Kennedy Hexacut machine hacksaw

[Leo F Byrne 1Participant @leofbyrne1]

The belt disintegrated on my hacksaw, which has been a good and faithful servant. Tony at Lathes was very helpful and sent a belt, It kept slipping and he sent another FOC.

Now it won't cut square. I have managed to tighten the front section with the help of Ian Jamieson – may his name be praised – but the saw won't cut square. I have fiddled about with the hexagonal guides/shim but to no avail.

I was making 1.8 mm discs from 28 mm brass rod, grinding them flat on the disc/belt sander and then slicing them. This is to make discs for the ball dispenser at the golf club – the pro can't buy them. I then machine a slot to fit in the machine.

I have now given up. Has a skilful person got any suggestions?

I make all sorts, but nowadays bows for violin/viola/cello.

Leo

[Leo F Byrne 1Participant @leofbyrne1]

Problems

[peak4Participant @peak4]

In which plane does it fail to cut square, and does the cut wander part way through?
By that I mean, does the cut go off vertically, or is the blade no longer perpendicular to the vertical face of rear vice jaw?
I've just been out to look at mine and it seems that there is no adjustment between the vice and the hacksaw bow itself.

I wonder if your main bearing bushes are worn, and the new belt with extra tension is pulling the man spindle, and thus the blade out of square.

Bill

[bernard towersParticipant @bernardtowers37738]

surely it must be quicker and easier to part them off.

[Dave HalfordParticipant @davehalford22513]

Did you change the blade at the same time? Is it still cutting on the same stroke? My 90 wandered till I used a full size power hacksaw blade, but then it is a much heavier bow.

Half the vice is steel, but the fixed side is only the main alloy casting, is that worn just where the 28mm rod rests?

[Clive FosterParticipant @clivefoster55965]

The bearings do wear, unsurprisingly, that allows things to move off line. The one we had in or little local section trials prep workshop at RARDE had noticeable rock but the saw still cut adequately. Albeit less square than we'd ideally have liked.

Modern plastic faced belts are potential issue as there tend to need both more tension and a higher surface speed to transmit useful power. The saw was designed and developed to use a leather or leather faced fibre backed belt.

if I had to replace the belt on one I'd change the motor pulley to poly-Vee and keep the standard flat pulley. The soft Vee side running on the big pulley will transmit enough power just fine at surprisingly low tension.

Doesn't help that power transmission nis inherently a bit on the marginal side to so the drive slips if the blade jams up rather than break. They were designed for site work where a certain degree of careless handling is inevitable.

Clive

[Leo F Byrne 1Participant @leofbyrne1]

I can't part off well enough on my ML7. I am just a violin/bow maker so at the lower level of engineering ability – though I do good work on bows.

I think a poly-Vee belt sounds like the way to go. Current driving pulley 21.3 mm o/d, 16 mm i/d, driven pulley 150 mm o/d.

Can belts be had in different lengths?

Or should I buy a portable machine hacksaw – Scheppach – from Screwfix and put it on its stand.

[vic neweyParticipant @vicnewey60017]

This is just for belt slipping if you get further problems

Have you got the instruction booklet for it and how are you fitting the belt? You may have to loosen the two bolts near the front and pull it forward and tighten it, then put the belt on the motor pulley and then start feeding it on the big pulley and turn it as it forces the belt to follow. it will then try to move off the motor pulley so tap with a soft hammer and continue forcing the belt on, that's what the instructions say.

I can scan the instructions if you haven't got one

 

Edited By vic newey on 08/08/2023 17:50:32

[Howard LewisParticipant @howardlewis46836]

Assuming

The belt is the correct length

The belt is the correct section for the pulleys

If the belt slips, the pulley grooves may be worn, allowing the belt to slip down the groove and bottom out rather than grip on the sides of the groove.

And obviously, the tension needs to be correct (Again, there will will be difficulty setting the correct tension if the belt is too long, or overtight if too short.&nbsp

It won't help, if the bearings are worn allowing the pulley to wobble

Nor is it likely to cut quare, or repeatably (Not talking high precision her ) if there is play in the bearings for the actual hacksaw frame, or the guides for it.

If there is play in the bearings, or shaft can they be bushed, or the shaft removed and turnded down until cleans up and then make bearings to match, sat a thou or two clearnce , maximum)

If the guides are circular, any chance of bushing, turning down, or replacing the guides and the making suitable bushes?.

As each element of wear is reduced, / eliminated, so overall accuracy will improve, until it reaches a level that is acceptable..

Rightly or wrongly, I don't regard bandsaws or power saws as precision instruments, but properly set up in good condition, surprising accuracy can be acchieved from time to time.

Howard

[Michael GilliganParticipant @michaelgilligan61133]

I believe that the belt on the Hexacut was flat, Howard … Hence Clive Foster’s excellent suggestion.

MichaelG.

