I will try drilling some holes and then using a boring head. I may have time tomorrow, otherwise I will give it a go next weekend. Thanks for all the advice. Hopefully it will save me from spending more money and possibly still not succeeding.

I will should be able to access a lathe in a few weeks. So if I get totally stuck I will give that a try. I live on the London/Essex borders

I will give a 24 mm rotabroach a try. I have a R8 mini mill. What adapter would I need so that the Rotaborach would fit it? The one I have found on Amzon says that it needs a pilot pin, SRA50 ejector pin. What is this used for?

I have a boring head and will use this if necessary. But I lack the patience to use a boring head on 3 holes because of the time it takes, unless there is no alternative. Plus, I have had problems making the holes too big with a boring head.

I am trying to cut a round 25 mm diameter hole in some 25 mm thick aluminium disks. I am using a Sieg mini mill. Using an ordinary holesaw is not working. Probably because I have already cut smaller diameter holes in the discs so the holesaw drill has nothing to drill through to guide the holesaw.

I bought a Armeg carbide tipped holesaw, which was not cheap. This successfully cut through one aluminium disc but no longer works to cut through the other 3 discs I have. I am using plenty of cutting fluid.

Would a diamond hole saw work any better? I have a boring bar, but do not want to use this as I know from previous experience this will take a very long time if I use it. As on the mini mill I can only take very smal cuts each time.

Perhaps my mini mill is simply not powerfull enough? I should soon have access to a large lathe, but I will still need to know what to use to cut the holes.

I have tried reseting it and it still does not work.

I will probably buy from Inverter Drive Supermarket as they have next day delivery. I need to know what day it will arrive. I was considering buying an inverter and motor package from Newton Tesla, to save on wiring, but as far as I can see there is no certainty on which day it will be delivered.

It is for a mirror making machine and I will probably add an over arm at some point, for which I would need another motor and vfd.

I will get a Weg inverter. Do I need one that is filtered, or is unfiltered OK? Weg CFW G2 0.75kW 230v costs £89.87 and is unfiltered. There is the Weg CFW500 G2 which is filtered and costs £213.73

I aasume both of these would be OK for my TEC 0.75kW 3 phase motor? Do I need a pendant? If so could someone please recommend one for the above drives which is easy to connect? I have been using my current inverter with just the buttons on the inverter, but maybe this is not a good idea?

David

I have checked all the wires and have disconnected them and reconnected them, but it still does not work. The manual says that you can reset by going to P77 and entering 12345, but I cannot understand how to enter 12345.

Can anyone recommend a replacement, preferably with good and simple instructions? Also, that are available quickly, Inverter Drive Supermarket shows delivery times of many weeks for some VFDs that have been recommended on this site For example the Eaton DE1 0.76kw VFD shows 8 weeks delivery time.

David

I have a xsy-at1 inverter which I have been using for a few years without a problem. I needed to move the motor and inverter. I am now getting error code 1 and the inverter does not work. Are there any suggestions as to what I can do? I have checked the wiring and there are no loose connections.

Should I just buy a better quality inverter? Can anyone recomment an appropriate one for a TEC 0.75kw 4 pole motor, model model MS2 802-4.

David

I have a 60 mm round acetal rod that I need to machine accurately to a rectanglular shape to fit inside some alumium rectangular tube one inch x one and a half inch (25.4 mm x 38.1 mm) wall thickness 1/8 th inch (3.1 mm.)

I have a mini mill without Dro and a portable (Aldi) band saw.

What us the best way to machine this? How to set it up so I can machine it accurately?

Of course I meant the diameter of the mirror is 508 mm (20 inches)!

Thanks for the information, Ebay is quite a bit cheaper. I will have a look at delrin. I am planning on adding a fan to the cell.

How easy is it to machine what I need out of round bar? I have a mini milling machine. I assumed milling a sheet would be a lot easier but maybe I am wrong? I also have an Aldi portable band saw. I only use the milling machine occasionally, but it comes in very useful sometimes.

Regards

David

I am making a mirror cell to support a telescope mirror. The cell is a triangular frame made with 1 inch x 1.5 inch rectangular aluminium tube with 1/8 inch wall thickness. In mm this is 25.4 mm x 38.1 mm, wall thickness 3.175 mm.

