By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Kennedy hacksaw-main bearing

All Topics | Latest Posts

Search for:  in Thread Title in  
Andrew Moyes 114/07/2021 21:17:53
142 forum posts
23 photos

This follows on from the interest shown in my Kennedy hacksaw restoration in the 'Hoover motor lubrication' thread. I hit a snag with replacement of the main bearing and the following is the method I used.

The shaft is ¾” diameter and the bronze bearing is 2” long. I purchase two 7/8”OD Oilite bushes x 1” long, thinking it would be a straightforward job to press the old bush out and new ones in. I then found that Kennedy didn’t follow normal engineering practice by reaming the hole. The hole is left as-cast with a pronounced taper. Their solution was a bush stepped on the outside and driven in from the wide end. The bush fitted the bore with line contact only around two rings, at the narrow end and in the centre.

I reamed the bore 7/8” but only half of the bore cleaned up. I pressed in the first bush and retained the loose bush with Loctite. I cleaned the outside of the loose bush with acetone and used an oil-tolerant grade of Loctite. I also machined a mandrel to align the two bushes, making sure no Loctite came into contact with the mandrel!

For the shaft, I used ground silver steel that was 0.5 thou under nominal size. The two Oilite bushes were also 0.5 thou undersize as supplied. The pressed-in bush contracted a further 1.5 thou.

Reaming an Oilite bush to size is not recommended because it smears the porous bronze and destroys its self-lubricating properties. Instead, I used a technique recommended in an old booklet by a bearing manufacturer. That was to press through a precision ground hardened steel ball. Mine was spot-on 0.750” diameter but due to spring-back of the bush, the shaft still did not enter the bushes. I heated the ball in stages with a blowtorch and used the drill press to force the ball through. It eventually enabled me to get exactly the fit I wanted with a highly polished, truly circular and porous bore.

Nigel Graham 214/07/2021 22:54:03
1712 forum posts
20 photos

I think that burnishing to size by pressing a ball through is still used in some production work, but you may find that doing it to an Oilite will squidge its surface closed as you point out a reamer will.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
cowells
rapid Direct
JD Metals
emcomachinetools
walker midge
Eccentric July 5 2018
Warco
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest