Emco Compact 5

[Graham MeekParticipant @grahammeek88282]

I had hoped to share the finished assembly of the New carriage and parts today, but the camera batteries need charging.

I have also completed the salvage of the M8 feedscrew thread in the Old carriage. While doing this an idea came to me as regards a combined repair and backlash adjustment insert.

It will mean some loss of travel, but this can be restored by making a thinner Aluminium distance piece similar to the one shown in the photograph below (above the feedscrew).

This only needs to be about 6mm thick to restore the cross-slide to the correct position. Ideally a new feedscrew also needs to be made which is 6 mm longer. This will restore the cross-slide travel to the original settings.

Drawings to follow on all the parts needed for this repair and those needed to fit a New Carriage.

Regards,

Gray,

[Graham MeekParticipant @grahammeek88282]

I have finally had a chance to take some photographs of the progress on Roy’s C5. I will deal first with the salvage of the Old Carriage.

Checking over the casting to see what was worn I was surprised to see only 0.01 mm maximum out of parallel between the Vee-way and the Flat-way to the rear of the machine.

There is a dimension from the flat to the surface where the Plastic Gib strips bolt to. This should be 7.05 mm and due to the wear on this machine it was actually 7.20 mm.

Thus the surface where the Gibs bolt to needed to be machined to establish the 7.05 mm dimension, see Slip gauges above. Also note in this shot the split at the end of the plastic gib. This is due to overtightening trying to take up the wear.

This gives another view which shows the replacement thread is fitted. This shot also shows the wear on the Vee-way, two pencil marks on the way to the right of the new thread shows the extent of the wear, and also the machine marks left by the endmill when establishing the 7.05 mm dimension.

This shows the carriage fitted to a brand new Unimat 4 Bed. This checks the Gibs are doing their bit and that there is no movement other than up and down the bed when the Gibs are adjusted correctly.

This last photograph shows the replacement thread fitted. There will be about 1 mm loss of travel with this design.

Regards

Gray,

[Graham MeekParticipant @grahammeek88282]

Lastly here is the finished New carriage with the parts which I made earlier in this post fitted.

In this view it is possible to make out the 2 mm Dowel in the yellow portion of the casting. This is to stop the Nut rotating when the adjuster screw is moved. It is half in the casting and and half in the Phos Bronze nut. Also note the new Plastic Gib strips which needed replacing due to the cracks in the Old Gibs shown in the previous post.

I still have the drawings to finalise and hopefully Jason will post these in PDF format in due course.

Regards

Gray,

[Jouke van der VeenParticipant @joukevanderveen72935]

Hello Gray,

 

Nice improvements of a worn carriage! This work is above my capabilities, to start with.

For a better understanding I have some questions.

You determined a wear of 0.15mm of the carriage surfaces in contact with the bed. I assume you could measure the height difference between “gib surface” and “bed surface” being 7.20mm. But how did you measure the value of 7.05mm? Or is this a reference value measured on a new carriage?

And then, is the “vertical” wear of the flat surface and the V-surface expected to be the same?

Next question: how did you mount the carriage on the cross table of the milling machine? Was the C5 cross table on the carriage and was its top surface used as a reference for horizontal mounting?

Kind regards,

Jouke

 

[Graham MeekParticipant @grahammeek88282]

Hi Jouke,

To check the casting I place the two flat Ways of the cross-slide dovetails on parallels, on the surface plate.

I know from experience, (see https://www.model-engineer.co.uk/forums/topic/emco-compact-5-modifications/page/2/    ) with C5’s. That the relationship between the flat surface at the rear is such that if a 10 mm diameter Roller is placed in the Vee-way. Then the dimension from the top of this Roller to the Flat way is 10.45 mm.

This then ensures the cross-slide Ways are moving parallel to the bedways and the theoretical Horizontal centre-line of the Lathe axis, ie perpendicular to the lathe longitudinal centre-line, (Headstock to Tailstock).

The 7.05 mm dimension is taken from 4 new Carriages that have passed through the Meek Workshop. They have all been spot on this dimension.

