Cutting a V groove

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Cutting a V groove

This topic has 52 replies, 20 voices, and was last updated 9 February 2024 at 21:48 by old mart.

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31 January 2024 at 15:34 #711022
Martin Shaw 1
Participant
@martinshaw1
After an extended period recovering from a fractured hip and the ME website turning itself inside out I am at long last allowed back into the workshop. One of the many tasks is to sort out the lathe tailstock and whilst the general plan is clear in my head I have a slight problem, how do I replicate the V groove as in the bottom of the existing tailstock base. My mill is a fixed head type and I don’t possess a tilting vice so without spending a fortune, any suggestions please?

Thanks

Martin
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31 January 2024 at 17:19 #711032
Fulmen
Participant
@fulmen
Perhaps a sine bar could be useful here?
31 January 2024 at 17:37 #711036
Peter Cook 6
Participant
@petercook6
If you have a small(ish) toolmakers vice you could clamp it in your main vice at the appropriate angle using packing or a machinists jack to prevent movement, and clamp the material to be milled in that.
31 January 2024 at 17:43 #711038
bernard towers
Participant
@bernardtowers37738
In the past I have stepped the V with varying sized mills and finished off with a multi tooth countersink of the right angle
31 January 2024 at 18:19 #711046
JasonB
Moderator
@jasonb
I’d fix it flat to the mill table and do the central flat bottomed slot. Then use a couple of angle plates to set the base at an angle so it can be milled with the side of a milling cutter for one face and the end of the cutter for the other.

Other option would be a chamfer mill then it can all be done at one setting flat on the mill table.
31 January 2024 at 18:31 #711047
Peter Tucker
Participant
@petertucker86088
When I wish to machine a V in a piece of work I have a short piece of large heavy section equilateral angle iron which I bolt to the machine table with the legs down and the right-angle corner up. The work is then clamped to one leg of the angle (making sure everything is square and parallel) and a standard milling cutter is used to make the V.

Hope this helps.

Peter.
31 January 2024 at 18:52 #711048
DC31k
Participant
@dc31k
On 31 January 2024 at 18:19 JasonB Said:

Other option would be a chamfer mill

It is a bit difficult to judge the scale, but looking at the length of the sloping side, it would need to be quite a large diameter chamfer mill (and hence quite a large price).

It would be a little more difficult (i.e. you’d need to be quite careful or it would mill a step) with a smaller diameter mill finishing in more than one pass.

As a lot of the material could be removed on the flat, to leave it like a staircase, giving the finishing cutter an easier time, and as it might well be cast iron, a 90 degree router cutter might be an economic choice for the job.
31 January 2024 at 19:48 #711053
Diogenes
Participant
@diogenes
..do you live near anyone with a shaper..?
31 January 2024 at 20:31 #711056
Andrew Tinsley
Participant
@andrewtinsley63637
Yes an ideal job for a shaper!

Andrew.
31 January 2024 at 20:33 #711057
Fulmen
Participant
@fulmen
Can you make a single flute cutter?
31 January 2024 at 21:04 #711059
peak4
Participant
@peak4
First job might be to measure the included angle of the prismatic section of the lathe bed.
I assume there must be an issue with the underneath of the tailstock mounting, so measuring the bed might be better than measuring the tailstock groove.

Bill
1 February 2024 at 07:53 #711082
David George 1
Participant
@davidgeorge1
What is the problem with the tailstock? Is the V wrong shape, size, or flatness. is it possible to keep shape and alter top face or holes etc instead.

David
1 February 2024 at 08:57 #711087
Bo’sun
Participant
@bosun58570
On 31 January 2024 at 21:04 peak4 Said:

First job might be to measure the included angle of the prismatic section of the lathe bed.
I assume there must be an issue with the underneath of the tailstock mounting, so measuring the bed might be better than measuring the tailstock groove.

