Member postings for Neil Lickfold

The BSW thread form is stronger in weaker or notch sensitive materials due to it's radius on the root and crest. The metric and the UNC form, has sharp edges on the crest of the thread form.

Neil L

The uneven helix angle and spaced fluted milling cutters work really well on manual mills and the mini mills. They are way better than any HSS cutter as well. The face cutters with the positive geometry uneven spaced inserts also work really well on the mini mills. Got a good laugh from the man or mouse video. Using compressed air with a bit of oil works really well for milling , especially if you adopt the full flute depth of cut with a shallow radial cut techniques. All that you need is some way to stop the chip from being recut again, and the cutter life increases quite significantly. If you also have ball screws or some way to control the back lash, climb milling also increase the cutter tool life as well.

Having support material above and below the part. Negative or dulled off a drill bit like the video is good for plastics. Also withplastic , not too hi a rpm. Otherwise it will want to melt the material. Same for a lot of other plastics.

Neil

What a great idea, and really cheap as well.

Neil

I was told that the motors, 2 pole or 4 pole can safely go to 40% over their rated max rpm.

Neil

Maybe you need to get back to them, so that the person who helped you, finds out that they either messed up, or need more training. Possibly take it further up the chain. The local place here in Hamilton, they will set the drive to suite the motor and the application it is being used for. Really great service too. Companies are only as good as their staff.

Neil

After setting the motor to the lower voltage option, get the hand book that came with it, and check the current settings, for your motor. From the motor data plate. The drive will generally go from 20hz to 50hz, but is programmable to 400 hz. Don't go over 70hz on the max limit. Some say don't go over 60z,(USA and Canada power frequency). Like others have said, as the frequency drops,so does the RPM, and so does the total power available. Also there is breaking options, and slow down/ decelleration settings. I think mine is like 0.3seconds or something like that, and have the accelleration at the same rate, on the motor start up and shut down.

I am surprised that if you brought the unit as a complete set up ready to run, that they would have the motor not in the correct configuration. I am assuming that your VFD is the 220V 3phase output one, and Not the 415V output one.

I have a microswitch inline on the S1 control circuit. This micro switch I use is a normal closed one, and is opened/broken circuit when the contact is made. It stops the lathe for when I do forward thread cutting. And allows me to turn the switch to reverse to wind back for another threading pass. Really good for internal threads. I have some pictures in my Album with it.

Neil

So I have an album here, https://www.model-engineer.co.uk/albums/member_album.asp?a=48822

I have the microswitch on S1 one connection. So when the switch (normal closed) is opened, it stops only the forward direction of the motor. Reverse direction still works . I set the VFD to stop in about 0.3 seconds I think, maybe 0.1 seconds. When the switch opens, the motor stops, then I switch to reverse, wind back.and can take another cut. The microswitch is set on a movable stop to set it in the Z distance.

Will add more to the album when I thread cut next.

Neil

Edited By Neil Lickfold on 29/07/2018 12:47:03

The problem you have is that the thread needs to be concentric to the taper seat in the head insert. If you make your heads, bore the inner diameter for the thread form, and turn the taper seat angle as well. Then use a small threading tool to screw cut the thread form. When it is mostly thread cut, you can use a tap to act as a thread chaser. If the tap is run just straight down the drilled hole, often the tap does not start concentric to the hole. I also found, that if the taper seat angle is made a very small amount, tighter on the front, over the nominal angle. I make the Nelson taper seat 34.75 deg instead of 35 deg. With the Turbo plugs, I make the taper 60.5 deg included angle. With bearing blue, the plugs will seal on the very front of the taper seat. Some glow plugs the seat is not concentric to the thread form. Those plugs will always have sealing issues. You can also correct a head, by making a precision thread form and use that to get the head insert concentric to the thread. Then rebore the taper seat.

SInce setting up the myford S7 with a VFD and a micro switch to stop the spindle, it has made doing internal threading quite easy, with confidence to internal thread cut.

Full form carbide thread cutting inserts are just great. If turning the lathe by hand, like some do, it is essential, that at no point do you move it backwards while it is engaged in cutting the thread. I just have a small run out area and use now use a micro switch on the VFD to stop the spindle when the tool is in the relief area. I also cut the area to be threaded about 0.1mm bigger on diameter. Us a marker pen for colour. I keep cutting until the marker pen is gone, measure the OD of the threaded area, eg 10.05mm and then make another pass at 0.1mm so it makes the OD of the form 9.95mm for a M10X1.5 thread. Works perfect every time. On threads smaller than 6mm I use -0.03mm and on threads smaller than 3mm I make them -0.01mm, so M2 and M2.5 I make them -0.01mm , for M3 -0.02mm , M4-M6 -0.03mm, above M6 , make -0.05mm , all are on diameter references. I buy the full form ground inserts for home. They will cut as hard as 58Rc and will cut all materials I need to cut, The inserts I use for threading Titanium, I only use on Titanium and nothing else. Thread cutting at 90 to 300 rpm is just fine, on hobby lathes. Use a good cutting fluid suitable for the material you are cutting also makes a difference. I either cut slow and dry , or with a flood of fluid to wash away the chips and it gives a good thread form finish. There are charts for carbide inserts for the number of passes in thread cutting. It is like about 4 to 6 passes, depending on the thread depth and pitch etc.

