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Member postings for Andrew Moyes 1

Here is a list of all the postings Andrew Moyes 1 has made in our forums. Click on a thread name to jump to the thread.

Thread: Kennedy hacksaw-main bearing
14/07/2021 21:17:53

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.

Thread: Hoover Motor Lubrication
14/07/2021 20:45:19

Hi Leslie and Chris. I haven’t made the progress I intended on the Kennedy hacksaw restoration. Partly because I hit some snags but I have also been diverted to help my son restore his new flat. However your requests will encourage me to get it finished and take photos.
Leslie - I renovated the Hoover motor first and didn’t take any photos while it was apart. If you have any specific questions I will try to answer them. One thing to note is that there are only three wires in total emerging from the start and run windings. One end of each winding is commoned within the windings and that wire goes to the neutral terminal. The other end of the run winding goes to line terminal and the other end of the start winding goes to line via the centrifugal switch. It’s therefore not possible to reverse this motor – not that you would want to anyway in this hacksaw application.
I'll open a new thread on the issue I had with the main bronze bearing.

Thread: Myford Super 7 with 'Big Bore Conversion'
29/06/2021 08:33:02
Posted by Michael Gilligan on 22/09/2018 08:53:24:
Posted by Alan Waddington 2 on 21/09/2018 23:51:06:

Seems like a great idea, how can large bearings be inferior to a smaller plain bush ? ........

.

The general concept of this conversion sounds excellent, but I have a 'back of the mind' recollection that Myford [Beeston] opined that such a conversion was impractical, because the headstock casting was too small for it.

Things change [including bearing designs]: So It would be very interesting to know what bearings, and what adjustment mechanism, are being used here.

MichaelG.

If I recall correctly, when I studied the photos posted by Roy Milner on eBay, it was apparent that he used his own casting for the headstock, confirming what Michael quoted here. The shape of the casting around the pulley and in front of the backgears was different to standard. Also, the enlarged gear on the back end of the spindle (38T on my Beeston big bore machine) means the fourth gear (after the two tumbler gears) has to be enlarged to 38T too in order to preserve the 1:1 gear ratio for screwcutting. That changes the tumbler lever geometry too. So a conversion will not be easy.

Andrew M

Edited By Andrew Moyes 1 on 29/06/2021 08:36:18

Thread: Burnerd Chuck Jaws
25/06/2021 06:09:32

Jeremy - I've a spare set of unused jaws that I don't now need. Send me a PM.

Andrew Mimg_20210625_055233820.jpg

Thread: Myford MLsuper7
29/05/2021 14:45:32

If it slows down when drilling, on the Super 7 it can also mean the adjustment of the front taper bearing is not correct. It could be that the front bearing is taking the end thrust which it's not intended to do. The thrust should be taken on the back (ball) bearing. The manual describes the adjustment procedure.

Thread: Tapmatic tapping head
12/05/2021 19:55:53

Thank, all, for the info. Tug - that's a kind offer re the manual but I have the leaflet that was supplied with the head. It covers user instructions, diagram, spare parts etc. Studying the exploded view of its inside has convinced me to leave it well alone!

Andrew

12/05/2021 17:14:13

Thanks Andrew. That's reassuring to know. It must be a design feature then.

Andrew

12/05/2021 16:13:04

I have recently acquired a Tapmatic 30x tapping head, supposedly having had only light usage. I am surprised at the amount of side play in the spindle, somewhere around 20-25 thou. Can someone who has owned a new head tell me if this is normal, to allow the spindle to align itself with the hole? Or is mine more worn than I was led to believe? Thanks.

Andrew

Thread: ER32 Collet?
05/05/2021 10:20:42

Bo'sun - Rotagrip in Birmingham sell the Vertex collets.

05/05/2021 10:06:45

Here is the evidence. It's a nice sliding fit on 3/4" stock.

img_20210505_095304375_hdr.jpg

Thread: Myford Super 7 Toolpost issue
05/05/2021 07:54:52

Look up the thread 'QCTP mounting on the Myford S7' and you will see some solutions.

Thread: ER32 Collet?
04/05/2021 18:29:58

I have a Vertex set of metric ER32 collets. They are more expensive than the run of the mill Chinese collets and are supposed to be of better quality. The 19-18 collet is also marked 3/4" so they are not worried about the extra 0.05mm. Opening it up that extra small amount will stress the collet less than closing down a 20mm collet almost a full millimetre but in theory that should be okay too.

