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Old 22-11-2017, 09:36 PM   #391
350TSS
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Today, fork leg bottoms got cleaned up and packaged up to go to Maxton’s. That took a couple of hours
I then thought I would try and reverse the jaws in the three- jaw chuck on the lathe to take the 3.25” bar. Took me a while to realise the scroll gear inside the chuck is a spiral and the jaws will only engage with the gear teeth one way, then it took me a little while longer to realise that the jaws only close up completely if the jaws are replaced in their intended slots. Every day is a school day! The jaws and the chuck itself now have register punch marks.
My options for machining the bar are therefore the 4-jaw chuck or the plate with 4 sliding teeth. I spent a good hour and a half not managing to centralise the work piece in the 4-jaw chuck. Whichever way I adjusted the jaws, I always ended up with a runout of about 3mm on the end of the bar (about 150mm long). The run out was always in different places as I used a felt pen to highlight the high point and slackened off the jaw(s) opposite, when I tightened up again (from the high spot side) the high point had moved somewhere else.
I will have to buy some form of clamp to hold a dial gauge when I eventually get the bar square enough to finely adjust it but I would be pleased with a 1mm run out but I am nowhere near that yet. This does not bode well for turning the work piece round and machining a bearing cup from the other side.
I gave this up as a bad job and spent an hour or so vacuuming the garage.
P.S. while writing this I thought I will give it one more go and I have just been down to the garage and I managed to set the workpiece in the jaws with about 0.25mm run out. The trick I used was to wind the tail stock centre hard against the workpiece forcing it flush with the face of the chuck before tightening the jaws, measuring the projection of the jaws from the drum of the chuck with a Vernier caliper
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Old 23-11-2017, 12:25 AM   #392
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What are those two green things on the shelf above your lathe ?
Might one or both of them be a "steady" ? (if so, it'll have three, threaded thingies pointing inwards.)
This can be fitted to the lathe bed and used to centralise the wayward end of the barstock while you centre-drill it.

I would be very wary of parting off anything that big in diameter.
Parting off is a dodgy process at the best of times, and worse if there is much backlash in the cross-slide screw.
The forces are huge, friction is high and, for a large diameter, the tool has to be long so its rigidity is compromised.
Even for smaller diameters, the tool needs to be set dead on centre height (or even slightly above, a heresy in normal circumstances) otherwise the tool will want to drag itself under the workpiece (made worse by cross-slide screw backlash).
Its useful for batch production but for one-offs I would just get the hacksaw out and take a deep breath.
But I would get as clever as I could in the turning operations so as to leave a smaller dia to saw if possible.
And/or I might part off to a shallow depth with a short, rigid tool, just to take some meat out of the work and also to guide the hacksaw.
For this dia, I would hacksaw in 4 or 5 different positions, to meet in the central bore.
Its almost impossible to leave a good face after parting off anyway, so you'll probably have to skim the back face afterwards.
And I would seek to arrange things so that I bored ALL of the bearing diameters/faces without disturbing the workpiece in the chuck, for concentricity.

The dodge with using the tailstock to help centralise is a nice little sign of intuitive skills btw.
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Old 23-11-2017, 12:29 AM   #393
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Oh, and I told you the 3-jaws wouldn't go in backwards.

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Old 23-11-2017, 11:44 AM   #394
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What are those two green things on the shelf above your lathe ?
Might one or both of them be a "steady" ? (if so, it'll have three, threaded thingies pointing inwards.)
This can be fitted to the lathe bed and used to centralise the wayward end of the barstock while you centre-drill it.

