Cutting a V groove

[Ian PParticipant @ianp]

My two penneth.

I’m not too bothered whether you want to use the existing part or make another but cutting a vee groove is only a tiny part of the problem.

The groove contains just two of the three surfaces that locate the tailstock base. Any machining, fitting or scraping must involve all three surfaces whether its the original casting or a newly made part.

Ian P

 

[Martin Shaw 1Participant @martinshaw1]

Ian

I don’t doubt your right, how do you suggest I actually cut the groove please?

Martinm

[Dave SParticipant @daves59043]

In the absence of a machine tool to do it a hacksaw and a file would work, albeit at the investment of sweat equity rather than pound notes.

I would fix the existing base however.
Your drawing shows additional guides to the edges, which are not needed and potentially over constrains the system.

[Martin Shaw 1]

On Martin Shaw 1 Said:

Ian

I don’t doubt your right, how do you suggest I actually cut the groove please?

Martinm

Without being facetious, I could only answer your question if I knew what tools you have available.

Ian P

 

 

[Martin Shaw 1Participant @martinshaw1]

First post in the thread, a milling machine with a fixed head and a non-tilting vice.

Martin

[Bo’sunParticipant @bosun58570]

Martin and myself are not the only ones to discover that the vee angle is not necessarily 90 deg. as one might expect.  Do the knowing amongst us think this is deliberate (unlikely I would suggest), or just shoddy machining?  Surely it would be more cost effective to machine to 90 deg, then you know where you are (standard tooling and all that).

No other reason for the question than pure curiosity.  That curiosity led me to check the fit of the 89ish degree vee on my WM250, and it was as near perfect as you might expect for the money.  Was I just lucky, or might the manufacturer be using “selective assembly”?

[DiogenesParticipant @diogenes]

I imagine there will be a deliberate mismatch in order to ensure contact occurs ‘somewhere on the flanks’ – otherwise there’s a danger that it will only occur at the top of the vee.

 

[Dave SParticipant @daves59043]

Somewhere, I think in Foundations of Mechanical Accuracy by Moore, there is a section about the angles of prismatic ways.

 

[Howard LewisParticipant @howardlewis46836]

Going back to the original tailstock.

Fromr the colour, it would seem to be a Sieg.

But I thought that from the C2 upwards, the lateral position of the upper half relative to the base was adjusted using two grubscrews, one each side , so that the upper part is pushed by one grubscrew and locked against the other. Mine is adjusted in this way.

Once locked against each other, tightening the clamp screw will not shift the two halves of the tailstock.

The C1, sadly, lacks the adjusting screws.  Not too long ago, I particpated in aligning one, by lightly clamping and using a G cramp to provide the lateral force align the Tailstock.

In this way, we got it aligned within 0.0005″

To do this, the chuck needs to be removed, because the bore through the chuck is smaller than the major diameter of the Morse taper in the Spindle.

Howard

[Martin Shaw 1Participant @martinshaw1]

Beyond observing the situation on my Sieg where there is no chance of contact other than on the flanks I can also see that the machining on the bottom of the tailstock is significantly worse than on the bed, there are very small contact wear patches and lots of apparently untouched surfaces. If that were the only issue then perhaps scraping might be a better option, as it is I think a more radical answer, making a new tailstock base will work better.

Martin

[Martin Shaw 1Participant @martinshaw1]

Howard

It’s an SC3 which has the horizontal locking screw visible in the pic above and the vertical screw that holds the body to the base and only tightenable by removing the whole thing from the lathe. It can be made to align but inevitably goes out after some time. Because of the slot and screw head recess in the base its range of adjustment is limited (fixed) and apart from a washer as suggested by Jason I felt a new base was the answer, I still do.

Martin

[Martin Shaw 1]

On Martin Shaw 1 Said:

Beyond observing the situation on my Sieg where there is no chance of contact other than on the flanks I can also see that the machining on the bottom of the tailstock is significantly worse than on the bed, there are very small contact wear patches and lots of apparently untouched surfaces. If that were the only issue then perhaps scraping might be a better option, as it is I think a more radical answer, making a new tailstock base will work better.

Martin

 

Out of serious interest/curiosity please could you elaborate what the other issue (or issues) that you feel warrant making a completely new tailstock base worthwhile?

Ian P

[Martin Shaw 1Participant @martinshaw1]

1. The sliding faces on the tailstock don’t appear to have much of an interference with the bed, the prismatic is       perhaps ok, the rear surface hardly at all.

2. The horizontal alignment screw doesn’t really adjust anything.

3. The vertical holding screw is tightened from underneath which requires removal of the tailstock and is limited by the recess for the screw head. This latter can be mitigated by a washer under the head but it is a bit sub optimal in my view.

