Member postings for Graham Wharton

For info, that tool takes standard ISO 16ER threading inserts.

Looks like that set comes with partial form inserts. Once you get to the full depth, you will then need to run over the crests of the thread to give you the appropriate flats across the tops (to get rid off the O/D burrs that you will no doubt be left with). Its basically the same process as you would go through if you cut threads using a ground HSS tool. The advantage of this type of tip is that it will cover most 60 degrees thread pitches in a single tip. A60 will cut pitches 0.5-1.5mm or 16-48TPI and the G60 will cut pitches 1.75-3.0mm or 8-14TPI.

The alternative is to use full form inserts which will apply the appropriate crest form to the thread automatically once you reach full depth. The disanvantage is that you need a different insert per pitch that you want to cut. If you did want to cut full form, as they are standard ISO 16ER toolholders, you can just buy them individually from whoever, for the pitches you need, and use your generic A60/G60 tips for the less common threads.

I use Sandvik threading inserts, but just tend to stick to about 0.1mm infeed per pass. Sometimes I may go bigger, for the first passes and then light cuts for the final pass. But as a rule of thumb, my lathe and my tooling works well with 0.1mm passes, apart from the last couple of passes where I am sneaking up on the final dimension, in which case the last couple could be 0.02 per pass.

You can get this sort of information from the insert manufacturer.

Here for example is the Sandvik Threading catalogue from 2012. **LINK**

If you skip straight to Page 71 you can see their infeed recommendations for their threading inserts. OK, these are more suited to CNC threading where you can just programme in a number of passes at the correct depths to know you are operating them correctly, but this can still apply to the home user, if you happen to be using their inserts.

The first entry on Page 71 is cutting a 0.5mm pitch metric thread. They recommend 4 passes of 0.10, 0.09, 0.08 and 0.07 to give a total infeed of 0.34mm.

For most threads the final pass is about 0.07/0.08mm with previous passes of anywhere in the region of 0.1 to 0.3mm per pass depending on the thread pitch.

I would have thought other manufacturers inserts operate in a similar window.

Hope this helps.

Business cards work quite well, often come in a nice little plastic box, and are already a good size for most jobs. can be cut easily into smaller strips as required.

I have a box sitting above my lathe from my previous job.

Graham

I bought all my Mitutoyos second hand on ebay. All chosen carefully, not accepting any that show signs of any rust. Most are as new, tending to cost in the region of 15-25 GBP each. Ive got a full set of standards and never have any problems with repeatability against the standards.

You could say my mic collection has become somewhat obsessive.

I don't have any digital micrometers, but all of my absolute digital calipers sit on my bench pretty much 24/7 with the displays on, as they don't seem to auto off, and i've not replaced any of the batteries in the last couple of years. I don't know if the mics are worse for some reason.

One thing to remember is that some modern oils with Sulphur based EP additives, like some modern gear oils will actually attack and corrode yellow metals, such as copper, brass and bronze. If you're putting them into your geared head, QC Gearbox or slapping them on your leadscrews, the yellow metal bushings and feed nuts might not like it at all.

Graham

Brian, Are you suggesting that inverting the polarity of one of the windings would have no effect on delta configured motors and is only relevant for star configurations.

My recently gained understanding that by reversing a winding, you are effectively reversing the polarity of the inductor, which would result in an unbalanced delta. This surely would have a bad effect on both wiring types?

Graham

Having read up a bit on the theory, it would appear that having a winding inverted absolutely matters resulting in the magnetic field produced by that winding being 180 degrees out from where it should be. In simplified terms, instead of having fields at 0, 120 and 240, you get fields at 0, 60 and 120.

Swapping L1 and L2 on the supply lines inverts the rotation direction, but swapping U1 and U2 on the terminal block breaks the motor regardless of L1,L2 and L3 configuration.

Graham

Hi John,

I dont fully know the theory behind it, as I would assume that the magnetic field generated by an AC driven coil would produce the same magnetic field regardless of which way round the coil is wired, however it certainly has an effect on my motor.

With one of the phases wired back to front on my motor, it span at about 50 rpm, making some strange noises and was drawing full load current all of the time.

I ran the above test which showed one of my windings was inverted, swapped one of the windings round and now the motor runs fine.

I just assumed that it was the way that the coils were wired in relation to each other that was causing the effect, essentially having two windings fighting against each other.

I do see what you mean though, swapping terminals U1 with U2, in delta mode, stil results in a delta.

In my case the three points on delta were U1W1 V1U2 W2V2 instead of the usual U1W2 V1U2 W1V2.

Anyone explain the theory?

