Holding cylinder in vice for boring, what angle to make jaws.

[Ttrees]

Hello folks, so I've had to ditch the case hardened lump of metal which I was planning to make a part from.
As an aside, it will be used as a bench grinding dressing tool, and looks to be even more effective as the hungriest dresser that one has ever seen.
In less than 5 mins, to turn a new 8" wheel into something which you would be swapping on a 6" machine!

So basically learning on working plastic or derlin material instead of steel which is teaching me some lessons.
Not getting a good hole, and the bits are stalling a bit much
(I need change me belts on the pillar drill, but I'm guessing not bad practice should one be very patient like myself, to make do with plenty of slip, as I'm drilling these out to 30mm)

Lets forget about that though for the minute, and focus on my setup
Sorry don't have new piccies, but its pretty much the same size part from plastic rather than steel.

Table and vice was already trammed, and hole was already accurately pre bored to 10mm BTW.

Used a similar setup block underneath, but wider for allowing parallels/soft jaws.

The issue I'm thinking is, that I need some sort of angled block to get at least 3 points of contact, rather than squeezing the part making two.

Will making blocks which hold the work at 45 degrees be optimal for this task, or is there a better way to hold the work, or possibly different angles than 45...
Is three or four points better for the job?

Thanks
Tom

 

[Alpha-Dave]

I have found that the 3x contact points on my Sevo vice are perfectly adequate for holding cylinders. Note that I’m using the ‘round faces’ on the mobile jaws to hold the cylinder, not the flat ones as shown in the second picture.

Also note that they solidly lock in those positions, not freely-swivelling.

 

[Ttrees]

Thanks AlphaDave
Without knowing if an end mill reduces this pinching occurrence or if the drill is a worse offender
I'd take a pot shot guess the end mill would be more apparent, so am guessing that's quite a tolerance you are working to.

Have you ever tried the same on plastic?
Not that I can say for sure that the holding of the work was certainly why this has happened, but I think its likely the case as the biggest factor.

Something tells me that it would still be the same should I have 3 points of contact which is not symmetrical.
If this is the case though, then I should ask if that particular vice is intended for use as such, as it doesn't appear that the pair at the rear of the photo spread apart far enough to
enable a symmetrical arrangement....
(unless I'm missing something)

Ps thanks for giving me the correct terminology for my post.

Thanks

Tom

 

[Terry - Somerset]

With thick walls, three points of contact will be adequate as the component is unlikely to deform under the pressure of a tightened vice.

I suspect the ideal would be (a) to have the points evenly spaced, and (b) for deformable items (plastic) the more contact points the better. So I would go with vice jaws angled at 45 degrees to give four points of contact.

I assume the drill is sharp and the speed is adjusted appropriately.

 

[Ttrees]

Thanks Terry, then four it is, unless someone can talk me out of it

Drills are likely as good as I can get them.
And my adjustable speed pillar drill is down to one speed due to the belts stretch factor,
Which happens to be a universal speed lol
Very underpowered as it is for the likes of what I'm doing, so its very slow going.

Cheers
Tom

 

[Phill05]

Ttrees, you can make a simple V block use against one side it will stop any movement can be in wood plastic or even better metal.

Edit: add image

 

[TRITON]

Know anyone with a 3D printer ?

 

[Ttrees]

Thanks again folks, I was just worried that a 45 v groove might still have the same effect
as just two points with this plastic.
Might be having another bash at this yet, so will report back with how I get on with a pair of 45 blocks.

Cheers
Tom

 

[Fergie 307]

+1 for Phil's blocks. If the jaws on your vice are removable then you could consider making up a set with a central vertical v groove, and also a horizontal one in each That makes it easy to hold round bar either vertically or horizontally, and you can still use the vice as a parallel jaw without having to change anything.

 

[TFrench]

When I have to hold a cylinder in the milling machine vice I just use a little eclipse vee block.

 

[johnbest981]

+1 more for Phils blocks, and Fergies explanation.

With the plastic being softer you are more likely to bend it if you overtighten - but the benefit of it being plastic is the drill will require less force to go through it so you wont have to haunch it up so tight.