4. The raised section of the base requires a pivot point for two opposing adjusting screws in the tailstock body to act against.

5. The vertical alignment needs sorted out.

6. Because it’s an interesting exercise that I feel like doing.

It is undoubtedly possible to fiddle about with the existing set up and make it work, I have done it oft enough to want a more permanent solution to the issue.

Martin

[Michael GilliganParticipant @michaelgilligan61133]

Please forgive the intrusion, Martin

You are clearly not interested in my opinion, but this is an open forum so I will express it anyway:

[6.] is an excellent reason … or it would be if you had the appropriate tools to hand.

MichaelG.

.

There … I’ve got it off my chest and done no-one any real harm

[Martin Shaw 1Participant @martinshaw1]

Thank you Michael, what are the appropriate tools please? This rather begs the original question though, how do I cut a V groove?

Martin

 

[Michael GilliganParticipant @michaelgilligan61133]

Someone else on the forum may be able to help you with that, Martin … it is quite beyond my wit to describe what you could do, with what you have.

That’s why I offered the alternative approach … which you rejected.

MichaelG.

[Martin ConnellyParticipant @martinconnelly55370]

To make a vee like this without being able to mount the part at a suitable angle, mill out the central slot, step mill the flanks, get out a file and set to work with some muscle power. The amount of filing required will depend on the step size you use to cut away the bulk of the material. If you have a profile gauge as used for copying profiles for things like coving or skirting it may be a useful guide to track initial progress.

Martin C

[bernard towersParticipant @bernardtowers37738]

Several members including myself have given you several options which one have you chosen?

[Martin Shaw 1Participant @martinshaw1]

Currently a 90 deg chamfering cutter seems the most cost effective and least amount of set up, I’ll post some pics when I have won or lost.

Martin

[old martParticipant @oldmart]

That measured 88.9 degrees sounds fishy to me. I say this because when I made the first saddle (carriage) stop for the museum’s Smart & Brown model A, I measured the angle of the prismatic vee at 88 degrees. After making the stop, I found that it did not fit very well, and rechecked the angle at the unworn end of the bed. 90 degrees, a standard angle when you think about it and I would recon that yours is also 90 degrees. The bed of our S & B is very badly worn. It is very difficult to measure such a short sided vee with precision. That makes buying a reverse dovetail cutter an attractive alternative to other methods. The great advantage in investing in a tilting vise is the extra versatility that it brings to your mill, but your budget may be limited.

This link to a new Sherwood cutter on ebay may help, it can be held in a standard collet as well as an Autolock type holder.

https://www.ebay.co.uk/itm/404288573598?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20230823115209%26meid%3D7176e27fd9de491b9754bb4914a1ae2d%26pid%3D101800%26rk%3D1%26rkt%3D1%26itm%3D404288573598%26pmt%3D0%26noa%3D1%26pg%3D4375194%26algv%3DRecentlyViewedItemsV2SignedOut&_trksid=p4375194.c101800.m5481&_trkparms=parentrq%3A8026fcda18d0adbaedfcd495ffff2d46%7Cpageci%3A06867133-c530-11ee-beb8-b65f927858cc%7Ciid%3A1%7Cvlpname%3Avlp_homepage

[old martParticipant @oldmart]

I wonder if you have thought about the method of getting the vee at the exact same height and angle as the flat part at the rear of the bed? I would not like to have to tackle that problem. Is there any way that the base can be salvaged and a better interface between the halves involving a third piece of metal made room for by milling back the top half of the tailstock?

You will certainly need a mag base with a lever style indicator to check and set the alignments of everything.

I recently replaced the rather poorly designed Atlas 12 x 24 tailstock with a NOS lever locking one of probably Chinese origin. This involved a new base for the tailstock to raise it up but the design was much simpler than yours. The Atlas bed is non prismatic like a Myford and the base only needed an adjustable gib to get it fitting well. The alignment is tricky. first the quill has to be exactly the height of the spindle and in a horizontal plane. Then the quill has to be aligned in plan view and there must be no deviation throughout the quill stroke. I used a MT2 test bar in the quill to get the alignment spot on.

The weakness in your tailstock seems to me to be not the base to bed, but the joint between the base and body. Is there any way you could improve the security between the parts?

[Martin Shaw 1]

On Martin Shaw 1 Said:

Howard

It’s an SC3 which has the horizontal locking screw visible in the pic above and the vertical screw that holds the body to the base and only tightenable by removing the whole thing from the lathe. It can be made to align but inevitably goes out after some time. Because of the slot and screw head recess in the base its range of adjustment is limited (fixed) and apart from a washer as suggested by Jason I felt a new base was the answer, I still do.

Martin

I respect your wish to make a new item, but let me tell you what I did.