Thread: Mt3 extension for tailstock
01/05/2021 23:05:12

I have a '2MT to 2MT adapter' for my Myford. I find it very useful for some operations such as tapping or using small, and therefore short, drills. I bought it from Chronos. I didn't have great expectations for accuracy as it's almost certainly Chinese but was pleasantly surprised. The runout is about a thou. The resistance to lateral forces is not great, as you might expect, but it could support light turning eg clockmaking. It seems fine for axial loads though.

Andrew

Thread: Dore-Westbury mills
01/05/2021 22:51:13

I looked up the construction notes supplied with the Mk1 machine. Arnold Throp said 'A 1/3hp motor is quite adequate for all the work a machine of this kind will normally be expected to do.'

Andrew

Edited By Andrew Moyes 1 on 01/05/2021 22:52:00

Thread: Hoover Motor Lubrication
01/05/2021 16:11:30

The machine was in a generally clapped out condition so I decided to give it a top-to-bottom overhaul, leaving no stone unturned. While I had the motor apart, I changed the bearings, checked the centrifugal switch, stripped off the unsightly hand painting, and resprayed it. The flat belt has been ditched and replaced by poly-vee.

The hexslides are next. Where the slides have worn, I will cut some relief slots across the fixed bars at the ends of travel. This will allow the bow to overrun into the slots (as on loco slide bars), then I'll re-shim the bow.

01/05/2021 12:11:57

Hi Chris. Having just stripped down the 1/6hp Hoover motor on my Kennedy hacksaw, I can confirm they are definitely ball bearings and it should be grease not oil. The bearings are shielded on their inner sides (to protect from dirt and retain the grease) but open on the outer sides so they can be regreased.

I have replaced the bearings in mine and tried to obtain bearings with a single shield but without luck. The original bearings are 6203-Z. I think the suffix Z means one shield and ZZ or 2Z means two shields. Although I carefully ordered suffix Z, they came with two shields. Rather than trying to prise out one shield, I decided to fit them as they were so it is now a 'lubricated for life' motor, a nice euphemism meaning they can't be regreased. They will see me out.

Andrew

Thread: New shaft in Oilite bushes?
28/04/2021 11:46:26

Thank you all for your thoughts. You have persuaded me to take the easy route and use ground silver steel. That’s on order together with the Oilite bushes.

It’s interesting to note that while the original ¾” dia mild steel crankshaft and bronze bushes are badly worn, the much smaller 3/8” dia crankpin which is hardened and runs directly in the cast iron connecting rod is perfect with no play.

I have replaced the motor bearings with SKF ballraces and converted the flat belt drive to poly-vee. The saw should be a useful addition to the workshop when finished.

27/04/2021 14:23:29

Duncan, all the commercial shafting I have seen is metric. Altering the machine casting and pulley to take a 20mm metric shaft and bushes instead of 3/4" is another option but more work.

Re the suggestion to use unhardened EN8, the original unhardened shaft has worn badly, hence why I wanted to do something better. That seemed a good idea at the time but maybe I should just do that and replace it again if and when it wears.

27/04/2021 13:46:01

If I were to use a high-carbon steel instead of carburising, to what colour would you suggest the shaft be tempered?

Andrew

27/04/2021 11:57:30

I too am restoring an old Kennedy power hacksaw and by luck I stumbled across this thread. I have exactly the same problem of a worn shaft and bushings. On mine, the shaft is unhardened. I intend to fit new Oilite bushes and would like to upgrade to a hardened shaft, which I believe is advisable when running in bronze. I can’t find any commercial source of ¾” hardened and ground steel. So I thought I would have a go at turning down some EN3B, carburising it using an old tin of Kasenit I have and then grinding it to size on the lathe with my toolpost grinder. I’m wondering how much grinding allowance to leave. It needs to be enough to correct any distortion but not enough to grind through the casehardening. The shaft is only 4.3/4” long and I will plunge the shaft vertically when hardening it to minimise distortion. My gut feeling is about 4 thou but I don’t have any feel for how deep the carburising will be. Any advice will be gratefully received.

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