Bill

Good morning Martin,

David has just reminded me. Yes, check the angle of the vee before doing any machining. When I made a carriage stop for my WM250, the vee was not 90 deg. as you might have expected. It was more like 89 deg. if I remember rightly.
1 February 2024 at 10:04 #711091
Mike Hurley
Participant
@mikehurley60381
Machine Mart have got the Clarke CTV25B 2½” Tilting Vice on offer at the moment for around £8

They’re a bit ‘basic’ but rugged, and at that price may solve your problem.

regards Mike
1 February 2024 at 10:12 #711092
Martin Shaw 1
Participant
@martinshaw1
Thanks very much for the useful suggestions, it does I suppose come down to how much I wish to spend on what is essentially a one off job, and availability. I don’t have access to a suitable sized shaper, nor do I know how to make a single flute cutter, which in honesty will take longer than the actual job and will I suspect be frustrating.

The problem is with how the existing base is held to the main body, a screw through a slot with a recess for a cap screw head that isnt quite lined up, so forcing the horizontal alignment out. This becomes apparent when using a small centre drill that sometimes describes an eccentric circle rather than a centre, fortunately this hasn’t happened on anything complex and it can usually be pulled back.

It is possible to see from the wear patterns that the base doesn’t sit down on the bed fully flat, especially at the rear and only uses less than half of the rear bed for support, for no good reason I can fathom. I cannot justify the cost of a sine bar and slip gauge set for a one off, so its probably going to be an angled parallel and an ordinary cutter or a 90deg chamfer cutter, the latter is perhaps the most convenient and indeed it will be in cast iron, I’ll take some measurements later and post the results.

Martin
1 February 2024 at 10:19 #711093
JasonB
Moderator
@jasonb
The slot for the can head screw can be corrected with a standard cutter or even filing, suggest a washer under the cap head would help too.

As it sounds like there is little to come off the Vee and flat surfaces blueing up and scraping/filing is likely to be all that is needed. Milling could take off more than is needed and then you have to deal with a low tailstock.

Also check that the flat top of the Vee way is not touching the middle of the Vee slot as it looks a bit brighter in the middle
1 February 2024 at 10:29 #711097
Michael Gilligan
Participant
@michaelgilligan61133
+1 for Jason’s analysis

This looks like a hand “fitting” job to me, not a machining job

MichaelG.
1 February 2024 at 11:25 #711116
Martin Connelly
Participant
@martinconnelly55370
The typical tailstock is slightly loose on its base and is clamped down onto it when the clamping lever is used. There are however two features that make sure the tailstock stays on centre. One is a keyway and key to keep the top parallel to the ways and the other is a horizontal screw or two and a point on the base for them to press onto for adjustment. I would not be using that inaccessible screw underneath for clamping, I would assume it should be loose and if there is no current adjustment on top then I would look to modifying it so that there was. This link has a picture showing these features, a key and adjusting screw just above it.

https://www.magzter.com/stories/Hobbies-Craft/Model-Engineers-Workshop/Beginners-guide-to-tailstock-alignment

Martin C
1 February 2024 at 12:57 #711132
Martin Shaw 1
Participant
@martinshaw1
I have measured the lathe bed, the angle of the raised v is as best I can measure it 44.2 deg on one side and 44.7 on the other, so 88.9 in total and possibly not symmetrical. THe original reasoning behind this was to both sort out the fit of the tailstock to the bed and also the arrangement for holding the body to the base and horizontal adjustment thereof. I decided a new base was easier than trying to make the existing one fit, I don’t believe I ever suggested machining the existing base, nor would I try. If in the extremes the centre was too low I can at least shim it to height. The other ideal was to use the tailstock lock to do that alone and retaining the unit on the bed was a separate fixing. The bit I didn’t know how to do beyond a vague understanding was cutting the V groove. I’ll do a wee sketch of my idea.

