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26th Apr 2021, 07:21 AM #31Most Valued Member
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I think John (shehappens) might be right. Your taps might be 'jap crap'. Buying a quality tap to compare is a good idea. Yes, HSS taps are much better than carbon steel.
Chris
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26th Apr 2021, 07:57 AM #32Philomath in training
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Whitworth threads have (or are meant to have) a rounded crest and root. From a manufacturing point of view, they are easier to make without that. If those tapped holes were made with 'proper' taps, it could be that the new taps are taking out the material that the radius would have left in - and shaving the rest of the thread to make that sloppy.
Michael
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26th Apr 2021, 09:45 AM #33
Just to throw a curly in do you have an SAE thread gauge?
To get a 1-2.5mm play is astounding. If there was that much crap in the threads I'd be concerened. Have tried a metric gauge on the thread?
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26th Apr 2021, 02:10 PM #34
The problem must have been a distorted thread maybe from over tightening ? As people have said in previous posts.
I Had the problem I mentioned earlier of trying to tap a part I'd made with the 3/8 16 Japanese Made tap . Well this morning I sharpened it as Baron J mentioned. But with a file not a stone. It worked but was also ruining the file . A triangular one .
The tap started working better but only got a small amount further through the test piece 10mm mild steel, even though sharper and well oiled. It stopped . It was jamming solid in its own hole , like it would had I sharpened it bad and made the leading edge smaller than what followed . I didn't do that though .
So I went searching and found I did have a P&N 3/8 16 BSW taper tap in an old box set that had lost its lid and a few of its sizes many years ago. It was a bit rusty from weld spatter, and one chipped tooth so I cleaned it up and sharpened it with a fine narrow grinding wheel . I also Grabbed a better Tap holder from another box and It was a breeze from that moment on !
worked beautifully . I cut my thread through the 19mm thick 4140 and then passed the Japanese tap through . It also went through well with no metal removal at all .
So I think that shows the cheap 3/8 tap is the right size and type and its just the condition of the used threads with the shaving off of metal when trying to clean a thread .
The worst one was the 1/2 inch on the cast iron part mentioned . So ill try the same test if I get a chance and have to tap a 1/2 hole .
Ill be getting some better taps and dies for sure .
IMG_7826.jpg
Rob
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26th Apr 2021, 03:22 PM #35Member: Blue and white apron brigade
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I've been buying HSS taps from McJing and I have found them to be pretty good.
When I made my grinder turntable I started to tap the 18 3/6" BSW threads used to hold the ballbearings on baseplate with a carbon steel tap from a cheap set I bought on line. Despite the liberal use of Trefolex, each hole got successively more difficult and by about the 5th hole I snapped the tap. Using a HSS tap from Mcjing it did all the remaining holes with no problems. Later I found on the base plate was made of Bisalloy. That same tap still works OK.
IMG_2910.jpg
Recently I needed to tap a 30 mm long M6 thread in some 316 but all my regular taps were only good for ~ 20 mm of fully formed thread. I found I hD a McJing M6 HSS gun tap which had reduced shank that allowed the tap to be driven in further to create about 24mm of thread. I then ground away more of the shank so it could reach the 30 mm mark.
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26th Apr 2021, 05:44 PM #36
Hi Guys,
Based on the description that Rob gave about his bolts and him saying that he had a large amount of play was a little misleading since the bolts that he described were only held at the end by the last 17 mm or so and from the pictures were at least 50 mm or more long, some wobble wouldn't be at all surprising !Best Regards:
Baron J.
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28th Apr 2021, 10:33 AM #37
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28th Apr 2021, 12:54 PM #38Golden Member
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28th Apr 2021, 02:53 PM #39Member: Blue and white apron brigade
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- Perth
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28th Apr 2021, 05:24 PM #40Golden Member
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- Oct 2008
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- Cairns, Q
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Bob,
I've also come across M6 (25.4TPI) retapped to 1/4 BSF/Brass (26 TPI).
Frank.
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