Need a perfect 8mm hole - to ream or bore?

[HankMcSpank]

Hi there,

(apologies, I think I'vetouched on this before, but I need to press on and actually do it, hence more detail needed from this related line of questioning)

I'm making a plate to mount on a stepper shaft...the stepper shaft is 8mm.

Now I want no slop on the plate whatsoever, so I want the hole in the centre of the plate to be a pretty perfect fit - 8mm.

Now I've never really used my lathe that much in anger, so I'm wet behind the ears wrt getting this perfect 8mm hole. The Googling I've done suggests that drilling a smaller hole then either reaming or boring out the hole to size is the way to go.

Which is the easiest, which is the cheapest (tool wise) & HTF do I do it! Seriously, I looked up reaming - and apart from a couple of porn sites (which I enjoyed very much) there's cack all out there illustrating how it's done - does the reamer go in the tailstock? Or if using a boring bar, does that fit in the toolhoder as normal - what size boring bar should I buy for an 8mm hole blah blah (you get the picture ie "this joker should not be allowed anywhere near a lathe", etc)

Thanks for your help.

Hank.

[Kn8]

Hi Hank have a look at
http://www.woodwindcourse.co.uk/user...ng_reamers.doc

I hope it helps.

Regards.

Ivan.

[irving2008]

Chuck up workpiece in lathe (or clamp to faceplate), drill out 6mm or so, using drill in tailstock chuck. Small boring bar in toolholder, insert into hole taking light cut open hole out to required size. For what you want you can get accurate enough with boring if you use short tool to avoid tool shank bending and use a light cut can cut 0.05mm undersize then trial with stepper while still chucked until tight push fit (if its close enough you can heat workpiece with hairdryer to expand it and it will be a tight fit when it cools). I dont think you need to ream it, but if you do want to, bore out 0.2mm undersize then ream with reamer in tailstock chuck.

[ptjw7uk]

Now you have the reamed hole how you going to fix it to the shaft?
Usual way is to drill and tap a hole or holes for grub screws etc otherwise what yo fix will spin on shaft.
Peter

[HankMcSpank]

Thanks guys...I now realise I didn't give enough info!

I've just bought a slug of 60mm diameter ali... it's 100mm long off which I will cut a slab of 30mm mount in my lathe to work on.

I will turn don about half of this workpiece down to leave flange on one side of the plate, which will have a grub screw going through it to grip the stepper shaft (I'll put a flat on the stepper shaft).

Therefore this 8mm hole needs to run 30mm deep through my workpiece. So is it possible to buy a boring bar that would go into say a small 7mm hole and allow me to cut 30mm into the ali?

I guess a reamer would be my best option but they seem to run a bit expensive and I'd need one per hole diameter type (I like the flexibility/flexibilty of a boring bar) ...have I git this right?

cheers,
Hank.

PS to refresh your minds (or show those that missed my first time round of questioning!), here's the bit I now need to make out of ali...

http://img160.imageshack.us/i/14811707.jpg/ - ie the round transparent faceplate in the piccie.

[BillTodd]

The great advantage of boring in the lathe is getting the OD and ID concentric.

Why not make a boring bar? The picture of the ones attached are simple steel rods with a cross hole, to take the cutting tool, and a threaded axial hole to fix it. The cutting tools are ground from broken reduced shank carbide PCB bits.

The smallest one shown here is 5mm Diameter, used to cut the 2" deep, 5/16" ID, LH acme thread for my steady rest support arms.

[irving2008]

Yes, you need one like this 5mm head on a 6mm shank (top one on page). If your normal lathe tool is bigger than 6mm then you might want to make up a boring bar holder (or buy one) to hold the cutting edge at the right height.

Boring is not as accurate as reaming, but within 0.05mm is possible with care and light cuts and thats easily good enough for this need.

[BillTodd]

I slap in a 6.5mm drill - it bends about like a bendy thing in Bendy Convention.

! in ally???

Are your drills sharp? Is the lathe turning in the correct direction?:rofl:
Is the tail-stock aligned correctly?

Drilling a hole in aluminium should not cause you any problem. Similarly, if your boring tool is sharp, it should easily cut a clean hole.

What depth of cut are you trying?

[HankMcSpank]

! in ally???

Are your drills sharp? Is the lathe turning in the correct direction?:rofl:
Is the tail-stock aligned correctly?

Drilling a hole in aluminium should not cause you any problem. Similarly, if your boring tool is sharp, it should easily cut a clean hole.

What depth of cut are you trying?

Dril bits were brand new (they are jobber bits - cheap as chips, but I figured on throwing them away and starting with a new one very regularly)

Yes the lathe is turning in the right direction (BTW, I'm not offended - it's a valid question with someone new like me!)

Re the tail stock alignment - this (I think) may be the root of my problem - how can I check it's alignment to see if it's within tolerance?

Thanks.

[Robin Hewitt]

Re the tail stock alignment - this (I think) may be the root of my problem - how can I check it's alignment to see if it's within tolerance?

Centres in both stocks then nip a thin piece of metal between them.

If it twists you are misaligned