Can a chaser from a die head be modified to cut internal threads.

[WindyParticipant @windy30762]

Can a chaser from a die head be modified to cut internal threads?

Have seen them used in a holder for external threading.

Its for large internal threading I suspect might have cut off some of the die chaser and might have to regrind some part.

Anyone made an internal thread cutter out of a die chaser or are there angles wrong.

[WindyParticipant @windy30762]

Can a chaser from a die head be modified to cut internal threads.

[peak4Participant @peak4]

I've not fully thought this through, and it's too cold in the workshop now, but would it need to be a left hand chaser to cut on the front of the hole, or a conventional one to cut on the rear, with the lathe running backwards?

I'm thinking about the helix angle of the teeth, but maybe not thinking hard enough.

Bill

[Anonymous]

I suppose it could be done but seems a complicated solution to a simple problem. A chaser only cuts on the front chamfer. The remaining "teeth" are forward (on an external thread) of the cutting line and are used to pull the diehead forward. On an internal thread those "teeth" would interfere with the already cut thread. So they would need to be ground back. Tilting the chaser will not work as it will mess up the helix angle.

Andrew

[Nigel Graham 2Participant @nigelgraham2]

If you need modify the chaser, especially as Andrew describes by turning into a single-point tool, you are giving yourself extra work and ruining the thing for its intended use.

Use a proper internal-thread cutting tool, either singe-point or an internal chaser.

There is though an old dodge as a chaser, of using one flute of a tap held in a holder like that made for round-section boring-tool shanks. This of course for diameters much larger than the tap, but with the same thread-form and pitch.

[Mike PooleParticipant @mikepoole82104]

I think the front clearance and top rake would be incorrect even with a large diameter internal thread. Front clearance is probably the most difficult to correct. An insert type tool may be useful for a ready made solution with the fiddly angles sorted out for you. Grinding a boring tool with a HSS bit is not too hard but seeing what I am doing is needing more assistance these days.

Mike

Edited By Mike Poole on 16/12/2022 22:54:49

[HopperParticipant @hopper]

Seems like it would be much easier to use a tap clamped in a holder whole, or a section cut from a tap and silver soldered to a boring bar shank, to cut an internal thread. That is what taps are designed for: internal threads. Clearance angles and helix angles will be correct for an internal thread.

Does my head in trying to imagine it from the armchair, but it seems to me that the helix angle on a die head chaser will always be wrong in relation to the cutting edge for cutting an internal thread.

[WindyParticipant @windy30762]

It was just a chance there might have been a way to modify one.

As far as cost of a die head chaser some years ago at a car boot I payed about £10 for a die-head and 11 complete sets with some single chasers thrown in.

Using a tap was a thought more so now as I purchased a tap on Ebay for £14 but the seller had made a mistake as was not the 30mm size he said it was.

I was refunded and told to keep the 32mm x 1.5P it still had plenty of life left.

As I have few smaller 1.5p taps might be able to use one of them in a suitable holder like Hopper suggests.

My work is now on full size stuff as model hydro's is in the past due to health issues due to going into a lake to launch am still in communication with some of the model hydro members distance is also another reason.

As a show the full size speed members might be interested in February 2023 a show mostly under cover with many speed attempt machines on show including the restored Bluebird.

For more details have a look at my club Straightliners website this link was last years show they also as a surprise did my 80th birthday party their for me..

https://www.facebook.com/StraightlinersNewsChannel/videos/1395737190880587

[Mick B1Participant @mickb1]

Seems to me it's way more trouble to mount the chaser – or part of it – than to grind a singlepoint threading bit out of 1/8 or 3/16 square HSS to fit a vanilla boring bar, gauging the flank angle from a suitable pitch gauge and stoning a flat or radius on the tip as appropriate to the thread form. But perhaps we all have a preference for the methods we're used to.

[duncan webster 1Participant @duncanwebster1]

Using a tap in a much bigger diameter hole will have the wrong helix angle even for the same pitch, so it still might not work. As others have said, grind up a single point tool.

[WindyParticipant @windy30762]

I thought helix angle would be a problem have a look at Cromwell tools  metric internal chasers and looks as if no helix angle..

 

Edited By Windy on 18/12/2022 13:01:15

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