Bedway vee angle

[AlanWParticipant @alanw96569]

I've been making a carriage stop over the last couple of days, unashamedly copied from the Journeymans Workshop site. I couldn't for the life of me get it to seat properly on the vee and, eventually, noticed that the angles differed. Having multiple-checked my own work and concluded that it is 90 degrees, I turned my attention to the lathe. A quick check with a digital angle gauge on the front vertical and both slopes shows it to be 86.4 degrees! I am not a happy chap.

Anyone else found this anomally?

Alan

[AlanWParticipant @alanw96569]

Are these normally 90 deg?

[AjohnwParticipant @ajohnw51620]

The way they are probably made the actual angle doesn't matter as the mating parts can be offset and machined at the same time, in this case it might be by just by using the same tooling.

This is how slideway grinders tend to work on prismatic beds. The saddle is carried on a sub table and offset so that grinding one side of the V on the bed grinds the opposite side of the V on the mating part. It helps insure that the angles actually match – the important aspect.

John

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[Roger Provins 2Participant @rogerprovins2]

Never thought about it before but have just measured my old Chinese 9 x 20 and it's 90 degrees.

[Michael GilliganParticipant @michaelgilligan61133]

Alan,

That could prove rather frustrating !!

I suppose the big question is: Do the male and female dovetails match?

MichaelG.

[Martin WParticipant @martinw]

Hi

On my Chester DB7V the angles of the V Ways are 90 deg so no problem in making various bits that locate on them.

Martin

[steamdaveParticipant @steamdave]

The Harrison M300 is 70 degrees.

Dave
The Emerald Isle

[John Stevenson 1Participant @johnstevenson1]

Colchester Bantam is 90 degrees as just made some new bits for it.

I presume the Chipmaster is the same as they share common items like saddles.

[Neil WyattModerator @neilwyatt]

Mini lathes are 90 degrees.

Neil

[JourneymanParticipant @journeyman]

Sorry about that, wrote the original article in 2011 and as it fitted and worked I never thought to check the actual angle. I have just done so and as near as I can make out the angle on my WM 250 is 88.4 degrees, close enough that I didn't notice the misfit.. Not, I'm afraid that it will help a great deal but I will add a note to the article for the benefit of anyone else who builds it. Only cure I can suggest is a little manual adjustment with a file!

John

[Michael GilliganParticipant @michaelgilligan61133]

Very decent of you, John

MichaelG.

**LINK**

[AlanWParticipant @alanw96569]

Interesting responses. The lathe is a WM240 so, copying John's design, I assumed it would be OK. From what the other John (Ajohnw) says regarding the way the bed and saddle are ground, I suppose I'm just plain unlucky that my example is more acute than on Journeyman John's WM250. The only way I can invisage milling out the angle is by using a dovetail cutter, that I don't have, or by using a cutter small enough to go into the 'dead' area at the apex and a lot of time. Any suggestions would be more than welcome.

Alan

[Michael GilliganParticipant @michaelgilligan61133]

Posted by AlanW on 12/02/2016 12:15:44:

… Any suggestions would be more than welcome.

.

[Whisper it, for fear of starting Civil War] :

Probably an ideal job for a Shaper.

MichaelG.

[AjohnwParticipant @ajohnw51620]

A bit of courage, a hand file and some engineers/micrometer blue. When it gets to a close fit very little blue is needed, so little that it can be hard to see. Even when way out it's ever so easy to put too much on.

I did think of adding that this angle is one that may be played about with according to the general geometry of the lathe in respect to cutting pressures etc. Not cast in stone just as dovetails angles on slides can vary.

Edit – Some thin plastic etc gloves are a good idea when using blue – it can get all over the place and be difficult  to wash off.

John

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Edited By Ajohnw on 12/02/2016 15:47:17

[JourneymanParticipant @journeyman]

Engineers blue and a small scraper might do it. Unfortuneately I noticed when measuring mine the "V" is also lopsided so it will be difficult to find a datum to work off. I don't think it needs to be a 100% fit provided it doesn't move at all once it is clamped up.