I was able to obtain a lever lock tailstock someone else didn’t need -John Stevenson had converted a machine that didn’t need a tailstock (I think it was for making fishing floats!

This was slightly taller than mine for some reason and I was able to machine the back and forth joint to get a much better fit and finish with perfect alignment with the lathe axis. Mods included a brass gib as well as sorting out the locking mechanism, so it could be moved and locked without going out of alignment.

Tests with blue showed the vee and sliding face to be good fits. I may or may not have done a tiny bit of scraping, I don’t recall.

If I was in your position I would either make or buy a single point cutter to make the groove and finish by scraping it to fit the bed – note this requires that the flat sliding surface at the rear is sorted too, or I would cut off the top of the  block, and make a new cross-motion arrangement and add a better locking arrangement (on my original tailstock I built a quick release, but it wasn’t as good as the stock one).

 

 

[Neil WyattModerator @neilwyatt]

There may be some useful stuff in this which I wrote a long time ago:

The Tailstock
A Tailstock Lever Clamp
One of the most annoying and time-wasting features of mini-lathes is the reliance on a simple bolt clamp to fix the tailstock. Reliable, solid and very slow. Nothing would speed up repetitive tailstock operations more than a quick-release mechanism for the tailstock. I thought out several possible solutions, but never got “a round tuit”. While idly sifting through one of my ‘bits boxes’, I turned up a redundant cycle quick release. If this can hold a cycle wheel solid as its (terrified) 190lb rider plunges down a steep, bumpy track at 40 mph, then surely it can clamp my tailstock, methought. After prising out a circlip, a simple eccentric cam arrangement was revealed.

The lazy solution would have been to shorten the quick release spindle, re-thread the end and run it through a plate beneath the bedways, but I wanted a longer clamp lever that would also be out of the way behind the tailstock. I decided to follow the principle of the clamp, but making it rather more robust. The device consists of a ‘cambolt’ which a lever turns in a ‘camnut’ drawing it into an outer sleeve. The cambolt pulls on a spindle threaded into a replacement baseplate, clamping the tailstock to the bed between the baseplate and the sleeve. To place the lever at the back of the tailstock, the cambolt is extended through a ½” hole in the tailstock web. This design has advantages over some other designs as all the clamping force is directly on the base of the tailstock casting.

The dimensions in the drawing will give a lift of 4mm if the cam is turned a full 180º. In practice, 90-100º can be achieved, giving about 2mm lift. This is sufficient to allow for variations in the thickness of the webs on the lathe bed casting along its length and gives adequate grip.

I can honestly say that this single adaptation has made a huge difference to the pleasure I get from my lathe. Any sequence of repeated tailstock operations becomes quick and easy. Most usefully, when drilling a deep hole one can release the tailstock and pull the drill out to clear swarf faster than one can wind it in and out with the handwheel.

Camnut
The size of this component is critical. The 8mm hole, together with the play of the head of the nut in the sleeve, is just enough to ensure that the cambolt will not jam it in the sleeve.

The camnut must be made from hardened and tempered silver steel or high tensile alloy. It will be under considerable tension, and it needs to be tough. The lever for clamping a cycle wheel is only half the length of the one I made for my tailstock, yet it clamps with sufficient force to withstand some really large shock loads. You should only need modest force on the tailstock lever to lock the tailstock solid.

I tempered my original camnut to dark straw, thinking this would be sufficient. This appeared to work, but the day after I fitted it I heard a sudden crack from the tailstock, and it had fractured. I was not even using the lathe at the time. A salutary reminder that hardness alone is no substitute for toughness. I made a replacement, but instead tempered it to a blue ‘spring’ temper. The new version has served for nearly a year without incident, so I recommend using this temper.

Spindle
Depending on exactly how you set it up, the lever clamp has about 2mm of travel for a 90° movement of the lever. This is not a lot, so adjustment is critical, and is provided by the combination of an M6 and M8 thread on the pillar. These have pitches of 1mm and 1.25mm respectively. By turning both ends of the assembly by one turn, the overall length will change by 0.25mm. Alternative and simpler arrangements would be to have a one-piece pillar, but this would only allow adjustment in steps of 0.5mm. A spindle passed through an unthreaded hole in the clamp plate could be used, but this would require locked pairs of nuts on both sides of the plate.

 

Cambolt
I made the cambolt from high tensile steel hexagon stock. Mild steel would probably wear too quickly in this application. You could use silver steel but, if you do, temper it to a different hardness to the camnut.

