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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 Chipmaster Part
11/10/2019 21:51:30
Posted by Paul Valente on 11/10/2019 16:35:46:

I’ve actually got the piece down to the base of the taper.

All I really need is an exact length for the threaded portion.

Which piece do you have? The hexagon part that lives in fresh air or the 1/4" UNC part threaded into the headstock? If the part threaded into the headstock through the aluminium cover is not there (i.e. the female threads in the headstock are clear), it might be a good idea to look inside the headstock to make sure it has not worked its way in there.

This is a situation where you will be really happy to see the broken off end of the fastener in the casting.

A countersunk fastener's length is always given from top of head to end of screw so the length of the threaded part itself is not usually given. Your assumption is correct, so what you have to do is determine the countersink angle. I did not tell you this as I cannot remember if UNC is 90 degrees or 82 degrees. Simply remove one of the other screws nearby and copy it.

11/10/2019 14:46:19

Two thirds of it is the same as one of the adjacent 1/4"-20 UNC x 7/8" long socket countersink screws that hold the cover on (including the countersink angle).

So remove one of those to have 67% of your drawing.

The rest of it is a 9/16" A/F hexagon, 7/16" long with a 3/8" diameter groove in it, 0.150" wide.

The remaining 33% of your drawing can therefore be determined by measuring the width and thickness of the semi-circular cut out in the splashback.

Thread: 3 Phase
29/09/2019 07:40:59
Posted by peak4 on 29/09/2019 00:31:57:

Old Mart, there's a little bit more to it in that each of the three windings need to be in the correct orientation...

The motor will run rough and overheat otherwise, as one coil will be working against the other two.

Could you kindly describe or post a credible diagram showing how it is possible to put the windings in an incorrect orientation.

Reversing the ends of any winding is exactly the same topographically as swapping over two wires of the supply. This is the standard method of making the motor turn in the opposite direction.

Thread: Aciera F3
16/09/2019 21:06:48
Posted by Ian Lee on 15/09/2019 22:27:18:

...my question is does anyone know the external dimensions of the collets or does anyone know where I can get a drawing...

If you put in such terms as 'W20 collet drawing' or 'W20 collet dimensions' into Google, you will find what you seek.

Not yet mentioned above as sources are small-lathes.co.uk and www.rcm-machines.com, the latter being very good as they have an ER32 holder on a W20 shank for 89 Euros. They also have a W20 internal thread to M12 adaptor (good start to a drawbar). Should you need a suitable W20 tap or die, they are available from China on eBay, denoted as SV20 thread. For screwcutting, do not be put off by the strange looking thread pitch - think in fractions rather than decimals and gear the lathe 5/3 of 1mm.

Thread: Myford 254 thread dial indicator
09/09/2019 19:57:59
Posted by Philip Slater on 09/09/2019 19:09:58:

I've never machined gears but I've got a milling machine so have the tools. Thinking aloud I wonder if I could machine the gears from Tufnel. Not sure what you mean by having 2 gears, are you saying you need to change gears on the Thread dial indicator?

Do not be alarmed: a thread dial indicator is in no way a precision mechanical device. Almost any kind of tooth shape will work; the important thing being the number of teeth (even so far as straight gashes around the perimeter of a thin gear.

You would do very well to buy Martin Cleeve's book on screwcutting as it probably the most concentrated source of information on leadscrew indicators out there. You can also search this site (using Google with site:model-engineer.co.uk as part of the query string - since the forum search is totally useless) as the subject has been done to death here as well.

Very briefly, thread dial indicators for an imperial leadscrew are very simple because of the way imperial threads are defined (teeth per inch) and one gear will do all pitches.

TDI for metric leadscrews are more complicated because metric threads are defined by pitch. One gear will not do all pitches. However, in some ways metric pitches are simpler because any pitch that is a factor of the leadscrew pitch does not need an indicator at all - you can drop the nuts in anywhere they will engage.

