Thread: Threading problem

Mike,
Glad you worked that one out before I tried to explain the differences in helix angles between 7tpi and 8tpi and different diameters. Internal threading really sux as you really need a different tool for every different tpi and diameter.
arrgh this sux I'm using my phone cause my pc just died. Damed windows!
Ewan

Yes I will look at the helix angle too ....

This stuff is so finicky ..the tool geometry has to be 100% correct , 90% isn't good enough .

What a learning curve .

Mike From the two pictures ,it looks to me that there is not enough front and bottom clearance ,so as you go deaper the bottom edge rides in the cut thread. there by lifting the front of the carriege,Just a thought could be wrong ,


Edwin.

Originally Posted by TKO

Mike From the two pictures ,it looks to me that there is not enough front and bottom clearance ,so as you go deaper the bottom edge rides in the cut thread. there by lifting the front of the carriege,Just a thought could be wrong ,


Edwin.

Ed

Yes maybe , I will check that out . I did regrind the tool . I should have left it alone when it was working OK .

Colour in all the surfaces of the tool with a texta and try again. That will show where it's rubbing. I think there's not enough front clearance. The diameter is a bit smaller than before.

Originally Posted by Bryan

Colour in all the surfaces of the tool with a texta and try again. That will show where it's rubbing. I think there's not enough front clearance. The diameter is a bit smaller than before.

Bryan

Good point about the diameter . The texta is worth doing as well

Mike

Originally Posted by TKO

Mike From the two pictures ,it looks to me that there is not enough front and bottom clearance ,so as you go deaper the bottom edge rides in the cut thread. there by lifting the front of the carriege,Just a thought could be wrong ,


Edwin.

I am with you on this.
I think its riding on the bottom edge as well as not having enough front clearance.
Mike, may I suggest grinding a radii under the cutting edge towards the bottom of the tool to give it clearance on the minor diameter of the thread (hole)
Maybe I should take a photo of the tool I used for doing the same job on my lathe.
Do not know if my camera would pick up the close up photo ?
Bruce

Ok Bruce and the others

Yes I understand . I have reground the tool . It now has much better clearance on the front and sides . I am sure it will perform OK now .

Mike

The reground tool

I still have to lap the tip on the diamond plate , its slightly wonky still , but the clearance is more pronouned now

MIKE

Looks to me like your helix angle is too small and going the wrong way.

Originally Posted by morrisman

The reground tool

I still have to lap the tip on the diamond plate , its slightly wonky still , but the clearance is more pronouned now

MIKE

Looking at the picture you will have to grind the bottom of your tool away a little so that it dosent rub.
If you have another threaded piece that fits your spindle place this tool in it at the correct position it would be in if cutting and see if it touches anywhere,if it does grind the tool until it dosent.

I did the clearance check on the actual Burnerd backplate thread . More than enough front clearance . Actually I'm worried the tip of the tool might break off as its rather thin now.

Helix.. Yes I've now adjusted it

Mike

Havent you ground the tool to suit the thread your going to cut?

Try more front rake on the tool and make sure you have the cutting point on centre. Also the top of the cutter seems to have a rake on it . Try a flat top as the front edge may be riding above the point . Tool grinding is an art in itself .