Turning down backplates

[Andrew TinsleyParticipant @andrewtinsley63637]

I have purchased a couple of 5" Myford backplates from Warco's current sale.

I intend to use them for two Pratt Burnerd Griptru chucks. These are 3.5" chucks, for my ML7.

I cannot take industrial size cuts on the ML7, so it looks like I am going to make an awful lot of swarf. I started to wonder if there was a less messy way of reducing the 5" diameter. Nothing has clicked, so I am asking the forum members if I am missing a trick?

I know I should just get on and turn them down and cope with the swarf!

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

[Speedy Builder5Participant @speedybuilder5]

You could trepan the "outer ring" away from the backplate, but by the time you have ground up a special tool and then found no use for the 'ring' you would question why!

[Robert ButlerParticipant @robertbutler92161]

Saw surplus to produce Octagonal shape much nearer the required diameter.

Robert Butler

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Andrew, you could use a suitable size hole saw maybe, but you would probably have to put a tapered piece in your bore for the pilot drill, or you can just face the register for your chuck to fit, and leave the rest at 125mm diameter.

Regards Nick.

[Grindstone CowboyParticipant @grindstonecowboy]

To be honest, there's nothing to stop you leaving them as is, and just turning down the register to fit your chucks. I have one mounted like this, and it's never caused me any issues. Additionally, you could drill a series of holes around the periphery and make an indexing device. Bonus feature!

Rob

Edit – Nick got there first!

Edited By Grindstone Cowboy on 12/05/2023 12:53:02

Another edit as I can't spell chucks

Edited By Grindstone Cowboy on 12/05/2023 12:53:45

[DC31kParticipant @dc31k]

A possibility is a rear toolpost and upside down tool. That could manage and direct the swarf in a way that is less labour intensive.

I wonder if multiple plunge cuts with a parting tool would remove material faster than multiple OD turning cuts.

[Martin Johnson 1Participant @martinjohnson1]

I would guess they are cast iron, so it really should not be an issue to reduce the excess to swarf in fairly short order. Carbide tool, generous feed rate, modest speed, coolant to keep the dust down. Go for it.

Martin

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I nearly mentioned Grindstone Cowboy's idea about drilling index holes.

Regards Nick.

[HopperParticipant @hopper]

An ML7 will cheerfully take 100 thou deep cuts all day long. That knocks .200" off the diameter. So five passes and your 5" backplate is down to 4" inches already. Couple more and you you are there at 3.5".

You will probably need to use top backgear at that diameter with HSS tooling. Or use carbide xxGT inserts and run a bit faster, maybe 200rpm (lowest non-backgear) and really shift some metal.

Won't take long at all. Making swarf is what lathes are for. The finished job is just the leftover bit after the swarf is successfully removed to its rightful location in the tray. The backplate is only, what, half-inch thick? Not much swarf at all over that length.  Keep your fingers away from it and used a suitable old screwdriver bent over at 90 degrees at the end to safely hook swarf curls out the way as you go.

Another trick, if it is cast iron not steel and so firing off little fragments of swarf all over the place rather than long curls: Take a piece of cardboard (side of a fag packet is traditional), stab a hole in it with a pen or tool bit and slide it over the lathe tool bit shank so it forms a little shield that stops flying fragments going all over the place. Works great on brass and helps with cast iron too.

 

Edited By Hopper on 12/05/2023 13:10:08

[egaParticipant @ega]

Posted by Nicholas Farr on 12/05/2023 12:44:40:

Hi Andrew, you could use a suitable size hole saw maybe, but you would probably have to put a tapered piece in your bore for the pilot drill, or you can just face the register for your chuck to fit, and leave the rest at 125mm diameter.

Regards Nick.

Plus one for the hole saw.

I used to think that the pilot drill was essential but someone said not so and I have found this advice to be correct (I am, of course, envisaging use in a machine and not freehand).

[duncan webster 1Participant @duncanwebster1]

When doing cast iron and producing lots of dust I rig up a clamp to hold the vacuum cleaner pipe to catch the debris (I hesitate to call it swarf) Still cover everything possible with paper, not cloth.

[Andrew TinsleyParticipant @andrewtinsley63637]

A good slew of ideas. The obvious outside the box one, is to just turn up the register. It looks to me as if the Warco backplates are steel, I know that the ARC ones are. At just a few pence over £15, they are well worth a punt.

Thanks all,

Andrew.

[Grindstone CowboyParticipant @grindstonecowboy]

"a few pence over £15"? I'm only seeing them at £26.50, otherwise I'd get a couple too.

Rob

[Dave HalfordParticipant @davehalford22513]

Posted by Grindstone Cowboy on 12/05/2023 15:11:39:

"a few pence over £15"? I'm only seeing them at £26.50, otherwise I'd get a couple too.

Rob

Agreed.

Sale is over I bought some stuff that is now 40% dearer

Edited By Dave Halford on 12/05/2023 16:15:40

[Dave HalfordParticipant @davehalford22513]

Warco site is now showing reduced sale prices again

[Rod RenshawParticipant @rodrenshaw28584]

I would be tempted to just turn down the register and leave the rest at the full diameter. The remaining backplate should act as a flywheel and improve the finish when turning, and be especially helpful when doing interupted cuts.

[Howard LewisParticipant @howardlewis46836]

If the Backplate is cast iron, place a powerful magnet under where the swarf will fall, and cover it with a few sheets of newspaper ; taking care that it douls not get involved with the chuck.

The magnet will concemtrate a lot of the swarf in a heap.

When machining is finiished, the nwsparer can be caredully folded and the cast iron dust disposed of, with minimum cleaning up the lathe nand its surroundings being necessary.

Howard

[DalboyParticipant @dalboy]

Posted by Howard Lewis on 20/05/2023 11:04:49:

If the Backplate is cast iron, place a powerful magnet under where the swarf will fall, and cover it with a few sheets of newspaper ; taking care that it douls not get involved with the chuck.

The magnet will concemtrate a lot of the swarf in a heap.

When machining is finiished, the nwsparer can be caredully folded and the cast iron dust disposed of, with minimum cleaning up the lathe nand its surroundings being necessary.

Howard

I put the magnet into a large plastic bag and when finished just turn the bag inside out saves messing about folding paper and the chance of spilling some. There will still be some that escapes

[DalboyParticipant @dalboy]

Posted by Dalboy on 20/05/2023 11:30:58:

Posted by Howard Lewis on 20/05/2023 11:04:49:

If the Backplate is cast iron, place a powerful magnet under where the swarf will fall, and cover it with a few sheets of newspaper ; taking care that it douls not get involved with the chuck.

The magnet will concemtrate a lot of the swarf in a heap.

When machining is finiished, the nwsparer can be caredully folded and the cast iron dust disposed of, with minimum cleaning up the lathe nand its surroundings being necessary.

Howard

I put the magnet into a large plastic bag and when finished just turn the bag inside out saves messing about folding paper and the chance of spilling some. There will still be some that escapes but not a lot

[Martin Johnson 1Participant @martinjohnson1]

Why are model engineers so averse to cast iron swarf? If you want clean hands, clean tools and clean handkerchief you have probably taken up the wrong hobby.

Martin

[Author]

Posts