Member postings for Martin Connelly

Stefan, have a look at the Pokeys range from Polabs, I think that is a good starting point for the motion controller. The steppers and drives need to be compatible with the motion controller so should be chosen after that.

**LINK**

They will probably advise you regarding what motion controller is good for your needs and what drives and motors to use with their boards.

Martin

I have my tram set ever so slightly off zero left to right. What this does is allows the trailing edge of a fly cutter to burnish the surface when used in one direction. If used in the other direction I get the overlapping light marks described above by Russ. If this sounds like it should not happen you need to remember that the fly cutter tool may be deflected upwards when the leading edge is cutting but will have practically no deflection on the trailing edge.

The point is that getting tram to zero may not be worth the effort put into it if you are close enough for the results to be satisfactory. Your 0.04mm across 254mm is 0.0016mm across a 10mm end mill. and unless you are moving up and down 250mm in a single set up then your vertical features will be less than 0.04mm out top to bottom. Unless you are working in a totally controlled environment with a need for very tight tolerances I think what you have is fine.

Martin

Douglas, your 4.33mm is correct but you will not have a sharp vee at the bottom. It is usual to have a small radius or flat, after all the mating part is going to have flats. If you have a mating thread with a 1mm flat then you would expect the base of the thread to have a flat smaller than this or a radius to give a small clearance between the two parts. A radius of 0.58mm at the bottom of the vee would be one solution and a flat of 0.75mm would be another. these both have the effect of increasing the inside diameter.

If we have a radius of 0.58mm at the bottom of the vee then the flank height is no longer 4.33mm but becomes 3.46mm and the radius after this goes down a further 0.29mm so your 4.33mm is now 3.75mm.

If we have a flat of 0.75mm at the base of the vee then the flank height is now 3.68mm.

See the drawing below for the details.

Martin

These numbers on there own do not tell enough to pass an opinion. If they are over a diameter of 10mm then they are probably unacceptable. If they are over a diameter of 300mm they are acceptable. So the question is what diameter are they measured across.

Martin

Zapp Automation sell a lot of the parts you will need. Don't know if they are the cheapest, just that they sell these items.

Leadshine 3 phase Easy Servo steppers and drives have a good power to size ratio. They also have the option to give an error signal if there is a position error which is not a feature of standard open loop stepper systems. If it is important to have a system where missed steps are not acceptable then they should be considered.

Martin

8.5mm long?

Martin

Douglas, 4.6TPI is very close to 5.5mm pitch. If you did 5,5mm pitch x 42mm diameter in a metric 60° thread form the difference between outside diameter and bore would be 5.5mm. This would give a bore of 36.5mm for your initial hole. I know there will be a slight difference due to the flats you require but it seems a lot different from your calculations of 30 April. To get close to the 10mm difference you have from Ø35mm to Ø45mm you would need a pitch close to 10mm or 2.5 TPI.

I printed off the picture of the thread in your post of 02 May and scaled the dimensions from the 44mm stated on the label. This gives a bore of 37.3mm diameter and a pitch of 6.4mm (approximate of course). This is close to what you would get from a metric thread with Ø44 and pitch of 6.5mm (37.5 bore). This is a little under 4TPI.

Based on these figures I think you should keep the TPI value at 4 or lower.

Martin

You could mill the threads as stated earlier but with a CNC lathe you can just cut the thread with the required tpi and diameter. A drawing of what is required would help.

Martin

Tormach have investigated pull out values for collets. Their report is useful reading for anyone using collets.

**LINK**

The important point for this thread is suitable lubrication on the correct surfaces. I wonder how many of these run out checks are being carried out with suitably lubricated surfaces. It may make a difference to the TIR values. It would be a good subject to include if an article is written for MEW as suggested by Neil.

Martin

Chris, the idea behind the use of tenons is that you can fit a vice or rotary table to a slotted machine table and it will be aligned to the slots without having to be dialled in. The accuracy depends on the state of the slots in both the vice/rt and the machine and how well the tenons fit the slots.

Martin

The slots in the base are for fitting tenons. These are to locate it in a slot on a table.

**LINK**

I think you need to clamp it using long studs and tall packers to apply pressure on what is the top face when set up as shown in your picture.

Martin

Could you drill a clearance hole through the extension and use an extended drawbar to pull the tool and extension together into the lathe? An extended drawbar should be easy to make.

Martin

There is nothing to stop you from grooving as deep as you are comfortable with using your parting tool and finishing off with a hacksaw. Flip the part and face the sawn side to give the required thickness. Just leave an allowance for the final facing operation.

Martin

My lathe cross slide gib is dowelled as others have suggested. Smart and Brown original design. Dowels are about 2.5mm.

Martin

Any use of electricity in your house will result in a current in the neutral wire. It only needs a small resistance in this cable for a voltage to show up between the earth's zero and the neutral. V=IR applies. This small voltage is able to produce a current in excess of the RCD tripping current when the neutral is connected to earth (low resistance). This small current flowing through the earth cable means the current in the live is different from the current in the neutral so the RCD trips. Avoid cutting the earth and neutral at the same time and there should be no problem.

Since you often share a neutral with neighbours their use of electricity means that even switching off all items in your house may not stop this nuisance tripping. As suggested earlier switching off all power with the double pole switch that isolates the live and the neutral at the consumer unit is the safest thing to do anyway.

Martin

My 7-6mm ER32 collet has a larger diameter for the back half of its bore as do all the smaller ones in my set. This does not cause these collets to grip out of parallel. This implies that it would cause no problem to hold anything with just half the length of any ER32 collet's bore.

Martin

I was asked if I wanted to have a drive/ride, I declined the offer.

Martin

Windy, did you see the Warhorse monowheel at Elvington? I have made a lot of the parts for it.

Martin

If you have suitable pipe you could fill it with solder then bend it. Heat to remove the solder after bending.

Martin

If your fixed vice jaw is set up parallel to the X axis then you can mount the workpiece in the vice with a machined face against the fixed jaw and the face you want to be square to it overhanging the jaws to the left or right. You can then machine that overhanging face by moving the Y axis.

If you want to machine a part without a vice you can clamp it to the machine with some scrap underneath it. As you machine each edge you add and remove clamps to keep the part from moving while each successive edge is cleared for machining.

If you are using a vice and want to hold a non parallel workpiece use of round bars or ball bearings between the moving jaw and the workpiece can be useful.

Martin