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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: Clamp Sets - Thread Type?
08/11/2021 07:03:55

Invest some of the grandchildren's inheritance into a 1/2" set and then there would be no doubt.

Photograph them, enlarge and draw over the photo on the computer.

The spanner size for the flange nuts used on clamping sets is not always standard: I have M12 with 22mm A/F and M14 with 22mm A/F (which is good as my drawbar is also 22mm A/F and other bolts on the machine are 7/8" A/F, so one spanner fits all).

Thread: VFD size
06/11/2021 12:54:46
Posted by Andrew Johnston on 06/11/2021 12:16:41:

I can't see a problem running a 2-speed motor from a VFD

The challenge using a 2-speed motor with a VFD is that it is not possible to configure the motor to accept 230v three-phase. You can run either speed of a 2-speed motor off a VFD that outputs 415v three-phase with all the precautions you rightfully highlight.

As I understand it, the most common way for a two-speed motor to be configured is 'Dahlander wound'. If you find diagrams of this configuration (e.g. https://www.wikiwand.com/en/Dahlander_pole_changing_motor), you can see how a standard low voltage delta configuration of the windings is not possible. Very briefly, from the above link, in low speed the motor is wired high voltage delta and for high speed, it is wired double-star.

06/11/2021 07:31:39
Posted by colin hamilton on 06/11/2021 05:44:02:

It is tripping on error code 4 which covers a load of sins one of which is over current

Just saying it trips with an overcurrent fault does not tell us much. For the particular setting that is currently programmed into the VFD, 'over current' could be 0.5A.

As Mike says, the maximum current value is normally a user-settable parameter in the VFD. Read the manual or post a link to it and the VFD here and we can advise further. Try to measure the current the motor is actually pulling: separate one of the phase wires from the others and put a cheap current clamp meter on it.

Make sure the ingoing supply to the VFD is adequate - cross-sectional area of wires and length of cable, even more so if you decide to pursue your 'somewhat oversize' route.

Is the output of the VFD wired directly to the motor?

Thread: Metric Screwcutting on Super 7B with 127 Tooth gear
04/11/2021 15:03:01
Posted by John P on 04/11/2021 11:15:20:

Anyway the chart is there for you to use if you wish...

As a general observation (i.e. I have seen it enough now to be bothered to ask the question), why is it that you produce a metric threading chart that includes pitches that are never used and are entirely non-standard (e.g. 2.25mm, 3.75mm, 1.3mm, 1.1mm)? I have seen it with metric thread dial indicator charts as well.

How many imperial threading charts do we see that include 6 1/2 tpi or 15tpi or 9 1/2 tpi?

Thread: IKEA Kitchen Carousel Peg
03/11/2021 07:32:37

Post a fully-dimensioned 2D sketch of it (pencil and paper) and someone will model it for you.

As you say, FreeCAD has a steep learning curve. If it looks like the one above, drawing it from 3D solids that have Boolean operations performed on them might be easier than using sketches.

You could try OpensCAD, but if you want a facsimile of the one above, it might be tricky from a standing start. However, if you can live with a functional replacement, it becomes much easier: its body is a cube. It is then partially cut by a horizontal cylinder. At the base, a cylinder projects, joined to a truncated cone (in OpensCAD a cone is a cylinder), cut through with a cube.

Thread: Where to get small Electrical component?
01/11/2021 15:53:18
Posted by mgnbuk on 01/11/2021 15:35:43:

Iskra

A Google search for "KPB 7301" brings up what appears to be the manufacturer's website...

...where it describes the item as a 'radio interference suppression capacitor'.

I am struggling to see how failure of this part could stop the motor working (unless it is shorted, in which case simple disconnection of it is worth trying).

Thread: Metric Screwcutting on Super 7B with 127 Tooth gear
01/11/2021 07:35:08
Posted by noel shelley on 31/10/2021 23:18:54:

This thread was started 8 years ago and got no real answers ! Like Nigel and Swarf Mostly, I got hold of a 127 change wheel ! Can any body give us instructions as to using it?

