Member postings for Rowan Sylvester-Bradley

Thank you for all that hepful advice. It sounds like the "treppanning" process is not going to work, or is going to prove troublesome and difficult. Although I see that you can buy special "face grooving" tools for this (e.g. https://www.sandvik.coromant.com/en-gb/products/pages/face-grooving-tools.aspx). Does anyone have any epxerience using these?

So my process now (based closely on JasonB's suggestions) is:
1. Cut the stainles steel rectangle to a rough circle using a hacksaw. Whether this just means cutting off the 4 corners, or doing more cutting probably depends on whether I can reassemble and get working my power hacksaw.
2. Grip it in the 4-jaw chuck, and cut the outer 6mm to 76mm dia using an HSS tool.
3. Reverse it in the chuck (maybe change to the 3-jaw) and cut the other 6mm to 76mm dia.
4. Still holding it in the chuck, drill and bore the 25mm hole.
5. Hold by the hole in the three jaw chuck with the internal jaws and turn the outside circumference to 75mm dia.
5. Face both sides and the circumference.
6. Drill and tap the radial hole. I understand that I can't tap 25mm deep. I was thinking of just tapping it as deep as I could, and then "extending" the grub screw with a rod say 4mm dia ground to a conical point. This can just be loose inside the hole.
7. Finish with emery or similar. Make a 25mm arbour if necessary to protect my fingers

Other issues. If 304 is not the best grade to use, what is best? Yes, it does need to be stainless.
Yes, what I have is a piece of 12mm x 75mm bar. I know that facing it will end up with it less than 12mm thick. I was just going to take off enough to get a flat surface. The eventual thickness is not very critical.

Thank you - Rowan

I have to make a disc 75mm in diameter, 12mm thick, with a 25mm hole in the middle. The dimensions (apart from the 25mm hole) are not critical. It needs an M5 tapped radial hole to take a grub screw to locate it on the shaft that goes through the central hole. I have a piece of 304 75mm x 12mm x 80mm stainless bar to make this from. Here is the process that I'm thinking of:
1. Mount the rectangular piece of stainless in the 4-jaw chuck, if necessary with some pieces of shim under it so that there is some space underneath to cut into in the next step. Drill a central hole up to 12mm dia in stages (e.g. 4mm, 8mm, 12mm).
2. Increase the size of the hole to 25mm using a boring tool.
3. Take the part out of the 4-jaw chuck and mount it in the three jaw chuck with the internal jaws.
4. Cut into the part from the side at 75mm dia using a parting type tool with extra clearance on the outside edge to allow for the curvature of the groove being cut.
5. Either cut right through the part from one side, or reverse it in the chuck half way through and cut from the other side.
6. Face both sides and the outer circumference of the part.
7. Give it a satin effect by holding silicon carbide smoothing paper against it as it rotates. It has to look nice.
8. Drill the radial hole using the pillar drill.
9. Tap the hole M5.

Is this a good process? Please say if this process won't work for any reason, or could be improved in any way.
Can I buy the tools needed to do this? Where from? Presumably they should ideally be carbide? Or do I need to make them myself from HSS? If so, any hint on correctly grinding the tools?

Thank you - Rowan

Another beginner's question: when I centre-drill something, I almost always end up breaking off the small centre bit of the centre drill. Why is this happening? Am I using too small a size centre drill? Or have I not got the centre drill properly centred on the axis of the lathe? Or both? Or something else? If it's not centred properly, how do I get this centred correctly? The tailstock on my lathe has a lot of slack in it when the nut is loosened, but I always try to get it centred correctly before tightening the nut.

All hints welcome.

Thank you - Rowan

I'm a beginner at this, and need some help. I have just tried turning a 0.75mm pitch thread on a piece of brass bar. I gound the tool myself, using an angle of 60 degrees. I used a slow speed (backgear using pulley 2). At the end of the threaded section I just turned off the lathe, since I don't know a better way of doing this. Of course this is not precise, and I may have stopped the lathe a fraction too early or too late at the end of some cuts. After each cut I just started the lathe in reverse until the tool was back at the beginning of the cut. I could not disengage the half nuts because I was cutting a metric pitch on an imperial lathe. I did not back out the tool for the reverse pass because I thought this would make it difficult to advance the tool by a few thou from its previous position for the next pass. The problem is that the thread has come out very lopsided, with a much sharper angle on one side than the other, which I hope you can see from the picture.

Why has it done this? How do I correct my technique to get a properly shaped thread?

All advice and suggestions gratefully received.

