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Member postings for DC31k

Here is a list of all the postings DC31k has made in our forums. Click on a thread name to jump to the thread.

Thread: What tool to measure small bores?
01/03/2021 08:33:25

The bearings will only come in a limited range of sizes and will be at full- of half millimetre dimensions. Perhaps consider some second-hand go-nogo gauges. Alternatively, some under- and over- gauge pins.

The point is that you do not need measuring capacity spanning the full 4-10mm range with a resolution of 0.02mm. You only need a very, very limited subset of this range.

With such small bearings, Loctite is your friend.

Thread: Avoiding marking / scoring while using fixed steady.
01/03/2021 07:40:19

Soft fingers, ball bearing fingers, a close fitting ring on the stock have been mentioned.

You could also try an old-style cathead and run the steady on that.

Possibly, a wrap of self-adhesive aluminium foil tape with diagonal butt joint might work.

Thread: Where to find a *good* optically flat mirror?
23/02/2021 20:10:26

There is a US site, where they have an online calculator. I do not know if their products are suitable for your application so apologies in advance if this is misdirection.

Thread: boring bar
23/02/2021 19:06:36
Posted by Robert Butler on 23/02/2021 18:46:47:

Ring Jenny J B Cutting Tools she will probably know exactly what you want, a very helpful lady.

And he could be helpful to her if he does what Mr ega suggests and finds information on the bar.

A Google search for 'BBPW-508R' produces a myriad of useful results including insert codes.


Thread: Help identifying a milling machine
16/02/2021 08:03:15

I think the Abene references are a little misleading. It has only superficial similarity to those - the head on the (opposite) side instead of the front. And that head is on a sliding ram with an additional Y-axis on the knee.

The photos taken from the right hand side of the machine look as if there is an additional vertical sliding surface, perpendicular to the knee ways and perpendicular to the ram ways so the whole head and ram can possibly be raised and lowered. It almost has two Z-axes and two Y-axes.

Google images will be your friend here.You have to try various combinations of 'Swiss milling machine', 'German milling machine', 'European milling machine'. These may give you some manufacturer names for further searches.

From the square shape and design of it (round, plasticated handwheels), to me it suggests late 1970's, early 1980's (compare and contrast the newer Abene models, Schaublin 22, later Deckels). The lathes site is better on the early machines than the later ones.

Another place to ask is anglo-swiss tools and the oldswissmachines io group.

If you remove a few covers, you might find date codes on some of the motors/electrics. That can narrow things down a bit.

Thread: Belt tension
15/02/2021 15:38:12
Posted by Clive Foster on 15/02/2021 14:50:38:

As Dave says the tension on toothed (timing) belts isn't great. Maybe a pound or two force to deflect its sideways at the mid point between pulleys. 5mm - 3/8 is small so tension at the low end methinks.

A good reference is here:

Inter alia, it shows three common belts at 5mm pitch and one at 0.200". Belt and pulley profile must match.

Section 10 of the document discusses the correct tension and it should be noted that for a positioning application (perhaps where a stepper motor is used), the tension is greater than just a drive application.

Thread: Pipe bending
14/02/2021 08:02:24

Could I offer this method as an alternative?

Very simple. Just need a vice, torch, long lever, wire template...

...and 25 years of practise

Thread: Vfd advice please
14/02/2021 07:52:20

Lots of replies answering his question, but could I break the trend and suggest that you may face challenges if you use a 3/4hp motor for a 3" wide sanding belt?

Further, sanding and linishing (an abrasive machining process) generally requires a high surface speed to be effective. Thus, speed control downwards from a motor's synchronous speed, even if a two pole motor is used, may not be necessary.

Simply put, you want the belt to whizz along powerfully, not crawl along, slowing down as soon as you try to sharpen a pencil on it.

So you need to start with the surface speed you need, see what diameter drive pulley you will use and select a motor rpm to give that surface speed. Then look at what motor is required to produce the necessary torque at that rpm.

To me, the 3/4hp seems way underpowered.

Thread: Indexable Lathe Cutters advice.
11/02/2021 07:30:35
Posted by JasonB on 11/02/2021 06:59:57:

You don't have any boring tools in that set.

Look at the side of the holders, you can just see the numbers on the top one in the photo the "08" indicates that the shank is 8mm x 8mm

He said it is a nine piece set. The photo only shows 8 tools, so it would be correct to say there are no boring tools in that photo.

We need a photo of the missing tool to make a definitive statement about the properties of the set.

At a pinch, the bottom one, the internal screwcutting tool could be used for boring, but it would be horrible.

