Work Holding for simpletons

[Terry KirkupParticipant @terrykirkup37827]

Hello again folks, I seek your advice once more.

I know this is ugly but is it good or bad? And should I get a bigger vise (this one 4&quot?

70mm of 50mm aluminium bar drilled 22mm (tip of 22mm blacksmith's drill just visible on left). I've made a few of these items previously but used boring tools to dig them out from 13mm drilled holes, so the bar was held in the 4 jaw chuck. Took me absolutely ages. I couldn't stop the lathe juddering or the boring bars (in tailstock 50mm boring tool holder) nodding madly! I did try to balance the chuck with weights, hardly made a difference though.

And one more question to our friendly experts – can I use the same method to open a hole up to 30mm in the same material, drill held by ER32 hex collet block in 3 jaw chuck or is my life in danger?

[Terry KirkupParticipant @terrykirkup37827]

Just want to know how daft I am.

[JasonBModerator @jasonb]

Maybe not ideal but when needs must. I have made up a couple of clamping bars from 1/2 x 1" steel that are drilled to suit the tee slot spacings in the mill and another the lathe's cross slide slots that are good for jobs like this.

I'd just hold the blacksmiths drill in the lathe's 3-jaw chuck and not bother with teh ER block & collet.

[old martParticipant @oldmart]

I think you are lucky to be alive.

What size is your lathe and do you have a four jaw independent chuck?

[HOWARDTParticipant @howardt]

Main problem you have is there is nothing directly behind the area you are cutting. You are imparting a turning motion on the fixture. Also the clamp studs have a bending force imparted. All bad with such a large intended bore.

Place the part on the angle plate so that the intended hole is above it. Make a strap clamp to hold the part, ideally one either side of the hole. A strip clamp can be a bar with two holes in it spaced as per the tee slots. Ideally as well put a fixed stop against either end of the bar to stop it moving sideways under cut.

If using a vice it would need to be big to have sufficient jaw depth to hold the part in at least one see. My suggestion would be to hold as above rather than in a vice.

[Ady1Participant @ady1]

Once you open the hole out to 20mm or so you can flycut it with a chunky boring bar whirring in the 3 jaw

I have used a 16mm bar to 45mm

Grind up a suitable cutter, will go from 20 to 40mm approx

Grind a 2nd bigger one for a bigger hole

extend the cutter a teeny bit after each pass

When you get it right it makes a nice swooshy noise as it carves a hole through the workpiece and the swarf flies away

GL

Edited By Ady1 on 02/10/2020 15:59:40

[Mick B1Participant @mickb1]

It's nasty for 3 reasons:

i) The clamping nut is unable to act straight onto the washer and clamp across its full diameter. It would be hugely better to add an equivalent thickness of support to the clamp on the opposite side of the stud, so as to level the clamp square to the stud or thereabouts, and even out the force the nut can exert.

ii) The clamps should be as close as possible to the site where machining force will be applied. If the hole shown only just clears the vertical plate, the clamps should be closer to it.

iii) It's also undesirable to sidestress the T-nuts and studs like that. Even if there are no dramatic events, there'll likely be some damage to reduce their future usefulness.

For opening up, I'd use a boring head with light cuts or, failing that, a collet- or chuck-held boring bar with a manually-set toolbit to open up to about 29,6 before using the 30 drill as a reamer. Light cuts, slow feed, and sort out the clamping first.

[Martin ConnellyParticipant @martinconnelly55370]

It the top stud goes up a little more or the bottom stud goes down a little more you have a loose setup. Never a good idea. Put a support on the opposite side of the studs to keep the clamps level so that there is no way for the studs to go loose. A simple machinists jack (see the one made by Dr_DMJN in this thread Stuart 10V Build Log for a simple design) will allow a good solid clamping action. Alternatively have a metal bar across the workpiece with holes for both the studs.

I agree with old mart, you were very lucky – this time.

Martin C

[Dave HalfordParticipant @davehalford22513]

The clamps are dire, the work is trying to twist away from the drill.

I would mount the angle plate in line with the drill.

Cut a chunk of 1/2" MDF to suit the bolts between the rod and the angle plate.

Use a single clamp plate as Jason suggests to hold it all.

Stop drilling when you see MDF in the swarf

[Henry BrownParticipant @henrybrown95529]

If I had to do that, a very non-preferred way for me, as I'd have used my mill. If I had to do it this way I'd have got a suitable piece of square or rectangular bar (that will have negligible bend when clamped) and drilled two holes through to match the pitch of the top an bottom T slots that will take your studding. That would be for a one off though and it sounds like you are doing this on a regular basis. As Jason said needs must sometimes but this is far from ideal and I certainly wouldn't try opening it up to 30mm with a drill.

[Martin ConnellyParticipant @martinconnelly55370]

Rear support of the clamp bar using a clamping set hex coupler and stud as a simple jack. Keeping the clamp close to level is important to avoid side forces on the stud which will encourage it to go down the gradient and so loosen.

Martin C

[Howard LewisParticipant @howardlewis46836]

Purely my preferences, but if possible I would hold the work in the 4 jaw, with the drill in a chuck in the tailstock.

This should be the most rigid way of holding the work, and least likely to move under the cutting forces.

The method shown is not the most rigid. Martin Connelly's method is better, if you must, since it provides increased clamping forces.. (Don't like the steeply inclined clamps! )

That's my 2 p

Howard

[Robert ButlerParticipant @robertbutler92161]

Not to mention stress on the T slots with possible dire consequences!!!!!!!!!!!!!!!!!! Robert Butler

[Nigel Graham 2Participant @nigelgraham2]

Martin –

I realise your photo is simply to illustrate the method but with respect I would –

– put a nut on the top end of the jacking stud to increase the bearing surface a bit, and avoid the risk of harming the end turn of the thread; and

– put the jack further back so the mechanical advantage is in favour of the jack holding the work-piece rather than vice-versa. (It's about 2:1 against in the picture.)

