8-40 tap recommendations

[dakor]

After just breaking off a brand new 8-40 tap in a remington 700 reciever. I am looking for some recommendations on a new 8-40 tap. This was suppose to be a good tap and it was not cheap and I babied the damn thing the whole time and did it by hand. Each hole was taking about 30min. I was really cutting light and backing it out with lots of vipers venom.

I got to the bottom of the third scope base hole and go to turn it out and snap.

Now I get to deal with getting it out and I am not sure what I am doing about that yet. I have a couple more 8-40 taps but they are made by the same place so I dont even want to chance it.

 

[Dan-Schenk]

I’m not sure about the tap, but try using boelube next text.

 

[Alex Wheeler]

2 flute spiral point from brownells, moly d, under power.

 

[LVLAaron]

You may have work hardened something with all that back and forth. No reason to just send it, on a thin through hole like that.

 

[whatsupdoc]

What hole, did you hit the locking lug?

 

[Bill Rodolph]

Were you keeping the tap straight? If not guided in a press or mill its easy to cock those little ones just a tad and snap.

 

[akajun]

You may have work hardened something with all that back and forth. No reason to just send it, on a thin through hole like that.

This
, in and out as least as possible
Les chance of work hardening r chipping a tooth

 

[jackieschmidt]

Taps are not designed to break.

The OP is doing something wrong.

There are several things that can cause tap breakage. First is the tap is dull. Since the OP is using new taps, that probably not the problem.

next is the wrong tap drill, ie too small. This is extremely important with small taps because you are dealing with just a few thousandths that can actually be smaller than the minor diameter.

Next is the tap not started dead straight. With small taps, just a slight amount of cant can lead to breakage. Never just try to start it by hand. Take it from a real machinist. It is virtually impossible.

Let me repeat. Taps are not designed to break. If used properly, the problems the OP is encountering should never happen.

 

[Walt Krafft]

What size hole were you trying to tap?

 

[dakor]

Its a new stainless remington and I was tapping a 8-40 hole. The action felt hard from the start much harder than the last blued action I did. I think if I would have used power the tap would have went right away.

i just turn the mill by hand and never had an issue until now. I was at the bottom of the hole and went to go back up and bam. It was the rear flat of the action on the third hole counting from front to back on the action. Its been a shitty week so might as well add to it.

 

[boltfluter]

Its a new stainless remington and I was tapping a 8-40 hole. The action felt hard from the start much harder than the last blued action I did. I think if I would have used power the tap would have went right away.

i just turn the mill by hand and never had an issue until now. I was at the bottom of the hole and went to go back up and bam. It was the rear flat of the action on the third hole counting from front to back on the action. Its been a shitty week so might as well add to it.

If for some reason the tap is Chinese manufactured that almost guarantees it will break. OSG is my favorite brand for a quality tap. Not sure if they make an 8-40 though.
Paul

 

[jackieschmidt]

If for some reason the tap is Chinese manufactured that almost guarantees it will break. OSG is my favorite brand for a quality tap. Not sure if they make an 8-40 though.
Paul

Remington supposedly manufactures their SS actions from 416. If anything, it should tap easier than a regular Chrome Moly Action.

In my shop, we tap a lot of holes. However, most are in the 3/4 through 1 1/4 range. I of course do some of my rifle work there.

your problem might be the quality of the taps. In any major tool house catalogue, they will have tools such as drills and taps listed as domestic, and off shore. the Offshore is usually substantially cheaper.

But it is a classic case of getting what you pay for.

 

[Walt Krafft]

What size tap drill did you use?

 

[hogpatrol]

On sketchy material like SS or CM, if the next size tap drill is only a couple thousands larger, I'll use it instead of the standard one. As far as U.S. made there are a LOT of products that the fine print says made in USA from foreign sourced material so you have a tool stamped USA made with crap chinese or other foreign steel. BTDT. Aside that, a three flute gun tap is what I use on receivers and I go all the way through, no need to back out and the chips are pushed ahead of the cut.

