Member postings for DC31k

A couple of observations:

While the advice is not to fill the bore with the shank, maybe sliding contact between the shank and the bore on the opposite side to the keyway would be beneficial as then the component will help support the slotting bar in the same way as a broach bush. This does presume 'on tool' adjustment of cutting depth.

Jason asks how long is the slot. By convention, we make slots the same length as the component they are in, but you could see if this is a necessary feature of your design. If the slot does not need to be full length, remove those parts that do not need to be there by plunging vertically with an endmill.

If you plug the bore (or on a piece of stock where the bore is not already formed), you could drill away a small part of the keyway leaving less for the slotting tool to remove.

Is it worth trying to 'pull broach' rather than 'push broach'?

Change the keyway to the shaft and use a couple of dog point grub screws to form the 'key'.

There are a few posts on this forum concerning the machine. This search term (without the quotes) should find them:

"britan lathe site:www.model-engineer.co.uk"

The other thing to consider is the available variety of holders for the inserts.

The ones branded Glanze (sold via Chronos) are an example: inter alia, they offer one that uses the normally-unused edges of the CCMT insert, so you obtain four edges out of each insert. Unfortunately, that holder seems specific to Glanze and only available as part of a set.

A seconday consideration is what holders are available for boring.

You are right about it being the "other hole" because the one to which you refer is in an-other part altogether.

The oil nipple is in the clutch housing. The grub screw to which the OP refers is in the front spindle bearing cover.

In a later manual (from SER 3311, diagrams CHIP-01-70 and CHIP-02-70) the longer grub screw goes into the headstock casting first. The shorter one on top of it is presumably to act as a lock bolt so the one below does not back out due to vibration.

The front bearing cover in the manual shows no grubscrew, but the item 1146, labelled 'peg' looks too coincidently to be in the same general location as the grubscrew for them not to be related.

In every Chipmaster I have seen, in both locations, the factory paint has been applied over the grubscrews.

I was just to post the same.

Strange as it may seem, 25 x 10 (£20.90) is more than 25% more expensive than 25 x 8 (£14.70).

It is worth looking up some sizes near the one quoted and see which section size is most economic (maybe 20 x 8 [3/4 x 5/16] would do)

It is possible to cut a tapered thread with a taper attachment on a lathe.

It would be possible to set a bar at the back of the lathe at the correct half angle for the taper, disconnect the cross slide and use a strong spring to pull a roller or follower attached to the cross slide against the bar. Put on the cut with the compound slide.

Even better than the spring, mount the tool at the back of the stock and the cutting force will always push the follower into contact with the fixed bar.

Offset the tailstock (perhaps by means of a boring head mounted in the taper and a centre in the place where the boring tool would go) so the face of the cone is parallel to the lathe's travel. You might need ball centres or a bell centre drill at both ends as the taper angle would be relatively big, and you would need a driving arrangement at the chuck end that ensures uniform angular velocity (I think it is called a compensating drive dog). That would give you a very skewed thread, but in this application, it would not matter.

I believe there were some lathes made where the power cross feed could be engaged at the same time as the longitudinal feed.

See:

https://pewetools.de/en/shop/product-category/square-head-screw-m7x1x22-for-system-size-a/

90% of off-the-shelf socket capscrews are straight knurled on the outside of the head for the top 3/4 of its depth. Make the counterbore the same size as the un-knurled portion of the head and press fit together. It would act like a rudimentary splined joint.

Fully in the style of the thread title, can I suggest that a set of blue balls might assist. Scribble marker pen over your ball and then clamp up. Where chafing occurs, that will indicate the line of contact and guide you where attention can best be focussed

Looking at the album, could the pillar/piece of metal on the other side of the clamping screw be too long? If it is over long, and ridgidly connected to the clamping plate, turning the screw will just be trying to bend that plate rather than squeezing the ball. Maybe remove the capscrews holding those parts together, mill a semi-circular or vee groove in both and use a round rod as a pivot.

I am wondering if a thin ring of a good insulating material in direct contact with the copper boiler, with the wooden ring outside that, might help. It might also provide some compressibility to cope with heat expansion.

Maybe glance through the things here:

https://www.vitcas.com/thermal-textiles

This looks similar to Victas' thermal felt

https://www.ebay.co.uk/itm/386102473543

and see if insulation inspiration strikes.