[Terry KirkupParticipant @terrykirkup37827]

Well, I retreat red faced, but fully expected! Thank you all for your input here, I will make better arrangements for the 30mm cut.

And Howard, just one thing. My lathe is Warco WM290V. With the workpiece, in fact any workpiece, mounted to the chuck, there's no way these fairly short blacksmiths drill will reach their target, even with the tailstock at its maximum 80mm extension where anything wobbles at the best of times. The cross slide is just far too wide for that, creating a huge intervening gap, so I guess I'll stay with chuck mounted tools for now. Unless I can hold the drills in the toolpost somehow, a wedge type BXA?

[JasonBModerator @jasonb]

That's odd Terry as My 280 allows me to drill right upto the chuck or faceplate. Though no leads screw cover on my early one.

[Tony Pratt 1Participant @tonypratt1]

I also find that with my Warco 290V you can't get the tailstock close to the work, the DRO fixed to the cross slide RH side makes matters worse, I need to look into that sometime.

Tony

[not done it yetParticipant @notdoneityet]

I was aghast at that holding solution! If I were holding something like that, I would acquire, or make, a couple of Vee blocks on which to mount the part, then have a couple of straps to secure the part in position. That would (hopefully allow the machining to be carried out closer to the centre of the holding device and permit cutting through the pats without cutting into the holding kit.

Holding solutions can often take longer to sort out than the actual machining of the article.

[larry phelan 1Participant @larryphelan1]

Delighted to have seen that setup !

And I thought my efforts were bad !

However, I do admire a brave man., but I really think a 4 jaw chuck would be a better idea.

I can just picture that piece taking off at a rates of knots when you start cutting

[Brian WoodParticipant @brianwood45127]

I have another suggestion and that is bolt the 4J chuck to the angle plate and hold the job that way.

I noted that the next hole will be 30 mm diameter which will be significantly more demanding on the workholding needed

Regards Brian

[Neil WyattModerator @neilwyatt]

Sometimes it's needs must as the devil drives…

In which cases light cuts, gentle feeds and an abundance of caution are in order. Think 'what's the worst that could happen'?

In this case poor finish or a broken cutter, I got away with just the first, which didn't really matter as I was just opening up the slots.

[Martin ConnellyParticipant @martinconnelly55370]

Nigel, you are correct it is just for an example, I have proper machine jacks, Wixroyd 15000.W0050 jacks and step blocks for when I do this sort of clamping. This was showing the minimum you could do to fix the issue and also the space behind the studs in the original photo was taken into account with the example shown. My preference would have been a good sturdy bar with holes for the studs going across the workpiece as has been mentioned above given the space available.

There is one of these jacks in this photo from 2017 and step blocks supporting the back of the strap clamps from the kit on the wall behind the mill.

Martin C

[Terry KirkupParticipant @terrykirkup37827]

Yet again I must thank you all for the input. As bad as it looked I assure you it was solidly held and as Neil Wyatt said "light cuts, gentle feeds and an abundance of caution" are exactly what I used. I'm still alive enough to type this but haven't tried the big hole yet. I think I may invest in an angle plate and vise a bit more up to the job. That's really what my clamping kit needs for a better match up. The tee bolts I used in the pic were not part of the kit which is much meatier but the slots in my 4" vise are tiny. Christmas is coming so I'll see what that brings.

Meantime I have to say how surprisingly excellent blacksmiths drills are, at least on aluminium.

Tony Pratt if you ever get that DRO issue sorted please post your solution on here, with luck I'll still be around to see it.

[not done it yetParticipant @notdoneityet]

Terry,

Had it come loose, you may well have destroyed the T-slots on one side or the other, before it came to a stop, or was launched in your direction. It is definitely worth asking before starting the job if you are not 100% sure that you can take (normal) robust cuts. Someone will almost certainly have needed to securely hold down something similar.

For a start it might save you scrapping an item or the tooling. It would not be the first I have scrapped a part because it moved while machining…

[HopperParticipant @hopper]

Posted by Terry Kirkup on 02/10/2020 15:37:22:…

 

…. I couldn't stop the lathe juddering or the boring bars (in tailstock 50mm boring tool holder) nodding madly! ,,,

A

That;s your problem right there. Boring heads are not designed to be used in the tailstock and tailstocks are not designed to hold a boring head. You end up with waaaaaay too much tool overhang and the essential little bit of slop between tailstock barrel and body becomes amplified by the distance/leverage and will move about all over the place. The other problem with today's cheapo Chinese boring heads is the supplied carbide boring tools are useless until they have been correctly reground on a green grit grinding wheel.

If you can hold the job securely in your four jaw chuck, the best way to bore the hole after drilling is with a stout boring bar held in the toolpost and fed along by the carriage. For a 30mm-plus hole you should be able to use a boring bar with a nice solid half-inch diameter or so shank. It should stick out of the toolpost just a tad more than the depth to be bored.

For the drilling first, start with a centre drill then a pilot drill of maybe 5/16" or 3/8" diameter then your large drill, then bore. It may help with the "juddering" if you machine a flat on the job same diameter as the finished hole so your drills have a steady flat surface to get started on. But it shouldnt really be necessary.

You need to get yourself a good book on beginner level lathe work, such as The Amateur's Lathe by LH Sparey to get the basics down pat. Forums and YouTube are helpful but no substitute.

 

 

Edited By Hopper on 06/10/2020 02:02:46

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