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Member postings for choochoo_baloo

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

Thread: Fitting a 5 micron DRO to Myford ML7
11/04/2022 16:15:16

I'm doing the research to buy a DRO for my Myford ML7. However I just read that the generic DRO are, unsurprising basically two board manufacturers both of which are based on metric.

Thus those of us, me included, who work in Imperial, reckon we must be aware that a 5 micron read-head can produce tangible rounding errors in the tenths digit, since all metric to Imperial conversion is done in software.

Obviously it's trivial to show 5 micron = 0.0002 " (1 sf).

My question is, practically, do 5 micron read-heads matter for an ambitious ML7 user hoping to aim for sub 1 thou tolerance? (from time-to-time; not always!)

Thread: Why aren't carbide chop saws used?
31/03/2022 00:58:47

I'm looking to buy a metal 'stock cutting' saw. The manual hack saw is getting tiresome...

It seems almost all hobby workshops seem to use either the ubiquitous 4x6 bandsaw or power hacksaw.

Why aren't modern chop saws used?

Especially since it seems the modern carbide tipped variety have overcome the dust/heat/sparking of the abrasive type; which is obviously a major deterrent in a small workshop! They're competitively priced too.

Thread: Is this 3 phase motor suitable for delta/VFD?
25/03/2022 19:59:02
Posted by Andrew Johnston on 25/03/2022 18:49:25:
Posted by choochoo_baloo on 25/03/2022 18:29:45:

...can supplying 240V 3ph (so approx half the rated 3ph voltage) actually harm an induction motor?

In a word - no. Running a 415V star connected motor with 240V phase to phase simply reduces currents, and hence torque and power, by the square root of 3.

Andrew

Thanks Andrew. Good to know that all it would do is simply 'underpower' the motor.

Just for my own understanding - only a minor academic point - wouldn't a star connection actually run at one third* of the motor rated power; whereas in delta each winding receives line voltages (415volts) and operates at full rated power?

*using power equation: P /prop V^2 so P /prop (1/sqrt(3))^2 so P /prop (1/3)

25/03/2022 18:29:45

One theoretical point a few of you have mentioned, I'd like clarity on:

can supplying 240V 3ph (so approx half the rated 3ph voltage) actually harm an induction motor? Or does it simply reduce the torque across all supply freq's supplied by the VFD?

NB: I'm quite happy with the physics in terms of their actual operation. The rotating B field induced by the 3 120deg stator winding pairs should behave as intended, just with lower magnitude when flux linking the rotor squirrel cage. Surely?

25/03/2022 18:21:20

Just managed to sort out the mass of photos on my computer - just created a new "Tom Senior M1" album. Should make future questions more straightforward.

Important point I forgot: I'm undertaking this to give my adjustable table feed rates via all the pulleys and gearboxes on the back of the column. 90% of the time I envisage using the powered S-head for the actual cutting. Does this constitute a 'light duty' application?

Please see "3 phase column panels" photo, as below. The 3 phase supply is tapped off for the Lo-Vo lamp, with it then going through to the handsome Brook enclosure that had the ON&OFF buttons (cover removed). Can connections be used in some way?

Then again the Transwave Layman's guide is clear that

the VFD should be wired straight to the motor with no paraphernalia in between.

3ph panels on column

 

Edited By choochoo_baloo on 25/03/2022 18:23:00

Edited By choochoo_baloo on 25/03/2022 18:31:53

25/03/2022 02:59:04

I'm planning to convert my Senior M1 to VFD. Transwave's helpful "Converters and Inverters - layman's guide" is a lucid overview of the process, well worth a read.

BUT...the original Crompton 3ph motor states 400V and I'm wondering whether these connections can be changed to delta/240V as required by inverters. Why does it lack the {W2, U2, V2, U1, V1, W1} that I've read about? Perhaps hiding behind that fibreboard?

(NB I can't get to the motor for the time being for a fiddle, so am relying on these old photos.)

3ph_plate.jpg

3ph_terminals.jpg

Thread: Using kerosene to clean ground surfaces
24/03/2022 19:22:24

Thanks all for the info - comprehensive as ever. Being a perfectionist, want to clarify the slightly differing opinions:

The tools permanent home is an insulated and heated workshop - fortunately rusting never seems to occur.I've already started my clean "kerosene + clean rag" method on some centres.

