How not to use a clamp

I've watched a few of Adès videos, he seems like a genuine nice guy who I don't think would ever intentionally want to encourage anyone to do anything that would result in someone getting hurt, having considered making similar videos, this kind of scrutiny makes me pause for thought.

Im puzzled what abuse the bed has by not putting strips under the clamps? we were never taught to do it at college & both my mill beds show no sign of abuse in all the years of use,perhaps a larger footprint strip if you're clamping over the tee slot maybe.

Graham.

I can see why you would want to put something under the clamps / blocks as most of the cheaper blocks don't have very good surfaces and could easily mark nicely ground surfaces. This is not a practice that I do but thinking about it , I will at the very least grind the bottom of the blocks and will probably find something better to place under them. That said my milling machine table has the all the signs of something used as a work horse in industry (it was like that when I got it) and probably wont look any better for it.

Regards.

David.

Man that does, criticised by those that can't...

Jom

First let me say I am, like others quite ok with Ade’s clamping for what he is doing, and he makes some entertaining videos. I think one of the problems of the force of the heel of the clamp is the softness of some mill tables, not usually a problem with industrial hardened tables, excessive forces will indent a small heel into the table surface. No one has moaned yet about the clamp stud and nut, no spherical washer below the nut so bending the stud assembly. As I say you do what you need to do in the privacy of your own workshop to get the job done with what is at hand.

They look like penn nuts to me Howard.

Emgee

Just read through this thread for the first time - some interesting comments but as a long time machinist....

The image shows right and wrong IMO - clamp to the left correctly set up - clamp to the right not so. If, as it appears to me, that the clamp is resting on the very thin edge of the packing block then if the top of the packing block is higher than the job then the packing block can rock away from the clamp very easily. It doesn't matter (in my book) whether or not the job is only a simple one with or without side forces if the clamp lets go because it is not placed as the design calls for and the job gets spoilt because of it it's a no brainer.

It really is sensible in using the clamps shown as designed ie with some if not all of the teeth engaged or a smaller block reversed and used as conventional packing. And of course the further one is into the operations the more there is to lose.

There should be no need for packing beneath packing to prevent damage to the table - granted I've seen some pretty disfigured tables over the years but those are always a culmination of many users who exhibit little care for the machine but if it's your own it, save an accident, heaven forbid, it should be quite unmarked and not damaged by sensible clamping.

Tug

Why is it you always see the mistakes after posting 

Edited By Ramon Wilson on 22/01/2021 23:11:51

Edited By Ramon Wilson on 22/01/2021 23:13:04

FWIW, I opened a copy of the image in PSP, played with brightness/contrast and zoomed in. It appears to me that one step of each (clamp and packing-block) is engaged.

From what I have seen, there are many far worse examples of machine shop misinformation on YouTube, including some of the very popular "big names" down to very beginners setting themselves up as gurus. I wouldn't worry too much about this minor infringement.

During my apprenticeship I was shown that interposing thin paper between the table and workpiece and or clamps go a long way to protect the table and also provide better grip/contact during clamping without overtighting and possible distortion or damage to table and or workpiece.

Regards to all

Derek

Posted by derek hall 1 on 23/01/2021 05:02:03:

During my apprenticeship I was shown that interposing thin paper between the table and workpiece and or clamps go a long way to protect the table and also provide better grip/contact during clamping without overtighting and possible distortion or damage to table and or workpiece.

Regards to all

Derek

Absolutely plus one for that advice Derek - the extra grip provided by a simple sheet of paper is out of all proportion to it's simplicity.

Peter, The image is dark but I accept what you are saying - my thoughts still stand though - inadequate or inefficient clamping is always a very easy way to ruin a part.

I may have mentioned this before but it's worth repeating - in my very early days of ME I had a Stuart handpump casting (poorly) clamped to a face plate set up on a ML7. Within a millisecond of the tool touching on it left the faceplate over my left shoulder and embedded its corner into the wood surround of the door behind me. The clamps rattling and frapping whilst my brain sorted frantically how to stop the lathe!

IMHO most clamps - particularly the commercial sets as in the image are way to large for most home bench milling machines.

