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Drilling holes using pillar drill - work wobbling

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petro1head16/01/2020 11:51:55
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730 forum posts
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I am sure I making some sort of school boy error

Using my recently refurbished Medding drill and a new Soba drill vice I drill a 6mm hole then want to open it up to 8mm using an 8mm drill. However when I offer the 8mm drill to the work the vice with the work wobbles about.

When I had my old Clarke drill with cheap Clarke vice this never happened so confused as to why it happening with the Medding.

For info I tried a different chuck and the bearings and quill are rock solid, unlike the Clarke.

The only difference is I had added an aluminium table cover to the Clark drill and the Medding table is steel. It’s also quite polished so could it be a lack of friction of the vice on the table?

Edited By petro1head on 16/01/2020 11:56:01

Ian Parkin16/01/2020 11:57:26
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704 forum posts
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Try bolting the vice to the table and make sure that the table is locked to the pillar

petro1head16/01/2020 12:10:00
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730 forum posts
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Hi Ian, yes there is that option but I am more curious as to why I have problems when I did not with the old setup

peak416/01/2020 12:21:43
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988 forum posts
98 photos

I'd suggest that with your previous drill press, any wobbling through misalignment was taken care of by the quill and chuck wobbling about.

Now you have something more rigid, that's transferred to the end of the drill.
Also, is you 8mm bit new, straight, and ground evenly?

Yes various ways of clamping the vice down, one quick and easy one is the over centre clamp, a bit like half a Mole grip.

Another thought, are you sure about drilling 6mm, and then opening to 8mm; this only allows a 1mm cut on each of the 8mm bit's flutes.
You might have needed to do that with your previous bench drill, but you've got a good machine now, so maybe a smaller pilot hole and then the 8mm.

Bill

Bill Chugg16/01/2020 12:46:20
1009 forum posts
7 photos

I would be inclined to use a step drill.

Bill

Andrew Johnston16/01/2020 12:58:14
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5115 forum posts
594 photos

Now you''ve got a man sized drilling machine just drill 8mm and be done with it.

Andrew

larry phelan 116/01/2020 12:58:22
579 forum posts
11 photos

I have often opened a 6mm hole to 8 or 10 mm without any wobble and my machine is not "Top-of-the-range" model, just a cheap Chinese Monday morning job. Very seldom do I need to bolt down the vise, the larger drill just centers itself.

But for anything bigger, such as 12mm, yes I do bolt it down, got fed up chasing the vise and job around the floor !wink

Clive Brown 116/01/2020 13:14:19
320 forum posts
7 photos
Posted by petro1head on 16/01/2020 12:10:00:

Hi Ian, yes there is that option but I am more curious as to why I have problems when I did not with the old setup

Are you using the same drill bits in both cases? I recently bought a "bargain" 1-12mm set of drills from my local engineering supplier. Most are OK but several of the larger ones are not straight. I first noticed this when using one in my Fobco. The hand-held workpiece wobbled about on the work-table. I don't think that this would have been too noticeable with a hand drill, but the rigidity of the bench drill showed it up.

Mike Poole16/01/2020 13:35:33
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2331 forum posts
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A pilot hole does not need to be any larger than the chisel point but for 8mm a pilot is not really necessary. This is virtually a counterbore job and they usually have a pilot to locate the counterbore but as they produce a flat bottom then there is no tendency to self centre. I would expect the work to dance as the drill needs to be sharpened perfectly and be absolutely concentric before starting to cut and even then it stands a good chance of grabbing. A normal length jobber drill is not rigid and any tiny misalignment or uneven cutting is going to start the wobble. I don’t know why you didn’t have the problem with your old drill but what you describe is to be expected in my experience, the dancing also tends to leave a rough edge to the top of the hole. A heavy vice and accurate alignment help but clamping is the best answer.

Mike

petro1head16/01/2020 14:08:00
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730 forum posts
143 photos

Thanks again for the replies

they are the same drills i used with the Clarke

in the meantime i have made some T nuts and am clamping down the vice, takes a little more time but job sorted

cheers guys

PS I have one of those mole type clamps but cant bloody find it

Edited By petro1head on 16/01/2020 14:10:31

Howard Lewis16/01/2020 14:17:00
2747 forum posts
2 photos

Sounds like one lip of the drill is cutting while the other is not. Consequently, the drill is trying to rotate the work.

This may be because of being loose, the drill / work alignment is poor.

If the vice is bolted down, it is far less likely to move, because you have greatly increased the rigidity of the whole system.

If the vice grip is inadequate, the drill could still pick the work out of it. .

Also you will have greater control over the feed rate, reducing the cutting force, and with it then tendencey to move.

Howard

Edited By Howard Lewis on 16/01/2020 14:18:00

petro1head16/01/2020 14:36:03
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730 forum posts
143 photos
Posted by Howard Lewis on 16/01/2020 14:17:00:

Sounds like one lip of the drill is cutting while the other is not. Consequently, the drill is trying to rotate the work.

This may be because of being loose, the drill / work alignment is poor.

If the vice is bolted down, it is far less likely to move, because you have greatly increased the rigidity of the whole system.

If the vice grip is inadequate, the drill could still pick the work out of it. .

Also you will have greater control over the feed rate, reducing the cutting force, and with it then tendencey to move.