Is the consensus that I should now be re-lubing with say WD40. Or the fact that they're going to now be properly stored in said warm environment mean I can stop there? I suppose what I mean is, should mating surfaces be left preferably bone dry or with a protective film?

24/03/2022 01:17:29

After an unexpected workshop hiatus, my lathe centres/QC tool holders/a few new drill shanks (in other words ground surfaces) collected some detritus & a little grime.

I plan to give them a brush with some kerosene then dry the excess with a clean rag.

  • Does kerosene leave a thin film, so serving as a rust inhibitor?
  • Is it OK to leave this film on mating surfaces ie on a QCTP tool post, in operation ie does it affect the accuracy?

Thanks in advance.

Thread: Engineering tuition recommendations
18/03/2022 01:36:21

Sorry chaps, realised I may have unintentionally set the wrong tone. I meant to say:

I am a great believer in self-teaching etc; have done so in many areas myself. His forum ha been invaluable over the years for my numerous beginner questions. It's because I aspire to tackle some hefty engineering projects in due course e.g. 4" scale traction engine, I would rather gain a good grounding from an experienced machinist to really 'learn the tricks' that no books could ever practically cover in their entirety. I think I'm trying to be realistic(?)

Otherwise it would be many years, large amounts of money on 'learning by experimenting', and most concerning is waning enthusiasm as progress stalls. Death/illness aside, I do see a lot of part finished mod eng projects for sale from the various dealers.

Hopefully that makes more sense?

Edited By choochoo_baloo on 18/03/2022 01:37:43

17/03/2022 19:49:06

I'm trying to find manual machine tool tuition. Aimed at a serious hobbyist who is bereft of any formal training. I'm keen to acquire a range of skills, over time of course, from a very competent engineer (who's ideally undertaken rigorous training in the form of a traditional apprenticeship). I've now decided I won't be satisfied continuing to self-teaching bits from books and youtube videos.

Surprisingly I'm struglging to find any sort of night school courses at local colleges, even within a 2hr radius. Granted I live in the West Country...

Even those introductory courses Axminster Tools ran down in Devon seem to have been discontinued.

Any suggestions are gratefully received.

Edited By choochoo_baloo on 17/03/2022 19:49:42

Thread: Ferrous, facing, HSS tool geometry
26/10/2021 14:32:30

This is precisely what's keeping me going on this long path, Lee wink

Posted by Lee Rogers on 24/10/2021 15:59:33:

Above all enjoy the day when you turn out a perfect finish with a tool that you made .

25/10/2021 02:16:43

So I knocked up a LH knife tool to use parallel to lathe axis as was advised. Pleasingly it produced a smooth/free cutting finish.

BUT...I noticed after a second pass (silver steel round) the tool developed a little knick at cutting edge. Thta would explain why, despite being bang on centre height, the final few mm of inward travle has a much rougher surface finish. Please look at the photo; I've circled the defect. Sorry but it's hard to expose correctly given the shiny steel (told you surface finish was otherwise good!)

All of this, is to ask: is the generic HSS to blame (cheap bundle from RDG) ie should I upgrade to a better quality HSS blank? Admittedly I'd assumed that on hobby machines at least, HSS was much of a muchness.

Has anyone bought Rennie HSS blanks (pleasingly they're made in England). I think I'll try some of these.

https://www.rennietool.co.uk/collections/all-toolbits

 

Edited By choochoo_baloo on 25/10/2021 02:17:03

Edited By JasonB on 25/10/2021 08:51:54

25/10/2021 02:05:04

I should have said in OP, I have been trying to follow Sparey's approximate geometries; without obsessing about angles.

And yes been using a simple tilting table on my bench grinder. Honed the corner and working edges with a DMT diamond hone - must say I'm pretty pleased how tools turned out.

Thread: Collets for Myford tailstock
23/10/2021 14:22:29

Thanks chaps, appreciate all the advice.

