tapping on the lathe

[colin]

Hi guys I have an awful lot of blind nuts to make any suggestions or home made tooling to help with the tapping of them to speed things up.

Thanks. :bow:

 

[Twmaster]

There's a good tutorial in the MIT machine shop videos. Kinda generic but would likely give you some ideas for a setup.

http://techtv.mit.edu/collections/ehs-videos/videos

 

[Lew_Merrick_PE]

Hi guys I have an awful lot of blind nuts to make any suggestions or home made tooling to help with the tapping of them to speed things up.

Colin,

I assume that by "blind nuts," you mean a blind tapped hole for something like unto an acorn nut. ??? You might want to think about forming the threads rather than cutting them if the material is malleable enough. This process is quite dependent on the lubricant used, but most suppliers of such taps produce guides to lubricants.

An adjustable torque slip clutch makes life a whole lot easier when using this type of tap ("TorqueTamer" was the brand of such clutches most common in my area -- Washington State -- a few years back). That way, when you bottom out, the tap merely spins in the toolholder (you will have to make your own adapter). A real tapping head is even better. Beware of the Chinese imitation "TapMatic" heads. Some are OK, but many have a ways to go before they qualify as marginal. There is an Indian-made tapping head (sold by Harbor Freight from time to time) that is actually pretty good. The main thing with the Indian unit is to take it apart, clean out the debris they leave in it, grease it up with good lithium grease, and watch all the adjustment screws (ND brand "VibraTite" works quite well) as they tend to loosen up with use. Once reworked in this manner, they are about 80% as good as a TapMatic head. (I usually replace the "Belleville washers" in them with good quality ones too.) A tapping head provides axial misalignment compensation that you will not get with an otherwise axially rigid set-up with an adjustable slip clutch.

Figure a TapMatic head will run you about $500. The Indian head from Harbor Freight is usually priced about $100. A 40 lb-ft rated TorqueTamer (nearly a decade ago) ran about $50.

My paper on Pilot Hole Considerations posted at http://www.scribd.com/Lew Merrick has the equations for calculating the proper fit for form thread taps. The pilot hole is larger than you would use for a cut-thread (standard) tap as you are moving material to make the threads rather than cutting it away.

 

[Deanofid]

Colin;
How many nuts?
WHAT size thread?
Also, what lathe are you using?

 

[Blogwitch]

Colin,

I normally power tap down to about 2.5mm to 3mm (3/32" to 1/8") using just a home made tapping holder mounted in the tailstock chuck. I did a post somewhere about making them, but as usual, I can't find it. The attached pic shows the large one I made. The small one I made was from a cheap pin chuck set.

The lowest speed my machine goes is 65RPM, but it does have reverse to screw it out again. That relies purely on 'finger feel', and I can't remember the last time I broke a tap off doing it. I just feed in holding onto both side arms with thumb and finger until I 'feel' the tap bottoming, then just let go of the arms, and the tap holder just carries on turning, put the chuck into reverse and hold the arms to screw the tap out again.

A good quality high pressure tapping lube is essential in all materials, and very good quality taps, which I grind the ends up to give a true 'bottoming' tap.

Down a bit on this post shows the sort of things and sizes they will do. Making small acorn nuts is dead easy.

http://madmodder.net/index.php?topic=1054.msg9447#msg9447


Bogs

 

[Tin Falcon]

Maybe some ideas here
pdf download: production threading to close limits by hart original compliments of the geometric tool company
PDF File HERE

Colin what are you using now

I would probably use a Spring type tap guide and use a spiral flute tap. these push the chips up and out so no need to stop to break your chip just all the way in and then back it out.
tIN