Test bar

I bought a 4 morse taper test bar from the Allexander Palace show on Saturday.I have a Myford large bore and discovered when tried that it is to long and won't enter the 1" bore to allow the taper to seat.I don't want to cut off the end, if at all possible as I wish to retain the centre pop so that I can use the bar for between testing.The bar is hardened,can I turn this down or is grinding the only solution.Your approach to the problem would be appreciated.

Frank

Would you trust a modified test bar? There may be residual strains from heat treatment that will be released by grinding off the material that is causing the problem. I think you would have to get the whole thing carefully checked after modification and it may need complete regrinding to get back to the original specifications if you want to keep the existing centres. If you abandoned keeping the end with its centre just cutting the end off should not cause the rest of the bar to distort. You may though have a problem in that the original specification was with the morse taper supported over its whole length. Removing part of the taper may change the setting of the bar in the socket.

These are just thoughts and the only way to find out if it is possible is to do the grinding and check the bar afterwards.

Martin

Contact the Supplier? They may have a shorter one.

Did you explain what you intended to do with it and on which machine, bet not.

At the risk of causing a choking fit in the Myford camp, is there sufficient "meat" in the spindle to allow an enlargement of the bore at the back of the taper to allow the test bar to seat correctly in the morse taper. The spindle should be soft and a No4 taper large enough to get a boring bar to the back of it. As already said, cutting about a carefully machined test bar seems likely to introduce errors.

Paul

Actually answering the OP's question ...

My understanding is that you wish to reduce the diameter of the small end of the morse taper. My experience with an ER collet chuck and a QC tool holder, both hardened to some degree, is that you can machine these with TC tipped tooling. I'd use a small radius tool tip and go for it - I don't think you can do much harm.

Cheers,

Rod

That seems entirely reasonable, Rod

MichaelG.

I agree with Rod, just remove metal in the required area.

Tony

Thanks for al the input.I will give your sugestion a go Rod there is 1.5" to reduce to 1" so that it will fit into the 2.5" long taper of the spindle bore.I did tell Warco's salesman I wanted it for a large bore Myford.

Frank

Perhaps I'm missing something or being dense (probably) but how the hell can a 4MT fitting on a test bar be 1.5 inches too long to go into a 4MT socket in the end of a lathe spindle. The small end of 4MT is only 20 thou in. bigger than the 1 inch bore. The only way I can see a standard 4MT male being too long is if the lathe has a "stub" MT taper in it, and since the bore is 1 inch there wouldn't be any point in machining a short taper and then having a step.

I'm confused!

Just read the post above and I'm amazed that Myford would build the lathe that way.

Edited By Keith Long on 18/01/2016 19:52:21

Kieth

The Taper from the face of the spindle to the start of the 1" bore is 2.5" and as the test bar that I bought has a taper of 4" so it would not enter the 1" bore so I had to reduce the end of the taper by 1.5" for it to fit.Thanks to Rods sugestion I used a tipped Knife tool ground to a small tip and using 77 rpm and fine cuts so as not to build up to much heat as well as lots of coolant .I was wary of the build up of heat but using this approach it was barly noticable.A satifactory result.Thanks to all who replied to my dilema.

Frank