I have a jig made from an Emco Unimat 3 Cross-slide, which is mounted on an 80 mm square piece of Aluminium Tooling Plate, (Flat to within 0.025 over a 300 mm Square). This has the dovetail of the U3 cross-slide uppermost. Thus the C5 Carriage can be loaded onto this and locked using the U3 Locking mechanism and Gib adjusting screws.

Before machining starts the 10.45 dimension is verified to ensure the Carriage is sitting in the U3 cross-slide correctly. It is then a simple matter to machine the Gib surface with reference to the 7.05 mm Slips.

I hope this helps,

Regards

Gray,

[Jouke van der VeenParticipant @joukevanderveen72935]

Thank you, Gray, for your extensive explanation.

I now understand the way of working you followed.

Next questions will be about the anti-backlash bushing you introduced in the worn carrage.

It looks to me that the bushing mounted in the carriage you show in the photo’s is different from what you proposed in the drawings. The drawings you have in progress will clarify this, I expect.

Regards,

Jouke

 

 

[Graham MeekParticipant @grahammeek88282]

Hi Jouke,

The threaded Phos Bronze bush fitted to the Old Carriage is the first solution. I offered the Anti-backlash solution shown at the top of this page above for those who might want to have this facility. I do not intend making this version as I know this will work, plus other things have arisen which makes this impossible now.

Regards

Gray,

[Roy BirchParticipant @roybirch29994]

Hello Graham

 

Did you ever design a lever operated tailstock for the Emco Compact 5?

 

Kind Regards

Roy

[Graham MeekParticipant @grahammeek88282]

Hi Roy,

The Lever Operated Tailstock comes in two guises. The actual Lever Feed for the barrel, (which was originally designed for the Unimat 3).

Or the Lever Clamping Attachment which does away with the need for the Allen key or Adjustable Lever handle.

There is one more photograph of the latter parts which I need to load in a new post.

Regards

Gray,

[Graham MeekParticipant @grahammeek88282]

The missing photograph,

(There was a spare version of this in the box of parts)

Regards

Gray,

[Jouke van der VeenParticipant @joukevanderveen72935]

Thank you Gray,

 

Which thread did you cut on the outside of the PB bush and how did you cut this thread in the carriage part? Drilling and cutting by hand or did you fixate the carriage in your mill to garantee alignment?

Regards,

Jouke

[Graham MeekParticipant @grahammeek88282]

Hi Jouke,

The thread on the outside of the PB Bush is M11x1 P. This was screwcut at the same time as the M8x1.25 P feedscrew thread was produced for absolute concentricity and squareness. The 45 degree chamfer for the locking face is also machined at this time.

The Old Carriage was mounted against an Angle Plate bolted to the milling machine table. Two parallels were used which located the flats of the Cross-slide Dovetail Ways against the Angle Plate. A parallel on the milling machine table located the machined upstand of the Bedway rear Flat Way, this is the face behind the slip gauges.

This keeps everything square.

A spigot was then turned which was a good fit in the core diameter of the worn thread. This then gives something to “clock” to get the milling machine spindle aligned with the old thread. A 10 mm diameter slot drill was then used for the tapping size. A 90 degree countersink was then used to provide the locking face for the PB insert. The last operation is to tap the hole using the machine spindle to ensure squareness.

Regards

Gray,

[Jouke van der VeenParticipant @joukevanderveen72935]

Gray,

Thank you for your extended explanation!

I knew in advance that my description of the approach “by hand” was much to simple!

So to read you took all the measures to keep everything square and aligned, something I can forget with my lack of experience and lack of means. I need to find somebody who is able to copy your way of working, otherwise my old design carriage will stay as it is.

Thank you so much.

Kind regards,

Jouke

 

[JasonBModerator @jasonb]

Graham’s drawings for the cross slide and backlash modifications can be found

 

here and here

[Graham MeekParticipant @grahammeek88282]

Thanks Jason,

Regards

Gray,

[Author]

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