Myford ID grinder arbors

I have a MG9 grinder which came with the internal grinding attachment. It has one single arbor for holding ID grinding wheels which is obviously home made. I want to make a selection of arbors for the vaious grinding wheels that I have, it would help me a lot if I could get some pics and/or dimensions from anyone who has them.

The arbors have a steep cone that locates in the spindle and is held in with a collet nut.

Can anyone help me with this?

Regards

Pete.

I knocked up a quick and dirty arbor to get me through the job at hand. It worked appreciably well but since I didn't have a LH retainer I had to watch for the retaining screw coming loose.

Incidentally, I found an arbor in the box of bits that doesn't belong to my grinder, it's much too large. I have no idea what it fits but the taper is a very close fit so I'm guessing it might be for a MG12 or some other ID grinding head. If anyone can identify it let me know please. I've put the basic dims below.

I have an older MG12. The internal spindle bolts to the front of the wheel spindle, replacing a plate, as opposed to the later pulldown internal spindle. The dimensions given above do not relate to the internal arbor I have. As far as I am aware the internal spindle didn't change between the MG9 and MG12.

Andrew

Mine is the same design Andrew. You remove a cast iron name plate then bolt the internal head in it's place. Remove the belt cover and bolt a large cast ally pully to drive the head with a flat belt and fit a cast ally belt guard.

My arbor nut has a 5/8"-20tpi RH thread and passes through 0.442". Does that sound similar to yours? If so I'd love to get some pics/dims of whatever factory arbors you have.

Also, how are your wheels retained? LH screws?

This is my internal grinding setup (I don't have the belt guard casting):

I got one internal spindle arbor with my grinder. Judging by the patina and style I judge it to probably be original Myford manufacture:

My spindle thread is the same, 5/8" 20 tpi Whitworth RH. The key dimensions of my arbor are:

Taper small end: ~0.235"

Taper large end: 0.547"

Length of taper: 1-1/16"

Diameter of plain cylindrical section: 0.471"

Diameter of grinding wheel cylindrical section: Nominally 3/8", but is tapered by ~12 thou along the length

The internal thread for the screw that holds the grinding wheel is 1/4" 26tpi RH, ie, BSF.

I have the original manual for my MG12, with the correct serial number manually typed in red on the page regarding serial numbers. The section on the internal attachment is unhelpful. Mostly about how to fit it, and how to do the initial fitting and alignment if it was bought at a later date rather than with the base machine.

Andrew

Thanks Andrew. Your dims work out 3.486" / foot of taper my guess is that it's 3.5" / foot given the difficulty in measuring such things precisely.

I think that our ID grinding heads are very similar if not identical. The covers are obviously different because the MG9 motor is in the cabinet.

Regards

Pete