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Member postings for not done it yet

Here is a list of all the postings not done it yet has made in our forums. Click on a thread name to jump to the thread.

Thread: Rc 45-50
10/08/2016 08:31:01

I note you gave much more inf

o on another forum. I would not recommend reducing tool dimensions without very good reason. Later overloading of the machine or tool is one risk, often forgotten after the initial change. Prolly not applicable to this machine-tool combination, but people do change machines....

With regard to hardness, the Rockwell scale is one of several and relates to the ability of the surface to resist abrasion, surface denting, etc. Generally, the harder the material, the less resilient the object is to bending - really hard offerings of the same material will be brittle at high hardness - tools/items can easily shatter if struck too

hard. There needs to be a balance between hardness and flexibility for most items, dependent on application. Shanks are often hardened to avoid damage from chucking.

Go with carbide for easy turning, but surface finish is important and may be a problem. XD351 is likely spot on the money. Using tools too big for the machine is attractive, but not necessarily a good move. Reme

mber, by reducing the diameter by 33% means removing more than half the metal in the shank....

Thread: Rotary Table Failure
10/08/2016 07:03:17

Climb milling or conventional? I might just understand the failure, if the former.

Doesn't look like a very wide contact area for those wheel teeth (only a small diameter worm?). It strikes me that perhaps the worm is fully hardened and rough, while the wheel is in a softened state?

Not a lot of point for a rotary table if it must always be locked down - might just as well use a simple dividing plate?

Thread: Quick change tool post
09/08/2016 10:09:19

Cliff,

There are options to continual shimming.

Make a shim (or pack) for each tool.

Get, or make, more tool posts and retain tools fitted, ready for use.

Not sure about fitting any particular QCTP to that lathe, but no need for drilling, I suspect (a waisted central bolt would be adequate?). Often changes need to be made to fit them, but usually this can be achieved without modifying the lathe top slide (Ie change the tool post fitting to suit).

Thread: RPM counter for Myford Super 7
09/08/2016 09:51:02

An even cheaper method is to make a table or graph of Hz versus speed (just like a screw cutting chart?). You will soon find that belt pulley changes are rare and you will easily remember the usual speeds at different Hertz. Anyway, do we need to know the real actual exact precise spindle speed to the odd rev per minute or so?

I fitted a simple hall effect counter on my LJ, but rarely take any notice of it. Cutting depth and traverse rate, along with surface finish and how the lathe 'sounds' is far more important than setting it to an exact rotational speed.

Thread: Lathe not turning parallel problerm
07/08/2016 06:43:08

Do start by turning a rigid bar only held in the chuck. No amount of off-setting the tailstock will make any difference if the tool position is changing as it traverses the ways. Perhaps tell us what this bed length is and how the lathe is supported? Flimsy timber is a no-no, timber is not that good, but a sturdy steel stand on a solid base is good.

Don't assume anything. All that is likely to do is lead you up a dead end!

Thread: Rotary table problem
05/08/2016 20:00:21

Are the locking 'devices' free or tight?

Thread: Acme thread
03/08/2016 09:13:02

for a new cross slide that im getting made

It would seem to be a sensible suggestion that the maker of your cross slide supplies the screw?

Thread: Power Feed to Milling Machine Table
03/08/2016 09:01:34

nothing too complicated to set up .

The complication is simply that of disconnection so that the manual feed wheel can be used. Most are satisfactory at slow feeds, but fast traversing is not always fast enough.

Most could easily be converted if the manual wheel was removed and replaced with a power drive. But shifting the table by a tiny amount might be problematic.... Clearly, tables with wheels at both ends are easier conversions and retention of manual adjustment is necessary.

Thread: feed speed
03/08/2016 08:41:59

Just wish I did not have to learn via my wallet

Sam,

A fact of life, on occasions, I'm afraid. Nobody but the user knows what their machine is capable of. Large rigid machines will always cope with higher feed rates than a flimsy chinese hobbyist import which may not even be adjusted optim

ally.

25mm per minute would likely be OK, but selection of cutter type is covered, no doubt, in many tomes.

There are well documented surface cutting speeds for machines, but many machines are unable to achieve the advised cutting speeds. Yours did have a higher speed, which you apparently forgot about. Cutting speeds assume the optimum for everything else on the machine.

Different materials have variable cutting characteristics. Aluminium is well documented as requiring much faster surface cutting speed (than steel) and possible difficulties. One is the recommendation for use of some cutting fluid - like WD40 as a popular choice.

Melting point of the mateial being cut is yet another factor. Cutting dry requires steadier progress than lubed cooling. Aluminium, while having a good heat conduction rate will still have a higher temperature at the cutting/shearig point. one possible reason for it 'weldig' to the cutter tip.

I have often made mistakes, sometimes to the detriment of the cutter, sometimes of the manufactured item. It costs time, if not money.

I keep bees and find it soo easy, but many (mainly those with insufficient learning and non thinking) struggle and call it a 'dark art'. But machining metal is far more challenging than wood, per eg.

Think yourself lucky that it only cost you a 3mm cutter. It could have been far more costly!

I went to the show at Donny, this year. The one thing that struck me was the load of cheap unbranded cutters available at supposedly bargain rates. I know that buying cheap often means buying twice, so ignored these so-called 'bargains'. From my woodworking experience, I know that the right tool made of the best material and sharpened properly will work so much better, and longer, than lower quality tooling.

