Setting Taper attach on 13 looking for a better way.

Rudd · Dec 2, 2018

I fitted a TA to my 13 specifically to turn B&S 9 tooling for my mills. I have tried the "indicate off a known good taper" method, I've tried indicating off something straight like the tailstock barrel. Even when it looks right on the indicator, the actual cut seems to be slightly off.

I could adjust for this by indicating the taper and taking another light pass, but the TA adjustment method seems to be "unsnug bolt, tap with small wrench, snug bolt, see what that did". I seem to be circling the correct .0417"/inch taper, always a bit under or over.

Has anyone come up with a better way to set the bar? Some sort of mod where you can adjust the angle of the bar with a screw for example?

Thanks

moonlight machine · Dec 2, 2018

Rudd said:
I fitted a TA to my 13 specifically to turn B&S 9 tooling for my mills. I have tried the "indicate off a known good taper" method, I've tried indicating off something straight like the tailstock barrel. Even when it looks right on the indicator, the actual cut seems to be slightly off.

I could adjust for this by indicating the taper and taking another light pass, but the TA adjustment method seems to be "unsnug bolt, tap with small wrench, snug bolt, see what that did". I seem to be circling the correct .0417"/inch taper, always a bit under or over.

Has anyone come up with a better way to set the bar? Some sort of mod where you can adjust the angle of the bar with a screw for example?

Thanks

I set mine close then move the carriage to take the lash out of the works. Then 0 the DRO, move the carriage 4 or 6 inches or whatever. note how far the cross feed has moved and adjust to suit. Mine is dead nuts after 2 or 3 trys and no stock is wasted.

n2zon · Dec 2, 2018

moonlight machine said:
I set mine close then move the carriage to take the lash out of the works. Then 0 the DRO, move the carriage 4 or 6 inches or whatever. note how far the cross feed has moved and adjust to suit. Mine is dead nuts after 2 or 3 trys and no stock is wasted.

As I'm fresh out of DROs for my SB13 I have the same question as the original poster. Setting the TA up accurately seems to take about three days past forever.

moonlight machine · Dec 2, 2018

n2zon said:
As I'm fresh out of DROs for my SB13 I have the same question as the original poster. Setting the TA up accurately seems to take about three days past forever.

So get one. If it really takes that long to set up the TA you will pay for the DRO the first time you use it. I set my TA in about 5 minutes. Or get 2 HF digital calipers and clamp them to the carriage and cross feed. That's what I did with my South Bend about 25 years ago.

TheOldCar · Dec 2, 2018

moonlight machine said:
I set mine close then move the carriage to take the lash out of the works. Then 0 the DRO, move the carriage 4 or 6 inches or whatever. note how far the cross feed has moved and adjust to suit. Mine is dead nuts after 2 or 3 trys and no stock is wasted.

Freak, that alone justifies me getting a DRO for one of the lathes. Making a 2 degree taper shank for a Schaublin tailstock took waaaaaaaaaaay too long. And without confessing too much redneckery, it involved lots of Dykem! The amount of test fits done I'm sure have wallowed the tailstock bore into a "custom" shape now. :crazy:

Adjusting taper attachment with a dial indicator & soft hammer, cutting a sample, marking, fitting, noting needed adjustments...and all of this more times than I want to remember. When the taper was as close as I could possibly get, machined shank was moved to my PPTGP.
((((Proprietary Precision Taper Grinding Process=Sandpaper :dunce:

)))))

Did I mention it took a while?

I'm not saying it was a useless experience. I'm saying (to myself) that I need a DRO!

moonlight machine · Dec 3, 2018

TheOldCar said:
Freak, that alone justifies me getting a DRO for one of the lathes. Making a 2 degree taper shank for a Schaublin tailstock took waaaaaaaaaaay too long. And without confessing too much redneckery, it involved lots of Dykem! The amount of test fits done I'm sure have wallowed the tailstock bore into a "custom" shape now.
Adjusting taper attachment with a dial indicator & soft hammer, cutting a sample, marking, fitting, noting needed adjustments...and all of this more times than I want to remember. When the taper was as close as I could possibly get, machined shank was moved to my PPTGP.
((((Proprietary Precision Taper Grinding Process=Sandpaper )))))

Did I mention it took a while?

I'm not saying it was a useless experience. I'm saying (to myself) that I need a DRO!

So get one. it's only money, you will make more!

fciron · Dec 4, 2018

It may not be an issue of adjusting the taper attachment. Will your lathe cut straight within a tenth over the same area where you're having trouble cutting the taper?

If the late won't cut straight then it won't cut the correct taper either. Bed wear, tool flex, etc. may not show up when indicating on the good taper without the cutting forces applied. It doesn't take much to keep tapers from fitting together.

Bruce Nelson · Dec 4, 2018

Use a test bar and a dial indicator. Determine the inch per foot of the taper you wish to cut. Use that information to learn what the indicator travel should be between two reference marks on the test bar. (Suggest the distance should be exactly 6 inches, or 3 inches, the longer distance will result in a more accurate taper) Make sure you eliminate the backlash before you take the indicator reading. If you are going to turn the taper between centers, then the test bar must be also mounted between centers; If you are going to turn the taper with the workpiece held in a collet or chuck, then you must mount the test bar the same way, without the outboard end supported by a center in the tailstock.

Don Kinzer · Dec 4, 2018

Bruce Nelson said:
Use a test bar and a dial indicator.

You can also rig up a way to hold a sine bar and the correct stackup against a ground bar held in the chuck and then indicate on the sine bar, adjusting for zero deflection. Lautard's Machinist's Third Bedside Reader has an idea for such a setup on page 16. If your taper attachment's guide bar is exposed you might be able to set up the sine bar on the taper attachment and indicate on it there.

You can also use a long travel indicator on the carriage and another indicator on the compound. Move the carriage a given distance, say 2 or 3 inches, and check the cross slide movement. I recently set the angle of my compound for cutting an MT5 taper this way, checking the result with bluing compound.

Rudd · Dec 4, 2018

thanks all. I was really asking if someone had a better way to adjust the bar than tapping with the little Williams wrench for the carriage lock. Looks like that is a "no".
Fciron has a good point, it's a pretty clapped out lathe, but I plan on cutting the taper down near the tailstock running between centers. I've been working on a practice piece which is pretty short, so cutting on the more worn area of the bed.
The first project is for a *straight* 1" arbor for the horizontal mill.
If it all goes south, I'll get a B&S 9 3/4" collet and weld the arbor into it.

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Setting Taper attach on 13 looking for a better way.

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