You need to be very specific concerning your machine details to receive any meaningful answer.

Particularly, if it is a changewheel-only (non-gearbox) machine, the solution will be different to whether it has a gearbox.

Thread: Choice of collets
30/10/2021 08:19:57

Consider the headroom you have between spindle nose and table. A small Clarkson chuck on whatever taper will have a certain length (height). An ER25 chuck and its nut is likely to have a shorter length, which may prove an advantage. The projection of a given cutter from a Clarkson chuck is fixed. You can, within reasonable limits, vary the projection of the same cutter from an ER chuck (choke it up or hang it out).

Thread: Pratt Burnerd 4 Jaw Chuck
24/10/2021 10:38:23

They are a tight fit in their holes. No other method of retention.

It is prudent to keep pins, jaw screws and slots together so they go back in the same way they came out. If really fussy, mark rotational orientation as it would be possible to reinstall 180 degrees out.

Examine them well and stone off any burrs resulting from the removal process before reassembly.

Beware on reassembly that if the forks are twisted (rotated) it can make operation of the screw very tight.

Reassembly can be made a little easier if the chuck is warm and the pins are cold.

Thread: Collets for Myford tailstock
23/10/2021 10:56:42

Particularly with regard to the Morse taper collets (with limited grip range), have you confirmed the shanks of the taps you want to use fit a standard collet diameter?

The ER collets might work better as they have a range of gripping diameters.

Thread: A workholding question.
22/10/2021 07:52:22

Tin the brass parts and the steel stub with soft solder. Sweat them together. Cut all at once.

Alternatively, superglue instead of solder.

You did not say how (which direction) it moved. Are you cutting to compress the double-sided tape or to expand it? If it moved downwards or sideways, a flat stop in the appropriate direction will prevent this.

To me, the steel stub looks a little on the small side. Something the same diameter as the brass would give more surface area for the glue. Clearly, you will cut into it the first time you use it.

Thread: Trugrip conversion
20/10/2021 17:28:25

The major diameter is 1.238". If you want to verify, buy a 5C collet and measure it.

I am guessing that the thread form is 60 degree included angle.

Most of the major threading insert manufacturers provide tables showing the infeed for a particular pitch and thread form.

Below is one example. Another very good one is the Seco one:

https://www.mitsubishicarbide.com/application/files/5314/7191/5783/tec_threading_depth_external_en-us.pdf

Use the numbers as a guide. The final dimension you require depends a lot on the cutting tool you use - a hand ground HSS one will be different to a multi-pitch insert (A, AG, G, etc.) and will be different to a single (specific) pitch insert.

If you are set on this route, it might be wise to buy your collet set and cut a test piece in the same material as the real version to verify that it fits every collet. If you cut the final version to a set of numbers, what happens after the chuck is assembled and one of the collets does not fit?

Thread: Spacing of buttons for making involute cutters
20/10/2021 09:00:33

Resurrection of a 7-year old thread...

I have just stumbled across the following, which provides a method of calculating button diameter and spacing that I had not seen before (the computing power just was not available to Ivan Law when he wrote his book). The paper itself is only 31 years old.

https://www.geartechnology.com/articles/0990/Approximating_an_Involute_Tooth_Profile/

Direct link to the paper itself:

https://www.geartechnology.com/issues/0990x/bilhardt.pdf

If anyone wants to duplicate his computer program, there is a very elegant solution for fitting a circle to three points here:

https://stackoverflow.com/questions/28910718/give-3-points-and-a-plot-circle

Thread: Hi all, newbie with first lathe, rare one i think.
19/10/2021 14:26:54
Posted by wayne ollerenshaw on 19/10/2021 14:09:40:

I will redo the check again tonight. Will of been me and a newbie to the world of lathes making a mistake like that.

