Stuck taper

[Wendelspanswick]

Why not mount a coarse grinding stone on to the table at the correct angle for the taper and then start the drill and lower the quill till it meets the stone. You can keep repositioning the stone to get a fresh face and then change to a finer stone if required.

 

[I'm getting on a bit]

Maker, there is no need to disassemble to polish out the high spot unless you like extra work

 

[Pete.]

Polish the high spot out till it runs true use emery cloth supported by a file.

Use blue to keep the correct taper

Don't try to do this with the spindle running, all it will do is follow the profile. If the taper is bent the only option is machining.

 

[I'm getting on a bit]

Don't try to do this with the spindle running, all it will do is follow the profile. If the taper is bent the only option is machining.

Sorry did not make clear to rotate spindle by hand

 

[cocker]

Less than 0.001" of run out ?
Just how accurate do you want ?
It's just a drill

 

[rory1]

I agree with the above, have you ever used a pillar/pedestal drill to work to sub 1 thou tolerances? Unlikely

 

[I'm getting on a bit]

Less than 0.001" of run out ?
Just how accurate do you want ?
It's just a drill

Yeah 8 tenths TIR equates to. 0004" runout

 

[Maker]

I agree, it does seem small. It could be simply that the chuck is badly worn (it definitely is worn, just don't know how badly).

 

[Spark plug]

As has been said its not a jig boarer, I would start by getting a new chuck and seeing ware you are at.

Unless you get a top end chuck like an albrechet, your going to compound the runout any way or reduce it if your lucky.

 

[brightspark]

my-Churchill -drill just has the Jacobs taper on the end of the spindle -

 

[Screwdriver]

Is this an internal or external taper? I just restored a Dumore toolpost grinder and it needs a job!

 

[MattF]

I think we need a photo. I'm confused as hell as to what's what.

 

[Pete.]

Less than 0.001" of run out ?
Just how accurate do you want ?
It's just a drill

If the taper is an inch long and running out a thou at the end because it's bent, then you put a 3" long chuck on it with 4" of drill sticking out the tip of the drill will have 7 thou of runout.

 

[I'm getting on a bit]

If the taper is an inch long and running out a thou at the end because it's bent, then you put a 3" long chuck on it with 4" of drill sticking out the tip of the drill will have 7 thou of runout.

Not necessarily because runout is only half of the total indicator reading, I explained this above.

To check what the runout would be over any given distance maker needs to give two readings and the distance between the two readings.

But when the drill touched down on whatever he was drilling the drill would find it's own centre.

I'm sure lots of even the most amateur lathe users would have seen this when a clearly off centre, centre drill has been started then see the centre drill find it's centre in the workpiece by the force's of the rotating chuck.

Maker just needs a new chuck and try it and see that there is nothing to worry about

 

[Pete.]

I never mentioned TIR, what I said holds true the runout is amplified by the ratio of the distance from the bend if it's a thou at one inch it'll 7 thou at 7 inches.

 

[cocker]

If the taper is an inch long and running out a thou at the end because it's bent, then you put a 3" long chuck on it with 4" of drill sticking out the tip of the drill will have 7 thou of runout.

You'll have more problems with a badly ground drill bits

Board now , do as you like - you will anyway

 

[Pete.]

The main reason you don't want the taper running out is the same reason you don't use an end-mill in a drill chuck without a drawbar. The side forces generated tend to work the taper loose. Of course when you're drilling the chuck can't exactly fall out but it can loosen and spin the taper.

 

[I'm getting on a bit]

I never mentioned TIR, what I said holds true the runout is amplified by the ratio of the distance from the bend if it's a thou at one inch it'll 7 thou at 7 inches.

Ha ha wrong, unless Maker gives two readings and the distance between them it could be just eccentric and would be less than a thou over the 7 inches. But like I say it will still run true when it hits the workpiece.

I'm sure everyone who has used a drill press will have seen a wonky drill run true when it touches down notwithstanding that the drill is correctly ground

 

[Pete.]

Ha ha wrong, unless Maker gives two readings and the distance between them it could be just eccentric and would be less than a thou over the 7 inches.

You're arguing a point I haven't made. Here's what I said:

If the taper is an inch long and running out a thou at the end because it's bent, then you put a 3" long chuck on it with 4" of drill sticking out the tip of the drill will have 7 thou of runout.

What bit of it is wrong?

 

[Maker]

You're arguing a point I haven't made. Here's what I said:


What bit of it is wrong?

You're assuming the taper is on the wonk whereas he's suggesting the taper is straight but off centre.
I only gave one measurement so you don't know which it is.