Kennedy Hacksaw bearing replacement

[Graeme DurantParticipant @graemedurant1]

Thanks Adrian – more confirmation! And yes, my base casting holes are oval.

Still begs the question why someone put an oversized but too short a bolt in the main casting by force or design….

Graeme

[AdrianRParticipant @adrianr18614]

Brut force and ignorance?

[Dave HalfordParticipant @davehalford22513]

Don't forget these were made for black iron pipe, conduit or scaffolding fitters to carry around. Any repairs required on site would have been basic

[CymroParticipant @cymro]

I bought a Kennedy saw last week from an advertiser on Facebook Marketplace. The description said that it was 'in need of TLC . . . It was only 10 minutes drive away so I went to see it, a small amount of money changed hands and I went home to examine my spoils.

Everything was locked solid so I started stripping bits off and freeing and cleaning them up until I got to the crankshaft which really was frozen solid. Nothing ventured, nothing gained so I got a big spanner on the crank and gave it a good heave. It let go with a crack and suddenly everything was moving. I removed the crankshaft and found 4 rusty needle roller bearings which had seized up in their cages so I took them out and had a squint at them with a loupe to find their part numbers, found them through a Google search and ordered replacements that same evening.

They turned up yesterday in the post and I set about fitting them. I wasn't sure how deep they were fitted in their housings; should they be butted up against each other to prevent any sideways float of the crankshaft, or should there be a clearance between them, I wondered . . . ??? So I Googled, 'Rebuilding Kennedy Hacksaw' and ended up on this thread. Imagine my surprise though, when I saw the description of the plain bearings everyone else was using . . .

Looks like mine has had some major alterations – the housings have evidently been line bored to take 1" OD caged bearings and I can see that they would work well without wearing out as others seem to have done.

Meantime, I've cleaned all the alloy mange off the parts and painted them ready to put it all back together. When I stripped the saw, the belt was actually stuck to the pulley so I'm going to need a new belt. I'm interested in using a poly V-belt and wonder if anybody can suggest where I would find a belt with an internal diameter of 533 mm as best I could measure it?

TIA for any help

[oldveloParticipant @oldvelo]

Hi Bill

"I think I'll probably devise a conversion using a poly V belt drive, but I'm not sure if I will be able to get a low enough drive ration in a single stage"

Any ratio with the flat belt as on th Kennedy Hacksaw can be replicated with Poly Vee Belts.

Machine the motor pulley with grooves on the centre line of the driven pulley. Machining grooves in the large diameter pulley is optional as the drive will work without the .grooves. and self centre on the crowned pulley.

Being Poly Vee Drive addict anything I build that is belt driven is with Poly Vee Belts fitted

Eric

[CymroParticipant @cymro]

I bought a Kennedy saw last week from an advertiser on Facebook Marketplace. The description said that it was 'in need of TLC . . . It was only 10 minutes drive away so I went to see it, a small amount of money changed hands and I went home to examine my spoils.

Everything was locked solid so I started stripping bits off and freeing and cleaning them up until I got to the crankshaft which really was frozen solid. Nothing ventured, nothing gained so I got a big spanner on the crank and gave it a good heave. It let go with a crack and suddenly everything was moving. I removed the crankshaft and found 4 rusty needle roller bearings which had seized up in their cages so I took them out and had a squint at them with a loupe to find their part numbers, found them through a Google search and ordered replacements that same evening.

They turned up yesterday in the post and I set about fitting them. I wasn't sure how deep they were fitted in their housings; should they be butted up against each other to prevent any sideways float of the crankshaft, or should there be a clearance between them, I wondered . . . ??? So I Googled, 'Rebuilding Kennedy Hacksaw' and ended up on this thread. Imagine my surprise though, when I saw the description of the plain bearings everyone else was using . . .

Looks like mine has had some major alterations – the housings have evidently been line bored to take 1" OD caged bearings and I can see that they would work well without wearing out as others seem to have done.

Meantime, I've cleaned all the alloy mange off the parts and painted them ready to put it all back together. When I stripped the saw, the belt was actually stuck to the pulley so I'm going to need a new belt. I'm interested in using a poly V-belt and wonder if anybody can suggest where I would find a belt with an internal diameter of 533 mm as best I could measure it?

TIA for any help

[Ex contributorParticipant @mgnbuk]

Tumble dryers and washing machines use very small drive pulleys with fairly extreme wrap around, spring-loaded adjusters and ony 16-20mm polydrive belts as I recall.

Some domestic machines use a stretchable poly-vee belt & do away with the tensioner. The grooves for the belt are ground directly into the motor shaft & the drum is plain (no grooves), so they operate much as has being suggested for the Kennedy modification.

At my previous employment we modified some of the belt building machines at a belt manufacturer to make the stretchable poly-vee belts for tumble dryers, adding a closed loop tensioner to apply the stretchable cord at a preset tension onto the rubber base layer. Normal belts used a different, non-stretching, cord – Kevlar IIRC. The belt building machines were modified manual Binns & Berry centre lathes that were converted to basic CNC operation, the cord being applied using the screwcutting cycle to get the required cord spacing.

The belts were manufactured as tubes about 2 metres long which, after vulcanising, were slit into the required width belts on another modified lathe that had Stanley knife blades mounted on the toolpost.

The issues I had when designing poly-vee drives were mainly due to the tension required to get them to drive properly without wearing out too quickly. Inadequate tension lead to the flanks of the vees on the belt wearing and, due to the narrowness of the vees, they soon bottomed out in the grooves and slipped. Short centre distances didn't help either, reducing the contact arc on the smaller pulley. High belt tension + plain bushes = likely short bearing life !

The OP's comment about the original belt not being very flexible suggests that it is old. The Kennedy I inherited from my father was incomplete & didn't come with a belt. I mangaged to get a new replacement from the bearing supplier we used at work & my recollection is that it was very flexible. Can't say how it performed, though, as I found one of the Taiwanese 6×4 bandsaws locally in a small ad & refurbished that rather than the Kennedy, which was subsequently sold still incomplete. From memory the replacement flat belt was some sort of plastic compound & was green on the outside & yellow on the driving side.

Nigel B.

[Dave HalfordParticipant @davehalford22513]

from Lathes.co.uk

They charge £26 for a belt + tax and post.

For the more-common Kennedy "Hexacut" Model 60 hacksaw the flat belt is normally 1" (25 mm) wide and 21.8" long (554 mm)

Yours may be different

[Author]

Posts