Howard

Edited By Howard Lewis on 16/01/2020 14:18:00

Something to concider, how square the table is to the chuck, need to check, thanks

ega16/01/2020 14:39:44
1444 forum posts
118 photos

If you have a Bullet-style drill in the target size (ie with pilot nose) you can drill a pilot to match and the Bullet drill will then start cleanly and follow the pilot hole.

Edited By ega on 16/01/2020 14:40:26

Hopper17/01/2020 00:05:53
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3989 forum posts
85 photos

It's much safer to have the vice bolted down anyway. Even a spindly 3mm drill can pick the vice up, spin it around and toss it across the workshop. (Usually to crash into the freshly painted petrol tank of a restored motorbike or whatever single valuable but easily dented object is in the shed.)

Even when drilling holes where you want to "float" the vice around so it can find the right position as you poke the drill tip into the centre punch mark etc, it's safest to have the vice bolted down but with the bolts/nuts left loose enough to allow some movement of the bolts in the slots etc.

You could try speeding up your drill spindle too. It might cut down the amount of wobbling compared with a slower speed.

not done it yet17/01/2020 07:09:04
3946 forum posts
15 photos
Posted by 34046 on 16/01/2020 12:46:20:

I would be inclined to use a step drill.

Bill

Hi Bill, not a good idea if the hole is more than a few mm deep.🙂

Bill Chugg17/01/2020 11:15:52
1009 forum posts
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not done it yet 17/01/2020 07:09:04
3733 forum posts
15 photos
Posted by 34046 on 16/01/2020 12:46:20:

I would be inclined to use a step drill.

Bill

Hi Bill, not a good idea if the hole is more than a few mm deep.🙂

For some reason, I could only see this post when not logged into the forum so I have had to copy , then log in and paste to be able to respond, All a bit strange.

So, not done it yet, I would agree with you that you are limited to about 5mm but the thickness of the plate was not specified. IIn future I will keep quiet unless the full details are published.

Bill

Clive Foster17/01/2020 11:32:26
1992 forum posts
73 photos
Posted by Hopper on 17/01/2020 00:05:53:

Even when drilling holes where you want to "float" the vice around so it can find the right position as you poke the drill tip into the centre punch mark etc, it's safest to have the vice bolted down but with the bolts/nuts left loose enough to allow some movement of the bolts in the slots etc.

Perhaps a point in favour of the notoriously sloppy, affordable, import cross vices! As I've said before mine is good enough to quickly bring the work under the drill in, hopefully, dead nuts alignment. However if it is a touch out there is sufficient slop for the drill to bring the workpiece exactly where it wants it with no risk of the whole kit and caboodle being slung across the workshop.

A very large drill running slowly can also wobble the table on my big Pollard 15AY floor standing drill. That machine has proper square section vertical ways for the table to run on and a double screw jack to lift it. My gibs are set so it lifts and falls without undue effort so clearances are very small. But a big drill on bottom speed can still wobble it. There is provision to use one adjuster as a table lock screw but I've never bothered to actually use it. Given that it appears to have been painted over in the factory around 1950 something when, I think, the drill was made Mr Pollard clearly didn't consider it very essential for normal folk either. But there for the just in case jobs.

I get the impression that most folk are far too tentative with drill feeds and speeds. OK the book values probably assume good lubrication but push it in firmly at something approaching the correct speed and it will settle in cleanly without wobble. If you pull back before the drill has reached full diameter and the cut surface has visible radial ridges running across it you are probably not feeding hard enough and quite likely running too slow. If the grind is a bit off centre or one cutting lip doing all the work this sort of thing is much more likely. Despite what the experts say hand sharpening drills properly is a considerable skill needing regular practice. A good jig system is far better for normal folk. Unfortunately all the affordable ones are, objectively, imperfect in greater or lesser degree. Often "crap". Some tools should just work. Properly. Its wrong that it takes Graham Meek or someone of equivalent skills to figure out how to rework a commercial product so it does what it said on the tin.

As Mike said a pilot hole the size of the chisel point is plenty. The more of the cutting edge actually engaged in the workpiece the more stable it will be. Nibbling a mm or a few tens of thou off the edge is a recipe for disaster, probably wrecking the drill in the process. I have a, fortunately, elderly and duplicated drill with approaching half an inch from the end down undersized by 80 thou due to being forced into a pretty hard workpiece to enlarge the hole. Needs must and sacrificed for the job but the final kick to getting my Clarkson drill grinder attachment sorted and fitted as being the only think I have capable of bringing it back to size with a truly central point.

Clive

Howard Lewis17/01/2020 12:56:04
2747 forum posts
2 photos

A quick and nasty way of centering a predrilled hole under a larger drill is to lower the larger drill into the hole, and to rotate the drill, BY HAND, backwards. Once the job is centred in this way, bolt it down so that it cannot move,

Howard

Bandersnatch17/01/2020 16:43:50
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1403 forum posts
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Posted by 34046 on 17/01/2020 11:15:52:

........but the thickness of the plate was not specified.

Come to that, neither was the material. if it's brass and using a pilot drill first with regular drills, I wouldn't be too surprised at this behaviour.

petro1head17/01/2020 19:20:43
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730 forum posts
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Any thickness and mainly aluminium

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