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Workholding on the faceplate

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Robin Graham31/10/2018 19:44:50
597 forum posts
130 photos

I'm very inexperienced with faceplate work and nervous about workholding.Do you reckon this setup will be safe?

faceplatesetup.jpg

Plan is to drill the first bar say 8mm, spot through the hole to the second then drill both in stages to say 13mm at which point I can get a boring bar in to open up the holes to 26mm.

The counterweight arrangement is a lash-up just to get an idea of what I need - it protrudes beyond the face of the workpiece, which is probably asking for trouble, but I can fix that.

I've spun the arrangement at 300rpm and nothing's come apart - my concern is more that when I start cutting, if I had a drill snag say and the packing pieces on the clamps were dislodged, all hell would break loose. Maybe I'm being over anxious, but any any comments or suggestions for better ways of holding the work would be welcome.

Robin

Emgee31/10/2018 19:57:18
1240 forum posts
210 photos

Hi Robin

You could bolt 2 pieces of flat bar using the on the centre faceplate slots, just butt the ends up to the lower plate being drilled, that would prevent any sideways movement of the workpiece.

Emgee

Robin Graham31/10/2018 20:09:17
597 forum posts
130 photos

Good plan Emgee, thanks.

Robin.

Simon Williams 331/10/2018 21:39:58
415 forum posts
67 photos

Well, safe it ain't, but serviceable - yes. I'm with you I don't like the bits sticking out beyond the periphery of the faceplate, but given that the workpiece is the size it is it don't make no never mind whether you've got one bit sticking over the edge or three. However for no better reason than to calm my nerves I'd be slightly happier if the counterweight bolt was head visible not tail visible. Anything to reduce the pokey sticky out bits.

Which brings me to the first rule of face plate work

Don't get your finger in the mangle.

Second rule is don't get anything else in the mangle either (hair, beard, sleeve, watchstrap, wedding ring etc etc.....)

Seriously though, 300 rpm - which isn't a lot if you're only drilling the pilot hole - is still enough you can't see the catch points, so you have to remember not to get close enough to get caught. It sounds obvious but make a conscious decision where the limits of the no go area are while the work is stationary and before turning if on.

Make no sudden movements - ask yourself all the time "am I still outside the danger zone if I make this next movement"? It goes without saying you must roll the work through a few revolutions to be sure nothing fouls THROUGHOUT THE LIMITS OF MOVEMENT OF THE TOOL. I find it useful to clamp a bed stop in position to stop the saddle getting too close to the headstock and potentially contacting the rotating work.

How are you going to deal with the situation where it all goes horribly wrong. Can you reach the OFF button without crossing the zone of flying debris? A footbrake is a comforting feature suddenly. Can you bring the situation back under control whilst staying right of the saddle?

Faceplate work like this gives me the heebie jeebies. If anything does shift it'll go to hell in a handcart before you can say oops. But it's very effective way of getting an accurately sized hole square to the surface.

I like Emgee's suggestion of two additional plates clamped on a diameter at right angles to the long axis of the work to be positive stops. As they are on a diameter they won't introduce an out of balance moment.

Make sure your fixings are not only tight but also clamp solid metal, you'll be fine.

Good luck Simon

PS Did I say keep your fingers out of the mangle?

Simon Williams 331/10/2018 21:47:52
415 forum posts
67 photos

And I meant to say please be sure that the packing pieces at the outer end of the two toe clamps holding the work in place are positively located to the clamp plates. They are at the periphery of the faceplate, so encounter the maximum bursting forces, and moreover if one of them does shift you're in trouble straightaway. So I wouldn't rely on the clamp force reaction/friction to hold these from spinning off the faceplate.

Best rgds Simon

Mick B131/10/2018 22:14:56
1214 forum posts
70 photos

If you have a bench drill, why not drill the 1/2" or 13mm hole with that, then set it on the faceplate (taking into account the safety measures others have proposed) and bore it to finished size as 150 - 200 instead of 300?

If you're a model engineer, remember you ain't doin' this for pay.

Edited By Mick B1 on 31/10/2018 22:15:27

IanT31/10/2018 22:46:05
1342 forum posts
137 photos

Hi Robin,

From the photo, the work piece seems to be two lengths, held apart by welded bridging pieces. So there would appear to be a gap in the middle, through which a simple strap could be passed. A bit of extra effort but a lot safer.

