Bedway vee angle

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

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

-

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

Alan,

That could prove rather frustrating !!

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

MichaelG.

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

The Harrison M300 is 70 degrees.

Dave
The Emerald Isle

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.

Mini lathes are 90 degrees.

Neil

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

Very decent of you, John

MichaelG.

**LINK**

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

.

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

Probably an ideal job for a Shaper.

MichaelG.

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

-

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

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

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.

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

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

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

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

.

John,

Apologies if I caused you any inconvenience.

MichaelG.