Member postings for Ian Newman 1

Hi,

It is interesting to read the views of people who find rate of removal of material an important issue (or at least a consideration).

As I stated in my earlier post, I do not consider a slow rate of material removal to be significant - I am not in the business of making large production runs, I make models as a hobby, as relaxation and entertainment. Consequentially, almost everything I do is a "one off" and so I find I spend a relatively small percentage of my time actually machining.

When considering milling jobs, I would estimate I only spend about 10% of my time actually cutting material. The other 90% is spent on the following tasks (in decreasing order of percentage time consumed):

1) Making/reading drawings and thinking about how I'm going to do the job

2) Setting up the job on the machine

3) Marking out

4) Digging out the required material and tooling

5) Cleaning up and putting stuff away

A further issue for me is that I frequently find I need to make some sort of custom jigs/fixture to hold the part I actually want to work on. Designing and making such items can often take longer than making the part I actually want....

Given all of the above, being able to remove metal at twice my normal rate would have minimal impact on my overall 'production rate'

All the best,

Ian

Hi Colin,

Do not worry about "top speed" requirements - all cutting speeds are simply based on the "most economical speed" in commercial applications, trading off tool wear against rate of material removal. For hobby use (where you do not pay for time, but pay to replace cutters) it is normat to work at slower than textbook surface speeds, depth of cut and feed rates in order to increase tool life.

My mill is fifty years old and has three speeds (I do not know the RPM, I just call them Fast, Medium and Slow) so speed options are limited....

If you have a "slow" top speed it just me and the job might take a bit longer - looking on the positive side, this means you will have more time for that cup of tea!

All the best,

Ian

Hi Robin,

Three observations:

As JasonB has said, plenty of cutting fluid should be used - although it is a forming process, knurling produces small swarf fragments that will be pressed in to the pattern unless washed away. (I use flood coolant at work, but as I do not have this facility in my home workshop I dribble a constant trickle of cutting fluid from a washing-up liquid bottle)

Feed rate - I feed at a "comfortable threading rate" (about 1mm per rev.)

I differ from JasonB regarding matching diameter/circumfrence to the knurl pitch - this is unnecessary, in over 50 years of using lathes (including a series of systematic trials and experiments) I have never found the need to adjust a diameter to match a knurl pitch. If unconvinced on this point, consider the case of the "rope knurl", an example is shown in the link below:

Illustration of rope knurl tool and pattern

The form tool has a larger diameter at its edges than in its middle (so the pattern must have a smaller pitch in the middle compared to the edges), the finished knurl pattern has a smaller diameter at the edges than in the middle (so the pattern must have a larger pitch in the middle compared to the edges). Despite this paradox, the tool works....

All the best,

Ian

Hi JR,

Have you looked at the Stuart Turner website? (Technically now known as Stuart Models):

**LINK**

They supply all levels from individual castings, casting sets, full material sets (castings plus bar stock, fixings, graphite thread, gasket material, etc), machined kits, through to "ready to run" completed models.

Best bit is they sell all their castings as individual items so you can buy random sized flywheels for your latest freelance design, or replacements for that vital casting you just cocked up when you weren't paying attention on your mill/lathe...

Just a recommendation from a satisfied customer who has bought lots of stuff from them over the years. (My seven year old grandson is currently building a Stuart S50 with Grandad's help, in Grandad's workshop, with Grandad standing very closely and nervously behind while Grandson uses the lathe...)

All the best,

Ian

Hi Michael,

Some lovely illustrations in your thread! Thanks for pointing it out to me.

All the best,

Ian

Hi Andrew,

Simple answer, it doesn't work. Check the recommendations of bolt manufacturers, international and national standards, etc.

The idea of putting the thin nut on top is not supported by the arithmetic when you actually analyse what happens in a bolted joint with a double nut.

