Cutlass bearing play

[tyce]

My Cutlass bearing has about 2 -3 mm of play in it, i am guesiing this is a bit excessive but its not a job i really want to do unless required as access to the internal deadwood side is awful.
What do you reckon is it an excessive amount of play?.

 

[Doghousekeeper]

Needs replacing IMHO. (I had a cutlass bearing with similar movement replaced earlier this year - £500 bill, a lot of money but peace of mind)

 

[Neil_Y]

Firstly it depends on the shaft size.

Cutless is a brand name of one make of water lubricated shaft bearing there are many others.

Our water lubricated shaft nearings for a 38.10mm (1.5") shaft would be considered worn and in need of replacement at around 1.00mm play. But different bearing manufacturers run different clearances. Our starting clearance for a 38.10 shaft is an ID of 38.19 to 38.29mm.

2.00 to 3.00 mm play would be considered in need of replacement for a 100.00mm - 125.00mm (4" or 5") shaft bearing that starts at a clearance of around 0.50mm.

 

[Deleted member 36384]

Its Worn - The Designation Should Be "Sliding Fit"

The cutless bearing is normally a sliding fit (H7/g6 = hole to shaft tolerance) on the shaft with no discernible axial play. At least that is how I understand it. At 2 to 3 mm play it is excessive. On a 1" Diameter Shaft the clearance between shaft and bearing is from a minimum of 0.076 to a maximum of 0.178 mm.

It doesn't mean that you will have impending failure, it could mean that, however, you are stressing the shaft and gearbox flange unnecessarily.

Two years ago I had my transmission system replaced and upgraded: shaft, cutless, mounts, thrust bearing. Afterwards, under power, the difference was incredible. However the old system was well and truly shot.

Its worth researching the different types of cutless bearings available. For example you can purchase ones which can be epoxy glued into their housing. This can be useful if you have a worn housing.

I am an amateur, so the above is open to verification and correction.

 

[Neil_Y]

Interesting old boots, is that the clearance for a nitrile rubber water lubricated bearing? we would run 0.06 - 0.16 on composite from new, change at 0.95mm

And now to clear up the cutless cutlass issue hopefully...
Cutless is a brand name (as in hoover) but it has become widely used as the name for a water lubricated shaft bearing, which is what it is. I know this as we were asked to remove references to Cutless from our website bearing information, it belongs to Duramax who developed the nitrlie rubber bearing for shafts to replace wood back in the 30's. It has then been mispelled as cutlass in some cases. But it is just a water lubricated shaft bearing of one design. There are many materials and designs that you can now use, many have demonstrated improvements and benefits over rubber as a bearing material.

Have a search for
Thordon
Railko
Tenmet
Orkot

 

[NickRobinson]

User experiences

Hi all-

There's stuff and pics that a search will show up (as always!)

My bearing had 5/6mm sideways play when I changed it! I'm not recommending such slop, just suggesting that your situation is planned rather than emergency maintenance if no scary noises or vibration.

You may find wear on the shaft as well when you pull it, fortunately my son can weld and turn stainless!

Lakes (no connection) provided a new bearing, £22 inc. and I went for a phenolic backing so I could adjust the fit in the housing.

I used a grub screw and polyester resin to retain. Just lifted after 50 hours plus motoring and all still good.

Nick

 

[vyv_cox]

And now to clear up the cutless cutlass issue hopefully...
Cutless is a brand name (as in hoover) but it has become widely used as the name for a water lubricated shaft bearing, which is what it is. I know this as we were asked to remove references to Cutless from our website bearing information, it belongs to Duramax who developed the nitrlie rubber bearing for shafts to replace wood back in the 30's. It has then been mispelled as cutlass in some cases. But it is just a water lubricated shaft bearing of one design.

I'm quite surprised to hear that. I worked with Weir pumps for several years in developing various high-pressure pumps. They made cutless rubber bearings and referred to them in their literature as those words, all lower case. They advised me at the time that the words describe the manufacturing technique, i.e. the rubber is moulded into its castellated shape, not cut to form it. This results in a bearing that has better fatigue resistance due to the absence of stress raisers. Hence 'cutless'.

Edit: Intrigued by the topic I did some further research and find that Neil Y is quite correct. See here.

 

[Deleted member 36384]

Interesting old boots, is that the clearance for a nitrile rubber water lubricated bearing? we would run 0.06 - 0.16 on composite from new, change at 0.95mm ......

Neil_Y, to be honest I assume that the figure I quoted is for a Nitrile bushing but the table I used does not state the material. The figure is the permissible tolerance at installation, when new. The data came from some information I cobbled together to try and understand the work being done on my own boat. The only clue is that the table probably precedes the general availability of composite cutless materials.

Another assumption I make is that when the whole shaft has play greater than the maximum tolerance then that bearing has worn, but, these journal bearings (cutless) have large length to diameter ratios.

This means that they stabilise the shaft and support the loads far more effectively than a shorter journal bearing and as such make the system far more tolerable to wear, which is a useful feature in hard to get at bearings.

 

[Stemar]

If your bearing is like mine, it's a bit scary, but not actually too bad to do.

Mine is in a bronze casting that's held on the deadwood by two screws. Undoing these doesn't seem to help in getting the casting off and trying to pull it off will give rise to immense frustration and a desire to take up golf. This is because the bolts simply lock the casting. It's actually screwed on to the shaft tube. Once someone told me, unscrewing it wasn't too bad and then it's easy 'cos you can take the whole thing home and work on it in a vice.

I had to use an extractor to remove the grub screw that held the bearing in place, but managed not to wreck it or break the extractor (makes a change) then pressed it out using a suitable socket from the toolbox as a drift. My local chandler was able to order a new one for a sensible price and I used a big G cramp to press it into place.

Good luck!

 

[tyce]

Thanks for all the very detailed replys, looks like this years layup potentially nasty job is the bearing replacement.

 

[Neil_Y]

I'm quite surprised to hear that. I worked with Weir pumps for several years in developing various high-pressure pumps. They made cutless rubber bearings and referred to them in their literature as those words, all lower case. They advised me at the time that the words describe the manufacturing technique, i.e. the rubber is moulded into its castellated shape, not cut to form it. This results in a bearing that has better fatigue resistance due to the absence of stress raisers. Hence 'cutless'.

Edit: Intrigued by the topic I did some further research and find that Neil Y is quite correct. See here.

It surprised me too!
However legally when a trade name becomes a generic name, the company that owns the trade name has lost the ability to protect the use of that name.

Xerox took action to stop people saying they would "xerox" something when meaning they would copy it to protect the xerox brand name.

Duramax has allowed cut less to be used widely and I believe they may have lost the right to protect the use of the brand name. I thought they use the term cut less with regard to the reduced occurrence of abrasives cutting into the shaft material??

We are going to stick with water lubricated journal bearing or shaft bearing as this is what it is. Composites have been used for over twenty years now gradually replacing rubber in commercial and military vessels. there is now an increasing use of composites in smaller boats.