Screw Thread ID

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Ed McDonnell

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I'm trying to id a screw thread. The major diameter is 7.09mm / 0.279". It's a perfect fit with an 18tpi gauge (which would be around 1.4 metric pitch). Looking for a tap:

M7x1.4 is not something I could find off the shelf
5/16-18 is too big.
9/32-20 won't work.

Anyone recognize this thread and know where I could find a tap? Having a custom tap made would not be worth it for this project.

I am making some Berea pizza cutters for holiday gifts. I was planning to use a metal / resin blank with the cutter frame screwing directly into the metal part and not using the threaded insert included in the kit. Using epoxy to set the insert in the metal doesn't seem like a very good solution to me. Maybe I'll just have to switch to some segmented wood handles instead.

Berea was no help. I suspect they are just reselling a kit they buy in bulk somewhere and they didn't do the design.

Any and all help appreciated.

Ed
 
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vtgaryw

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It doesn't even show up on any of the standard tap charts or at McMaster. It's got to be a special.

I've wanted threaded inserts of odd sizes before too (for a semi-kitless pen project.) They don't seem to be generally available without just cannibalizing a kit. I'd love to know of a source for these oddballs too.

Gary
 

gimpy

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if it is some thing you could carry into the hardware store, they should be able to figure it out for you
 

Woodchipper

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Try an industrial supply company or fastener distributor. They should have a thread gauge to determine the diameter and thread pitch, exactly. I have one from my sales days. Handy as a pocket on a tee shirt. Lowe's has one on the wall in the fastener section- if you have a store handy.
 

Ed McDonnell

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Can you chase the male threads with a more comon die? I’ve done that before if you’re close.
Hi Bruce - I was hoping that might work, but it's not close enough to anything common to make thread chasing an option. I also thought about making a jig to hold the part and machining it to 1/4-20, but that's more work than it's worth.

Ed
 

Ed McDonnell

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Try an industrial supply company or fastener distributor. They should have a thread gauge to determine the diameter and thread pitch, exactly. I have one from my sales days. Handy as a pocket on a tee shirt. Lowe's has one on the wall in the fastener section- if you have a store handy.
Hi John - I have sae and metric gauges and was able to figure out the thread pitch and diameter. It just wan't anything I had seen before.

Thanks,

Ed
 

Ed McDonnell

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It doesn't even show up on any of the standard tap charts or at McMaster. It's got to be a special.

I've wanted threaded inserts of odd sizes before too (for a semi-kitless pen project.) They don't seem to be generally available without just cannibalizing a kit. I'd love to know of a source for these oddballs too.

Gary
Hi Gary - The closest thing I could find is a 9/32-20. And it was only the tap. There was no matching die. I've got a lot of different oddball taps I've acquired over the years to use for pens. They can be crazy expensive to have made. A M7x1.4 or 9/32-18 would probably do the job. Definitely not worth having made for this project. I could also try making my own custom tap, but I'm not willing to put that much work into something I'll only use once.

Thanks,

Ed
 

More4dan

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monophoto

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Berea was no help. I suspect they are just reselling a kit they buy in bulk somewhere and they didn't do the design.

I've never bought anything from Berea, and based on Ed's experience, I never will.

Problem 1: as consumers, we should be expect vendors to support the products they sell us, and if they won't/can't, then there are alternate products from other vendors.

Problem 2: using a non-standard thread is a really dumb design. The pizza cutter assembly clearly is manufactured, and cutting threads in the mounting stud is part of that manufacturing process, but I'm sure that it would have been less expensive to source standard threaded inserts, and then specify that a matching standard thread be machined into the cutter.

Problem 3: the best way to install threaded inserts is to screw a matching bolt (or a threaded shaft with a nut) into the insert, and then use a hex driver to drive the insert into the wood. Using a screwdriver, as suggested in the instructions for this kit, is a great way to bugger up the insert while still not driving it into the wood.

Problem 4: Berea Hardwoods like to sell wood, but they would sell more kits if they designed them to work easily with plastic materials as well as wood.
 

Ed McDonnell

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Hi Danny - I made a tap after reading your post back then. Never said thanks, so a belated thanks. It worked ok on wood and resin. Not so good on metal. I suspect I didn't get the heat treating right. I ended up getting it stuck in a piece of copper and made a pretty good mess of things trying to get it out. I'm going to try making a tap again some day, but not for this project.

I thought about using epoxy or alumilite to cast the threads, but the threads on this cutter frame are rough and I don't think the plastic threads would hold up to very many handle removals.

The threaded stud on the cutter frame has flats on two sides. Almost like it might be capable of self tapping. Maybe I'll try using one as a tap and see what happens. If I bung up the threads I can always just epoxy it permanently into the handle.



Ed
 

Ed McDonnell

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Hi Louie - Overall, I've been satisfied with the products I've gotten from Berea. These pizza cutters are probably one of the least satisfactory Berea products I've dealt with. I only paid $6 for them and I think they are worth that (but not any more). I wouldn't be surprised to see Berea drop the kit or change over to a new kit from a different supplier.

Ed
 

wolf creek knives

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Can you chase the male threads with a more comon die? I’ve done that before if you’re close.
This is what I do for some of the knives I buy. I've contacted the manf. about the scale screws without any results. Went to a hardware store, bought a drill bit, tap and die and now have custom threaded holes that I can thread a brass rod in. Saves me a bunch of time and a lot of headaches.
 

More4dan

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Hi Danny - I made a tap after reading your post back then. Never said thanks, so a belated thanks. It worked ok on wood and resin. Not so good on metal. I suspect I didn't get the heat treating right. I ended up getting it stuck in a piece of copper and made a pretty good mess of things trying to get it out. I'm going to try making a tap again some day, but not for this project.



I thought about using epoxy or alumilite to cast the threads, but the threads on this cutter frame are rough and I don't think the plastic threads would hold up to very many handle removals.



The threaded stud on the cutter frame has flats on two sides. Almost like it might be capable of self tapping. Maybe I'll try using one as a tap and see what happens. If I bung up the threads I can always just epoxy it permanently into the handle.







Ed


Copper can be tough to thread even with a traditional tap. A former tap might be a better solution. Good luck finding those in a specialty thread though. It bends the material instead of cutting.

Why do you want to be able to remove the handle? I guess it would allow you to wash in the dish washer. JB weld and some other high temp epoxies are good to high temperatures (450 F) and would withstand the DW temps. With metal to metal you don’t have to worry about using a clear epoxy.

Danny


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Ed McDonnell

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Hi Danny - My plan for the handle was to have a metal core that I engraved / carved and then encapsulated in clear resin. I'm concerned about how clear PR will hold up to a dishwasher over time. And I know for sure that aluminum / brass doesn't do well in a dishwasher.

After sleeping on it, my current plan of action is to bore out a snug fit recess for the threaded insert then epoxy it into the end of the metal rod. Not an optimal solution, but it will have to do.

Ed
 

More4dan

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Hi Danny - My plan for the handle was to have a metal core that I engraved / carved and then encapsulated in clear resin. I'm concerned about how clear PR will hold up to a dishwasher over time. And I know for sure that aluminum / brass doesn't do well in a dishwasher.



After sleeping on it, my current plan of action is to bore out a snug fit recess for the threaded insert then epoxy it into the end of the metal rod. Not an optimal solution, but it will have to do.



Ed


JB Weld might still be a better adhesive for the insert if it did make its way to the dishwasher without removal. Had a friend repair the head on his outboard motor with it. Lasted several years.


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