Causes and in fact the space receive their funds on a per-month basis disbursed based on membership dues. The intent and general approach to this is that budgets have an expiry on them, either be that a time period (monthly) or upon exhaustion of the budget.
An unlimited discretionary budget with a cap on per-purchase does certainly seem attractive but would go against the whole monthly nature of our standard discretionary budgets - even the executive discretionary budget is monthly. On top of that, discretionary budgets in that style would go against the ethos of being a community organisation where every member can have equal input in our decisions. Additionally, It.would not be financially prudent to allow a cause leader to have this level of budget as it would allow for being able to spend a cause’s entire accrued funds in short order.
Procedurally, in order to approve any kind of cause related budget at this point in time it would need to be done by implementing a Cause Operating Policy at a cause meeting (See https://hsbne.org/admin/causes.html). Currently the Metal Shop cause does not have a cause operating policy that I can find, though there was discussion around implementing one back in 2018. The template is online at https://docs.google.com/document/d/1OzwjLIBdxa1CPozrRPLr6AJX7AvkqW8Eo7ahWjPWV84/edit?usp=sharing
From your pain points you’ve listed above though, I have a suggestion. In the Electronics cause we have a list of consumables and a consumable budget such that any member can purchase consumables in that list and expect to be reimbursed (Provided we’re almost out of them and they’ve spoken to the cause leader). A lot of what you’ve listed above is consumables (first two items) so this would fit the bill.
$100 a month is tight for metal shop consumables and the value you’ve set for $200 would be perfectly reasonable as a monthly budget for consumables, I’d encourage you to implement the same approach with the list of approved consumables as it will make your life easier.
With regards to materials, whilst you could have a monthly budget for this it would be in my opinion more sustainable/less work to have a bulk budget every few months to buy a bunch of common stock and stock take every couple of months to bring stock back up to acceptable levels. This way the purchase of stock goes past the membership each time and is fully equitable.