Graham

Hi all,

Ive just converted a three phase motor from 440V single voltage to 220/440 dual voltage. The original motor, being single voltage, was only 3 wire, therefore I had to dig out the star point and split into three additional leads. I fitted a new 6 post standard terminal block to aid switching in the future.

Well, during this process I managed to rather carelessly find myself with a motor with 6 black wires coming out of it with no labelling whatsoever.

I learn't something new today sorting it out, so I thought I would share the knowledge.

The first step to resolve is to work out which wire belongs to which of the 3 coils. To do this, use a multimeter to measure the resistance between the wires. Start with wire 1 and measure resistance to each other wire in turn until you find a wire with non infinite resistance. It will probably be sub 100 ohms depending on the type of motor. Mark the first "U1" and the second "U2"

Repeat with the 4 remaining wires until you find another pair. Tag these with "V1" and "V2".

Check the final pair and label these as "W1" and "W2"

The second step is to verify the polarity of the windings is correct. To do this, get a 12V DC power supply, or car battery and an analogue DC Volt meter (10VDC scale). The analogue meter is important as you are looking for small deflections in voltage, which you cant normally see on a digital multimeter.

• Connect Multimeter - to V2
• Connect Multimeter + to V1
• Connect Battery - to U1

Briefly touch Battery + to U2. If the voltage reading on the meter deflects +ve then V1 and V2 are correct. If the meter deflects -ve then swap the labels on V1 and V2.

• Connect Multimeter - to W2
• Connect Multimeter + to W1

Again briefly touch Battery + to U2. If the voltage reading on the meter deflects +ve then W1 and W2 are correct. If the meter deflects -ve then swap the labels on W1 and W2.

The next step is to verify the rotation. For this I configured the motor for delta operation, bridging U1-W2, V1-U2 and W1-V2, and then connected L1 of the inverter to U1, L2 to U1, and L3 to W1 and set the inverter to clockwise rotation. If the motor rotates anti clockwise, then swap the labels between U1 and V1, and then swap the labels between U2 and V2. (This last step is optional as you can easily swap rotation of a motor when hooking it up to the power source)

That should pretty much be it.

Hope this is of use to someone.

Graham

Thomas, please get a qualified sparky in to give you a quote. Pay lots of attention and ask him the right questions when he gives you the quote. Even if you're not going to get him to do the job, you should ask him questions and listen to his advice when he quotes you on what you will need.

Plenty of people have been quick to give you advice , but none of the them have been armed with enough information to design the installation you are planning.

You've beed advised to use a range of cable sizes, but nobody knows how long the cable run is.

You've been told to install an earth rod for your workshop and connect that to the house earth without checking what sort of earthing arrangement your house is on. On certain installation types what you have been advised to do may be prohibited by some power supply companies with good reason.

You've been told to install a 1.5mm2 ring main on a 16A breaker but this is not compliant with current wiring regulations and won't get signed off.

Nobody has asked how far away from the house the workshop is.

Nobody has asked if you have a water supply to your workshop fed from the house in conductive pipes buried in the ground or has said anything about earth bonding, or the equipotential zone.

Nobody has said anything about your earth loop impedence of your house supply or how that earth is supplied (TT, TNCS PME etc).

Then theres making sure youre going to meet the disconnection times for your RCDs......

There are plenty of other things you need to consider too, expecially if you are planning on getting a sparky to come and sign it off as compliant with the regulations at the end of it.

No offence intended to the well meaning people on this forum, but if you're intending on getting a sparky in to do the work, then the best person to make the sorts of decisions and answer the questions you are asking on here, and actually design the installation, is yourself and the sparky who will be signing it off.

Graham

Clarkson part numbers for chucks. Hope they are of use. There's probably some gaps which you may be able to work out. e.g I reckon my 3MT Large Chuck is actually part number 80103 etc.

Edited By Graham Wharton on 08/04/2015 21:43:29

Clarkson part numbers for Collets and Chuck Spares. Hope they are of use.

Steve,

I think at some point Clarkson must have changed the name of the large chucks with a taper gauge of less than 1/2" to medium to remove confusion about collet sizes. The 1" collet for the large chuck with taper gauge of less than 1/2" is a completely different size collet to the 1" collet for the large chuck with taper gauge of more than 1/2".

This applies to all of the 803XX series from the table above. The body diameter is smaller than the other large chucks, and the collet O/D is smaller than the other large chucks.

The full range of collets for the three chuck sizes are

Small 6mm, 8mm, 10mm, 12mm, 16mm, 1/4", 3/8", 1/2", 5/8"

Medium 20mm, 25mm, 3/4", 1"

Large 20mm, 25mm, 32mm, 3/4", 1", 1-1/4"

Looking at the clarkson part numbers, the 8mm Small, 20mm Large, 3/4" Large and all medium collets all appear out of sequence with the other original collet part numbers, so these may have been introduced after the above clarkson images were produced. I'm guessing the extra collets were introduced at the same time as the range was changed to small, medium and large.