Inside the tubes there will be 3 spherical bearings, 10 mm ID, 20 mm OD and width of 15 mm

I am following a design from an American astronomy website. In this the spherical bearings are place in housings made of Nylon which fit in to the aluminium tube.

I worked out that I need to cut Nylon bar in 3 pieces to around 34.93 mm x 22.23 mm and length of maybe 50 mm each. So I probably need a length of nylon bar of around 200 mm to allow for mistakes cutting the bar.

Direct Plastics sell Nylon 6 sheet 40 mm thick x 250 mm x 250 mm for £57.64. I wouldn't mind getting this quantity which is more than I need in case it might come in handy in future. But I don't want to pay this much.

Does anybody know where I can get Nylon cheaper or is there a cheaper material I can use? Nylon seems to working fine for the telescope cell in the U.S.A. so a similar material would be good.

The bearings will have some quite heavy duty springs keeping them under pressure, and supporting the telescope mirror, they are for collimationg the telescope mirror, which is quite heavy.

I don't know how much it weighs but it is 508 mm in circumference and 40 mm thick glass so it is quite heavy. I can carry it but it is rather hard work!

David

Thanks for all the advice.

I am in London/Essex. I have ordered some cable from TLC-1.5mm² 4 Core SY Protected Cable Flex. They have a branch not far from me so I will collect if from the branch

David

I am thinking of getting a VFD and a 3 phase motor, it will be a 1 hp motor. I have bought 3 of the Workshop Practice series about motors and VFDs and am reading through them

There is also a Youtube video of someone setting up a VFD and 3 phase motor for a Myford ML7 lathe which is quite informative. For the motor to VFD connection the man in the video states that he used the cable from a 16 amp 3 phase extension lead, as this was cheaper than buying lengths of wire.

As far as I can make out from my reading the power going from the VFD to the motor will be 240 volt 3 phase. Can I buy a 16 amp 3 phase extension lead from Machine Mart and use the cable from this, even though it is 400 volt?

Does the cable need to be shielded? Should it be 4 core 2.5 mm? The length of the cable will be 1-2 metres at most.

If possible could someone give links to where I can buy appropriate wire. Screwfix has some armoured wire but it is hard to tell if it is shielded and it is 25 meters long and over £60!

For the cable from the mains to the VFD I am planning to use a 13 amp plug and the same heavy duty cable I used for my existing first phase 1/2 hp motor-or should this cable be shielded as well?

The motor I am going to get is-TEC IE2 0.75kW Aluminium Three Phase Motor 230V/400V 4 Pole 80 Frame B5

David

My existing motor is single phase 1/2 hp. I am only thinking about getting a 3 phase 1 hp motor.

My existing gearbox is for a 71 frame motor, the 3 phase motor I am planning to get is an 80 frame motor, and the shaft on the motor is 19 mm rather than 14 mm on the existing motor, so it won't fit.

What I was wondering about was, if I got a 30:1 gearbox for the new motor this should make everything fine for very slow rpm for the turntable of between 1-5. But would the VFD and the motor be able to increase the rpm of the turntable to 40 rpm with this amount of reduction?

Perhaps I would be better with say 15:1 reduction? I have 3 shafts with pulleys on to reduce the rpm, so I could change the machine if necessary to only use two of the shafts, which would increase the speed.

At the moment I will not need that much torque when the turntable is running at low speed. This is because at that stage I will be pushing the polishing lap across the mirror by hand.

The torque is needed when the lap rotates on the machine in a fixed place. However, eventually I would like to add a powered overarm so that the machine would push the polishing lap back and forth across the mirror. I could possibly use my existing motor and gearbox for this, it is better not to run the overarm off the same pulley system as the turntable but rather to have a second motor.

David

Actually I already have a 30:1 reduction gearbox for my existing motor, the input is for the 14 mm shaft which is on my existing motor. I have not fitted it yet because I am not at the stage when I need really low rpm on the turntable-this is only needed in the last stage of working on the mirror, which I am almost at.

