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Post by blackhawk7204 on Mar 22, 2009 10:13:25 GMT -5
I have a standard Savage breech plug that I recessed the vent liner hole and countersunk for the vent liner. Now I can't get a tap to cut the threads deeper so the vent liner will screw back in. I had no trouble drilling it but a normal tap just will not cut the threads. Is there a special tap used to cut threads in harder steel?  |
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Post by ET on Mar 22, 2009 10:53:48 GMT -5
Is all the carbon buildup removed from BP?
Are you trying to use a bottom tap?
Is this a used tap?
Recommend you get a new sharp 10/32 tap with a spire point and all should be well.
Ed
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Post by blackhawk7204 on Mar 22, 2009 11:00:36 GMT -5
It's a brand new breech plug but it is a used tap. Will a new standard tap cut it?
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Post by edge on Mar 22, 2009 11:19:56 GMT -5
I have a standard Savage breech plug that I recessed the vent liner hole and countersunk for the vent liner. Now I can't get a tap to cut the threads deeper so the vent liner will screw back in. I had no trouble drilling it but a normal tap just will not cut the threads. Is there a special tap used to cut threads in harder steel? When you say "normal tap", what do you mean? The breechplug is heat treated steel so it is not soft like a cold rolled steel. IMO, you may want to open up the hole since you can live with less than 50% threads! While a #21 (0.159) is fairly normal, you probably should go with a #20 ( 0.161) or even a #19 (0.166 ) I normally use a 2 flute gun tap in a machine, but if you are doing it by hand make sure that you use oil and only go 1/2 revolution(max) and back off to break the chip. If you break the tap and have been breaking the chip you have a chance to get it back out  Good luck  edge. |
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Post by rbinar on Mar 22, 2009 13:11:25 GMT -5
 8-)The 10ML plug can be tapped with a regular tap. Well at least if the regular tap is a plug or tapered style tap. Using a bottom tap will be much harder. Working on the theory a picture is worth a 1000 words here goes.  As you can see it's a lot easier if you put a couple of wood spacers in a vise and clamp it upright. A tap handle won't hurt any either. The best tap would be a TIN coated 10-32 (about $7 at MSC on line) plug tap like the shown at the in front of the breech plug. Using this type of tap I don't worry about re-drilling the plug I just tap the existing hole.
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Post by ET on Mar 22, 2009 13:46:31 GMT -5
I guess everyone has a choice for type of tap they prefer to use. Mine happens to be with only two cutting sides and find them more durable than the regular tap with 4-cutting sides.  This one in particular has already done 3-BP's with little effort and will do more. Ed |
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Post by Richard on Mar 22, 2009 18:38:59 GMT -5
I use a cobalt tap and they cut like a "hot knife thru butter!"
Richard
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Post by rbinar on Mar 22, 2009 19:49:30 GMT -5
I guess everyone has a choice for type of tap they prefer to use. Mine happens to be with only two cutting sides and find them more durable than the regular tap with 4-cutting sides. This one in particular has already done 3-BP's with little effort and will do more. Ed The two taps shown in the image I posted have cut at least 70 plugs between them. The one in the plug may have as many as 50 on it's own. However as Richard's post shows there is always a better mouse trap. |
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Post by ET on Mar 22, 2009 20:22:02 GMT -5
Thats a lot of plug tapping (50) with one tap. With the amount of tapping you do I can see why you would use such a quality tap.
My post was not intended to suggest the type of tap I use compares in any way to TIN coated tap you have. But would be a good cheaper secondary choice to consider for doing a smaller amount if cost was an issue.
Ed
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Post by ozark on Mar 22, 2009 21:23:32 GMT -5
The answer is that suggested by edge. The tap can only be turned a partial turn before reversing the rotation until you feel the chipl break and enter the flutes. Tapping without backing up frequently will result in clogged taps and often broken taps.
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Post by skin290 on Mar 23, 2009 7:19:12 GMT -5
I guess everyone has a choice for type of tap they prefer to use. Mine happens to be with only two cutting sides and find them more durable than the regular tap with 4-cutting sides. This one in particular has already done 3-BP's with little effort and will do more. Ed That one IS stronger than the others, has more cross section area...and if you are through tapping, does not need backing out, chips push out thru the front. To the OP's question, you need to check what the tap is made out of, some cheaper taps are just hardened carbon steel, with is fine for AL or just cleaning threads, but not fun for full-cut tapping of steel. It would be tough on harder steel to use, so try and find out if it is actually high speed steel. If it is, and breech plugs are non-hardened steel (even if they are soft tool steel or high alloy like 4140), you should have no problem running it in there, but use some kind of thick lubricating oil. I used the black sulfur stuff for a long time for most production work, but the best was always some really thick special tapping stuff, nearly to gel state it seemed. Thick motor oil SHOULD work in a pinch...just go slow, and if it doesn't feel like its actually cutting, back off and figure something else out...don't force it! (Have burned or drilled out too many taps myself!) You might just need a higher quality tap. If it is a standard "hand tap" you will need to back it off every couple turns to break the chip. |
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Post by blackhawk7204 on Mar 23, 2009 19:17:39 GMT -5
Well it took 2 new taps and a lot of oil even after using a larger than normal drill bit, but I finally got it threaded. The taps I get locally are just not tough enough for this kind of project.
I will get a better tap before I try this again!
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8-)The 10ML plug can be tapped with a regular tap. Well at least if the regular tap is a plug or tapered style tap. Using a bottom tap will be much harder.