If your machine is stalling drilling out that size then a good idea is to start with a centre drill (although again, less important on soft plastic), then pre drill the size of the web on the big drill (the bit at the very tip of the drill where the two cutting flutes meet) probably around 3mm on that drill. That'll take out a heap of effort that the drill has to work but will leave enough material for the drill flutes to "get under" and stop the chatter you can get from pre drilling the hole too big in a "stepping up" the drill sizes method.

 

[Fergie 307]

When I have to hold a cylinder in the milling machine vice I just use a little eclipse vee block.

I bought a couple of the ones that are square with a v groove on each side, about 4 inches long and maybe 2 inches square. Found them in a box of bits at the local car boot, a bit bashed about but ideal for holding stuff in a vice, only cost me a couple of quid and use them all the time.

 

[Ttrees]

Seems I might be worrying about nothing, although I suppose I'll have to see yet if four points is enough support to hold without deformation.

No bother now getting things done a bit quicker, now I've got comfortable with the poor mans cross slide on the lathe, ends faced and beveled fast,
and have plenty of stock to redo the part.
If the four points dont work, I might make another set of v blocks and just stick a clamp on them.

I've figured out the dimension I need with the part, so won't be making another pair
until I disassemble the machine again.
I am going to do a test and thorough checks as I am curious about a few things on the machine, so don't want to do too much at the same time.

Stuck old Koyo bearing (likely needing proper cleaning and repacking yet)
into the wheel as it has less chamfering on the races compared to the SKF ones.
So I made sure I HAVE to disassemble again, as I guess it will get noisy fast, so will be making another pair soon.

Glad to report that no looseness is apparent like it was before, phew, thought my bore got a bit worn, but it was only the bearing dropping further in and out of the wheel, (old bearing spacer wasn't parallel)
Quite apparent the change as the washer actually is pressing on the inner race now.
An easy thing to spot now, should one have worn plastic spacers on their machine.

Will be interesting to see how things fair when drilling.
Might try to make a juicy post should I still fail making the holes spot on.

Thanks folks

Tom

 

[Fergie 307]

+1 more for Phils blocks, and Fergies explanation.

With the plastic being softer you are more likely to bend it if you overtighten - but the benefit of it being plastic is the drill will require less force to go through it so you wont have to haunch it up so tight.

If your machine is stalling drilling out that size then a good idea is to start with a centre drill (although again, less important on soft plastic), then pre drill the size of the web on the big drill (the bit at the very tip of the drill where the two cutting flutes meet) probably around 3mm on that drill. That'll take out a heap of effort that the drill has to work but will leave enough material for the drill flutes to "get under" and stop the chatter you can get from pre drilling the hole too big in a "stepping up" the drill sizes method.

Good advice there. The problem is if you only have the two flat jaws then any catch or chatter will tend to cause the piece to tilt along the line of the jaws, having at least a third point of contact prevents that happening, and allows you to hold it firmly in place with much less force on the jaws. I was always taught that a pilot hole should never be more than half the size or less compared to the finished size. So for 10mm, maybe a 4mm pilot hole. If you go too big then all the work is being done by the very edge of the flutes, which can then overheat, chatter and blunt the drill much more quickly than if you are spreading the cut across most of the edge. The only exception is probably any kind of thermo plastic, where you need to be careful as drilling a large hole in one go can heat the plastic up too much and start to melt it. In that case taking the hole out in smaller steps is probably a good idea. I work in Delrin a lot and the most important thing is to make sure your cutting tools are razor sharp, a blunt tool or drill will tear rather than cut it. Have fun.

 

[Fergie 307]

And if you are machining Delrin, or pretty much any plastic on a lathe my advice would be to use HSS tools in preference to carbide, and make sure they are really sharp. And bear in mind if you work it a lot it will get hot and expand, so if size is critical then machine it to within say 1mm of the finished size, then let it cool down fully before finishing to size.

 

[Alpha-Dave]

If you want to be certain of no movement, then the solution would be to drill/cut a round hole in a block of metal the size of the workpiece, then split it in half and drill&tap it so it can go in place of the vice’s jaws. That would give almost perfect contact around the entire cylinder with very little pressure needed, so no deformation.

That is probably only worth doing if you have to make lots of the same thing or very litte material for the work.

 

[Ttrees]

@Alpha-Dave that sounds like it would be the solution if all else fails.
No hefty blocks of metal around, as I'd be making steel parts rather than plastic.
Have some suitable plastic which is a bit poisonous to work, harder than the plastic I'm working on, which would do,
but I will have a wee mock up with wooden blocks first.