If I get a 1 hp 3 phase motor with a 19 mm shaft is it possible to buy (or make) an adapter to reduce it to 14mm so it will fit in the gearbox?

I have discovered that the v belt from the motor pulley was a bit slack and this was causing a lot of the noise, it is a step pulley so I have now put the belt on bit a bigger pulley and it is tighter and the machine is still noisy but not as bad. The speed of the turntable has now increased to around 38 rpm which is fine as it means the mirror gets polished faster.

I think I will think about this and possibly buy a VFD and 3 phase motor later in the year. I was going to buy from Newton Tesla, the AV750 I hp package. But when I rang them they told me that it could take up to a week to be delivered. I am on holiday next week on Monday and Tuesday so wanted to get it by then.

There are books in the workshop practice series about electronics and VFD so I will probably buy these and have a read.

Has anyone bought one of the inverter and motor packages from ACDC Drives?

I am interested in the Motor Control Kit-AC10 Inverter 0.75KW 230VAC input

This has an inverter and 1hp 3 phase motor.

It is for the powered turntable on my (telescope) mirror making machine. It is currently powered by a 1 phase motor from Machine Mart which has worked fine but is very noisy and I would like to have variable speed. Also, occasionally the torque seems to be lacking and I have to help the turntable along by hand.

I have belts and pulleys which reduce the 1500 rpm of the motor to around 28 rpm for the turntable. I want to be able to change the speed between 1-2 rpm to around 40..

The Motor Control Kit is described as 'plug and play' which is good as I don't know much abut electronics. I managed to wire up the DOL starter and existing motor but it took a week or two of reading

David

Thanks for all the advice. I have solved the problem by cutting in to the side of the table with a jigsaw and moving the shaft a few mm, this has now made the tension in the belt enough so it does not slip. The pillow block bearing at the bottom of the shaft is attached to a board with two nuts and bolts. I slowly tighten the nuts on the bolts, this moves the shaft and tightens up the belt.

Polishing now works fine,

It is a 20 inch f/4.1 mirror. I am testing it with Ronchi gratings and a bath interferometer, which I am slowly learning how to use, also the Foucault test.

Does anyone know where I could buy an idler pulley with spring loading?

I have a mirror making machine, one of the belts is very slightly too long and is slipping. This only happened when I started polishing the mirror, there was no problem when grinding the mirror. Apparently there is a lot more torque when polishing.

Also, would I buy the same diameter idler pulley as the one I am replacing, and would it fit on the shaft the same? The diameter of the pulley I have at the moment is 8 cm.

I realise that I could buy a slightly shorter v belt, but I have been recommended to get an idler pulley as a belt can stretch with time. Also, getting belt that is exactly the right length is not that easy.

I also wonder if the fact that the belt is going from an 8 cm pulley to a 35 cm pulley could cause problems, is the difference in sizes to great.? I have a bit bigger pulley i could fit, but would need a new belt, as the one on the smaller pulley will not fit.

David

Hi, I have made a rotating turntable for making a telescope mirror. The turntable needs to rotate evenly with very little or no runout.

I was getting a lot of runout. I have figured out that this is due to the 8 inch pulley I have used to attach the shaft to a the wooden turntable I made, which is 20 inches in diameter. The pulley fits well on the shaft. However, the top of the pulley where I attach it to the turntable is unven, one side is higher than the other.

I am trying to make the pulley even by attaching a file to a vice, leveling it over the pulley and rotating the pulley on the shaft, using a motor at. around 25 rpm. This seems to be working, slowly. The pulley is metal, I am not sure what metal.

My question is, is this a good way to do it? Of course the file is going up and down with the motion of the pulley as it goes round.

I have a milling machine but no lathe.

David

I have some self lubricating pillow block bearings. I have got some dirt on them, sawdust, bits of metal. I have cleaned them as much as I can with a cloth.

In case some dirt has got in to the bearings is there any oil I can use to flush out the bearings?

Also, this is probably a silly question, but do I need to lubicrate the bearings as they are self-lubicrating?

I haven't used the bearings yet.

David

So I signed up again and it now works. Now I need to watch some videos to figure out how to use it!

David