other easy answer aside from buying Scott's bearings. Thankfully I haven't had to do mine yet. But if I had to I'd probably go with his.
 
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