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By Oskar Sedell
#1206329
I´m about to make cap irons for a couple of tapered plane irons (and then make wooden planes, using these irons).

Anyone know of a good source for the old school style cap iron screw? the ones with big, slotted cylindrical heads. I figure it is clever to find the screws first, and then the corresponding tap.

Maybe there are industrial sources, do you know if this type of screw has a special name to search for?

Looking forward to your input!

best regards,

Oskar
By Cheshirechappie
#1206334
Search for "cheese head machine screws". You may have to try one or two different sizes to find the one that has enough meat in the head to not drop through the slot in the iron. Most of mine seem to be in the 3/8" (10mm) diameter on the threaded part, but some look to have extra-large heads compared to a commercial machine screw.

They do vary though - one of mine uses a round-headed brass machine screw. I don't think it's original - but it works!

Edit to add - looking in Machinery's Handbook, it could be that Pan Head machine screws will be even better; for an M8 screw, cheese heads are 13mm diameter on the head, pan heads are 16mm.
For an M10 screw, cheese heads are 16mm diameter on the head, pan heads are 20mm.
For an M12 screw, cheese heads are 18mm diameter on the head, pan heads are not listed.

In each case, the M8, M10 and M12 refer to the outside diameter of the thread.

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Another possible route might be to source secondhand double irons, or secondhand cap-irons with their screws.
By D_W
#1206391
They are sold by industrial supply here knurled and slotted as "thumb screws". You may need to cut the bolt length down and chamfer the end.

Search:
Slotted Stainless Steel Low-Profile Knurled-Head Thumb Screws

https://www.mcmaster.com/#knurled-head-bolts/=1bgai6r

Nothing is cheap if you buy only one. It costs about the same amount to buy an entire used cap iron online.
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By DTR
#1206397
Make sure you pay attention to the screw length. When I replaced the iron in one of my planes with a thicker one, I discovered that the original screw wasn't long enough to engage with the cap iron. I made a longer replacement screw myself, but I appreciate that's not a luxury available to everyone. Since you're making your own cap iron, you can at least dictate what screw thread you use. If you go Metric instead of Imperial you will have many more "off the shelf" screws available to you.