.

Ref. __ http://www.lathes.co.uk/taylor/page2.html

Edited By Michael Gilligan on 08/08/2023 19:19:58

[peak4Participant @peak4]

Yes PolyVbelts are readily available in different lengths and widths, but like any other flat belt, the spindles do need to be parallel to each other to work well.
This is just  one of many suppliers
https://simplybearings.co.uk/shop/Belts-Multi-Ribbed-Poly-V-Belts/c4601_4791/index.html

Since Leo has an ML7, it should be easy enough to grind up a tool and make the appropriate grooves.

The outer circumference of the flat belt on my Hexacut is about 21½", and Simply Bearings seem to list both 20" & 21", so something should be suitable.

Bill

 

Edited By peak4 on 08/08/2023 20:23:48

Edited By peak4 on 08/08/2023 20:28:15

[Graham MeekParticipant @grahammeek88282]

I recently acquired a Kennedy 60 and one of the things I have wanted to do with it is replace the rather aging drive belt.

I have just drawn up the pulleys and pulley centres. The belt comes out at 535 mm and the nearest to this is 533 mm or 21" , belt number 210J10. I will be placing an order shortly for this and a few other things so I will let you know how I get on.

Regards

Gray,

Unwanted graphics

Edited By Graham Meek on 11/08/2023 15:53:58

Edited By Graham Meek on 11/08/2023 15:54:47

Edited By Graham Meek on 11/08/2023 15:55:21

[john halfpennyParticipant @johnhalfpenny52803]

How about using a poly vee belt inside out, ie driving on the flat side. I've seen this done on slightly larger machines, but the motor pulley of the Hexacut may be a problem because of the small radius?

[Graham MeekParticipant @grahammeek88282]

I intend to use the Poly V on a grooved pulley on the motor, but with the ribs running on the larger pulley with no grooves. The large angle of lap should more than compensate for the lack of grooves. Further my current lathe will not swing this size of pulley.

The ultimate aim is to reduce the loading on the Saw bearings which wear quite considerably when using the current set-up. The other plus point is it should stop the smaller pulley from slipping. As well as stopping the belt from running off this pulley due to the above shaft mis-alignment.

It is possible using the Grooved motor pulley to go slightly smaller, as the minimum pulley size for this belt is 18 mm diameter. This however would mean a smaller belt and a reduced number of cutting strokes per minute.

The cost of this conversion as well as new Oilite bushes comes in a good deal cheaper than the replacement flat belt.

Regards

Gray,

[Graham MeekParticipant @grahammeek88282]

Well despite actually measuring the saw twice and drawing things out the belt above arrived today and it is too short. Thus it is back to the drawing board and order a longer belt. When I hit the right one I will let you know.

Regards

Gray,

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Graham Meek on 12/08/2023 11:02:48:

I intend to use the Poly V on a grooved pulley on the motor, but with the ribs running on the larger pulley with no grooves. The large angle of lap should more than compensate for the lack of grooves. […]

.

Very common practice on Tumble Driers … for obvious Production-Engineering reasons

MichaelG.

[Graham MeekParticipant @grahammeek88282]

Hi Michael,

The Washing machine drive was what I had based my drive on. If it works for Hotpoint it will work for me.

Regards

Gray,

With regard to the drive belt I must own up to having had Brain fade. Checking the drawing again yesterday I had measured the inside of the belt and not what might be called the crest of the inverted Vee, which is 1.8 mm above the inside of the belt measurement.

This dimension in round numbers is 555 mm which is 4 mm short of the next size up 559 mm or 22". This belt arrived this morning and all it requires is a slightly larger pulley at 30 mm diameter. As opposed to the original 22 mm diameter. It will mean a few more strokes per minute but I can live with this.

Hopefully I can post some photographs later this week of the conversion.

Regards

Gray,

Edited By Graham Meek on 16/08/2023 15:13:26

[Graham MeekParticipant @grahammeek88282]

Last night just before I turned in for the night. I had a sinking feeling that the new larger pulley would not fit inside the existing Kennedy Belt Guard. A quick look this morning allayed my fears. During today I have managed to manufacture and fit the new pulley and belt.

I chose steel for the pulley, but with hindsight aluminium would have been better. As the Compact 5 was not impressed with the 2 mm deep Vee grooves in one hit. In the end I worked out a routine which used four cuts, two of which were off-set and formed the width of the groove at the top of the Vee.

There was a bit of a setback with the Phos Bronze bearings. I think they were inserted when the main body was cast. They did not want to budge when using a puller, and the only way these are likely to come out now is by boring them out.

However the saw works fine with the new belt and I have so far tested it on 25 mm Mild Steel. I did also try using an 18 TPI blade which the saw easily took in its stride. Even though the manufacturer states 24 TPI blades on the machine plate. Tomorrow I have some 40 mm square aluminium to cut up so we will see how it performs on this and maybe get some photographs.

