Cam bushing clearance

[Jack_Hester]

From time to time, I run across a situation where a new cam bushing is too tight for one or more cams (Harley Flatheads). The usual thing for me to do is press it out, shave the face in the lathe, press it back in, and repeat the clearance check. I am having a cutter fabricated to do the shaving on the installed bushing. What are your ideas or practices on resolving tight clearances on these bushings? Thanks.

Jack

[JURIS R.]

Cam bushing clearance

I have found that by using Aluminium Oxide Flex-Hones it is easy to precisely enlarge the existing bronze bushings to the required size. Very good on piston pin bushes in rods as well. Even the final finish honing in case- hardened big ends leaves cross-hatch for oil retention. You have to wash the abrazives away with hot detergent -- water solution. If applying in a dead end -- you may require scraping the very end of the bush as the abrasive globules of Flex-Hone may not work at the very end. The surface has a cross- hatch pattern -- very good for oil retention. The process may be slower than skimming in a lathe, but you do not have to remove the bush and you can open out the bushing very precisely without having to guess the contraction, etc. More information is available from the Brush Research Co. -- a US company.

www.brushresearch.com

Juris R.

[Jack_Hester]

Juris R. -

My issue was not with the I.D. of the bushing. On occation, I run into a batch of aftermarket bushings that have the shoulders too thick. So, I had a tool made to shave the surface down on these shoulders, and get the correct clearance without shims.

Jack

[AdminGuy]

Isn't that why they make them thick? So you can cut them down to your spec. on a mill/lathe.

Post a picture of your new tool when you get it cut.

[Paps]

Hi Jack, I suggest mapping out all your dimensions before installing the new bushings. Beginning with the gear cover bushings the proceedure would be to use a good straight ground on all sides machinist parallel laid across the gasket face of the cover. From this parallel you would depth mic down to the cover bushing bore shoulder where the flange of the bushing seats. The measurement you get minus the width of your parallel and squished cover gasket thickness would be the actual interior dimension from the gasket surface to the cover bushing bore face installed. Then do the same with the case half side bushing bores. Add these two dimensions together. This represents the actual interior measurements of the assembled case half and cover. Next mic all of your cams accordingly from shoulder to shoulder where they run against the bushing flanges and include the endplay shims you will be using. These dimensions will be the linear dimensions of the cams inside the assembled case half and cover. If the cam and cam component linear measurements are longer than the case half interior measurements you will know how much to face off of the bushing flanges ahead of time before installation. Hope I simplified this enough cause it sure confused me. Paps

[Jack_Hester]

Picture of Bushing Facing Tool

The file is 176K in size. Larger than the max size allowed. Send me an email and I will reply with a couple of pics.

Jack

[brucem]

cam bushings

Jack,I don't have a micrometer or catalog in front of me,but it seems to me, my first thought is to use a counterbore tool, these are available thru MSC, Travers,Enco, etc.

[Jack_Hester]

BruceM -

Wouldn't a counterbore have a taper to it? The tool I had made has no taper, and refaces the surface of the bushing to a flat, smooth finish as it removes metal for clearance.

Jack

[brucem]

cam bushings

Jack,the counterbores I have used were straight,possibly you had a reground one-that is a common problem on gregrinds. Another thought-place bushing in collet or chuck on a lathe and face off before installing. Regards Brucem

[Jack_Hester]

Actually, this was a new manufacture, to my specs. I sent them a drawing of the physical size of a standard bushing, and they made the tool from scratch.

Jack

[Mike L]

Lap it?

I haven't tried it yet, but if it isn't too much to take off, what if you used lapping compound using the cam itself in a drill? Just a thought if you don't have readily access to a mill.

[Jack_Hester]

Mike L -

Please don't! You'll be taking metal off the cam. Bushings are easy to replace. Cams cost more, and originals in good shape are not that plentiful. Use a reamer.

Jack

[papereng]

Sizing Cam Bushes

I think you guys are talking about 2 different things? The flange being too thick would affect the end clearance of the cam axially. That sounds like the "counterbore" tool isn't a bad idea to me.

The ID being too tight can be sized with a ball bearing before installation on a blind bushing, and in place on a through-bored bushing. Push (press) a ball bearing with the correct diameter through the bush to burnish the bore to size.

On my old Triumphs, I use the ball to size the timing side thru-bushing, and then a reamer to line / size the drive side blind bush using the timing bush for alignment. My cam bushes aren't flanged so I don't have the other situation.

The ball bearing trick works pretty good.

[T. Cotten]

I'm all for burnishing! But balls don't come in the sizes of worn shafts, or many of the journal sizes of HD gearchests.

Lapping inbeds abrasive in bronze, so I try to avoid that as well.

I love my ALOX brushes, but they are only a final plateau finish.

The end-play bind is one where I would rather draw-file, or cut with a piloted counterbore bit, than work a bushing in and out. Especially since I like to pin them before I fit them, as the dowel distorts them.

With regard to the fit to the cam journal, I find a felt-tip marker and a sharp triangular scraper easily relieves most 'pre-fit' bushings of burrs and minor distortions from the pressing procedure.
A hone or reamer removes unnecessary metal to achieve "straight", whereas the skilled eye and hand can do it selectively with no set-up, and retain more bearing surface for a sweeter fit.

Low tech rules.