Oils seals, which way to install?

Hi everyone,

For the rotary broaching tool I'm making I'd like to add in a small oil seal at the rear of the tool to act as a barrier against dirt and moisture. Is there a preferred way to install these or does it not matter?

One end of the seal has been reduced into a kind of swaged chamfer. The opposite face has the rubber seal going from the ID, up over the face and all the way out to the OD.

These are 16mm OD to fit a12mm shaft.

Thanks, Ed.

Usually "hollow" side in towards the fluid.

'Fluid' in this case being air so the seal lip and spring would be visible after assembly.

If the shaft is lubricated and you want the oil seal to prevent the oil escaping then the seal lip and spring would need to be on the the oil side.

Ian P

If you think about it, I feel you want the 'hollow' side of the seal to be against whatever you are protecting the other side of the seal from, be it dirt, water, oil leakage out, whatever, so the pressure on the 'hollow' side is pressing the seal tighter to the shaft to resist ingress rather than the other way round, if that makes sense.

Chris

Thank you guys,

There's no spring on the seal, I think because it's so tiny.

I knocked up a quick sketch in Fusion 360 of the cross section.

Ed,
You have not told us much about how this shaft is moving in your rotary broach but there are many different profiles for seals which depend on the application as much as anything. You mention keeping out dirt and moisture and I'm assuming that there is some sliding action with this shaft so is this maybe more of a wiper that you really need and that profile is intended to wipe off any crud that lies on your shaft without wedging it into a taper that compresses it onto your shaft. Google Wiper seals and take a look at the SKF site. There are lots of pdf files illustrating different seal profiles, their housing dimensions and the shaft sizes to say nothing about the various materials that the seals can be made from.
hope this helps you choose the best seal for the job.

Bob D

Ed,

Don't want to repeat myself!

Bob D

Edited By Robert Dodds on 02/04/2016 23:37:50

Hi Bob,

Thanks for the pointers. This will be a rotary tool, so no sliding motion. Here are some more pictures with decriptions.

Ed.

The red coloured section of the larger diameter part is yet to be parted off. I will hopefully be doing this tomorrrow(today). This will leave a flat wall at the back of the tool to take the seal.

The body is made up of 2 brass sections which sandwich and hold concentric a couple of bearings that have been pressed onto the 12mm dia shaft. The brass body and bearings all rotate together around the shaft which will be fixed and held in a QCTP tool holder. ...(I may need to redesign the shaft with a shoulder on it to bear against the bearings).

Once I've parted off that rear section I will need to machine a counter-bore to take the seal. This will be to prevent any dirt etc from getting between the stationary shaft and the revolving body.

Here's a pic showing the rear as it is now with the seal on the shaft. The stepped part is just an existing feature from the brass offcut I used and will be machined off as mentioned above.

Edited By Ed Duffner on 03/04/2016 01:27:21

Beautiful work.

A quick rule for seals: Lip facing in to keep lubricant in, lip facing out to keep dirt out.

You probably want to keep dirt out.

Thank you John

Your seal looks very much like a self energising hydraulic component seal far too sophisticated and expensive to

keep dirt out. A very ordinary HMI 16 x 12 should fit the bill

Nice shiny turning

Michael Wade

Hi Ed

John is spot on can I add a little more. the bearings are rubber sealed so no lubricant on the seal so a dab of grease on the shaft before fitting the seal.

There are "Double Lipped" Seals available with smaller secondary lip to keep dirt out and lubricant in.

Or a felt grommet soaked in oil instead of a modern seal will keep the swarf out.

Eric

In my earlier posts I neglected to mention that there are seals with dual lips. They provide against lubricant loss and exclude dirt. I have not looked at a seal catalog and I know know nothing of what is available in the UK so I can't make a specific recommendation.

Just did a quick search.  SKF and Timken offer oil seals.  They should be available in the UK.

Edited By John Reese on 04/04/2016 02:41:03

Here is SKF info.

http://www.skf.com/group/products/seals/industrial-seals/power-transmission-seals/radial-shaft-seals/index.html

Edited By John Reese on 04/04/2016 02:43:52

Edited By John Reese on 04/04/2016 02:45:12

Add Garlock to the list of sources.

Edited By John Reese on 04/04/2016 03:06:34

The normal rotary shaft seals do not allow for much side-ways movement. It may be better to use a Vee ring seal. They are inexpensive and easy to fit and available from most bearing suppliers. No special machining required. Just press over the shaft.

Paul.

Paul- thanks for that, V ring. I've been searching and could not remember what they are called. Used a lot in the past on agricultural stuff, keep dirt out, also at speed will "fling" out so less friction on the face.

Shout if I'm wrong but my understanding is that the sealing lip goes on the inside so that over-pressure in the oil casing will cause the seal lip to be pushed against the shaft and increase the sealing pressure. In this case as there is no differential pressure I cannot see it matters overly. Think I'd go with John Reese's rule.

Martin

Thanks guys,

I've now completed the tool and installed the seal as per the orientation in last photo I posted above i.e with the chamfer pointing outward.

I was also trying to find a metal type shield to do a similar job because they have less friction but they don't seem to be available in tiny sizes.

Best Regards,
Ed.

Edited By Ed Duffner on 04/04/2016 13:13:01

Really not worth changing your already very good job but for dirt exclusion without friction you would probably have to opt for a labyrinth seal as used on such things as the Quorn Cutter Grinder spindle. Essentially you engineer a convoluted path of ingress to keep the dirt out.

If you choose a labyrinth type sealing arrangement, the "thread" should be of a hand that screws any dirt outwards, (NOT inwards) under normal direction of rotation.

Some lipseals are available with a "thread" on the outer side of the lip, but again, are only effective if the rotation of the shaft moves debris away from the lip.

Metal shields on ball bearings exclude large particles, "rubber" seals (as in bearings with "2RS" suffixes are much more effective in keeping out small particles. Talk to Ketan at Arc Euro about these types of shields and seals.

Howard

Thank you for the info chaps. I think the labyrinth is a bit involved for my skill level at the moment - very clever idea!

I also like the idea of the felt washer. I'll see how it goes with this rubber seal for the moment and how warm the tool gets. I don't think it will be too bad as it would be used interrmittently.

Cheers,
Ed.