Parallelism in vertical vice / jaws

[William AyerstParticipant @williamayerst55662]

Good morning all,

I'm a little way further on building my Stuart 10v, and one thing that has come up is that I don't really have a solid solution for bringing work away from the chuck or the rear of a vice on the vertical slide, while maintaining parallelism.

My usual method is to add packing around a part, and slide behind something of known good (ish) flatness, such as flat rod. I tap it home using a soft hammer and then tighten up the jaws. Inevitably, this means that the packing piece becomes trapped behind the work.

On the 3 and 4-jaw chucks I can't afford to leave the packing piece behind the work while the spindle is rotating, and since it may require some effort to release it may move the work piece.

On the vice in a vertical slide, I am constantly on the hunt for packing pieces which are shorter than the width of the piece being clamped, and the correct thickness to bring the work out beyond the jaws.

Any thoughts or opinions gladly taken.

[William AyerstParticipant @williamayerst55662]

[John HaineParticipant @johnhaine32865]

Just a bit of nomenclature – "rod" is generally understood to be of round cross-section, so "flat rod" is a contradiction in terms. I think you mean strip or bar?

What you need are PARALLELS which are a standard item used in milling and many other operations. Ideally they are ground flat and parallel. You can buy sets, but they would probably be too wide for a vice on the vertical slide. You can actually often use a bit of ground rod such as silver steel but getting a bit the right size could be tricky. Alternatively buy some bits of thin (say 3mm) MS strip which could be sufficiently accurate of various widths – and you could mill them down to make a set covering the various dimensions you need. IIRC Harold Hall describes making parallels on his website? It is good practice to tap the work down against the parallel AFTER tightening the jaws. In the vice it shouldn't be possible to move the packing when the jaws are tight.

If you use a packing piece behind the work in the chuck as you describe, if the jaws are properly tight it should be possible to tap it out using a small hammer and a drift to help make sure the force is in the right direction not to shift the work.

[William AyerstParticipant @williamayerst55662]

Dear John,

Flat bar is what I meant, rather than flat rod. I have found a set of parallels which are 1/2" to 7/8" – the latter of which is the very tippy tip of my vice jaws – so should be fine.

Re: drifting the packing behind the chuck – clearly I'm doing something wrong, as I had thought that was done, but ended up with one surface a couple of thou out of parallel – but I will keep practising.

As an aside if anyone knows a good way to test which side of my cylinder is perpendicular to the bored hole….

[Clive FosterParticipant @clivefoster55965]

Further to Johns post steel parallels are commonly 1/4" or more thick which makes holding thin components difficult without supplementary packing. Thinner ones can be found down to 1/8" or so thick but these are quite tricky to use as the tend to tilt. You should use the thinnest parallel that can be fitted commensurate with leaving enough msterisl above the jaws to machine.

For thinner parts normal practice is to use spring (wavy) parallels which are spring steel strips made with several waves along their length. Typically around 1/2" wide across the waves so the stand up nice and stable. When the vice is done up the waves splay out allowing the parallels to compress until the part resting on them is gripped.

As John says normal practice is to beat the part down when the vice is quite tight to ensure that it is properly seated on the parallels. Generally tightening and beating needs to be done in stages with typical home shop equipment due to accuracy limitations allowing tiny movement during the tightening process. Considerable restraint is needed when beating on thin parallels. When more on way ones as these are easily damaged.

Beating down is an acquired skill. You need a resilient striker to avoid bounce back.Historically a lead hammer was the historical weapon of choice for the professionals. The vice jaws need to be both smooth and quite tight so the part slides down and stays down. Firm hitting, hammering a nail style, is frustratingly unproductive. I use a 16 oz, nylon faced, Thor dead blow hammer held loosely and strike with a flicking motion so the haft bounces gently in my hand on strike. All the work ins don by the momentum of the head. Usually works.

Larger parts are best done with two parallels. Theoretically you should be able to get the part firmly seated on both but in practice the accuracy of affordable vices and the component being worked on is rarely good enough to get both dead tight. The slightly loose one ensures the job hasn't tilted so its still important.

