Tap Follower – Part 1

By Grover Koelpin 6 comments


In my most recent Watchmakers Faceplate video
I needed a tap follower to make sure the threads attaching the two parts together were dead
straight. I haven’t been able to buy a tap follower small enough for the chucks on my
small machines, so I thought I’d try making one based on the design Phil Desjardins and
Pierre Beaudry made for Keith Fenner’s What’s In Your Box tool giveaway. I sketched out the rough dimensions I thought
would work, decided to make it from silver steel, and try making something with the ER20
collet chuck for the first time. My design isn’t quite the same, but that’s down
to me misunderstanding Phil and Pierre’s videos and not because I intentionally modified
it. My first step was to clean up a length of
10mm stock for the tool body. I then centre drilled one end, and drilled out three diameters
for the main features. The first is a 5mm through hole for the tool
tip. The second diameter is a 6.5mm chamber for
the spring. The final diameter is the 7mm tap diameter
for the M8 thread that holds the end cap in place. The thread was tricky to tap for a few reasons.
Firstly I didn’t yet have a tap follower, so had to constantly adjust the tailstock
to keep the tap straight. Secondly I don’t have a tap wrench large enough for this tap,
but short enough to swing full circle above the lathe, so I had to make do with the small
swing space available. Thirdly I can’t lock the lathe spindle, so had to use a wrench
to hold the collet chuck. Fortunately it didn’t need to be tapped
very deep. With the thread cut I moved on to a new piece
of stock to make the end cap. This needs to be screwed in firmly, but undone by hand,
so I started by knurling the outer diameter. This is my first ever knurl, and I screwed
it up pretty badly. The most major mistake was failing to tram the toolpost. Fortunately
this was extremely obvious by looking at the result of the first pass, so I stopped to
set the toolpost to 90 degrees. The second mistake was failing to use cutting
oil. With the tool post straight, and cutting oil
applied, things went much better. I’m pretty happy with the result. I then turned down a short length to 8mm for
the thread. The final step before threading was the same
5mm through hole. I drilled a little deeper than necessary to make parting off easier. As before I’m using the thread technique
I learned from Joe Pie. The lathe is run in reverse, with the feed screw moving the carriage
away from the chuck. This allows the lathe to run much faster without fear of crashing,
and also allows the thread to be cut very snug against the top of the cap. I used the thread tool itself to cut the starting
groove, as close as possible to the shoulder. Out of shot I set up an indicator to mark
this starting position, so I could return the carriage to exactly this spot. I set the
compound to match the 60 degree thread angle as usual for single pointing. I then found the outer diameter using the
tool, and ran it back and forward to clear the burr from the edge of the groove. The first scratch pass was pretty slow, but
everything seemed to go smoothly. After a few passes I got more confident and
increased the lathe rpm so the insert would cut more cleanly. Towards the final pass I started to see a
problem. At my carriage start position, the tool point was no longer aligned with the
starting groove. Advancing the compound at 60 degrees has caused it to loose alignment
as the thread progresses. Looking back at Joe Pie’s video, he does it with the compound
at 90 degrees for exactly this reason. If I’m going to use this technique with the
compound at 60 degrees, I need to progressively adjust the carriage start position to compensate. It’s a pretty good fit, sits snugly against
the end. With the thread cut to depth, I returned the
compound to the starting position, and run the tool along the original diameter to remove
any protruding burrs. Finally I faced the top of the cap to remove
parting tool marks, with it screwed into the tool body. The tool body is now complete, and this is
probably enough for one video. Look out for part 2 where I’ll show making the reversible
tool tip.

6 Comments

Colin Creed Tattoo Machines

Nov 11, 2017, 5:59 pm Reply

Nice start, Well done!!

Hans Schmidt

Nov 11, 2017, 7:36 pm Reply

On small lathes, I like the manual approach on threading, particularly in a situation like yours. It is slower but gives precise control. This gentleman illustrates a nice hand-crank mandrel for this purpose. https://youtu.be/2pDGQjaBbJA?t=1m58s

R. Steven Lang, Shark River Machine

Nov 11, 2017, 3:38 pm Reply

I always enjoy your builds as I also use a small lathe.

f preston

Dec 12, 2018, 7:33 pm Reply

Nice video . Better without the music

Dima Kuroedov

Nov 11, 2019, 11:20 am Reply

Thanks! A have a proxxon 250 too. I want to make this tool. What a material you use?

Dean Harris

Dec 12, 2019, 2:33 am Reply

Spaceman Spiff approves!

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