That is the trouble with thought, it can mislead you. Best not to think but to test the indicator with something of a known dimension (thickness) and see how much the indicator moves. For instance, a search could tell you the thickness of every coin that is legal tender in the UK. Passing one of each of those under the indicator would teach you a lot.

Given how badly thought can divert you from truth, 'look', as you have done with the arbor face, is at least an order of magnitude worse. Now you know what each of the little lines on the indicator mean, poke it up inside the spindle, even if it is at an angle, and actually measure if there is any run out in the spindle itself.

You have paid money for the tool. Why 'look' when you can recoup some of that money?

All you can say for sure is that there is run out on the arbor. You have not yet identified or isolated the source of that runout. You will soon become bored, as will your supplier, if you return a few arbors as faulty and then subsequently discover there is an issue with the milling machine spindle.

I think the emotion and value-judgement-laden language may be a little inappropriate (see also 'purist traditional' above).

From a purely technical, engineering standpoint, it just makes sense to dimension in the units in which the items were originally produced.

It might be a good service to then show alternate dimensions in the measurement system in common use today, but then their origin is clear and nothing is hidden.

I do not know how it would work, but for some things (e.g. counterbores, clearance holes), strict adherence to the original when showing metric might make things more difficult to construct. I guess a lot depends on the skill of the person making the drawings in choosing a suitable substitute.

Making drawings in millimetres of parts which have always been imperial rather negates the 'clear and easy to follow' idea.

If by 'every part' you include the fasteners, what will be your metric description of a 2BA x 1/2" long socket capscrew?

Have you tried 'model boiler calculations' in a search engine?

Given its focus, could it be possible that such a question has been asked on this forum in the past?

Please start with these:

https://www.model-engineer.co.uk/forums/postings.asp?th=75370

https://www.model-engineer.co.uk/forums/postings.asp?th=170551

The SFMES link in the above is now incorrect:

https://fmes.org.uk/pressure-vessels-and-testing/

Edit:

https://www.homemodelenginemachinist.com/threads/model-boiler-design-information.8176/

Edited By DC31k on 14/09/2023 13:21:01

Thanks for the tip.

I think what you describe is known as an 'olive' or 'pipe olive' in UK.

I suppose if it were a dire emergency a wedding ring could be used...

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Most of the plastic fittings have poor UV stability. Leaving them exposed to light 365 days a year will shorten their life.

I think this might be the manual for the Clausing version of the round head Triumph:

http://vintagemachinery.org/pubs/detail.aspx?id=3846

For that, and for 4.5tpi, it says (on page 14/15) the 36t gear should be the DRIVER (I think that is what you call the stud gear above) and is used in place of the normal 18t gear. The DRIVEN gear (what you call the screw gear) should remain as 42t.

What tpi did it actually cut with the set up you describe?

Can you get it to cut 9 tpi or 18 tpi successfully? If so, 4.5 tpi will be one or more multiples of two different to those.

Someone will be along soon to advise the exact answer, but with a bit of thinking you might be able to solve the problem yourself.

For imperial threads, the numbered selector changes the tpi and the ABC lever multiplies or divides those tpi by a factor of 2 (if you take B as the starting position).

Since your required 1mm thread is coming out as 2mm, you need to do something to the ABC lever that would increase the tpi of an imperial thread by a factor of 2.

There are only three possible positions for the ABC lever and you have posted what happens in one of those for two cases. Try the other two positions in each case and report your findings. If it does not solve the problem, it is data that will contribute to solving it.

Having a problem that is exactly twice what it should be is easy to solve. Think how lucky you are that the thread did not come out as 1.87mm pitch - that really would require some thinking.

To save wasting metal, tie a marker pen to the toolpost with an elastic band and use that to draw on the stock as it rotates.

Unless I am mistaken, that appears to be for a four-way indexing toolpost. I would be interested to see a patent for the quick change post.

Loose enough to self-align but not so tight as to restrain the leadscrew in any way other than the correct one.

If you do end up removing it, mark which side is currently facing the column and reinstall in the same way.

Forwards/backwards, play will contribute to backlash so in that direction it is undesirable.

Left/right play will have no effect as the Y-axis is constrained by the ways.

Up/down play (float) would be good as it allows for manufacturing tolerances on the relative height of knee ways, saddle ways and screw centreline.