I use a combination of 6mm cap head screws of varying lengths for the bolts which are more than adequate for most model sized workpieces. Packing is mainly of varying lengths turned from 1" dia mild steel. These are drilled through 6.5mm and counter bored. Ideal for use on faceplate set ups when they can be used not only as packing but also as balance weights

That's just to show my approach - not how to teach granny I assure you

Regards - Tug

Tug, I'm even a bit more cautious than yourself with clamps spinning on the faceplate. I would have a bolt and nut through each of those round packers into the T slot behind just to make sure they were secured if the clamps came loose. Just to make sure that nothing can fly off if it comes loose, except maybe the job itself if unavoidable.

Sounds like petty criticism for the sake of it.

Oh I don't know Bo'sun, I guess it's a fair point to comment on but can say with confidence that as cautious as I am Hopper I've not had a problem with this particular set up ie using the round packing as shown. I do sometimes bolt the packing in place if there is more than one part to do as it eases the setting up but It's not always possible to get slot, packing and clamp in line to do so. When making the diesels I used the faceplate a lot.

I like using this system because of it's 'size' - the bolts have far more tensile strength for what is required and the packing is easy to stack - just dropping a bolt through three pieces keeps them roughly in line. I have a minimal selection of clamps, mostly home made and the four small ones kept from my very first lathe, a Unimat which get frequent use and particularly on the rotary table.

Like I say - I'm not teaching granny but if it does help someone new to machining it's worth saying I guess

Regards - Tug

Oh dear, so many "BUTS". My mentors would probably have heeded the advise had it been given BEFORE many of them lost bits if their anatomy to retrospectively teach me not to loose mine.

"Them as can do and them as can't teach" Yep, brilliant philosophy, but let's not forget, SOME can do both, gained from years of the former while retaining most of their soft bits intact.

Regards Ian.

Martin's example isn't the worst I've seen on the web, but that's good because it got us talking. Subtle mistakes are often more educational than the bleeding obvious! The clamping error is an easy to miss operator mistook. As it's easily fixed, we benefit from it.

Being a self-taught machinist I rely on threads like this to pick up tips and best practice. Derek's mention of thin paper is a cracking example! Obvious now he's said it, but I would never have thought of improving grip with paper myself.

Dave

And while not relevant to this post the last two parts muttered under our breath as students on a 4 year B.Ed course were and those that can't teach, teach teachers, and those that can't teach teachers teach on philosophy of education courses.

Totally slanderous of course ......

Yes, paper or thin card for providing a slightly keyed and imperfection-absorbing surface is a great idea.

The only cautionary note is that, depending on how dry the air in your workshop is, if you leave the set-up in situ for any length of time, you may see rust spots on your table when you dismantle things. Even oiling the paper first didn't help me avoid these rust spots when some clamps were left in situ holding down an angle vice for about six weeks.

Maybe there is something better than paper for longer term set-ups. Thin Theraband is an idea [haven't tried it yet], but it might well wrinkle uncontrollably as you tighten things down.

Well I must admit I've never considered that someone would leave a set up on paper for six weeks but I appreciate we can't all be in our workshops on a daily basis

Oiling it would - I would think - defeat the object of improving grip. Using paper as such is nothing new - it has been around for a long long time. It's particularly useful when clamping is a bit marginal or in a vice to improve grip on material that wont take excessive pressure - eg a gunmetal casting.

Whilst the cutting forces weren't excessive I really was expecting this operation to be fraught with moving but the paper prevented it with only a central bolt holding on the lower half of the flywheel. It's never a good idea to clamp with a single bolt at any time but it was needs must on this occasion.

Saw went through on one pass at depth shown, job slackened and turned and op repeated until the two halves were separated

I don't claim nor ever have to be a 'teacher' but I learnt from others passing things on - to me this is a way of repaying that knowledge.

No one way is ever right - but some are definitely wrong so I hope this is seen as trying to be helpful to those who don't have the vast experience that some have.

Tug

Tug, I agree that the commercial clamping sets are far too big for small mills; they can be a real struggle to set in place and work around. Making a set based around M6 fasteners with stackable packing pieces and a consumable sub-table has been on my list for some time. I also intend to make matching T-nuts for the faceplate slots, but as I've only used it once in 18 years that's a very low priority!

As for teaching, it's a depressingly under rated skill. Good teaching takes training, practice and an understanding of the subject - I suspect those who trot out the phrase those who can't, teach have never tried it. There a lots of people who can do, but are hopeless at teaching. That teaching also develops your skills as you do so is so well known that it has a name - The Mentor effect; having to think through what you're doing and why so you can explain it is very useful. I found being asked to help train our new bell-ringers is the biggest improvement I've made to my own ringing.