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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: Gear spec for threading dial
25/07/2019 19:07:23
Posted by JasonB on 25/07/2019 13:05:40:
Posted by jacques maurel on 25/07/2019 11:04:27:

Be careful as the number of divisions must be a submultiple of the number of teeth!


Why would that be? The factory gear is 20/21T and the dial divided into six yet from the chart I posted above it will work with a large range of pitches, infact all that the gearbox can produce.

The dial is divided into six but the usable divisions of the dial with any particular gear have to be a submultiple of the gear's teeth. For the 21t gear, you can only use 1, 3 & 5, which would be 7 teeth apart. For the 20t gear, you can only use 1 & 4, which are ten teeth apart. Poor 2 and 6 never get a look in with these gears.

Could you amend your 3D model to the correct pressure angle? Think about it: is any module gear in the world likely to have a 14.5 degree PA?

The 14.5 degree PA corresponds with the 29 degree thread angle of imperial ACME. Metric trapezoidal has 30 degree thread angle, which would be 15 degree PA (I wrongly stated that it would be 30 degrees in a post above but cannot find any way to correct my error).

Thread: Meddings Driltru Handwheel (Star Wheel) Stiff
25/07/2019 18:39:59

Would a complete replacement bush in metal (perhaps oilite running on the shaft) be a long term option to fix it forever? Maybe the original was cost-engineered.

Thread: Colchester Bantam 1600 3 phase supply
24/07/2019 17:24:38
Posted by Robert Atkinson 2 on 24/07/2019 13:39:14:

Hi Rick,

Have you looked a the existing motor to see if it can be re-wired as Delta (lower voltage) for use on a mdern solid state drive?

He says it is a TWO SPEED motor. Some of these already run delta-connected on 415v. So you cannot delta them again (double-delta?) to make them go on 240v. See:

for typical two-speed arrangements.

I hesitate to mention it here, but the 5hp 240v in, 415v out inverter sold by Drives Direct will do the job but it is rather expensive and it does involve switching downstream of the inverter's output, which seems to be verboten with extreme prejudice on this forum.

Thread: How to cut metric threads on an imperial lathe and vice versa.
24/07/2019 17:04:56
Posted by Journeyman on 24/07/2019 11:33:04:

Only those metric pitches that divide exactly into 90 will be able to use the dial when screw-cutting. Thus pitches of:- 0.5, 0.6, 1.0, 1.25, 1.5, 2.0, 2.5 and 3 will work, pitches of 0.7, 0.8 and 1.75 won′t work.

If you have a 3mm pitch leadscrew, any of the pitches that are a factor of 3 do not require the dial at all. You can remove it and engage anywhere at all.

As long as you use a stop on the bed so the carriage position is known, and close the nuts when the correct mark lines up, the method will work all the time for any pitch of any system of units.

You should pay very close attention to old mart's advice viz: "it is a good idea to make sure the thread dial marks line up with the datum line when the nut is engaged before doing any threading".

That means you need to make sure the dial mark is lined up when you set the bed stop. You cannot just put the stop in a random place (well, you could, but then you'd have to make your own mark on the rotating part of the thread dial to align with the stationary fiduciary mark).

23/07/2019 19:45:33
Posted by old mart on 23/07/2019 14:54:06:

Impossible, it cannot be done, I hear you scream, hogwash, I say in reply.

And to thoroughly silence your screaming disbelievers, suggest to them they should watch the oxtoolco video on YouTube entitled 'Metric Threading with an Inch Lead Screw'.

Thread: Colchester Chipmaster
23/07/2019 19:37:09
Posted by Stuart Bridger on 23/07/2019 16:05:35:

Continental units have a different screwcutting gearbox as well the leadscrew. Mine is imperial, but does have the dual dials. which i have been told is quite rare. Very useful though.

And strangely enough, although the Continental model has an impressive range of imperial threading abilities, I believe the dual dials only work on imperial feedscrews. Hence, you could have imperial threads on a Continental but could not have imperial dials.

The only serious thing an imperial machine cannot do is M12 (x 1.75) threads. However, with 36t and 63t change gears from an ancient Drummond, it can.