 

[GenePoole]

Its a new stainless remington and I was tapping a 8-40 hole. The action felt hard from the start much harder than the last blued action I did. I think if I would have used power the tap would have went right away.

i just turn the mill by hand and never had an issue until now. I was at the bottom of the hole and went to go back up and bam. It was the rear flat of the action on the third hole counting from front to back on the action. Its been a shitty week so might as well add to it.

How are you prepping the old hole for 8-40? I find that the factory 6-32* holes are rarely in line. I've seen them vary from the action centerline by up to 8 thou. I set my action to the centerline with a ground dowel and bushings, just as I would in a lathe, then punch the holes with a 1/8" carbide endmill so that they do not follow the old hole. Then I ream to 9/64" (#28 is the spec drill size or 0.1405, but a 9/64 is 0.1406) with a chucking reamer. From there, the tap (with a guide and TapMagic) cuts like butter. I use an HSS tap with an H1 tolerance. Do all operations for each hole one-at-a-time with the table locked, then advance to the next hole.

Edit: 6-48

 

[AlNyhus]

After just breaking off a brand new 8-40 tap in a remington 700 reciever. I am looking for some recommendations on a new 8-40 tap. This was suppose to be a good tap and it was not cheap and I babied the damn thing the whole time and did it by hand. Each hole was taking about 30min. I was really cutting light and backing it out with lots of vipers venom.

I got to the bottom of the third scope base hole and go to turn it out and snap.

Now I get to deal with getting it out and I am not sure what I am doing about that yet. I have a couple more 8-40 taps but they are made by the same place so I dont even want to chance it.

Boy...somethings not right. I suspect that the tap seized on the way out and that's why it broke.

I have some 8-40 Sandvik spiral taps but they've been dc'd. The ones sold by MSC under their Value Series have been very good too. I don't do many holes with mine before I grab a new one so they're always sharp. You didn't mention the drill size used but a #28 or a 9/64" will clear the old 6-48 threads provided it's located dead on before being done. If there's any remnants of the old threads, that's another area where a guy can into trouble with these small taps. I was taught that the smaller the tap, the less you want to back it up when cutting...once I start it never gets backed up until it comes back out of the threads. Coming back up after the threads are cut things can get herky too...the tap can bind and snap if theres much swarf at all. Cleaning and relubing before coming out has always worked for me. For lube, 90 wt. gear lube with some moly powder mixed in works good..kind of my home brewed Moly D substitute.

Wayne Shaw tipped me to these guided tap handles from McMaster-Carr. The guide is 1/2" O.D. so it goes into a collet on the mill. They make one for the smaller taps and ones for the bigger sizes.

 

[ridgeway]

Walter spiral flute.

 

[dakor]

The customer wanted them 8-40 I would have rather left them as is.

The hole was drilled in the mill with a #28 bit like it said on the side of the tap. The book also says to use a 28.

This is the first tap I have ever broke in 14 years.

These taps are from Brownells and are 4 flute. I was just asking if someone had a tap they really liked for taping an 8-40 thread.

I am going to try a 2 flute after I figure out a way to get the broken piece out.

If I cant get it out without trashing the threads they will all be 10-32

 

[natdscott]

If I cant get it out without trashing the threads they will all be 10-32

Just take your time, man. Keep that frustration in check, or walk away 'til "later".

And at least there, you can work from both sides, as needed.

 

[boltfluter]

The customer wanted them 8-40 I would have rather left them as is.

The hole was drilled in the mill with a #28 bit like it said on the side of the tap. The book also says to use a 28.

This is the first tap I have ever broke in 14 years.

These taps are from Brownells and are 4 flute. I was just asking if someone had a tap they really liked for taping an 8-40 thread.

I am going to try a 2 flute after I figure out a way to get the broken piece out.

If I cant get it out without trashing the threads they will all be 10-32

I am sure you know this, but a carbide end mill is your friend when it comes to removing a broken tap. Slow feed rate by hand and high rpm works for me. Good luck.
Paul