Clive

Edited By Clive Foster on 22/06/2021 10:14:16

[William AyerstParticipant @williamayerst55662]

Thank you Clive – I guess I'm still not 100% on the beating process when holding a part in the chuck – the beating needs to get it flat against the packing behind – but surely if it is flat and hard up against the packing, then by nature the packing will be very tightly gripped?

I have tried to use a drift and a hammer in the past but I think this is what gently nudged my cylinder out of true when held in the 4-jaw (although of course, it could be something else entirely)

[Anonymous]

For setting work in the 4-jaw chuck I use aluminium extrusions/gauge plate/HSS toolbits as packing if the work needs to be set away from the chuck body. I never leave the packing in place when turning. Friction is not sufficient to keep it in place with any certainty even if the work is tapped into contact.

For spacing work in the machine vice I use piles of gauge plate or accurate (better than I can measure) parallels made by the late father of a friend, who was a toolmaker. If I don't need to remove the packing I will tap the work down. If the parallels need to be removed (for thru drilling for instance) I don't tap down. The lift on the vice is small anyway.

Andrew

[JasonBModerator @jasonb]

For holding thin items in the 3-jaw such as cylinder end covers I like to use my soft jaws, not so much for their concentric holding but that the back of the machined jaw provides a stop to push the work up against which is easier than juggling parallels. Also lacking the chamfered corners of most chuck jaws I can happily grip just 1mm of length which is fine if you don't get carried away with big cuts or parting off. They also allow tailstock support without the risk of pushing teh work back into the jaws which is a risk if packing has been removed.

In the vice I may only tap down 10% of the time not really finding it is needed for a lot of jobs but that will depend of individual vice lift.

I managed wit a few bits of flat BMS bar and HSS toolbits as my "parallels" for a long time before I got a commercially made set and still use them for some jobs along with the various size 1-2-3 type blocks depending on the job in hand.

 

Edited By JasonB on 22/06/2021 12:20:02

[not done it yetParticipant @notdoneityet]

Some make bespoke spacers for their chuck – such that the ‘spider’ is retained by the chuck jaws.

[Clive FosterParticipant @clivefoster55965]

In practice the amount of lift when a component is clamped in a vice is strongly dependant on how parallel the sides being gripped are.

Nicely parallel sides gripped between smooth flat jaws in a vice with no significant wear generally don't suffer from lift. Tapping down being more for verification than necessity. With my equipment basically changing the force needed to pull parallels out from "needs a tug" when the part is simply pushed down to "proper heave or use hammer and drift" when beaten down.

If your equipment is less than pristine beating down becomes more important. Now that quite decent vices can be got at pretty affordable prices there seems little point in struggling with something past its sell by date. As with chucks moving on from the "clunker that was all that could be afforded when starting out" makes life so much more pleasant.

(Looking back my biggest regret has been indulging a tendency to spread make do and mend over several "too cheap" things rather than buying one decent thing at a time and accepting that getting it all would take longer.)

If a part needs serious efforts to beat down I take a close look at how parallel the gripped sides are. It doesn't take much error before things become a bit problematical. Indeed an error sufficient to seriously reduce the amount of engagement between jaw and part on one side is frequently not readily seen by eye. Maybe reducing grip enough to risk the part moving or, worse, escaping during machining. (Shaper fans will know exactly what I mean.) Time to add soft packing or an alloy spacer and accept that this makes beating down a little harder.

Visible out of parallel demands proper action. From soft packing at least to roller one side. Repair or make a part to modify jobs can be a pain. Especially if its a casting never intended to be held that way by those sides.

Clive

[William AyerstParticipant @williamayerst55662]

Thank you all, I managed to mill some T-nuts and a few other bits without major issues, and have some parallels on the way.

[William AyerstParticipant @williamayerst55662]

I noticed that the port face of my cylinder was sloped about 10 tho on the longitudinal axis. It's my understanding this isn't a critical issue, but I decided to see if I could fix it.