As Herr Michael Gilligan suggests above, a photo of the Gewindesschneide Tabelle will mean you do not need to measure anything - the info. on the plate will tell you. Think of it like the label in your trousers - you do not need a tape measure to size them, you just look inside and see FB.

19/10/2021 12:23:12
Posted by Dave Halford on 19/10/2021 11:26:41:

Which would be quite handy for a metric German naval vessel crew.

Makes you wonder about the story.

Yes. It is interesting to note that the two shown on the German site linked to above are also imperial - they are both gearbox models and the screwcutting charts are shown in the two discussion threads.

In one of the German site discussions, the poster says the bearings were marked GDR, so East German. However, that may have no relevance to dating this one.

Thread: KLG Mystery Object.
18/10/2021 17:47:50
Posted by Ian Johnson 1 on 18/10/2021 17:35:46:

Looks like a bottle opener? One of those freebie corporate giveaways?

You are correct. See near the bottom of this page.

https://aipetcher.wordpress.com/2011/11/02/a-life-in-a-year-2nd-november-motorways-and-minis/

Thread: Ball screws
13/10/2021 17:12:59

If you are converting a machine, then asking about ball screw diameter is rather putting the cart before the horse.

Decide on the machine and make some drawings of the space available for the nut and screw. That will then guide you in the diameter. Ball nuts for a given screw diameter are somewhat bigger in all directions than standard nuts.

Thread: Halogen Oven
12/10/2021 19:51:34

Every one I have fixed has been left hand thread.

Are you absolutely sure it is the element?

Maybe 4 out of 5 that I have fixed, it has been the thermal fuse that has gone.

Check it with a continuity meter and if it is open circuit, temporarily bypass it and see if the element comes on.

Thread: cutting spur gears on a mill
11/10/2021 07:04:01
Posted by Andrew Johnston on 10/10/2021 20:47:33:

If a hob produces a mathematically correct involute curve rather than a series of facets why do some gears need to be shaved after hobbing to improve profile and reduce running noise?

What you are asking is precisely analogous to asking why turned parts need to be ground or lapped after they come off the lathe - the answer being to improve the surface profile.

A great number of the gear finishing tools use the same motion as the gear cutting tools that preceded them, just with a different cutting tool - often an abrasive.

Pete Rimmer's point is very apt. Nobody complains about a lathe producing a helical surface. One can extend his point to the flat surface produced by a shaper or planer - at a microscopic level it is a series of ridges, but the tool/workpiece relative movement is correct.

There is a huge amount of confusion in this place over what constitutes an 'approximate' method. A lot of it is simple misunderstanding of the language used.

A generating process is by definition one in which the movement between cutting tool and workpiece is geometrically (mathematically) correct to produce the shape required. It is a mistake in the use of language to employ 'approximate' to describe a 'generating' action.

Where 'approximate' might gain some foothold is in the _application_ of the method. If you do not let the hob cut 'enough', the sides of the gear teeth will not be well formed (cf roughing cut and finishing cut with a lathe - coarse and fine helix left on the work). The definition of 'enough' is arrived at by the end-use to which the gear is put. Sometimes, even 'forever' is not 'enough' and that is when you have to send the gear to another machine for finishing, just as you would send your planed surface plate to be scraped.

10/10/2021 11:06:29
Posted by Nigel Graham 2 on 10/10/2021 00:01:52:

Going back a bit nearer topic I am fairly sure the Myford manuals tell you the gear standards...

It is a strange thing. Of every manual for every machine tool that I have ever come across, the gear specification is never mentioned.

As a few examples: Myford 7-series; Colchester Bantam, Chipmaster, Student; Harrison L5, 140, M-xxx class; Boxford. Look at every Asian-sourced lathe available new from UK suppliers - how many of them mention the change gear spec.?

You might also explore mills that use change gears (e.g. Harrison, Deckel, Alexander, early Beaver).

It is notable that change gear specs. are hard to find on lathes,co.uk, perhaps the most comprehensive resource available.

Also surprising is that in the many years since the web has been part of our life, no-one has produced a compendium of this information.

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