To Tap or to cut 1.25" x 7TPI internal threads?

[WobblyHand]

Was this mine ? It sounds familiar !

Yes it was. Thanks again for the loaner!

I have since purchased an A12NEL3 LH bar for myself and have used it to make two lathe spiders. One spider was to finish the one for my mini-lathe, the second was for a new spider for my 10x22 G0602/G0752Z. Sure made the job easier!

 

[WobblyHand]

I must admit, my experience with smaller taps quality has been hit or miss. Even when I purchased from Grainger! I have hand tapped a LOT of 1/4-20 holes, 8-32, 6-32, 4-40 and a few slightly larger in steel as well as Al. All the taps eventually wear out, but some last longer than others. I have thought about trying to set my mill up for power tapping, but it is difficult to make this conversion. IT is just an induction motor without phase information being driven via a VFD. So the speed varies.

I once had a 1/4" thick SS 4' x 8' optical table. It came with 1/4-20 tapped holes on 1 inch centers for attaching optical mounts. However the manufacture's tap must have been very dull as we could not get screws into the holes. I had to re-tap so many of the holes that I set out to just hand re-tap them ALL. It took a long time. And of course I was interrupted/startled at one point and snapped the tap tip off. It was not sticking out enough to grip, just enough to be in the way. Fortunately, with the assistance from a good machinist tech we/HE got it out!

There seems to be a lot of ~$20 big taps for sale. Not from Grainger! I am sure they are not the best, but .... What do you think of tools from Tractor Supply? They have a titanium nitride coated Mibro 1-1/4 in. -7 NC Plug Tap for only $20. !!??? I have never purchased from them as it is a drive. I see that Mibro is a big Chinese company, but many US retailers (box stores) sell their tools. It might be good enough to run through the turned threaded hole for clean up? https://www.tractorsupply.com/tsc/product/mibro-1-1-4-in-nc-plug-tap-1183312?store=2307

I will have to pay more than the price of a tap for each of the threaded rods. So the price is not really the biggest concern.

I built a proximity stop for my lathe when I was doing the VFD conversion. So I have this feature. It works very well.

Yes, I should probably buy the threaded rod before I start making the threaded holes. I may have to buy a die just to run over the threaded rod.

Dave L.

If I understand correctly, you'd be single pointing open through holes. So a proximity stop isn't even required. Just eyeball it.

How many holes are you going to do? Do the pieces fit in your lathe? If it were a lot, I'd be tempted by a HSS tap, most definitely NOT by a carbon steel one. If only 4-8, I'd single point them. It doesn't take long to do. Your lathe is capable, and so are you! I've read your posts, you are definitely capable of doing this.

Beats me about Tractor Supply taps - never used them, hope not to have to. I find it tough to believe they'd be great, could be ok, or a total waste of your cash. I haven't purchased low end taps in a while now, having experienced dull and snapped HW store one's. Some of the low end one's were not true to size, so I swore them off. (They were oversized, known good screws rattled in the threads.)

I hemmed and hawed doing my first internal blind threads, since I was using a Micro100 solid carbide tool. and I had snapped a carbide tool a week before. Just "screwed" up my courage and did it. 'Twas a little nerve wracking in the beginning, but really, single pointing isn't hard at all. Just have to start doing it.

 

[RaisedByWolves]

I would be a little suspicious of a 1 1/4" tap that has an asking price of $29.95. Over the years I've purchased dozens of taps online and never seen a quality brand of that size with a price like that.

A good source for quality taps online is Zeitlin Industrial Supply on eBay. They currently have a listing for a WIDA 1-1/4-7 hand bottoming tap listed for $86.99. That's about the least expensive quality tap I've seen of that size.

WIDIA 1-1/4"-7 HSS Hand Tap 4 Flute H4 Bottoming Tap USA Made | eBay

Chamfer ‎1P-2P. Cutting Edge Material HSS Series/List # 5303 | 2303. HIGH SPEED STEEL HAND TAP. Tool Type Hand Tap Thread Size ‎1-1/4″ - 7. Overall Length (OAL) ‎5-3/4″ Cutting Direction (HAND) Right Hand.

www.ebay.com

As a side note I have had to hand tap 1 1/4-7 holes in DOM tubing for tie rod ends on construction machinery. It was difficult to say the least.

So far neither of the taps shown are the proper type of tap to do this job by hand.

I was wondering why everyone was saying to do this by hand would be difficult or too difficult, and with the wrong tap....yeah OK.


The taps shown are both plug taps and really not that good for hand tapping regardless of the hole size.

You ideally want to use a start tap for this type of job. It will align its self better and take less effort to turn. I've done threads this size by hand with an 18" Starrett tap handle.