It doesn’t matter if you make the cambolt from hex or bar stock, though the latter will be a little harder to hold and drill for the handle. Start by turning down the 3/8” diameter (this section passes through the hole in the tailstock). Now turn the 9mm section over length, to provide the material for the cam, and the 5mm section at the same setting, so they are concentric. Thread the end of the latter M5. You now need to turn the cam, which requires offsetting the work by 2mm. This is most easily done using a four-jaw chuck, but you may also do this by packing one jaw of a three-jaw chuck. Align a suitable mounted point as a gauge (or even the tip of a tool), close to the joint between the 9mm and 5mm sections. Adjust the work so that the extremes of eccentricity are alternately at the 5mm and 9mm diameters. Now turn down a section of the 9mm diameter to 7mm, taking fine cuts to ensure the work does not slip.

Mill or file a flat for mounting the handle. This should be opposite the ‘high spot’ of the cam, so that pressing the lever down will raise the cam and tighten the clamp and that the maximum movement will occur as the lever passes the horizontal. The dimensions given for the lever handle are intended to give a good match for the existing tailstock and toolholder levers.

On final assembly the cambolt should be retained in place by a washer and two locknuts, or a single nylock nut.

Sleeve
I admit it, I have never got around to replacing the original cycle clamp sleeve, it works fine, though it does look a little out of place. The item in the drawing will do the same job, but take care to ensure that the two holes are exactly in line with each other and the centreline of the sleeve. As the clamp locks the camnut will move from side to side within the sleeve, not just up and down. Significant clearance is needed, more than just a sloppy fit, or the clamp will appear to lock without gripping the lathe bed.

Lever Handle
This is a simple design, it could be even simpler, but this shape blends nicely with the other screw levers on the machine, and I have copied it on other devices I have made. It isn’t as pretty as Quorn-style ball handles, but they are neat, quick to make and possible more comfortable to use.

You could argue that the lever is too long, as it allows tremendous force to be applied, and can foul the tailstock barrel locking lever. In practice I only turn the latter lever when the tailstock is locked, so that isn’t a problem. As to the mechanical advantage of along lever, only a few pounds of pressure will lock the tailstock securely. This is part of the pleasure of using the clamp, but one must take care not to over do it.

I made an attempt to black the lever by heating it and dropping it in clean oil. I don’t think it was clean enough, as the result was rather patchy, but even so it is not showing any signs of corrosion from my sweaty palms!

Baseplate
I made a plate that was rather thicker than the original, as that showed signs of distortion. It also meant I had the original as a spare, should the replacement fail! Note that it is offset in order to clear webs in the lathe bed, I suspect the offset will vary between machines, so check your dimensions from the original plate.

Tailstock Modification
In order to mount the handle at the back of the tailstock, it is necessary to make a hole in its web. The exact location for the hole should be marked on the web with the other components in position; take care to ensure there will be space around the cambolt to so it can move up and down. I opened the hole up in two stages, drilling the initial hole, then plunging in a slot drill to open it to full diameter. After carrying out this operation it is important to check that the tailstock is still properly aligned.

Assembly
It can be tricky to put the whole thing together, especially as you may need to make fine adjustments to get the clamp to lock along the whole length of the lathe bed. An added complication may result if the holes in the upper and lower parts of your tailstock do not align well. In this case you may need to thread the upper spindle in from above, as the camnut may not fit through the holes. Once you have the correct length I suggest using threadlock to keep the two parts of the spindle together, the rest of the assembly will be kept aligned as they cannot rotate once the cambolt is in position. Don’t forget to put a little grease on the cam on final assembly.

[Martin Shaw 1Participant @martinshaw1]

My thanks to Old Mart and Neil for the most helpful posts with lots of information for me to absorb and think through, I am grateful for the time and effort.

Martin

[old martParticipant @oldmart]

If you separate the halves of the tailstock and rub the base along the lathe bed to show up the high spots, they could be scraped back locally with a small scraper made from a flat needle file. The end of the file could have its teeth rubbed down for the end 5mm and the flat end rubbed for a slightly off square and curved cutting tip. Wet and dry paper on a flat surface would only take minutes with a little file. When you have a better fit, and perfect is not required, then you can set it on the bed nice and clean and check the squareness of the left hand face that lines up the top half of the tailstock. A lever indicator on a mag base sitting on the cross slide as it is run will give you either dead square or a close approximation of the error from one side to the other. A lever indicator with its original length stylus set at close to right angles to the surface to be checked will give the least error. Any error measured across the part can be noted and the base set on the mill bed using the indicator to reproduce the error. When the milling cutter removes just enough metal to clean up the whole width, you should have a better squareness.

If you do not intend to offset the tailstock to taper turn between centres,it might be possible to fix the top and bottom together more securely once you get proper alignment. There are adjustable taper turning devices which fit into the Morse taper of the tailstock quill rather than having to move the halves of the tailstock. I would never taper turn between centers, but having a taper turning facility on the Smart & Brown model A, I am somewhat spoilt.

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