New to me Hartford Mill

[Susquatch]

Sorry @Susquatch, I got the milling direction completely a$$ backwards in my reply to your question 3) above.

To conventional mill, the cutter needs to be in the front of the workpiece (to cut the front step the key) when the table is moving right to left; and on the rear (to cut the rear step) when the table goes left to right.

Yes, you do want to feed into the cutting edge - that way the backlash is not a factor as it is taken out.

In machines with substantial backlash, the preference is not to climb mill (feeding in the same direction as the cutting edge is going) because if it grabs and takes up the backlash, the amount of material that needs to be removed at that instant may overpower the cutter and damage it off. Climb milling does tend to leave a better finish though.

No worries, that's exactly how I understood it. This cutter VS part/table stuff is all "relatively" confusing. (Pun intended.) As Einstein would have said, it's all relative..... LOL!

When I first started thinking about milling, I realized that all milling produces chips because the cutter grabs chunks with each tooth pass. In the absence of a chip breaker, lathes cut springs or strings because there is only one tooth that stays constantly engaged at the same depth from start of cut to finish. Spinning part VS spinning tool. In the same way, a lathe pushes almost all cuts which eliminates backlash during the cut.

But a mill is a different beast.

In my simple way of looking at it, I began by forgetting about all that left right stuff. Parts are either pushed into a cutter edge headed in the opposite direction, or yanked along by a cutter edge headed in the same direction. I figured that pushing eliminates the backlash the same way as it does on a lathe.

Hopefully this will all be intuitive for me some day soon.

I just assumed that it works like a lathe. You always want to fight the cutter in order to eliminate the backlash.

 

[YYCHM]

No worries, that's exactly how I understood it. This cutter VS part/table stuff is all "relatively" confusing. (Pun intended.) As Einstein would have said, it's all relative..... LOL!

When I first started thinking about milling, I realized that all milling produces chips because the cutter grabs chunks with each tooth pass. In the absence of a chip breaker, lathes cut springs or strings because there is only one tooth that stays constantly engaged at the same depth from start of cut to finish. Spinning part VS spinning tool. In the same way, a lathe pushes almost all cuts which eliminates backlash during the cut.

But a mill is a different beast.

In my simple way of looking at it, I began by forgetting about all that left right stuff. Parts are either pushed into a cutter edge headed in the opposite direction, or yanked along by a cutter edge headed in the same direction. I figured that pushing eliminates the backlash the same way as it does on a lathe.

Hopefully this will all be intuitive for me some day soon.

I just assumed that it works like a lathe. You always want to fight the cutter in order to eliminate the backlash.

That's a good description actually, I like it. I have a hard time grasping the concept as well, even with pictures. Now you have to wonder what up milling and down milling means when you're making a slot or when facing as now you have an advancing cutting edge and a retreating cutting edge no matter which way you feed the stock, or am I still not comprehending the concept?

 

[RobinHood]

Excellent analogy @Susquatch! I like your though process you went through comparing the lathe’s cutting action to a mill’s and seeing how they can be the same/different.

Now you have to wonder what up milling and down milling means when you're making a slot or when facing as now you have an advancing cutting edge and a retreating cutting edge no matter which way you feed the stock, or am I still not comprehending the concept?

That’s why it is preferred to cut slots undersized first and then do a step over to clean up the sides. Once the cutter is only cutting on one side wall, you just gave yourself the choice of feeding into the cutting edge (conventional) or feeding with it (climb). Since you have the option, even a less rigid mill can produce a good quality slot.

In other words, if you want a precise 1/2” slot, stay away from the 1/2” end mill - as tempting as it may seem to use one.

 

[YYCHM]

That’s why it is preferred to cut slots undersized first and then do a step over to clean up the sides. Once the cutter is only cutting on one side wall, you just gave yourself the choice of feeding into the cutting edge (conventional) or feeding with it (climb). Since you have the option, even a less rigid mill can produce a good quality slot.

In other words, if you want a precise 1/2” slot, stay away from the 1/2” end mill - as tempting as it may seem to use one.

But..... What's the right way to face or do the initial slot in the first place?