Thank you - Rowan

Edited By Rowan Sylvester-Bradley on 03/09/2022 18:12:48

I'm looking for a low viscosity 100% clear 2-part epoxy in a double syringe, with not too fast setting time. I need it to repair cracks in some china items, so it needs to flow well into the crack before starting to set. Can you recommend a product that will do this?

Thank you - Rowan

Do you know where I can get one of these? I suspect that the cutting edge of the tool will still be too high though (there is only 8mm between the top of the top slide and the centre line of the lathe).

Thanks - Rowan

Thank you.

But that doesn't answer how I get the tool low enough so the cutting edge is accurately aligned with the cenre line of the lathe.

Thanks - Rowan

On my lathe (a Portass PD5) the surface of the compound slide that tools are clamped to is about 8mm below the centre height. This seems to mean that I can't use a tool thicker than 8mm (or more precisely, whose cutting edge is more than 8mm above its base). So how can I use a tool like this:

where the cutting edge is 25mm above the bottom of the holder? Can I attach some sort of tool holder directly to the cross slide (i.e. remove the compound slide altogether)? But then there will be no fine resolution way to move the tool parallel to the axis. What is the correct way to solve this problem?

Thank you - Rowan

On my Portass PD5 the centre is about 48.5mm above the top of the cross slide. How does this compare with a Myford?

I'm not sure I need a casting for the rear toolpost. Can't I just machine it from a piece of 50mm square mild steel?

Thanks - Rowan

How wide a parting tool should I start with?

Thanks - Rowan

Is this type of parting tool satisfactory?

LINK

There seems to be nothing much (except the taper) to keep the carbide tip in place, and nothing to stop the tip being driven deeper into the tapered recess.

Thanks - Rowan

Thanks for these answers. I just ordered a copy of GHT's book.

Rowan

Where do I find this GHT design?

What exactly were you referring to when you said that RDG had one on ebay?

Thank you - Rowan

Yes thank you, I already have a copy of this. It answers many questions, but not all.

Rowan

Another beginner's question. On my lathe, if I make a tool from 8mm square HSS and clamp it in the tool holder with no shims or anything, then the top of it is about at the right centre height. I bought some 18 x 2 mm HSS with the intention of making parting off tools from it, but there seems to be no way of setting these at the correct height unless I grind them away to be 8mm high (unless I remove the compound slide and find a way to mount the tool holder on the cross slide). What's the best way around this problem?

Thank you - Rowan

Thank you for that. Yes, the bearing clamp is single sided.

One related question: if I fit drip oilers to the headstock bearings, do I need to fit them also to the counter shaft? Or does this just not matter because wear in the counter shaft bearings is a lot less critical?

Thank you - Rowan

Thank you for all the helpful advice. Here's a picture of my setup:

I bought the brass hex bar from aluminium_online via ebay. They say it is grade CZ121. The speed I was using was about 300rpm.

I just tried tightening up the headstock bearings a bit (since I could see nowhere else that any play was getting in), and it seems quite a bit better. So maybe this is the root cause of the problem... If I need to replace the headstock bearing shells can I buy them, or do I need to make them? If I need to make them, what metal do I use? Do I need to do anything to the headstock shaft surfaces when I replace the bearing shells? Anything else I need to know to make good replacement bearings? Or should I be fitting roller bearings instead?

Thank you - Rowan

I'm a beginner at this. I'm trying to make a couple of parts from 19mm a/f brass hex rod. It involves turning down a section to 15mm diameter, cutting a thread, and parting off the part. I am getting some jitter which is spoiling the part. I'm using a tool with no top rake, at the second fastest speed my lathe can do. I have tightened up all the slides, and can't feel any slack anywhere. I have tried no lubricant, and soluble oil.

What am I doing wrong? How do I get it to cut cleanly and leave a good finish?

Thank you - Rowan

My lathe (a Portass PD5) has a Brook Gryphon single phase 0.33HP motor. It has 4 terminals, which currently have 4 separate wires to the Dewhurst switch. I'm tidying up the installation, and am planning to replace the 4 separate wires with a 5-core cable (for the 4 terminals plus earth). The colours available in the cable are blue, brown, black, grey and yellow/green. Obviously the yellow/green one should be earth, but is there a standard or recommended allocation of colours for the other terminals? By instinct I think I would use blue and brown for the main winding (brown for live, blue for neutral) and black and grey in some random order for the start winding. Any comments or suggestions?

Thanks - Rowan

If I have measured/calculated this correctly DP is about 12 (a 65 tooth gear has an outer diameter of 106.8mm). What does CI mean for the Myford gear?.

Thanks - Rowan