Regards

Gray,

Edited By Graham Meek on 17/08/2023 19:33:28

[DMBParticipant @dmb]

Gray,

I once took a tatty belt to some supplier in Brighton and Hove area for a replacement and the guy produced a board with 2 pulleys mounted on it. One was moveable, allowing adjustment to make any belt fit tightly. He immediately told me what I needed by reading off Mark's on the board. Maybe a lot of suppliers use something similar.

John

[bernard towersParticipant @bernardtowers37738]

I remember that item in Parks Pumps in Norwich from the 60s and 70s and if I remember correctly it was made for FERODO.

[Graham MeekParticipant @grahammeek88282]

Hi John, & Bernard,

I have seen this type of fixture at my local bearing factors many years ago, but this was explicitly for standard Vee Belts. Not the multi-ribbed Poly V belts. Please correct me if I have got this wrong.

Regards

Gray,

Generally,

Poly Vee belts are a whole new ball game for me. As far as I can make out the length of the Poly V belt is buried inside the thickness of the belt. For the J section belt that I used this belt length is 1.8 mm from the inner surface. At least this corresponds to what I have drawn out. I have also cross-referenced by measuring the actual, versus designed centre distances of the pulleys on the Saw after conversion. This has come out within 0.25 mm of the designed dimension. Thus I am pretty confident this is how the belts are measured. Of course I could be completely wrong and this is just a fluke.

As always am prepared to learn from anyone with more knowledge on these belts.

Regards

Gray,

[mgnbukParticipant @mgnbuk]

If it works for Hotpoint it will work for me.

The polyvee belts used on tumble dryers are not the same construction as "standard" belts – they use a slightly elastic tension member to make the belts "stretchy"

The reason I know this is that a company I worked for modified the "belt building" machines used to make the belts (by a company in Wigan) to have a closed loop tensioning arrangement to wind on the tensioning cord, which had to be applied at a specific tension to get the correct stretch required. Normal belts used a non-stretch cord.

The stretchability may have been to enable the removal of a separate tensioning mechanism ( engineering by accountants ! ) & the installed tension was high. Tumble dryer installations used grooves cut directly into the motor shaft (around 12mm or so diameter IIRC) & a large diameter plain face "pulley" on the rear of the drum, giving a very large gear reduction.

Polyvee belts in general require a lot of tension to work correctly & wear fast if under tensioned – the amount of wear required on the flanks of the vees isn't much before the belt just ends up driving (more likely slipping) on the points when they hit the bottom of the grooves.

Can't say I am a fan of polyvees though, to be fair, the installations I designed them into were normally "challenging" and where a traditional vee belt solution would not fit the space available.

Nigel B.

[Leo F Byrne 1Participant @leofbyrne1]

Thank you for all your help. Pro tem I have bought a Scheppach bandsaw from Screwfix and, after fettling, it it does what I want, viz making brass discs for my friend the golf pro to use in the ball machine. I didn't realise how much I relied on the Kennedy.

I had a big metal bandsaw years ago but could never get it to do what I wanted and sold it. The Scheppach now cuts square – and quickly! – and the job is now done.

I will revisit the Kennedy at a later date, probably with v-belts. Having reached a dead halt had prevented me from getting on with other projects of a more important nature – including viola bows.

What a great site this is!

Leo

[BufferParticipant @buffer]

Posted by Graham Meek on 11/08/2023 15:52:23:

I recently acquired a Kennedy 60 and one of the things I have wanted to do with it is replace the rather aging drive belt.

I have just drawn up the pulleys and pulley centres. The belt comes out at 535 mm and the nearest to this is 533 mm or 21" , belt number 210J10. I will be placing an order shortly for this and a few other things so I will let you know how I get on.

Regards

Gray,

Unwanted graphics

Edited By Graham Meek on 11/08/2023 15:53:58

Edited By Graham Meek on 11/08/2023 15:54:47

Edited By Graham Meek on 11/08/2023 15:55:21

I could never get the two pulleys parallel on my saw so the belt just kept coming off.   Its been dumped under a bench for years now.   

 

Edited By Buffer on 18/08/2023 15:29:47

[Graham MeekParticipant @grahammeek88282]

Hi Buffer,

The common fault with this machine, and it is down to wear in the crank bearings. The crank pulley automatically swivels clockwise due to this wear and in doing so sheds the belt. This wear is due to the high tension required by the original flat belt. With my muscle illness I struggled to get this belt on and off. When the saw is set-up correctly according to the manufacturers data.

Also I have seen that some saws have motor pulleys with 16 mm bores running on 5/8" shafts. How this ever worked from new I will never know.

The Poly V has very minimal tension when compared to the original set-up. I had the machine set-up and running in under 5 minutes. With the belt running dead centre on the larger pulley rim.

Regards

Gray,

[Author]

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