Oilite bush sizes

[Nick Taylor 2Participant @nicktaylor2]

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

[Nick Taylor 2Participant @nicktaylor2]

[KWILParticipant @kwil]

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 GilliganParticipant @michaelgilligan61133]

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

**LINK**

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

MichaelG.

[Ian S CParticipant @iansc]

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 2Participant @nicktaylor2]

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 2Participant @nicktaylor2]

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 CrossfieldParticipant @mikecrossfield92481]

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 GilliganParticipant @michaelgilligan61133]

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 CParticipant @iansc]

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 yetParticipant @notdoneityet]

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 2Participant @nicktaylor2]

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!

[CirclipParticipant @circlip]

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.

[MuzzerParticipant @muzzer]

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 PooleParticipant @mikepoole82104]

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 2Participant @nicktaylor2]

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 GilliganParticipant @michaelgilligan61133]

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 CParticipant @iansc]

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 2Participant @nicktaylor2]

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

[Peter_HParticipant @peter_h]

Sorry to comment to so long after the thread, but I have just found out one relevant thing. The pickoff shaft in the headstock of the Colchester Chipmaster lathe has an oilite type bush at each end. According to the parts manual they have the designation CT18 by 1.1/8″ long. I don’t know yet what the diameters are but one thing stuck out from the drawing – they are flanged…

So this numbering system must some how include that information. Most of the bushes in the headstock are BS68 or BS69, one being plain and the other flanged, but some supplies show both as plain. Also, bushed with the GH identification are FGH flanged and GH plain. If the original poster is still here, were yours plain or flanged?

BTW, a reasonable cost supplier for imperial sintered bushes I have found is Wych Bearings in the UK, for example a AI161816 Oil Filled Sintered Bronze Bush 1×1-1/8×1 BS185-1 is 3.47 ukp.

[old martParticipant @oldmart]

Oilite bushes should not be reamed as the cutting process tends to wipe the surface and seal the pores. As already mentioned, boring with a sharp tool is approved by the manufacturers. One production fitting method was to use a mandrel with a fine ground finish the same diameter as the shaft to be fitted to the bushed end. The bush is slightly compressed when fitted, but no mention was made of the difficulty of removing the fitting tool.

[D.A.GodleyParticipant @d-a-godley]

Have you spoken with HPC Gears at Chesterfield ? ,  they may very likely be able to help you.

 

[Peter_HParticipant @peter_h]

Fully agreed on the reaming, definitely a non starter. In the past I have bored them out with an Aluminium cutting carbide insert with a very high rake angle, sharp edge and 0.2mm radius tip.  Meanwhile, I’ve at least found some info on the BS68 and BS69.

BS68 x 7/16″ long   =  1.1/8″ id x 1.3/8″od x 7/16″ long

BS69 x 1.0″ long    =  7/8″id x 1.0″od x 1.0″ long

 

There is a lot of info in the Chipmaster parts manual, but it is spread through 3 or 4 editions of the same manual. However, no mention of flanged or not anywhere, so I may give HPC a try, thanks. Good to hear they are still going. I remember their tiny but thick catalogue from many decades ago.

[IanTParticipant @iant]

‘CT’ (Copper Tin) part numbers may reference the US MPIF (Metal Powder Industries Federation) Standard 35 which define the % copper/carbon/iron/tin mix of the bearing and other factors such as it’s porosity.

I think that “CT18” probably therefore defines the material grade rather than a specific size and could be either a shortened version of a MPIF number or simply a manufacturing part reference…

Standard Bronze Oillite bearings are MB01-2 grade, which is the equivalent of CT-1000-K26 in the MPIF S35 standard.  I’m pretty sure any good quality sintered bronze bearing will suffice for this use. They do shrink slightly on insertion and are designed to do so.

Regards,

 

IanT

[Peter_HParticipant @peter_h]

Really interesting Ian, thanks. Looks like the salient one is Standard 35-SLB for PM Self-Lubricating Bearings but the only one that is free is Index of all MPIF Standard 35 Materials . There are one or two others in that list that I’ve seen as bush identifiers, such as FG.

I’m happy to use any sintered oilite type bush, the problem is identifying their size and if they have a flange, from incomplete manuals and without disassembling the headstock first. I have 90% plus of a disassembled spare headstock but, of course, the bushes are missing. I would like to refurbish that and “just” swap them over. I think I’m nearly there though.

One useful asset I found in my PDF directory was an old Colchester Lathes parts book. It covers most component types and goes up to whichever lathe used Gamet 140085/140140H main bearing. I’m happy to upload it but there’s a good chance that I got it here many years ago :).

 

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