No idea – came with the lathe but your suggestion looks probable but they are too small for 3.25” bar


I would be very wary of parting off anything that big in diameter.
Parting off is a dodgy process at the best of times, and worse if there is much backlash in the cross-slide screw.
The forces are huge, friction is high and, for a large diameter, the tool has to be long so its rigidity is compromised.
Even for smaller diameters, the tool needs to be set dead on centre height (or even slightly above, a heresy in normal circumstances) otherwise the tool will want to drag itself under the workpiece (made worse by cross-slide screw backlash).
Its useful for batch production but for one-offs I would just get the hacksaw out and take a deep breath.
But I would get as clever as I could in the turning operations so as to leave a smaller dia to saw if possible.
And/or I might part off to a shallow depth with a short, rigid tool, just to take some meat out of the work and also to guide the hacksaw.
For this dia, I would hacksaw in 4 or 5 different positions, to meet in the central bore.


Its almost impossible to leave a good face after parting off anyway, so you'll probably have to skim the back face afterwards.
The width of the hub needs to be 20mm, the ODs I need are 73mm for 10mm and I will be down to 50mm at the other end for 10mm length, the bar size is 82.5mm (3.25”) so I will machine the 73mm dia first for 26mm. Then about 11mm from the end (allowing for a facing cut) I will machine down to 50mm for about 15mm allowing for facing and tool width for parting off and I will insert parting off tool for maybe 10mm cross cut leaving me about 30mm to hacksaw and a reasonable guide for my not very accurate hacksawing abilities. Does that sound OK to you?


And I would seek to arrange things so that I bored ALL of the bearing diameters/faces without disturbing the workpiece in the chuck, for concentricity.
This is a very good point and I will need to change the design I was contemplating. The original fixed brake hanger is 20mm thick at the axle and is clamped by the spindle being done up. I need therefore to end up with the outer edges of the bearings in the hanger hub at 20mm with the inner race also being clamped when the spindle is tightened.
On the bearings I bought the outer race is flush with the inner race, they are 7mm wide, so I originally intended to machine from both sides leaving a 6mm wide step for the bearings once inserted to butt up against. There is no danger of a clash between the wheel bearing outer track and the inner hub bearing. I may have to have a shim on the swinging arm hub bearing (same OD as the inner track) to prevent contact between the outer race and the swinging arm.
Machining from one side only will not permit this step so I shall make a steel spacer the same bore as the spindle and the same thickness as the inner race of the bearings. The outer track of the bearing will now have to be an interference fit in the hub to prevent the caliper mount walking sideways under load into either the wheel or the swinging arm. If I do not end up with a good interference fit i.e. a bit too sloppy, there is always bearing lock or I could grind a small notch on the outer track of the bearings and drill and tap a 3mm grub screw radially (or both)


The dodge with using the tailstock to help centralise is a nice little sign of intuitive skills btw.
Desperation makes you innovate
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Old 23-11-2017, 12:10 PM   #395
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If you haven't already, try one of these http://www.arceurotrade.co.uk/Catalo...e-Tool-Holders It makes parting and grooving far smoother than a traditional blade
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Old 23-11-2017, 11:21 PM   #396
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Slob: I will investigate - I love buying tools even if I do not know how to use them
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Old 23-11-2017, 11:23 PM   #397
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Today’s efforts frustrated in the morning by UPS (see Pet Hates posting). This afternoon taking on board Utopia’s comments I redesigned the brake hanger hub and started to cut metal taking the 82.5mm bar down to 75mm for 26mm then started on the reduction to 50mm for the 15mm closest to the chuck. School run duties necessitated a halt to proceedings. Tomorrow I will finish the 50mm section, use my largest morse taper drill (15/16”) to bore a hole about 30mm deep into the bar and hopefully face the end furthest from the chuck with very light cuts as it will not be supported by the centre. I have ordered some new boring tool bits which are promised for delivery tomorrow and if they do arrive I will take the 15/16” hole out to 37mm. I do not have an internal micrometer,(though I have a bid on one on eBay) so this will be a slow process taking a cut and measuring with a Vernier caliper. Again, the cuts will have to be small to prevent too much load being put on the chuck jaws. I have not done any boring before so this will be rewarding if I get it right and frustrating and time consuming if I get it wrong.
My lubricant feed system worked after a fashion. The petrol tap I thought would be quite progressive in delivery of lubricant to the tool/work piece. In fact turning it on the lubricant flow was nothing , nothing , nothing, too much and far too much. Also the delivery pipe needs a better aiming system. I know I should be using paraffin for aluminium but I keep forgetting to get any so sump drainings will have to suffice for now. Note strides soaked and shoes now fully waterproofed