 

[RaisedByWolves]

They do exist. Back in 2014, I bought a new Butterfield 1-1/8 x 16 tpi tap for $15 on eBay.

Yeah, I don't understand equating the price of an Ebay tap to quality.

 

[Charles scozzari]

The point was that you can find amazing deals on eBay (or other marketplaces). I wouldn't shy away from a deal just because of a low price. My philosophy when buying something that seems too good to be true "can I afford to lose the money if it turns out to be trash". I have a collection of used USA made taps purchased for rock bottom prices at hamfests over the years that are far better than any of the imports that I have.

As to breaking a 1-1/4" tap, I wouldn't want to meet the gorilla that did it.

Hi, my thoughts were not on breaking a 1 1/4" tap but were intended to the quality and the condition of it in general. As you stated there are a lot of tooling on Ebay if you know what to look for in the tool or tooling you are buying. Thanks.

 

[Ulma Doctor]

The point was that you can find amazing deals on eBay (or other marketplaces). I wouldn't shy away from a deal just because of a low price. My philosophy when buying something that seems too good to be true "can I afford to lose the money if it turns out to be trash". I have a collection of used USA made taps purchased for rock bottom prices at hamfests over the years that are far better than any of the imports that I have.

As to breaking a 1-1/4" tap, I wouldn't want to meet the gorilla that did it.

Amen

 

[Illinoyance]

Single point the thread. Make the boring bar if you don't have one suitable. Grind the tool bit. After single ponying do a clean-up pass with the tap.

That guarantees the tapped hole eill be true to the work, and on size.

 

[Illinoyance]

Definitely single point it. It will be true to the work. Use the tap to clean up the threads. It is no fun driving a 1 1/4-7 tap by hand.

 

[B2]

Thanks again folks for all of the advice and info.

Yes, the A500 is the post/Tube and Pipe steel. Thanks for bring this up. I know that some of the post jack threaded screws and collars are made from ASM 1215 steel. It is suppose to be machinable, but not the strongest against tension. However, these, as are in my design in compression, not tension. But the stress on the threads must be a combination of tension and compression forces with some shear due to the thread angle.

Yes, I agree a starter tap is a much better shape.

Yes, I see no reason to purchase a used tap. Even if it is a good brand, it is just the luck of the draw that it is not worn out. I would probably never use this tap again. So it just needs to make it through the 12 holes, which is not insignificant if the tap is not started straight. I commonly use the Mill to align and hold the tap perpendicular to the hole, but I do not have the ability to power tap. (envy!) Anyway, I will probably turn the hole and use the tap to clean up.


The first comment brings up another issue for me to think about more. Just how thick should this threaded hole piece of metal really be if it is made from ASM 1215 steel, which is what some of the commercial jack post use. The issue is how much thread engagement of this 1.25 by 7 TPI rod and collar is really needed? My numbers would indicate that more than the diameter of the threaded rod, 1.25", would be over kill. So maybe the single through hold for the threaded rod at the bottom dictates this and should be 1.25" thick rather than just 1 to 3/4". The pair at the top might be overkill, except this threaded rod pair are long in order reach through the floor joist to the start of a middle tube/post.

These threaded rods etc are part of a post assembly forming a column. The column post is actually three stacked posts which go from a basement footer to second floor roof beam. I'm changing the construction from two original roof assembly support walls to two beams with posts at the ends. There is not actually going to be much load on them ( a couple thousand pounds each at the most, unless there are extreme winds (>90mph) when the load might go up by 3,500 lbs/ post. So a total static plus dynamic load of ~2000# +3,500# per post. So it would be unreasonable to think a post load would ever be more than this. The posts thread through the walls and are hidden on the first floor. A total distance of about 29 feet is covered by the assembly. At each floor there will be bracing to prevent the post from bucking sideways where they join. The pair of threaded rods are use at feed between two spaced 2x12s to support the start of the middle post/tube. There are four of these, each one custom to fit the location. The posts will support some large LVL beams, that I hung at the roof years ago .. waiting for the posts. , These then support the roof rafters .... mostly during a wind storm. These original assembly walls, that I am taking out were constructed from ~12' ~ 14' long, 2x4s on 16 inch centers, without any cross bracing and no covering such as plaster! Without cross bracing a 2x4 wall of this height supports very little before bucking. So I am sure that they have never seem much of a load. They were probably use initially just for construction of the roof joist. And they did not even sit on a wall below, just the floor that was supported by floor joist. So am skeptical that this 94 year old house has ever seen a 90 mph wind. The roof structure is a strange design, sort of a Queens Trust design, without much bracing. But it has been holding up a slate roof for a long time. Anyway, I think I have over designed this thing in order to ensure that it last another 100 years.

Dave

 

[metalmaster1]

is it possible to just weld a nut to the plate after drilling a clearance hole?