large steel disc’s

[clogsParticipant @clogs]

need to make around 10 large steel disc's from 10mm thick strip…..

ranging from 6" – 10" o.d……..no center hole, accuracy within 1mm………due to geography cannot get them flame or plasma cut and have no facility's myself……..obviuosly to big for a hole saw….

I run a Bridgeport J head….Is there a tool that can be used on the B.P. for the job……I dont fancy drilling a million hole's to make the disc's then knocking them outta the plate PLUS, ideally I need a machine quality finish to the outter edge…..

any idea's……ta, clogs

[clogsParticipant @clogs]

[Tractor manParticipant @tractorman]

Can you have 10mm slices sawn from round bar stock at a steel supplier? The firm I use make base plates for fence posts that way slicing six inch bar on a band saw.

[JasonBModerator @jasonb]

Posted by clogs on 24/01/2018 07:02:00:

I run a Bridgeport J head….Is there a tool that can be used on the B.P. for the job

Rotary table would do it. may want a sub plate if table too small to mount 10" disc and just move the clamps as you go. Knock the corners off the plates first with a bandsaw or angle grinder.

[clogsParticipant @clogs]

sorry, tractorman……..

my first thjought after plasma cutting…….I live in the boonies outside the UK………can't remember the last time I saw anything that big…….

was thinking along the lines of a single point cutting tool along the lines of a large fly cutter……..

spose could get the job done in the UK and then ship…..

still cheaper than getting it done here I guess…..clogs……..

there's gatta be a way to do it myself with what I got…..

[Ady1Participant @ady1]

Draw / mark out on plate

Angle grind square sections

Drill centres for arbour— NO CANT DO THAT

Use centre mark on 4 jaw chuck on lathe

parting tool your way in on 4 jaw supported by live centre

Can only do up to 8 or 9 inches on a Drummond though

[HopperParticipant @hopper]

How big of a lathe do you have? you could treppan the discs from squares of flat plate on the lathe.

If you can't drill holes in them for clamping to the faceplate, you could weld something on the back to hold the disc by then angle grind it off afterwards. Or just clamp it on the corners with clamps I suppose.

Would be less rectum-clenching to use the mill and rotary table though, I reckon. But do-able if you grind your trepanning lathe tool with extra clearance on the OD side and cut in several stages, moving the tool inwards toward the centre at different cuts so you end up with a groove that is mostly a fair bit wider than the tool bit, to allow swarf clearance and minimize jamming. It's just like parting, only on a curve!

Edited By Hopper on 24/01/2018 08:58:40

Edited By Hopper on 24/01/2018 09:02:15

[TomfileryParticipant @tomfilery]

Clogs,

I know you said laser cutting was no good, but a quick check on eBay shows SGS Metals do 10mm thick discs in a variety of dimiters (sic) – 150 dia for 4.50 quid and 250 dia for 12 quid. Plus 6.50 postage. Might be easier in the long run, though depends on your budget.

Have no connection with them, nor have I ever used them.

Regards Tom

[not done it yetParticipant @notdoneityet]

Hopper is right. If in mild steel, there might be little problem with even a hole for an arbor – just weld it up and face it later. Even more than one, if bolted to a face plate.

I would be careful if using a rotary table. Other than a light finishing cut, unless the table drive were adequate for this type of work, as I believe that many modern designs are clearly not up to the job.

Fly cutting may be the answer, but likely considerable power/slow speed required for a large diameter?

[BazyleParticipant @bazyle]

Hacksaw and angle grinder to about 2mm of final size maybe using wooden jig to hold grinder like a sanding table.. Then if you don't have a rotary table it would be worth while using a bit of the stock to make a jury rig one – ie plate with hole in middle for bolt down to T-nut on mill table. Then superglue (even hide glue if you are really out in the bush) and fine cuts with the mill to final size.

I think you are outside the sensible range for a trepanning tool in the mill.

[John McNamaraParticipant @johnmcnamara74883]

Hi

10mm steel s not that hard to cut with a thin 5" grinding disk. If you can't find someone that can plasma cut them for you. in the bush there is usually access to oxy cutting at the local garage, you will need a bigger gap 2-3mm should be enough, less than that if the operator has a disk cutting jig and knows how to use it.

I would scribe mark the plate with a compass then cut the corners off at 45 degrees leaving a mm or so gap to the scribe line then trim the 8 corners left again and so on until i was near size. Let the disk do the cutting as you work it along the line, don't push it

You could finish off with a bench grinder if you have one. working your way around the disks grinding up to the scribe line. otherwise a side cutting 5" recessed centre disk in the hand grinder will be OK for the finishing.

For a job like this I would take the work outside and set up a work surface at the right that I could clamp the steel plate down rotating for each cut and leaving the cut line over the edge. This leaves you two hands to control the disk grinder.

Also needed will be Eye protection a dust mask and ear protection, you will be making a lot of noise and dust, and you need to protect your eyes.

Regards
John

[Clive FosterParticipant @clivefoster55965]

I've used a similar method to that suggested by John McNamara, albeit not with disks, and can confirm it works well.

For disks I'd spend bit more time marking out tho' by doing 4 hexagons about 15° apart. Hexagons are easy to do as being the chord equal to the radius of the circle. So you just draw a circle and step round it then join the marks with a ruled line. Just remember its the inscribed circle that needs to be your specified diameter so the radius of the circle you draw needs to be larger than that of the disk **LINK** is a handy calculator. 4 hexagons gives you 24 points to knock off so very little left to clean up afterwards.

Flap disk is faster than file for clean up if you have a steady hand. Vertical bandfacer / linisher is great if table is large enough to support the disk. Leather gloves, hold tight and only use light cuts.

Used a Chester Lux style vertical mill to produce a couple of decently accurate 3/8" thick disks in pre Bridgeport days. Vertex 8" rotary table with "improved wood" sacrificial table. Perm one from good MFD, high density chipboard or chipboard underfloor for the sacrificial table. Have used all for such duties at some time, don't recall what I actually used for that job. Made a cavity to locate the parent piece central. Probably just screwed a thin piece of ply on top and trimmed a hole to right shape for the blanks with a router cutter on t'mill.

No access to rotary table slots for clamps to hold the material down so wood screws and washers rammed in with the power screwdriver had to do. Using a suitably large drill, selected so one turn of the handle left a small web between holes, I quickly mashed out most of the material. Similar but uneven webs being of no consequence. A slot drill of, probably, around 1/2 to 2/3 rds drill diameter (used what I had), made the accurate to size cut. Went round 2 or 3 times to get an appropriate depth of cut without excessive load on the stock. For the last cut I added more wood screws and washers to teach the inner piece manners. No longer recall the exact technique but I imagine I made the releasing cut in incomplete quadrants leaving 4 webs at 90° intervals then added more screws as close as possible to each web so the piece didn't escape on break-away.

Got good disks and didn't break a cutter so I guess that was result. In practice probably less of a faff than it seems from the written description. As is so often the case I find taking time and trouble to sort out a right first time with no fettling method is faster overall than diving in with fast rough first cut then spending ages cleaning up to size. YMMD.

Clive.

Edited By Clive Foster on 24/01/2018 13:35:38

[JohnFParticipant @johnf59703]

Frank/Clogs have a look at your email account John

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