Fix for Oversized Bores

Loctite works in the field

Thanks for the reply. The parts will go to 20 different locations and my customer does not want the techs to have to mess with the Loctite.

Not a lot else will stick to anodize. You'd also need to prime.

I'm presuming this was meant to be some level of press fit.

Depending on the duty, the part shape [and everything else not mentioned] you may be able to internally knurl, externally crimp, or point stake, or bore and insert, or shim, or ....

Or send them out with bearings loctited in

Or remake them - [possibly at the anodiser's expense, if they were over-etched].

I would consider using the gel type super glue, or the two part epoxy adhesives and installing the bearings while wet. Wiping off the excess, and not allowing any to get in the bearings.

These guys might have something you could use...

http://www.caswellplating.com/

Ceramic coating might work well...

http://www.ceram-kote.com/products/ceram_kote_product_line.htm

Thanks SolarEagle, I will talk to the company about future situations. Good info.

Aside from compromising the Anodize, I'd second the suggestion. But if that's not an issue, Knurl and re machine.

We used to do pump shafts that were undersized that way. It'll work the same on ID's.

This is assuming that the bearing was intended to be a press or interference fit.

Thanks for the responses.

The bearings should be 0.0001 to 0.0003 press fit. When we machine the parts, the bearing bores are machined on the first set of operations. On the second set of operations the part gets cut-off and radiused. At this point there is not any way to hold onto the part for further machining operations, that prevents me from knurling or sleeving them, unless I come up with some type of internal hand knurling tool that can be precisely adjusted.

Normally I would just send the parts to scrap and fight with the anodizers, but I have to get them out tomorrow. That leaves me in a lot of trouble.

Thanks,

dgibson

I know of two choices. One is to overbore the hole and drive a sleeve into the new hole. This will give you the tightest control over the problem because you can drive in the sleeve and rebore the hole to the exact size you need.

The second method is a bit trickier, but have the parts stripped of their anodizing and have them reanodized using Type III hard coat anodizing. Type III is a much harder and thicker coating on the aluminum.

The downsize is controlling the exact thickness of the anodizing may be difficult. I would consult with your anodizer and see what they are capable of doing.

While your bore is cited as being .001" oversized, you did not state what the desired diameter was and to what tolerance you need to maintain. Since you only cited three significant digits maybe the hard coat Type III coating will be good enough.

You could try and knurl the outer surface of the bearing and ignore the part with oversize anodized bore. The bearings are readily set up on a spigot turned true in the lathe and left there. Watch out you don't brinell the races.

Or you could lacquer the outer surface of the bearing. Using Molybond 122L dry-film lacquer includes MoS2 particulates in the coating and maintains your engineering credibility :)

Mark Bingham
Relativity PL

Good luck knurling or lacquering a 608-ZZ

Hi dgibson:

I had this type of experience. I had a John Deere farm tractor with a self aligning bearing, on the drive shaft, that got loose in the housing. I had greater over bore than yours, though. I used a 12 volt battery grounded to bearing housing and a stranded copper wire connected to the other battery terminal. By scratching the stranded wire on the housing, dots of copper were welded to the housing. By spending some time placing copper dots everywhere in the bore, the bearing can be forced into the bore. This compressed the high spots and make the bearing tight in the bore. Smaller wire makes smaller dots. It lasted for many years.

Clark

I believe that anodized surface is electrically non conductive.

If Loctite is too messy then how is any other adhesive or filler any less so?

Another mechanical fix is to introduce interference in the socket using a hammer and centre punch.

DON'T ignore Loctite special products for cylindrical fitting. Henkel/Loctite has a line of products for cylindrical fitting problems.

I always worry when someone refers to Loctite in a generic fashion. Please search under cylindrical fitting , they have several solutions and case studies.

I think that USA is still using Inch and not mm.

But when you say in field but don't say about the part and size of it how anybody can give a valid suggestion.

There are various solutions as suggested already e.g. fitting a sleeve and rebore, anodiizing ...

Bring up the facts and good relative replies be there.

I am out of touch due to age but remember of boring the worn-out threads and fitting a coiled type insert and re-Tapping the thread. Was a Repair kit having all tools and inserts and accessories.

For a under-size bearings tried successfully with shims.

These were the temporary repairs in field, not in base stations.

Problem Solved:

We ended up making a fixture to hold the parts on a rotary table on the mill, made an internal knurling tool, and were able to achieve the desired results.

I sure appreciate everyones responses.

Thanks,

dgibson

I have voted nick name's good answer a GA, since he was the first to suggest it.

If this is a skate application, you may find the knurling, in time, will hammer flat.

It may be an idea to prepare for some warranty issues - and obviously re-tolerance as necessary with regard to etching in anodising.

Actually it is supporting a small auger. I don't anticipate any problems.

Thanks,

You don't mention the wall thickness of the tube. One solution might be to deform the tube with a special die. You may be able to radially shrink the ID to obtain the required fit. You can also create radial pressure with magnetic forming.

I'm glad that worked out for you. I'll remember that.

I had to look it up and did find this ready to use internal knurling tool. http://www.formrolldie.com/serv03.htm

"This type of tool is often used to repair parts with holes that are slightly oversize...."

Did your tool end up looking just like this example?

You really want to let folk know what type of facilities you have ready access to. Makes it easier to make recommendations.

GA to nickname in #5 for getting it right first hit.