Member postings for DC31k

That works in bearings with a parallel inner bore. It would struggle greatly in the outer cup of a taper roller bearing as there is virtually nothing for it to expand against.

It would be similar to closing a 5C collet with nothing inside it - likely to damage the tool.

Thankyou fo rthe heads up.

It might be some trick of the photography but the inch markings look too close together.

Very good and very good. But please do not start a thread complaining when someone wins with a boiler suit.

I think you also need to re-assess (in the sense of narrowing the scope of) the 3D printing part of your exclusion clause.

Entering a 3D printed item is probably not within the spirit of the competition, but using a 3D printed something to assist in the item's creation is no different to drawing it in CAD.

In a model engineering context, would you disallow a 3D printed pattern used for a casting because you want the person to whittle it out of a dead tree?

In a woodworking context, there are numerous 3DP add-ons and gadgets that extend and enhance the capabilities of a 1/4" trim router.

For a sculptural item, there might be good reasons to 3DP some level of prototype, gauge proportions and modify as necessary before proceeding to make the real thing in an expensive material.

You are the only person in this thread thus far to write ISO40. I think you are mistaken in that statement.

There are 40 taper specifications that are designed for use in an automatic tool changer, but the top of the tool is in every case threaded because the pull stud that one machine manufacturer uses is not the same as the pull stud that another manufacturer uses. Hence, for home workshop use, almost every type of 40 taper tooling can be used with a drawbar.

Sometimes if the tooling does not have the parallel shank at the top of it, a longer drawbar would be needed. Sometimes the tooling does not have the cut out for the drive dogs at the bottom of it, but it can be adapted.

I would question the assertion that the 3/8" drawbar would be marginal in strength. To give it some teeth, it would be necessary to calculate the tension that, let us say, a piece of M10 or 3/8" grade 4.8 studding will withstand and then come up with a plausible machining situation where that number might be approached closer than 50%.

Are there any solutions within the means of a home workshop to prevent this happening?

Would wrapping in stainless steel foil and including a bit of paper that would burn off the oxygen work?

For small stuff, could you coat in borax paste as if you were silver soldering and then dissolve off once cooled?

Would something as simple as surrounding the bar you want with another bar on each side of it tightly wrapped with wire be good enough to stop the bit in the middle being oxidised?

Maybe I was reading his stated "my first ever machine/mill" too literally. I wonder, if he has a lathe, why he would be asking for someone else to make the item pictured?

It is an interesting exercise to list the minimum amount of stuff needed to bootstrap him out of this hole.

My B&Q starter for ten: M16 threaded something, hacksaw, vice, cordless drill, 5mm drill bit, M6 tap, M6 threaded rod, M6 penny washer, M6 nut, 10mm spanner. Make the first one with an M6 female thread, the small diameter giving lots of wiggle room in the end of the M16 rod. Even if drilled not in the centre and not completely square it will still work. Use the first one to hold the ER chuck in the mill to make a second, much better one.

Who is next for machining 'name that tune'?

At this point in the drama, his Uncle Murphy steps forward to inform us that the only drill chuck he owns is on a 40 taper with M16 drawbar thread...

If you use what you have drawn to solve the problem, be very, very sure that the 3/8" drawbar will unscrew before the M16 thread.

If you are not very, very sure, put a double locking nut at the top of the 3/8" drawbar so you can drop everything out of the bottom of the spindle if necessary.

Have you checked there is enough headroom up inside the spindle taper to accommodate the 15mm height of 25mm diameter above the end of the 40 taper tool?

The M16 to M12 or M10 version of this might be a better solution:

https://www.ebay.co.uk/itm/325124381095

Loctite it into each tool and the drawbar will always come out as it should.

Given that a partial profile insert has a tip radius to suit the finest thread in its range, the infeed for that fine pitch should be the same as for a full profile insert.

There is a mathematical relationship between pitch and tip radius.

So for any other pitch within the insert's range, it should be possible to derive a correction factor (a number greater than 1.0) by which the full form infeed should be multiplied to obtain the partial profile infeed.

Every manufacturer's tables that I have seen are based on full form inserts so it would be a useful exercise to derive (and possibly publish) these correction factors.

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Now to flies in the ointment...

