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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: Colchester Student mk1 change gears
03/03/2020 18:08:00
Posted by Drew Mason on 02/03/2020 21:13:25:

My second question is, would anyone out there have a set of original 42/35/21T gears that they would part with? Or even just a 21T gear?

If the gears used on this lathe are hard to come by, you can help yourself by familiarising yourself with gearing nomenclature and finding gears of the same tooth specification. You need to know Diametral Pitch (DP) and Pressure Angle (PA). Most easily digestable reference is Ivan Law's book in the Workshop Practice series.

If you report these details here, we can tell you which other machines share the same tooth specification.

If the centre detail does not match your existing ones, this is normally easy to modify (could be as simple as pinning the new gear concentric to one of the old ones).

There is a seller on eBay whose user ID is you_engraving who makes delrin change gears at very reasonable cost.

Thread: Threading with inserts
27/02/2020 16:13:23

Posted by David Colwill on 27/02/2020 13:04:00:

Interestingly not all insets have the second tooth. The photo shows two 1.5 mm pitch inserts...

I hope I am not telling you something you already know, but are you aware that threading inserts come as full profile, suitable for only one thread pitch and as partial profile, suitable for a range of pitches?

Full profile ones look like that on the left, where the second tooth finishes the crests.

While both the inserts you show may be able to cut a 1.5mm pitch thread, only one of them is strictly a 1.5mm pitch insert.

Partial profile metric are usually labelled A60, G60 or AG60. Full profile will have a number for the pitch as part of their label.

Thread: Bantam feed not working
15/02/2020 10:23:39
Posted by not done it yet on 15/02/2020 08:24:48:

You have learned that it is never a good idea to use a solid stop when under power feed!

That statement is not universally true. The Bantam (and Chipmaster) have a very clever mechanism that allows precisely this. If the manufacturer of the machine has given you this facility, why not use it?

15/02/2020 08:37:18

As Steve says, attack this logically. It is just a machine.

Do you have a manual for it? If not, please obtain one as all Colchester manuals have full exploded diagrams of the entire machine. This will tell you how the spindle links to the feed mechanism and where the shear pin may be.

If you find a manual online, please post a link so we can all look at it.

When you were cutting, were you using the leadscrew and halfnut (lever at headstock end of apron)? Or the sliding feed (lever on face of apron below cross-slide hand wheel)? The sliding feed should disengage automatically when hitting the stop. The leadscrew will not.

The sliding feed disengagement is all in the apron so it may need cleaning and lubricating.

Any shear pin will be in a place semi-easily accessible and not buried inside the gearbox.

The gears may be rotating but often one of them is on a carrier that is (shear) pinned to its shaft.

Put a pair of soft-jaw pliers on the feed shaft near the tailstockand turn it gently. The output of the gearbox where the leadscrew dog-disengagement should also turn. The output shaft of the gearbox where the change wheel is should also turn. If the SHAFT turns but not the gear, that is where the shear pin is.

Thread: Another - What is the correct name for this
03/12/2019 19:29:22

The thing that immediately comes to mind seeing your sketch is a planer gauge. As the name suggests, however, it is a measuring tool and not really designed for workholding.

Thread: Meddings LF2 pillar drill
01/12/2019 08:16:15

Any Meddings will be a good drill, so long as it has not been totally abused.

As JohnF says, the deciding factor may be whether it has a single speed or a two-speed 3-phase motor.

A single speed motor is relatively easy to convert to 230v three phase and run from a VFD, even if you have to dig out the star point of the motor.

The eBay link is single speed motor (see photo of the name plate - two speeds are given but only because of different power grid frequencies).

A two speed motor is very difficult to convert to lower voltage operation.

Thread: M24 x 2 arbour
28/11/2019 08:38:51
Posted by Emgee on 27/11/2019 22:00:28:

Get yourself a blank end MT2 arbor and thread it in the lathe.

All the boring head arbors I have seen are flanged after the thread, to stop the head screwing itself into the spindle. Finding a MT2 blank arbor of big enough diameter to accommodate this may prove challenging.

Thread: Tailstock indexing
24/11/2019 20:54:38

See:

https://www.model-engineer.co.uk/forums/postings.asp?th=140386

where a graduated Myford LEADSCREW handwheel is repurposed for use on the tailstock.

Thread: Acme thread
24/11/2019 08:30:53
Posted by Shaun Belcher on 24/11/2019 00:17:30:

Myford claim its 10TPI for the imperial feedscrews, but only say the metric ones are 3/8" 2mm pitch.

I think what this means is that the outside diameter of the screw is 3/8" but the pitch that is cut on it is 2mm.

Basically a metricated version of the imperial screw, the only change being the distance between the thread crests. It means all the stuff at the handle end will fit unchanged.

Thread: Myford Super 7 Metric thread cutting gears
24/11/2019 07:55:14

Until someone more qualified comes along, please have a look here:

https://www.model-engineer.co.uk/forums/postings.asp?th=125630

as I think it will answer most questions.

Thread: Operating manual for a Harrison 140 metric lathe
12/11/2019 14:52:22

Type 'Harrison 140 imperial threading' into Google.

Inter alia, it will find

https://www.mig-welding.co.uk/forum/threads/gear-cutter.56392/page-2

and

https://www.mig-welding.co.uk/forum/threads/advice-on-lathe-purchase.62989/page-3

These may shed light onto your problem.

Most unlikely to have a 6cm leadscrew unless it has come from a dressmaking shop or is ex-Blue Peter.