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Old 29-11-2017, 09:23 AM   #398
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Long day machining my brake hanger hub yesterday. With some new tool bits and boring bars I had to spend quite a bit of time working out the right shims to fit the new tools in the tool post so the cutting height was correct.
Guess what? I buggered it up – obviously with the last cut of the day.
Boring the 37mm hole for the inner bearings I was measuring using vernier calipers and forgot that their measurement of an internal surface has to account for the thickness of the blades, the two outside edges of the blades touch the internal arc and the actual diameter is larger. The hole measured 36.95mm but the 37mm bearing fell in with about 0.05mm slop – too large a gap for bearing fit or even a grub screw. I should have tried the bearing itself to the bore holed rather than relying on the Vernier caliper Another school day!
I have two options here, 1) make another one or 2) sleeve the original with a bronze bush and fit the ball races into the bronze sleeve. There is still enough meat to do this, 6mm either side of the sleeve. I will however have to bore the bronze sleeve so that the wall of the sleeve will only be 1.5mm where the ball race is. If I make the sleeve too tight a fit then I could have trouble pressing it in whilst maintaining the integrity of the ball race location. Also, the outer diameter of the now made hub at 75mm does not allow much meat for the csk 8mm socket screws to bolt to the hanger plate, there is a danger the countersinking will encroach on the outer rim of the hub which will look bloody awful.
Whilst the original work piece is still in the 4 jaw chuck I will finish the existing one to allow the sleeve option. Then I will machine up another one with a larger overall outside diameter to prevent the countersinking encroaching on the outside diameter and hopefully with a bored hole that actually fits the bearings.
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Old 29-11-2017, 09:31 AM   #399
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http://www.arceurotrade.co.uk/Catalo...mm-150mm-516-6
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Old 29-11-2017, 09:34 AM   #400
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Thanks Slob, brilliant - never seen these before or knew they existed even. Already purchased
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Old 29-11-2017, 02:28 PM   #401
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[QUOTE=350TSS;549389]
Guess what? I buggered it up – obviously with the last cut of the day.
Boring the 37mm hole for the inner bearings I was measuring using vernier calipers and forgot that their measurement of an internal surface has to account for the thickness of the blades.
[QUOTE].

Its always the last cut of the day.
Trouble is the winning post comes into sight makes you get complacent, just at the very point when the stakes are at their highest.
Done it myself loads of times.

I don't understand your explanation of how the mis-measurement occurred though.
Vernier calipers should be able to measure bores directly with no need to take anything into account.
However, this method of measuring a bore is intrinsically inaccurate, as it requires an extreme level of technique/feel to avoid getting an undersize reading.
This is made worse (near impossible) when the workpiece is still in the chuck.
The problem arises because the caliper blades essentially form (and measure between) two parallel lines which are difficult to align with the bore at its widest point.
The internal gauges which Slob referred to measure between two points, not two parallel lines, so the technique required is much easier to master.
Me, I use a pair of old-fashioned friction type, internal calipers, which also measure between two points .. but they too require a certain level of technique.
..... as will your new gauges for that matter, but nowhere near so much as with the vernier calipers.

I'm assuming that you will be after a slight interference fit for the bearing and will then sweat it in by heating the housing and pressing the bearing in place.
Therefore you would not be able to use the bearing as a gauge anyway.
The std method of measuring bores in a machine shop is to use "go" and "no go" plug gauges.
I suggest that you make yourself such a gauge out of a piece of scrap before machining the new piece.
I would select my desired interference on the 37mm bore (maybe something like 36.9 or 36.95mm) and make one gauge that size and another a few thou (in old money) smaller than that (maybe 36.8/36.85mm).
Then machine 'til the smaller plug goes in and, holding your breath, take a further light skim from there (or not, if the small plug goes in freely).
You can still use the material that you make the gauge from to make something else later.