For your 3mm pitch leadscrew, this means 3.0, 1.5, 1.0, 0.75, 0.6, 0.5, 0.3, 0.25 and 0.2 pitch threads do not need a gear. The remaining common ones (especially 1.25 and 1.75) will need an indicator gear (1.25 needs a gear with teeth 'by fives' and 1.75 needs a gear with teeth 'by sevens'.

Thread: wire bender
07/09/2019 16:15:21
Posted by duncan webster on 07/09/2019 16:02:20:

I want to buy a tool, got far too many other jobs on the go to start making one, I just need pointing at where to get it

Put 'wire bender' into Google images. There is one common design that seems to be sold by many people, so make your choice of seller.

If there are many to do, stacking three or more wires on top of each other and pulling the loops all at once will speed things up. This is how small reinforcing bar is bent.

Thread: 4 jaw Self centering chuck recommendations please
03/09/2019 17:12:44
Posted by peak4 on 03/09/2019 10:55:29:

Has anyone seen a vendor offering these with a set of outside jaws included (or even available?)

The only off-brand one I have seen with both sets of jaws is by a seller called niuniucme on eBay. Unfortunately, they are in US but if you have a contact there, it may be of some use.

For brand name ones in UK, Rotagrip are competitive.

Thread: ACME thread identification question.
02/09/2019 20:42:27
Posted by Pete Rimmer on 02/09/2019 14:00:47:

They specified the OD for the blank for rolling the thread on the imperial cross slide screw to 4 decimals.

But could that be because the thread forming process (rolling) is quite fussy in that respect? Maybe if checking using three wires, this is the diameter that gave correct results.

It may be similar in concept to thread forming taps: for success, you need to be a lot more careful in your tapping drill selection.

Thread: Substitute for limonene
30/08/2019 07:49:41

I am not a chemist but...

... is there something different about HIPS that makes standard polystyrene solvents unsuitable? Or are most polystyrene solvents also ABS solvents?

The Wiki page for limonene says it is used in paint strippers (I think one US one is Citristrip). This page might be a guide to alternative sources.

Do some experiments. Put some strands of HIPS and ABS into a few glass jars and fill with solvent of your choice. Come back next morning and see what remains.

Thread: Tool post project
29/08/2019 07:17:39
Posted by Jeff Dayman on 29/08/2019 00:14:27:

The proposed designs will not restrict the 6 degrees of freedom of the toolholder.

But in what way is it lacking? The only one I can see is non-repeatability of rotation about the clamping stud. In all other directions it seems OK (if one agrees that it does not need to be restrained from pulling into the workpiece).

To the OP, it may be worth thinking a little of the QC aspect of the design. Right now, to change a tool fast, it has to go towards the centreline of the lathe. This means winding the carriage back past the end of the work or winding the cross slide back to give clearance. If you need to remove the tool (perhaps to measure something) without altering your settings, this may annoy you.

Thread: Boxford Shaper Table Lock
27/08/2019 17:04:48

You are correct that there is no horizontal lock.

If possible, try to cut down the right hand side of the work as you stand in front of the machine. Then the cutting pressure is trying to stretch the leadscrew, nut and restraining collar. Once the lost motion is taken up, it should be solid. Exactly analogous to turning with a lathe. About the only time you need a cross-slide lock there is for an interrupted cut (hex or square turned to round) where movement is due to vibration.

Perhaps do a test piece with an indicator bearing on the side of the table and see if it moves at all.

I do not think two stops would be needed as the table should not move towards the cutting pressure. If needed at all, one should be enough.

Thread: ACME thread identification question.
25/08/2019 18:50:11

Can you describe the graduations on the cross-slide dial please. How far does the cross-slide move when you rotate the wheel one turn? Take a marker pen and trace round the crest of the thread and tell us what you see.

There is a possibility it could be 5tpi two-start.

Thread: Lathe tool holder
24/08/2019 17:28:54

If there are many holders and only one toolpost, could you shim the toolpost itself?

Thread: Mystery Tooling
16/08/2019 06:50:52
Posted by Kiwi Bloke on 14/08/2019 22:24:23:

Thanks to the set-up pic, you've provided the clue - it's a travelling steady. Clever design for its simplicity.