I have found that the ccgt 09 and ccgt 06 inserts from kyocera on the myford are best. You want around 400 rpm for the hard skin and then around 600 for the rest. Get the small radius 0.2mm inserts and take no more than 0.2mm cuts (0.4mm diameter ) at about 0.05mm per rev,(2 thou per rev) feedrate. If it gets hot, use water or some coolant on it. I have a picture of the ccgt inserts that I turn bearing races with in my album.

In my experience , unless you can get a 0.2mm cbn and they are expensive, the regular coated carbide will be a far better choice on a Myford lathe.

Neil

The 1.5D or 2.D rule work well for similar strength materials. But a steel capscrew in an aluminium housing that is frequently being reassembled, the threads in the Al housing will last much longer with a 3d thread engaugement . On those we replace the worn threads with 2D helicoils and they are ok, the ones that had the 2d thread in the 1st place. Irony is to get the 2d helicoils in takes the same room as tapping for 3D threads. The 3D threaded ones have not failed after 4 years of service. The 2D threaded ones failed in less than a year. For some materials fine pitch series threads are stronger than the course pitch series.

Neil

Loose compound slides, and loose or improperly adjusted cross slides, all add to poor surface finish. I only use the low speed range of the motor to the clutch, so max is like 700 rpm or so. The ground inserts for Al etc work really well like a hss tool. I find that using very sharp tools is the key to a good surface finish, as well as slide etc in very good order.

Neil L

The kurt type or clones of the Kurt vice is the best way to go. The biggest advantage is the mechanism that pulls the sliding jaw down as it closes. The best part is not needing to tap down the part in the jaws. There is another American brand that have another system that is new, is is even better again, by the Chick work holding company. http://www.chickworkholding.com/

These are too new I think for their to be knock offs yet. My Kurt clone is mad in Taiwan, and I am very very happy with it. After seeing the Chick vises at the Emex show in Auckland, I am going to make my own version of their quick change Jaw mechanism. My 4 inch version has jaws that are 110 mm wide. This is the one I bought a few months ago. After using it for a only a short time, would not want anything else.

It is a time saver as well. You don't waste time tapping down the work piece etc etc. And the handle only needs a light load on it t clamp things very tight. The little mound around is good as it will catch any fluids etc as well.

Just my penny's worth. Neil L

Thanks Ian , Fenner is the link belts I have , and is the one installed on my motor to clutch pulley. I have another type I was given, that has metal pins to join the links, but have not used it yet either. One day I guess.

Neil

Back in 05 or 06 while living in America, brought some link belt for the Myford S7. Best thing I ever did. Apart from the initial stretch, but followed the instructions with the link belt( ie make it the shortest specified length 1st), it has been like magic. The vibration that I used to get completely dissapeared. I can have a dti on a workpiece with the motor running and you can see the needle position. Before it vibrated and you could not read the dti. This is from the motor to the clutch. I have not yet needed to replace the head stock belt yet, but do have the link belt for the day I need to replace that belt. The current headstock belt is a gates segmented quiet run belt. Has little grooves to let air out or something.

Neil

Google found this , http://www.lathes.co.uk/amolco/ Looks like the screw you are talking about is too short.

Neil L

Edited By Neil Wyatt on 08/07/2018 22:48:35

Another issue is the radius of the tool is too large and requires too much tool pressure. So it flexes everything as it cuts, apart from the issue that the head/ column is not trammed to the run of the spindle. On some machines, it is not the column that needs correcting, but the work head may need shimming to get the run of the spindle true to the table. So if the head runs up and down the column, and the bottle square or you master square shows that it is within 0.02mm over 150mm or so than that is going to be OK. Then you know the error is in the assembly that is holding the spindle. It could be it needs a shim under the Pivot ring on the lower side. Looking at the numbers, it will most likely need a piece of 2 thou shim in this area for a start. It may need a 4 thou shim.

Neil L

The real issue is the clay slurry getting into the bearing. Sealing it with some silicone tubing on either side might be the answer. Clay particles are very hard. So no bearing material will cope with that sort of abrasion.

Most of the laps were either used dry , or they used a cutting oil. Not seen any that used water. Often the double sides was for a roughing and a finishing diamond wheels,

Neil