Clayton undertype

[Phil1965]

Hi I am building a 2” Clayton and now looking at machining the compensating centre. The apertures for the pinions is making me scratch my head a bit. In the construction notes it references using a snap gauge and references a sketch for details. Unfortunately they forgot to include the sketch.
I would be grateful if someone could give me a idea on what this snap gauge consists of. Apologies if these seams a bit simplistic but I am new to this pastime
Thanks Phil

[Jo]

 

I need pics to remember what you are talking about from when I made mine

Jo

[Phil1965]

It’s the cut outs on the centre for the pinions

Many thanks

Phil

[Jasonb]

The only two surfaces that need machining are those either side of the small pinion gears at 7/8 and then 3/8 from that.

I would set it up true on the rotary table offset to do the first of the 7/8" faces with say a 5/16 or 8mm cutter and then rotate the table to do the other two at the same setting. Then similar on the opposite face rotating round for the other two, you can measure or use a gauge block to check the 3/8 dimension. That's how I did my Fowler one but did not need to worry about the rotary table as there are only two pinions on that so simply + and - on the Y axis either side of zero.

I suspect the article was written at a time when most milling would have been done on the lathe without milling machine, rotary table and DRO that most seem to have these days so the old methods may not be the best now.

[Phil1965]

Thanks Jason
I have a milling machine and rotary table but never thought on that method. Suppose I got to wrapped up in the construction article. As long as I reference the bores for the pinions spindles it should be straight forward

Many thanks
Phil

[Jo]

The three pinions need to be at 120 degrees and this is set by their spindles so this must be cut first. I recall drilling and reaming the mounting holes those by mounting the casting on my indexing head to get the three holes at exactly 120 degrees.

As Jason mentioned you can then mount the casting centrally on a rotary table and get the centre line of the gear square to the bed. I recall doing that by poking a long bar in the pivot hole and looking along the milling machine table. The only critical distance is the width of the gap into which the pinion fits and that all three slots are equal distance out from the centre.

Then you can mill the inner and outer faces of the pinion hole. Rotate the table round 120 degrees (check it is right using the bar in the pivot hole) Repeat milling the inner/outer faces and then twirl round and do the final pinion hole.


Jo

[Jasonb]

Yes the ideal way would be to not disturb it's position on the rotary table between the two operations, you could do them in any order just remounting the R/T form horizontal to vertical. That way the pin holes will be at right angles to those machined surfaces and radial to the central axis


EDIT, jo the width is given and is the 3/8" that I mentioned in my first reply (9.53mm may make it easier for you to understand)

[Jo]

It would be better to use an indexing head if you had a vertical/horizontal one as they lock spot on the correct angle.

Jo

[Phil1965]

Thanks Jason and Jo, just been looking at the drawings and it all makes sense what you have suggested. Jo unfortunately I only have a rotary table not a indexing head but I am sure if I only index in one direction making allowance for any backlash I will be good.
Thanks again this forum is a wealth of information.

Thanks

Phil

[Jasonb]

It's always worked for me , I just put a bit of thumb pressure on the side of the table to introduce some drag which takes up any backlash and make sure I'm always turning in the same direction.

Out of interest are the Clayton gears supplied machined or cast? or will you be cutting your own?

[Phil1965]

The gears are machined from Blackgates. Not up to gear cutting. That’s on the agenda for the next project.