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Oilite bush sizes

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Nick Taylor 230/03/2017 09:02:21
102 forum posts

Morning all!

I'm looking at some drawings on the Boxford spares website in order to get some oilite bushes for my shaper.

The bushes are all described as such - 'CT18 x 7/8 Oilite Bush'

What does the CT18 part of the description mean exactly? The 7/8 in this case seems to relate to the length according to the drawing. So I assume 'CT18' somehow tells you the ID and the OD?

Sorry if this is a silly question!

Cheers,

Nick

KWIL30/03/2017 09:56:33
3681 forum posts
70 photos

As an alternative to to "CT18 x7/8", just look at "Bearingboys" site for for all types of oilite bushes at good prices.

7/8 will be the length and the ID and OD will be obvious from your machine as the dimensions are generally easily identifiable as standard measurements.

Michael Gilligan30/03/2017 11:06:10
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23121 forum posts
1360 photos

This search facilty on the Bowman [Oilite] website might help:

**LINK**

http://www.bowman.co.uk/products/oilite_plain

MichaelG.

Ian S C30/03/2017 11:06:15
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7468 forum posts
230 photos

I'm not sure what the CT stand for but the 18 is the length of the bearing 1 1/8". Is the bearing plain or flanged? In the Boxford Shaper site it is listed as obsolete, also mentioned is BR-CT 18 x 7/8".

Ian S C

Nick Taylor 230/03/2017 13:11:22
102 forum posts

Hi gents, thanks for the replies!

The machine is complete at the moment, so as you say I can just measure the bearings, which is what I plan to do - also it looks like I need to make a new gear shaft as it is worn nearly 1.5 thou on one of the bearing surfaces, and is slightly out of round.

The machine runs great until you try to take heavier cuts, when slotting etc, and you start to hear a thump at the extremes of the ram travel which seems to be due to lack of lubrication on the rocker linkage bearings.

Looking forward to using the myford to make bits for the boxford, seeing as last month was spent making bits with the boxford for the myford

I was just curious if the 'CT' number referred to some sizing standard which I wasn't aware of.

Cheers,

Nick

Nick Taylor 230/03/2017 22:58:08
102 forum posts

Done some measuring, most are standard IMP sizes but there are a couple which are really bizzare, IDs of 680 thou and OD of 837!

Think I'll have to give boxford spares a ring tommorow.

Mike Crossfield31/03/2017 08:24:58
286 forum posts
36 photos

Nick

If you ever get to the bottom of the CT designations do let everybody know. Some (but not all) of the oilite bushes used on Myford lathes are specified on the parts lists using CT numbers, but I've never found out how to decode them.

Michael Gilligan31/03/2017 09:08:20
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23121 forum posts
1360 photos
Posted by Mike Crossfield on 31/03/2017 08:24:58:

Nick

If you ever get to the bottom of the CT designations do let everybody know. Some (but not all) of the oilite bushes used on Myford lathes are specified on the parts lists using CT numbers, but I've never found out how to decode them.

.

+1 for that ^^^

My best guess, so far, is that CT is a hang-over from the US material specification

See the table of equivalents on this page: **LINK**

http://www.bowman.co.uk/products/oilite_materials

MichaelG.

Ian S C31/03/2017 09:16:04
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7468 forum posts
230 photos

I have two options fot the CT, either the OD of the bearing, or the specs for the lubrication oil. I think there are different load rates for these bearings.

Ian S C

not done it yet31/03/2017 09:40:44
7517 forum posts
20 photos

I have one option for CT. I asked and was told it was a bearing prefix for a supplier that went ouf of business about 10 years ago. (From Peter at Bearing boys).

Nick Taylor 231/03/2017 09:59:33
102 forum posts
Posted by not done it yet on 31/03/2017 09:40:44:

I have one option for CT. I asked and was told it was a bearing prefix for a supplier that went out of business about 10 years ago. (From Peter at Bearing boys).

Have just been on the phone to Boxford and have been told a very similar thing - the CTXXX seems to be a manufacturer part number rather than a Boxford part number.

Didn't have any dimensions for the bearings, apparently a fire at Boxford a few years back destroyed a lot of the old drawings.