Thread: Gear spec for threading dial
23/07/2019 19:15:50
Posted by Michael Cross 4 on 23/07/2019 15:04:41:

For future reference for anyone who might need it, I received this in a helpful PM (many thanks): theory the gears should be helical with the teeth at the helix angle of the thread....

For fullness of answer, one should qualify this by saying it is true assuming you want the axis of the gear perpendicular to the axis of the leadscrew. If you skew the gear to the helix angle of the thread, a standard spur gear can be used. See GHT's headstock dividing attachment for Myford lathes where a skewed worm wheel (the leadscrew) drives the spur bull gear.

If you read the HSM link (and I also think it is in Cleeve's book), many of the common metric pitches do not require a threading dial at all as you can engage the halfnuts anywhere you like.

Thread: Colchester Chipmaster
23/07/2019 14:28:03
Posted by Stuart Bridger on 23/07/2019 08:35:21:

Call me a heathen, but I have always used a 13mm ring spanner for this function. A bit of a loose fit, but given that not much pressure is required to lock the saddle, it works well enough for me.

You can only escape that epithet if you stipulate that it is the Continental model. As any fule no, a 1/2" ring spanner should be used on the imperial machine.

Thread: Gear spec for threading dial
23/07/2019 14:25:49
Posted by Michael Cross 4 on 23/07/2019 12:40:33:

I bet someone knows of an even better fit from something off the shelf.

I know that anything that meshes will work but since I'm going to the trouble of doing it I might as well do the best I can.

Your two statements contradict each other. Either you want to do it right, in which case you need gears with 6mm circular pitch and very likely 30 degree pressure angle, or you want something close, in which case 2 MOD (6.28mm CP), 20 degree pressure angle will do adequately.

Looking at the gear on an imperial Chipmaster TDI, it is closer to parallel-sided stub teeth with a reasonable chamfer on the tips than a true involute form.

I hope you understand that one single gear will not do all metric pitches. Please glance at post number 6 here:

as it contains an image that is worth saving.

Thread: Lathe tooling
22/07/2019 15:47:57
Posted by old mart on 22/07/2019 13:41:20:

Glanze indexable lathe tools are in the higher quality sector, I can recommend them.

In my experience, the tools and retaining screws are indeed excellent value for money.

Where they fall down is the quality of the inserts themselves. I have found them to be uniformly poor.

Hence, if buying the set, budget a little extra for a box of name brand inserts. CCMT06 inserts of the highest quality can be picked up on eBay for little more than a pound each. With the Glanze set containing a tool that allows use of the obtuse-angle of the insert, that's 25p an edge.

Even the very sharp CCGT06 are no more than £1.50 each or 75p an edge.

Thread: Colchester Chipmaster
21/07/2019 09:42:11
Posted by Ernest Shirt on 20/07/2019 23:35:42:

...I’m going to make a new locking bolt with a 1/2” AF hex head and just use a standard 1/2” combination spanner.

Before you make the new bolt, try a 12-point 1/2" A/F ring spanner on the existing square bolt. Because of the chamfered corners, it fits with no more slack than a 7/16" A/F open ended.

If the original spanner was 7/16" square x 1/2" A/F, then maybe a drum brake adjusting spanner can be modified to replicate it.

Please post the tool list if you are able.

20/07/2019 15:40:26

I do not think Colchester ever supplied a spanner for this.

Whatever you make, it needs to be fairly shallow or it will foul the topslide when it is parallel to the spindle axis.

A good place to start might be a gas bottle spindle key and a file. Older ones appear to have more meat surrounding the square hole.

Thread: Unknown object
20/07/2019 09:55:40
Posted by Paul Barter on 20/07/2019 07:58:41:

Any ideas as to why it is supplied with an elaborate means to lock an axis on the gimbal?

Thanks to Michael for digging up the PM thread. To quote from post 14 of that one:

“The indicating needle is 12 ¾ inches long when jointed together, magnifying greatly the slightest movement at the indicating point, and being in two sections it may be carried in the mechanic's kit conveniently.
The needle also passes through the ball, having a split stem, forming a chuck for holding it, and it may be adjusted to any length. The ball is pivoted to form a universal joint but may be instantly converted into a single joint for vertical motion by merely tightening the knurled knob, adapting it for inside and outside surface contact. A steel ball about .175 inch in diameter slips over the point for inside work. . . .”