I find 'stepped' blocks tend to move even in static use (assuming that's what the 'packing' blocks are). I would try to avoid their use here, hence the strap suggestion. I'd try the two counter-weight straps differently too - mounting them individually but in a radial position (like a 'V' ). The inner ends could then be used to help hold the work in place. You may not get quite the same balance effect with this arrangement - but probably enough and it would be better than having those two bits sticking out. For something like this - I'd also run it as slowly as possible - a sharp drill will still work.

Hope this helps - stand well to the right as you work, just in case!

Regards,

IanT

Phil P31/10/2018 23:32:06
518 forum posts
137 photos

I usually put some thin paper between the face plate and clamps etc, they are less likely to skid.

Phil

Hopper01/11/2018 00:59:58
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3741 forum posts
76 photos

I would never use those unsecured step blocks as packing. I like to have everything on the face plate except perhaps the job itself with a bolt through it into the faceplate so it can come loose but not fling off. I would drill and tap a hole in the end of those two clamps and put a bolt through there that makes an adjustable packing piece. Set it so the head of the bolt bears on the faceplate and screw it out so it sets the clamp at the correct height (ie just a tad higher than the job).

And I would not use those two clamps with razor-like angled leading edge sticking out past the periphery as counterweights. I'll use preferably a piece or two of 2" or so round bar with a hole drilled through the middle. Painted red so you can see them swinging around in motion. If those long clamps come loose they are going to swing out under centrifugal force and foul on the bed. Could get nasty. Or a couple of spare change gears can be used as counterweights.

+1 on put a couple of pieces next to the job in the centre to stop it sliding sideways, because the clamps are a long way from where teh cutting is going on and job could move a bit quite easily.

Using bolts tapped into the clamps as packing substitutes can be seen here, in this rather precarious set up.

dscn1325.jpg

Even then, stand well clear of the line of fire. Get your self up next to the tailstock somewhere while drilling and boring etc. And keep hands well clear of the faceplate AND PROTRUSIONS area. It is all too easy to focus on the little calm area in the middle where you are drilling or boring and forget completely about the meat shredder whirling around outside it. Obviously don't out of habit go to flick away a bit of swarf or feel the vibration on the boring bar etc. Keep on hand on the tailstock or leadscrew handle and the other on the cross slide handle etc. at all times.

Edited By Hopper on 01/11/2018 01:08:46

not done it yet01/11/2018 07:42:44
3476 forum posts
15 photos

Good advice, Hopper, but do you have three hands (or do you operate a foot pedal, or similar) emergency stop?smiley

A ‘belt and braces’ approach, with awkward items on a face plate, is well advised. Particularly otherwise unrestrained step blocks - they would give way without warning with possible catastrophic results to the machine, if not the operator.

Hopper01/11/2018 08:09:09
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3741 forum posts
76 photos
Posted by not done it yet on 01/11/2018 07:42:44:

Good advice, Hopper, but do you have three hands (or do you operate a foot pedal, or similar) emergency stop?smiley

Stop button is on the bench front right below the tailstock, so within quick reach of the right hand if operator is standing in the safe position by the tailstock. No reaching past the working area to hit a switch mounted to the headstock end of the machine etc.

Hopper01/11/2018 08:13:07
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3741 forum posts
76 photos

Looking at the OP picture again, another thing I might do is move the job around so it sits between two slots, rather than right on top of one slot. This would allow clamping bolts to be right up close to the job, so in the best position for clamping force. As they are, clamping force is mediocre due to bolts being halfway between packer and job.

Andrew Johnston01/11/2018 08:14:17
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4890 forum posts
550 photos

Regarding the original picture I'd be inclined to move the balance weights in slightly, as it's not clear if they'll clear the bed. I'd also second the blocks at the front of the work to stop it twisting, to the extent that if it isn't done the work will twist.