Cheers

Graham

For more info,

Small Collet O/D = 7/8"

Medium Collet O/D = 1-3/8"

Large Collet O/D = 1.683"

Graham

I'd say that's a Medium S Type chuck on an MT3 Taper. It looks identical to the one I sold a couple of years back due to not being able to find any collets other than a 1" one that I had. In the approx 1 year that I was monitoring ebay for collets, I dont think I ever saw anything other than 1" (at a price I was willing to pay)

Clarkson part numbers for the medium chuck range are

• 40094 - 1" Collet
• 40095 - Spanner Medium
• 40096 - Medium Damping Ring
• 40097 - 25mm Collet
• 40098 - 3/4" Collet
• 40099 - 20mm Collet

Hope this helps. Good luck in the hunt for collets.

Graham

Thanks all. thats cleared it up. My original thoughts of hiring 6 thin people and getting them all on station at the same time seems like such a silly thought now!

Graham

Always wondered what in-line drills are used for.

In this example, would you have 6 pieces setup on the table and drill all 6 at once, or would you have a number of operators working on their own pieces, or 6 different drill bits and move your piece along the table as you go?

Thanks

Graham

Ive just looked at some pictures of the newer version of the Fobco Star Spindle, and I'm now thinking that the bearing arrangement on the later models is significantly different. Perhaps a pair of back to back angular contacts at the bottom of the quill and nothing at the top????? There doesnt appear to be any bearing surface at the top of the wider section. Has anyone split down a later model of the quill.

Thanks

Graham

Edited By Graham Wharton on 04/03/2015 10:49:00

I should clarify that last statement. Without preload applied, I was seeing vibration in the spindle when running with no load applied. As soon as the drill bit touched down, the angular contact seats and the vibration goes away. As soon as the load is taken off, the spindle vibration returns.

If you only have an angular contact at the bottom and standard bearing at the top, I would expect to be able to grab the end of the spindle and pull forward and backward and get some play.

This is tony's advice from lathes.co.uk

"As a point of interest the top bearing in the shaft assembly is an ordinary ball race, but the lower pair are a pair of angular-contact type. When the assembly is rebuilt some end loading is required on the bearings - and this can be done with a length of tubing, the setting being locked by a grub screw through the top collar (ensure that it bits into a new part of the shaft, not the original dimple). At first the bearings will be slightly tight and to correct this it's necessary to seat them properly by giving the end of the shaft a single smart tap with a 2 lb lump of brass. After this the shaft should spin freely and sweetly"

When he refers to the top bearing in the shaft, he is refering to the pulley bearing being a plain bearing, not the top bearing in the quill/spindle. He correctly refers to these as a pair of angular contacts.

Hope this helps

Graham

I just happened to replace the spindle bearings on my fobco star today.

The quill/spindle contains a pair of angular contact bearings. I replaced mine with a pair of SKF 7202BEP (Replacing the old R&M LJT15's). The bottom bearing is fitted so the angular contact is made when pressing up on the base of the inner bearing race from the bottom, and the top one is placed in the opposite direction, so the angular contact is made when pressing down on the inner race from above. It does matter which way up the bearings go. The top bearing was a looser fit in the quill than the bottom one, which needed pressing.

When assembled, you need to use a piece of tube to put over the spindle and press down on the collar that sits ontop of the upper bearing. Then you need to press down to exert some preload on the bearings while tightening the grub screw on the collar. This keeps the arrangement in place. Angular contact bearings don't work unless they have pressure applied to them.

I initially did this using hand pressure, but got too much movement on the spindle after fitting and had to repeat in the press, just putting extremely light pressure whilst doing up the grub screw. It really was the lightest of pressures in the pres though. That worked a treat.

There is another bearing at the top/front which secures the pulley to the main casting, but I have no details on this bearing. I wonder if something was getting lost in translation between you and Tony as there should be two angular contact bearings in the spindle (one at bottom and one at top) and a standard ball bearing for the pulley.

Note, there are several spindle types, so I am not sure if the different types use the same bearing arrangement. Ive heard of some people saying there is an angular contact at the bottom of the quill and a standard bearing at the top, but I cant see how that would be very successful.

Even without any preload though, as soon as you push down on the quill on a drill bit, the bottom angular contact should seat properly, but I was seeing significant vibration at 4000rpm without proper preload applied so I dont know whether this type of arrangement would work very well.

Hope this helps.

Graham