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Member postings for Tim Stevens

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

Thread: Milling Collet Jammed in Taper
05/03/2019 18:08:38

There is a hole right through the spindle and I suggest that it is likely that it is the same diameter from the top of the taper upwards. With any luck it is a larger diameter than the small (upper) end of the taper. So, it should be possible to turn a slug of mild steel to that diameter. If the slug is long enough, it could be used to contact the taper and knock it out. A shorter slug could be drilled and tapped for a push-rod (which could be made from the remains of the draw bar).

Before you do this, make a measured sketch of the drawbar dimensions, so you can make up a new one. I have used a plain mild bar of the thread size (often 8mm) with a sleeve towards the top end, held in place with a couple of steel roll-pins - and a square filed carefully on the extreme end. You can't mill the flats if your mill is out of commission - but perhaps you could use the now-stuck cutter for this job, with no drawbar, and see if that helps to loosen things. Worth a try?

Regards, Tim

Thread: ML7 compound slide setup
02/03/2019 16:59:46

The spanner size you need for this adjustment is 2BA - and perhaps not so easy to find outside the 'empire' we used to have. The BA series is based on metric dimensions, but does not match any of the 'continental' metric series - French, German, ISO, etc. the dimension across the flats is 8.2mm. Spanners do exist - perhaps you might try an on-line auction site?

hope this helps - Tim

Thread: Modern equivellent idea's please
16/02/2019 15:46:57

A further VFD advantage which might be useful, is that some VFD kits come with an RPM gauge. It tells you the frequency of its output (motor rpm, sometimes), and doesn't account for any belt drive etc, but handy none-the-less.


Thread: Submitting Articles to Model Engineers' Workshop
16/02/2019 15:35:30

Yes, Michael, you may be right. My confusion lies in the two checks requiring a 'yes' answer (neat and easily read) followed by one where only a 'no' answer will do. Unless - where you might be right, where the copyright is in regard to the article itself, in which case a note needs to be added to that effect. Or not.

Confused of Mid Wales - Tim

16/02/2019 12:27:35

Neil: Below is the last of the bullet points in your 'Checklist' above. I think you need a 'do not' in the last sentence.

  • Any files to accompany the article that we can put on the website e.g. a spreadsheet. These normally won’t be edited so make sure they are neat, easily read and contain any copyright information.

Cheers, Tim

Thread: Mill tooling runouts
12/02/2019 10:25:08

Gerry - you say: I find the compliance in the right and left direction (X axis) is twice as much as that in the Y axis

I am fairly sure that 'compliance' is not the word you need. A compliant device is one which follows its instruction precisely, so you really mean the opposite, I suggest. Would flexibility be a better word? Or deviation, perhaps? Or even floppiness?

PS my Champion 20V is much the same. One day I will try a couple of steel straps from the top of the column to the wall behind it.

Regards, Tim

Thread: Overload trip
09/02/2019 11:54:41

If you could mount the motor so that it is able to pivot - like the dynamos and alternators on cars - you could use a spring to hold the motor on one side of the slack, with a switch to turn off the input if the motor moved to the stalled side. You would need to adjust the spring tension so that in the stall condition, as the motor tries to haul itself towards the driven side, the stalled movement always operates the switch. Use a switch that turns off and stays off (not a microswitch) to avoid any tendency for the motor and spring to bounce to and fro when stalled.

Not the best explanation I have offered, but I hope you see what I mean.

Regards, Tim

Thread: Tapered gibs on a mini mill (SX2.7)
09/02/2019 11:42:28

A factor you may not have considered is the question: is the column truly perpendicular to the base? if it leans outwards, you will get the effect you describe - machining towards the back of the measured position, if your measurement was done with the head higher up than the machining (as may be likely with a longish finder and a shortish cutter).

And I agree that the gib you have does seem to be thinner than it should be. If the mill is fairly new (as it appears to be, you could try asking the supplier for help. Goods are supposed to be fit for purpose during use, not just when brand new, and faults like this are not obvious until everything - including the machined surfaces of gib and ways - has settled.

A strip of shim which overlaps the gib at both ends, with the ends bent back to locate it, would be worth a try.

Cheers, Tim

Edited By Tim Stevens on 09/02/2019 11:43:29

Thread: Pitched aluminium rings. Any ideas how to machine them?
05/02/2019 11:05:57

Jason - if your three pictures above were done with the same settings, they are a very good example of the colour bias created by cameras which try to achieve an overall 'standard' colour balance. The same effect causes tools which are just less than new to look really rusty, unless there is plenty of red in the background.