The code on the toolholder is SSSCR0810H09. That means that ONE dimension of the holder is 8mm and the other is 10mm. Compare and contrast the very common SCLCRxxyy tools, where x and y are generally equal.

Thread: Picking up the thread.
10/02/2021 19:02:45
Posted by Tony Pratt 1 on 10/02/2021 17:56:22:

Yes, set the cross parallel to the lathe travel & reset the job as before. Start the screw cutting procedure with the tool not cutting metal, stop the lathe once you are in the bore...

Leave the tool slightly slack in the holder and slide it forwards and backwards feathering the cross-slide until it drops into the groove of the existing thread. Tighten tool in holder.

Thread: Engineering / Modelling Books for Winter Evenings?
10/02/2021 07:26:15

Neville Shute's autobiography.

Truth, lies and O rings (Space Shuttle)


Richard Feynman's writings on the Shuttle incident.

Thread: leadscrew pitch
09/02/2021 19:21:44

We have had long and interminable discussion in another thread about various definitions of the inch.

This here thread would seem to provide two more candidates:

the Howard inch, where 1/4 of it is equal to 6.354mm and the Duffer inch where 1/4 of it is 6.28mm.

Thread: Push broaches for square holes
08/02/2021 07:08:19

You are concerned that £100 is an excessive price. Examine carefully the item you would receive for that money and ask yourself if you could make something of equal utility for the same price. DuMont's site in the US is a good place to start to gen up on broach technology.

In addition, it may simplify your work, open up tooling options and ease the path of any tooling you do use if you can critically examine the 'deepish' nature of the holes. Consider what depth the actual square portion needs to be and any part that does not need to be square see if it could perhaps be made circular of a diameter equal to the across-corners measurement of the square.

Thread: 8mm shank parting tool blades, where to buy?
04/02/2021 21:11:33
Posted by Stuart Cox 3 on 04/02/2021 20:21:19:
Thanks, I did take a look at the RDG tools listing before but they don't seem to list one at 8mm.

Sorry, clarity fell away in the search for brevity. I was going off the ArcEuro description that says it is 8.3mm high. There are a lot of 5/16" x 1/16" blades listed, but they might not be tall enough and possibly too thick. The RDG one is the correct 1.5mm width but 10mm high, and could be reduced on its underside by 1.7mm.

04/02/2021 20:10:00

Are we allowed to mention bona fide UK-based eBay sellers here?

RDG Tools list something suitable, as does MaxT Engineering Supplies.

The item numbers, if they survive the censor, are 351498912133 and 372619224936.

Thread: spindle thread
04/02/2021 17:52:53
Posted by colin hawes on 04/02/2021 16:47:44:

DC31k is correct; the thread will be 1 3/8 x 8

If you have understood my post as saying this, then I am sorry that I did not write more clearly.

A simple OD measurement of the register would give a more reliable indicator of the thread size than an OD measurement over the thread crests. If the register is 1 3/8", then it would be difficult for the thread to be 1 27/64" (27/64" is bigger than 3/8" so the register would not go over the male thread).

If the register is close to 1 27/64", then further investigation is needed, including David's metric possibility. One way may be to do a three wire measurement of the thread. There is a good online calculator somewhere for this, whose address has been posted here before. It will tell you the best size wires, but will also give you the measurement if you input the wires you are using. This means you can use three drill shanks, three drill blanks or three bits of silver steel or whatever you have to hand that is close.

On further reflection, I am wondering how a loose fit of a 1 3/8" (female?) thread leads to the supposition that the mating (male, spindle?) thread is 1 27/64", a bigger size. Surely the only way to get the two threads to mate at all is some gender reversal?

04/02/2021 16:34:30

Surely the chuck does not use the threads alone for location. Does it not have a register inboard of the threads? The register size and fit of the chuck to that register is way more important than loose or tight threads. The threads do not want to be too tight lest they try to influence the register.

Thread: How to align a fixed steady?
04/02/2021 11:16:26
Posted by br on 04/02/2021 10:15:01:

How do you stop the fingers marking the material, just out of interest ?

One option is to use roller fingers. Small bearings can be used for this. Plastic bearings are also available. Wood turners use skateboard or roller blade wheels.

The trouble is that most steadies supplied as standard with a lathe are woefully small. I believe Hemingway offers a large capacity one and John Stevenson showed one made up of laser-cut steel sheets laminated together.

Thread: M2 x 2mm brass grub screws - do they exist?
04/02/2021 08:01:59

Make the balance weight 1mm greater OD (and remove material elsewhere if total mass is important).

Drill through hole in weight 1mm offset so one side has 3mm wall.

Thread: Loctite made in China?
02/02/2021 15:24:54

My starter for 2p. Genuine, grey import.

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