What size screw is this?

[YYCHM]

I need to replace two screws on my bandsaw. I'm assuming metric.. maybe. The threaded portion measures 0.234" (6mm?) OD and looks to be 20 TPI according to my SAE thread gauge. I started looking through online screw charts but got dizzy real fast. Is there an online screw calculator that would solve this mystery in a less pain full fashion?

Thanks

 

[John Conroy]

Most of the screws on my Taiwanese bandsaw are sae thread. It's probably 1/4" 20 tpi. 20 tpi is almost exactly metric 1.5mm thread pitch but m6 X 1.5 is pretty rare, the common thread,pitch for m6 is 1.0.

 

[PeterT]

Not sure about where your bandsaw originates from but its unfortunately quite common to have a mish-mash of imperial & metric fasteners on machines these days of Asian origin or outsourcing. The OD isn't a great indicator because often times the fastener isn't well made. Or as John says there are certain combos that are quite close to one another & if you assume wrong then its possible to bugger up the threads. If you don't already have a screw pitch gauge, they are a good investment.

There are many thread tools on the net but I use this one a lot. It shows the tolerances & comes in handy when designing & cutting threads particularly.
http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx

 

[Chicken lights]

I have a selection of SAE and metric nuts at the shop. I just try the nut on the mystery bolt until I find one that threads on nicely

Or I’ve used a thread chaser to do the same thing, especially if it’s metric

 

[YYCHM]

And the winner is...…….. 1/4-20.

 

[YYCHM]

The screws I need to replace hold the guide(foot) plate when using my band saw in the vertical.

The problem is they seat proud. They seat proud on the large plate (bottom of the image) as well.

I picked up some replacements and attempted to mill the heads down but by the time the head was reduced enough to sit flush nothing was left for the screw driver to engage.

What's the solution to this? Different kind of screw? Thicker guide(foot) plate?

 

[PeterT]

I have the same thing. I can see where they hand ground the heads to make them flush-ish. It’s a design problem. The solution I envision is a thicker plate or a sub plate somehow tacked or attached underneath to allow deeper counter sinks. Because minimizing the screws seems more pita.

 

[RobinHood]

This educational video from days long ago shows different flush riveting methods used in aviation. Instead of rivets, countersunk screws could be used with an appropriate nut plate or a threaded hole.

Perhaps you could adapt your bandsaw guide using one of the demonstrated methods?

 

[John Conroy]

I just made a larger thicker plate to use when the saw is in the vertical position.

 

[Johnwa]

I made my table out of ⅛” aluminum plate. I placed the screw in the hole over a suitably sized nut on an anvil and hit it with a hammer. It formed the dimples quite well.