New lathe arrived today : The ongoing saga

[Brian JohnParticipant @brianjohn93961]

Once I got down to 6.1mm then I was shaving off a small amount at a time ; the smallest I could manage. But the last cut was much larger than it should have been and I am not sure what went wrong.

There is still too much play in the top slide and the cross slide. I thought I sorted this out the other day but I will have to have another look tomorrow.

Edited By Brian John on 04/09/2015 08:26:46

Edited By Brian John on 04/09/2015 08:28:53

[Neil WyattModerator @neilwyatt]

Posted by John Haine on 04/09/2015 08:15:42:

Neil, metric lathes are normally calibrated in diameter mode, certainly all 3 I have had are that way.

My metric cross-slide isn't.

Neil

 

Edited By Neil Wyatt on 04/09/2015 08:46:27

[Neil WyattModerator @neilwyatt]

Posted by Brian John on 04/09/2015 08:26:08:

Once I got down to 6.1mm then I was shaving off a small amount at a time ; the smallest I could manage. But the last cut was much larger than it should have been and I am not sure what went wrong.

This isn't unusual if you are taking very fine cuts – its better to take decent sized cuts with any lathe.

[HopperParticipant @hopper]

Posted by JasonB on 03/09/2015 14:58:44:

…

Edited By JasonB on 03/09/2015 15:01:46

Brian, it looks on this photo like you may have a chipped or worn cutting edge on this toolbit, although hard to tell in the blurry pic for sure.

I've got a good bench grinder if you want to drop around sometime and we can give your toolbits a bit of a touch up. And i can show you how to grind a more conventional toolbit from scratch on the other end of one. It's easy once you have been shown how.

[JasonBModerator @jasonb]

No chipped tool, look at the link to the ARC toolbits posted earlier they are made like that. All that is needed to sharpen is a quick touch of the end on a grinder.

My small Unimat 3 which is quite similar is callibrated for tool movement not dia. My Imperial lathe is callibrated for diameter

Brian I suspect that when you drilled the hole you removed any of the tapered hole that the ctr was previously resting on and when you brought up the ctr again it located against the hole. Net time gio in deeper with the centre drill so it leaves the tapered hole larger than your intended thread dia, say 4mm across for a M3 thread. You are using a centre drill for the tailstock to go into, your spotting drill is no good for this as its the wrong angle.

J

[HopperParticipant @hopper]

Posted by JasonB on 04/09/2015 09:28:51:

No chipped tool, look at the link to the ARC toolbits posted earlier they are made like that. All that is needed to sh

J

I understand how the tool is made and works, but it looks like the lefthand edge at the very end is not straight. But it might be just blur on the pic.

[Gas_mantle.Participant @gas_mantle]

Posted by Hopper on 04/09/2015 09:35:48

I understand how the tool is made and works, but it looks like the lefthand edge at the very end is not straight. But it might be just blur on the pic.

What looks like a chip I think is actually the edge of the topslide showing from behind, if you look it's line with the rest of the slide to the bottom right of the tool.

[Brian JohnParticipant @brianjohn93961]

Jason : that might explain what has happened. I am using the centre drill to make a hole for the dead and live centres. I only use the spotting drill for drilling the hole in the flywheel.

Hopper : thanks Pete. I am working the next three nights (and sleeping through the day) but I will call you next week to arrange something.

[HopperParticipant @hopper]

Posted by Brian John on 04/09/2015 10:58:36:

Hopper : thanks Pete. I am working the next three nights (and sleeping through the day) but I will call you next week to arrange something.

No worries. I am around on weekdays.

[Brian JohnParticipant @brianjohn93961]

I think the problem with using an external thread is that you limit yourself to the size of flywheels that can be machined. I have flywheels ranging from 20mm to 27mm thick. I think the expanding mandrel will be more useful. However, I will have a go at making the external thread version as well. Today I have cut three more pieces of aluminium bar stock (using the jig saw). I then faced off the ends and centre drilled them ready for turning tomorrow.

Of course a face plate would be much more versatile and one will have to be made or acquired eventually.

[JasonBModerator @jasonb]

If you leave 19mm of unthreaded length on the manderel that will be sufficient for all widths of flywheel, just wind the nut on bit more for the narrow ones. Or leave 26mm unthreaded and just put a few washers under the nut when you do the narrow ones.

J

[Gas_mantle.Participant @gas_mantle]

Brian,

I don't know how big you are intending to make wheels but here's a mandrel I made for a wheel 20mm thick wheel (I think 65mm dia) it worked fine and I'm sure using the same principle I could make one a bit bigger within reason.

[Brian JohnParticipant @brianjohn93961]

I have just had another look at my box of flywheels : the thinnest hub is 14mm and the thickest hub is 27mm so I think a few different mandrels with different threaded lengths may be required. But first I have to make at least one of them ?

[Gas_mantle.Participant @gas_mantle]

I don't know how others go about it but I make a mandrel as a 'one use only' item, once you remove it from the chuck you'll find it very difficult to get it back on centre for multiple uses.

I'm not saying an expert can't do it but as a beginner I'd far sooner spent 10 mins making a new mandrel knowing it will central to the lathe axis.