 

[PeterT]

RH beat me to it. Its generally always undesirable to mill a slot with the same width EM, at least if you are aiming for any degree of precision & finish. One edge will be climb milling & the other conventional. The slot will always be a tad wider than the EM diameter. Better to select an EM of say 60-70% of width if you want high removal rate. Then you can better control feed & speed during roughing, then climb mill on both faces of slot during finishing pass. The slot bottom can be finished at same depth since you have EM diameter overlap.

Looser machines aggravate climb milling but even solid, tight CNC's have to pay attention to tool deflection with high DOC or high tool stick-out. For hobby machines I like rougher EM's specifically for this reason. They do a better job removing bulk material vs conventional EM's with less stress on everything. Save the good cutters for smaller DOC & finishing. Notice in climb milling chip goes from thick to thin. Conventional goes from thin to thick.

 

[RobinHood]

Yes, do the center of the slot undersized initially, then you choose how you want to finish the sides in a second step.

Using the 1/2’ slot as an example again, you could use a 3/8” end mill (or a 7/16” one if you know how it behaves) to take out the majority of the material, then step over as required to get the walls 1/4” each side of center.

Or as Peter just posted, use two different end mills: one to rough & one to finish.

 

[Susquatch]

Now you have to wonder what up milling and down milling means when you're making a slot or when facing as now you have an advancing cutting edge and a retreating cutting edge no matter which way you feed the stock,

I have enough trouble just doing one face without adding that complexity......... It's a damn good question! In my minds eye, I see an Irish jig goin on on one side and a spastic hip-hop on the other..... I'll comment a bit more a bit further down.

In other words, if you want a precise 1/2” slot, stay away from the 1/2” end mill - as tempting as it may seem to use one.

Sounds like a great plan to me! Solves the dance card problem too! I'll be adding that one to my bag of tips.

Notice in climb milling chip goes from thick to thin. Conventional goes from thin to thick.

Ya, that's the cutting edge observation I made earlier about one of the differences between lathes and mills "one tooth that stays constantly engaged at the same depth from start of cut to finish."

But the drawing you used seems to introduce yet another phenomena - namely bending of the cutter body itself! The drawing does a crappy job of that, but the words in the subtitle are very informative (exact opposite of the old adage - one picture is worth a thousand words). This bending issue is one of the biggest issues with my mill/drill. I have an active imagination, I imagined it to be much worse than it probably really is. But I swear I could see it bending sometimes with my naked eye!

Now just insert that issue into the 1/2" slot @YYCHM asked about! My head hurts. Yet another reason to cut small and then finish afterward.

 

[historicalarms]

Hey Susq (and YYC for that matter), take one of your new 32" barrel blanks and finish it to an octagon barrel on a mill with a bed travel of 25 inches or so....by the time you have that baby down to a facsimile of a factory job you will be much more versed on the intricacies of both side cutting & top cutting with an endmill. By the time your done the 8 sides intricacys of feed direction will be forever embedded in your thought process for every other mill job you ever attempt.

You need the "shorter than work" bed travel so you can get the complete benefit from the job....multiple re-sets with the accompanying measurements & alignments( angles too).

 

[Susquatch]

Hey Susq (and YYC for that matter), take one of your new 32" barrel blanks and finish it to an octagon barrel on a mill with a bed travel of 25 inches or so....by the time you have that baby down to a facsimile of a factory job you will be much more versed on the intricacies of both side cutting & top cutting with an endmill. By the time your done the 8 sides intricacys of feed direction will be forever embedded in your thought process for every other mill job you ever attempt.

You need the "shorter than work" bed travel so you can get the complete benefit from the job....multiple re-sets with the accompanying measurements & alignments( angles too).

OK, so how about let's debate the accuracy and precision issues associated with the service of octogonal barrels first....... If we can agree on that, I might agree to discuss various alternative methodologies for cutting flat surfaces on the lathe instead of a mill. After all that, MAYBE I'll consider the milling issues........

If you agree to all that, then I plan to declare temporary (or permanent) insanity and claim I never suggested it in the first place......

On a serious note, are they really milled? I would have thought the old originals were either hammer forged or drilled from octogonal billet. Or is that just some modern trend I am not aware of......