John

[mechman48Participant @mechman48]

The ways on my WM 250 V-F… according to my digi gauge, one side measures out at 44.4* & the other at 44.6* = 89* I made my carriage stop to suit using Engineers blue & it clamps up just fine.

George.

[AlanWParticipant @alanw96569]

I'm afraid I don't have a shaper or even access to one, just the lathe and my home-brewed mill/drill. I should also add that I still consider myself a beginner when it comes to precision engineering, although I've been tinkering for a good many years. I am yet to build a model, despite that being the original objective.

In my repeated attempts to get it to fit, the notch is now too big to salvage by files or scraping but that may be my route for the next attempt. My filing skills are not great so machining is preferred. I spent some time this afternoon making a profile from aluminium sheet using the good old file to fit method. I'll probably scan it and draw over the resulting template to ascertain the angles more precisely.

My "V" is also assymetric John; I think it must have been a Friday afternoon job after a lunch time session down the pub, if they dare do that in China.

Thanks for the suggestions folks. Keep 'em coming.

Alan

[Michael GilliganParticipant @michaelgilligan61133]

Alan,

Looking at the drawing again … there may be a realistic way to machine what you need.

Split the vee at the apex [12 dimension line] and make it in two parts; then secure with dowels and counterbored cap-head screws. … You would probably want to skim all the outer surfaces after assembly.

MichaelG.

.

P.S. … Here is some bedtime reading.

Edited By Michael Gilligan on 12/02/2016 21:26:24

Edited By JasonB on 13/02/2016 13:16:11

[JourneymanParticipant @journeyman]

Michael, sorry you can't link direct to an image or pdf on the Journeymans-Workshop, it stops bandwidth being used. You will have to go via the page Saddle Stop and scroll down to the drawing.

Cheers John

[Ian S CParticipant @iansc]

Allan, if you have a file, and a grinder, you can have a scraper, grind the tip of the file to shape, and sharpen on an oil stone. If it's an old file, grind the teeth away, just don't over heat, and draw the temper.

Ian S C

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Journeyman on 13/02/2016 10:55:42:

Michael, sorry you can't link direct to an image or pdf on the Journeymans-Workshop, it stops bandwidth being used. You will have to go via the page Saddle Stop and scroll down to the drawing.

Cheers John

.

John,

Apologies if I caused you any inconvenience.

MichaelG.

[AlanWParticipant @alanw96569]

Michael, thanks for the suggestion and link. I could probably salvage the job by following that route, especially as my version of John's design is twice the width (because I happened to have a piece of 30mm square handy) giving plenty of space for a couple of dowels and a cap-head. I favour socket cap screws for most of my projects anyway, keeping well stocked with M3 to M10 in various lengths. Thanks again.

Ian, I'm not brilliant with saw and file, so the thought of scraping fills me with dread! It is probably a phobia I should break for my own good. I read about doing it years ago in MEW (I have issue No 1) but photos and words don't really convey the technique very well. I believe it is one of those skills that needs to be demonstrated. Any volunteers for a presentation at the engineering exhibitions? It would probably draw more interest than some subjects that have featured.

Alan

[AjohnwParticipant @ajohnw51620]

Use a scraper for this sort of thing ? It would be a lot easier to do with a file.

Either way a shallow saw cut at the top of the V is likely to help.

John

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[JourneymanParticipant @journeyman]

Michael, no inconvenience at all., just thought I would explain that the link wont work. I set it up to like that when I found that some enterprising far east hacker had copied most of the site, given it a different name but still kept all the links to my images. Basically I was helping to run another site for free. I don't have problems with people copying and using anything, if I did I wouldn't have made a web site! I just object to funding some free-loader who can't even be bothered to write their own articles.

Cheers John

[Neil WyattModerator @neilwyatt]

Posted by AlanW on 13/02/2016 12:01:51:

Any volunteers for a presentation at the engineering exhibitions? It would probably draw more interest than some subjects that have featured.

At the last Model Engineer Exhibition Neal Reid was demonstrating scraping (and letting punters have a go) on the SMEE stand.

Neil

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