Many will claim high cuttig speeds, deep cuts and/or high metal removal rates. Most of us are much more conservative because our kit is less sophisticated, not so perfectly set up or we are not so highly experienced in selection and operation of tooling and kit. I have long used carbide router cutters for timber, but recognise that not all carbide cutters are equivalent. I bought this my first solid carbide milling cutter at Doncaster and I will use it very carefully, given the cost differential to other similar cutters in other materials.

Experience does cost. Learn from it and move on. On your last posting, consider what might have happened if your 3mm cutter had, say, twenty cutting edges instead...... would it have been better, faster, etc? I think not.

Thread: Acme thread
02/08/2016 22:29:45

Tell us more. Length, length of thread, material, why ACME, etc?

Dies are available for purchase (recommend them for finishing a roughed/part formed turned thread). Square threads are often substituted for ACME threads. Do you need a new nut?

HPC Gears can supply a range of items at reasonable(?) prices.

Thread: Power Feed to Milling Machine Table
02/08/2016 22:06:05

Table feed rates, according to lathesdotco, for the Centec 2B were 4'' per minute tops.

0.65, 1.19, 2.18 and 4 inches per minute are the figures quoted. Of course, with a VFD fitted, I can choose whatever speed I fancy....

Thread: Postage zones in the UK.
01/08/2016 19:40:52

You've won. Quite likely someone, somewhere, sometime watches these fora. Likely to end in a call for 'name and shame' if it went to any other conclusion. Unfortunately (or perhaps fortunately for you) it was likely an advertiser on these very same pages, and were tipped off to watch out for possible impending

trouble. Not an outside bet that it might be someone who might not want to 'rock the boat' or have the boat rocked? It is something I have noted on at least a couple of occasions, since joining the forum.

01/08/2016 12:00:59

I suggest you read their terms and conditions carefully. That is your (and their) contract. It should not be ambiguous and if it is, then as the purchaser, your clearly correct interpretation would stand up in court.

Thread: Jammed insert.
28/07/2016 06:45:37

I go with those that say that bottom screw is a screw with an 'off-centred peg' on the end. It will turn one way or the other to 'uncam' the insert from its secure tight-fitting position. Technically, I would guess, it does not need to actually be tight, once the securing clamp is fully tightened and, although it would normally remain tight, if it came loose, it could not unscrew unless the insert moved.

I would guess that it will release the insert by turning it inwards - clockwise - as it would normally be initially positioned almost fully screwed home, thus tightening the insert by turning outwards, in an anticlockwise direction. Well, I have a 50%chance of being correct!

Thread: Myford 254 metric screw cutting
28/07/2016 06:29:58

I think he means 'whatever number you chose', not necessarily number 1. Disengaging the half nuts while traversing forwards, before stopping the lathe and shifting the cross slide back, prevents running into an uncut area and breaking the tool. On reversal of the lathe, to return for a subsequent pass, the half nuts are engaged at that same number on the dial indicator (as lathe is now running in the reverse direction. Hence while disengaging half nuts they are always re-engaged at that same point every time. The important thing is the same number and always on the same turn of the dial indicator, as the thread would not necessarily be picked up on that same number without driving the lathe backwards

Thread: is this motor suitable for a milling machine
26/07/2016 11:48:32

 

Anything that is safe and works would be fine. Start with connector strips and build from there if there is nothing available commercially.

 

 

 

Only twelve wire connections and three or five link connections, so not too difficult. Better screw clamp connections would be better than the usual cheap strips with screws into the conductors. Fitting good connection terminals to each wire is also safer.

 

The question of suitability for any particular milling machine? Yes. But not to all.

 

MG,  looks like a US product.  Might be OK, if you are that side of the pond, but a bit hefty to import to the UK, I would think.

Edited By not done it yet on 26/07/2016 12:02:24

Thread: tapping drill
25/07/2016 06:53:52

A lot of muscles required, I reckon, if starting to tap after drilling a 32mm hole, unless! in possession of a complete set of taps.

This link gives the size for Whitworth theads. Wrong thread angle, but gives a good idea of amount of material to be removed.

http://www.engineersedge.com/hardware/whitworth-screw-threads-chart.htm

Thread: Lubrication quetion for Harrison L5A
25/07/2016 06:30:06

Too thin oil may contribute, depending on the seal type. Other factors may be you overfilling, there may be too much bearing play, the seal may be damaged 

(or worn), or the seal bearing point on the spindle may be damaged (or worn).

 

 

There must be provision for draining the headstock and usually some form of level device. Doubtless the drain will be at the lowest level of the box and the upper level device may be a dip stick or level plug. Both should be fairly easy to find by observation.

 

 

Do tell us the seal type.  Is it a lip seal, felt seal, or other?  Lip seals require a good sealing contact point, but can be displaced slightly to use a different sealing point on the shaft.  Felt seals usually have a thrower to prevent direct and continual immersion of the seal in oil.  Some seals do not have any seal, per se, but actually 'screw' the thrown oil back towards the gearbox.  

     

 

The last, but not least, reason for leakage may be a blocked breather, causing a pressure difference between the interior and exterior of the headstock.

 

 

 

 

 

 

 

 

 

 

 

Edited By not done it yet on 25/07/2016 06:41:23

Thread: VFD questions
24/07/2016 20:01:44

BPlease loopraking using the VFD is a good attribute but do make sure it is appropriate for your application.

If it is required for 'fast breaking', the resistor power may be important, too. Beware something may 'brake' if you 'break' too quickly. Or is that the other way round?wink 2

Thread: tapping drill
24/07/2016 16:53:48

About twice the thread depth less than the fixing bolts. What bolts/cap screws are you using? 1.5'' is 38mm.

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