Perhaps this effect has caused others problems, so I hope this helps someone.

cheers, Tim

Thread: A gas engine question
04/02/2019 18:29:57

Another factor for a slow tickover is the valve timing. Modern engines all have 'valve overlap' - the inlet opens before tdc and the exhaust closes after. This promotes good scavenge and better breathing at high speed. But you need no overlap for a slow engine (as used in ordinary (non-racing) cars up to around 1930). Given this factor and a heavy flywheel (heavy in the rim, of course) then the CR does not need to be really low, especially if your carb (inlet tract) is small*. And if it is too low your generator will need to be really feeble, or it won't drive it. Although, of course, what you put into a generator is closely related to what you get out. Have it driving a couple of LED bulbs and you get impressive light for very little power.

* if the gas can't get in, you can't compress it so much. You can always lower your CR with a thicker gasket - as long at the rest of the geometry allows the head to move away.

Cheers, Tim

04/02/2019 16:31:25

The Compression Ratio is volume of max space: volume of Min space - I make it 8.22:1.

And the claims for engines at whizzy ratios are all aluminium engines. I bet your model is cast iron - which does make a big difference. And my view is that 8.22 to 1 is pushing your luck if I am right about this.

Regards, Tim

Thread: Mystery optical device
03/02/2019 17:41:33

No, sorry, its actually intended for parties. You produce it and say 'What is this for?' and while everyone is arguing you get a clear run at the punch bowl ...


Thread: A gas engine question
03/02/2019 17:32:53

Pump petrol will only stand a max of about 9:1 in full size engines, and then only if the design is good, ignition timing and fuel mixture bang on. With gas it depends more on what gas, exactly. Town gas is very rare in the UK - it was made from coal, and we don't do coal any more.

Hope this helps (but I bet it doesn't)


Thread: Old screwdrivers - any use as a materials source?
03/02/2019 16:39:01

They make very good tent pegs


Thread: Questions: Myford ML 10
31/01/2019 14:51:40

A dog clutch as shown above would have an added advantage. It would be very easy to add an adjustable rod, running leftwards from the saddle, which would disconnect the clutch at a set position. This would enable you to cut threads without the worry of overshooting. So, I'm going to have a good look at my ML7 to see if I could make something up.

Regards, Tim

Thread: Holding sheet metal on milling table
28/01/2019 18:03:18

Can I suggest that a thin sheet of brass is very likely to flex - possibly becoming tight in the centre or vice versa - unless it is firmly attached all over to a thicker sheet. To do this you need to sandwich the pair under pressure between two flat surfaces, while the adhesive sets. As for the glue itself, tradition would say shellac, such as knotting, applied evenly to the thicker element, allowed to dry horizontally, add the thin brass, and warm carefully and evenly with eg a hair dryer, and put under pressure (four volumes of an encyclopedia, perhaps) while it cools. Leave one edge of the thin sheet overlapping slightly (2mm) so you can hold it when warming the pair again to separate. Then remove traces of shellac with alcohol (meths, burning alcohol).

Or do the same sort of things with Loctite or a similar product - but you need a fancy solvent to get traces off afterwards.

Hope this helps - Tim

Thread: Round indexable tips.
27/01/2019 17:40:57

I have little experience with these round 'inserts' so far, but I have had good finish up to now. I wonder if that could be because the round insets are very finely finished - I would say ground on the OD, perhaps. The actual finish of the triangular (etc) versions seems to be straight from the sintering press. Any thoughts?

And they do seem to be popular with wood turners.

Regards - Tim

Thread: Precision Level or Precision Frame Level
22/01/2019 17:58:41

That would be for setting up a vertical mill, then, would it?


Thread: Is it just me?
22/01/2019 17:52:40

I think that sometimes the firms do this so that you have no record of sending your message. I suggest that it is always better to send an e-mail in the ordinary way - you have a record for following up, and they don't get quite so many of your personal details.

PS thank goodness these Contact us pages are not (yet) infected with compulsory damn-fool smilies, like some others are.

Cheers, Tim

Thread: The Diamond Tool Holder
22/01/2019 17:47:52

I wonder - we have here a tool which is held in another tool and clamped to a third. Would it make sense to combine the first two - The square-bit holder and the cutter holder? A slab of steel with the angled clamp-slot at one end and a dovetail slot in the middle to match your QC? And if you did that, what is to stop you making it double ended? In this case the two ends would have to be opposite hands - one downwards and the other upwards - to avoid the second end from fouling the top slide as you change its position.

There would be one clear advantage for some of us - once set up, it would avoid that awkward delay when we needed to change tools but couldn't remember where we had put the next one.

If I have a go at making one of these, would EN1A be OK or should I go for something a bit up-market, and if so what?

Regards, Tim

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