Tap and Die. What size handle do I need for a 1¼" BSP tap.

[Gromett]

I just checked. I was thinking of PVC for shattering. ABS doesn't shatter but is more expensive, and I don't think it the best for tanks for a few reasons?

 

[jockaneezer]

I was just curious really.
I was thinking you might have trouble holding the part to tap the thread into it as that HDPE is quite slippy and very soft, but if you get them welded into the bigger sheet first it should be no problem apart from the physical size of getting it under your drill press or what have you, as you've already mentioned.
I've got a component made from 20mm thick 4140 steel that needs welding for an M20 thread repair, just waiting on Amazon dropping off the fine pitch tap this afternoon, then I need the wife to go out while I preheat the whole thing in the kitchen oven !

 

[Gromett]

I was just curious really.
I was thinking you might have trouble holding the part to tap the thread into it as that HDPE is quite slippy and very soft, but if you get them welded into the bigger sheet first it should be no problem apart from the physical size of getting it under your drill press or what have you, as you've already mentioned.
I've got a component made from 20mm thick 4140 steel that needs welding for an M20 thread repair, just waiting on Amazon dropping off the fine pitch tap this afternoon, then I need the wife to go out while I preheat the whole thing in the kitchen oven !

ok, Got an update for you.

I had a break in computer work and decided to just beast it with the tap. I didn't mind if I broke them or made a mess of it as I was going to use them for test welds anyway and they wouldn't see a customer or any of my final pieces. For the smaller one I had already popped out, I just held the tap as square to the insert as I could tapped the top of the tap with a lump hammer to make sure it was engaged then ran it down without any oil and only doing the odd reverse. Reversing doesn't seem to help as it doesn't break the cuttings off and just reverses over them. It is 20mm thick HDPE so it held into the vice well enough and only marred it slightly.
I am making a jig to hold it fully which I should be doing tomorrow.

For the big one. I didn't remove it from the sheet. So the tabs held it down. I clamped it to the table and tapped from the back. I did the same trick with the lump hammer and then used a ring spanner to run it down without reversing it. I fished out the thread of hdpe as often as I could reach it.

The threads are not the prettiest I have ever seen, but perfectly functional and good enough for the job I am using them for.

For future ones I will get him to leave 4 tabs on the big ones to make it easier and more stable. I will use a little oil, and I won't reverse at all on the big one. I will do the tapping whilst still in the sheet.

I am sending that big handle back for a full refund. They had a chance to resolve it for the last 2 days and only had one communications asking for a picture of the label.

Not sure if you can see it in this picture or not. But the fittings to be used in the first tank screw in nice and snuggly. It will make for an EXTREMELY tough connection to the tank and will allow the fitting to be changed easily if needed.
I am EXTREMELY happy with how this little project is turning out.

 

[jockaneezer]

Looks like a win then and a good job you have a nice, new sharp tap as threading into plastic by hand can just end up in a cross threaded mess !
Still no sign of my Amazon tap and I've just spent the last half hour removing a broken M6 tap from this job, luckily the tools I got given from fellow Funster Mike a couple of years back included a 5mm tungsten carbide slot drill that gingerly got it out.

 

[Gromett]

Just spoke to the CNC guy and his going to add 2 more tabs and rotate them 45° Will make my tapping job soooo much easier.
Computer job is on a half hour break for him to get his lunch. So I went out and tested out the hole saw sizes on a spare piece to make sure the insert will fit in the proper sheets later. It is 10mm so quite a bit bigger than the 6mm.

But fits perfectly.

You can now probably clearly see what I am doing. The threads on the fittings are all 15mm long. Tapping a 6mm sheet to fit them would not give a good connection or seal.
These inserts are to give 20mm for the 15mm of thread and to spread the load across more of the tank to prevent damaging the sheet which would be hard but just in case.

It will even support heavy duty brass fitting now such as ball valves etc. Rather than the cheap plastic fitting normally used on motorhomes and caravans.

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[Gromett]

I was just curious really.
I was thinking you might have trouble holding the part to tap the thread into it as that HDPE is quite slippy and very soft, but if you get them welded into the bigger sheet first it should be no problem apart from the physical size of getting it under your drill press or what have you, as you've already mentioned.
I've got a component made from 20mm thick 4140 steel that needs welding for an M20 thread repair, just waiting on Amazon dropping off the fine pitch tap this afternoon, then I need the wife to go out while I preheat the whole thing in the kitchen oven !

Just saw the bit about getting rid of the wife so you can abuse the kitchen. Love it

 

[Silver-Fox]

Gromett

If it were me I would get the large tap ground down a bit more at the end for an easier start.

You can pick up pillar drills cheap secound hand.
It doesn’t even need to work

 

[Gromett]

Gromett

If it were me I would get the large tap ground down a bit more at the end for an easier start.

You can pick up pillar drills cheap secound hand.
It doesn’t even need to work

It went in really easily to be honest. I think the pictures are a bit deceptive. There is quite a few thread worth of taper.

When I say I tapped it with a lump hammer I was perhaps over egging it a little

 

[Silver-Fox]

When I say I tapped it with a lump hammer I was perhaps over egging it a little

I’ll be honest when I read that my legs went a bit like jelly