I used flat packing on the bottom (entry point of boring tool) of the cylinder , and rod above it incase the cylinder top wasn't parallel. I placed a mandrel into the cylinder and pushed that hard against the vice jaws. In this arrangement, the bottom of the cylinder was parallel to the ways, and the bore was vertical.

I used a dial indicator and the vertical traverse of the vice and determined there was about 10 thou out. Clearly the cylinder top was slightly out of parallel, so when I clamped it using that side to an angle on the faceplate – instead of the cylinder bottom which was fully parallel with the bore, it was skewed.

It was a fairly straight forward job to skim that off with the slot drill, but the finish was nowhere near as good as holding it on the faceplate, as although it was flat there were some chatter marks which needed polishing out.

Just incase I'm doing something horrifically wrong on that note:

• I used a 3/8" HSS slot drill in a collet, running at the fastest lathe speed.
• The work was held with aluminium strip below and rod above in the vice, quite tightly.
• The vice was mounted to the compound vertical slide (my obvious thoughts as to a lack of rigidity)
• The carriage had the lead screw engaged and using a lead screw handwheel to advance the carriage (maybe I should have locked between each pass?). The vertical slide, and cross slide were nipped up much as I could while still being able to move them.

All the best,

Edited By William Ayerst on 23/06/2021 09:56:51

[JasonBModerator @jasonb]

I would not bother with the vice as it can introduce more errors than needed.

Set the vertical slide up with a dit to get the table parallel with the lathe axis. Put a tee nut in the middle slot and screw a stud into that. Slip cylinder over stud and with a bar or heavy "washer" and nut clamp cylinder with true face against table.

You can now machine the port face by raising/lowering the vert slide to get the cutter stepover, carriage to set depth of cut and cross slide to move the job back and forth to actually make the cut. Only cross slide should be unlocked.

Also keep "slot drills" for slots or plunge cuts, a sharp 4 flute cutter would be best for this say 1/4" stepping over 3/16" per pass.

EDIT, something like this

 

Edited By JasonB on 23/06/2021 10:27:52

[William AyerstParticipant @williamayerst55662]

At the time I was machining it, I couldn't be sure which side of the cylinder was perpendicular to the bore. I guess I could have tried both ways and seen what the DTI said…

It certainly= seems more straight forward your way!

I should probably, for my sanity re-face the cylinder top to be perpendicular to the port face and bore, and parallel with the cylinder bottom. I guess for that arrangement I DO need to use the vice?

[JasonBModerator @jasonb]

Have a look at the last page or two of the twin Victoria thread. if you don't know which end is true true to the bore then turn up an arbor to mount the cylinder on and turn the end(s) true on that as suggested by Ramon. You then have flat faces to ref the port face to.

[William AyerstParticipant @williamayerst55662]

I do now know which end is true – there's an infinitesimal difference in bore diameter that is detectable on the fit of the spigot on the cylinder end cover – though I didn't at the time. Given the only remaining skewed angle is the top of the cylinder and non functional I guess I could leave it- but I want to square it up. Any ideas on how to mount that for facing or shall I use the vice as I expect?

[JasonBModerator @jasonb]

As Above, mount on an arbor and skim the end on the lathe

[William AyerstParticipant @williamayerst55662]

Thank you Jason – do you have any link? I can't seem to find the thread…

[JasonBModerator @jasonb]

Here

[William AyerstParticipant @williamayerst55662]

Thank you Jason – triple checked and it is the cylinder top that was not perpendicular, so in this specific case I thought I would use what else I learned from this thread regarding milling rather than setting up an arbor. I wil review that thread though, it looks like it will come in very useful!

Either way I got a MUCH better result by using a 1/4" end mill with 3/16" passes and locking the cross slide:

[JasonBModerator @jasonb]

That looks OK

If you have not already seen it then DocG's earlier thread on his 10V is worth a read even if it was done with a mill as well as the lathe.

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