Ho hum, I use step blocks quite a lot. Although not clear there are six clamps and step blocks holding this smokebox:

smokebox_turning.jpg

No problems so far. smile

Andrew

Kettrinboy01/11/2018 08:33:38
75 forum posts
39 photos

Just make sure before you switch on to double check that everything clears the bed and double check you've tightened all the clamp bolts and that they have enough thread engaged , 2mm of thread engagement in a nut is not enough under load, after doing loads of set ups like this over the years I had my first prang the other day , I was modifying a tool holder for my Kennet t&c grinder and had a 3/8 plug gauge pushed in a hole to depth mic to and got distracted , didn't notice it in there before I switched on and bang the plug came round hit against the bed and broke off a chunk of the cast iron boss it was in , luckily no damage to bed and part could be modified , shakes you a bit though I must admit but things like this stop you getting complacent which can happen when you do things for ages and think you know everything.

regards Geoff

John MC01/11/2018 08:38:45
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191 forum posts
26 photos

Holding work on a faceplate can be a messy business. From the safety perspective its one of those jobs that needs continuous risk assessment, that is to say "on the fly". I see no problem with "loose" packing (step) blocks, its the same force, give or take, holding them and the work. I have more concern with excessively long bolts pointing towards the tool. This photo shows, I think, an about as neat as it gets faceplate set up. Once the guard is back in place I would be happy with the set up.

John

pict0284.jpg

not done it yet01/11/2018 09:43:40
3476 forum posts
15 photos

Andrew,

6 step blocks/clamps is likely good enough for it to be considered as a ‘belt and braces’ approach. Also you will have centripetal forces in your favour, should any one of those blocks even come loose a tiny bit!

If it were six on the outside it should be good even if one step block came loose.  But I would not wish to catch it, if it did, at speed!

Edited By not done it yet on 01/11/2018 09:46:51

IanT01/11/2018 09:58:07
1342 forum posts
137 photos

I'm.with Hopper with regards to unsecured packing - reading through this thread, it has occurred to me that tapped holes in the base of my stepped blocks might be a useful mod to do when I have a few spare minutes. Through bolts would help stop them shifting and certainly prevent them flying off. I don't use them on my faceplates at the moment.

Have also had a faceplate 'balancing' fixture on my TUIT list for some time - very useful for setting this kind of thing up...

Regards,

IanT

Robin Graham02/11/2018 19:25:22
597 forum posts
130 photos

Thanks for replies - as I said, I've had next to no experience of faceplate work, so all advice is very welcome. In fact this is only the second time I've used the thing - first time workholding was solved by construction of the famous Hopper Gizmo wink

I'm not too worried about the step blocks flying off due to centrifugal force alone - at 300rpm on a 10 inch faceplate the radial acceleration at the periphery is around 12.5g (123 m/s^2) - so given that the blocks have a mass of around 45 grams, the force on them is about 5.5N, roughly the weight of a 550 gram mass - nowhere near enough to shift them all other things being equal. However I take the point that this method isn't good practice - all other things could rapidly become unequal!

I shall redesign the setup in the light of your comments - secure the packing, reduce the number of sticky-outy bits and put some further supports in as per Emgee's suggestion.

Regarding recovery from an 'incident', the lathe has a stamp bar which stops the motor/ spindle in well under a second. My reaction time in a panic situation is another matter....

Robin

not done it yet02/11/2018 20:13:47
3476 forum posts
15 photos

You are certainly right about things rapidly becoming unequal! One second @ 300rpm is five revolutions - 2 1/2 if linear deceleration under braking. More than enough time for loose items to cause damage.

Recognising things are starting to go pear-shaped is likely after the event and some of those bits are a lot more than 45g. There is a risk of high forces if the whole thing stops against the lathe bed from full speed!

Robin Graham02/11/2018 20:54:36
597 forum posts
130 photos
Posted by not done it yet on 02/11/2018 20:13:47:

You are certainly right about things rapidly becoming unequal! One second @ 300rpm is five revolutions - 2 1/2 if linear deceleration under braking. More than enough time for loose items to cause damage.

Recognising things are starting to go pear-shaped is likely after the event and some of those bits are a lot more than 45g. There is a risk of high forces if the whole thing stops against the lathe bed from full speed!

Yes, the 45g calculation was specifically concerned with the possibility of the step blocks bursting loose - obviously lots of other things could go wrong!

The new woodworking machines I have have to stop within ten seconds of hitting the stop button. How many fingers can a table saw get through in ten seconds I wonder?

Robin

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