Thread: Drilling big holes (in tiles)
09/11/2019 18:49:49
Posted by JasonB on 09/11/2019 16:28:43:

Use it to drill a hole through some 6mm ply or MDF then hold that against the wall to guide the holesaw until it has started the cut

Holding the guide in place is not easy, especially on a slippery tiled surface. If time is not pressing, glue the guide on 24h in advance using hot glue or silicone.

I agree with the others that a small hole is all that is necessary. With a bit of careful measurement, you can drill on centre of the tap, expose the screw holding the handle on, remove the screw and handle and use a square socket on an extension to turn it. Remember when finished not to leave it fully open.

Thread: INT30 sensitive drilling attachment
09/11/2019 13:55:13
Posted by Mark Davison 1 on 09/11/2019 09:38:15:
The bit I still cant picture, even after study the drawing you sent (thankyou) is which way up the adapter mounts to the nose. I'd have assumed the ground face mates with the nose but the assembly drawing suggests it goes the other way, with he ground face down?

Sorry, I thought I had added a note on the email. The assembly drawing is incorrect, my fault. The ground part is up, the counterbored holes are down.

To me, it is an easy part to reproduce, needing precision only on two concentric bores, one for the spindle nose, the other for the ER holder.

Thread: Boring bar toolpost.
03/11/2019 16:31:48

This may be a wildly foolish idea, but if there is any uncertainty over deflection, could you put gussets under and behind the bar?

How much is there between the outer face of the bar and the point of the tip? You could shrink or loctite on a sleeve that increases its effective diameter. Even an eccentrically-bored one so that the under and back get more meat than the front.

Thread: INT30 sensitive drilling attachment
02/11/2019 08:46:19
Posted by old mart on 01/11/2019 21:14:15:

Its a difficult project, what with the core diameter of the pull stud being only 9.85mm and some method to allow the chuck shaft to move axially and turn with the toolholder via a keyway or similar. The stroke will be severely limited, if the whole assembly is not fairly long.

These sidelock spindles may have the answer to the finish of the bore and the screws could drive a slotted spindle.

**LINK**

The sidelock holders do project downwards so a bit of headroom is lost.

Your idea of a boring head shank is very good. They are unlikely to be through hardened and a nose cap could be used to hold it into the spindle, thus eliminating the troublesome drawbar. Think Myford spindle nose MT2 collets. Cut the top off it as necessary as the full length of the taper is not needed for axial drilling loads.

You could use the threads originally destined for the boring head to screw on an unhardened piece that provides the sliding drive system.

Was is Erikson who did a quickchange toolholding system for Bridgeports that used a cap to retain the tooling instead of a drawbar?

In practice, stroke length is limited by lever ratio at the top end. 6:1 ratio, for instance needs lever to go 300mm for 50mm quill travel.

Edited By DC31k on 02/11/2019 08:48:51

02/11/2019 08:37:07
Posted by Mark Davison 1 on 01/11/2019 20:35:05:

I was hoping to use at least some of the depth of the INT30 taper so as not to loose too much of the available height.

Using a spindle nose cap, it can project upwards into the taper to give the height and length for support, but does not need to be machined to fit the taper.

31/10/2019 16:42:49

Have a look at how Schaublin do their sensitive drilling attachment for the 30 taper spindle on the 13 mill.

It locates on the spindle nose itself, like a big facemill would.

Much easier to make than something that locates in the taper.

You need to think of how the drive will be transmitted while still allowing sliding movement. Generally done with a key and keyway. A dog point grub screw into the 3MT adaptor could be used, but requires tapping a hard part. An accurate keyway is equally difficult in a hardened ER straight shank chuck.

Copying the Schaublin design would allow you to put keyway in unhardened spindle nose adapter and use angle grinder to form a not-very-precise-over-wide slot in ER chuck and then JB Weld in a key (using the adapter to keep it aligned while it sets).

See bottom left of page 6 here:

https://drive.google.com/file/d/0Bxr59DtuJda_amx1V1dvNE8xVXM/view?usp=sharing (Anglo-Swiss Tools, Schaublin 13, French catalogue)

for nose dimensions. Top right of page 12 for attachment complete.

I have a drawing for all the Schaublin parts so if you PM me with contact details, I can send to you.

Thread: Additives to kerosene for degreasing?
30/10/2019 19:48:28
Posted by Mark Rand on 30/10/2019 16:48:55:

If I were braver/more informed, I'd probably find a suitable detergent to add to straight kerosene.

If you look at the MSDS here

https://www.img-limited.co.uk/wp-content/uploads/2015/01/Blue-Jet-Degreaser-CLP-MSDS-Sheet-FULL-1.pdf

it is just kerosene with IPA (propan-2-ol) and a bit of ethoxylated oleic acid (which is a fairly generic non-ionic surfactant).

This is one of the few data sheets I found that actually list the minor ingredients; most others just say 90% kerosene and stop there.

Thread: SHAPER ACCESSORIES
29/10/2019 19:41:22

Ian Bradley's 'The Shaping Machine' contains drawings for a small and large hacksawing tool (pages 41 & 42). Rather smaller that that shown above.

The NEME-S website (http://www.neme-s.org/) has an online shaper reference section.

Thread: Tools of unknown types.
29/10/2019 07:02:28
Posted by John Reese on 29/10/2019 00:41:46:

There a lot of similar collet chucks on the market. They are definitely not ER type collet. They resemble Acura grip or TG collets but my not be compatible with either system.

I think the ones shown are known as Oz collets.

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