Thin grooves on smal dia shafts

[chillybilly]

Struggling with cutting the retainig clip grooves for the valves on the nemett engine any tips ??

3mm dia shaft .5 mm width groove ,20mm away from the chuck .

Thought about making a roller box like off a wickman multi spindle ,but that will take an age :-\

 

[tel]

Why 20mm from the chuck? the closer you can get it the better.

 

[stevehuckss396]

When I cut my grooves I reversed the valve and held it in a er11 collet.

 

[GailInNM]

A shop made split collet works well. Just a short length of rod with a diameter larger than the head of the valve and a hole drilled in it the size of the valve stem. Split it length wise with a fine saw like a jewelers saw or hobby shop Zona saw or Xacto saw The saw cut needs to go through the center hole to near the far side to form a hinge. When putting in the chuck make sure the slit is not under a jaw. Brass or aluminum work well for these as they are easy to saw cut. This one is for 2mm stem and is made from 1/4 inch diameter brass. Save them and shoon you will have all your common sizes ready to use by just reaching in a drawer.
Gail in NM

 

[Lakc]

A1 tool steel with a high relief (15degrees) held exactly on center in my parting tool holder. Machine it to your groove dia and harden it. I didnt bother to temper it, just keep the speed high when grooving. This is a 3.5mm stem valve in pic.

 

[chillybilly]

Thanks chaps ,

As to the 20mm out of the chuck ,its got a 28mm valve stem so it all ends up a bit long .

How are you getting the split collet to run concentric ,is that a 4 jaw job .

Could really do with a collet chuck and some collets .One day maybe

 

[tel]

Turn a short section of the stem first, and do the groove before pulling more out from the chuck and finishing the stem. Absolute concentricity won't matter so much up there at the end as it only has to hold the keeper and spring.

 

[LongRat]

I have heard of people grinding the grooves with a dremel in the toolpost and a thin cut-off disc. If you have a toolpost grinder then you are golden.

 

[Drei]

I have built the lynx engine and i machined the valves stem by reversing then in the collet chuck.

Drei

 

[GailInNM]

"How are you getting the split collet to run concentric ,is that a 4 jaw job ."

While most three jaw chucks have some runout they are normally quite repeatable if the scroll and jaws are clean. When you drill the hole, mark the position of the number 1 jaw before removing it to slit. Then slit it between the #1 and #2 jaw positions. When you reinstall it in the chuck align the mark with the #1 jaw.

Even if you are off a little bit the retaining rings would not have a problem as long as the groove bottom diameter and width are correct.

Gail in NM

 

[chillybilly]

Yeh i guess so ,when i was an apprentice you would have been put on swarf duty had you been seen putting anything in a 3 jaw like that .Guess when its been drummed into you like that you dont think of it :big: 10 weeks solid screwcutting too ,didnt forget that either

Off in the shed to make some noise LOL