It is like the idea that you can increase the strength of a bolted joint by increasing the threaded thickness of a nut: A bolt always fails in tension before the threads fail in shear (i.e. the bolt snaps before the thread strips - unless the thread is damaged, in which case all bets are off....). Therefore increasing the threaded depth has no effect on the failure point.

Do the sums - the numbers don't lie

All the best,

Ian

Hi Bob,

The disassembly is the reverse of assembly: The top nut is undone and half the maximum tensile force is taken through the half nut.

No problem.

All the best,

Ian

Hi,

I'm sure I will not be the first to point this out, and I have probably posted this in the wrong place, but....

In MEW issue 311 (Jan 2022) there is a reprint of the notes by Geometer describing methods of locking nuts on studs (p22). The reprint comes with a header giving the caveat that some information in the reprint may be obsolete or incorrect in the light of "modern" methods and techniques, but there is one error that I believe should be corrected.

The illustration "C" shows the use of a "jam nut" placed on top of a full nut, which is generally considered incorrect usage.

There are any number of textbook and internet site references that explain the locking mechanism and hence the correct location of the half depth jam nut, which should be under the full nut. A brief intuitive description is given below, in the description, assume the stud is pointing "upwards" and the nut is being tightened "downwards":

When a bolted joint is critically specified, the required clamping force in the joint is defined. This force requires a certain tensile force in the bolt (or stud). This tensile force is difficult to measure in a bolt so an approximation is used by measuring the torque applied to the bolt or nut when tightening.

In using a jam nut, the half nut is fitted first and tightened until half the desired tensile force is applied through the stud. In this state, the "lower" stud thread flanks are pressed firmly against the "upper" flanks of the nut thread.

Now the full nut is tightened down on top of the half nut. As it is tightened the tension in the stud projecting from the top of the lower half nut increases until it is equal to the tension due to the half nut. At this point the load is taken off the lower half nut and the full tensile load in the stud is carried by the full nut. In this condition, the flanks of the stud thread are lifted off of the flanks of the lower nut thread and the half nut threads are no longer in contact with the stud threads.

Tightening the top, full, nut past this point increases the tension in the stud, but also pull the stud up through the lower half nut so the "upper" stud tread flanks make contact with the lower flanks of the lower half nut.

The top full nut is now tightened to give the design tensile force in the stud. When this is achieved, the stud is stressed to deliver the specified clamping force, the top nut experiences the full downward force due to the tension in the stud, and the lower half nut experiences an upward force (equal to half the tensile force in the stud) pulling it in to contact with the upper nut.

In reality, as these tensile forces cannot be measured and are only estimated through torque measurements, this is a very hit and miss method and should be avoided in any truly critical situation.

All the best,

Ian

P.S. some sample sites supporting the above explanation are referenced below:

**LINK**

**LINK**

**LINK**

**LINK**

**LINK**

**LINK**

I did a quick search and I don’t Think this has been posted anywhere else on the forum:

The centre aisle in Lidl currently has magnetic welding clamps, both fixed angle and variable ones, £4.99

Ian

Hi Ifoggy,

<SNIP>

Most of the small holes I need to drill seem to be in workpieces that can't be rotated

</SNIP>

Ah yes, the difference between the beautiful ideal of the perfect world, and the brutal reality of the real world

All the best,

Ian

Hi,

For small (model sizes) springs, the "standard" formulae do not work as they tend to be based on simple torsion rather than a helix

"The Model Engineer's Handbook" by Cain, or "Spring Design And Manufacture" (same author) are your friends in this task

All the best,

Ian

Hi,

The method of making very small hole by hand holding the drill bit is a "standard" trick. I use a graver to catch the hole/rotation centre rather than a centre drill (which is generally too large for the job). See the videos below for my take on it:

Gravers:

https://m.youtube.com/watch?v=lZ7PP4KgzmU

Catching a centre:

https://m.youtube.com/watch?v=f8IDhos0Qtw

Drilling:

https://m.youtube.com/watch?v=maUtJ2UBuMs

The finished hole:

https://m.youtube.com/watch?v=hiXwU0qn9s0

(The last video includes the workshop cat and the little kid from next door who always came round when he heard the "Grumpy Old Man" doing stuff in the workshop)