Lots of options it seems.
Thanks for the input everyone.

Tom

 

[Ttrees]

Hello again folks
Sorry been such an age with this, I've been pestering ye with loadsa drilling queries
and as always pure speculative once again.

Not sure if the jaws worked or not, clearly I'm not doing something right yet, although
things are maybe progressing...as in the process of elimination is lessened somewhat
Just to give an insight into my setup...

Table locked tight and trammed beforehand

And double checked the vise which was also bang on

Jaws made

Also took the time to make a quick drill sharpening gauge which was enlightening

Now to the speculative bit
I am going to setup a jack anymore for the table, might buy a bottle jack if they are cheap enough.
Say I do and that's taken out of the equation.

What I haven't seen is a centering bit for the pillar drill, since it would be nice to center on with this pre bored cylinder, which seems spot on, and the bottom faced on a lathe.

I can only guess it is the issue, although my clamping setup could do with deeper clamp
but lets not go there, as I've had these same issues with the mounting plate in the other axis also, it's flat as a pancake and doesn't tip, even when clamped like above.


...................................
What I've been doing is as follows...

A bit of a sloppy fit in this pre bored material, for the drill to truly hit dead center,
but the issue seems to get worse progressively...

Sounds very confusing looking at my writings, better number this instead in a progressive fashion.

1 Table locked
2 Center the drill in accurate hole as good as I can get it
3 Vise jaws flush with that stick in my hand and tightened,
4 Vise clamped to the table

Unlock lever and drop table enough to swing away
Switch to the next size up, (my machine is really needing belts, no beans to take decent chips)
Don't seem to have a photo, what I was hoping would be the most sureworthy gamble in regards to aligning the table back up once one changes a bit,

So far, my thinking was to ever so lightly engage the bit into the work while hand turning it backwards, praying that it would center up,
and progressively tightening the table lock whilst turning the bit.
Clearly this doesn't seem to be working for me,
so I'm guessing there is something I'm missing on here.

I'm starting to question if I should attempt lowering the table enough so I can change bits without moving the table, or at least having it somewhat lower,
enough to swing the table over and change to another bit,
and also using some sort of centering bit to keep an eye on things.

Keen to see what ye say.
Maybe it's all down to the bit of flex in the table, but to be honest, the machine needs a bit of babying in regards to taking heavy cuts, so I take it easy.


Thinking some more about this, maybe some sort of support for the table for use with a jack or other solution, and another bracket to make some sort of horizontal stop for it also would possibly count those two issues out.
Don't think there is that much runout on the machine TBH, likely would be noticable with a 30mm bit at unsuitable RPM's if belts were tight whatsoever, and not inspired to go delving into that, better things to be doing,
don't mind making something that is a bit more simple like welding up some brackets or whatnot, that seems progressive compared.



Thanks for reading

Tom

 

[Jacko264]

I hope you under stand this idea
turn the drill bed 90% then bolt the vice to the bed with the jaws vertical
put the metal in the vice so the drill goes though it
as I Said it’s only a idea of mine
or drill it in a lathe
Graham

 

[Ttrees]

I hope you under stand this idea
turn the drill bed 90% then bolt the vice to the bed with the jaws vertical
put the metal in the vice so the drill goes though it
as I Said it’s only a idea of mine
or drill it in a lathe
Graham

I'm failing to see what could be achieved here, apart from the possibility of a slighter
more rigid setup, as these parts are shallow enough to be drilled as is,
unless you mean some possible method for steering the bit by unlocking and rotating the table ever so slightly.

I flipped the first component around after drilling half way, and I've gotten away with
better results many times rather than attempting drilling at any depth.
Just to test this I tried without flipping and indeed the result was indeed worse.

Thinking the solution might be a centering cone, and some horizontal stop for the table.
and proper support under the table.

Love to acquire some more knowledge, but annoyingly most machinists don't hang around fighting with a machine which is not seemingly the tool for the job,
well... for a machinist and not a chancer like myself,
This machine seems adequate for me, and definitely worth doing a bit of engineering on.

Curious why I haven't seen much to do with drilling accurate holes using a bog standard pillar drill, although I've not watched all the youtubes.

Cheers
Tom