Good day all. 

I'm looking at building the guided helve power hammer. (rusty/Krusty??) 

For the ram and guide I was looking at uhmw for bearing surface and thought what about using round tube uhmw for the guide and a length of round bar 4140 for the ram.?

Seems too easy am I missing something? 

The problem with round guides is when they wear you can't really adjust them for a tighter fit like you can flat ones. Look at machinery like lathes, and milling machines. They use tapered gibs so that the slop can be adjusted out. 

I see. How long could it take to get sloppy? 

The plastic tube isn't terribly expensive and the way I'm envisioning the way to mount it should be able to Change it out in minutes. 

Anyone one else able to share there wear rates with uhmw guides.? 

UHMW tube is NEVER straight nor is it tight enough tolerance to be used except as loose-fit.  Wall thickness tolerance of UHMW tube is always positive and quite substantial.  Also, the expansion rate is so high that you can have weird effects with temperature changes. 

I'd avoid the tube for this and go with sheet goods.  It's also worth it to go very thick with UHMW material--even 1/2" thick can go noodley on you when it gets warm and the material cold flows.  Thicker is definitely worth the expense.  Be sure and avoid re-grind material also as some suppliers toss out this option as cheaper (I've seen regrind with metal shards and voids).  Specify "virgin" material only.  Black (UV stabilized) if it will see either sunlight or fluorescents (or welding arcs) of any non-incedental duration.

I use about $ 50,000 in UHMW material a year so am fairly experienced with it's foibles.

I just checked a piece of UHMW tube in the shop to give some example numbers:  Roundness varies by .013 which is a LOT and the bore is .045 undersized, OD .04 oversized.  Bow from the factory in a 4 foot length was 1" but one could probably deal with that.  It would definitely need to be machined to size to use as a guide of any kind (1.5" I.D, 2" O.D. was the specified size of the tube)

wow that is alot of variance. i guess i will stick with the sheets. thanks. is uhmw still the better option. how much work are you doing between changing out the guide surfaces?

Good Morning,

Maybe this is the reason Skate-Board Wheels are used for the guides.

Neil

Does any one here have any pictures of a guide using skateboard wheels? 

Seems more durable 

for my ram guides I'm in train to build I would use this kind of rollers - they are on ball-bearings and are V-grooved. you can use 2 pairs to guide a square rod (used on the corners), for example, and are easier to use in the build than the skateboard rollers. and in my area are 2 times cheaper than the skateboard's ones.

Anyone have  a recommendation for how long the guide should be using using 2 sets of bearing on each side. 

I have zero experience so I can only really guess. I am thinking about 10 inches but is this overkill. 

If I am thinking about this right 

10" Guide + 7" travel + 2ish" whip? + 6" of adjustable height. =a minimum of 25" ram is 63lbs using 3" bar.   plus top die. 

Does this sound right? 

Is 3 inch a good ram size? 

I don't need that heavy of a hammer. But thought 2 inch ram would be too weak. 

Your question is to vague in my humble opinion.

a 3 inch square ram has little space for mounting the top die. How do you plan to mount it, V groove and wedge? bolts and a mounting plate?

Make a drawing of the ram assembly and give some numbers for bpm. Without details no one should judge if the guide is long enough.

It depends on lateral forces caused by the swing arm, what tooling you want to use and the type of bearing surface.

I would not recommend rollers. you need a tight fit to avoid impacts on the bearing. A tight fit leads to a constant motion which causes in my mind spots in the bearing to be worn out more than others.

Read, compare, calculate  and sketch. And state clearly  what you want  to do with your hammer, because there are many hammers out there and no other will be like yours 

Actually 10" is adequate but forget the wheels use plates instead. 

Agreed, keep it simple. Just use flat pieces as your wear guides. 

Gotcha. Hoping to start scrap shopping soon. Only issue is the closest yard worth going to  is about 5 hours away. 

Any Canadians on here that knows of a good place to buy uhmw.? 

If you are going scrapping keep your eyes open for strips of brass or bronze, will work as well or better than PE in a home built power hammer if you luck onto the right stuff.  

Nomenclature note:  UHMW stands for Ultra High Molecular Weight.  Correct abbreviation should be UHMWPE the PE part is an acronym for polyethylene.  Most folks reading this should know that but we get beginners all the time...

Merry Christmas!!

Any Canadians on here that knows of a good place to buy ????  Lots of special Treasures in Ottawa, on the Hill!!

The best way to build a Hammer, is look in your own yard to see what you have in inventory. Most scrap metal dealers won't let you through their yard. Talk to your local auto Mechanic's and see what is in his/their scrap pile. Don't start with "I have to have this", start with "what can I use that is locally available, to get the job done". Paint comes last!! Donuts help with access to inventory of used parts. Look through your local Auto Wreckers for ideas.

Neil

The yard I mention is one I have full access to the yard. I'll have to take  a drive to Ottawa.  that's much closer. 

Thanks for the input so far I'm sure I'll have more questions. 

Luckily I have my dad's help he collects lots of treasure and is a skilled fabricator. 

 

And merry Christmas everyone