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Crown Reversing Tapping Head Instructions

Assistance Needed

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Mike Hulme08/02/2019 21:35:45
13 forum posts

Hi, I have acquired a Crown auto reversing tapping head to tap some very small holes in stainless steel. However it came without any instructions and I am unsure how to test and adjust it.

Has anyone used one of these, or even has a manual/instructions for one?

I would be very grateful for any assistance.



Emgee08/02/2019 22:39:56
1149 forum posts
206 photos

Hi Mike

If the head has a clutch so you can pre-set power transmitted it will help reduce tap breakage.

Very small holes in stainless is not the best place to start using a new tool, best try it out on some aluminium plate, but start using say a 5mm tap with through holes to get some feedback on how it behaves, it may be wise to drill the holes to suit 50% thread engagement to begin with.

The smallest size I have tapped with a Tapmatic is M3 at 700rpm using spiral tap in aluminium with 2.5mm hole,
I would be very nervous if having to tap 70% engagement blind threads in stainless.


Mike Hulme08/02/2019 22:59:36
13 forum posts

Hi Emgee,

Yes, it has a clutch, but I am not sure how to adjust it, This tapping head is quite old, and I have never used one before.

I need to tap 1,6mm holes through 1.5mm steel to accept allen bolts. Eventually these will become reed frames for a concertina I am building.

I've seen several youtube videos, but none explain when to adjust the clutch for the best feed.


Emgee09/02/2019 22:03:14
1149 forum posts
206 photos

Hi Mike

A few pictures may help to solve the problem of clutch adjustment, normally there is a knurled ring that rotates to align various numbered indexing positions depending on tap size, clearly the smaller diameter tap the less torque is applied before the clutch disengages to prevent tap breakage.

With such small threads with through holes in thin plate there will be very little load on the tool, perhaps not sufficient to disengage any clutch on the tool, especially if you keep the rpm low so you can reverse the quill before the tap reaches full flute length. In the tap drill chart I have tapping drill size is 1.25mm for M1.6 x.35

Using the M1,6 with 0.35mm pitch will only provide 4 threads in the plate, so only for light fixing, best to use some kind of thread locking liquid (Loctite or similar) to increase the joint strength.


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