Martin
1 February 2024 at 17:18 #711193
Howard Lewis
Participant
@howardlewis46836
If the clamp screw is misaligned in some way and forcing the two halves of the tailstock out of alignment, I fully agree with Jason that the easier option would be to solve the problem with the setscrew., rather than trying to re engineer the base.

As he says, probably all it needs is a little machining to provide clearance so that the foul, apparently causing the problem is removed.

Fix the root cause, and life will be much simpler.

Remember the radio amateur’s motto KISS (Keep it simple, stupid)

Howard
1 February 2024 at 18:59 #711214
Martin Shaw 1
Participant
@martinshaw1
I’m all in favour of simple however in this case I want to do a few other things as well like making the screw holding the two parts together tightenable without removing the tailstock from the lathe and providing decent adjustment around the axial centre line. I am also making some retention clamps that hol;d the tailstock to the bed so it slides but doesn’t lose all semblance of alignment when its unlocked. I did a similar modification to the saddle with conspicuous improvement. Meanwhile a sketch to show what I am doing, none of this is major engineering, mostly a bit of facing, drilling and tapping which even I can do.

Martin
1 February 2024 at 22:15 #711238
Howard Lewis
Participant
@howardlewis46836
I cannot but think that your aims will involve a lot of work, to achieve facilities that may see very little use.

After all we are talking hobby lathes, rather than industrial where time is money.

But don’t let me dissuade you!

The prismatic bed provides the alignment for the tailstock base, so that locking the tailstock assembly pulls it down onto the Vee.

Recently, i helped align a Tailstock where there was a clamp, but no adjusting screws to move the upper part relative to the base, for alignment. Lacking that feature, we used a G clamp to provide a screw adjustment, against a lightly tightened top to base clamp screw.

Having obtained the desired alignment, we then removed the tailstock and fully tightened the clamp screw, before rechecking the alignment.

On the mini lathe, such as the Sieg, (As on many other lathes) the upper part of the tailstock is adjusted by a grubscrew on each side, to move the upper part relative to the base. This was how I checked and adjusted the alignment on mine.

Having been given a quick release tailstock, (from another lathe,) found that it could not be aligned closer than 5 mm. Stripping the tailstock suggested that some of the machining had been done with an angle grinder, but that there was quite enough metal to mill 5mm fromone side of the lower half stop, to allow alignment on my lathe.

Having done this, all that was needed was a longer grubscrew on one side, to allow the centres to be aligned to within 0.0005″ (0.019mm) over a 13″ length, with the two halves lightly clamped.

Once aligned, the clamp was fully tightened, and alignment rechecked.

Howard
2 February 2024 at 05:46 #711262
Michael Gilligan
Participant
@michaelgilligan61133
Similar thinking to Howard, but from a different perspective:

Your opening post referenced the difficulty of replicating the groove, and we now understand that the existing groove is imperfect as-is … That adds an order of magnitude to the difficulty of replicating it [which would be a futile exercise anyway].

To my simple mind the the Cart and the Horse need to be put back in their proper relationship !!

.

You already have a ‘nearly right’ groove in a lump of Iron … So spend some time on the manual fitting-work, and get that groove as near-perfect as you can … ignoring, for the moment, all that surrounds it.

When you finally have a good slider … treasure it … because that is your reference for all the relatively simple machining that you will be doing to improve the tailstock arrangement.

[ climbs down from soapbox, to make Coffee ]

MichaelG.
2 February 2024 at 14:14 #711353
Martin Shaw 1
Participant
@martinshaw1
Michael

It’s your opinion however you have been far too literal with replicate, you must surely have realised that I want to put a groove in a completely diferent piece of material. If it was nearly right I wouldn’t bother doing anything at all, however all I wanted was some advice on how to cut a groove, not a lecture on whether it was the right thing to do.

Martin
2 February 2024 at 14:22 #711359
Michael Gilligan
Participant
@michaelgilligan61133
Fine

MichaelG.
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