Reading the spider build thread has me thinking. Would it be better to use a very fine thread for spider adjustment screws ? It seems to me that the finer the thread the easier it would be to fine adjust the dial in of the bore. A bigger turn resulting in less movement of the bore. We’re not going to be having to start the threads repeatedly so after setting up the spider we’re just running the screws in and out a little. What’s the benefit of a coarser thread ? Would 1/4x32 or higher be better than 1/4x20 ? How about making your own screws at something like 1/4x48 or higher on the lathe ? Just exploring the ideas.
Threads for spider screws
- Thread starter Shrek
- Start date
Doug Beach
Silver $$ Contributor
Mine are 3/8-24, I have no problem making very fine adjustments. The equivalent rotation to 1 minute on a clock is only .0007”, and that adjustment is being made a long way from the chamber area, so your movement there is much smaller.
Short answer would be yes. The ;finer the better to make it easier to make fine adjustments.
Think of it this way. A 20 TPI will travel 1/20" or 0.050" of an inch per revolution while a 32 TPI will travel 1/32" or 0.03125" making it much easier to make fine adjustments.
Think of it this way. A 20 TPI will travel 1/20" or 0.050" of an inch per revolution while a 32 TPI will travel 1/32" or 0.03125" making it much easier to make fine adjustments.
Grizzly has some nice tipped 3/8"-24TPI bolts that are designed for just this purpose. They normally cost $16.95 for a package of 4, the are on sale right now at $4.95.
https://www.grizzly.com/products/Ba...qh31D0dxgpCHeMmvZouVhtCYiZzZ8n3xoChIAQAvD_BwE
https://www.grizzly.com/products/Ba...qh31D0dxgpCHeMmvZouVhtCYiZzZ8n3xoChIAQAvD_BwE
I have two of their spiders with the bolts in them. I’m just exploring the idea of finer threads for the purpose.
Dusty Stevens
Shiner
Finer the better. And the bigger the better- easier to put tips in and such. A 1/2-40+ would be my choice if i still worked in a machine shop and could make screws and taps. The 3/8-24 papa charlie posted would be your best bet off the shelf
McMaster Carr
3/8"-24 brass-tipped set screws, $8.38 pack of 10
https://www.mcmaster.com/catalog/126/3256/
3/8"-24 brass-tipped set screws, $8.38 pack of 10
https://www.mcmaster.com/catalog/126/3256/
Doug Beach
Silver $$ Contributor
Or just drill the bolt of your choice, and thread or glue a round head brass screw to the end, with the round head as your contact point.
B Nettesheim
Gold $$ Contributor
Yes
It’s real easy to put too much pressure on the barrel thus changing the shape of the barrel inside and out
carlsbad
Lions don't lose sleep over the opinions of sheep.
I like larger bolts. Aluminum threads will not hold up long term fine. I use my spiders much more than most of you here but yesterday I was thinking I may have to put thread inserts in my aluminum viper style truing fixture eventually. I used 1/2-13 set screws there. I make my own brass tipped set screws. I buy long standard set screws and bore them out for 1/4" diameter inserts. Yes they are hardened. the one's I've seen for sale are pretty poor.
In my outboard spider (non-chuck end of my spindle) I used 3/8"-24 in a stainless steel fixture and this is plenty of beef for that end.
On my barrel clambering spider which I made out of steel I only had room for 7/16-20 set screws but they seem to be fine.
So I use fine in steel and coarse in aluminum.
--Jerry
In my outboard spider (non-chuck end of my spindle) I used 3/8"-24 in a stainless steel fixture and this is plenty of beef for that end.
On my barrel clambering spider which I made out of steel I only had room for 7/16-20 set screws but they seem to be fine.
So I use fine in steel and coarse in aluminum.
--Jerry
I have built a lot of fixtures for my lathe in the past (non gun related). I prefer steel or stainless, depending on the application, but have used aluminum where the fixture become larger for ease of handling. In those cases where I am using aluminum, I make a point of using either never seize or something similar on the threads. This prevents the threads from galling. As a result, I have never had an issue with damaging or tearing out the threads, course or fine.
But I do agree with Carlsbad, fine threads in aluminum have the potential to fail much sooner than courser threads.
But I do agree with Carlsbad, fine threads in aluminum have the potential to fail much sooner than courser threads.
butchlambert
Site $$ Sponsor
Really! If I have a spider on each end with "copper" tips and a tenth Deltronic pin will still slide through it. It ain't bent or "squeezed".
AckleymanII
Gold $$ Contributor
M10-1.0 with brass tip is a fine thread, and would work very well.
A range rod or Grizzley rod with proper fitting reamer pilot will tell you immediately if the barrel is being squeezed too much. I check for this and have never experienced it, even on Model 7's in 308 Win muzzle.
A range rod or Grizzley rod with proper fitting reamer pilot will tell you immediately if the barrel is being squeezed too much. I check for this and have never experienced it, even on Model 7's in 308 Win muzzle.
How are you measuring this?
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