So you need to make it uniaxial if not using with a centre-punch mark.

Very clever, those old boys.

20/07/2019 06:59:26

I think it is a precursor to a dial test indicator, used for centring up work in a four jaw chuck.

There is a long, slender rod that goes through the collet. The end of this locates in a centre drilled in the work. The length of rod between holder and workpiece needs to be relatively short; the free end relatively long to amplify any out of trueness. When the free end stops wobbling about, the work is true.

Thread: Myford ML7 tailstock bore, and threading the barrel to fit a chuck
15/07/2019 20:56:14
Posted by Mike Donnerstag on 15/07/2019 19:19:04:

Also, can anyone tell me the maximum travel of the ML7 barrel?

9 1/2" long.

Overall travel is 3 1/2" but that starts 1/4" inside the casting. So 3 1/4" starting with barrel flush with casting.

You will lose some of this depending on how much you use gluing on the chuck.

15/07/2019 17:47:19
Posted by JasonB on 15/07/2019 16:27:23:

Am I missing something as I can't see how you will be able to advance the tailstock mounted chuck towards a driven drill bit if the bow is poked down the tailstock barrel and out the back so no screw can be fitted.

ML7 tailstock is hollow. Hence why it is not self-ejecting unlike Super 7 which is not and which is.

9/16" bar goes through. 5/8" bar does not.

Barrel diameter is 1".

Make thick washer ID 1", OD 1 1/8". Loctite ID to barrel. Loctite OD to chuck register.

If force of drilling overcomes loctite, use MIG welder.

Thread: MEW 283 Electronic Leadscrew link
12/07/2019 07:07:00
Posted by SillyOldDuffer on 11/07/2019 14:08:47:

(Be careful buying encoders - I accidentally ordered a 1000 positions per revolution encoder due to not reading the small print...)

Can you modify your code so that it reads every edge of the quadrature pulses? Then the 1000 ppr magically transforms into 4000 ppr.

Thread: Modding a fixed steady
01/07/2019 08:40:57
Posted by JasonB on 01/07/2019 07:02:51:

Just use them without the screw adjuster and the small grub screw that the adjuster is retained by.

Then you are relying purely on the grub screw in the finger groove to stop them moving.

In the original design, the lower grubscrew acting in the groove (the one with the locknut on it) is purely for rotational location purposes. It should be dog-pointed and a good fit in the groove. A nylon tip might be a good idea so a little axial friction can be applied to the fingers but this screw should never be used for locking. The reason for rotational fixity is so the bronze tips can have line contact with the work rather than point contact.

Right now, the axial thrust of the fingers goes into the threaded adjuster and is resisted only by the top grubscrew in its groove. This is the worst part of the design. If you are to reengineer it, some kind of bronze thrust washer here to resist the axial force is needed. This then lets you use the upper grub screw (or replace with knurled screw for toolless use) for locking purposes, just stopping the threaded bit from rotating loose due to vibration.

Ream out the bores to the nearest size of ground MS or silver steel bar, make two sets of fingers (one same length as standard, one shorter so full capacity is possible) with keyways to fit dog point grubscrews (may need to fettle the grubscrews as well for concentricity of dog and constant diameter).

What you have is a good starting point that just needs a little easy tweaking.

Thread: Square Headed Screw Supplier
30/06/2019 20:11:31
Posted by Vic on 29/06/2019 20:10:12:

I wondered why they used square head screws. Must say though that I’ve not had any problems with swarf when using socket screws in my four way.

The (normally four) holes in the holder are so close together that the points of standard hex. screws would clash.

27/06/2019 07:36:16

Have a look at

This gives relevant DIN standards, which are useful as search terms.

Long time ago, I bought M8 ones from Nu-Screw in Neasdon, about £40 per hundred, but I cannot find their website any longer.

What is wrong with dog point hex. grubscrews in your application? I like them better than traditional sqaure head as they are cheap, you can pick a length to suit the tool being clamped so they do not poke up so much that swarf wraps around them.

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