This is the kind of rigmarole which makes machining one-off parts significantly more expensive than people realise ... and is why I am sometimes reluctant to take on such work.

ps. if you still don't have any paraffin to use as a cutting fluid, try WD40.
The problem with machining ally (without cutting fluid) is that the swarf easily gets friction-welded to the tool, making it cut both oversize and raggedly.
If it happens, I use a stanley blade to (carefully) scrape it off.

Here endeth the lesson.
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Old 29-11-2017, 05:29 PM   #402
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Quote:
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I would select my desired interference on the 37mm bore (maybe something like 36.9 or 36.95mm)
0.1mm is 4 thou - that is a massive interference!
..... "You cannot be serious"
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Old 29-11-2017, 08:24 PM   #403
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Old 30-11-2017, 01:17 AM   #404
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Quote:
Originally Posted by BLUNT View Post
0.1mm is 4 thou - that is a massive interference!
..... "You cannot be serious"
No, not exactly (John ?) .. the figures were only there to illustrate the method really and I plumped for the simplest ballpark ones that came to mind.
But yes, "maybe, something like" 4 thou probably is a bit toppy.
In old money, off the top of my head, without spending hours deciphering the tables, I probably would have recommended "a thou or two" .. but in metric that goes to three decimal places, which seemed excessive in the context.
I may also have allowed a thou or two to cover an inexperienced machinist (pardon) and some measuring error (which would likely be undersize).
And its funny how a bore in ally can grow a few tenths once you knock the crests off the machining marks, so maybe I erred on the side of caution.
Whatever the tables (eventually) say (in tenths of thous .. beyond the accuracy levels of most turners for a one-off part), I would aim for the top (ie tight) limit of that as a minimum machining tolerance, and err tighter if anything.
It may be sacrilege to say so but you can always lick a few tenths out with emery if its a bit tight (even if it's been previously removed from the chuck) .. but you can't stick any back.
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Old 30-11-2017, 05:06 AM   #405
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Thanks guys for the advice.
No more machining until the telescopic gauges arrive. I will a0 get some paraffin as the bore I machined was a bit corrugated and the swarf was not coming off in those satisfying thin spirals b) as Utopia suggests make up some go/no go stubs, these I can measure confidently with an external micrometer (and on external surfaces with a vernier caliper).
I spent yesterday pondering the packaging of the electrics. Some new coils arrived from Exactfit – the ones recommended by the Fastbikegear people were working out at c 130 euros apiece + customs etc. etc (but they were satisfyingly small). The Exactfit ones were c£140 the pair but whilst they fit the original M900 mountings the design of the attachment of the ignition lead means that in reality they will require more physical space to accommodate them. In consequence they will not mount vertically in the CF box I am making to fit behind and below the headstock. They will not fit either laid flat end to end or even overlapping, but I am confident they will fit angled at 45 degrees to the centerline of the bike and 60 degree to the vertical with the spark plug leads projecting rearwards. Getting the bracketry to work for this is going to be a nightmare particularly as I will have to make some sort of ventilated metal box to provide a faraday cage to protect the MUV2 control unit and to allow the heat generated by the coils to dissipate. I thought about molding some foam to fit inside the box and contain the coils but this will I think be a good way to shorten the life of the coils through over-heating.
There are two, possibly three other bits of kit to find space for, 1 the ignitech ignition module, about the size of a Swan vesta matchbox and the starter solenoid (with possibly an associated relay). I am confident all these and associated wiring will fit nicely in the tray I have moulded into the rear of the battery tray. The only issue is that this tray is located very close to the underside of the carburetor float bowls which is not clever at all. I do not have any other available space so I think I will have to make a cover for this tray keep the volatile liquids away from the sparky bits.
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