Planning my first 'real' lathe project

[dansawyer]

I have a very servicable Colchester 13 round head lathe It shows wear but aside from the gear noise is fully operational. I have a MT5 to MT3 spindle adaptor which appears to be in good order. When I test the male MT5 fit to the spindle with Prussian Blue it shows a clean mating. When I test a good male MT3 taper to the MT3 spindle adaptor it also shows a clean mating. However when I test a MT3 male ER32 adaptor to the MT3 spindle adaptor it shows a very poor fit. The blue shows a ring about an inch wide at the big end and little down the taper. This is also confrimed by feel, there is a small amount of movement after firmly setting the ER32 adaptor in the spindle adaptor. (If I over set the ER32 adaptor with a firm taps with a brass hammer I can get a firm fit, not a good practice.)
My question is: What is the best way to repair the adaptor taper?
Can a serviceable fit be created with an hss tool and sanding to polish?
My plan is to use a teper attachment and set it with a DTI based on the good taper. Is this the best way? Is there a primer on this I have missed?
Thanks in advance. Dan

 

[MrWhoopee]

Your plan is probably the best approach. Just remember that there needs to be some extra carriage travel before the cut begins to ensure that any lash has been taken out of the taper attachment.

edit: after a bit more thought, this would be a good job for an electric die-grinder adapted to be a toolpost grinder.

 

[dansawyer]

Your plan is probably the best approach. Just remember that there needs to be some extra carriage travel before the cut begins to ensure that any lash has been taken out of the taper attachment.

edit: after a bit more thought, this would be a good job for an electric die-grinder adapted to be a toolpost grinder.

I have been scared away from tool post grinders. If the lathe is covered with an adaquite cloth coveringand the ways are cleaned after grinding is such a tool post grinder 'safe' for the lathe? Is there a fear of the grit getting into 'unclenable' areas? Can this risk be adaquately addressed by simply covering the lathe above?
A tool post grinder has great appeal. I would like to feel comfortable using one. thanks for bringing it up.

 

[markba633csi]

I wouldn't worry too much if you cover the ways and are careful to clean up afterwards
You might have very little material to remove
-M

 

[Larry$]

I made a cheap air die grinder into a tool post grinder buy just machining a block of aluminum to fit. Cover everything with painters tarp. Mark the tarp "Grit side" so it always goes on the same way.
I was afraid that the die grinder bearings would be too sloppy, but if there is play it is all taken up in one direction. I've used it to improve a Chinesium MT3, good fit & finish.

 

[MrWhoopee]

I have been scared away from tool post grinders. If the lathe is covered with an adaquite cloth coveringand the ways are cleaned after grinding is such a tool post grinder 'safe' for the lathe? Is there a fear of the grit getting into 'unclenable' areas? Can this risk be adaquately addressed by simply covering the lathe above?
A tool post grinder has great appeal. I would like to feel comfortable using one. thanks for bringing it up.

Toolpost grinders have their place. If used infrequently and with care, there is little danger to the ways. Covering the ways with something that the grit can't pass through is necessary plus thorough cleanup. Pay extra care to avoid allowing grit under the carriage. This particular job will require much more setup than actual grinding and will generate very little grit. If possible, arrange the rotation so the spark/grit stream is downward and place a pan full of water underneath.

 

[Janderso]

I've never used one myself but for the this operation, It sure seems like the best option. Everything needs to be set up with care and gibs are tight!!

 

[markba633csi]

Do you have a plan to hold the workpiece? You'll need to take a light cut then check the fit- maybe do this several times
-Mark

 

[C-Bag]

I was told the best thing to cover the ways with by a tool and die maker was cling wrap/plastic wrap with some oil to make it cling. Then just carefully toss the mess when done. Not had reason to do it yet but I thought I’d pass that on.

 

[dansawyer]

Do you have a plan to hold the workpiece? You'll need to take a light cut then check the fit- maybe do this several times
-Mark

I had only started to work through holding the piece. I had gotten as far as setup is critical, the part is an adaptor and there are two mounting 'surfaces' that must be as concentric. One is the surface that needs to be machined and the other is an ER 30 collet holder, I had thought about mounting a 3/4 inch precision rod in the ER 30 as the primary mounting point. That is only one point, I believe the other end needs to be held both in concentric orientation and steady as well. There is a surface on that end that may be used, however I have not tested it for concentricity. This is a two part problem, mounting and machining. Thank you for brining that point up.