I should have said that it was actually Cutwel technical advisor who recommended this. So in the spirit of sharing knowledge, they advised: (who themselves do lots of proper engineering themselves),

For a Myford size, power tapping with tail stock collet is the smart choice esp can maximise squareness and rigidity. Furthermore the motion of hand tapping actually slightly degrades the thread form due to the repeated forward and backward necessary to clear chips. Cause a slightly looser fit. Plus get the powder metal HSS which are more shock absorbant by their nature.

(Must say was refreshing change to have a long friendly chat with experts. On phone for about 30 min!)

Edited By choochoo_baloo on 23/10/2021 14:24:02

23/10/2021 03:25:17

I want to give power tapping a few metric on my ML7 a go whereby a machine tap is held in the tailstock.

To do so will require the tap to be held in a tailstock collet. I already own the Myford patent collets (those using a 1 1/8" Whit closing ring). Annoyingly I can't see these workign on the taslktock becuase any required adaper would constrict the 2MT bore.

So if I need to source another collet design,simplcity and cost, woudl plain 2MT collets suffice:

https://www.arceurotrade.co.uk/Catalogue/Collets/Morse-Taper-Collets/MT2-Collets-Metric-Sizes

If so can I use M10 studding with a washer and nut at far end of tailstock barrel for the drawbar?

Thread: Ferrous, facing, HSS tool geometry
23/10/2021 02:45:26
Posted by Ramon Wilson on 22/10/2021 23:35:20:

I've been advocating using HSS on a Myford (as opposed to insert tooling) for many years now but I confess that when it comes to grinding 'correct' profiles I'm hopeless cause.

Fundamentally I have three basic shapes on the go all the time one left hand knife for turning, one right hand for facing and a tapered round nose tool for finishing either. This latter is probably the most used 'stock' tool.

If possible could you upload some photos please? As said above, I am keen to learn more about effective HSS grinding!

23/10/2021 02:43:39
Posted by not done it yet on 22/10/2021 23:13:30:

There is not too much need for ‘experimenting’ - it has all been done time after time and more times. Stick to the accepted norms is my advice.

That's precisly my point; I've struggled to find much (Sparey aside) on HSS geometry for facing.

Turning/boring/parting all have plently of references. Just struggled to find many for facing.

23/10/2021 02:41:03
Posted by SillyOldDuffer on 22/10/2021 18:14:46:

Sparey's "The Amateur's Lathe" is my bible when it comes to HSS.

One of my older books, can't find the stupid thing, tabulates a full page of different tool shapes for roughing, finishing and other purposes. I suspect the variety of shapes date from the Carbon Steel era: in comparison HSS is very forgiving.

With a knife, Sparey suggests finish is achieved by setting the tool almost parallel to the work to produce a rubbing action in conjunction with slow turning speed, fine-feed, and plenty of lubricant. Works for me.

Thanks Dave I have read that chapter of Sparey. When I tried to follow his advice (ie RH knife for facing) I suffer chatter each time.

...Does Sparey mean swapping in a LH knfe, exploiting this rubbing, and moving perpendicualr to the end face? I admit I found his bit unclear.

22/10/2021 16:50:55

Hello all. I'm new to home metalwork, and have at long last had the time to start experimenting with grinding my own HSS tools for my ML7 lathe.

I'm now experimenting with obtaining the best surface finish when facing steel(s), and am hoping this thread can be a convenient reference for me and others to learn other approaches. I gather HSS tooling is rarely 'only one way will work'.

My current approach is:

use parallel (to lathe axis) QCTP station, ~ 1mm radius round nose, LH so as to cut into the centre. (I will upload a photo later when I get chance!)

Please do contribute, all advice gratefully received.

Edited By choochoo_baloo on 22/10/2021 16:51:59

Thread: Under & over reamers?
30/09/2021 23:58:09

More a curiosity for me at this stage

I just watched a machinist video whereby the nomial diamter of a silver steel dowel didn't have a smooth sliding fit into a reamed hole. She then explains that's why 'under/above reamers sets' exist. Presumably, in Imperial, these would b +/- 1 thou of the nominal size? I've seen a couple of American sellers offer them.

After some searching, no one in this country seems to sell them? Is it instead common practise to buy buys the explicit reamer size e.g 0.501" for an oversize 1/2" hole.

Would appreciate some clarity on this. Thanks in advance.

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