[Ian S CParticipant @iansc]

I use a mandrel for turning some parts I make for agricultural machinery, I use a bit of 2" bar with a 35 mm spigot on the end and a 3/8" UNF hole for a bolt, and heavy washer(10 mm thick), this is used to turn the 150 mm outer diameter of a 8 mm thick hot rolled steel disc, and also to groove 100 mm dia pulleys. To get it to run true I mark it with a centre punch each side of jaw 1. It's done a few hundred items with no slip, or other troubles.

Ian S C

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by Peter Nichols on 05/09/2015 12:42:26:

I don't know how others go about it but I make a mandrel as a 'one use only' item, once you remove it from the chuck you'll find it very difficult to get it back on centre for multiple uses.

I'm not saying an expert can't do it but as a beginner I'd far sooner spent 10 mins making a new mandrel knowing it will central to the lathe axis.

If I can, I make my mandrels out of PGMS – that way I can return them to a collet to get concentricity.

Rod

[Brian JohnParticipant @brianjohn93961]

I started to make some reducing cuts on the mandrel (first photo). Once I get down to 10mm then the dead centre gets in the way. How do I get around this ? What I was doing last time was putting the cutting tool at 45 degree angle to do the right hand end and then putting it back to 90 degrees to finish up to the shoulder. This seems a bit clumsy and maybe I am missing something ?

I also cut up some 25mm aluminium bar (second photo)  which I bought from the scrap yard for a few dollars as I thought it might be useful. I used the jig saw fitted with a metal cutting blade. Even though it was aluminium it still took a long time ! How would you cut metal of this thickness. I also have some 40mm aluminium and some 30mm brass ; I am not looking forward to cutting this up ! I really must buy a fixed steady  so that I can machine large diameters like this.

 

Edited By Brian John on 06/09/2015 08:28:56

Edited By Brian John on 06/09/2015 08:29:32

Edited By Brian John on 06/09/2015 08:31:25

Edited By Brian John on 06/09/2015 08:32:09

[BazyleParticipant @bazyle]

Sometimes you have to do things by hand. Use a regular big hacksaw. When you have done a few cuts in 3 in steel you won't be bothered by a little bit of aluminium.. Keep a separate blade for alloy as it will blunt on steel.

Your lathe piece is still sticking out too far from the chuck. It should be in the same place as it will be when you put the wheel on it – so right up clos to the jaws . For the cut close to the centre you would use a "half centre". or one that is just smaller if you can find one.

For multiple thickness wheels use a threaded end type of mandrel for the longest and a stack of washers on the outside for the smaller ones. But now you have some smaller rod why not make a few smaller things out of that for a while to build up more expertise.

[Brian JohnParticipant @brianjohn93961]

The piece is in the chuck as far as it will go so tomorrow I will cut some off to reduce the length.

It is a bit of a problem finding parts with an MT1 taper. There is not as much available as MT2.

[HopperParticipant @hopper]

+1 on use a vice and full-sized hacksaw to cut stock. For ally you want to use a coarse pitch hacksaw blade, probably about 18TPI or fewer. Rule of thumb is the softer the metal, the coarser the blade. So for steel you would use a 24 or 32TPI blade. Brass will take a coarse blade like ally. Both ally and brass cut like butter with a good hacksaw.

Same rule of thumb applies to your jig saw blades. A fine tooth blade will clog up and take a long time to cut through ally. A coarse metal-cutting blade will rip through it like wildfire.

However, for cutting thin walled tube or thin sheet of any material, a finer blade will work easier without getting hung up.

It looks like you are getting the hang of things as you go along. Good stuff!

[Anonymous]

Bother, looks like I've been doing it all wrong. I have three manual hacksaws with 18, 24 and 32tpi blades. I always use the 18tpi hacksaw, irrespective of material, unless the section to be cut is too narrow. I work on 2, or preferably 3, teeth across the width to be cut.

Andrew

[Brian JohnParticipant @brianjohn93961]

I have set of metal cutting hack saw blades : 14T, 18T, 24T and 32 T. I was using the 14T blade but it still took much longer than I thought. I will try a large hacksaw next time. Now that I have cut them to a manageable size I could also cut them into smaller lengths by parting off on the lathe. That might be a good idea as I need the practise ! Perhaps part them off to 1/2 or 3/4 the diameter and then finish with the hacksaw ?

I did read somewhere that some people use a hacksaw blade somehow mounted horizontally in the tool holder. How would that work as you cannot apply any pressure unless the blade was mounted vertically ? Although, I suppose any slight angle larger than 90 degrees to the horizontal might suffice.

 

Edited By Brian John on 06/09/2015 12:09:03

[JasonBModerator @jasonb]

When you go round to Hopper's get him to show you how to grind up a more pointed tool which will allow you to get in a lot closer to the ctr, no need to buy another one.

Edited By JasonB on 06/09/2015 13:01:23

[Chris DentonParticipant @chrisdenton53037]

Have you glued something in that to stop it compressing?

[JasonBModerator @jasonb]

yes, couple of scraps turned to a good fit and glued

[Author]

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