Or are you just having fun....

 

[historicalarms]

OK, so how about let's debate the accuracy and precision issues associated with the service of octogonal barrels first....... If we can agree on that, I might agree to discuss various alternative methodologies for cutting flat surfaces on the lathe instead of a mill. After all that, MAYBE I'll consider the milling issues........

If you agree to all that, then I plan to declare temporary (or permanent) insanity and claim I never suggested it in the first place......

On a serious note, are they really milled? I would have thought the old originals were either hammer forged or drilled from octogonal billet. Or is that just some modern trend I am not aware of......

Or are you just having fun....

On the first question....99.9% of my shooting is done with cast bullets so the accuracy difference between round or octagon is so far out of the realm of worries that it is insignificant...I just do it to make 1870's-90's actions mimic buffalo rifles of old.

The "insanity thing....well, thats just a given.

Also never given it much thought on the old ones being hammer forged...Other than civil war cannon barrels, I have never read of any done in North America anyways.
Pretty sure they weren't drilled from octagonal stock, bores are way too uniform in centering from OD to be drilled...even modern deep hole drills wander off from center 99.9% of the time.

No, I was very serious in suggesting the operation. The one i did, I clamped as level and straight with the table travel as I could and had at'er. first cut was a top flat cut with an endmill, second two cuts were side cuts with same endmill, one on each side....this set the & sides perfectly perpendicular to each other and not bad for re-setting....there was a flat side to set on the blocks for every cut.

Edited to add; Now, thinking back on what I read on the hammer forged cannon barrels, it was an experimental project carried out by the Union army war dept. and was cancelled before many were made because they deemed it too expensive an operation ( the equipment required and the steel was much more money than cast iron)so they want back to casting iron tubes altho they did us a steel bar to create the bore in the casting and pulled it out (must have been quite an operation in itself for the time).

 

[Susquatch]

On the first question....99.9% of my shooting is done with cast bullets so the accuracy difference between round or octagon is so far out of the realm of worries that it is insignificant...I just do it to make 1870's-90's actions mimic buffalo rifles of old.

The "insanity thing....well, thats just a given.

Also never given it much thought on the old ones being hammer forged...Other than civil war cannon barrels, I have never read of any done in North America anyways.
Pretty sure they weren't drilled from octagonal stock, bores are way too uniform in centering from OD to be drilled...even modern deep hole drills wander off from center 99.9% of the time.

No, I was very serious in suggesting the operation. The one i did, I clamped as level and straight with the table travel as I could and had at'er. first cut was a top flat cut with an endmill, second two cuts were side cuts with same endmill, one on each side....this set the & sides perfectly perpendicular to each other and not bad for re-setting....there was a flat side to set on the blocks for every cut.

Edited to add; Now, thinking back on what I read on the hammer forged cannon barrels, it was an experimental project carried out by the Union army war dept. and was cancelled before many were made because they deemed it too expensive an operation ( the equipment required and the steel was much more money than cast iron)so they want back to casting iron tubes altho they did us a steel bar to create the bore in the casting and pulled it out (must have been quite an operation in itself for the time).

I see.

Well, I'm not a fan of octogonal barrels. I do have a muzzle loader but it's a modern one with a round barrel and I only bought it because we have a muzzle loader only deer season here. It mostly just gets older the rest of the year.

My match grade barrels are much to precious to do any milling on.

But I like the idea of the learning experience. Perhaps after I choose a mill and finish fixing it up, I'll try the process out on a plain chunk of steel just for that reason.

 

[Susquatch]

Big day today. My first parts order arrived from H&W. I am hoping it includes everything I need to get the Hartford going. Primarily the bull gear bearings, grease, and miscellaneous other small parts. But both mills were missing the quill wheel so I bought one wheel to go on whichever machine I end up keeping. I've already extracted the broken stud on the BP to facilitate that.

Now the pressure is on to complete the motor adapter, the pulley modifications, and the shaft key. Hopefully I can do all that this week. If not, then next week for sure.

I also bought a bunch of machine screws to replace most of the crappy flat slotted and Philips screws in the Hartford while it's apart. I'm not very fond of either philips or slotted. Besides, high quality allen head machine screws are really quite inexpensive for what you get.

