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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: 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.

Thread: 316 Stainless
04/08/2019 08:31:10
Posted by Dave Harding 1 on 04/08/2019 00:12:42:

I don't have any flood cooling it just gets extremely hot and now I think its case hardened itself.

How confident are you that it is 316? Was the material from a reasonably-trusted source?

Stainless does not case harden. It does work harden, mainly due to allowing the tools to rub and not cut. Small depths of cut, high speeds and low feed rates are ideal conditions for rubbing. Do not dwell at the end of the cut.

You might need to be a bit more specific than simply 'carbide'. Are they name-brand inserts of standard geometry?

Please ignore totally the advice given by another poster viz: "If you are using tip changing tools, then of course you have to go at 6000 RPM with low depth of cut ( .05 mm)". If you really want to work harden your material, this is the ideal recipe.

Thread: Myford 7 Capacity Check
02/08/2019 20:05:45
Posted by Martin of Wick on 02/08/2019 17:03:45:

7 in. swing over bed 9 in. in the gap

Barely 1 1/4 in. (31mm) horizontal in gap between faceplate and bed on a 7

Just over 1 1/2 in. on S7

Would it be more relevant to measure between spindle nose and bed? Perhaps also between spindle nose and headstock casting.

You could make an offset (towards headstock) faceplate that accommodates the 2" width required.

In a push, buy a bed off one of the spares breakers and cut some off the ways.

Thread: Good inserts For (t6 i think) aluminium
02/08/2019 19:50:13

It would be beneficial to you to tell us what holder you have for the inserts (i.e. the insert shape).

Assuming you have a rhomboid one, I have had good luck with Korloy CCGT inserts. Available on eBay via China if you do not mind waiting, or Cutwel Tools.

In general, aluminium inserts will have a 'G' in the code (for ground/polished after sintering) and will be shiny silver in colour and very sharp.

Be sure not to get ones for aluminum, or you will have to source your material from USA.

Thread: Boring Head
30/07/2019 20:25:24

One thing to get your head around if, er, heading for a larger head is the head room the head requires.

The body and standard toolbit of larger boring devices can eat up a lot of your Z-axis space.

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!

JM

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:

http://www.elkmotor.com.tr/EN/two-speed-dahlender-winding-types.pdf

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'.

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