There is a slight complication when it comes to 60 degree partial pitch inserts - what tip radius do they actually have - the minimum tpi stated for the insert or the minimum metric pitch stated for the insert? The two numbers will vary slightly, but maybe not enough to be significant.

Partial profile inserts generally come as Axx, AGxx and Gxx (and Nxx and Qxx for really coarse stuff). The minimum pitch of A and AG is the same, but G starts at a coarser pitch, so there would need to be two sets of factors for each vee angle (correction factor for G60 on 1,75mm pitch would be 1.0) .

His previous question on the same subject was on 25/07/23 (https://www.model-engineer.co.uk/forums/postings.asp?th=187461). The details you ask for are in that thread, posted 26/07/23.

That kind of begs the question of why the boiler supplier is quoting a superceded standard on their website.

Is is easy to find out the last date BS2790 was valid?

If you are thinking buying in quantity of more than one, it might help to find a definitive copy of the Standard that applies in Australia and send it to Steam Traction World for comment.

They would be well placed to say if their boilers comply. They could also identify any place they do not comply and suggest options for resolving the difficulty. They would be more likely to help on a multi-item order than a one-off.

The other option is to obtain a copy of BS2790 and send it to the relevant authority in Australia so that they might comment on if it is an acceptable alternative to the local standard or again identify specific items that need further attention.

If I put BS2790 into Google, the second link I see is a pdf copy of the standard, so you could do a 'compare and contrast' yourself in advance of any further action (i.e. the lawyer version where you do not ask any question to which you do not already know the answer).

The 'M' in the above is the ISO code for the length.

https://www.cutwel.co.uk/blog/learn-the-boring-bar-iso-code-system

If you search for shorter lengths (S12 H, J, K), there are few options, hence cutting it down would seem to be a reasonable way forward.

CTC Tools in Hong Kong have 12mm (metric) alternatives to the 1/2" (imperial) Glanze ones linked to above.

For initial balancing, you could spend £3.56 on one of these:

https://www.ebay.co.uk/itm/275570011508

They do, but the worm ratio and the number of holes in any particular circle are not independent.

The (useful) number of holes depends on what prime numbers are contained within the worm ratio. Consider a 40:1 ratio and a 90:1 (or 60:1). There is a factor of 3 in these latter two ratios which is not in the former ratio, so plates supplied with the former have to provide the missing 3.

Would it be true to say that the rotary table has 360 degree graduations around its perimeter?

Would it also be true to say that there is a fiducial indicator somewhere on the body of the table that registers the passing of these graduations as the table is rotated?

If so, align two of the slots parallel to the X-axis and remove and refix the fiducial indicator such that it reads zero in this position.

As below your original but above this post, I was under the impression that R8, being invented by Bridgeport was univerally 7/16" - 20 UNF.

I have seen it reported that it is often the fit between the key in the spindle and the keyway in the tool that causes issues. Less than perfect quality tools/collets can have undersize keyways.

As it is a 48t gear, that implies that you have a metric (Continental) Chipmaster.

The Continental is less often seen than the imperial version so that might make finding a replacement difficult. The other issue is that with 48t, it would come from a set of gears 'by fours'.

Other lathes that use the same 14DP 14.5 degree PA gears are Harrison L5 and 140, Drummond and some early larger Colchesters. Someone might know if 48t was part of the Drummond or Harrison set.

The gear is quite important for most metric threads. It is used as either 28/48 or 56/48, which reduce to 7/12 or 7/6.

You would have to check if the gears would fit the space available, but it is possible to reproduce those two ratios with 35/60 and 35/30. Coming from a gear set 'by fives', they might be easier to find.

The other difficulty is the six-spline centre detail of the gear (it is the same as Boxford X10 models) - you could re-use the broken gear if you find a single 48t replacement, but if solving the problem involves more than one gear, how do you make more than one new centre?

This page lists a whole range of machine tapers and is well worth bookmarking:

https://www.tools-n-gizmos.com/specs/Tapers.html

A 30 taper is 1.25 inches major dia.; a 40 taper is 1.75 inches.

Standard drawbar size for 30 taper is 1/2" or 12mm; for 40 taper it is 5/8" or 16mm.

Tooling with an imperial drawbar thread can have either BSW or UNC threads; the thread pitch for 1/2" BSW and 1/2" UNC differs.