The reason the method works is simple physics:

If you have a rotating drill and a fixed work piece, the drill has an axis of rotation and there are cutting forces on both lips of the drill bit - the forces are not equal (the drill bit will not be perfectly symmetrical) and so as the force on one side of the drill bit is greater than on the other, the drill bit gets pushed off axis and the hole "drifts"

If the work rotates, the same physics applies and the drill bit will move until the forces on each side of the drill are equal - this happens no matter how deep the hole is, the drill bit is always forced towards the axis of rotation of the work piece

Holding the drill in a fixed (i.e. tailstock) chuck results in a conflict between the path the drill bit wants to follow and the path being forced on it by the chuck - this can result in a small drill bit snapping. With very small diameter bits, it is best to hold the bit by hand to allow it freedom to "float" - it also allows you to let the drill "slip" in your fingers if/when the drill grabs, or something else goes wrong

I've been using lathes for 50 years and have broken loads of things in that time, but I've never snapped a small drill using the above technique

All the best,

Ian

Love it!

The material is not CI but BDMS - I know I should have used the right material but .... (can't think of an excuse)

As the bed is machined from a block a lot of the detail will be fabricated. Not sure how some of this will be done yet. To mix up a couple of proverbs: It's a case of "burn that while we cross it"

All the best,

Ian

Hi,

The adaption is discussed over several articles in ME magazine - I don't know if these contain any more info.

Vol 143, issue 3557, date 18/3/77 p334 on

Vol 144, issue 3596, date 3/11/78 p1275 on

Vol 143, issue 3598, date 1/12/78 p1405 on

All the best,

Ian

OK - boring things like earning a living got in the way of the model making for a while, but I've done some more on the bed

The outline has been roughed out now and the dovetails machined:

The base/foot of the bed will be fabricated.

Ian

A bit more progress:

The feedscrew for the cross slide machined out:

I also cut out the cross slide front plate. After threading the feedscrew, the cross slide and saddle could be fully fitted with the front plate and feedscrew. A small handle was quickly filed up to allow the operation to be tested:

View underneath:

I also roughed out the headstock - milled/hacksawed from a block:

Hi,

Today's progress - a bit of machining and drill/tapping to make the cross slide fit the saddle, and a little work with a needle file to shape the gib strip.

The parts (only one of the locating dimples has been drilled on the gib strip so far):

The cross slide fitted to the saddle:

Viewed from underneath:

The next challenge is to make a small Tee-slot cutter to produce the cross-slide Tee slots.

Ian

Phil,

As you (and Ian) have noticed, the intention is to make a working machine. I started on the assumption that it would be a nice, simple, straightforward project - it is a simple lathe with a total of about 12 moving parts, it must be a 'piece of cake' compared to a Gresley A4.

But when you start looking at the detail of the task it sort of grows

All the best,

Ian

Having frightened myself with the thought of trying to machine the bed, I decided to start with something a little easier.

I spent yesterday evening flycutting some small slabs of stock to the desired thickness and then cut the 'blanks' that will become the compound slide, the cross slide and the saddle and filing them to shape.

Compound parts:

I machined the dovetails in the saddle, drilled and tapped the gib adjustment holes and filed the saddle to shape:

Hi,

My new project is a 1/4 scale model of my own lathe - a Drummond Pre-B Type made in about 1910.

One of the conical headstock bearings has reached the limit of its adjustment, so I had the headstock dismantled to take dimensions to make a replacement. While the headstock was demounted and in bits I took the opportunity to make fully dimensioned drawings of the parts for future reference - and one thing led to another....

The obvious place to start is the bed. On the original, this is cast and to make a cast. Casting is not a process that I have access to, so I am going to mill/file the part from solid and fabricate some of the minor detail. Progress so far:

As you can see, I've a long way to go with this component...

Ian.