It is a bit of an unusual travelling steady as it is bolted to the crosslide. To make it work, one would need to put the cut on with the topslide.

Thread: Slitting Saw - which one?
14/08/2019 07:05:48
Posted by ChrisB on 13/08/2019 09:47:16:

slitting saw.jpg

There is very little advantage and lots of disadvantages cutting it the way you show.

Right now, the teeth are cutting almost vertically. It might pay you to reduce the depth of cut so the lowest tooth on the saw just breaks through the wall of the tube. In this way, the teeth are cutting much closer to horizontally and the length of cut is at its maximum.

If you have some spare material, or similar material, turn up a close fitting plug for the bore and low-strength loctite it in. This will greatly increase the rigidity of the part and stop it flexing and trapping the saw as more cuts are put into it. Slitting saws do not like vibration. With the plug, and semi-horizontal cutting, you might be able to sneak a centre and tailstock support in. Even if not, support the outboard end with a jack.

Consider the pros and cons of conventional versus climb cutting here. Conventional will try to lift the part off the table, but you are always driving the work into the saw. Climb will push it down onto the table but the saw will try to self-feed.

Me, I'd grind the set off a hacksaw blade, sandwich it between two parallel guides and be done with it. Was it Sir Tubal or Uncle George who ground teeth in a feeler gauge to cut a very narrow slot?

Thread: Small Volume PCB printers?
13/08/2019 18:37:37

An possible alternative depending on number complexity, size, holes, etc. is to import the scan into your CAD program, trace over it to produce a vector file and then CNC mill or route it from copper coated board.

Thread: Chosing a drill grinding attachment or machine
10/08/2019 11:05:23
Posted by Clive Foster on 10/08/2019 09:55:41:

Drill carrier is ingenious being a proper pair of Vee blocks segmented toast rack style so anything between 2 and 20 mm can be held.

Seeing the picture, the carrier is the same principle as the Tormek drill sharpening attachment. The Tormek one is also worth looking at to see if it meets your needs. You can buy the attachment separately from the grinder.

Thread: Bulking problem?
10/08/2019 10:59:01
Posted by BRIAN RICHMOND on 09/08/2019 21:05:08:

I have tried using a battery of Mikalor heavy duty clips along the entire length boiling the horn and then tightening the clips. This works a treat initially and really pulls the horn in quite easily.... However when you reach a certain point and the torque increases the threads just strip on the clips.

How elastic is the material? How quickly does it spring back when a clamp is released?

The Mikalor clips have a range over which they are designed to clamp. Exceeding this will, as you have found out, lead to breakage. Once you reach the lower limit of a particular clamp, you might have to release it and replace with a smaller one.

One principle of the piston ring clamp that you might borrow is the spiral of spring steel that surrounds the rings. If you put something similar on the horn, and then the Mikalor clamp over it, the spring steel should slide over itself, especially if lubricated, and reduce the force needed.

Thread: Adjustable 3-jaw chuck designs
05/08/2019 20:03:40
Posted by Bob Stevenson on 05/08/2019 17:28:00:

...........I did toy with the idea of acquiring another 3 jaw and skimming out the register for the 'copper mallet' method but the WM180 has chuck fitting which is the Chinese 'bolts for little fingers' method of fixing and I'm not keen to open up the bolt holes in the spindle plate. The chucks are purposely tight on the register enough that i have to use a brass plate against the headstock to 'jack' the chucks off using the fixing nuts as jacks......

I think your idea has merit and could be done with no alteration to the machine if you had a sub-plate between chuck and spindle register.

The thinnest arrangement would be with a front-bolted chuck to sub-plate and a chuck register larger than the spindle register (so they telescope slightly).

A rear-fixed chuck would need a thicker sub-plate and maybe bolts with holes drilled in the sides for a tommy bar (look up 'capstan nut' for the concept).

Thread: Furrows on a milled edge
05/08/2019 19:49:43

You could try vacuuming up or blowing away the chips as they are produced so there is no recutting of chips happening. This can lead to an uneven finish.

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