Looks like I need to get some cored Oilite bar and see how I get on making the odd size ones. Only 3 to make, the rest are standard sizes. The other option I suppose is to remake the shafts themselves to more standard sizes... Oh and need to make a gear shaft as well… and I’ve got about 12 hours of jobbing work to get done this week… so the shaper might have to wait!

Circlip31/03/2017 10:43:12
1723 forum posts

In the dim and distant, after (and during) scoffing sandwiches at lunchtime, essential reading, for me, was going through suppliers catalogues accrued over the years in the office.

UNFORTUNATLEY, in the rush to computerise their sales information, many companies dumped most of the original specs and streamlined the sales departments resulting in the short form catalogues we now have to use.

Bit like metrication, computer scanning and information storage was a cost implication for many of the smaller companies while some of the larger ones burned fortunes on what has now proved inadequate systems.

Regards Ian.

Muzzer31/03/2017 10:56:46
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2904 forum posts
448 photos

Wow. It's fantastically expensive stuff. Having recently been specifying sintered bushes myself, I know it's possible to machine the stuff but it's not considered ideal, as the surface finish suffers. It's also very spongy stuff and the ID collapses a fair bit as it's pressed in. That changes the normal dimensions you'd expect for press fitting, as well as the ID of the bore before pressing - it's not really practical to ream it in place. If at all possible you'd find out the approved dimensions of the real thing before it's fitted.

The bar stock in the link doesn't specify anything as fancy as the porosity (or the actual composition). IIRC this would normally be in the 20% ballpark for what we consider to be Oilite - something like B50.

Murray

Mike Poole31/03/2017 11:43:02
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3676 forum posts
82 photos

I was surprised that Oilite is available as bar stock, I always understood that the bushes were sintered to a finished size and take up their final dimension after fitting. Rework of the bush after fitting was not recommended as the open nature of the surface gets smeared and compromises the lubrication. But as we see you can buy bar stock so it must work to some extent. I always thought of Oilite as being a cheap bearing solution but it also has the advantage of being very compact and does not require complex machining in most applications.

Mike

Nick Taylor 231/03/2017 12:08:59
102 forum posts

I've been doing a bit of research and the two big things that you need to be careful of are;

VERY sharp tool with small cutting radius, preferably carbide as it will keep its edge better (although I’ll probably resort to some HSS-Co and be kind to the tool, think I have some M42 somewhere)

Fully clean bush of all debris from machining, then replace the oil contents by soaking in oil @ high temp (80°C is often quoted).

I was surprised at the cost of the cored bar, there are a few available on eBay for considerably less, but they are solid bar. But thinking about it, I’m sure you could drill undersize as you would any bar stock, then take your finishing boring cuts with sharp tool mentioned above to retain the porosity.

Mmmm, this will require some thought!

Cheers,

Nick

Michael Gilligan31/03/2017 12:21:05
avatar
23121 forum posts
1360 photos

Nick,

You have probably seen this already: **LINK**

http://www.oilite.com/bmp.asp

But it's worth posting here for easy future reference by others.

MichaelG.

Ian S C01/04/2017 11:12:55
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7468 forum posts
230 photos

When Oilite bushes are made, the bore is made oversize, I'm not sure if it is %, or so many thou per inch, and the bush is pressed into the mounting hole it compresses to the correct size.

Along with the spec CT18 x 7/8, I saw the alternative BR - CT18 x 7/8.

Ian S C

Nick Taylor 201/04/2017 14:56:35
102 forum posts

Hi Micheal - yes I had seen that thanks - good to have some SFM numbers to go off.

However - It seems the 'funny sizes' aren't that funny at all. What made them 'funny' sizes was being measured at 11pm.

Just been and remeasured with clearer eyes and turns out they are standard 16ths sizes.

So for reference the two part numbers that I couldn't find are (IDxODxLENGTH);

CT173 x 5/8 = 7/16 x 9/16 x 5/8

CT175 x 1 = 11/16 x 13/16 x 1

So we could maybe assume that CT174 would be 9/16 x 11/16 x length?

At least this prooves what we already knew about the CTxxx question - they are just part numbers and tell you bugger all about the actual size unless you have a list infront of you.

Off to price up some oilite bearings, hope to get the shaper back together soon!

Cheers,

Nick

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