 

[Susquatch]

Another snag. As I reassembled the back gear, I discovered something I missed during the disassembly. Members may recall the problems I had getting the pin out for the gear shift fork. The main body of the head has a stepped hole in it so the pin cannot be punched out as described in the manual. It must be pressed out from the bottom up.

Well, in the process of putting it all back together, I discovered that the pin is also staked. There are corresponding grooves in the housing where the stake marks fit..... So, looks like the pin I ordered will be surplus. I will need to use the old pin and align it soo the stake marks and grooves line up. Yes, I could just make new grooves by hammering it in, but that would just snowplow the problem by moving more metal around. So I'll put it back where it wants to be.

Edit - turns out that those stake grooves are regular and don't match the stakes. Near as I can figure, the stakes and the grooves were deliberately done to stop the pin from coming out as well as turning. This seems really odd to me. The pin is only a guide for the forks. Nothing turns on the pin so nothing should cause it to spin. So why all the trouble to make that pin work and act like that? What am I missing here?

 

[Susquatch]

Hit another snag. The replacement cog belt for the back gear is a different tooth spacing than the original. That's a pretty significant departure from the Bridgeport standard.

But worst of all is that this means the big pulley is also wrong. Except for the broken piece of one tooth, there isn't much wrong with the old one. So I'll just repair it with epoxy and reuse it. The pulley was expensive so I'll have to return it.

Unless someone wants it?

 

[Brent H]

@Susquatch - PM @architect - he may be able to use it

 

[Susquatch]

@Susquatch - PM @architect - he may be able to use it

Done.

 

[Susquatch]

Pulley and cover plates arrived today. Yup, wrong size.

Gunna return it and then repair and use the old one.

Also almost finished the motor adapter plate today. Ended up deciding to gouge/cut the center section out. Too much work and too many chips to cut it away. This way I have a 1/2 x 5 inch disk of plate steel I can use for other jobs. Gouge cutting the center out of that plate was no piece of cake! Couldn't use regular cutoff blades. Even at 5 inches, the curvature of the cut was more than it could handle. Had to grind a special tool to get the depth and handle the inside/outside radius.

Basically, I don't like parting and that's exactly what this felt like. Anyway, that "part" is done now. Tomorrow, I'll make sure it fits the motor, flip it, and then clean up the backside to get it ready to paint.

Originally, I had thought I might have to mill down mickey's ears a bit, but that has turned out not to be the case. The quick clamp bolts appear to be designed to handle a plate thickness from about 1/4" to 3/4" or so.

 

[John Conroy]

RH beat me to it. Its generally always undesirable to mill a slot with the same width EM, at least if you are aiming for any degree of precision & finish. One edge will be climb milling & the other conventional. The slot will always be a tad wider than the EM diameter. Better to select an EM of say 60-70% of width if you want high removal rate. Then you can better control feed & speed during roughing, then climb mill on both faces of slot during finishing pass. The slot bottom can be finished at same depth since you have EM diameter overlap.

Looser machines aggravate climb milling but even solid, tight CNC's have to pay attention to tool deflection with high DOC or high tool stick-out. For hobby machines I like rougher EM's specifically for this reason. They do a better job removing bulk material vs conventional EM's with less stress on everything. Save the good cutters for smaller DOC & finishing. Notice in climb milling chip goes from thick to thin. Conventional goes from thin to thick.

View attachment 16273

I just watched a fun video from Fireball Tool showing his giant Cincinnati mill with some nice slo-mo footage and great explanation of climb vs conventional milling.

 

[Susquatch]

I just watched a fun video from Fireball Tool showing his giant Cincinnati mill with some nice slo-mo footage and great explanation of climb vs conventional milling.

Holy COW! That is some tool! I like his explanation too. Helps cement an understanding of the principles. But I prefer my more simplistic version for most purposes "simply" because I have a half a** chance of remembering it!

 

[Susquatch]

I chatted with H&W today.

Apparently the belt and pulley are linked to HP. My step pulley is a 2HP. They said they can exchange my parts for the right ones if they can find them. TBD.

More waiting....... (insert huge sigh here).